VOLUME 7 No. 3 / AUGUST, 1973 / PRICE $1.00 G.P.O. Melbourne for posting as a periodical (Category B)

Gas Cleaning System

A New Approach to Dust and Fume Collection

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UNITED DEVELOPMENT CORPORATION PTY. LTD.

Cover ii Clean Air / August, 1973

Vo l . 7 / No. 3 August, 1973

GUEST EDITORIAL Dr. Moss Cass, M in is te r f o r Conservat ion and Env i ronment

TECHNICAL PAPERS

Measurement of Oxides of Ni t rogen in M o t o r Vehicle Exhaust, R. W. Bilger

Fabric Dust Co l lec tors , S. Stanley

SI Units and the A i r Po l lu t ion Engineer, W. Strauss

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The O l d , The New and The Future in A i r Pol lu t ion Ins t ruments , Andrew E. O'Keeffe 50

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FEATURES

Air Pollution Research in Australia and New Zealand

New Zealand Branch News

A Conservationist Book Club in Australia

Air Pollution Technology Course

In The Federal Sphere

Ambient Air Monitoring Programme

Forthcoming Conferences

Book Reviews

JOURNAL OF THE CLEAN AIR SOCIETY OF AUSTRALIA AND NEW ZEALAND President: J.G. Schroder Federal Secretary: Dr. J. Harry, P.C. Box 163 Lidcombe, N.S.W. 2141

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EDITOR W. Strauss ASSISTANT EDITOR S.J. Mainwaring EDITORIAL BOARD W.H. Cock H. Hartmann L. Clunn N. Hawthorn EDITORIAL OFFICE Department of Industrial Science University of Melbourne Parkville, Vic, 3052, Australia

ADVERTISING H.E. Pett &. Co. 31-37 Russell Street, Abbotsford 3067

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Subscriptions and subscription enquiries should be directed to the Circulation Manager, Mr. L. Clunn, 20 Lynette Avenue, Beaumaris, Vic. 3193, Australia.

'Clean Air' is listed in Current Contents and Environmental Periodicals.

Clean A i r / August , 1973 A1

A2 Clean Air / August, 1973

The clean air crisis:

If current clean-air legislation is confronting you with future problems. Lucas wood-waste furnaces offer the immediate answer.

Lucas furnaces provide complete combustion of chips, shavings, saw-dust and sander dust, entirely eliminate emissions of smoke,

odour and ash, do not require smoke-arrestors and greatly reduce the need for boiler-cleaning.

In every way, and by wide margins, Lucas wood-waste furnaces meet every require­ment of the clean-air regulations. Operation is fully-automatic with no need for operator-control so you make big savings on labour costs. Maintenance costs are low with monolithic, high-density, super-duty refractories to save you the cost of periodic re-bricking. Wood waste is fed pneumatically into Lucas furnaces so complex materials-handling equipment is not required. The only visible emission from the stack of a Lucas wood-waste furnace is a shimmer of heat. What more could you ask?

LUCAS RECYCLERS OF AUSTRALASIA LTD. 608 St. Kilda Road, Melbourne. 3004 Telephone: 51 5381

A division of Unochrome Australia Ltd.

UNO 49

Clean Air / August, 1973 A3

For economical dust and fume collection Mikro-Pulsaire Filter Collectors USED throughout Industry — Throughout the World! Proved in more than 20,000 world-wide installations, the Mikro-Pulsaire is performing a variety of duties . . . providing efficient recovery of high-value dusts . . . supplying effective dust control . . . contributing to the stepped-up fight against air pollution.

DUCON Temperature, corrosion and abrasion make it tough on dust control equipment in many of today's industrial pro­cesses, such as pyro-pro-cessing, catalyst recovery, black liquor recovery, calcining and pelletizing operations. The dust produced in these operations is hot, abrasive and often highly corrosive. An ordinary dust collector would deteriorate rapidly, re­sulting in costly shut­down of the operation and replacement of the equipment. In such applications, ex­perience really pays off. Ducon can offer 35 years of experience in dust control and extensive knowledge of severe service applications.

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HEAD OFFICE

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A4 Clean Air / August, 1973

LET's CLEAR THE AIR...

Ceilcote scrubbers settle pollution problems With pollution control regulations becoming more and more stringent, it will pay you to investigate the overall long-term advantages of Ceilcote wet packed scrubbers. Ceilcote has a scrubber to handle your noxious gases, corrosive mists, and solid particulates. Ceilcote manufactures corrosion-resistant air pollution control equipment from fibreglass reinforced plastic or lined steel. Wet scrubbers are our specialty. We design, engineer, and build them. For example: • Cross-flow Packed Scrubbers — Capacity 2,100 — 50,000 cfm. • Countercurrent-flow Scrubbers — Capacity 330 — 47,500 cfm. • Wet Cyclone Scrubbers — Capacity 3000 — 50,000 cfm. • Vertical Air Washers — Capacity 2900 — 67,000 cfm. And if these types are not suitable for your needs, we can build a scrubber to your specification. Unique Tellerette packing — exclusive to Ceilcote — is used in many of our scrubbers. The advantages are tremendous. Please write for fully descriptive literature.

Ceilcote Designers, Manufacturers and Installers of Corrosion Resistant Materials, Process Equipment, and Air Pollution Control Systems

Cellcote Pty. Ltd. , P. O. Box 563, Devonport, Tasmania 7310. Telephone: 27 8461 (Std. prefix: 004) Telex: 58510 Sydney 439 7760. Melbourne 81 3047. Adelaide 84 173. Perth 24 6044. Brisbane 5 3331.

Clean A i r / August , 1973 A5

CEILCOTE SCRUBBER AT GEELONG, VIC.

A typical Installation of a Ceilcote Duracor FRP scrubber at the Phosphate Co-operative at Geelong, Vic. This Tellerette filled, cross-flow scrubber weighs 12,800 lbs. and was designed by Ceilcote to treat 32,000 cfm. of Dens gas formed during

superphosphate produc­tion at 130°F.

NCAA 100 Ozone Monitor

The Norian NCM 100 Ozone Monitor measures the concentration of ozone in ambient air by photomet­rically monitoring the chemiluminescence resulting from the reaction of ethylene gas with ozone. The NCM 100 has built-in calibration and thermo-electric stabilisation for wide range ambient operations. The Monitor is capable of measuring ozone in the pre­sence of NO2, SO2, Cl2, and other substances which have traditionally interferred with the Potassium Iodide reaction.

The instrument is capable of accurate measurements in quantities as low as 0.1 parts per hundred million (pphm).

The NCM 100 incorporates original engineering by Messrs. L. M. Ferrari and E. Brown of the New South Wales Department of Health, Division of Occupational Health and Pollution Control, Australia, and is manufactured under licence from that Department.

FEATURES:

• Chemiluminescent Reaction of Ozone and Ethylene.

• Ozone Response Instantaneous. • No interferences from gases such as SO2, NO2 ,

CI2 , CO2, etc. • 4 Ranges covering 0-1,000 pphm. • Ranges 0-250, 0-50 for Atmospheric Monitoring.

• Direct Digital Readout. • BCD Output for Data Processing. • Peripherals including external recorder, printer, computer and

telemetry facilities.

We also invite your enquiry for

NCM 200 Chemiluminescent oxides of nitrogen analyser for measurement of stack and exhaust emissions, 0-20000 ppm.

NCM 300 Chemiluminescent oxides of nitrogen for atmospheric measure­ment, 0-100 ppm.

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A6 Clean Air / August, 1973

GUEST EDITORIAL

Dr. AAoss Cass, Minister for Environment and Conservation

One of the most important changes that occurred on December 2, was the election of a government that was prepared to act on environmental matters. It was realized that the do-nothing attitude of the previous Lib­eral Government had alienated a large number of middle class people who care greatly about conservation and are concerned with the deteriorating environment of Australian cities. Many new Labor Members of Parlia­ment from the outer suburban areas consider they owe their election to the fact that the Labor Party made more detailed and radical commitments on conservation than the Liberals.

I mention this in introduction to indicate that the Whitlam government feels is has the mandate to make radical decisions on environmental policy ranging from the possibility of saving Lake Pedder to stringent pro­visions for the maintenance of clean air. Like most environmental prob­lems, clean air is peculiarly susceptible to the perennial wrangle between State and Federal responsibilities. It is a fact that the greatest burdens in both monitoring and reducing pollut­ant emissions in Sydney and Mel­bourne are being carried out by State Government departments. However, while State bodies are doing their very best in this area, there is no doubt in my mind that air pollution is a national problem. This is the way it was perceived by the Senate Select Committee on Air Pollution. National, both because of its urgency, and be­cause of the Government's mandate

New Zealand Branch News

The Fourth Annual General Meeting of the New Zealand Branch was held in Auckland on 28th March. The fol­lowing were elected:

Mr. J. E. Fitzgerald (Branch President), Dr. J. Rogers (Vice-Pre­sident), Mr. A. W. Skam (Secretary-Treasurer), and as Committee Mem­bers. Mr. L. N. Larsen, Mr. N. Lory. Mr. N. G. Thom, Mr. R. T. Douglas, Mr. J. A. Bryan, Mr. D. J. Higgins, Mr. F. Robson, Mr. E. L. G. Clist and Dr. J. de Lisle.

Following the Annual General Meeting, a lecture on the "New Zealand Clean Air Act, 1972" was given by Mr. R. T. Douglas, the Chief Chemical Inspector of the Department of Health, and Mr. N. G. Thom, the Regional Chemical Inspector, Auck­land. The speakers dealt with the history and philosophy of the act, and in particular with the definition of

on environmental issues. In its wider sense, the air in Aust­

ralian cities has become a classic example of "The Tragedy of the Com­mons." Because the price of air is zero, and because it has no monetary value, it has become a dumping ground — a cesspool.

It will be quite obvious to readers of this journal, which has an inter­national reputation, that the problem of air pollution is going to get worse before it gets better. One indicator of this is the number of cars — the mobile sources — registered each week in Melbourne and Sydney.

Apart from the mobile sources, stationary sources such as, for ex­ample, coal burning power stations, are vitally important in the overall pollution pattern, and like other en­vironmental problems, this becomes a problem in planning. The Common­wealth Department of Urban and Regional Development is aware of this, although its constitutional pow­ers are limited; to reduce traffic and pollutant loadings, it has already secured the location of a large block of Australian government offices at Parramatta instead of the inner Syd­ney area, which is under stress.

One of the first tasks in determin­ing the extent of air pollution is to establish some sort of national air monitoring system. This was proposed at the 4th meeting of the Australian Environment Council which met in Melbourne on July 5. The N.S.W. Min­ister for Environmental Control, Mr. Beale, provided information on a de­tailed feasibility study initiated by N.S.W. for a monitoring network for air, water and noise in the Sydney regional area which was conceived as the first module of a national net­work. He also proposed a motion for

an "air pollutant," and the obligations of the "occupiers of premises." Over 100 people attended, including 27 members of the Society, and repre­sentatives of local authorities, the consulting engineers and the N.Z. Institution of Engineers.

A Conservationist Book Club in Australia?

The publisher for Thomas Nelson (Australia) Ltd., Miss Anne Godden, has indicated that her organization is considering starting a "conserv­ationist book club" in Australia, along similar lines to the Sierra Club Books of America. If there were 2000 mem­bers, books could be supplied at $4.65 each, and with 5000 members the price could be as low as $3.55. The books would have board covers, and colour plates. Society members and others are invited to write to the publisher, at 597 Little Collins Street, Melbourne,

the establishment of such a national pollution monitoring network, of which air monitoring would be a major element. This resolution was passed by the Council and the feasi­bility study is expected to be com­pleted by September next. The Aust­ralian Environment Council also passed a resolution recommending that "The Australian Federal and State Governments increase the allo­cation of resources for monitoring purposes."

It is not possible for me at this stage to say by how much this allo­cation will be increased, as other government departments are tackling the problem. My department, in asso­ciation with the department of Trans­port, is working on more stringent design rules for motor car emissions. The National Health and Medical Research Council has also been active in this general area, and at its 76th session, l0th-l l th May, 1973, "en­dorsed the national air quality mon­itoring programme and national motor vehicle testing programme," and passed its documents on to the monitoring sub-committee of the Australian Environment Council.

While there is no shortage of con­cern by some elements of the public, and more information and technical expertise is becoming available, only a wide general increase in public con­cern will force more government action, such as the provision of Fed­eral funds. I therefore consider it a matter of basic importance that public pressures force both State and Federal governments to act with even more despatch. It is in this area of raising public consciousness about the problems of air pollution that this journal, Clean Air, is playing a vitally important role.

3000, to indicate their interest, so that an estimate can be made to see whether sufficient subscribers would be forthcoming

Air Pollution Technology Course

The Victorian Branch of the Society, in conjunction with the Vic­torian Chamber of Manufacturers will conduct a course in "Air Pollution Technology" on Tuesday evenings. 6.30-8.30 p.m., from 18th September to 23rd October, at the Victorian Cham­ber, 370 St. Kilda Board.

Subjects to be studied are: Meteor­ology and dispersion of air pollutants, Monitoring, Fuels and Combustion, Control Systems and Equipment, Odour Control, Automotive Pollution, and Legislation. Further details can be obtained ' from Mr. W. H. Cock (Phone 435 7492), Mr. G. K. Ferris (877 2044) or Mr. D. A. B. Phillips (699 1411).

Clean Air / August, 1973 45

R. W. Bilger MEASUREMENT OF OXIDES OF NITROGEN IN MOTOR VEHICLE EXHAUST

The literature on the measurement of oxides of nitrogen in motor vehicle exhaust is reviewed with particular emphasis being placed on methods suitable for employment as standards for regulatory purposes. Attention is given to sampling techniques and the problems associated with the total bag sample procedure. Recommendations are made for further investigation of the range and extent of NO x — hydrocarbon reactions in total sample bags and the use of continuous sampling as an alternate procedure for use with total bag sample procedures for measuring CO and hydrocarbons.

Dr. Bilger is a Senior Lecturer in the Department of Mechanical Engineering, University of Sydney, N.S.W. 2006

Introduction: Oxides of nitrogen (NOx) are present in gasoline engine exhaust gases in concentrations rang­ing from 100 to 3000 ppm. Accurate, or at least consistent, measurement of the mass of NOx emitted from gas-oline-engined vehicles is required if standards and regulations limiting the emission of this pollutant are to be implemented.

The problems associated with the measurement of NOx from gasoline engine exhaust can be broadly divided into:

(i) obtaining a correct sample; (ii) correctly analysing the sample. Methods of analysing NOx in

samples have been recently but briefly reviewed by McFarland and Benton (1)

and earlier but more comprehensively in a Shell publication by Blackmore and Crawford (2). It is not proposed to repeat such a review here. Suffice it to say that since the Shell review the early promise of the ozone-chemi-luminescent method appears to have been fulfilled and this instrument is now almost universally used by the motor vehicle industry and regulatory authorities for NOx analysis. (Some remarks on nitric oxide chemilumine-scent analysers and thermal convert­ers will be found later in the paper.

Problems associated with obtaining a correct sample range from selections of the correct "driving cycle" to limiting losses in the exhaust hand­ling system and collection bag, if used. The first of these involves such questions as: "Is the Economic Com­mission for Europe Regulation 15 or the 1973 U.S. Federal driving cycle procedure more representative of emission conditions?", and is beyond the scope of this review. The main methods of sample collection are the continuous sampling (CS), propor­tional sampling PS), variable dilution or constant volume sampling (CVS) and total bag sampling (MB) tech­niques. Of these only the proportional sampling (PS) technique (3) has not been used in regulatory standards, presumably due to the resistance it gives at the air inlet to the engine and its general complexicity.

Various combinations of sampling technique and analytical method have

been used (4)-(9). Only three proced­ures have been actually specified as part of a legally required standard. They are —

(i) California 1971 — 7-mode cycle with continuous sampling (CS) and non-dispersive infrared (NDIR) ana­lysis of NO.

(ii) California 1972 — As for 1971 except that a hot 7-mode cycle may be carried out at the end of a U.S. Federal CVS procedure and that chemiluminescent analysers may be used.

(iii) U.S. Federal 1973-76 — Mul-timode cold start or cold plus hot start driving cycles, constant volume sampling (CVS) with diluted sample accumulated in bag and analysed by chemiluminescent NOx analyser.

The current Australian standard embodied in Australian Design Rule No. 27A (ADR 27A) makes no mention of NO*. It is based on the European standard (ECE 15) which also has no provision for measurement of NOx. There is increasing concern about these emissions from motor vehicles particularly as the common methods of controlling hydrocarbon (HC) and carbon monoxide (CO) emissions re­sult in a substantial increase in NOx emissions. The European Group of Rapporteurs on Air Pollution (GRPA) is currently discussing methods of measurement of NOx to be used with the ECE 15 total bag sampling (MB) procedure. Recently it has been an­nounced that Australia will be adopt­ing the 1973 U.S. Federal procedure and standards for implementation from July 1976. There will be a period of two and a half years between the implementation of ADR 27A and these new standards (ADR 27B) during which some million and a quarter vehicles will be produced with no NOx controls. There is a need for a proced­ure capable of being used with the ADR 27A test so that the NO* emission rates of these vehicles can be monitored.

In the following sections the various problems involved with ob­taining a correct sample and analy­sing it correctly are discussed. A secondary aim of this review is to recommend procedures to

46 Clean Air / August, 1973

be developed for use with the total bag sampling (MB) procedure as used by ECE 15 and ADR 27A.

Fundamental Considerations

The NOx in the exhaust at tail pipe exit is almost entirely nitric oxide (nitrogen monoxide) NO. At room temperature this nitric oxide reacts with oxygen present in the exhaust (approx. 1%) or diluent (up to 21%) to form nitrogen dioxide N02. The re­action is apparently termolecular in the absence of radiation and proceeds:

Stephens and Schuck (10) give k = 4.5 X 10-12 pphm-2 hr-1 at 298°K. This means that for raw exhaust with 1000 ppm NO and 1% O2 at room temperature 15% will be converted to NO2 in 12 min. With exhaust diluted about 10 times so that there is 100 ppm of NO and 19% 02, 25% of the NO will be converted to N02 in 12 min.

Nitric oxide is essentially insoluble. Engine exhaust gas contains approx­imately 12% water vapour and this will condense on cooling by heat ex­traction. No data appears to be avail­able on dew point elevation by NO2. Nitric oxide is generally unreactive (except with oxygen and unsaturated hydrocarbons) while nitrogen dioxide is quite strongly reactive with a wide range of substances. Donnelly ( 1 1 ) re­commends the use of teflon tubing with stainless steel fittings where NO2 is present.

The dark reactions of nitric oxide and nitrogen dioxides with unsatur­ated hydrocarbons have been studied by Altshuller and Cohen (12). There

appears to be insufficient evidence to make a direct assessment of the rate of depletion of nitrogen oxides in raw and diluted bag samples but both Altshuller and Cohen (12) and Hum et al. (13) consider that the reactions will present serious analytical prob­lems in raw exhaust samples. The reactions are considerably slowed by dilution. Figure 1 shows data of Smith et al. (3) for raw exhaust and exhaust diluted in various ratios by dry nitro­gen. The raw exhaust in this case was dehydrated immediately after the sample point so that there can be no question of N02 loss to condensate. The disappearance of NOx is accom­panied by loss of hydrocarbons when analysed by FID (flame ionization detector) there being no apparent loss with NDIR analysis.

The use of plastic bags for collec­tion and storage of gas samples has been reviewed by Schuetted (14). Mylar and Tedlar bags have been found to be essentially inert to NOx and Tedlar is widely used for exhaust storage in the United States. Films of condensed water vapour and hydrocarbons, and hydrocarbon reaction products can accumulate on the bag surface when raw exhaust samples are used and may interact with the gas phase NO,.

Continuous Sampling (CS) Tech­nique: In this technique a continuous, constant flow rate, sample is extracted from the exhaust and monitored by rapid response instruments. The tech­nique is widely used by the motor in­dustry for engine component and control system development. It is also used in the California test procedure where NDIR analysers for NO were initially specified. Since there is in­sufficient time for NO2 to be formed it is not analysed for and the sample

may be dried by a dry ice/acetone trap prior to entry to the instrument. Since NDIR instruments suffer con­siderable interference from water vapour the sample must be dried very well. With chemiluminescent analy­sers H2O interference is negligible and recent continuous sampling practice tends to use heated sample lines and heated instruments to avoid HaO con­densation (15).

The main disadvantage of this system is that the time dependant concentration output obtained must be suitably weighted so that a true mass emission result is approached. For regulatory purposes this weight­ing can be somewhat arbitrary if only a consistent standard is required.

Constant Volume Sampling (CVS) Technique: The variable dilution or constant volume sampling technique mixes the whole of the exhaust stream with a considerable excess (minimum of eight times) of pre-purifled, filtered air and after mixing it is cooled and pumped at constant volume flow rate. A small but constant flow rate sample is extracted before the pump and accumulated in a plastic bag. This procedure has been described by Broer-ing et al.(4), Mick and Clark (5), and Booy (6). It purports to give a true mass emission result and has been adopted by the U.S. Federal govern­ment as the standard test procedure from 1972. Nitrogen oxides analysis is implemented for 1973 model year cars and is effected by means of a chemi­luminescent analyser with the use of a NO2 to NO converter so that total NOx is measured. Problems with water vapour condensation are precluded by dilution so that the mixture always remains above the dew point. Reac­tions of NOx with hydrocarbons in the

Clean Air / August, 1973 47

bag are kept to negligible rates by the large dilution used. The measurement technique is considered to give accu­rate results and Donnelly (11) estimates that the results of the California Air Resources Board Laboratory correlate to within about 2% with results of the General Motors Corp. laboratory.

Total Bag Sampling (MB) Tech­nique: In this technique the total undiluted exhaust emission is pumped into a plastic bag after cooling the gases in a heat exchanger and remov­ing the condensate. Although this technique forms part of European (ECE 15), Australian (ADR 27A) and Japanese standards for measuring CO and hydrocarbons it has never been used to set a standard for control of NOx. General experience (e.g. Yana-gihara (17) ) has been that NOx losses occur in the bag in an inconsistent manner. The results shown in Pig. 2 are due to Iverach (18) and are typical. These results are for samples collected according to the ADR 27A procedure which is very similar to the ECE 15 procedure. The equipment used in­corporated an over-sized heat ex­changer which cooled the gases very effectively and no condensation was apparent on the walls of the sample bags. NOx analysis was by means of a Thermo Electron Model 10A chemi­luminescent analyser with thermal converter.

An attempt to qualify the losses has been made by various workers reporting (19) to the ECE Group of Rapporteurs on Air Pollution. From the information available it appears that a test vehicle was motored at steady conditions on the dynamometer and its exhaust collected in the bag for 20 min. The NOx content of the bag was then measured and compared with the NOx in the exhaust as con­tinuously sampled during filling. Average losses reported ranged from a low of 2% by the German rapport­eur to a high of 20% by the U.K. rapporteur. The effect of vapour con­densation was evidently questioned. At a later meeting the draft standard was amended to require cooling of the gases to below 17°C. The sample bags are required to be flushed with dry air before each test. An ice trap at inlet to the analyser is also required, an amendment which is difficult to understand. It should be pointed out that the mix of hydrocarbons and NOx obtained under steady motoring conditions can be a lot different to that obtained under cyclic conditions. There will always be grave doubts as to the accuracy and consistency of the procedure while results like those shown in Fig. 2 are obtained.

Chemiluminescent Analysers

The ozone-chemiluminescence analy­sis method has now reached a

predominant position for analysis of NOx. The method is based on the chemiluminescence of the reaction of ozone with nitric oxide or more cor­rectly by the photo-decay of the ex­cited NO2 molecule formed. The basic kinetics of the reaction have been studied by Clough and Thrush (20) and instruments developed for the meas­urement of nitric oxide have been reported on by Frontinjn et al.(21), Niki et al.(22) and Sigsby et al. (23). Instruments became commercially available during 1971 and are now very widely used.

The first instruments used low pres­sure reaction chambers (5 to 10 torr) but later models operate at close to at­mospheric pressure. The low pressure instruments have been found to require high vacuum pump maintenance due to the effect of the ozone on the pump oil. The use of fluoro-carbon oils obviates this difficulty but the savings in pump weight and cost favour the higher pressure instrument. The near atmospheric pressure instruments have been found by Kruse (24) and Zolner(25) to suffer negative interfer­ence from carbon dioxide. Kruse found that for each percent of carbon dioxide in the sample there is a 1% reduction in response to nitric oxide. He says that no such interference occurs with the low pressure instru­ment. Tests that we(26) have carried out at Sydney University indicate negative interference due to carbon monoxide of 1% in nitric oxide for each 5% of CO2 at a reaction chamber pressure of 11 torr. Out tests showed positive interference from hydrogen but only at concentrations above 40% which is of no interest in engine work.

Problems are often experienced with preparation of adequate reference standard gases, particularly at the low concentrations met with in the CVS procedure. Test gases in high pressure cylinders appear to absorb NO on the walls and this desorbs at low pressures. The concentration can vary appre­ciably with cylinder pressure. Don-nelly ( 1 1 ) has the following comment: "Still another problem was caused by not having good standard gases at the low concentrations obtained by CVS tests. We solved this problem by making our own NOx mixtures. The procedure used consisted of filling a Tedlar bag with an exact volume of pure N,. During the filling process an exact amount of pure NO was in­jected, using a syringe, into the bag along with the N2. This mixture be­came a temporary standard used to calibrate the TECO (Thermo Electron Chemiluminescent Analyser) and at the same time to recheck and revalue our NO calibration gases. The pro­cess was repeated many times at each concentration to establish statistical confidence and at several concent­rations to obtain a range of values."

Thermal Converters

The purpose of the NOx-to-NO or thermal converter is to convert NO2 in the sample to NO. This conversion is required since only the NO is meas­ured in the chemiluminescent analy­ser. The thermodynamics of the reaction favour the dissociation

2 NO2 2 NO + O2 at temperatures above about 500°C and dissociation is also favoured by low pressure. At a mixture pressure of 10 torr a sample containing 500 ppm NOx will only have 2% of that as NO2 in equilibrium at 650°C.

The kinetics of the gas phase dis­sociation reaction are however too slow for it to work in an analytical instrument but a stainless steel tube heated to 650 °C is found to adequately catalyse the reaction. The so-called "thermal" converter is in fact a cata­lytic converter.

Some trouble has been experienced in decay of converter efficiency and a check of this should be carried out periodically. A simple check is to mix NO with air and monitor the resulting NOx mixture as outlined by the U.S. Standard (16). A more convenient method has recently been developed by the U.S. automobile industry. This method uses an ozone generator to provide ozonated oxygen which is then mixed with the nitric oxide span gas to produce nitrogen dioxide (24).

There is also some evidence that the converter tends to oxidize ammo-­nia to NO but since ammonia con­centrations in gasoline engine exhaust are only 6 ppm at a maximum (Schuch-mann and Laidler(27) ) this is un­likely to be much of a problem, and certainly the use of lower temperature converters with more effective cata­lysts (Hodgeson et al.(28) ) will not work at high NOx concentrations since the NO2 will remain unconverted.

Most of the experience on NOx — to — NO converters has been accum­ulated in the United States where ex­perience is largely confined to systems which have large excess of O2 as in the CVS procedure. (In the continuous sampling procedure only NO is meas­ured). There is some experience to indicate that catalytic reduction of NO on hot stainless steel can occur under fuel rich conditions. Hal-stead (29) reported such reduction occurring in sampling probes. Recent experienced) with our own NOx anal­yser indicates complete reduction with CO levels above 12% and H2 levels above 6%. With 3% hydrogen and no oxygen present one-third of the nitric oxide was reduced. However, when 1 or 2% of oxygen was present hydro­gen concentrations of over 10% were required to cause reduction of the nitric oxide. Kruse (24) comments that this occurence has been found during the use of combined calibration gases

48 Clean Air / August, 1973

such as CO and nitric oxide with balance nitrogen. Bartok et al.(30)

review NO catalytic reduction tech­nology. It is now apparent that the presence of oxygen in the sample can forstall the reduction reaction. The amount of oxygen required will pre­sumably depend on the residence time in the converter but in any case should not be in excess of that re­quired to oxidize all of the CO, hydro­gen, and other reducing agents. The addition of oxygen to the sample is recommended in all work with fuel rich exhaust gases.

NOx Measurement in Total Bag Sampling Test

There is a need for a standard proced­ure to be developed for measurement of NOx emissions with the ECE 15 and ADR 27A procedures already in use for measuring CO and hydrocarbons. From what has been said above there are two feasible approaches.

1. To fully explore the extent and dependence of the NOx hydrocarbon reactions in the bag so that adequate extrapolation procedures can be devel­oped.

2. To continuously sample the ex­haust during the test procedure and appropriately weight the results to obtain a suitable average. The weight­ing function will be arbitrary but could be fixed upon after suitable in­vestigation of mode mass flow rate. The result of this method will be a completely consistent standard. It will be no more arbitrary than the driving cycle used in the test procedure.

The final choice between these approaches will depend on many fact­ors but it is believed that both are worthy of further investigation.

Clean Air / August, 1973 49

Andrew E. O'Keeffe

Measurement of air quality requires instruments which go beyond the simple modification of analytical chemical methods. Sophisticated techniques such as chemiluminescence, modified chromatographic and light scattering are now being adapted to air pollution instrumentation.

Mr. O'Keeffe is the Chief of the Air Quality Measurement Methods Branch of the Division of Chemistry and Physics, Bureau of Air Pollution Sciences, Environmental Protection Agency, Research Triangle Park, N.C. 27711.

This paper is based on the keynote address given by Mr. O'Keeffe at the International Clean Air Conference, Melbourne, May 1972.

THE OLD, THE NEW AND THE FUTURE IN AIR POLLUTION INSTRUMENTS

Introduction: When the need to con-tinuously monitor and record ambient concentrations of air pollutants was recognized some 20 years ago, traditional wet chemical methods were automated, and existing process con-trol instruments were modified to enable readings to be made at much lower concentrations. The resulting techniques frequently involved absorp­tion in aqueous solutions and subse­quent reaction with a reagent to give a coloured product. The extent of the reaction was followed by measuring the absorbance of monochromatic light with a photoelectric sensor. Sometimes the concentration of a pollutant was determined by continu­ously passing ambient air through a sample cell and measuring the atten­uation of a narrow portion of the electromagnetic spectrum which was directed through the cell.

The methods used were often defi­cient in regard to sensitivity, specificity and rate of reaction. Moreover being so often based on absorbence tech­niques the electric signal generated was inversely related to the concent­ration of the species under test. For the low concentrations at which air pollutants exist in ambient air this meant that measurements generally depended on a small difference of two large signals — this was inherently an unsatisfactory procedure. However, today we need ever more rapid, sen­sitive and precise methods. The search for improved techniques has led us to a family of superior instruments which have either only recently reached the market or are at present under development. It is the purpose of this paper to consider the principle of operation of some of these devices.

The Flame-Photometric Detector In the flame-photometric detector (FPD) for sulphur gases, also adapt­able for phosphorous-containing com­pounds and for several other conceiv­able possibilities, a sample of air entering through the small tube on the side of the burner enters a hydro­gen-rich flame. In such a flame all sulphur compounds in the sample are converted to diatomic sulphur. The diatomic sulphur is thermally excited and rises above the flame in an excited

state S*2. There it cools off and returns to ground state, emitting light, hav­ing its major emission at about 375 nanometers. That light is viewed by a photomultiplier through a filter which excludes light of other wavelengths. The signal produced by the photo-multiplier is amplified by an electro­meter, giving a real-time recording of the quantity of sulphur containing gases in the entering sample.

In most air pollution situations it is reasonably certain that total vol­atile sulphur and sulphur dioxide are for all intents and purposes synony­mous. If one had other volatile sul­phur compounds (such as H2S) pre­sent to an extent of more than a few percent of the SO2 present, even at background levels one would be warned by the odour that he had a potential interference and would take necessary steps to accommodate that to the situation; thus it can be seen that, in most situations, the FPD, just as described, is a valid measure of sulphur dioxide.

For the odd case, where the above assumption is not valid, one can use gas chromatographic separation of sulphur dioxide from other volatile sulphur compounds coupled with a flame-photometric detector. A sample of air is continually drawn through a sampling valve. Meanwhile carrier gas is passed through a second port in the sampling valve then through the chromatographic column to the flame-photometric detector, and of course no signal is seen. Periodically the valve is rotated through 180°, thus injecting a small sample of the air into the carrier gas stream going through the column. This column is most unusual in that it has the ability to pass sulphur gases down to parts per billion. All previous attempts to chromatograph sulphur dioxide (for example) had failed at about the 1 to 10 ppm level. We were fortunate to find a combination of column and packing which would permit measure­ments to be made at these low con­centrations. It consists of a Teflon tube which is essentially completely inert to these reactive gases, packed with powdered Teflon (also quite inert) coated with polyphenyl ether, also quite inert. The partition between

50 Clean Air / August, 1973

gas phase and liquid phase takes place within the polyphenyl ether layer on the Teflon particles, and under this fortunate combination of circumstances we do obtain real and highly sensitive separations of the sulphur gases.

The signal from the flame-photo­metric detector goes through the usual electrometer to a recorder, and the readout is in chromatographic form, ELS being eluted from the column and contributing its signal immediately following a small air peak, followed by sulphur dioxide, methyl mercaptan, dimethyl sulphide, dimethyl disul-phide and so on, for a continuing series of organic sulphur compounds. Since the flame photometric detector is specifically selective to compounds containing sulphur, hydrocarbons and the like do not appear in the record, i.e. they do not interfere.

A somewhat simplified method for obtaining selectivity between SO2 and HS consists of providing, ahead of the flame-photometric detector, a filter of silver wool held at about 100°C. H2S in the incoming air sample is perm­anently held on the silver, while S02 passes through quantitatively. We thus have a very simple means of measuring SO2 in the presence of other sulphur-containing substances. It will be evident that the degree of specificity (for SO2) imparted by this strategy can never be complete in the absence of an empirical determin­ation for each and every conceivable sulphur-bearing substance; neverthe­less an instrument of this type has very real utility, provided its limit­ations are known and understood.

Chemiluminescent Nitrogen Oxide and Ozone Detectors

Let us now consider the chemilum­inescent nitrogen oxide detector shown in Fig. 1. It consists of a reaction chamber A, into which an air sample is drawn. Meanwhile one supplies an excess of ozone. The whole chamber is kept at about 1 torr by the pump, B. Under these circumstances the ozone-NO reaction takes place and emits light; the light is filtered to get rid of the signal due to extraneous ozone — olefin or, ozone-aromatic reac­tions, etc. The light arising from the

ozone-NO reaction is observed by the photomultiplier, the signal is ampli­fied and appears instantly on the re­corder as an indication, of the nitric oxide entering the instrument.

The same instrument can be made to measure NO2 by the simple exped­ient of converting NO2 quantitatively (or reproducibly) to NO and measur­ing this correcting, of course, for any NO originally present. The conversion is presently accomplished by passing the sample stream over a bed of gold wool at 220°C.

This same instrument can also be used to measure ammonia by using a similar converter, held at 250°C, to convert ammonia to NO. Obviously when operating in this mode one reads NO, NO2 and ammonia. To untangle ammonia information, one may either correct subtractively for NO and NO2 or periodically remove the ammonia from the sample stream by passing through a short section of glass or quartz tubing coated on the inside with phosphoric acid. The difference in readings with and without the phosphoric acid scrubber is wholly attributable to ammonia.

The instrument described in the preceding paragraphs is the low pres­sure version of the chemiluminescent NO device, operating at about one torr. Another more recent version of this operates at pressures approaching one atmosphere. Some sensitivity is sacrificed in such an instrument, but we find that it still retains sufficient sensitivity for the measurement of NO and NO2 at ambient levels; i.e. down to the parts per billion range. The geometry of the instrument is such that two streams, one containing ozone and the other nitric oxide, enter the reaction chamber separately and meet in a sort of Bunsen burner. In the mixing zone, the two gases are sufficiently protected from air quen­ching, so that luminescence does take place, the nhotomultiplier is able to observe that luminescence even though the instrument is operating at atmospheric pressure (a condition that ordinarily completely quenches ozone/NO luminescence) and of course we get a signal, which is handled in the customary manner.

The chemiluminescent ozone in­strument, operates on exactly the same principle. As a matter of fact it was the success of the ozone instru­ment that led to the question, "Why shouldn't we try the NO instrument at atmospheric pressure?" This was based on some work by Nederbragt in Holland, about 1965, in which he re­corded the ability to mix an air sample suspected of containing ozone with pure ethylene and to observe the lum­inescence due to the ozone-ethylene reaction. In other respects, this instru­ment is virtually identical with the NO-ozone device just described.

Clean Air / August, 1973

Carbon Monoxide Detection In Fig. 2 we see a totally different kind of instrument. This is an instru­ment that I think has great potential within the area of nondispersive in­frared (NDIR) instrumentation. The usual nondispersive instrument for measuring carbon monoxide, for ex­ample, uses black body radiation and senses the attentuation in a sample cell due to the presence of carbon monoxide. It is interfered with by water, carbon dioxide, methane, and perhaps other substances. The present instrument was proposed by Dr. William Link. It used a radiation source which emitted specifically the spectrum of carbon monoxide that would be attenuated in the sample cell and would not suffer interference from water, CO2 and so on. We first built this using a black body source, to excite fluorescence in a carbon mon­oxide-filled cell, and using the fluore­scent emission as the source of energy for a non-dispersive infrared instru­ment. This suffered from having less sensitivity than was really desired.

As an alternative the CO was en­closed in a hermetically sealed cell connected to a bellows. Within that cell, the CO is rapidly compressed and expanded. Under these conditions there is thermal emission from the carbon monoxide molecules. This emission is an exact match for the absorbance spectrum of carbon mon­oxide. If any CO is present in the sample cell it will absorb the light in proportion to its concentration and thus, with the help of the phototube and amplifier, produce the appropriate signal. In contrast to the fluorescent-NDER device that works only for CO, the pressure-induced luminescence principle appears to be applicable to many other gases as well.

Fig. 3 depicts our solution (perhaps temporary), of the problem of deter­mining carbon monoxide at levels below those that can be reliably sensed with the existing non-disper­sive infrared instrumentation. In addition to carbon monoxide It also simultaneously determines methane and total hydrocarbons. A sample enters through valve A. Periodically valves B and C are rotated, a sample is brought Into a short pre-column upon which moisture and organic sub-

51

stances heavier than methane are retained. Methane and carbon mon­oxide pass through. After a short period — once carbon monoxide and methane have passed through — the valves are reversed to inject an air sample directly into the flame ioniz­ation detector, giving a reading for total hydrocarbons. Meanwhile, the carrier gas is moving the carbon mon­oxide and methane through the analytical column where a separation is performed. Unfortunately there is no convenient detector for carbon monoxide, so the effluent from the column is passed through a nickel catalyst at about 300oC, hydrogen is added, converting CO to methane and giving two methane peaks at the detector, the first one being recorded as carbon monoxide and the second one as methane. Altogether, we obtain a strip chart record in the form of a repetitive bar graph which records total hydrocarbons, carbon monoxide and methane.

Microwave Absorbance Spectrometry We have a contract with Lawrence Radiation Laboratories, who are put­ting together a prototype device to evaluate the utility of microwave ab­sorbance spectrometry as an air pollu­tion measurement tool. Microwave energy enters an analytical cell, passes along it and is picked up by a detector at the other end. Meanwhile a gas sample is continuously drawn through the cell and the receiver end of the microwave system is feeding inform­ation to a strip chart recorder. It is characteristic of microwave spectra that the lines are extremely sharp when operated at high vacuum as this instrument would be, and that one is able to find among the great wealth of such lines a single one that will correlate with a given substance with complete specificity and hopefully sufficient sensitivity.

Detection of Sulphuric Acid Mist

The next device, illustrated in Fig. 4, exists only as a concept at present. It remains to be seen whether it can really function and it is concerned with one of the oldest known air pollutants, sulphuric acid mist.

If one looks with a forward-scatter photometer at a particle that may or may not contain sulphuric acid, repre­sented by the top open circle, the photomultipller will see a quantity of forward scatter related to the particle size, the number of particles present in the sample and the optical proper­ties of those particles. If one takes a second look (represented by the lower solid circle) at this same particle population after exposing it to hydro­gen iodide there should be, according to the equation at the bottom, a dras­tic change in the optical properties of the particles, but little or no change in their number, nor in their average size. Therefore the forward scattering will have been attenuated sharply by the presence of sulphuric acid. Ob­viously this is going to be less than totally specific. It will respond to any strongly oxidizing material present; nitric acid certainly would give a false reading, as well as hydrogen peroxide and probably other interferences. If we are able to go from a condition of having no way of reading sulphuric acid mist to one of being able to say that we either have sulphuric acid or perhaps we have nitric acid, etc., we will have made, I think, a major advance in the monitoring of this pollutant.

Photofragmentation Instruments

Another potential solution to the nitrogen dioxide problem is being developed. A prototype of this instru­ment has performed beautifully; quite conceivably it could give birth to another family of instruments which the people involved have christ­ened photofragmentation instruments. Nitrogen dioxide entering the system is photolyzed by strong ultra violet light from a mercury or xenon source, generating O atoms. The O atoms are carried through light traps so that the exciting energy isn't carried forward to a reaction chamber. Nitric oxide is added there and reacts with the O atoms produced from the NO2. The luminescent reaction involved is the O plus NO reaction which is observed by the usual photomultiplier-electro-meter combination and is recorded.

Pollutant Detecting Using Semiconductors Another series of potential instru­ments which could be produced in very small form, and at low cost may be developed from, semiconductors. For example, zinc oxide is known to exist with a crystal lattice in which an occasional atom of oxygen is miss­ing. It; certainly is quite reasonable to suppose that oxygen in the atmos­phere above such a crystal will reside in that crystal imperfection during a portion of the time related to the

partial pressure of such oxygen. In other words, if one had no oxygen at all above it, the semiconductor device would have some given resistance, while it if were exposed to one at­mosphere of oxygen it would have a lower resistance. This broad area has been extensively examined by several workers, over 15 or more years. It was recognized, as soon as semiconductor devices became known, that they must necessarily be covered with an imper­vious coating, usually of silica, to protect them from changes in the ambient. So what is simpler than to reverse that process and deliberately leave off the protective coating and have a device which will be sensitive to changes in the ambient? Unfortun­ately, these changes are seldom, if ever, specific; for example zinc oxide, reacts to oxygen but also to methane and many other gases.

It is conceivable however, that if one does not seek a single sensor com­pletely and specifically sensitive to a single pollutant, but looks instead for what I call quasispecific detectors; one device that is primarily sensitive to oxygen and secondarily to many other gases, another one that is prim­arily sensitive to SO2 and secondarily to many other gases, and so on. If one can, using a fairly simple com­puter, unravel the matrix of inform­ation coming from a battery of such sensors, one will have a mass-pro­ducible system capable of measuring many different pollutants. This or some similar concept can in the future provide the number of air pollution sensors that will be needed to make a reasonable and operable control of air pollution possible.

Permeation Tubes

One development, dating back about 5 years, whose very existence has greatly accelerated the evolution of air pollution measuring instruments, is the permeation tube. This simple device provides a reliable source for the generation of precisely diluted mixtures of pollutants in air, thus enormously simplifying the otherwise tedious task of validating the sen­sitivity, accuracy, precision and specificity of an instrument during or after development. The construction

(Continued on page 63)

52 Clean Air / August, 1973

S. Stanley FABRIC DUST COLLECTORS

While fabric dust collectors are one of the most frequently used types of units for air pollution control their practical design is as much an art as a science. This paper is concerned with all design aspects, from the selection of the filter cloth, based on the characteristics of the fibre, to the housing and different modes of reconditioning the fabric surfaces in operation.

Mr. Stanley is Technical Manager, Corporate Planning Group, Malleys Ltd. and was formerly Technical Manager of Malleys Bahco Engineering, which specialized in air pollution and air handling. Before this, the author designed environmental control systems with consultants in Hungary and Australia This paper is based on one given as part of the course sponsored by the Clean Air Society in the Control of Air Pollution, at the University of New South Wales.

introduction: When high collection efficiency is required for fine particles, the most frequently used industrial equipment for the separation of dust from a carrier gas is the fabric dust collector. In these units three basic elements are present: the conveying gas (frequently air), the airborne particles and the porous layer.

While mechanical dust collectors, wet scrubbers or electrostatic precipit­ators all employ some kind of ingen­ious design feature for the separation of particulate matter from the gas stream, the filtration principle em­ployed in the fabric dust collectors is, or at least appears to be, a simple straightforward process: the air is passed through the porous layer and the airborne particles are retained on the entry side.

The Filtration Process: The actual mechanisms of filtration in fabric dust collectors is a complex process which is aided by other actions and depends on many variables.

The conventional filter consists of textile fibres in a porous layer, in which the spaces or voids between fibres are usually much larger than the airborne particles. The collection is therefore not just a sieving oper­ation, although some of the particles are, of course, separated due to a siev­ing effect. Thus, all particles which are bigger than the pores will be trap­ped, but particles are also separated if size and shape of the voids in the medium do not correspond with that of a particle. In fact, separation is mainly caused by the inertial impac­tion of particles on the fibres. When the particles approach the filter fibre, the heavier ones cease to follow the gas stream lines around the fibres; they hit the fibres and are separated.

An important additional factor, particularly for sub-micron particles is the diffusion effect. Here particles follow the stream lines and are sub­ject to "Brownian" motion. In this random movement of the particles, they contact the fibre surface and are separated. There is the additional possibility of electrostatic effects; de­pending on the electrostatic charge of particles, and on the media, they are either attracted or rejected by the filter media.

Filter Cake Formation and Resist­ance to Airflow: Once the separation process has started, a considerable dust layer will accumulate on the filter surface and between the fibres. This layer will then act as a filtration cake.

The particles deposited in the pores in the medium and on the sur­face of the fibre layer greatly modify its performance characteristics. The particles retained act as secondary collectors and can be much more effective as they present targets of approximately the same size as the particles to be collected. The dust which accumulates as a layer or cake on the surface will therefore assist to retain the very small particles. This, however, cannot go on indefinitely, and from time to time some of the dust cake must be removed. As it is most important that not all of this dust cake is removed, reconditioning the filter layer is a very delicate process.

While many different theories have been advanced on the processes that take place in fabric dust collectors and a number of attempts have been made to develop formulas or equations on the flow resistance and the effi­ciency of the process, many experi­mental factors have to be introduced and the theoretical considerations can only approach the problem. The resistance to flow in a fabric dust collector through the porous layer will

Clean Air / August, 1973

Table 1.

Basic Properties

Width of cloth

Dia. of filter tubes

Length of filter tubes

Threadcount

Thickness

Unit mass of cloth

Density of fibre material

Permeability*

Temperature

New Metric Unit

cm

mm

m

per cm

μm

g/m 2

kg/m 3

litre/sec./m 2

at 200 Pa pressure drop

°C

Important Properties for Filter Fabrics

Old British Unit

inch

inch

feet

per inch

inch

02./sq. yd.

g/cm 3

cfm/sq. ft. at 1/2" WG.

°F

Conversion Factor

2.54

25.4

3.281

.394

25400

33.9

10-3

7*

(F-32) 5/9

* (The Permeabi l i ty value is n o t directly proport ional to pressure drop. In the old imper ia l system 1/2 in. WG pressure drop is used. In metr ic pract ice usually 20 mm WG. It is s u g -gested t h a t t h i s now should be set as 200 Pa. The conversion figure of 7 is only approx imate ; the new value should be determined experimentally w i t h the new parameters) .

depend on the "permeability" or "clean cloth resistance," the gas flow rate, the density of the gas, the dust burden, the dust particle size and time. The resistance of the porous layer will increase and eventually either all or part of it will have to be restored to the low resistance con­dition selected at the design stage. The total overall resistance of the fabric dust collector unit will also depend on the configuration of .all parts of the unit, from entry to outlet, the gas velocity and flow characteris­tics.

The resistance of a fabric dust

collector unit must be considered to­gether with the resistance of the ex­haust system it is connected to and the characteristics of the exhaust fan. For preference the exhaust fan should have a steep pressure volume charact­eristic. This will ensure slight vari­ation in exhaust volume and duct velocity (Fig. 1).

Fabric Collectors, Parts and Con­struction: The first examples of fabric dust collectors were large screens, where the contaminated air was dis­charged into a screened enclosure and the air found its way through the fabric. Later, installations with large

bags suspended in "bag rooms" were developed. In large installations of this type, special buildings — bag houses - were constructed. In smaller units

fabric sleeves were suspended from a header without any protective casing around them. As better engineered dust collectors were requested, units incorporating a group of fabric sleeves enclosed in a suitable housing were developed. The built "bag house" was converted into a manufactured bag collector. The housing was made watertight and airtight and could be placed adjacent to and outside the factory building, and the exhaust fan placed on the clean gas side, after the collector.

The following factors must be considered in a modern collector unit design —

1. Type of porous layer. 2. Reconditioning mechanism and/

or action and control equipment. 3. Inlet and outlet mainfold and/or

connections, dampers. 4. Casing or housing, dust storage

hopper or hoppers. 5 Dust disposal equipment. 6. Supporting structure, ladders,

platforms. Design: The basic design of a

fabric dust collector starts by estab­lishing the volume of gas to be treated, its temperature and the type and quantity of the dust carried.

Selection of the filtering medium and the flow velocity (the air to cloth ratio) is the most important step. According to the physical and

Table 2. General Properties of Fibres

Fibre

COTTON

WOOL

NYLON (Polyamide)

TERYLENE (Polyester)

ORLON-DRALON (Polyacrylonitrile)

POLYPROPYLENE

NOMEX (Polyamide)

GLASS

Acid Resistance

Poor

Very Good

Fair

Very Good

Excellent

Excellent

Fair

Excellent

Alkali Resistance

Fair

Fair

Excellent

Good

Fair

Excellent

Excellent

Fair

Recommended Safe Temp.

70°C 190°F

95°C 200°C

120°C 250°F

140°C 280°F

120°C 250°F

95 "C 200 "F

250 "C 480"F

275"C 525°F

Flex & Abrasion Resistance

Fair

Fair

Excellent

Very Good

Fair

Very Good

Very Good

Poor

Cost Index of Filter Bags*

1

2.2

1.5

1.8

2.0

1.3

4.5

4

Notes

Poor resistance to mildew and fungi

Similar to those of cotton

High tensile strength good elasticity. Unaffected by mildew and fungi

High tensile strength Excellent dimensional

stability

Resistance to moisture Not harmed by common

solvents

Density, chemically resist­ant to acids and alkalis

Excellent resistance to high temperature, high tensile strength

Low mechanical strength hence vulnerable to abrasion

• The coat Index shows the approximate relative cost of bags of the same proport ion and size made f r o m the various materials. However, when calculating owning cost of bag collectors the l i fe of bags should be taken into consideration and also the expense Involved In changing the bass. Jn many Instances the better and more expensive material w i l l result In cheaper owning cost.

54 Clean Air / August, 1973

chemical properties of the dust partic­les; the substance, the construction, the shape and the size per unit volume of the porous layer will have to be varied.

A great variety of cloths can be used as filtering media. To make the best selection it is essential to know their characteristic properties, these are determined and listed by manu­facturers who specialise in industrial fabrics. The skilful designer of the dust collecting equipment will make his selection to suit the dust and the process involved. However, it must be kept in mind that the knowledge of these properties whilst a great help and guide, is never an absolute assur­ance of satisfactory collector perform­ance. There is no simple comparison between the very wide range of filter cloths. Practical experience is import­ant and on difficult problems testing with truly representative pilot units is advisable.

The main properties which the collector designer must consider are the type of material or materials used for the fibre, the weight, t in perme­ability and the strength of the cloth or felt. Other properties listed by cloth or bag manufacturers and assisting in the choice are the thread-count, the type of weave and the finish.

The physical properties of filter cloth have been customarily given in British units in the past. Some manu­facturers have started to convert these to metric units, but their usage has not yet been firmly established. It would be desirable to agree to a uni­form set of units based mainly on the present usage in this industry and in Europe. The suggested units and con­version factors from the ones used up to date are as given in Table 1.

Filter Fibres and Fabrics: Textile materials used as filtering media can be woven or felted and made from a large variety of material. Until recently natural fibres such as cotton and wool were used. The introduction of synthetic fibres as filter media has given greater efficiency aid durability. Some of these are listed on Table 2.

Synthetic fibre yarns are manufac­tured in three forms —

(a) Continuous multi-filament: Several fibres of unlimited length twisted tightly together to produce a smooth yarn, the greater the number of filaments the bulkier and stronger the yarn.

(b) Staplefibre: Extended contin­uous fibre which is cut into short lengths. This must be then carded and spun into a yarn similar to the pro­cessing of natural fibres, namely cot­ton and wool.

(c) Monofilament: Unbroken lengths extruded in a coarse diameter of a single fibre.

Cloth can be produced from any of these basic yarns, either singly or

in combination. In conventional fabric dust collectors, the filtering media are woven cloth; the permeability is re­stricted largely to the open pores in the weave; very little air movement can take place through the twisted fibres in the yarn.

The weave employed must produce a stable cloth in which the threads cannot be easily pushed about and the pores between the threads are constant. Twill or satin weaves are much more stable than plain ones. Cotton satin makes a satisfactory filter media for general purposes and is slightly cheaper than the synthe­tics, although synthetic materials usually posses advantages over cotton. This can be the case when handling plain harmless non-corrosive and non-abrasive dust particles at normal temperature, but their advantages are more apparent when the gas stream is hot, moist or corrosive, abrasive or sticky, or with a combination of these difficulties. Wool makes an excellent filter cloth but it is heavy and expen­sive. Cloth which employs synthetic continuous filament yarn has a com­pletely smooth surface which results in some advantages, such as excel­lent cake release, good moisture resistance and easy cleaning. The regularity and smoothness of the fila­ment yarn permits the construction of very closely woven lightweight cloth which is capable of retaining the particles. The continuous form of the fibre results in high tensile strength.

Cloth made from staple fibre yarns have a lower tensile strength than those of the continuous filament but on account of their greater resilience have excellent resistance to abrasion and mechanical damage. They cannot be produced in as closely woven form as filament cloth but assistance is given to fine particle filtration by the hairy nature of the yarns. Cake release is not as efficient but this can be improved by surface treat­ment. Staplefibre may be spun either to the cotton or the woollen systems. The former are characterised by being fine and tightly twisted. Usually it is necessary to twist yarns together to produce bulk for a filter cloth. In the case of woollen spun yarns, sufficient bulk can be achieved by spinning and twisting a single thread. This is because of the more delicate way in which woollen spinning is effected. Cloth made from monofilament is completely smooth and has good mechanical resistance but it cannot be produced in close or even moder­ately close weave, and therefore, is not very suited to dust collection from a gas stream.

A successful filter cloth is based on filament and spun yarn, doubled to­gether in warp and weft. This type of material combines high tensile strength with resilience and good filtering properties and a rather goodl

cake discharge characteristic. In contrast to the woven cloth

there are various types of non-woven materials. Felted wool has been known and used for hundreds of years and its origins are lost in antiquity. One story relates that the inventor was a monk who, on one of his long pilgrim­ages, eased his sore feet by putting wool into his sandals. When he arrived in the monastery he found to his great surprise that he had made the first woolen felt insole. Heat, moisture, pressure and the motion of the feet had activated the felting properties of wool. The same four fac­tors are used in pressed felt manu­facture today.

Wool or hair felt was the first real non-woven material used. No spinning, weaving or knitting is re­quired because the element of felt is the single fibre, not a manufactured thread or yarn. The fibres are rand­omly oriented with spaces between. Pelts have a three-dimensional struc­ture.

At present the most important felts for dust collection are needle felts. The needle felting process produces tough strong fabrics by mechanical interlocking, without recourse to the use of bonding agents. In manufac­ture the fibre is laid out on travelling aprons to form a bat; a thick layer of fibres laid in different directions. The bat is then pressed down with boards containing needles with barbs which vibrate through the bat to intermingle the fibres and producing a complex interlocking. The final fabric varies in thickness from 1 to 8 mm. Using an assortment of natural and synthetic fibres, sometimes in blends, a compre­hensive range of needle felts can be produced.

All filter media, both woven and non-woven, should have the right finish. Cotton and wool fabrics should be preshrunk. Sometimes other finishes such as moisture proofing or fire-retarding are desirable, but care should be taken that if these are applied, the permeability of the filter cloth is not affected.

Synthetic materials should be heat-set and sometimes are silicone treated for better heat resistance. S^me of the synthetic fibres can have a strong static charge and these should receive antistatic treatment. In applications where the static charge could cause explosions, earthing wire strips must be used.

Handbooks on dust collection usually include tables of recommended filter media. No selection table can be complete and perfect, and while some guidelines can be given, an intelligent study of the process, trials and experience in usage are always im­portant. The closely woven materials

give high filter efficiency and are used where effective dust separation of fine particles is required. This results in

Clean Air / August, 1973

high resistance and low air to cloth ratio. A more loosely woven fabric produces lower efficiency but lower resistance.

Separation improves with the growth of the filter cake, but after each periodical cleaning process sep­aration deteriorates for a short while. Raised woven fabrics support the build-up of the cake due to the fibrous surface and are therefore more efficient, but the release of the cake is less perfect. After a while some of the fine threads that form the raised fluffy layer on the surface of the cloth will wear due to abrasion, continuous air blast and mechanical shaking or alternative reconditioning action.

Natural fibre felts are not now­adays used to any extent. Needle felts combine the useful properties of both felt and woven fabrics. They have a remarkable pore volume, as much as 80% or even more, therefore good permeability to air yet the fine pore felt achieves an efficient dust separ­ation, even if dusts are of very small particle size. For equal efficiency felts require a smaller filtration area, as they can be used at higher air velo­cities. By special callender treatment, the surface of the needle felt can be rendered smoother and thereby pro­viding easier cake release.

Bag House Arrangement: The fabric Alter or bag collector has a

dirty side and a clean side and the filter media provides the division be­tween. So as to provide a large surface area in a limited space the filter media is made up of a number of elements.

The Shape and Arrangement of Filter Elements: The filter elements can be of various shapes and sizes. The most popular arrangement is cylindrical sleeves or bags. The dirty air can be either on the inside or the outside. If the dirty air is on the inside the sleeves are usually attached to a tube plate at the bottom. Air enters the tubes from below the tube plate and as it is rising the air gradually passes through leaving the dust de­posited on the inside. The top of the bags are formed into a loop and are suspended from a hook or clamped to a cap shaped header. There are a variety of bottom and top attach­ments used. This is one of the areas where manufacturers are keenly com­peting for the best and yet inexpen­sive and simple designs. The attach­ments must be airtight and easy and quick to operate.

If the dirty air is on the outside of the bags, the air travels from the out­side concentrically inward. The bags therefore have to be supported by a cage or similar supporting structure, or they would collapse. The bags of this type of unit are usually attached and clamped on the top and have a circular bottom sewn to the cylind­rical section.

Units which have flat envelope type filter elements must also have supporting structures and the action is similar.

Most fabric dust collectors use 125 mm (5 in.) or 150 mm (6 in.) dia. bags larger ones, 187 (7 1/2) in.) 200 mm (8 in.) are also fairly common. The diameter of the filter sleeve influences its length. The air velocity in the throat of the bag should be moderate and from this criteria it has been established the practical rule that on shaker type collectors where the air to cloth ratio is in the order of 3.5 to 1 the length of the bag should not be more than 30 times the diameter. Very large dust collectors handling high volumes of air or gas must use larger bags. 250 mm (12 in.) diameter and 9 m (30 ft.) long bags are a popular choice for these units. All these popular diameters tie in with the usual cloth widths available.

Oust Removal from Bags: It has been mentioned that the dust accum­ulation on the surface and in the pores of the filter media will gradually increase the pressure drop and at least the major portion of this accumul­ation has to be removed, the filter media has to be reconditioned for continuous use.

Cleaning can be manual, semi­automatic and fully automatic. Small

fabric dust collectors which serve an intermittent process can be cleaned with a hand-operated shaker. For these it is important that instructions should be issued and some person be made responsible for the periodic cleaning or reconditioning. Larger units which serve an intermittent process with a heavy dust concent­ration, i.e. one which is stopped several times during the day should be fitted with mechanical shakers electrically interlocked with the main exhaust fan. A time delay must be employed and shaking takes place on all the bags in the whole unit for a short time after a short delay to make sure that the fan has stopped. If the process is continuous and cannot be interrupted, or where the dust burden is heavy, fully automatic timing for reconditioning must be used.

This can be time controlled mech­anical shaking, bag collapse or reverse air flow or a combination of these actions, but in each case combined with damper control as one section of the unit is reconditioning only and this part is isolated.

Reverse jets or pulse jets can recon­dition a section comprising of a few elements only, without isolation. These methods use high-pressure air not only providing reverse flow but also flexing of the sleeve. With these cleaning methods mainly felts with high air to cloth ratios are used, but not exclusively. The change in perform­ance of a fabric collector is shown on Figs. 2 and 3.

Shaking: Mechanical or hand shaking can be up and down, side­ways or in an arc. Shaking will not be effective if in their natural state the bags are not tight. Spring loading or adjustment must be provided in the suspension because bag length will vary slightly due to fabrication toler­ance. In usage even best quality material will change its length especially with change in humidity. Mechanical shakers are usually elec­tric motor actuated by means of cams, eccentric and shaker arms. Shaker mechanisms should be robust and easily accessible for maintenance. There should be no airflow during shaking or the dust shaken off will be redeposited onto the media. Bag col­lapse just before or during shaking will help to crack the filter cake and is often combined with the shaking. Collapse is caused by permitting a small volume of air to flow in the reverse direction.

Reverse Flow: Bag cleaning with steady reverse flow only is never as effective as shaking or a sharp, short duration air blast creating vibration in the bag. When reverse flow clean­ing is employed the bags are usually fitted with anti-collapse rings. These rings should be strong and attached to the bags completely covered to pre-

56 Clean Air / August, 1973

vent chaffing of neighbouring sleeves. It is advisable to use multi-filament cloth of a smooth finish with good dust release qualities. Reconditioning either with shaking or reverse air should be for as short a period as possible. The duration and the fre­quency will depend on the type of dust and the dustload. It is advisable to make the time adjustable and set the controls after commissioning. One section of one compartment will be reconditioned at a time therefore the others will have to carry the load and for a short time air velocity through the bags working will increase. This increase will depend on the number of compartments. It is not good prac­tice to have less than four compart­ments or the variation in velocity, re­sistance and therefore in flow could be noticeable and could cause block­ages in the exhaust system. In the "Reverse-Jet" type of dust collectors blow rings with small holes or slots against the cloth surface travel up and down the sleeves. Air for cleaning is blown through the slots creating reverse flow and flexing of the filter media.

Pulse-Jet: The Pulse-Jet type of dust collectors employ a nozzle in the throat of bags. The shape of the nozzle and the configuration of the throat will vary with the design. Com­pressed air at 40 to 100 p.s.i. is dis­charged from the nozzle for a very short duration. This quick sharp air blast does the cleaning. Special adjustable timers and pilot solenoid valve operated diaphragm valves are used for the blast control. The time duration is usually adjustable and can be as short as 0.05 sec.

In all instances where reverse air is used in some form or other it might be necessary to heat or at least temper or dry the air if there is danger of coundensation.

Filtration Air Velocity: The most important design parameter in fabric dust collectors is the filtration velo­city through the filter media. This will vary according to the type, particle size and concentration of the dust, the type of porous layer selected, and the reconditioning process employed. The higher the permissible velocity the smaller the unit, resulting in economy in cost and space. However, these high velocity units are more likely to give operational troubles.

Tables 3, 4 and 5 give guide lines but these must be used with discre­tion. For most of the dust collection problems, it is impossible to state which type of reconditioning system must be used to best advantage. Apart from the factors mentioned the choice will be influenced by the practice generally adopted in the particular industry and the preference of the person who makes the decision.

Inlet and Outlet Connections: Dust collectors with all the filter

elements in one compartment usually have a single air entry and outlet connection. Some designs feature mul­tiple connections even on single com­partment units for better air distrib­ution. The connections can be fitted with a cut-off gate or damper but frequently no dampers are fitted at all. Multi-compartment units must have some type of inlet and outlet manifold with connections to each

compartment. Either inlet or outlet or both connections are fitted with dampers. These dampers are usually operated by electric damper motors or air cylinders, their closing and open­ing and the reconditioning process are controlled from a timer. On many of the fabric collector designs the inlet manifold or distributor is built

into and forms integral part of the casing or hoppper. In some of the

Clean Air / August, 1973

Table 3. Recommended Maximum Filtering Velocities for Shaker or Reserve Flow Type Bag Collectors

Material Filtering Velocity

FPM

Cement crushing

Aluminium oxide, Bronze powder. Carbon, Cosmetics, Fertilizer (cooler, dryer), Graphite, Iron Ore, Iron Oxide, Lampblack, Lime, Paint pigments

Alumina, Brunswick Clay, Coke, Charcoal, Cocoa, Chocolate, Clay, Cleanser, Grinding (separators, cooling, etc.), Lead oxide, Manganese, Mica, Soap, Starch, Sugar, Soapstone, Talc,

Bauxite, Baking Powder, Ceramics, Chrome ore. Feldspar, Flour, Flint, Glass, Granite, Gypsum, Conveying, Plastics

Asbestos, Packers, Limestone, Quartz, Silica

Abrasives, Cork, Batch spouts, Oyster shell, Marble

Buffing wheels. Feeds and Grain, Canders, Rock

Cotton, Leather, Tobacco, Wood, Paper

1.50

2

2.25

2.50

2.75

3

3.25

3.50

Table 4. Recommended Maximum Filtering Velocity in Reverse-Jet Bag-Houses

Material Filtering Velocity

FPM

Graphite, Carbon (green)

Lead oxide fume, Metallurgical fumes, Tantalum fluoride. Zinc, Oxide

Carbon (calcined), Carbon (banbury mixer), Cement ( raw) , Cement (mi l l ing). Polyvinyl chloride (PVC), Sand scrubber, Zirconium oxide

Bauxite, Clay (green), Gypsum, Lime, Paint pigments, Phenolic molding powders. Starch, Sugar, Wood Flour, Zinc (metallic)

Aluminium oxide, Cement (finished), Chrome (ferro) crushing, Limestone (crushing), Mica, Soap and Detergent powder, Talc, Tobacco, Wood sawing

Clay, Vitrified Silicious, Enamel (porcelain), Flour, Refractory brick sizing (after f ir ing), Silicone carbide, Soy Bean

Grain

5

6

7

8

9

10

12

Table 5. Recommended Maximum Filtering Velocities for Pulse-Jet Type Bag Collectors

Material Filtering Velocity

FPM

Activated Carbon, Carbon black (molecular), Detergents, Fumes and other dispersed products direct from reactions, Powdered Milk, Soaps

Tannic Acid, Stearates, Starch, Silicates, Resins, Plastics, Pigments (Metallic and Synthetic), Metal oxides, Metal powder, Fly ash, Dyes, Dry Petrochemicals, Diatomaceous Earth, Cake, Ammonia Phosphate (Fertilizer)

Sugar, Sorbic Acid, Silica, Rock dust ores and minerals, Perchlorates, Limestone, Kaolin, Gum (natural), Flourspar, Coal, Clay and Brick dusts, Ceramic Pigments, Cement, Carbon black (finished), Aspirin, Alumina

Talc, Soda Ash, Sandblast dust. Sand, Sale, Rubber chemicals, Perlite, Lime (hydrated) Gypsum, Foundry shakeout. Fibrous and Cellulosic material, Buffing dust. Asbestos

Tobacco, Sawdust, Leather dust, Grain, Flour, Feeds, Cocoa, Cardboard dust, Cake mix

6

9

10

12

15

designs an inertia separator, baffle box or other similar feature is incorp­orated at the inlet to relieve the media of some of the dust load. Other designers prefer to collect the coarse particles together with the fine ones on the filter media, because the larger particles can help in the formation of a filter cake with good flow charact­eristics. The decision which principle to follow will greatly depend on the type and concentration of the dust to be collected.

The resistance of the unit will be built up from the pressure drops through the porous layer and the air flow resistance through inlet and out­let connections. The unit, from entry to exit, should be designed with due regard to air flow and unnecessary restrictions must be avoided. It is not good practice, however, to lower the air velocity on the dirty side to less than the carrying velocity and for even distribution into the various compartments a certain minimum velocity and resistance at the entry point to each section should be main­tained. If this is not done some of the sections will receive a higher load whilst others are not fully utilised.

Collector Housing: Fabric dust collectors are usually enclosed in a housing or casing. The construction of the housing will vary according to the size of the unit and with the pressure (positive or negative) in it.

If the fan is on the dirty side and air is blown into the collector the casing can be quite light and serves only as protection from weather or damage. If the fan is on the clean side, the enclosure must be airtight and has to stand the suction pressure of the fan. The housing can consist of completely welded or fabricated cubicles or modules or can be assem­bled from standardized flanged panels. The choice depends on economy of manufacture and transport and either type can give equally satisfactory results.

Hoppers: At the bottom of the col­lector housing hoppers will receive the collected dust. The type and shape of hopper (or hoppers) depend on the dust handled and the proposed method of dust disposal. On very small units it can be just a dust drawer; on larger single compartment units a hopper tapering to one dust container or to a dust valve; on large units a long V-shaped hopper with a built-in conveyor and on very large units a number of these large hoppers.

The angle of hoppers should be as steep as possible, and should be pro­vided with cleaning and inspection doors, poke holes, and in certain applications with mechanical vibra­tors. Usually there is more operational difficulty with hoppers than any other part of the collector. Some dusts have a tendency to cling to­

gether and arch across the steepest section. A complete "live" bottom (a number of parallel screws) is the only practical solution.

If the fabric dust collector is hand­ling hot gases with moisture content, care must be taken that they should not cool below the dew point or con­densation will occur. In these cases the housing and the hoppers may have to be insulated. If the gases are corrosive all internal surfaces must be given special finish to suit the application.

Dust Disposal: In many instances collectors must have suitable hoppers to store the collected dust until dis­posal of the dust can be conveniently arranged. Due consideration should be given to conveyors and dust valves. They should be robust and leakproof. In some units, the dust is constantly discharged with the aid of a screw conveyor, air slide, scraper conveyor or other similar means and an un-loader valve or rotary air lock. In other instances the collected dust is conveyed to a suitable spot, into storage tanks or bins by pneumatic conveying systems. In many instances the collected dust can be reused, or has commercial value and efficient trouble free dust disposal equipment can contribute to the overall economy of the plant.

Care should be taken not to create a new dust nuisance with the dust disposal. Manual or open handling should be avoided. Wetting and/or pelletizing of the dust is often em­ployed to achieve clean removal. This of course can not be employed where the collected dust must be reused in its dry form.

Support Structure: Fabric dust collectors are usually supported on a structural steel stand. The height of the stand will depend on the dust dis­posal system. Even if this is at the inception a simple manual operation it is a good idea to have sufficient clearance from the ground for a more complex dust disposal system at a future date.

Access ladder or steps and service platforms should be provided to all levels and locations requiring inspec­tion and maintenance. Stands, ladders and platforms must comply with the usual design requirements. Found­ations should be calculated for loads with both empty and full hoppers.

Conclusions

The engineering task in fabric filter design is to produce an efficient device which will not deteriorate in efficiency during the daily cycle of operation or in the long term. Clean­ing and maintenance should be kept to a minimum, and carried out in ordinary working time. These collect­ors have low resistance to airflow and are therefore economical in oper­

ation. They have large dustholding capacity and are equipped for the disposal of the dust without further hazard. The installation must be such that the danger from fire or explosion is eliminated. The units occupy a min­imum of space and above all fulfill the most important criteria of low cost.

In practice all the different types of fabric dust collectors used are the results of attempts to approach the ideal unit incorporating as many as possible of these desirable features.

To what extent one or other of the criteria is considered preferable should be a matter of careful study and should be matched to the overall manufacturing process it serves.

Further Reading Filters — General Perry, B. H„ Chilton, C. H. and Kirkpatrick, S. D., eds. Perry's Chemical Engineer's Hand­book, 4th Ed., McGraw-Hill, 20.76-20.79 (1963). Damelson, J. A., ed Air Pollution Engineering Manual, U.S. Dept. or Health Education and Welfare, Public Health Service, National Centre for Air Pollution Control, Cinclnatti, pp. 105-135 (1967). Industrial Ventilation: A manual of Recom­mended Practice toy Committee on Industrial Ventilation of the American Conference of Governmental Industrial Hyfricnists. Mr. M. M. Schuman, Michigan, Chairman, P.O. Box 453, Lansing, Mich., 48902, U.S.A., Tenth Edition 1970 reprint, Section 11. LoefTler, F., "Collection of Particles by Fibre Filters." Chap. 6 in Air Pollution Control, Pt. 1, ed. W. Strauss, Wiley-Interscience, New York, pp. 337-375, (1971). Properties of Fibres "Chemiefascern" Deutscher Fachverlag GmbH. Frankfurt/Main. Freiherr-von-Stein 7-3 p. Pt. 10, October (1960). Knlep, E., "New ways for dedusting with synthetic fibre filter media." Wasser, Luft and Betrieb, 5 (Feb. 1961) (reprint). Long, W. L., "Nomex Nylon — a new high temperature filter medium." Paper No. 46B presented at 55th National Meeting of the Am. Inst. Chem. Engineers at Houston, Texas, U.S.A., February 7-11 (1965). I.C.I. Industrial Fibres Manual. Edition 1, Section 2/1. The Physical Properties of LCI. Fibres for Industrial Uses. Issued by I.C.I. Fibres Ltd., Harrogate, Yorkshire, England, 8 p. (1968). Physical Properties of "Terylene," Edition 1, Section 1, Section Al. Technical Information Manual. Issued by I.C.I. Fibres Ltd., Harrogate, Yorkshire, England, 6p. (1969). Du Pont Fibres in Industry. Issued by E. I. Du Pont De Nemours & Co., Wilmington, Delaware, U.S.A. (1960), 84 p. particularly pp. 19-21 and 61-82. LoefTler, F., "Separation efficiency and pressure loss for filter materials of different structure and under different conditions" Staub-Rein-halt, Luft 30 (12) 518-22 (1970).

Errata

The following correction to the article "A Basic Bibiolography for Sampling and Analysis of Air Pollut­ants," Clean Air, 7 (1), 21 (1973), should be noted —

(a) "Ann Arbor Science Publishers Inc." is the correct name of this com­pany and not Ann Arbor Publishers (as printed).

(b) "The Particle Atlas" and "The Particle Analyst" are both out of print but a new four volume set "The Particle Atlas," Edition Two, Dr. W. McCrome, is now available.

J. BAGG

58 Clean Air / August, 1973

S.I. UNITS AND THE AIR POLLUTION ENGINEER

It was announced early in 1970 that the metric system of weights and measures would be introduced pro-gresively into Australia in this decade. As a result engineering and science students at Universities and Colleges of Advanced Education are being taught in these units, text books and tables increasingly use metric units, and more and more of our products and materials are being measured and sold in units based on a metric system.

The metric system being used is known as the S. I. System, because of its French title "Systeme Inter­national d'Unltes," and it is simpler and more restrictive than the metric "c.g.s." (centimetre, gram, second) or "m.k.s." (metre, kilogram, second) systems that many of us have learned; it uses neither the calorie as a unit of heat, nor the poise as a unit of viscosity. The confusions of the "e.s.u." system of electrical units are avoided, and no longer will one have to worry whether it is an Imperial gallon or a U.S. barrel.

Basic S. I. Units: The basic units in the S. I. system are the kilogramme (mass), metre (length), second (time), Kelvin (temperature), ampere (electric current), candela (the unit of luminous intensity) and radian (angular measure). All but the last are commonly used by the air pollu­tion engineer. The Celsius scale of temperature (0°C = 273.15°K) is com­monly used instead of the absolute or Kelvin scale.

Derived S. I. Units: The important derived units are the Newton (S. I. unit of force), the joule (S. I. unit of heat and work), the watt (S. I. unit of power), the pascal (S. I. unit of pres­sure), the hertz (unit of frequency); as well there are a number of elec­trical units, viz. coulomb (charge), farad (capacity), henry (inductance), volt (potential) and weber (magnetic flux).

Metric Multipliers: One of the major advantages of the metric system is that larger and smaller units are given in powers of ten. In the S. I. system a further simplification is introduced, by using only those units with multiples of 10*. Thus for lengths, in engineering, the micro­metre (previously micron), millimetre, and kilometre will be used, and the centimetre will be abandoned. A further simplification is that the decimal point will be substituted by a comma (as in Prance, Germany and South Africa), while the other num­bers, before and after the comma, will be separated by spaces between groups of three, i.e. one million dollars will be "$1000 000,00."

Table 1 gives the prefices and mul-

Table 1.

Prefix

Tera

Giga

Mega

kilo

-

milli

micro

nano

pico

Prefixes, Symbols and Multipliers for the S. 1. System

Symbol

T

G

M

k

-

m

M

n

P

Multiplier

10 1 2

10 9

106

103

-

10 - 3

10-6

10-9

1 0 - 1 2

Table 2.

Quantity

Length

Mass

Electric current

Time

Frequency

Energy

Pressure

Force

Power

Electrical

Charge

Potential Difference

Resistance

Conductance

Name

metre

millimetre

micrometre

kilometre

kilogram

gram

milligram

ampere

second

minute

hour

day

hertz

joule

pascal

Newton

watt

Symbol

m

mm

μm

km

kg

g

mg

A

s

min

hr

day

Hz

J

Pa

N

W

Definition

—

10-3 m

10-* m

10-3 m

1 0-3 kg

1 0-4 kg

—

6 0 s

3600 s

86400 s

S-2

kg m 2 s"2

kg m-' s - 2

kg m s-'

kg m 2 s-3

Basic and Derived Units

Conversion

3.281 ft. 39.370 ins.

0.03937 ins.

3.937 X 10-5 ins.

5/8 mile

2.2046 lbs.

0.03527 ozs. 15.432 grains

0.01542 grains

—

— —

—

0.239 cal. 9.48 X 10 - 4 B.t.u.

Nm-2

4.146 X 10-3 ins.

W.G. (4 °C)

0.10197 mm W.G. (4°C)

2.953 X 10-4 ins.

mercury (0°C)

7.50006 X 10-3 mm

(0°C) ( t o r r )

9.869 X 1 0 - 6 a t m .

J m - 1

10 5 dyne 0.2248 lb. (force)

Js-I 3.414 B.t.u./hr.

1.341 X 10-3 H.P.

coulomb

volt

ohm

Siemens

C

V Ω

S

A s

kg m 2 s - 3 A -1

kg m 2 s - 3 A- 2

s'! A2 kg- 1 m-2

—

JA-1 s - l

VA-1

AV-1

Ω-1

Clean Air / August, 1973 59

tipliers for the S. I. system. It, should be noted that the units of time have not been decimalized, and the minute, hour and day remain with their traditional multipliers of 60 and 24. There are 86,400 sec. in & day. Table 2 gives the basic and derived units commonly used in the S. I. system, and some of the most important con­versions to traditional units. Table 3 lists some of the secondary measures commonly used, and Table 4 the special combinations of units in fre­quent use by air pollution control en­gineers and scientists. Some conver­sions from traditional to S. I. units are given in Table 5.

All of the industrial nations in the world have either been metric for some generations, have commenced metrication, or are about to do so. Even the United States, which for a time was the only major industrial country contemplating staying with traditional units, has now decided to go over to S. I. units.

It is interesting to note that a decimal system, based on the earth as a fundamental unit, was first sug­gested in 1670 by Gabriel Mouton, a vicar of Lyons. The French Revolution was a period of change, during which the metric system of weights and measures was introduced. This was detailed in the French legislation of 1795, and confirmed by decree on the 19th Frimaine, in the eighth year, otherwise the 10th December 1799, under Napoleon.

. The basic unit of the metric system was the length of 1 metre, represent­ing, as suggested by the vicar of Lyon, one ten millionth of the quadrant of the circumference of the earth. The length, or rather a section of the arc, was based on a special survey by two French surveyors, Delambre and Mechain, who surveyed the meridian running through Barcelona in the south, to Dunkirk in the north in the years following 1791.

There was, however, strong pre­judice against the new metric system in France, and another decree under Napoleon re-established the old scheme of French weights and meas­ures in 1812. This was withdrawn only 25 years later. Other European coun­tries were slow to follow the road to metrication. For example, the German states only abandoned their old syst­ems, which varied from state to state, seven years after the formation of the Empire, by decree of the Federal par­liament in 1877. This decree followed the Metric Convention Treaty of 1875 to which 18 countries were signatories.

In England, uniform weights and measures were decided upon as part (Chapter 35) of the Magna Carta in 1215. It is this uniformity which prob­ably relieved the pressure towards metrication in the 19th century, although the use of metric weights

Table 3.

Unit of

Area

Volume

Density

Dynamic Viscosity

Kinematic Viscosity

Abbreviation

square metre m2

cubic metre

kilogram per cubic metre

pascal second

square metre per second

m3

kg m-3

Pas (or N s m 2 )

m 2 s - 1

Secondary Units

Conversion into

cm2

mm2

f t 2

yd2

1 ft.3 U.S. barrels (o i l )

in.3 galls (Imp.) galls (U.S.)

g cm - 3

Ibf t -3

lb in-3

Poise

kg f.s m-2

Ib f .s f t - 2

stoke ( m 2 s -1) f t2 hr-l

Multiply by

104

106

10.764 1.196

103

35.31 6.29 6.102 X 104

220 264

10 -3

0.06243

3.613 X 10-5

10 0.1020 0.02088

10^ 3.875 X 104

and measures in contracts became legal in 1864, and the metric system as a whole was legalized by act of par­liament in 1897.

The United States, following the advice of Thomas Jefferson, toyed with a decimal system developed by Jefferson in 1791. Thirty years later, another future president, John Quincy Adams, recommended metrication after the French system to Congress. However, although the United States has permitted metric measures since 1864, and was a member of the Metric Convention of 1875, it has not yet taken the final steps towards metric­ation.

Many experienced engineers will find the conversion difficult, as for a

time they will lose the "feel" for reasonable quantities, whether they be temperatures, gas flow rates or pollutant concentrations. Nonetheless the effort at complete conversion will have to be made soon, or we will not be able to follow designs and develop­ments made elsewhere in the world or even in our own country.

Acknowledgement:

The author would like to thank Mr. J. N. O'Heare of the S.E.C.V. and Mr. G. Pratt of the Department of Industrial Science for their careful checking of the tables and helpful comments.

W. STRAUSS (Table 5 on page 63)

60 Clean Air / August, 1973

Table 4.

Unit of

Concentration

Volume Flow

Velocity

(flows through Filters)

Deposition (based on 30 day month)

Special Units

Abbreviation

kg/m 3

g/m 3

mg/m 3

m3 s-1

m 3 /min m 3 /h r

m s-1

m/min

m/hr

mg m-2

(day) - 1

Conversion to

lb / f t 3

grains/ft3

grains/ft3

ppm

f t 3 / s f t 3 / m i n

f t 3 / h r f t 3 / m i n

f t /s f t /m in

f t /m in ft/sec

f t /m in

tons/mile2 month

(30 day month)

Multiply by

0.06243 0.437

0.000437 22.41 / M *

35.3 35.3

35.3 0.5883

3.2808

196.85

3.2808

0.05468

0.05468

0.0765

* M = molecular weight

AIR POLLUTION RESEARCH IN AUSTRALIA & NEW ZEALAND

This journal published a review of research in these countries in 1970, and besides some projects in the Commonwealth Scientific and Indust­rial Research Organization, four universities out of 21 reported some work in air pollution. Since then there has been a tremendous increase of interest in our environment, and this is reflected in the research in the Universities and C.S.I.R.O. Now 15 universities report some projects in this area, besides a greater number of projects in different C.S.I.R.O. divisions. In addition two Universities have had specialist courses at the graduate level since 1971, and at least one further course is starting in 1973.

This review is a result of a request for information sent to heads of departments of physical and biological sciences and engineering in univer­sities throughout Australia and New Zealand. It will, unfortunately, due to oversight and omission, not be com­plete. Those whose projects have been omitted could write to the editor of this journal for inclusion in future reports.

It is felt that such a report is use­ful because it assists those working in the field in avoiding duplication of effort. Furthermore, it enables them to find out who is studying a related field, and it can lead to useful contacts. UNIVERSITY OF ADELAIDE Department of Physics Theoretical studies of diffusion of pollutants in a f luid medium H. S. Green Aerosols in the Troposphere W. G. Elford A high powered pulsed laser is being used to study aerosols in the tropo­sphere and stratosphere. Observations are being carried on over the city of Adelaide and both man made and natural aerosols are being detected. UNIVERSITY OF AUCKLAND Department of Chemistry Biochemistry of Plant Damage by Air Pollutants J. Spedding Investigation of the damage caused by SO* and O, is being investigated using "CO. as a tracer for metabolic pathways involving COs. The Uptake of Gases by Vegetation J. Spedding

The uptake of SO., H,S and hydro­carbons is being studied using radio­active gases as tracersd). Air Pollutant Gas Exchange with Water J. Spedding The solubility and kinetics of gaseous exchange in aqueous solutions is being undertaken to determine the role of atmospheric water and the oceans as sinks for pollutant gases. Atmospheric SO* Oxidation J. Spedding A study of the role of SOa oxidation in the aqueous phase in the atmosphere in relation to the concentration of sulphate from anthropogenic sources is being carried out to test the validity of some theoretical models. Department of Physics A Study of Air Pollution over Auckland A study has been undertaken using optical long path techniques. Measurement of Meteorological Parameters This study has been undertaken in order to derive an "air pollution potential index" which will provide a prediction of the proneness of a given region to air pollution. A Study of Antarctic Dust A study will be made in 1974 of dust concentration and size distribution in the Antarctic. It is also intended to study the electrical effects of blowing dust. AUSTRALIAN NATIONAL UNIVERSITY School of General Studies Department of Chemistry Measurement of Urban Air Pollution N. Daly and P. Steele The air pollution levels at the Civic Centre, Canberra, were measured. It was found that the levels during the day exhibit the same characteristics as those in high traffic flow areas in Detroit and Los Angeles. UNIVERSITY OF CANTERBURY Department of Chemical Engineering Urban Air Pollution A. M. Kennedy and N. J. Peet Clean air zones will be established in Christehurch under newly-passed legislation. Technical, social and econ­omic factors will be involved in eliminating the main cause of visible

pollution — the domestic coal-fire — and replacing it with alternative forms of heating. Detailed surveys of fuel and energy usage and pollutant emissions have been carried out for the period 1966-1971. These, coupled with household surveys, meteoro­logical and analytical information, will be used to provide a basis for guiding those concerned with imple-plementing the clean-air legislation. Activated Carbons N. J. Peet Preparation and testing of carbons produced from New Zealand coals and other sources. The work will involve laboratory-scale preparations, deter­mination of surface areas and pore sizes, and optimisation of preparation methods. Initially, the work will be aimed at producing carbons suitable for catalytic oxidation of SOa to S03. Desulphurisation of Flue Gas N. J. Peet Improvement and testing of a small-scale unit, capable of treating the gas from combustion of a sulphur-con­taining oil. The unit will use an active carbon type of catalyst for oxidation of S02 to S03 which is then removed by washing with water. Sulphur Isotope Ratios in Air and Flue Gases J. B. Stott There is some interest in determining the source of sulphur oxides pollution in Christehurch air. The Nuclear Science Laboratories at Gracefield have agreed to analyse sulphate sam­ples which we collect and suitable absorption apparatus has to be built and operated to do this. Cyclone Separation of Dusts from Gases J. Abrahamson An experimental study is in progress to investigate the causes of bin blow-back in multi-cyclone installations. MACQUARIE UNIVERSITY School of Earth Sciences One Dimensional Model of Atmospheric Processes R. Badham and E. T. Linacre A detailed one dimensional model of atmospheric processes affecting the nocturnal temperature profile has been developed and supplemented by a simpler version. This will be able to predict mixing layer depths from the minimum of forecastable ground based measurements.

Clean Air / August, 1973

Measurement of Inversion Characteristics using Mode! Aeroplanes R. Badhani and E. T. Linacre Flights using model aeroplanes have provided measurements of temper­atures at different places in New South Wales, in particular over a wheat field with weil instrumented ground conditions. This has permitted the checking of a model for inver­sions, with emphasis on growth and dissipation. Notable is the observation of a tightning of the inversion before break-up. This technique is being extended to the measurement of radi­ation divergence. Frequency and Character of Inversions from Thermohydrographs B. Richardson and E. T. Linacre An array of thermohydrographs has been placed on the Blue Mountains scarp for measuring frequency and nature of inversions in the Hawkes-bury valley. Measurements have been made continuously over five months of winter, when conditions are most critical, and have been corroborated by radiosonde and model airplane soundings. A complication has been the non-linear temperature profile. Temperature profiles using Radiosondes and Tethered Balloons C. Edgar and E. T. Linacre Fifty radiosondes have been modified for their use in Australia, and the possibility of making them recover­able has been investigated. They will be used for spatial distribution of in­versions. As these are unlikely to be permitted over the city, tethered balloons, carrying a radiosonde may be used. Equipment has been devel­oped for recording the sensor tem­perature automatically on the ground, the tether length and angle (for height). This will be used in the Par-ramatta valley for routine measure­ments. Development of a Flicker Thermometer E. T. Linacre and C. Edgar A flicker thermometer has been developed for use on relatively inac­cessible locations, not reached by cable. Here the time between light flashes is proportional to the temper­ature. A compact device has been developed for optical transmission of a signal for chart recording, which shows the difference between two points, say on a mast. This will be installed at Gladesville for measure­ments of conditions upward of Sydney. Meteorological Factors in Choice of Airport Sites B. Richardson and E. T. Linacre An attempt is being made to quantify the meteorological factors, together with those of land preparation, access,

etc. for a possible airport in the Hawkesbury valley. Sydney's Windfield C. A. McGrath, G. Hawke and E. T. Linacre Sydney's windfield has been examined in order to provide data on the ventil­ation of the city's pollution. This will provide input into a proposed com­puting model of the regional atmos­phere. This is being extended by the use of wind records from eleven ane­mometers around the city for the analysis of streamlines on various synoptic situations. Preliminary con­sideration has been given to a two-layer computer model of the windfield, including the disposition of hills and heat islands.

Effect of Pollution on Turbidity A. P. Campbell and E. T. Linacre A set of radiometers has been estab­lished with a recording arrangement for automatic measurement of global, diffuse and sky radiation, and duration of sunshine. These values will be compared with those measured in central Sydney. MONASH UNIVERSITY Department of Mechanical Engineering A Mathematical Model of Air Pollutant Dispersion D. Blackman and R. Joynt In the model developed, the pollutant is represented by fluid particles which move randomly to simulate the effect of atmospheric turbulence and are also advected in the mean wind field. The model can be adapted to a wide range of problems involving disper­sion in the atmosphere and has been used to calculate sulphur dioxide con­centrations in the Melbourne metro­politan area. Department of Chemistry An Attempt to Determine the Molecular Structure of PAN R. D. Brown Work has been in progress on this project for some time and there are still many problems to be solved. THE UNIVERSITY OF NEWCASTLE Department of Chemical Engineering Hydrodynamics of a Mobile Bed Scrubber B. Lancaster A study of the pressure drop charact­eristics of a co-current mobile bed scrubber. Sulphur Dioxide — Limestone Reaction Kinetics B. Lancaster The kinetics of the reactions of sul­phur dioxide with limestone which will occur in a coal fired fluidized bed boiler has been investigated.

The Reaction between Sulphur Dioxide and a Limestone Slurry B. Lancaster The reaction mechanisms which occur when a limestone slurry scrubber is used for scrubbing sulphur dioxide from flue gases has been studied. Department of Mechanical Engineering The department operates an air monitoring unit, and is particularly concerned with the measurement of atmospheric dust, haze, SO2 and CO levels. Oxides of nitrogen and ozone are also to be measured in the near future. A report was prepared last year for the Kooragang Island Pollu­tion Inquiry Committee by the head of the department, Professor A. J. Carmichael. Survey and Analysis of Air Pollution in Newcastle G. Y. O'Sachy An Investigation of Suspended Particulate Matter in the Atmosphere P. Phong-Anant Air Sampling and the Determination of Airborne Pollutants in the Newcastle Area K. C. Wong An Analysis of Dust Fall Out in the Newcastle Area Since 1962 L. W. B. Browne and G. Y. O'Sachy

UNIVERSITY OF OTAGO Department of Physics Vertical Movement of Eddies in the Atmosphere R. L. Closs An accoustic sounding system has been developed, from which it is hoped, by an analysis of phase and amplitude of sound scattered from the lower atmosphere, to obtain inform­ation on the vertical movement of eddies of warm air. Reliable data is being obtained, and with the incorp­oration of a two-phase lock-in amp­lifier, this will be a powerful tool for observing the formation and break up of the temperature inversions. UNIVERSITY OF QUEENSLAND Department of Economics A Linear Programming Approach to Regional Industrial Pollution Control S. Huxley A demonstration of the application of linear programming to the optimal composition and location of industry within a region where emission limits have been set. A method has been suggested for constructing a function of the opportunity/costs associated with pollution abatement. This func­tion can also be used for determining the optimal level of regional indust­rial pollution, and the allocation of pollution "rights among different firms.

62 Clean Air / August, 1973

An Economic Study of Air Pollution in Brisbane N. A. Tuan An attempt has been made to estimate economic costs of air pollution in the Brisbane region, and the cost of pollution abatement. Department of Chemical Engineering Population Limits by Thermal Pollution D. J. Nicklin and D. F. Martin An energy balance was set up on the earth's atmosphere to test whether man's increasing energy production could lead to global effects. It can be predicted that if energy production reaches a certain level, a significant rise in the average sea-land temper­ature will result, and thus limits to population at a given level of indust­rialization are set. A Gas Scrubber with a Contacter Containing a Fluidized Floating Bed K. O'Neill, D. J. Nicklin, N. J. Morgan and L. S. Leung A gas liquid scrubber has been suc­cessfully tested where the packing consists of a fluidized bed of solid plastic balls. This scrubber also in­volves several changes in the direction of the gas stream, so that co-current as well as counter-current flow is achieved. UNIVERSITY OF TASMANIA Department of Chemistry Mercury vapour in the Atmosphere H. Bloom Air is being sampled in the industrial areas around Hobart, using a gold trap for absorption. Mercury vapour levels in the atmosphere are being determined over a long time period. Pollution by Motor Car Exhausts H. Bloom Experiments are being carried out on the composition of exhaust gases from motor vehicles to determine the effects of methanol on a non-leaded petrol relating to the diminution of concent­rations of carbon monoxide, nitrogen oxides and unburnt hydrocarbons. Three engines have been set up, in­cluding one with fuel injection, where the exhaust gases can be sampled and analyzed by both conventional methods and by mass spectrometry. VICTORIA UNIVERSITY OF WELLINGTON Chemistry Department Carbon Dioxide Content of the Wellington Atmosphere Mr. Lowe A collaborative programme between the Institute of Nuclear Science, D.S.I.R. and the department has been carried out. It is primarily aimed at an understanding of the carbon dioxide equilibrium between the ocean and the atmosphere, and the effect of fossil fuel consumption.

To be continued.

The Old, the New and the Future in Air Pollution Instruments

(Continued from page 52)

of a permeation tube is quite simple; it consists of a short length of fluorinated ethylene-propylene cop­olymer (FEP Teflon) within which is sealed, by means of end plugs (also FEP), the substance of interest — for example, SO2 — in the liquid state. It has been shown that, at constant tem­perature, the contained substance, driven by its equilibrium vapor pres­sure, which in our SO2 example is about 3 atmospheres at room temper­

ature, will permeate outwardly through the teflon wall at a small but constant rate that can be precisely measured by determining weight loss as a function of time. It will be readily evident that such a known source, in combination with a metered stream of air flowing over the source, will supply a uniform mixture of the substance in air at a precisely known level, down to parts per billion. Such a precisely known mixture is an obviously invaluable asset in studies of an analytical instrument under a variety of conditions. The revolution in air pollution instrumentation dates from the first availability of this simple device.

Clean Air / August, 1973 63

S.I. Units and the Air Pollution Engineer

Table S.

Quantity

ft ins miles ft/sec f t /m in ft3 /sec f t 3 /m in Imp gall/min

pounds ounces

grains lbs/ft3

grains/ft3

lb/sec Ib/min Ib/hr f t2

yd2

ft3

Imp. galls

lb ( f ) / i n 2

atm. in. W.G. in. mercury mm mercury

Poise lb f.sec/ft2

kg f.sec/m2

Stoke (cm/s) f t 2 / h r

ft2/sec

B.t.u. therm kWh calorie f t l b ( f ) / s e c

horse power B.t.u./lb. B.t.u./ft3

B.t.u./Ib°F B.t.u./ft2 hr tons/mile2 month

(Continued from page 60)

Conversions of Conventional to S. 1. Unit!

Multiply by

0.3048 2.54 X lO-2

1.409 X 103

0.3048 5.08 X 10-3

28.32 X 10-3

0.472 X 10":l

75.77 X 10-*

0.4536 28.35 X 10"3

64.8 X 10-* 16.02 2.29

0.4536 7.56 X 10-3

126.0 X 10-* 92.9 X 10-'3

0.836

28.317 X TO"3

4.546

6.895 X 103

101.3 X 103

249.1

3.386 X 103

133.3 lO-'

47.88 9.807

10-4 25.81 X 10-'

92.90 X 10-3

1.055 X 103

105.5 X 10 '

3.60 X 10* 4.1868 1.356

745.7 2.326 X 103

37.21 X 103

4.187 X lO3

3.155 13.077

to obtain S.I. unit

metres (m)

metres (m) metres (m) Metres/sec (m s_l )

Metres/sec (m s"1

m3 s"' m3 s-' m3 s-'

kilogrammes (kg)

kilogrammes (kg) kilogrammes (kg) kg n r 3

g m - 3

kgs-l kgs-l kgs-l

m2

m 2

m3

m3

Pa, (Nm-2) Pa, (Nm-2)

Pa, (Nm-2) Pa, (Nm-2) Pa, (Nm-2) Pa, (Nsm-2)

Pa, (Nsm-2) Pa, (Nsm-2) m 2 s- l

m 2 s- l

m2 s"'

J J J J W

W Jkg-I

J m-3

Jkg-I K-l W m - 2

mg nr 2 (day)-1

FORTHCOMING CONFERENCES

1975 International Ciean Air Conference

The 1975 International Clean Air Con­ference is being held at Rotorua, New Zealand, from 17th to 21st Feb­ruary, 1975. The first four days will be the technical and general sessions, while the last day will be devoted to visits to the large paper mills in the area.

Two special technical sessions will be devoted to "air pollution from natural sources, such as geothermal areas" and "pollution control of the forestry industry," while others will be concerned with the many other aspects of air pollution, from urban planning to monitoring and control.

The programme sub-committee consists of Dr. Rogers (Chairman), Mr. A. W. Skam (Secretary), and two other members of the New Zealand Branch Committee. The Committee is inviting comments and suggestions from Society members for topics that should be covered, and it will shortly be issuing a formal call for papers. These suggestions should be sent to Mr. Skam, P.O. Box 2225, Auckland, New Zealand.

Symposium on Laser Technology

The Ian Clunes Ross Memorial Found­ation is holding a symposium on Laser Technology at the National Science Centre, Parkville, Melbourne, 3-5 October 1973. The Symposium will not only present papers on the basic principles of laser technology, and its applications, but will consider what current research promises for laser applications in the future. In addition to the formal papers, the third day will be devoted to demonstrations of a wide variety of current laser applic­ations.

Contributions are still being in­vited, particularly on detailed techno­logical advancement in the field of environmental studies. Persons inter­ested in either attending, presenting papers or demonstrating should write to The Secretary, Ian Clunies Ross Memorial Foundation, 191 Royal Parade, Parkville, 3052.

Ambient Air Monitoring Programme

Results from the ambient air monitoring programme which has been established in Victoria were made available to the media for the first time on Monday, 23rd July 1973. Results are given for the 8 a.m. to

9 a.m. and 2 p.m. to 3 p.m. hourly average on the following parameters: oxidants, oxides of nitrogen, nitric oxides, nitrogen dioxide, ozone, local visual distance.

The Authority intends to increase the number of parameters being measured to include sulphur dioxide, hydrocarbon, particulates, carbon dioxide, wind speed and direction and relative humidity. All results will be data logged and transposed to the computer monthly. The information will be available to all interested parties and will be used for trend analysis, acorrelation analysis and in the current programme on oxidants and their precursors as well as evalu­ating the efficiency of the waste man­agement programme which is now in full operation.

Initially two complete mobile stations will be used in conjunction with one fixed station. The present aim is to have five fixed stations.

This is the first time in Australia that comprehensive monitoring in­formation has been made available to the news media on the same day by a government instrumentality.

P. LeROY Chief Air Quality Officer

In the Federal Sphere

Dr. Moss Cass, the Federal Minister for the Environment and Conservation, has announced the setting up of a National Bureau for Environmental Studies. This department also has a proposal for a parks and wildlife service for the Federal territories. The government also hopes to implement a survey of Australia's biological re­sources. It has also been indicated that "Impact Statements" will, in future be required in certain circum­stances for new activities on land controlled by the Federal Government.

The Attorney-General, Senator Murphy, has announced that an "Environmental and Administrative Law Branch" will be established in his department, which will be con­cerned with the "development of en­vironmental law as well as general administrative law matters." Officers of this department had already been appointed to assume special respon­sibilities concerning legal matters relating to the environment, and some have had talks overseas aimed at pro­viding a guide to action that the Aust­ralian Government might take to pro­tect the environment through law. "As the Government formulates de­tails of its policy, other proposals for legislation to ensure that Australia's environment is protected will be announced. This legislation will form the basis of a comprehensive national environmental legal code."

On the last day of the Autumn session of the House of Represent­atives, it established a standing com­mittee to deal with environmental and conservation matters. Its members are Mr. J. W. Bourchier (L. Vic), Mr. E. M. C. Fox (L. Vic)., Mr. J. C. Kerin (ALP, N.S.W.), Mr. A. H. Lamb (ALP, Vic), Mr. I. L. Robinson (CP, N.S.W.), and Mr. R. H.. Sherry (ALP, Tas.). It will be chaired by Dr. H. A. Jenkins (ALP, Vic), The terms of reference of the Committee are to enquire and report on —

(a) environmental aspects of legis­lative and administrative measures which ought to be taken in order to ensure the wise and effective man­agement of the Australian environ­ment and Australia's natural re­sources; and

(b) such other matters relating to the environment and conservation and the management of Australia's natural resources as are referred to it by the Minister for the Environment or resolution of the House.

The Committee is to recognize the responsibility of the States in these matters, and to seek their co-oper­ation in all relevant aspects. The Committee also has powers to consult with a similar Committee of the Senate. (Originally a joint committee of the two Houses was proposed, but this was dropped because of the difficulty that the Senate would have had in supplying members because of the requirements of its own committee system).

Standards Association of Aust. -Conference on Air Quality

A meeting attended by about 30 delegates, representing a large number of organizations in the field of en­vironment and pollution control took place in Sydney on 2nd May, 1973. The meeting was chaired by Dr. E. C. Potter of the C.S.I.R.O. Division of Mineral Chemistry.

The delegates discussed the pro­posed programme of work by the International Organization for Stand­ardization, Technical Committee ISO/ TC 146 "Air Quality." This concerns general aspects of air quality, and the methods of separation, measurement and analysis of particulate matter, gases and vapours.

The motion that "the S.A.A. seek participant membership of ISO/TC 146" was passed.

The programme of work to be undertaken is essentially that out­lined in the TC 146, and a committee is to be set up by the S.A.A. of repre­sentative organizations, which in­cludes the Clean Air Society, among 17 other organizations.

64 Clean Air / August, 1973

BOOK REVIEWS

"The Stockholm Conference — O n l y O n e Ear th " An in t roduc t ion to t he pol i t ics of survival . Friends of the Earth Earth Island Ltd., London, 1972. Distributed by Angus & Robertson Ltd. 175 pp L Australian Price $1_.50.

To the reviewer's surprise, this book was issued before the Stockholm Con­ference, although it appeared to pre­sent evidence, conclusions and recom­mendations from the conference. Nonetheless the message is powerful; man is a species exploiting the envir­onment on which he relies by exter­mination of other species, denuding the countryside and polluting air, water and soil.

The "Friends of the Earth" feel that we are not only seriously deplet­ing earth's resources, but poisoning the planet. Our consumer society entices us to destroy goods before they have outlived their usefulness. Furthermore, there is a futility in sit­ting "in a ton or two of metal waiting in traffic jams." Thus, "if you are not part of the solution, you are part of the problem."

Of course, above all, is the problem of numbers: "when you have finished reading this book (less than two hours) there will be 15,000 more people."

While the book is well prepared, the standard of illustrations is disap­pointing. The persuasive word pictures would have been better supported by colour photographs, than drab black and white illustrations of what we should be preserving.

As a digest of what is happening — a snapshot of changes in our ecology — this is a good book; it should now be followed by another, telling us what has happened as a result of the 1972 Stockholm Confer­ence.

L. H. PYKE

Proceedings of t h e Second In ternat iona l Clean A i r Congress ed. by H. M. England and W. T. Beery Academic Press, New York, 1972 1354 pp. (1971) $85.00 Available in Australia through Book and Film Services, P.O. Box 226, Artarmon, N.S.W. 2064 __

This gives, In one volume, all the papers delivered at the IUPPA Con­gress in Washington in December 1970. Over 250 papers have been kept within the manageable bounds of a

single volume, and the editors must be congratulated on this, as they have managed to retain a, clear style of presentation. The papers have been divided into sections designated as follows: surveys, medicine and biology, chemistry and physics, engineering, meteorology and administration. Reports from IUAPPA member organizations and from inter­national organizations conclude the

volume. At the time of the congress, the

papers delivered presented the most-important "state of the art" reviews available, and so this volume is a most important work of reference. Its price, unfortunately, places it beyond the individual, but no library serving those working in air pollution, or environment protection can afford to to be without it. W. STRAUSS

Clean Air / August, 1973

Lead can be lethal Lead is great . . . . until you eat it. Then it is a dangerous,

cumulative poison. But Varian Techtron keeps an eye on it for us. With an atomic absorption spectrophotometer.

Too much lead in the system from a polluted river or a carelessly coated can . . . it can be as lethal as a dose from a 45. But an Australian team of scientists at Varian Techron has progressively developed an analytical instrument called an atomic absorption spectrophotometer (for detecting atoms not splitting them) to discover lead traces before you are booked for Boot Hill. This Melbourne company, Varian Techtron, the world's second largest manufacturer of atomic absorption spectrophotometers, is out there watching over pollution for us. It's nice to know someone is. And even nicer to know they're Australians.

Clean Air / August, 1973

If you are employing the most efficient apparatus available, then you will be enjoying the advantages of the

Airf low BCURA or M k l l l A dust sampling equipment. Both these instruments conform to the requirements

of the British Standard 3405 : 1971 and are described in Appendix A of this publication, "Measurement of Grit

and Dust Emission."

BCURA Dust Sampling Equipment (Component parts in their carrying cases shown at r ight).

Features

Compact — occupies little space during transit or storage.

Simple to operate — the cyclone itself is used as a flowmeter.

High temperature operation — the cyclone probe (without fi l ter) may be used up to temperatures of 650°C or more.

M k l l l A Flue Gas Dust Sampler

M k l l l A features a polypropylene tube which provides long term accuracy with little maintenance.

For further information contact —

H. B. SELBY & Co. PTY. LTD

MELBOURNE, SYDNEY, BRISBANE PERTH, ADELAIDE, HOBART

environmental information

mailing list ramsays scientific book department maintains an environmental information mailing list. If you

would like to receive any regular bulletins detailing newly published books in your interest

area simply cut out this advertisement and return it to MISS ANNE LINDSAY C/- RAMSAY'S

DIRECT MAIL OFFICE, 182-206 BERKELEY ST., CARLTON 3053.

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Clean Air / August, 1973 Cover iii