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TRANSCRIPT
ENVIRONMENTAL EMISSIONS FROM A
SUSPENSION FIRED BOILER WHILE BURNING
REFUSE DERIVED FUEL AND COAL MIXTURES
JERRY L. HALL*t, GARY A. SEVERNS*, HOWARD R. SHAN KSt, ALFRED W. JOENSEN*, and
DELMAR B. VAN METER* Engineering Research Institute and Mechanical Engineering Department
Iowa State University* and Ames Laboratory (U.S. Department of Energyt
Ames, Iowa
ABSTRACT
Results are presented of the emission evalua· tions of a suspension fired steam generator operat· ing at the Ames, Iowa power plant while burning mixtures of refuse derived fuel (RDF) and coal. The facilities, test design and sampling procedure are summarized and emission results are given. Emissions of uncontrolled particulates, chlorides, trace elements of copper, lead and zinc all increase consistently with increases in RDF as expected for the composite fuel analysis. Emissions of sulfur oxides and nitrogen oxides decrease with increases in RDF. No discernible trends, within the data scatter, were noted concerning formaldehyde, hydrocarbons, and many of the 19 different trace elements scanned during these experiments. Combustible and noncombustible characteristics of the boiler grate ash became more like the cor· responding flyash characteristics as the amount of RDF was increased. The test data from the City of Ames studies show that the particulate emissions are capable of being controlled within al· lowable compliance rates provided the dust col· lectors are suitably designed and operated.
INTRODUCTION
The City of Ames, Iowa has been commercially operating a system for energy and materials reo covery from municipal solid waste (MSW) since November 1975 . The Ames solid waste recovery system consists of a 150 ton/day (136 tid) refuse
processing plant, a 5 00 ton (454 t) Atlas processed refuse storage bin, and the existing Ames municipal power plant. Air classified shredded refuse is pro· duced for use as a supplementary fuel with coal. Ferrous and nonferrous metals are also recovered.
Evaluations of the refuse processing plant and the power plant have been conducted since February, 1976, and are a cooperative venture among the City of Ames, EPA, DOE's Ames Laboratory, Iowa State University, and Midwest Research Institute. Since the Ames system was designed primarily based on the St. Louis experience, these evaluations offered the opportunity to fill tech· nological data gaps as well as confirm selected observations from the St. Louis studies.
Operatio� of the recovery system included burning of the refuse derived fuel (RDF) as a sup· plementary fuel with coal in a suspension·fired steam generator. The supplementary burning of the RDF in stoker boilers was to occur during shutdown of the pulverized coal unit. However, attempts at firing RDF in the existing Ames suspen· sion system revealed that high dropout of unburn· ed wood, cardboard, and large paper prevented continuous burning. Therefore, the suspension· fued bbiler was modified by the addition of bot· tom grates to allow continuous co·firing of RDF and coal. RDF is now burned in the suspension· fired boiler on a regular basis.
497
FACILITIES
Municipal solid waste dumped on the tipping floor of the refuse processing plant is reduced to a
nominal 6 in. (152 mm) size by the first stage shredder. Mter passing the magnetic separator for ferrous removal, the shredded refuse is further reduced in size to a nominal 1.5 in. (38 mm). The shredded material is then air classified into a light combustible fraction (RDF) and the heavy rejects. The heavies are then subjected to further removal of ferrous and nonferrous material.
The RDF is pneumatically conveyed to Unit 7 through either of two 8 in. (203 mm) transport pipelines at an average rate of 4-9 tons/hr (1.0-2.1 kg/s). Injection of the RDF into the furnace of the unit was at a location directly between the pulverized coal injection nozzles except for four runs at 100 percent load.
Table 1 includes descriptive characteristics of the suspension-fired steam generator (Unit No. 7) used for the tests. The unit has a wet bottom ash removal system. An electrostatic precipitator is the type of air pollution control equipment currently installed on this unit.
EXPERIMENTAL DESIGN
For this study it was determined that two major factors could be controlled at various levels. These factors were the steam generator load based on either steam flow generated (or megawatts of power generated) and the amount of RDF based on heat energy input to the boiler. The levels of these factors were chosen to be 60, 80 or 100 percent nominal steam generator load, and 0, 10 or 20 percent RDF. To obtain sufficient data for statistical analysis, a factorial experimental design with three replications was devised for the steam generators as summarized in Table 2. Thus the statistical design was 'a 3 x 3 x 3 (3 loads, 3 values of RDF and 3 replications) full factorial experiment with 27 runs required to fill the data matrix of this experiment. Additional miscellaneous testing was accomplished on this steam generator for purposes of ascertaining compliance with Iowa Department of Environmental Quality rules. During these tests the location of the RDF injection point was changed compared to the EPA designed experimental runs. The results of all tests concerning this steam generator are contained herein.
To satisfy the objectives of the environmental emissions study, all appropriate input and output streams associated with the operation of the steam generator unit were sampled. A block diagram showing the sample locations of both entering and leaving streams is included as Fig. 1. The tests ac-
complished concerning the environmental study on Unit 7 are summarized in the data matrix format of Table 2 as previously indicated. All inputs to and outputs from the steam generator were evaluated including fuel, combustion air, bottom ash, steam, fly ash and stack gas.
A block diagram showing the sample locations and types of samples collected is included in Fig. 1 . All of the sampling was conducted on a regular basis except the organic species which were sampled on intermittent days as manpower, instrumentation, and equipment would allow.
TESTING AND SAMPLING PROCEDURES
Sampling of effluents was conducted according to EPA prescribed techniques [I ,2,3] . Stack particulate samples were obtained at numerous prescribed points in the smoke stack cross section as shown in Fig. 2. In addition, three stack sampling trains operated Simultaneously while an additional particulate sampling train was located before the particulate collector. Figs. 3 and 4 show the sampling location and sampling points at the collector inlet. Input fuel and grate ash were sampled at regular 30 min. intervals throughout the test period, and then mixed to yield a composite sample. Hopper (fly) ash was sampled at the completion of each experimental run. Combustion air to the boiler was monitored by wet and dry bulb thermometry. Steam flow rate, temperature and pressure were also recorded at regular intervals.
The composite coal and RDF samples were analyzed by the Ames Laboratory. Ultimate analyses and heating values were obtained by standard ASTM methods. Trace elements in the fuels and ash were determined by x-ray fluorescence [4] (XRF) techniques. Trace elements in the sample train impinger solutions were determined by inductively coupled plasma [5] (ICP) techniques.
The size distribution of the particulates after the dust collector was determined via an Andersen type cascade impactor. Particulate samples obtained with the EPA Method 5 sampling train were analyzed via XRF. The impinger solutions front the Method 5 train were analyzed via ICP.
The gases CO2, CO, °2, and N2 in the stack were determined via Orsat techniques. EPA Method 7 was used for evaluation of NO x levels and the EPA Method 6 was used for measurement of S02 . C1 through Cs hydrocarbons were determined by gas chromatography. Several modifications [6,7]
498
TABLE 1 CHARACTERISTICS OF AMES MUNICIPAL POWER PLANT UNIT 7 SUSPENSION STEAM GENERATOR
Manufacturer
Electrical output - MW
Installation date
Pressure temperature
kPa/oC
(psi/ OF)
,
Nominal steam output capacity
kg/h (kg/s)
(lb/hr)
Coal firing equipment
Furnace pressure
Dust collection Equipment
Stack height
meters
(feet)
Heat input at nominal •
capac1ty
MJ/h (kJ/s)
(BTU x 106
/hr)
Coal fired, TPH @ 9540 BTU/lb
Combustion Engineering
35
1968
6205/481
(900/900)
163,600 (45.4)
(360,000)
2 pulverizers
8 nontilting tangential burners
Balanced Draft
American Standard
electrostatic precipitator
61
(200)
460 (0.13)
( 436)
22.9
RDF capability, TPH @ 5000 BTU/lb
(kg/s @ 11,629 kJ/kg)
with 10% and 20% of total 4.4 @ 10% (1.1 @ 10%)
fuel input being RDF 8.7 @ 20% (2.2 @ 20%)
499
ALYSIS FLOW RATE ULTIMATE AN HEATING VAL CHEMICAL AN
UE ALYSIS LEMENTS
TABLE 2 TEST MATRIX FOR UNIT 7 EXPERIMENTAL RUNS
Percent RDF Percent
Load 0% 10% 20%
60% 3 runs --- ---
(1976)
80% 3 runs 2 test runs ---
(1976) (1977)
100% 3 runs --- ---
(1976)
80% 3 runs 3 runs 3 runs (Wyoming (1978) (1978) (1978)
Coal)
100% 3 runs 3 runs 3 runs (Wyoming (1978) (1978) (1978)
Coal)
100% --- --- compliance tests* (Wyoming 4 runs
Coal) (1978)
* RDF injection nozzles relocated to be below the coal injection nozzle.
FILTER PARTICULATE TRACE ELEMENTS
IMP INGER WATER TRACE ELEMENTS
EMISSION RATES OF
PARTICULATE TRACE ELEMENTS
IMP INGER WATER TRACE ELEMENTS
EMISSION RATES OF PARTICULATE & TRACE E ASH SOFTENI NG TEMPERATURE PARTICULATE AND GASEOUS SPECIES
HUMIDITY BAROMETER INTAKE COAL
\ PARTICULATE SIZING
•
,
TEMPERATUR E � AIR / VOLUME FLOW DENSITY ULTIMATE ANA HEATING VALU CHEMICAL ANA
TRACE ELEM ASH SOFTENIN
TEMPERATUR
BOILER • COLLECTOR RDF UNIT STACK \
LYSIS E LYSIS & HOPPER , ENTS ASH " G E FEEDWATER GRATE STEAM -ASH \ FLOW RATE
CHEMICAL ANALYSIS & TRACE ELEMENTS
• SOFTENING TEMPERATURE TEMPERATURE FLOW RATE FLOW RATE FLOW RATE CHEMICAL ANALYSIS & TEMPERATURE
TRACE ELEMENTS PRESSURE SOFTENING TEMPERATURE
FIG.1 SAMPLING LOCATIONS OF ENTERING AND LEAVING STREAMS
5 00
SAMPLING PLATFORM
POINT
A
B
C
0
E
F
IN ,
14.22
24.67
31. 78
37.63
. 42.65
47.25
SAMPLING POINTS 4 In. PORT,
v-.:.c ? -- CAPPED WHEN
NOT SAMPLI NG
WALL
NOT TO SCALE
SAMPLING POINTS
RADIUS POINT
RADIUS
m IN m
0.361 G 51. 32 1.303
0.626 H 55.03 1. 398
0.807 1 58.67 1 .490
0.956 J 62.02 1. 575
l.OB3 K 65.22 1.656
1.200 L 68.15 1. 731
FIG.2 STACK SAMPLING POINTS
RESISTIVITY
PROBE PORT
GAS FLOW •
EXTERIOR
POWER PLANT---...
WALL
• NOT TO SCALE
VANE
UNIT 7 PORT LOCATIONS •
8EFORE PARTICULATE COLLECTOR
,
, •
CROSS SECTION A-A 4ft x 20 ft
SAMPLING PORTS
'-'------ --
\ "'-l._ VANES \
TO LS.P. •
FIG. 3 SAMPLING LOCATIONS AT THE COLLECTOR INLET
o 0
o 0
UNIT 7 SAMPLING POINTS BEFORE THE PARTICULATE COLLECTOR
o o
o o
o 0 0 0 0
o 0 0 0 0
o 0
o 0
o
o b C
o 0 0 0 0 0 0 0 0 0 0 0 0 b
0 0 0 0 0 0 0 0 0 0 0 0 0 .
OIMENSIONS
IN m IN m .
A 9.25 0.235 • 6.0 0.152
B lS.5 0.470 b 12.0 0.305
C 240.0 6.096 C 4S.0 1. 219
FIG.4 COLLECTOR SAMPLING POINTS
501
of the EPA Method 5 train were used to collect samples for analysis of aldehydes and ketones, chlorides and trace elements.
Table 3 is 11 summary of the sampling methods used for the tests of this study.
During a given test, samples were obtained at all locations previously shown in Fig. 1. The input fuel and boiler load were held as constant as possible at their preselected nominal values during a given test run. Each test was typically 4-5 nr in length if no difficulties were encountered. On some occasions tests lasted for more time than the nominal because of various difficulties that arose concerning sampling, boiler operations of refuse feed to the boiler. Also, on some occasions, backto-back tests were accomplished during a given day. However, such back -to-back tests were those accomplished for compliance testing as required and monitored by the Iowa Department of Environmental Quality. Input coal and RDF were sampled at regular � hr intervals throughout the testing period on any given day. These samples were then mixed to yield an appropriate composite sample for the given test.
The stack effluents were generally sampled according to EPA prescribed techniques [1,2,3] . The preparation of each sample train include: 1. cleaning of sample train glassware with an appropriate acid wash followed by several distilled water rinses; 2. preparation of chemicals and loading of sample train impingers with appropriate absorbing solutions; 3. weighing and labelling each impinger of each sample train; 4. weighing and loading particulate train filters; 5. checking sample boxes, control boxes, and sample probes for proper operations; and, 6. transporting the sampling equipment to the test site and preparing for the sampling test as scheduled with the City of Ames personnel.
Before operation of any sampling train, leak checks were performed from the sampling train probe tip to insure that such sample train was leak free. No sampling train was operating until it had passed an appropriate leak check with a maximum
allowable leak rate of 0.02 cfm (O.OO l1/s) at a sampling train vacuum of 15 in. of mercury (50.7 kPa). This leak rate was also allowed at a lower vacuum if the vacuum level of the leak check was not exceeded during operation of a particular sampling train during a test. All sample train leak checks during this study complied with this leak rate criterion. After each experimental run, a leak check was also performed to insure that no leaks had developed during the sampling period.
TAB LE 3 SUMMARY OF SAMPLING AND ANALYTICAL PROCEDURES
Item Sampled
Fuel into boiler Coal
• RDF
Combustion · Air
Ash Grate (bottom ash) Collecteq fly ash (hopper ash)
Steam
Fly ash Before particulate collector Stack
Flue gas · Stack
Sampling Techniques
Hourly samples combined to form single components sample
Thermometry
Grab samples combined to form single composite sample
EPA Method S Brinks impactor
Andersen impactor Brinks impactor
Orsat EPA Method 7 EPA Method 6 Modified EPA
Method S Modified EPA
Method S
Modified EPA Hethods S & 6
Modified EPA Method S
Grab sample
Aspiration across column of macroreticular resin
502
Analytical Procedure
• Trace elements via XRF Ash via ASTM method Moisture via ASTM method HHV via ASTM method
. Wet bulb and dry bulb temperature
Trace elements via XRF or appropriate ASTM method Ash via ASTM method Moisture via ASTM method HHV via ASTM method Trace elements in grab sample composite taken from particulate collector hopper ash
Flow rate Temperature Pressure
Trace elements in material on filter via XRF
Size distribution via impactor Trace elements in impinger solutions via rcp
CO2' CO, O2, N2 NO SOx
A1�ehydes and ketones via method of Carotti and Kaiser Organic acid via ion chromatograph Cyanide via ion selective electrode Phosphorus via spectrophotometer
Chlorides via colorimetric and spectrophotometric analysis of part of impinger solutions from SO train
x
Mercury, arsenic, antimony beryllium via rcp C] and Cs hydrocarbons via cfiromatography
and
gas
Organics (PCB, POM, etc.) via gas chromatograph-mass spectrograph
TIle samples were obtained either isokinetically or proportionally as required, but only after appropriate calibrations of the sample train dry gas meter, flow orifice, pilot tube, sampling nozzle and the temperature indicators on the sampling train had been properly ascertained.
After sampling, the sample train impingers and filters were weighed and prepared for laboratory analysis as necessary. The impinger chemicals were transferred to clean reagents bottles, the filters were desiccated to dryness before weighing, and the coal, RDF, and ash samples were appropriately mixed and processed prior to chemical analysis. All of the samples were then transferred to the various analytical groups of the Ames Laboratory-DOE for analysis.
RESULTS
Most of the results are reported in a data matrix format that indicates the control factor of load and per cent RDF on the experimental runs accomplished. The results for each of the three runs are tabulated as a cell average and cell standard deviation in the various tables presented in this section of the results. Each data point on the various plots included in this section of the report is the cell average. Thus, each data point represents the average of three experimental runs unless otherwise noted. It should also be noted that two standard deviations on each side of the cell average would apprOximately correspond to the 95 percent statistical confidence band. This means that there would be about 95 percent probability that the actual value of the measured variable would fall within the range of two standard deviations on each side of the cell average.
Curves and lines drawn through the data points contained on the plots are meant to show general trends in the data. Such curves are not to imply any particular mathematical expression which may (or may not) govern the behavior of a particular measured variable.
AIR, FEEDWATER AND STEAM CHAR
ACTERISTICS FOR THE EXPERIMENTAL
RUNS
Table 5 includes the average air, feedwater, and steam characteristics for the experimental runs performed for the steam generator Unit 7. Both the average and standard deviations are given for each cell, where each cell represents a given nominal
turbine load and a given percent of RDF input on a heat energy basis. From this table it can be observed that the steam load is also tabulated on a percent basis which corresponds approximately to a given percent turbine load. The actual RDF heat energy input tabulated shows some slight variation from the nominal values desired for the test set-up. The variation in the amount of heat energy input is indicative of the amount of control of that particular variable experienced during the operation of Unit No.7.
The characterization of the air entering the boiler unit for combustion purposes is given by wet bulb and dry bulb measurements which have been used to determine the relative humidity of the the air entering the boiler. The barometric pressure of the air at that turbine location is also tabulated. The feedwater temperature is tabulated as well as the pressure and temperature of the steam which is generated in the boiler unit for use in the turbine. The flue gas or combustion products being exhausted from the boiler into the stack are given in terms of flow rate, temperature and pressure as measured at the sampling location in the smokestack of the Unit 7 steam generator complex.
CHARACTERISTICS OF INPUT FUELS
The average of heating values and ultimate analysis constit.uents, as well as their standard deviation for both the coal and RDF used during the tests on Unit 7 are listed in Table 6. It should be noted that the ash content of the RDF is higher than that of the coal used during 1978 and that both the heating values and the amount of sulfur in the RDF is lower than that of the coal for the comparison runs made during this study. The significance of these observations is that as the amount of refuse used in the boiler unit is increased, an increased amount of ash will be generated due to using refuse. The additional amount of ash was expected to show up partially as fly ash and partially as bottom ash. Consequen tly, as the RDF increased, the amount of particulate emissions was expected to increase. This was also in agreement with the previous data obtained on travelling grate stoker Units 5 and 6 during 1976 and 1977 studies on the travelling grate units.
Because the sulfur content of the RDF was lower than in the coal, it was also expected that the oxides and sulfur emitted from the smokestack would decrease Significantly with increases in RDF.
503
TABLE 4 SUMMARY OF SAMPLING TRAIN CHEMICALS AND SAMPLING FLOW RATES
Sample Train
Particulate (EPA Method 5 )
Oxides of Sulfur (EPA Method 6 modified and with 5 impingers)
Organic Acid (EPA Method 5 modified with Tenal< plug*)
Aldehyde and Ketone (EPA Method 5 modified)
Trace Element (EPA Method 5 modified with midget impingers)
Impinger Number and Solution or Material
1
200 mL distilled H
20
2
200 mI, distilled H
20
100 mL 100 mL 8 0 % Isoproponal 3% H
20
2
100 mL NaOH
empty or dry
25 mL NaOH
100 rnL NaOH
100 mL NaHS0
4
25 mL ICL
3
empty or
dry
4
200 gDrierite
100 mt 100 mt 200 g
3% H2
02
NaOH Drierite
100 mL 200 g: NaOH Drierite
100 mL 200 g-NaHS0
4 Drierite
25 mL 10 g. ICL Drierite
* Tenal< plug used to absorb organic vapors from sampled flue gas.
Typical Flow Rate
i/min
Isokinetic
8
8
1
1
Typical Sampling
Time, min
144
30
60
60
60
TABLE 5 AVERAGE AIR, FE EDWATER. AND STEAM CHARACTERISTICS FOR EXPERIM ENTAL
RUNS ON BOI L ER UNIT 7
Nominal Turbine Load (%)
60
80
80
80
80
100
100
100
100
100
RDF (%) Year
° 197 6
o 1976
o 1978
10 1978
20 1978
o 1976
° 1978
10 197 7
10 1978
20 1978
Steama
Load (%)
RDF Heat Input
(%)
Air Wet Bulb
°c
Dry Bulb
°c
� 4 5 .4 0 . 00 12.0 5 .
a 1.9 0.00 6.6 5 .
x 65.2 0.00 3.0 -1.
a 0.7 0. 00 5 .0 4.
x 64.7 0.00 22.0 28 .
a 1.6 0.00 5 .0 4 .
x 65.3 12. 72 19.0 23.
a 0.5 1.4 3 3 . 0 2.
x
a
x
a
x
63 .8
0.8
86.7
1.5
88.5
18 . 9 6 18.0 23.
5 .27 2.0 5 .
0.00 04.0 -7 .
0.00 11.0 9 .
0. 00 23.0 28.
a 1.3 0.00 3 . 0 3 .
x 88 . 6 10.07 21.0 15 .
a 1.6 0.17 1.0 2.
x 8 6. 9 13.52 22.0 27.
a 1.2 1.95 2.0 2.
x 8 8 .6 20.80 23.0 28 .
a 1.6 1. 18 3 .0 3 .
ReI Hum (%)
3 3 .
1.
4 7.
10 .
Bar Pres
kPa
Feed Water Temp
°c
9 7.20 18 1.
0.44 1.
9 7 .80 195 .
0.78 2.
Steam Temp
°c
4 7 9 .
2.
4 7 6.
2.
60. 9 7.68 197 . 4 7 6.
8. . 0.58 2. 2.
69.
17.
5 7 .
12.
4 3 .
4 .
64 .
6.
5 3 .
10.
64 .
10.
62.
9 .
98.09 196.
0 .44 1.
98.09 194 .
0 . 30 1.
9 8 .00 206.
0 .7 5 2.
9 7 .68 209.
0 . 58 1.
9 8 . 00 209 .
0 . 00 2.
97.92 209.
0 .14 2.
9 7 .68 209 .
0.20 2.
4 77.
1.
4 7 6.
1.
480.
1.
486.
2.
4 77.
2.
4 79 .
3 .
485 .
4 .
Steam Pres
kPa
58 67.
4 .
5888.
18 .
604 8 .
14 5 .
6151.
21.
6034.
152.
5929.
17.
5896.
34 .
5895.
Stack Flow CMS
stp
Stack Temp
oK
3 0 . 08 4 34 .
0.22 4 .
3 7. 62 4 4 1 .
2.85 9 .
38 .79 454 .
2.31 4 .
3 7.76 4 68 .
0 . 59 3 .
3 7 .9 1 481.
0.38 4 .
50 .75 4 5 3 .
0. 18 7.
4 5 .44 4 69 .
0 . 9 6 5 .
4 1.96 4 4 9 .
O. 11. 15 4 .
5 9 17 . 42.92 4 68 .
4 1. 2.34 6.
6234 .
4 8 .
4 3 .53 4 7 9 .
1.59 13 .
a Re 163,600 kg steam/h
b x and a represent the mean and + the standard deviation, respectively
504
Stack Pres
kPa
96.89
0.45
9 7.40
0 .76
97 . 0 6
0 . 5 7
9 7 . 4 6
0 . 4 6
9 7 .4 7
0.29
9 7 .68
0 .61
9 7 .34
0 . 4 4
9 7 . 3 8
0 . 01
9 7 .33
0.10
97. 11
0.18
TABL E 6 VALUES OF COAL AND RDF CHARACTERISTICS AS FIRED
Quantity Coal RDF
Number of Samples 1976
mean Std Dev
(x) Number of Samples
Heating Value (HHV) kJ/g 22.42
(BTU/1b) (9648
Moisture (%) 16.67
Ash (%) 12.98
Carbon (%) 53.96
Hydrogen (%) 3.42
Sulfur (%) 3.27
Chlorine (%) 0.03
Oxygen (%) 9.66
CHARACTERISTICS OF BOTTOM
AND FLY ASH
(0) 14
0.13
57)
3.91
2.30
2.81
0.65
0.85
0.01
1.52
Tables 7 and 8 are tabulations of the combustible and noncombustible constituents of the bottom ash and the fly ash respectively from Unit 7. The interesting feature of this data is that the characterizations of fly ash and bottom ash in terms of mineral matter and carbon are Significantly different when coal is the only fuel burned in the boiler. However, as the fuel mixture changes from 0 - 20 percent RDF, the characteristics of the fly ash and bottom ash become nearly identical.
Another feature of the data in Tables 7 and 8 is that tabulations are given for operation of Unit 7 both before bottom dump grates were installed and after the bottom dump grates were installed . A comparison of this data shows that the bottom grates were highly Significant in retaining unburned combustible material in the furnace region so that the combustible portion of the RDF could continue to burn once it has fallen through the
505
1978 1978
mean Std Dev mean Std Dev
(x) (0) (i) (0) 18 12
23.6 0.52 13.02 0.83
(10156 224) (5602 359)
16.6 1.2 24.04 3.06
9.74 2.23 13.09 2.72
56.6 1.5 30.66 2.92
'4.01 0.19 4.51 0.44
2.79 0.81 0.32 0.05
0.21 0.12 0.35 0.15
9.08 2.26 27.04 2.87
suspension zone to the grate of the boiler. Thus, the dump grates were instrumental in helping derive the available heat energy from the fractions of RDF that had fallen through the suspension zone of the boiler before complete combustion had occurred. For example, with 1 0 percent RDF at 1 00 percent load as much as 35.4 percent of the ash was carbon dropping to the bottom pit of the boiler and being lost to the system before the installation of the dump grates. After the installation of the dump grates the loss of carbon amounted to about 1.5 percent of the ash. A similar characteristic shows up for the carbon in the fly ash but the degree of this loss in carbon is much less than with the bottom (grate) ash.
Another interesting feature of the data is that the mineral ash content of both the bottom and fly ash became more nearly the same (on the order' of 97 percent) following installation of the dump grates. Prior to the dump grate installation the percentage of mineral content in the bottom ash was significantly lower, mainly because of the add i-
Parameter (%)
Carbon
Hydrogen
Sulfur
Chlorine
Mineral
Carbon
Hydrogen
Sulfur
Chlorine
Mineral
TABLE 7 ANALYSIS OF BOTTOM ASH FROM BOI L ER UNIT 7
Prior to Installation of Dump Grates; 1976,1977
60% Load 80% Load 100% Load 0% RDF 0% RDF 0% RDF 10% RDF
7.51 (4.90)a
0.87 (0.56)
2.58 (1.12)
0.01 (0.01)
89.0 (4.33)
0% RDF
4.66 (0.88)
0.20 (0107)
1.07 (0.87)
0.01 (0.00)
94.8 (0.82)
5.46 (1.24) 5.53 (0.95) 35.4
0.61 (0.20) 0.49 (0.15) 3.83
3.59 (1. 40) 2.90 (3.95) 0.75
0.00 (0.00) 0.00 ·(0.01) 0.18
90.3 (0.98) 91.1 (4.76) 59.9
After Installation of Dump Grates; 1978
80% Load 10% RDF
2.10 (0.28)
0.23 (0.02)
1.12 (0.99)
0.02 (0.01)
96.6 (0.82)
20% RDF
3.11 (0.72)
0.37 (0.08)
0.31 (0.04)
0.02 (0.02)
96.2 (0.80)
0% RDF
6.62 ( * 0.38 * )
8.98 * ) 0.03 ( * ) 84.0 ( *
100% Load 10% RDF
1.49 (0.27)
0.18 (0.04)
1.12 (0.71)
0.02 (0.01)
97.2 (0.51)
(3.42)
(0.55)
(0.06)
(0.04)
(4.06)
20% RDF
1.85 (1.21)
0.21 (0.12)
0.34 (0.08)
0.02 (0.01)
97.7 (1. 41)
a Values in parentheses are ± one standard deviation
TABL E 8 ANALYSIS OF FLY ASH FROM BOILER UNIT 7
Prior to Installation of Dump Grate 1976, 1977
Parameter 60% Load 80% Load 100% Load
(%) 0% RDF 0% RDF 0% RDF 10% RDF
Carbon 0.79 (0.19) 0.95 (0.27) 1.87 (1.15) 4.68 (0.43) Hydrogen 0.27 (0.08) 0.60 (0.25) 0.61 (0.28) 0.07 (0.02) Sulfur 1. 52 (0.25 ) 1. 35 (0.28) 1. 35 (0.18) 1.02 (0.12) Chlorine 0.00 (0.00) 0.00 (0.00) 0.01 (0.02) 0.00 (0.00) Mineral 97.4 (0.47) 97.1 (0.57) 96.2 (1. 47) 94.2 (0.57)
After Installation of Dump Grate 1978
80% Load 100% Load
0% RDF 10% RDF 20% RDF 0% RDF 10% RDF 20% RDF
Carbon 1.85 (0.55) 2.43 (0.35) 2.54 (0.05) 1. 92 (0.78) 2.41 (0.49) 2.40 (0.40) Hydrogen 0.10 (0.02) 0.11 (0.01) 0.17 (0.05) 0.10 (0.02) 0.11 (0.01) 0.11 (0.02) S ulfur 0.70 (0.34) 0.69 (0.13) 0.86 (0.14) 1.02 (0.51) 0.82 (0.21) 0.83 (0.13) Chlorine 0.01 (0.01) 0.01 (0.00) 0.03 (0.01) 0.01 (0.01) 0.02 (0.01) 0.02 (0.01) Mineral 97.3 (0.55) 96.8 (0.46) 96.4 (0.09) 97.0 (0.39) 96.6 (0.59) 96.6 (0.30)
a Values in parentheses are + one standard deviation
506
tional carbon remaining in the RDF which had dropped into the bottom hopper of the boiler.
Further analysis of th6 samples of RDF indicated that the ash fusion temperatures were from 60-lODe lower than those for coal. The RDF also has a high sodium content which had a significant detrimental effect on fouling index as compared to burning coal only. Thus some difficulty wi th slagging and fouling was anticipated and observed during these tests.
EMISSIONS
Results for the major effluents of interest from the emission tests are presented in Table 9. Each number tabulated in Table 9 represents the average of three ind�pendent runs unless otherwise noted. The standard deviations are also given in Table 9 as the values within parentheses. Standard deviations are measures of the variations in the experimental results caused by the uncontrolled factors in the experiment as well as uncertainties in the experimental measurements and the analytical analyses.
PARTICULATES
The variations of the uncontrolled particulates, controlled particulates and electrostatic precipitator efficiency with RDF are shown in Fig. 5, 6 and 7 respectively. From Fig. 5 it can be observed that the uncontrolled emissions generally increase with RDF except for the 100 percent load data using coal only. Otherwise all the runs show Significant increases in particulate emissions as the amount of refuse derived fuel increases to the steam generator. It is also apparent from this plot that the initial data obtained using coal only in this boiler in 1976 and 1977 indicates a reverse trend in terms of particulate emissions. The expected particulate would be higher at 100 percent load than at 60 percent load as was the case for the 1978 data. The reason for this reversed trend in the 1976 . data is believed to be related to difficulties noticed in operation of the particulate collector on Unit 7 during 1976 and 1977. The precipitator was extensively repaired between the 1976/77 experiments and the 1978 experiments. However, it should be emphasized that the scale for the emissions is
TABLE 9 SELECTED EMISSIONS FROM BOILER UNIT 7
Prior to Installation of Dump Grates 1976, 1977
Parameter Units 60% Load 80% Load 100% Load .
0% RDF 0% RDF 0% RDF 10% RDF
Particulates lb/l06
BTUb
(controlled) lb/l0
6BTU Particulates
(uncontrolled) lb/l0
6BTU Oxides of Sulfur
SOx 6
Oxides of Nitrogen lb/IO BTU NOx
lb/lO�BTU Chlorides Formaldehyde lb/l0
9BTU
Methane lb/IO BTU
0.23
9.05
2.61
0.32
5.14 4.56 0.00
(0.07)a
0.35 (0.12) 0.60 (0.09) 0.53 (0.12)
(1. 02) 7.49 (1.72) 8.26 (0.05) 8.35 (0.30)
(0.40) 2.88 (0.70) 3.70 (0.16) 2.88 (1.l4 )
(0.03) 0.26 (0.09) 0.35 (0.02) 0.27 (0.04)
(3.75) 13 .6 (8.42) 28.14 (6.91) 7.65 (5.05) (5.58) 20.9 (44.0) 5.49 (4.58) 60.0 (52.6) (O.OO) 0.00 (O.OO) 0.00 (O.OO) 0.00 (O.OO)
---- ----------------- ------------------------ - ---- -----------------------------------------------------------
Parameter Units
Particulates lb/l06
BTU (controlled)
lb/l06
BTU Particulates (uncontrolled)
lb/l06
BTU Oxides of Sulfur SOx
6 Oxides of Nitrogen lb/IO BTU
NOx lb/lO�BTU Chlorides
Formaldehyde lb/l09
BTU Methane Ib/10 BTU
After
0% RDF
0.21 (0.05)
6.54 (1. 33)
3.42 (0.14)
0.39 (0.02)
10.7 (1. 77) 8.37 (14.0) 5.30 (2.65)
Installation of Dump Grates
80% Load
10% RDF 20% RDF
0.37 (0.09) 0.37 (0.07)
7.63 (0.63) 8.21 (1.21)
2.84 (0.16) 2.33 (0.63)
0.33 (0.02) 0.33 (O. 03)
50.9 (35.8) 93.7 (8. 96) 12. (207.) 0.77 (0.42) 6.07 (1. 58) 3.77 (0.30)
a values in parentheses are + one standard deviation
1978
100% Load
0% RDF 10% RDF
0.42 (0.2l) 0.44 (0.07)
7.93 (3.58 ) 7.28 (0.53) .
3.30 (2.07) 2.33 (0.49)
0.31 (0.04) 0.26 (0.01)
7.65 (1. 88) 58.4 (31. 9) 0.19 (O. 33) 1.44 (O. 72) 3.35 (0.93) 4.58 (1.44 )
b 6 ' to convert from Ib/10 BTU to micrograms/Joule, multiply values in the above table by 0.430
507
20% RDF
0.53 (0.09)
7.47 (0.53)
1.93 (0.5l)
0.26 (0.03)
28.6 (9.35) 0.42 (0.19) 2.47 (0.58)
4.00,--------------------, EFFECT OF RDF ON UNCONTROLLED EMISSIONS
3.80
3.60
� 3.4 .... � �
•
�
� -
� � - 3.10 '" w
" w � �
Ii! ...
� 3.00 u
!5 o '" 60 PERCENT LOAO D '" 80 PERCENT LOAD c. '" 100 PERCENT LOAD
OPEN SYM80L '" 1978 DATA SHADED SYMBOL", 1976 OR 1977 DATA
1.8
1.60 '-__ -'-__ -" ___ ,.L-__ -,J-___ ,L-...J o 4 8 11 16 10
REFUSE DERIVED FUEL HEAT INPUT. PERCENT
FIG.5 UNCONTROLLED PARTICULATE EMISSIONS
:::
o EFFECT OF RDF ON CONTROLLED EMISSIONS
0." r-
0.10 1-
L------"" 0.1
g:' 0.16 •
�
i!j 0.14 -� '" -
� 0.12 " w � �
li! o. ...
8 0.08
0.06
0.04
0.01
o '" 60 PERCENT LOAD D '" 80 PERCENT LOAD c. '" 100 PERCENT LOAD
OPEN SYMBOL'" 1978 DATA SHADED DYMBDL '" 1976 or 1977 DATA FLAGGED SYMBOL'" 1978 DATA AFTER RELOCATION OF RDF NOZZLE
O.OO !,-__ --:-__ -!: ___ ""=-__ -,! ___ -:! o 4 B 1
REFUSE DERIVED FUEL HEAT INPUT. PERCENT
FIG.6 CONTROLLED PARTICULATE EMISSIONS
98.0,---------------------,
97.0
96.0
� u z w -u -
t:: 95.0 w
� " ... u w � � "
u 94.0
93.0
91.0
o '" 60 PERCENT LOAD D '" 80 PERCENT LOAD c. '" 1 00 PERCENT LOAD
OPEN SYMBOL'" 1978 DATA SHADED SYMBOL", 1976. 1977 DATA
91.0 �--+--_!:__--_;';;_--_;';,_--f.:__J o 4 8 11 16 10
REFUSE DERIVED FUEL HEAT INPUT. PERCENT
FIG. 7 ELECTROSTATIC PRECIPITATOR EFFICIENCY
significantly expanded and that all the emissions with the 100 percent coal as the only fuel are within 2.8 to 3.9 mg/J of heat energy input.
The controlled emissions generally increase with increases in RDF. This result was expected since the amount of ash in the RDF was proportionally larger than that of the coal. For the 100 percent coal runs (0 percent RDF) the decrease in the emissions at 8 0 and 100 percent load for the 1978 data is a result of repair of the electrostatic precipitator which occurred late in 1977. Difficulty was experienced with the electrostatic
. precipitator during 1976 and 1977 because some of the plate retainers in the precipitator had failed, rendering some of the precipitator plates to be ineffective during the test runs accomplished in 1976 and 1977. This is one reason why the emissions for the 60, 8 0 and 100 percent load in 1976 and 1977 appear to be Significantly higher than
508
the emissions for the corresponding loads in 1978. Thus, the data obtained in 1978 is much more representative for the usual performance of Unit 7. Furthermore, the data of 1978 show very consistent trends in the direction anticipated based on the fuel input analysis.
At 100 percent load additional runs were made in 1978 for Iowa Department of Environmental Quality compliance checks with federal and state regulations. Some of these runs were accomplish-
ed after the location of the RDF injection point was placed below that of the coal injection nozzles in the boiler. The specific locations of the coal nozzles were at both the 1 32.5 and 1 29 .2 ft (43 .7 and 42 .6m) level while the RDF was injected at the 1 27 . 1 ft. (42 m) level. For comparison the dump grate level in the boiler was at the 1 00.5 ft. (33 .2 m) level so the suspension zone for the RDF was slightly less than 27 ft . (8.9 m). The RDF injection point for the emission data presented in Fig. 6 is all with the RDF injection point located between the two coal nozzles except for the runs where the data point plotted is flagged. The importance of the location of the RDF injection point is dramatically shown in Fig. 6 and indicates that the particulate emissions can be reduced significantly by the proper location of the RDF injection point.
It should also be noted that the particulate matter collected during the runs with RDF often contained several pieces of black flaky material which had passed through the electrostatic precipitator and into the sample trains used for collection of particulate matter. The black flaky substance would stick to sides of houses and automobiles and was quite disconcerting to several citizens who forwarded complaints. Relocation of the RDF injection point in the boiler eliminated the problem almost completely as well as lowering significantly the particulate effluent from the smokestack . Lowering of the amount of particulate effluent from the smokestack because of the relocation of the RDF injection point resulted in the Iowa Department of Environmental Quality not applying emission offsets to the operation of boiler Units 5 and 6 at the Ames Power Plant.
The effect of RDF on the electrostatic precipitator collector efficiency is shown in Fig. 7 . From this figure it is clear that the efficiency drops consistently with increases in RDF. These trends are very consistent for the data obtained in 1 978 and showed the electrost�tic precipitator efficiency to be higher at 80 percent load than at 1 00 percent load. The effect of the repair between 1 977 and 1 978 data is also apparent in this figure . For example, for the coal only runs, the collector efficiency changed from 93.4 - 94.4 percent efficiency at 1 00 percent load. At the 80 percent load the efficiency increased from 94.9 - 96.8 percent thus demonstrating the dynamic effect the repair of the precipitator had on its performance .
Figs. 8 and 9 show the particulate size distribution as determined via an Andersen cascade impactor for the 80 and 1 00 percent load runs.
From these figures it is apparent that at 1 00 percent load the sizes for coal only, 1 0 and 20 percent RDF are all about the same. At 80 percent load the differences were significant. From these figures it is apparent that particle size increases with increases in RDF.
Figures 1 0 and 1 1 show the particulate size distribution at the collector inlet and in the stack determined by a Brinks cascade impactor. Comparison of these two figures reveals the size distribution retained by the electrostatic precipitator. The Brinks and Andersen size distribution results for the stack particulate do not agree because the sampling probes and calibrations are different for each type of cascade impactor. Thus, comparisons can only be made in a relative rather than an absolute sense and only for a given type of cascade impactor.
OXIDES OF SULFUR
The oxides of sulfur (SOx) emitted from the boiler decrease significantly with increases in RDF as shown in Fig. 1 2 . This decrease amounted to about 50 percent for boiler loads of both 80 percent and 1 00 percent in going from 0 to 20 percent RDF. Thus, an advantage of using RDF with coal is that relatively high sulfur coal can be used while still meeting EPA regulations.
100.0,-----------------,
10.0 ...----10% ROF
CUMMULATl VE PCT LESS THAN 050 FIG. 8 PARTICULATE SIZE DISTRIBUTION FOR
80 PERCENT LOAD
509
V> % 0 '" u -:IE:
0 �
0
� N -V>
� -' u -... '" « �
100.0.-----------------------------------------,
10.0
20% ROF
1.0
10% RDF
PARTICLE SIZING 100% LOAD UNIT 7 ANDERSEN 1978
O� ROF
0.1L-_����������� -���-=_� 2 5 10 15 20 30 40 50 60 70 80 85 90 95 98
CUMMULATIVE PERCENT LESS THAN D50
FIG.9 PARTICULATE SIZE DISTRIBUTION FOR 100 PERCENT LOAD
V>
i5 '" u -:IE:
0 �
0
W N -V>
w -' u -
:;; « �
1DO.OI,----------------------
1D.0
1.0
PARTICLE SIZING UNIT 7 100% LOAD 1978 8RINKS BPC
0% RDF
10% RDF
0.1L-__ ����������������--��� 2 5 10 15 20 30 40 50 60 70 80 85 90 95 98
CUMULATIVE PCT LESS THAN D50
FIG. 10 PARTICULATE SIZE DISTRIBUTION AT THE COLLECTOR
V> %
51 u -:IE:
0 �
0
� N -V>
� -' u -... '" « �
.,
100.0,.----------------------,
0% RDF ___ ..,..",/ 10.0 ./'"" ... 2D% RDF
10% RDF
PARTICLE SIZING UNIT 7 100% LOAD 1978 8RINKS STACK
O. 1 '=---;L--,l;;�,...f.,.......,f;;_-+.::-t;,,._7.;_;�+n_.f<-+n-*""� 2 5 1 0 15 20 30 40 50 60 70 80 85 90 95 98
CUMMULATIVE PCT LESS THAN D50 .
FIG.11 PARTICULATE SIZE DISTRIBUTION IN THE STACK
1.6K----------------,
EFFECT OF RDf ON SOx EMISSIONS
1.2
1.0
..... 0> "-
•
V> i5 0.8 -V> o '" 60 PERCENT LOAD V>
o '" 80 PERCENT LOAD -:IE:
o '" 100 PERCENT LOAD w
• OPEN SYM80L '" 1978 DATA fii 0.6 SHADED SYIIlOL '" 1976 or 1977 DATA
0.4
0.2
0.0 '--___ '--___ '--__ ---,'::-__ --,'--__ ---''--' o 4 8 12 16 20
REFUSE DERIVED FUEL HEAT INPUT, PERCENT
FIG.12 OXIDES OF SULFUR EMISSIONS
510
OXIDES OF NI TROGEN
The oxides of nitrogen (NOx) generally decrease with increases in RDF at all boiler loads as shown in Fig. 1 3 . The decrease was generally in the range of 1 0 to 20 percent and somewhat dependent on boiler load as the RDF was increased up to 20 percent. The NOx emissions generally decreased less for the 1 978 data than for the 1 976-1 977 data. This may represent better operation of the boilers and better control of the combustion zone temperatures for the experimental runs of 1 978.
..., ...... Ol ::>.
vi z: 8 In In ::E ....
x 0 z:
0 . 1 8
0 . 1 6
0 . 1 4
0 . 1 2
0 . 1 0
0 . 08
0 .06
0 . 04
0 . 02
EFFECT OF RDF ON NOx
E M I SS I ONS
BOILER UN IT 7
o '" 60 PERCENT LOAD o '" 80 P E RCENT LOAD {). '" 1 00 PERCENT LOAD
OPEN SYMBOL ", 1 978 DATA SHADED SYMBOL ", 1 976 OR 1 977 DATA
O. DO '=-_ __,!---�-__::';;_-___::':_-__,� o
REFUSE DERI VED FUEL H EAT I N PUT . PERCENT
FIG. 1 3 OXI DES OF NITROGEN EMISSIONS
CHLORIDES
The chloride emissions for the suspension fired boiler increased linearly and significantly with increases in RDF as shown in Fig. 14 except for the 1 00 percent load, 20 percent RDF data point. The boiler experienced as much as a 1 0 fold increase in chloride emissions as the RDF increased from 0-20 percent for all boiler loads in 1 978. The chlorides in the stack emissions are believed to come
5 1 1
from the chlorinated hydrocarbons in the RDF. The chlorides drop for the 1 976- 1977 data because of the dropout of RDF into the bottom hopper since the bottom grates were not installed at this time.
..., ...... Ol c
vi z: 8 In In ;: .... .... c
;:;: a ...J ::t: U
40 .0
3 5 . 0
30 .0
2 5 . 0
2 0 . 0
1 5 . 0
EFFECT O F RDF ON CHLORIDE E M I S S I ONS
o '" 60 P E RCENT LOAD o '" BO PERCENT LOAD {). '" 1 00 PERCENT LOAD
OPEN SYMBOL '" 1 978 DATA SHADED DYMBOL '" 1 976 . 1 977 DATA
D . O � __ L-__ L-_�� __ � __ � o 4 8 1 2 1 6 20
REFUSE DERIVED FUEL H EAT INPUT . PERCENT
FIG. 1 4 C HLORI DE EMISSIONS
A L DEH YDES A ND KETONES
No conclusive trends concerning aldehydes and ketones (reported as formaldehyde) emissions could be observed as illustrated in Fig. 1 5 . Formaldehyde emissions depend on the constituents of the RDF such as wood chips, leaves and other cellulose fiber. No control of the quantity of these items in the RDF was attempted. Consequently the emissions due to the burning of cellulose fiber were as variable as the constituency of the RDF.
METHANE
The unburned (C1 ) hydrocarbons (methane) emitted from the stack increased and then decreased as the RDF increased to 1 0-20 percent respectively as shown in Fig. 1 6. The level of methane detected is very low as was expected.
60
50
o "" 60 PERCENT LOAO o ... 80 PERCENT LOAO " 0, 100 PERCENT LOAO
OPEN SYMBOL ; AFTER INSTALLATION OF 01M' GRATES , 197B
HADED SYMBOL ; BEFORE I NSTALLAT ION OF OUMP GRATE . 1 9 7 6 , 1 977
? 40
30
20
1 0 EFFECT O F REFUSE DERIVEO FUEL ON ALOEHYOE AND KETONE EMISSIONS ANALYSEO ANO REPORTEO AS FORMALDEHYDE
0�0----�======�====�1�2�==�16====�2�0� REFUSE OERIVED FUEL HEAT INPUT, PERCENT
FIG, 1 5 ALDEHYDE AND KETONE E M ISSIONS
2 . Br-------�------�---, EFFECT OF RDF ON METHANE EMISSIONS
2 . 0
1 . 6
� 1 . 2 o "" 60 PERCENT LOAD o ... 80 PERCENT LOAO " "" 100 PERCENT LOAD
OPEN SYt'80L "" 197B DATA � SHADED SYMBOL "" 1976 OR 1977 OATA
! O . B
0 . 4
0 . 0��==t=====!===:'---},----.,J;.-------,!;� REFUSE DERIVEO FUEL HEAT INPUT . PERCENT
FIG, 1 6 M ET HANE EMISSIONS
TRA CE ELEMENTS
A series of 1 9 trace elements were sampled from all input and all output streams associated with the operation of steam generator Unit 7 , Table 1 0 lists the trace elements detected in the input fuels of coal and RDF used during the test of this particular study, The elements selected for analysis are
5 1 2
listed by rank order in Table 1 0 where the ranking had been determined by the concentration given in parts per million, In addition the standard deviations which go along with the average concentrations are also listed , Another column in Table 1 0 also shows the amount o f the trace element listed on the basis of mass per unit of energy input to the boiler. The values listed in Table 1 0 are overall averages for both the coal and RDF used during tests performed in 1 978. The trace elements with higher proportions of concentration in coal as compared with RDF are also identified in this table as strontium, beryllium, nickel and germanium. The elements that were not detected based on the detection limit of the analytical instrumentation are also indicated in this table. Elements relatively high in concentration in the RDF are shown in Table 1 0 to be zinc, lead, copper, manganese and vanadium.
Table 1 1 lists the trace elements detected in the bottom ash , hopper ash (fly ash) , and particulate matter collected on a fIlter in the sampling train located in the smokestack of Unit 7 . These elements are listed in rank order based on mass of the element per unit of energy input to the boiler in this particular table. The detection limits of the x-ray fluorescence device used to analyze for trace elements in the solid materials collected in the output stream samples is also indicated in Table 1 1 . These numbers are in units of parts per million by weight of the element , except for the stack fIlters which are given in units of micrograms per square centimeter of area over which the particulate is collected on the fIlter. Trace elements of relatively high concentration in the fly ash are zinc, lead, manganese , vanadium and strontium. These elements along with nickel, copper and chromium are high in relative concentration in the bottom ash.
These tables are presented so that a comparison can be made with the trace elements scanned in the input fuels. If mass balances are desired , the quantity coming in with the input fuel minus the amount of the individual trace element in the bottom ash minus the amount of the individual amount in the fly ash collected in the electrostatic precipitator hopper would give an estimate of the amount of the element leaving the smokestack of the boiler.
Trace elements were also analyzed from the particulates collected in the smokestack and from sampling train impinger solutions to yield additional estimates of the trace elements that were
emitted from the boiler stack. However, these estimates are not as reliable as the estimates found by taking what comes in with the input fuel and subtracting what drops out with both the bot· tom grate ash and the hopper fly ash : Some mass balances have been attempted but are not present· ed here because some of the resulting balances are inconsistent due to the low constituent levels, sampling uncertainty, and analytical uncertainty. Sometimes the uncertainties accumulate to the point where attempts at mass balances yield nega· tive quantities leaving the smokestack. TItis does not mean that there is an accumulation of such a
material in the boiler or in the generating system but is simply an indication that there are un· controlled factors in the experiment which cause variation in the data, that there are experimental errors in the measurements, and that there is error in the analysis of the samples. A combination of the variability due to the uncontrolled factors, the experimental error, the analytical error and the analytical detection limits often overshadow the small amount of the trace element actually in the system. This is especially evident when the average values of the trace elements for a given load and percent RDF are ,.relatively small .
TABLE 1 0 TRACE ELEM ENT CONTENT OF COAL AND RDF USED AS FUEL IN UNIT 7
COAL RDF
Element Level* Element Leve l *
ppm ng/J ppm
S t ront ium** 86 + 2 8 2 . 9 2 + 1 . 15 Zinc 7 6 3 + 345 - - -
Vanadium 83 + 16 2 . 9 2 + . 5 2 Lead 6 1 3 + 289 - - -
Manganese 76 + 2 3 2 . 6 7 + . 79 Copper 5 7 2 + 854 - -
Zinc 66 + 4 1 2 . 39 + 1 . 46 Mangane se 194 + 4 7 -- - -
Beryllium** 37 + 1 2 1 . 55 + 0 . 49 Vanadium 154 + 32 - - -
Lead 36 + 1 3 1 . 26 + . 48 S t ront ium 46 + 1 1 - - -
Tin 20 + 5 0 . 7 1 + . 1 7 Chromium 34 + 8 - - -
Chromium 19 + 7 0 . 74 + . 35 Tin 27 + 8 - - -
Nickel** 18 + 5 0 _ 6 3 + . 1 7 Ant imony 25 + 1 7 - - -
Copper 15 + 3 0 . 52 + 0 . 0 8 Gallium 16 + 3 - - -
Germanium** 5 . 3 + 0 . 9 0 _ 19 + 0 . 04 Nickel 14 + 4 - -
Gall ium 2 . 5 + 0 . 5 0 . 09 + 0 . 0 2 Selenium 8 + 1 - - -
Ant imony BDL+ BDL Cadmium 6 . 4 + 8 . 1 -
Selenium BDL BDL Germanium 1 . 7 + 0 _ 3 -
Thal l ium BDL BDL Thall ium BDL
Mercury BDL BDL Mercury BDL
Arsenic BtL BDL Arsenic BDL
Cadmium BDL BDL Beryll ium BDt
Cobalt BDL BDL Cobal t BDL
* Values listed are overall averages for the coal and RDF used during 1978 tests .
** Trace elements with higher proportions in coal than in RDF
+ BDL s ignifies the element is b elow the analyt ical instrumentat ion det ect ion l imi t .
5 1 3
ng/J
4 . 65 + 2 . 1 3 -
3 . 89 + 2 . 27 -
3 . 58 + 5 . 74 -
1 . 18 + 0 . 33 -
0 . 94 + 0 . 19 -
0 . 28 + 0 . 04 -
0 . 28 + 0 . 04 -
0 . 1 7 + 0 . 06 -
0 . 15 ' + 0 . 11 -
0 . 10 + 0 . 0 2 -
0 . 09 + 0 . 03 -
0 . 05 + 0 . 01 -
0 . 04 + 0 . 05 -
0 . 01 + 0 . 00 -
B DL
BDL
BDL
BDL
BDL
Vl
.....
.j:>.
TA
BL
E 1
1
TR
AC
E E
LE
ME
NT
CO
NT
EN
T O
F B
OT
TO
M A
SH
, H
OP
PE
R F
LY
AS
H A
ND
ST
AC
K F
LY
AS
H
-
Elem
ent '"
(O
P.tec
t ion
Ll
::)its
) PP
M'"
Chro
miu
m
(100
)
Hang
;t.nes
e (7
0)
Zinc
(2
0)
Lead
(2
5)
Nick
el
(20)
Copp
er
(20)
Vana
dium
(2
00)
Stro
ntiu
m (5
) Ga
lliu
m
(10)
Ti
n --
-
Bery
llium
(1
0)
Ant i
mony
--
-
Sele
nium
(5
) Th
all i
um
---
Germ
aniu
m
(10)
He
rcur
y --
-
Arse
nic
(to)
Ca
dmiu
m -
-
Coba
lt
(30)
Bott
om A
sh
Leve
l .
Hax
Max
PPM
ng
/J
2450
5.
62
1200
2.
66
1680
2
.62
1240
1.
68
680
1.5
6
910
1.4'
>
660
1.3
3
750
1.0
3
320
0.58
160
0.1
1
120
0.0
13
230
0.4
36
BOL
BOL
BOL
BOL
.BOL
BO
L
BOL
BOL
BOL
BOL
BOL
BOL
BOL
BOL
Elem
ent·
Av
g ±
Std
!lev
og/J
0.9
13 +
1.4
0 Zi
nc
0.9
50 ±
.80
5.
Hang
anes
e
0.9
64 ±
0.7
90
Lead
0.6
34 ±
0.5
34
Vana
dium
0.2
61 ±
0.3
87
Stro
ntium
0.4
)) ±
0.4
42
Chro
miu
m
0.4
48 ±
0.3
61
Copp
er
0.3
59 ±
0.2
74
Nick
el
0.0
55 ±
0.1
33
Call
ium
0.0
34 ±
0.0
34
Germ
aniu
m
0.0
11 ±
0.0
02
Tin
0.0
96 ±
0.1
17
Bery
lliu
m
BOL
Cadm
ium
BOL
Anti
mony
BOL
Sele
niu
m
BOL
Thal
lium
BOL
Mer
cury
BOL
Ars
enic
BOL
Coba
lt
'" De
tect
ion
11.mIt
s fo
r Bo
ttom
Ash
and
Hopp
er A
sh a
re t
he s
ame
Max
PPM
2250
132
0
1640
1030
1130
404
218
140 86
51
59
120 11
92
BOL
BOL
BOL
BOL
BOL
Hopp
er A
sh
Part
icul
ate
00
St
ack.
Fil
ters
Leve
l lU
emen
t (De
tect
ion
Leve
l Ma
x --
Avg
+ St
d IJe
v Li
mit
s)
I' .. x
Max --"
vg ±
Std
Oev
ng
/J
fiR/J
Mg
/cm
2 lf
g/cm
2 pg
/J
pg/J
10.7
4 4
.717
+ 2
.428
Zi
nc
(0.2
) 82
12
5:0
35.3
5 ±
26.
26
5.8
0 3.
469
+ 1.
178
Lead
(1
) )0
37
:4
18.9
4 ±
13.
19
5.76
2.
994
+ 1
.849
Va
nadi
um
(1)
8 11
.0
7.00
± 1
.44
3.67
2
.744
+ 0
.623
St
ront
luo
(0.1
) 10
D
.7
6.6
6 ±
2.4
0
3.)
) 2
.296
+ 0
.600
Ma
ngan
es.:!
(0.5
) 10
10
,/t
5.4
6 ±
2.1
1
1.44
0
.861
± 0
.259
Ce
rma�l
u",
(0.4
) 1
.7
2.5
9 1
.39
±0
.54
.759
0
.417
+ 0
.189
Co
pper
(0
.2)
2.6
2.69
D
.5±
0.5
8 .4
70
0.3
06 +
0.0
84
Chro
miu
m
(0.5
) 1.
6 2
.43
1.3
3 ±
0.5
5 .3
30
0.1
72 +
0.0
83
Gall
ium
(0
.4)
1 .5
2.2
8 1
.31
± 0
.67
.248
0
.126
+ 0
.039
N
icke
l (0
.3)
1.2
1.6
5 1.
24 ±
0.4
8
.200
0
.096
± 0
.068
Se
len
ium
(0.2
) <0
. 5
0.'7
9 0
.43
± 0
.15
0.3
1 0
.249
+ 0
.057
A
rsen
ic
(0.2
) 80
L BO
L BO
L
0.0
5 0
.019
± 0
.015
Be
ry 1 l
1U"ll
--N
.A.
N.A
. N
.A.
0.3
0 0
.139
+0
.116
Ca
dmiu
m
---
BOL
BOL
BOL
BOL
BOL
Cob
alt
(0.4
) nO
L BO
L BO
L
BOL
BOL
Merc
ury
---
BOL
BOL
BOL
BOL
BOL
Anti
mony
--
BOL
BOL
BOL
BOL
BOL
Tin
---
BOl
BOL
BOL
BOL
BOL
Thal
lium
--
DOL
BOL
BOL
Table 1 2 is the listing of the trace elements detected in the exhaust gas stream from smokestack of Unit ·7 . The particular trace elements have been condensed or collected in the solutions in two different sample trains. One solution used was water in the particulate sample train where the flow rate through the train was relatively high at a value of about 0.2 Lis. The other sample train was the "trace element" sample train where the flow rate through the train was relatively low at a value of about 0.02 Lis . The various flow rates through these trains have been previously indicated in Table 4. The solution in the particulate train was water whereas the solutions in the trace elements train were sodium hydroxide (located in an impringer used as a prescrubber in a sample train) followed by two impingers which contained iodine monochloride . The analysis of the trace elements used in this particular sample train have been combined to include the total amount collected in the sodium hydroxide prescrubber and both of the iodine monochloride impingers. All of the trace elements found in the solution of the sample
trains have been analyzed by the Inductively Coupled Plasma technique (ICP). The only elements jointly detected in the impinger solutions of both sample trains were cobalt and arsenic. However, other elements consistently detected were mercury, selenium, zinc, copper, manganese and tin .
Table 1 3 is a listing of trace elements detected in the sluice water which was the water used to sluice the bottom ash from the bottom pit of boiler Unit 7. This sluiced material then passes through a pipeline for approximately 1 300 ft. C 400 m) to an ash pond where the sluice water samples and bottom ash samples were collected by the Fiscus-Joensen technique . The levels of strontium, antimony, arsenic and mercury were at the highest relative levels and all at values less than 0 .4 mg/L.
Table 14 is a listing of th.e trends of the trace elements that are in the output streams as they either increase, decrease or remain constant with respect to the amount of refuse derived fuel coming in with the input fuel . The plus signs in the
TABLE 1 2 TRACE E LEMENTS COND ENSED OR ABSORBED IN I MP I NGER SOLUT I ONS OF
SAMPLE TRAINS
Trace Element Sample Train ( Impinger ICL) Particulate Sample Train ( Impinger H2O)
Element (Detection* Level Element (Detection* Level Limit) ICL Max Max Ave + Std Dev Limit) Max Max Ave + Std Dev Mg/! Mg/l pg/J pg/J Mg/I Mg/I pg/J pg/J
Cobalt 0 . 0 5 0 . 284 1 741 234 + 403 Cobalt 0 . 002 0 . 19 3 14 . 9 3 . 18 + 4 . 06
Arsenic 0. 40 <0. 400 9 4 3 3 8 5 + 208 Mercury 0. 10 0 . 29 9 14 . 7 4 . 46 + 3 . 04
Zinc 0 . 02 0 . 6 1 7 2 3 3 70 . 6 + 5 5 . 4 Arsenic 0 . 05 0 . 082 8 . 00 5 . 26 + 1. 21
Copper 0 . 01 0 . 09 5 5 5 . 0 2 5 . 6 + 21 . 9 Selenium 0 . 0 4 0 . 060 5 . 7 8 3 . 81 + 0 . 9 8
Manganese 0 . 004 0. 136 45. 3 9 . 5 + 10 . 6 Tin 0 . 04 0 . 2 70 5 . 60 4 . 07 + 0 . 8 7
Beryllium 0 . 001 BDL** BDL BDL Beryllium 0 . 00005 BDL BDL BOL
Cadmium 0 . 10 BDL BDL BDL Cadmium 0. 003 BDL BDL BDL
Chromium 0 . 08 BDL BDL BDL Chromium 0 . 00 3 BDL BDL BDL
Gallium 0 . 2 3 BDL BOL BDL Copper 0. 0005 BDL BDL BDL
Germanium 0 . 30 BDL BDL BDL Gallium 0 . 01 BDL BDL BDL
Mercury 0. 22 BDL BDL BDL Germanium 0 . 01 8DL BDL BDL
Nickel 0 . 1 7 BDL BDL BDL Manganese 0 . 001 BDL BDL BDL
Lead 1 . 80 BDL BDL BDL Nickel 0 . 0 7 BDL BDL BDL
Antimony 0 . 4 2 BDL BDL BDL Lead 0 . 05 BDL BDL BDL
Selemium 0 . 63 BDL BDL BDL Tin 0 . 025 BOL BDL BOL
Tin 0 . 2 3 BDL BDL BDL Stront ium 0 . 0 2 BDL BOL BDL
Strontium 0 . 28 BDL BDL BDL Thallium 0 . 1 BDL BDL BDL
Thallium 7 . 5 BDL BDL BDL Vanadium 0 . 004 BDL BDL BDL
Vanadium 0 . 06 BDL BDL BDL Zinc 0 . 0 2 BDL BDL BDL
* Detec t ion limit of the primary chemical, ICL is given
** BDL indicates below the analyt ical instrument detection limit
5 1 5
table indicate an increase of the trace element with increased amounts of RDF used in the input fuel, whereas the negative sign indicates a decrease in the amount of trace elements with respect in RDF in the input fuel . A zero indicates no detectable trend within the data scatter. Those elements detected in the stack effluent consistently increasing with increases in RDF were manganese , zinc, lead, copper, gallium and chromium.
Table 1 5 lists the estimated trace elements in the ambient air in terms of a stack gas concentration given in units of milligrams per cubic meter (mg/m3) of stack gas. An estimate of the concentration of the element in the ambient air is obtained from the flue gas concentration by dividing the flue gas concentration by a factor of 1 ,000 to yield the ambient air estimate of the element concentration. The estimate of the ambient air concentration is then compared to the threshold limit value (TL V) of the element as given in Reference [8] . The ratio of the estimated ambient air concentration to the threshold limit value has been listed in this table to approximate the relative toxicity of the element scanned ·during the particular tests of this study. Finally, a comparison is
TABLE 1 3 TRACE E LEMENTS DETECTED IN
BOILER SLUICE WATER
Element (Detection Blank Max Ave + Std Oev Limit ) Level Value Value !lglJ mg/l mg/l mgIJ
Strontium 0 . 07 0 . 271 0 . 372 0 . 267 ± 0 . 047
Ant imony 0 . 025 BOL 0 . 233 0 . 069 ± 0 . 061
Arsenic 0 . 05 0 . 083 0 . 100 0 . 074 ± O . OlB
Mercury 0 . 035 0 . 042 0 . 05 0 . 041 ± 0 . 01 7
Manganese 0 . 001 0 . 212 0 . 04 0 . 008 ± 0 . 013
Copper 0 . 0005 BOL 0 . 04 0 . 004 ± 0 . 010
Chromium 0 . 003 BDL 0 . 02 0 . 006 + 0 . 005
Vanadium 0 . 004 BDL 0 . 01 0 . 006 ± 0 . 002
Cobalt 0 . 00 2 0 . 010 0 . 0 1 0 . 003 + 0 . 002
Beryllium 0 . 0005 BOL BOL BOL
Cadmium 0 . 003 BOL BOL BOL
Gallium 0 . 01 BOL BOL BOL
Nickel 0 . 0 7 BOL BOL BOL
Lead 0 . 05 BOL BOL BOL
Selenium 0 . 04 BOL BOL BOL
Tin 0 . 04 BOL BOL BOL
Zinc 0 . 02 BOL BOL BOL
Tha111wn 0 . 10 BOL BOL BDL
Germanium 0 . 01 BOL �DL BOL
made between the data of this study and the predictions listed in Reference [9] from the 8t. Louis data. From the 8t . Louis study it was predicted thaCchromium ( 1 0 .2), copper (7.4), lead (3 .7) and zinc ( 1 .2) would be above the TLY and of relative Significance in the order given. None of the trace elements detected on the stack particulate train filters during these studies have predicted ambient air concentration above the TLY although lead is at a level near 30 percent of the TLY. However, from the trace element sampling train cobalt (5 .3) and arsenic ( 1 .7) are indicated to be above the TLY for the Ames study.
MINOR ELEMENTS
Table 1 6 lists the minor constituents (elements) found in the coal, RDF, bottom ash and fly ash for the 1 978 test runs on Unit 7. The elements listed are aluminum, silicone, sulfur, potassium, calcium, iron and titanium.
FUEL ENRICHMENT FACTORS
Figures 1 7 and 1 8 are plots of fuel enrichment factors of the trace elements to show the relative importance of RDF in causing increased emissions of the particular trace elements scanned in this study. From these figures the elemen ts of zinc, copper, and lead have Significant increases with RDF over coal alone'. Gallium increases slightly with RDF. The reason for copper being relatively high at 1 2 percent RDF and then dropping at 22 percent RDF is not known at the present time. Zinc comes into the RDF from paper where it is used as a fllier material. Lead and copper come . into the RDF from inks used in newsprint and colored pictures. The gallium is felt to be an impurity that comes into the RDF along with another element such as aluminum.
The fuel enrichment factor (FEF) in Figs. 1 7 and 1 8 is defmed by the relation
5 16
FEF
where
[xl c + RDF [Fel c + RDF
[x1 c [Fel c
[x/Fe1 c + RDF
[x/Fe] c ( 1 )
[x] micrograms of trace element x per Joule of heat energy input
TABLE 1 4 TRENDS OF TRACE E LEMENTS VARIATION WITH RDF INPUT TO THE
STEAM GENERATOR
Antimony
Arsenic
Beryllium
Cadmium
Chromium
Cobalt
Copper
Gallium
Germanium
Lead
Nickel
Manganese
Mercury
Selenium
·Strontium
Tin
Thallium
Vanadium
Zinc
Bottom Ash
+
BDL
BDL
+
BDL
+
+
BDL
+
+
+
BDL
BDL
+
+
BDL
+
+
Hopper Ash
+
BDL
+
+
BDL
+
+
o
+
o
+
BDL
BDL
+
+
BDL
+
+
Stack Particulate
Filter
BDL
BDL
N .A .
BDL
+
BDL
+
+
o
+
o
+
BDL
o
o
BDL
BDL
o
+
Stack Impinger
Water
BDL
o
BDL
BDL
BDL
o
BDL
BDL
BDL
BDL
BDL
+
+
o
BDL
o
BDL
BDL
BDL
+ indicates an increasing trend with RDF increases
o indicates a lack of any definite trend
- indicates a decreasing trend with RDF increases
StacJ< Impinger ICl-NaOH
BDL
o
BDL
BDL
BDL
o
BDL
'BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
o
Sluice Water
o
o
BDL
BDL
BDL
BDL
o
BDL
BDL
BDL
BDL
BDL
BDL
BDL
o
BDL
BDL
o
BDL
BDL indicates levels were below the detection limit of the analytical instrument
N.A. indicates that no analysis was available
5 1 7
TABLE 1 5 TRACE ELEMENT CONCENTRATION FROM STACK FLUE GAS AS AN ESTIMATE FOR
AMBIENT AIR CONCENTRATION
Concen- S t . Louis* Concen- tration Filter T . E . Flue Gas S t . Louis trat ion from Trace Conc . * Train* eoncen- Conc .
TLV from Filter Element TLV TLV tration TLV mg/m3 mg/m3 train mg /m3 mg/m3
Ant imony 0 . 5 BDL** BDL 0 . 0 22 0 . 044
Arsenic 0 . 5 B DL 0 . 8 7 3 1. 7 4 6 0 . 005 0 . 010
Beryllium 0 . 00 2 BDL BDL 0 . 000 0 . 000
Cadmium 0 . 20 BDL BDL 0 . 00 7 0 . 0 35
Chromium 0 . 05 0 . 00 3 BDL 0 . 060 0 . 511 10 . 220
Cobalt 0 . 1 BDL 0 . 5 30 5 . 300 0 . 085 0 . 850
Copper 0 . 1 0 . 003 0 . 058 0 . 030 0 . 580 0 . 735 7 . 350
Gallium 0 . 00 3 BDL 0 . 003
Germanium 0 . 00 3 BDL 0 . 001
Lead 0 . 15 0 . 04 3 BDL 0 . 28 7 0 . 556 3 . 707
Manganese 5 0 . 01 2 0 . 10 3 0 . 00 2 0 . 0 2 1 0 . 198 0 . 040
Mercury 0 . 05 BDL BDL
Nickel 1 0 . 003 BDL 0 . 00 3 0 . 21 2 0 . 212
Selenium 0 . 2 0 . 00 1 BDL 0 . 005 0 . 001 0 . 005
Stront ium 0 . 015 BDL 0 . 151
Tin 2 BDL BDL 0 . 033 0 . 017
Thall ium 0 . 1 BDL BDL 0 . 000 0 . 000
Vanadium 0 . 5 0 . 016 BDL 0 . 032 0 . 009 0 . 018
Zinc *** 1 0 . 080 0 . 160 0 . 080 0 . 160 1 . 240 1 . 240
* S tack concentrat ions are divided by 1000 .
** BDL indicates levels b elow the detect ion limit of the analytical instrument
*** values are for ZnC12
5 1 8
Coal
Al Si S K Ca Fe Ti
TABLE 1 6 PERCENTAGE OF MINOR CONSTITUENTS IN COAL, RDF, BOTTOM ASH AND
HOPPER FLY ASH
FUELS - o Summar� of All 1978 Runs
Ave + Std Dev RDF Ave + Std Dev
1 . 29 + 0 . 17 Al .1 . 36 + 0 . 48 1 . 94 + 0 . 25 S1 2 . 92 + 0 . 61 2 . 94 ± 00. 76 S 0 . 38 + 0 . 10 0 . 09 + 0 . 02 K 0 . 32 + 0 . 07 0 . 77 + 0 . 30 Ca 0 . 49 + 0 . 31 1 . 55 + 0 . 35 Fe 0 . 42 + 0 . 08 0 . 05 ± 0 . 00 Ti 0 . 19 + 0 . 04
ASH - Summar� of All 1978 Runs 80% Load 100% Load
Bottom Ash 0% RDF 10% RDF 20% RDF 0% RDF 10% RDF 20% RDF
Al 7 . 43 + 1 . 47 6 . 18 + 0 . 60 Si 14 . 7 + 1 . 5 21 . 0 + 2 . 9 S 0 . 92 + 0 . 49 0 0. 64 + 0 . 41 K 0 . 75 :;: 0 . 08 0 . 87 :;: 0 . 03 Ca 7 . 44 :;: 3 . 40 7 . 59 :;: 0 . 77 Fe 1 7 . 4 + 1 . 7 8 . 9 :;: 3 . 0 Ti 0 . 48 ± 0 . 07 0 . 5 7 ± 0 . 11
Hopper Ash
Al 8 . 5 7 + 1 . 48 9 . 37 + 0 . 83 Si 15 . 70 + 0 . 95 1 7 . 33 + 0 . 76 S 0 . 95 + 0 . 20 0 . 65 :;: 0 . 12 K 0 . 96 :;: 0 . 13 1 . 23 :;: 0 . 06 Ca 6 . 61 + 3 . 26 5 . 55 + 0 . 73 Fe 1 7 . 6 :;: 2 . 9 4 1 3 . 9 0 :;: 2 . 62 Ti 0 . 59 ± 0 . 08 0 . 71 ± 0 . 07
*On1y one ana1yis of 100% Load - 0%
14
1 2
1 0
B
FUEL ENRI CHMENT FACTOR
AMES MUN I C I PAL POWER PLANT
BOILER UNIT 7 BO PERCENT LOAD
REFUSE DERIVED FUEL HEAT INPUT , PERCENT
5 . 43 + 0 . 43 3 . 8* 5 . 23 + 0 . 21 5 . 40 + 0 . 92 20 . 8 + 1 . 3 11 . 0 24 . 25 + 1 . 50 24 . 76 + 2 . 31 0 . 27 + 0 . 10 4 . 8 0 . 6 7 + 0 . 24 <0 . 5 + 0 . 0 0 . 85 :;: 0 . 02 0 . 450 0 . 83 :;: 0 . 02 0 . 95 :;: 0 . 02 7 . 88 :;: 1 . 02 14 . 1 7 . 22 + 0 . 27 7 . 88 + 0 . 21 6 . 07 + 1 . 87 13 . 8 7 . 29 :;: 0 . 89 7 . 26 + 0 . 45 0 . 52 ± 0 . 05 0 . 16 0 . 42 + 0 . 02 0 . 46 :;: 0 . 06
8 . 10 + 1 . 35 8 . 53 + 2 . 26 9 . 23 + 1 . 31 8 . 73 + 1 . 90 16 . 13 + 1 . 91 16 . 47 + 2 . 35 17 . 50 + 2 . 69 1 7 . 30 + 2 . 85
0 . 84 :;: 0 . 15 1 . 11 + 0 . 71 0 . 85 :;: 0 . 26 0 . 84 :;: 0 . 09 1 . 16 :;: 0 . 10 0 . 95 :;: 0 . 17 1 . 16 :;: 0 . 08 1 . 29 :;: 0 . 02 7 . 32 :;: 1 . 39 10 . 22 + 3 . 68 7 . 82 + 1 . 1 7 9 . 57 + 0 . 33 15 . 0 :;: 4 . 42 14 . 8 7 :;: 2 . 80 1 1 . 1 5 :;: 3 . 12 11 . 79 :;: 1 . 91 0 . 65 :;: 0 . 08 0 . 53 :;: 0 . 11 0 . 71 :;: 0 . 05 0 . 63 :;: 0 . 05
RDF data availab le
Pb
24
1 2r------------------------------------,
1 0
a: o t; B
� � � 6 u
� z: '"'
..J
� 4
FUEL ENRI CHMENT FACTOR
AMES MUN IC IPAL POWER PLANT
BOILER UNIT 7 1 00 PERCENT LOAD
Zn
O�O----�----�----��--��--��--�24 REFUSE DERIVED FUEL HEAT INPUT , PERCENT
FIG. 1 7 TRACE E LEMENT FUEL ENRICHMENT
FACTORS FOR 80 PERCENT LOAD
FIG. 1 8 TRACE ELEMENT FUEL ENRICHMENT
FACTORS FOR 1 00 PERCENT LOAD
5 1 9
[Fe 1 micrograms of iron per Joule of heat energy input
C Subscript meaning coal only at the input
C + RDF = Subscript meaning mixture of coal and refuse derived fuel at the input
Iron was chosen as a reference because its value was measured more precisely than any other element in the samples of these tests. This is mainly because the quantity of iron in the samples is quite high and significantly above the detection limits or resolving ability of the x-ray fluorescence apparatus used for trace element analysis. The ratio of the amount of element to the amount of iron was formed to help eliminate or cancel any calibration factors in the analytical apparatus that would be of a multiplicative nature . This was felt to be of importance because many of the trace elements scanned were only slightly above the detection
limits of the apparatus. Thus, elimination of as many uncertainties as possible in the data led to the use of enrichment factor for presentation of the trace element results.
CONCLUSIONS
Refuse derived fuel, in combination with coal, was successfully fired in a suspension fired boiler with no insurmountable problems after bottom grates were installed. The major result of this project is that the successful burning of the RDF represents a viable technique for conservation of resources as well as helping to keep good farmland in production instead of using it for landfill.
Some of the significant items which were observed during this study were :
1. The combustible properties of the fly ash and the bottom (grate) ash became quite similar as the RDF approached 20 percent. The softening point of t he ash lowered and the fouling index became more detrimental as the RDF was increased in the fuel input. The fouling impact of RDF at Ames has been recently reduced by a process plant modification which included installation of a degritter. This helped remove a large proportion of sand-glass grit rna terial.
2. Uncontrolled particulate emissions tend to increase with corresponding increases in the RDF fraction of fuel input. This appears to be a result of both lighter particulates and increases in air flow through the boiler when burning RDF. A dump grate was installed in this unit to facilitate burning
of RDF particles not remaining in suspension . The RDF injection nozzle location in relation to the coal nozzle was found to be important in affecting emissions. The lowest particulate emissions occurred when RDF was injected below the coal injection point.
3. The oxides of nitrogen (NOx) and oxides of sulfur (SOx) both decrease while chlorides increase significantly with increases in RDF. No discernible trends, within the data scatter, were noted concerning formaldehyde or hydrocarbon emissions.
Increased emissions of the trace elements zinc, copper and lead corresponded to increases in RDF. Further studies of the trace element emissions are being performed.
This is the first continuously operating system in the United States using the "fluff' or shredded refuse as a supplemental fuel . Thus, the data provided by this paper as well as in some of the referenced reports herein are the only extensive data available for firing RDF with coal in both suspension fired and stoker fired boilers. The results should provide valuable assistance for those planning further facilities.
ACKNOWLEDGMENTS
This project has been supported through EPA Grant R8039030 1 0 and DOE Contract W-7405-Eng-82 . A major portion of the analytical data reported in this paper was provided by Ames laboratory-DOE staff supported by the U.S. Department of Energy, Contract No. W-7405-Eng-82, Office of Health and Environmental Research , Budget Code GK-01 -02-04-3. The following Ames Laboratory staff played a leadership role in the development of analy
.tical methods and in the
direction of the analytical effort : R. Bachman , E. DeKalb, V. A. Fassel , R. J . Hofer , R. N. Kniseley , and J . Richard.
Support has also been received from the American Public Power Association, the Ames Laboratory-DOE, and both the Engineering Research Institute and Mechanical Engineering Department at Iowa State University.
REFERENCES
[ 1 1 "Standards of Performance for New Stationary
Sources" Federal Register, Vol . 36, No. 247, Pt. 1 1 ,
December 23, 1 9 7 1 .
[ 2 1 "Standards o f Performance for New Stationary
Sources. Ammendments to Reference Methods," Federal Register, Vol . 41 , No . 1 1 1 , Pt. 1 1 , June 8, 1 967 .
520
(3) "Standards of Performance for New Stationary Sources," Federal Register, Vol. 38, No. 66, Pt. i 1 , April 6, 1973.
(4) Cooper, John A., "Interpretation of EnergyDispersive X-ray Spectra," American Laboratory, pp. 35-48, November 1976.
(5) Fassel, Vel mer, A., "Quantitative Elemental Analyses by Plasma Emission Spectroscopy," Science, Vol . 202, No. 4364, pp. 183-191, October 13, 1978.
(6) Carotti, A. A. and Kaiser, E. R., Journal of the Air Pollution Control Association, Vol. 22, p . 249, 1972.
( 7 ) Hal l , J. L., et al., "Environmental Evaluation of the Stoker-Fired Steam Generators ( Part III) : Evaluation
of the Ames Solid Waste Recovery System," EPA Special Report (EPA Grant R80390 3010 ) in review, August 1977.
(8) Ananth, K. P., Shannon, l. J., and Schrag, M. G., "Environmental Assessment of Waste-to-Energy Processes Source Assessment Document," U.S. Environmental Protection Agency Document EPA-600/7-77-091, Cincinnati, Ohio, August 1977.
(9) Gorman, P. G., et al., "St. Louis Demonstration Project Final Report : Power Plant Equipment, Faci l ities and Environmental Evaluation," Final Report (EPA Contract No. 68-01-1871 ) , October 1977.
Key Words Boiler
Combustion
Emission
Refuse Derived Fuel
521