1360_ch09

chapter 9

Working program toward a first implementation

Following approval by corporate management to proceed on the basis of thepreliminary process design and economic estimate (the green light, seeChapter 8, Section 8.8), the work program will expand considerably and willrequire a larger number of professionals, organized in several differentgroups and possibly in different locations. The core team, which will workwith the project manager at the center of the campaign, will also have to beconsolidated at this point.

This chapter deals with those parts of the working program that can bedone in parallel and handled as separate jobs, with proper directives,under the direct coordination of the project manager. Chapter 10 will beconcerned with the consolidation of all the results from these different jobsinto a single, final plant design.

9.1 Patent protection

9.1.1 Revised or additional applications

Following the experimental program and further conceptual shaping in thepreliminary process design, one should ask: if we knew at the time of thefirst application what we know at this present stage, how would we formu-late the patents claims?

In many cases, analysis of the results from the experimental programmay point out specific features, or particular ranges of variables, that appearat this stage to be clearly essential for successful and profitable implemen-tation, which were not obvious from the start, even to a person versed inthe art (in the patents archaic jargon). The patent should therefore bereviewed in order to determine if any of the claims included in the firstapplication should be changed, or new claims added. The senior project staffwill now examine with the patent experts whether:

1360_frame_C09 Page 143 Monday, April 29, 2002 3:38 PM

Copyright 2002 by CRC Press LLC

Such

specific novel aspects

can be presented convincingly as

discov-eries that are essential

to practical industrial implementation and,if so,

What is the

best procedure and timing

for preparing and submittingrevised or additional applications to cover these specific novelaspects?

Separate applications are often recommended to increase the legal protectionfrom different angles, but these additional applications also require invest-ment of time and some significant expense (see below).

The conclusions of this review should probably also be relevant withinthe terms of the contractual agreement between the inventors/promotersand the implementing corporation (see Chapter 8, Section 8.9). These gen-erally define the nature and extent of the intellectual rights for whichexclusive licensing should be provided in the contract, including any patentassigned by the inventors to the corporation, and (most important!) theoption for the corporation to award recognition for substantial contribu-tions, by adding other names to the list of inventors, in the revised oradditional applications.

9.1.2 Extended geographical coverage of the patents

The procedure of the international Patent Cooperation Treaty PCT allows a patent applied for in one location, on approval, to be filed in anyone of 70 to 80 different countries with no further examination. However,the extent and locations of additional filing have to be decided within a relatively short time after the PCT approval, and filing in each country cancost up to thousands of dollars in registration, attorneys fees, translation,and other similar expenses. This cumulative cost is for every separate appli-cation, so that the decision to file many separate applications in many dif-ferent countries can become very costly.

9.2 Detailed process design 9.2.1 Piping and Instrumentation Diagrams

The process engineering team will now prepare, with the active participationof the engineering companys staff, revision 0 of the P&ID drawings. Whenready, these drawings will then be distributed to all members of the projectteam and consultants, for their review and comments. These drawings willbe

revised several times in the future

, as more detailed information and com-ments become available, until they are finalized as approved for construc-tion. These P&ID drawings, as can be seen in typical examples in Figures9.1, 9.2, and 9.3, include all major and secondary equipment items, with theirformal names, tag-numbers, and main specifications, as also collected in theequipment list.



The major equipment items have already been defined and charac-terized in the preliminary process design (see Chapter 7, Section 7.8)and are further discussed in Section 9.3 below.

The secondary equipment items are those that can be selected fromstandard models found in suppliers catalogs. This selection or rec-ommendation is generally made by the sales engineers or specialistsfrom suppliers, in response to specification sheets prepared by theengineering company. These equipment items consist mostly ofpumps, fans, compressors, standard heat exchangers, solid handlingequipment (conveyors, elevators), agitators, and so like.

In addition, in a new process, there may be some equipment items thatcannot be attributed from the start to either group. For instance, aparticular heat exchanger duty could present unusual features (suchas in the flow conditions, in some safety hazards, in the possibility offouling, or in feed-back control) and thus a thorough discussion isneeded with the potential suppliers, before a choice can be made be-tween a standard model or a special modification. Similarly, the choiceof certain pumps can be critical in particular situations, if a normalleakage of a process stream could become a safety issue or if solidscould accidentally find their way into the stream. The impeller of anagitator may have to be specially redesigned in order to avoid thecreation of emulsions in certain liquidliquid mixing operations.

9.2.1.1 Piping lists

These lists include all the piping lines with their standard diameter andschedule (wall thickness), material of construction, and tag-numbers. Apiping line is defined and tagged as it connects one piece of equipment toanother. If thermal insulation of the piping line is needed, its thickness isalso noted at this point. The pipe diameters are calculated from the materialbalances tables, including a chosen reserve, and from acceptable linevelocities (which can be quite arbitrary), and rounded to the next upperstandard diameter (that can also add a significant reserve!).

The routine specification/sizing of piping in a conventional plant designis generally processed automatically by technicians, but for a new processwhere different unknown factors could be relevant, the process engineer-ing staff should review these piping specifications carefully and repeatedly.This task may seem trivial, but many of the problems in start-up can gener-ally be traced back to an error-of- judgment in piping specification.

Any change in the piping in an operating plant can be very complicated.Therefore, greater care should be devoted to those added reserves for anew process, to allow for the possible increase in some flow-rates during theplants start-up, to solve unexpected problems, to arrive at process optimi-zation, and for the eventual increase of production after de-bottlenecking.Note that the added cost to increase the size of small diameter piping isgenerally insignificant.



However, in certain cases, a larger diameter may be counterproductive.For example, in pipes handling streams that may contain solids, a decreasein the stream velocity could induce their settling and accumulation incertain parts.

9.2.1.2 Valves

All the valves needed for different functions are listed and tag-numbered,each with its location, standard, material, and size. The types of functions are:

On-off for complete opening or closing of the flow, leaving the pipeupstream full of the process stream. Is this acceptable process-wise?Not always.

Throttling to impose a back-pressure and reduce the flow-rate. Dif-ferent types are available for specific stream characteristics, i.e., theexpected degree of erosion. How to choose the best model?

By-pass: a set of three on-off valves that allow the flow to be detouredfrom its normal route, through a particular piece of equipment.

Drain: on-off valve at the lowest point of a piece of equipment or apipe. Does it open directly into the open air or into a draining pipe?Could solids clog it, and in such cases, would a flush-back washingarrangement be needed? Would there be a hazard if some leakagedid occur?

Venting: on-off valve at the highest point of a piece of equipment ora pipe. Is it open directly to the atmosphere or into a venting pipe?Would a leakage present a safety hazard?

Sampling: specially designed on-off valve, to remove samples forinspection or analysis, while avoiding any dead space between therunning stream and the outlet, or providing a flush-back arrangementto arrive at the current material.

Flushing: certain pipes need flushing with water to prevent accumu-lation of solids.

In a new plant with a novel process, more valves are generally provided

thanfor a conventional process, to allow for more flexibility, for easier inspectionand cleaning (i.e., if solid precipitation could occur), and for the extensivecollection of data during start-up and optimization. This is important inparticular for the flushing and sampling valves.

9.2.1.3 Instruments

All the

instruments for local indication

and for the

control loops

are marked andtagged on the P&ID drawings, then listed according to their expected basicprocess duty. Their functional scope and general policy are agreed withinthe core team, before transmission to the detailed engineering. In this rapidlychanging technological field, the specification sheets and the final choice ofthese instruments have to be done by specialists, updated with the latest



developments, and with the feedback comments from users. This choice isgenerally done in personal meetings between a process engineer and aninstrumentation designer from the engineering company and the sales spe-cialist from the supplier.

In a new plant with a novel process, a much larger number of local instrumentsare installed

to allow for initial calibration, collection and checking of indi-cating data during the optimization stage, together with some degree ofcross-checking on important points. These extra local indicators will beremoved eventually, when the production is stabilized and there is no needfor them anymore.

9.2.1.4 Control loops

Control loops, with their standard definition and control valves, are essen-tial to control flow-rates, liquid levels, stream temperatures, pressures,pH, or other analytical features. The further integration of these controlloops into the computerized control system is discussed further in Section9.6.4 below. The selection of the hardware equipment is similar to theprevious section.

9.2.1.5 Flanged manholes and hand-holes in closed pieces of equipment

These openings are needed in any plant, for inspection and cleaning of theinterior or access to carry out adjustments or modifications, without havingto dismantle the piping and instruments connections or the drive and upperconnections. It is always advantageous to have more of these openings, butthey add significantly to the installation cost, and they can eventually causetrouble, by leaking out process streams or leaking in air.

In a new plant with a novel process, a much larger number of flangedmanholes and hand-holes are generally designed than in a conventionalprocess, to allow for better inspection during start-up and optimization andeventually, for handling of unexpected situations.

9.2.1.6 Provisions for possible future connections

Since changes in the piping of an operating plant are always very compli-cated, it is a good practice to design and provide certain connection points(flanged nozzles in the equipment and flanged tees in the piping), so thatpiping additions can be hooked up with only brief interruption. In a newplant with a novel process, a much larger number of such provisions isworthwhile, to allow for more flexibility in optimization and de-bottleneck-ing. Their extra physical cost is very small compared to the possible gains.It is important, however, that their locations be very carefully plannedaccording to likely scenarios.

Another use for these extra nozzles in a new plant with a novel processhas often been to unplug solid deposits in certain lines that often appear,sometimes with no clear cause, and have to be dealt with.



9.2.1.7 Non-conventional drives

Non-conventional drives are also marked on these drawings. Although gen-erally, the electric motor drive is not tagged separately but considered aspart of the equipment, certain motors are different. The special process dutyof such drives could be specified as: variable-speed, high-torque, withfeed-back control, or direct steam turbine, etc. If certain electrical drivesneed to be connected also to an emergency electrical supply, this is empha-sized on the P&ID drawings and on the lists.

Lists of all equipment items, piping lines, instruments, control loops,and electric drives are prepared in a suitable format (revision 0), in additionto the P&ID drawings. These spreadsheets will be used and revised furtherin all the detailed engineering work.

9.2.2 Examples of portions of piping and instrumentation drawings

The following three typical examples are given to illustrate that certain verysimple process concepts, which are almost taken for granted, can becomequite complicated to design and operate in the plant, and require carefulattention to many details to be applied successfully.

Figure 9.1 illustrates a very simple statement in a process description:the overflow (stream 6507) from stage 1 is cooled to 45

C and transferredto stage 2. In the plant, this statement translates into three pieces of equip-ment and three control loops, plus pipes and valves and local instruments.Of course, most chemical engineers know this but quite a few process devel-opers have no definite idea of the translation of such a simple statement(the engineers will take care of that). This means that the overflow processstream PI-6507 is collected in a buffer tank TK-1054 and pumped by P-1054

Figure 9.1

P&ID example of overflow cooling and transfer duty.

LT06

FEM09

TT08

TC08

TY08

TV08

FV09

FY09

FT09

FC09

LC06

TT07

TI07 1"

2"

2"

TK-1054

3"-N-43678"-V-4320

6'-PI-6507

P-1054

CoolerE-1054

3"-CWS

3"-CWR

3"-PI-6508



through a plate heat exchanger E-1054. The flow is measured by FEM-09and the liquid level in TK-1054 is kept constant at a desired level by LC-06,which cascades on FC-09, which operates the control valve FV-09 on theoutgoing stream to stage 2. The temperature is monitored in TK-1054 by TI-07 and the final cooler temperature is measured and controlled by TC-08,through the control valve TV-08 on the return flow of the cooling watercircuit. Of course, TK-1054 has to be vented and (in this particular process)kept under nitrogen blanketing. A bypass is provided for the process streamaround the plate heat exchanger to be able to continue operation whilemaintenance operations are done in this cooler. Sampling valves and otherstand-by valves are also provided.

Figure 9.2 represents a portion of a P&ID for a process making puredry hydrofluoric acid (HF), by distillation from an intermediate processstream containing HF, water, and a third component (needed to decreasethe vapor pressure of the water). In principle, this is a very simple strip-per/rectification column, with a reboiler, a condenser, and condensatereflux, and extensive physical data has been published on this system. Thebottom stream is recycled to the process backwards. But in fact, there arequite a few complications that require experienced decisions. First, theatmospheric boiling point of HF is about 20

C. Operating the condenser

Figure 9.2

P&ID example of a distillation section for dry HF.

P-101

P-102 P-103

TK-105

E-102

Refrig.systemHS-101

freon vapors

freonliquid

reflux

HF vapors

bottom to recycle

CWR

CWS

M

mixedsolution

HPS

D-101

to vent

to vent

to vent

productstorage

fromto

PI

LT LIC

TE

TRC

PCV

E-101

TE TRC

TE

TRC

TI

PIPI

TI

PC

PI



with cooling water would require maintaining the whole system underpressure and raising the temperature in the reboiler, thus requiring a veryhigh steam pressure and mostly very expensive materials of construction.This was ruled out and an operating pressure around atmospheric wasopted for; therefore, the condenser was designed with a

dedicated mechanicalrefrigeration unit

. The column is operated with a temperature gradient; itsupper section is kept quite cool by the reflux of cold HF, which serves alsoas a direct contact cooling medium, as a large part of the reflux is justevaporated and returned to the condenser. This means that the columncannot be operated, or

even started

, without a significant amount of reflux,and therefore

a stock of HF must always be kept in the receiver TK-105

to bridgetemporary interruptions in operation. After longer stoppages, HF may haveto be brought back from the product tank into TK-105 to restart this unit.

The ultimate irony is that this plant cannot be started for the first time withoutbuying some product from the competition!

Of course, the whole unit must beclose-vented and all the noncondensable gases sent back to the scrubbersoperating in another section of the plant. Thus the amount of instrumen-tation and control shown in Figure 9.2 is in fact only the starting minimumfor review, and careful designers may decide to add more means of oper-ational flexibility and safety. These problems are typical in many cases ofnew process design and development.

Figure 9.3 illustrates some typical complications that have to be takeninto account in the P&ID for such a simple operation like a thermal evapo-rator for large-scale preconcentration of a relatively diluted aqueous solutiongoing to crystallization. Significant amounts of water have to be evaporatedat the lowest cost. Mechanical recompression is generally one of the bestchoices in connection with a falling-film evaporator operating under vac-uum, which seems to be simple enough and there would be a number ofspecialized suppliers always eager to make an offer. In principle, the solutionis circulated and distributed as a film on the inner wall of the vertical tubes;it falls down while it is heated by the condensing steam in the chest outsidethe tubes; part of the water is evaporated, separated in a side vessel. Afterthat, the water vapors are compressed and sent into the chest. A centrifugalcompressor is generally the best choice for such duty (compression ratio),energy-wise. But such a compressor is very sensitive to the presence of solidparticles, or even liquid drops in the vapor, considering the very high shear-ing forces. Thus the vapors from the evaporation have to pass through aseries of treatments:

1. Separation from the main concentrated liquid, which may be froth-ing, into a side vessel.

2. Passed through a mesh entrainment separator, equipped with a peri-odical washing system, actuated by a differential pressure controller.

3. Mixed with recycled hotter vapors to dry any possible microscopicdroplets remaining, before entering the compressor. This recycle isset by a down-stream temperature controller.



4. After the compressor, the vapors are desuperheated by a spray ofcondensate water in excess, since for a change, such excess is notdetrimental.

5. Then, the make-up stream of low-pressure steam is mixed in. Therecould be different control schemes, according to the characteristicsof the system and the quality of the thermal insulation. The mixedvapors are distributed in the chest and flow downwards while con-densing on the tubes.

6. The chest is a closed vessel and any noncondensable gases presentwould accumulate and prevent further condensation. Thus thesegases have to be continuously removed by a side-vacuum system,under the control of a pressure-control system. The standard vacuumsystem requires a direct condenser stage, discharging through abarometric leg or hot well and a water-ring vacuum pump witha cold water stream.

Figure 9.3

P&ID example of a falling-film, vapor-recompression evaporator.

M

M

M

condensatefeed

hot well

coldwater

vacuum pump

condensate

concent.soln.

CW

DC

TI

TI

TI

TI

TIC

PE

PIC

PDI

compress.

LC

LIC

FR

LP steammakeup

TE

TI

PI

LE

LELE



7. The amount of noncondensable gases in a system under vacuumdepends mostly on leaks inward of air, due to faulty installation ormaintenance, and many plants experience difficulty as a result. Thus,an oversized vacuum system could help in many cases.

One can therefore see that the smooth operation of such a conceptuallysimple evaporator can depend on many detailed issues requiring decisions,and the developers cannot just relegate these details to the expertise of thesuppliers. Instead, they should at least understand exactly what is involvedin the new process. We have not discussed proprietary technology that everysupplier is claiming for himself such as, for instance, the exact distributionof the liquid films inside the tubes, the eventual cleaning of these tubes,various internal baffles and vapor routes, etc.

9.3 Major equipment packages

Major equipment packages are groups of equipment items that are pivotalin the plant and should be designed or procured together, in process-com-patible materials. These packages could be, for instance, a multiple-effectsevaporator, a distillation section, a crystallization system, or a mixers-settlersbattery for solvent extraction.

The preliminary process design gave a

functional analysis of the processrequirements

for this equipment package, as quantified in the material andheat balances, with a draft specification sheet and a list of potential suppliers(see Chapter 7, Section 7.8). Some of these suppliers have already beencontacted for the FCI estimate. At this stage, more extensive discussionsshould be conducted by the senior process team with each of these suppliers,preferably in face-to-face meetings, if this is possible, to explain the particularneeds of this project and to clarify the following aspects:

Which possible design options would these suppliers consider forthis particular case and what is their preference? Each option will bedetailed, with advantages and disadvantages.

What is the extent of their previous experience on similar projects?Are they willing to disclose details and allow direct contact withreferences?

Who are their designing experts and what is their theoretical back-ground, in particular for designing a first-plant case?

What process data is absolutely needed for their design? Do they have the piloting equipment and the staff to run the necessary

demonstration and optimization tests, which could be used in thisproject at their place or which could be shipped to another pilot site?

When these open discussions reach a more detailed stage, a mutuallybinding secrecy agreement will probably have to be signed. A good procedurewith suppliers is to cross-check their claims with independent consultants.



After the first round of discussions, a preferred supplier will usuallyemerge for each major equipment package, on the basis of the confidence,the cooperation and the facilities that they can provide. For a

critical

majorequipment package, the actual purchase cost is probably a secondary con-sideration of the project team, as long as it remains in the reasonable range(

although this fact of life will never be admitted openly!).

The proposed equipmentdescription and the numerical data obtained from this supplier will be usedto proceed with the engineering work at this stage. However, to maintainthe formal procedures and to retain a fallback option (in any case), thispreferred supplier will be generally included in a short-list of two or threeother possibilities, which will be maintained fully in the picture until thefinal bid is allocated. Such rules-of-the-game are generally well known toeveryone concerned in this field!

Apart from the packages, the configuration of some other majorequipment may have to be

specially developed (or more exactly modified)

anddesigned to obtain the particular performance duty that is specified forthe new process. The eventual cooperation of a specialized supplier, whois close enough to the desired technology, could be advantageous butit could also raise delicate issues concerning the future exclusivity andownership of this new know-how, once the actual plant results becomeavailable.

9.4 Pilot testing of specific process operations

Pilot testing of some process operations may be required to confirm detailedquantitative specifications for particular pieces of equipment items, whenthese operate with the exact streams of the new process. Examples are givenbelow.

9.4.1 Multiple-effects evaporator

The

basic design

of a multiple-effects evaporator for budgeting purposescould be based on bench-scale equilibrium data, but the reliable

detaileddesign

of an industrial installation will require the

experimental

determina-tion of certain quantitative factors that could be still unknown, such as,for instance:

What heat transfer coefficient can be obtained with different concen-trations of the solution (density, viscosity) and with different veloc-ities in the tubes, and what will remain from the heat exchangersperformance after a few hundred hours of operation and the resultingdeposits (coating) on the heat exchange surface?

What would be the possible effect of any noncondensable gases orsoluble impurities dissolved in the feed solution on the behavior ofthe solution boiling inside, such as frothing, splashing, precipitation,and possible encrustation of solids?



What would be the frequency, method, and ease of internal cleaningand how would that affect the average number of working hoursfor design?

What would be the external behavior of the concentrated solution,once it is removed from the evaporation conditions (depressuriza-tion, cooling)?

Furthermore, larger quantities of concentrated solution may be required fortesting of the downstream operations relative to this evaporator, such as acrystallizer, a flaker, a spray-dryer, and so on.

These requirements necessitate the

continuous operation of a pilot evapora-tor

, equipped with all the instrumentation for collecting the necessary data,while storing the resulting concentrated solution in suitable containers. Thetest period would be relatively long (a few weeks, for example) and sufficientquantities of the starting solution needed, of the actual composition or asclose as possible (with due reservations). Such piloting can be done in aspecialized R&D institute, or in cooperation with a potential equipmentsupplier, who could rent a portable pilot installation and operate it.

9.4.2 Liquidliquid contacting battery

Another example of a major package is a multiple-stage, counter-current,liquid-liquid contacting battery for a solvent-extraction process. For design-ing a horizontal battery of mixerssettlers, in which each stage is assumedto be practically at equilibrium, all the process aspects can be calculatedreliably from the results of bench-scale equilibrium tests, such as the numberof theoretical stages, the concentrations, the mass transfer rate in a mixedvessel, and the liquidliquid separation rate (see Chapter 6, Sections 6.2.3and 6.4.1). This choice of equipment was therefore popular for implementa-tion of new processes (Chapter 4, Reference 13) and it would probably stillbe the best choice for a small number of stages (say three to five).

However, when a larger number of stages is required, with larger flow-rates and more costly solvents, the option of a mixerssettlers battery couldpresent significant disadvantages as compared to a continuous vertical col-umn-contactor, or to a set of centrifugal extractors. These disadvantagescould be, for example, a bigger internal inventory of solvent, a larger hori-zontal area in the plants layout, the need for more intermediate pumps, andso on. These issues have been discussed extensively in international confer-ences and some recent papers relevant for industrial equipment are listed inthe references.

1114

Cusack et al.

11

presented the development of a new highcapacity column design from an analysis of previous models (Koch). Axialmixing in large-scale packed extractors is detailed in Reference 12. Lo

13

reported on an experimental comparison among three different existingmodels of columns, his conclusions for one particular case and the scale-upprocedures to be used for an industrial project. Movsowitz et al.

14

reportedon a rather exceptional case in which a uranium plant in Australia worked



for two years in two parallel lines, one with four mixers-settlers and thesecond with two Bateman columns and then it was decided to use (of course)more columns for their new expanded plant.

Several suppliers offer vertical columns/contactors, each with their ownproprietary design and know-how. None of these columns can be reliablysized without

extensive pilot testing for each case

with the

actual materials

, inorder to determine: acceptable velocities, height of a theoretical contact stage,behavior of the phases mixture (observations), starting procedure until asteady-state operation is reached, and so on. Therefore, each supplier isorganized with its own portable pilot installation and expert staff, which canbe hired by a prospective client to conduct such tests with his own materials,for process demonstration and equipment sizing. In many cases, the hiringfee for the pilot is deducted from the purchase price of the industrial equip-ment, if a deal is reached.

But for the process engineering group, the main issue before orderingsuch equipment for a novel process is to understand the internal mecha-nisms, which are generally not entirely published. For example, how theperformance is scaled-up and

what can be modified

if the results obtainedduring start-up are unsatisfactory?

9.4.3 Main problems for piloting

The above typical examples emphasize the two main problems related tothe piloting of specific process operations, from the point of view of theimplementing corporation:

The investment in a new, owned pilot would be expensive, requirein-house expertise and a relatively long time to start and, therefore,would be justified only for a long-term continuing R&D program inthis particular field. Otherwise, after the conclusion of these series oftests, this pilot installation could remain unused for a long time. Onthe other hand, these pilot tests could be possibly done in cooperationof a pre-selected supplier, as most suppliers of specialized equipmenthave their own pilot installations. However, such preselection couldimpose many formal limitations, which should be clear and accept-able from the beginning.

The procurement of a sufficient quantity of representative feed solu-tion may be difficult and may need to be produced in another pilot,according to the upstream operations (before the one under consid-eration). This condition may require a more comprehensive andlengthy program.

9.5 Modeling

The methodology and technique for the development of a dynamic mathe-matical model that can simulate a specific process have been occupying the



attention of the chemical engineering scientific community for the last twoor three decades, and have evolved rapidly with the advancement of com-puterized resources. This is one of the most popular (fashionable?) academicfields in chemical engineering faculties and many commercial programs arealso offered to the professionals. There are good textbooks and publicationsand there is therefore no need to recapitulate them here.

14

However, any such model can only be as good and accurate as the numer-

ical data in its data base and this weak point has discouraged many developersof novel processes. It is therefore important to recognize the importance andthe need for such a tool, by considering it a

long-term investment in the processdevelopment program

. Thus, the model can be started and run first on the basisof reasonable assumptions and the significance of the results can be studiedand understood. Then, after the first runs, a list should be prepared of certaindata with significant leverage, which should preferably be confirmed andcompleted by additional bench-scale tests (see Section 9.6.3 below). The modelwill therefore be

progressively improved

.A dynamic mathematical model, as the quantitative basis of this specific

process, will be used first for the important, but not critical, task of theengineering design of the instrumentation and control systems and for deci-sions concerning the volumes of buffer tanks. (This design is not criticalbecause it is dealing with relatively wide ranges.) However, at a later stageof the plants design (see Chapter 10, Section 10.2), this dynamic mathemat-ical model should be used for a

critical task

, in order to

evaluate the conse-quences of any change

in: the composition of the raw materials, the concen-tration of possible impurities, the kinetics of mass transfer, or the qualityrequirements from the new products.

Finally, after the plants start-up, this model should be expanded tocorrelate and interpolate the operating plants results. This expansion willhopefully culminate in the achievement of new process know-how for thedeveloping corporation.

9.6 Complementary bench-scale testing program

Following the experimental work described in Chapter 6, which served asa basis for the preliminary process design described in Chapter 7, specificadditional experimental work will generally be needed to generate somespecific and important missing data.

This complementary program of

bench-scale tests

can probably be donein the same R&D laboratories that were used before, in parallel with theother tasks discussed in this chapter. It can be divided, according to theirlevel of urgency for the overall effort of this working program, into sevendifferent tasks to obtain additional data needed for:

Detailed specification of the industrial equipment Design of pilot installations or interpretation of their results Process modeling



Design of instrumentation The final choice of materials of construction (corrosion) Clarification of waste disposal issues Clarification of process safety issues

9.6.1 Detailed specification of the industrial equipment

Following consultations with the equipment suppliers, a detailed list willemerge of all the specific factors that may have a significant effect on thechoice, sizing, design or expected performance of the different items of majorequipment (see Section 9.3 above).

A fact of life common to almost all projects is that, from the moment oftheir request, the availability of these quantitative results becomes an urgentrequirement for the continuation of effective engineering work, either by thecontractors participating in the bids, or by the engineering company. (Thisurgency will be strongly and repeatedly emphasized by the engineers.)Examples of quantitative data that may be required are:

Simple physical properties, such as the density or the viscosity of aparticular stream, at a specific composition and temperature. Lessfrequently, more complex physical properties may be needed, suchas the wetting contact angle between different phases, thermal con-ductivity, dielectric coefficient and other electrical properties, opticalcharacteristics, and so on.

The density, size distribution, and characteristic shape of resultingsolids (i.e., crushed rock or crystals produced), which could affectthe bulk density of a loosely packed bed of such solids in a silo, ortheir transfer by pneumatic conveying. In addition, the shape andsize of these particles can affect their flow properties (bridging)and their rate of dissolution or of settling.

The reaction rate and/or the mass transfer rates of certain reactions,under specific driving forces and in specific contact conditions, such asthe mixing regime, differential velocity, temperature and pressure, etc.

The ion-exchange rate with specific commercial resins and processstreams, in certain flow conditions.

The results from standardized technological tests, such as the grind-ing rate of solids, the settling rate or the filtration rate of a slurry, thecompaction of a powder under pressure, etc.

9.6.2 Pilot installations

As discussed in Section 9.4 above, pilot-plant installations can be very expen-sive and lengthy operations, and they can get stuck if they are not properlydesigned to cover the specific function of the novel process. However, a pilotmust obviously be designed without having all the necessary information.It may be worthwhile, therefore, to increase its chances of success by getting



some of this information from rapid bench-scale testing, if possible beforecompleting the design of the critical parts of the pilot (for example, thereaction rate curve in a mixed reactor). These bench-scale tests suddenlybecome of the highest priority on the critical path of the whole project.

9.6.3 Process modeling

As discussed in Section 9.5 above (and later in Chapter 10, Section 10.2), themethodology and technique for the development of a dynamic mathematicalmodel, simulating the specific process under consideration, require

accuratenumerical data

at its data base. Most of this data could probably be obtainedfrom textbook laws, published scientific information, or previous test workdone on this subject or on similar projects. However, some

assumptions

areprobably also needed to close the cycle and start the model running.

Thus, after the first few runs that are needed to get a good feeling of thesystem, certain insecure

cause-to-effect

data with significant

leverage

can bedefined. For instance, the cause could be a change in temperature, or a changein concentration of a certain variable that could be caused by dilution, or bythe ineffective dispersion of an added reactant stream. The related effectcould be in the rate of precipitation, in the level of supersaturation, or in thesolubility concentration. Obviously, in any real process, the number of suchtheoretical cause-to-effect relations could be enormous on paper, but for-tunately, only a relatively small number of these relations would generallyhave the kind of leverage to justify their inclusion in the dynamic model,and these relations should be carefully selected and defined, in the limitedrange of practical interest.

Therefore, additional bench-scale tests should be arranged to confirmand complete the data needed on these selected relations. Such tests couldprobably be combined with those described above in Section 9.6.1, since theyare of the same general type.

9.6.4 The design of instrumentation

The choice of instrumentation hardware for chemical plants, from standardcatalogue items, can be critical. Most of the modern instruments are basedon

physical characteristics

of the stream under surveillance, such as its elec-trical conductance or capacitance, its magnetic density, and its optical prop-erties under various wavelengths. Entrained impurities in the actual processstream, or even simple dissolved components such as water or atmosphericgases, may affect some of these physical properties.

Fortunately, the specialized companies supplying such hardware havetheir own extensive data bases and their instruments cover wide ranges sothat, in most cases, they are able to complete their recommendations andoffers on the basis of the nominal analyses of the streams concerned, withthe reservation that their final calibration needs to be done during the plantsstart-up. However, there may also be some reservation when a new process



is considered and their guarantee conditional on certain

assumed

values ofthese characteristics. These companies will probably recommend performingspecial tests to supply such information or perhaps delivering representativesamples for testing in their laboratories.

9.6.5 Corrosion tests

The tests needed to confirm the choice of materials of construction werediscussed above in Chapter 3, with respect to any unknown corrosion effecton the materials of construction used for the equipment and piping. This isimportant first for establishing safety measures to prevent accidental failure,but also for estimating the lifetime of each piece of equipment, its supplycost and maintenance schedule, or the possible contamination of the productwith metallic traces.

The orderly testing of the corrosion rate is a long procedure that was(hopefully) started at the beginning of the process development, for eachcombination of the most probable construction materials and some typicalsets of process conditions. An expert consultant with relevant industrialexperience was probably engaged at that time to recommend options andprocedures to arrive in time at the optimum specifications for materials ofconstruction.

But at that time, the exact process conditions for corrosion testing (com-positions, chemical additions, or temperatures) were not available. Now,since the confirmation of the final choice has to be included in the purchasingspecification of the equipment and the matter is again on the critical path ofthe project, additional tests may have to be done very urgently with the finalmaterials and conditions.

Furthermore, the public authorities and the insurance company repre-sentatives may insist on receiving written certification from an expert, atleast in relation to the risks and damages that may result from a possibleaccidental failure.

9.6.6 Clarification of waste disposal issues

The definition and quantification of all the possible waste streams andoptions for their disposal within the framework of the particular regionconsidered, are critical features of any new chemical implementation. Thisspecialized field of activity includes various technical, commercial, and legalaspects. During the new process development stages, at least one acceptableand affordable disposal procedure has been defined for each waste streamand included in the projects scope. But now, this proposed disposal proce-dure should be presented to the relevant authorities, with all the supportingdata to obtain their formal authorization.

Urgent tests may now be performed to produce any additional data thatmay still be needed for the final design of the treatment operation and theconvincing evidence of the results. These tests are generally of a specialized



nature and may have to be subcontracted to a suitable laboratory or to aninstitution with the relevant experience. For example, in one case, it wasintended that most of the organic waste stream would be incorporated intoa commercial cattle-feed mixture and thus had to meet certain specifications.In another case, the solid residue was intended to be integrated into abuilding-blocks production line and had different requirements. In stillanother case, the residue of microorganisms from a fermentation processwas found to have a very beneficial effect on the operation of a municipalsanitary-waste bio-sludge installation. Each case is different and there aremany problematic situations.

9.6.7 Clarifying process safety issues

Most chemical plants could present some form of known safety hazard,which has to be kept well under control. (See Chapter 3.) The implementationof a novel industrial chemical process can introduce an unknown safetyhazard, unfamiliar to the corporation and not taken into account in itsoperating practice. A systematic survey and consultations with a safetyexpert should have been started early enough in the development programto identify such potential safety issues, and to document them in detail, indifferent safety manuals, for the lab, pilot operation, and plant. Relevantpublic regulations in the area of implementation should also have beensurveyed, and this information included in the plants design and control,with the necessary requirements to ensure safe operation, to the best of theproject managers judgment.

Now, with the finalization of plant design and the application for thenecessary permits, certain

standard

laboratory tests may still be needed (pos-sibly from a statutory organization such as a standards institute) to

certify

certain key issues, such as for example, the flash-point for a particular mix-ture of organic solvents, or the handling of a certain radioactive or poisonousimpurity present in any of the raw materials or fuels, which should bemonitored and kept under surveillance.

9.7 Preparation of product samples for market field tests

The marketing experts of the corporation generally conduct these fieldtests, either directly or through their regular geographical distributionchannels, while the plant is being designed. The usual procedure is tocontact a number of randomly chosen end users, show them the samples,the analyses, and the specification of the expected products, and ask fortheir comments.

The feedback from such contacts should be available as soon as possible,as it could be very important for:

Confirmation of the final form designed for the products Specification of any change needed



Confirmation of the estimated sales revenue from the products

But this simple standard procedure can only start when significant quan-tities of representative samples of the products are made available, of theorder of tens of kilograms. Thus, an important but difficult task, at thisstage of the working program, is to prepare rapidly such representativesample products, without a production line. This problem should beemphasized to the whole team, as creative thinking and past experienceare often needed, for example, to:

Integrate as much as possible of such production into the piloting orthe testing programs mentioned above, such as the crystallization,evaporation, and liquidliquid extraction.

Improvise practical batch or manual methods, with any availableequipment, to prepare large quantities of starting material and tobridge over the missing intermediate operations, such as acid leach-ing, filtration, centrifugation, solid drying, and screening.

9.8 Clarification concerning any formal permits needed

Any new plant projected will require, most probably, a number of formalpermits from different public authorities, as well as comprehensive insurancepolicies. These permits differ from country to country, but they are concernedwith different aspects of:

The plants construction, in relation to possible adjoining operations,local building planning, residences, roads, etc.

The plants operation, in particular the transportation of materials,ecology, the disposal of possible accidental leaks or gases, etc.

The safety of the plants personnel, including fire fighting (see Ref-erences 9 and 10)

The marketing of the product, where public regulation is concerned,such as for food, pharmaceutical, animal feed, or building materials

Disposal of waste streams and possible poisonous or radioactive effects

The technological background is detailed in several basic referencebooks.

6, 7, 9, 10

Early clarification with the authorities as to proper procedureis best conducted by corporate specialists or consultants, to indicate exactlywhat factual information should be provided by the corporation to securethese formal permits, possibly in the form of an environmental impactstatement, required in certain regions. Then, the project manager will deter-mine if such data is already available in a convincing form, or if its prepa-ration would require any

additional testing or engineering studies

. The prepa-ration of such document can require a great deal of work from theprofessional members of the core team and their consultants, especially fora new process or product, considering the lack of exactly similar references.



9.9 Worth another thought

If we knew at the time of the first patent application what we knowat this present stage, how would we formulate the patents claims?

Certain very simple process concepts that are almost taken forgranted can become quite complicated to design and operate in theplant, and will require careful attention to many details, to beapplied successfully.

Major equipment packages are groups of equipment items that arepivot in the plant and should be designed or procured together, inprocess-compatible materials.

For a critical major equipment package, the actual purchase cost isprobably a secondary consideration of the project team, as long as itremains in the reasonable range.

The configuration of other major equipment may have to be speciallydeveloped (or more exactly modified) and designed to meet thespecifications of the new process.

A pilot plant that is owned by the corporation is expensive, requiresin-house expertise and a relatively long time to start, and therefore,would be justified only for a long-term continuing R&D program inthis particular field.

Any dynamic mathematical process model can only be as good andaccurate as the numerical data in its data base and this weak pointhas discouraged many developers of novel processes. It is importantto recognize the importance of this tool and to consider it as a long-term investment in the process development program.

At a later stage, this dynamic mathematical model should be usedfor a critical task, in order to evaluate the consequences of any pos-sible change in the composition of the raw materials, the concentra-tion of possible impurities, the kinetics of mass transfer, or qualityrequirements for the new products.

References

1. Bequette, B. W.,

Process Dynamics, Modeling, Analysis, and Simulation

, PrenticeHall, New York, 1997.

2. Law, A. M. and Kelton, D. M.,

Simulation, Modeling, and Analysis

, 3rd edition,McGraw-Hill, New York, 1999.

3. Edgar, T. F. and Himmelblau, D. M.,

Optimization of Chemical Processes

,McGraw-Hill, New York, 2000.

4. Turton, R. et al.,

Analysis, Synthesis, and Design of Chemical Processes

, Simon &Schuster, New York, 2000.

5. Corbitt, R. A.,

Standard Handbook of Environmental Engineering

, 2nd ed.,McGraw-Hill, New York, 1998.

6. Meyers, R.A.,

Encyclopedia of Environmental Pollution and Cleanup

, John Wiley& Sons, New York, 1998.



7. Tedder, D. W. and Pohland, F. G., Eds.,

Emerging Technologies in HazardousWaste Management

, ACS Symp. Series, American Chemical Society, Washing-ton, D.C., 1990.

8. U.S. Department of Health, Education, and Welfare,

Air Pollution EngineeringManual

, Washington, D.C., 1967.9. Steinback, J.,

Safety Assessment of Chemical Processes

, John Wiley & Sons, NewYork, 1998.

10. Kletz, T. A.,

Process Plants, A Handbook for Inherently Safe Design

, Taylor andFrancis, London, 1998.

11. Cusak, R. W., Glatz, T. J., and Holmes, T. L., The AP column, the developmentof a high-capacity extraction column,

Trans. Int. Conf. Solvent Extraction

, 1999,427. Cox, M., Hidalgo, M., and Valiente, M., Eds., Society of Chmeical Indus-try, London. (Koch Process Technologies).

12. Becker, O., Lewis, C., Hardy, R., and Seiber, F., Axial mixing in large packedextractors, Trans. Int. Conf. Solvent Extraction, 1999, 475. Cox, M., Hidalgo, M.,and Valiente, M., Eds., Society of Chmeical Industry, London. (Koch Glisch)

13. Lo, T. C., Process development, design and scaleup using a large Scheibelextraction column, Trans. Int. Conf. Solvent Extraction, 1999, 1503. Cox, M.,Hidalgo, M., and Valiente, M., Eds., Society of Chmeical Industry, London.

14. Movsowitz, R. L., Kleinberger, R., Buchaliger, E. M., Grinbaum, B., and Hall,S., Comparison of full-scale pulsed-column versus mixer-settlers for uraniumsolvent extraction, Trans. Int. Conf. Solvent Extraction, 1999, 1455. Cox, M.,Hidalgo, M., and Valiente, M., Eds., Society of Chmeical Industry, London.(Bateman-Israel)



Developing an Industrial Chemical Process, An Integrated ApproachTable of ContentsChapter 09: Working program toward a first implementation9.1 Patent protection9.1.1 Revised or additional applications9.1.2 Extended geographical coverage of the patents

9.2 Detailed process design9.2.1 Piping and Instrumentation Diagrams9.2.1.1 Piping lists9.2.1.2 Valves9.2.1.3 Instruments9.2.1.4 Control loops9.2.1.5 Flanged manholes and hand-holes in closed pieces of equipment9.2.1.6 Provisions for possible future connections9.2.1.7 Non-conventional drives

9.2.2 Examples of portions of piping and instrumentation drawings

9.3 Major equipment packages9.4 Pilot testing of specific process operations9.4.1 Multiple-effects evaporator9.4.2 Liquidliquid contacting battery9.4.3 Main problems for piloting

9.5 Modeling9.6 Complementary bench-scale testing program9.6.1 Detailed specification of the industrial equipment9.6.2 Pilot installations9.6.3 Process modeling9.6.4 The design of instrumentation9.6.5 Corrosion tests9.6.6 Clarification of waste disposal issues9.6.7 Clarifying process safety issues

9.7 Preparation of product samples for market field tests9.8 Clarification concerning any formal permits needed9.9 Worth another thoughtReferences

1360_ch09

Documents