AEPA

                  indn     ental Resea  EPA 600 7 78 153b
                             Nov^mti.T 1 978
                       e P.Hk NC 27/11
Sulfur Retention
in Coal Ash

Interagency
Energy/Environment
R&D Program Report

-------
                 RESEARCH REPORTING SERIES


Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional  grouping was  consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:

    1. Environmental Health Effects Research

    2. Environmental Protection Technology

    3. Ecological Research

    4. Environmental Monitoring

    5. Socioeconomic Environmental Studies

    6. Scientific and Technical Assessment Reports (STAR)

    7. Interagency Energy-Environment Research and Development

    8. "Special" Reports

    9. Miscellaneous Reports

This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded  under the 17-agency Federal  Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development  of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects;  assessments  of, and development of, control  technologies for energy
systems; and integrated assessments of a wide range of energy-related environ-
mental issues.
                        EPA REVIEW NOTICE
This report has been reviewed by the participating Federal Agencies, and approved
for publication. Approval does  not signify that the contents necessarily reflect
the views and policies of the Government, nor does mention of trade names or
commercial products constitute endorsement or  recommendation for use.

This document is available to the public through  the National Technical Informa-
tion Service, Springfield, Virginia 22161.

-------
                            EPA-600/7-78-153b

                                  November 1978
Sulfur  Retention
     in  Coal  Ash
                by

   K.L Maloney, P.K. Engel, and S.S. Cherry

              KVB, Inc.
         17332 Irvine Boulevard
         Tustin, California 92680
        Contract No. 68-02-1863
      Program Element No. EHE624A
    EPA Project Officer: David G. Lachapelle

  Industrial Environmental Research Laboratory
    Office of Energy, Minerals, and Industry
      Research Triangle Park, NC  27711
             Prepared for

  U.S. ENVIRONMENTAL PROTECTION AGENCY
     Office of Research and Development
         Washington, DC 20460

-------
                                  ABSTRACT

        An analytical study was conducted to assess the potential for sulfur
retention in various types of coal-fired boilers.  The results of a field test
of ten industrial coal-fired boilers were used to evaluate the impact on sulfur
retention of the operating variables (load and excess O_).
        The effect of ash composition on sulfur retention was also evaluated
with the use of a linear regression analysis.  An expression of the form

   Percent Sulfur Emitted = a+b (%Na O/%CaO) + C (load/10 )
where a, b and c are constants, gave the best overall fit to the two pulverized
coal-fired boiler data.
        The field test results and the regression analysis results were sup-
ported by equilibrium coal ash composition calculations over a range of
temperatures and theoretical air for four coal ash compositions.  These cal-
culations show that significant fractions of the sulfur can be tied up as Ca
and Na salts under both reducing and oxidizing conditions at temperatures
below 2500 °F.  A minimum in the total condensed phase sulfur species is pre-
dicted at stoichiometric conditions for all temperatures.

-------
                                   CONTENTS
Section                                                                Page
        Abstract                                                         ±±
        Figures
                                                                         IV
        Tables                                                            .
        Conversion Factors                                              viii
1 . 0     INTRODUCTION                                                      1
2.0     SULFUR RETENTION CORRELATIONS WITH BOILER CONDITIONS AND
        FUEL ASH COMPOSITION                                              3
        2.1  Sulfur Retention Studies with Boiler Conditions              3
        2.2  Sulfur Retention Studies with Fuel Ash Composition          22
        2.3  Other Related Sulfur Retention Properties                   24
3.0     THERMOCHEMICAL EQUILIBRIUM SULFUR DISTRIBUTIONS                  34
        3.1  Introduction and Background                                 34
        3.2  Computer Program                                            34
        3.3  Coal Compositions                                           35
        3.4  Computer Results                                            37
        3.5  Discussion of the Equilibrium Results                       49
4.0     CONCLUSIONS                                                      57
        References                                                       58
                                     iii

-------
                                    FIGURES


Number                                                                 Page
         2
2-1     R  vs. number of data points.                                    10
2-2     Percent sulfur oxides emitted vs. percent rated load             12
        (at different percent excess oxygen levels), Alma Unit 3.

2-3     Percent sulfur oxides emitted vs. percent rated load             13
        (at different excess oxygen levels), Alma Unit 3.

2-4     Percent sulfur oxides emitted vs. percent rated load             14
        (at different percent excess oxygen levels), University
        of Wisconsin, Stout.

2-5     Percent sulfur oxides emitted vs. percent rated load             15
        (at different percent excess oxygen levels), University
        of Wisconsin, Eau Claire.

2-6     Percent sulfur oxides emitted vs. percent rated load             16
        (at different excess oxygen levies), University of
        Wisconsin, Madison, Unit 2.

2-7     Percent sulfur oxides emitted vs. percent rated load             17
        (at different percent excess oxygen levels), Willmar
        Unit 3.

2-8     Percent sulfur oxides emitted vs. percent rated load             18
        (at different percent excess oxygen levels), Fairmont
        Unit 3.

2-9     Percent sulfur oxides emitted vs. percent rated load             19
        (at different percent excess oxygen levels), St. John's
        Unit 2.

2-10    Percent sulfur oxides emitted vs. percent rated load             20
        (at different percent excess oxygen levels), Waupun
        Unit 3.

2-11    Percent sulfur oxides emitted vs. percent rated load             21
        (at different percent excess oxygen levels), Fremont
        Unit 6.


                                      iv

-------
                             FIGURES (Continued)

Number                                                                 Page
 2-12   Percent sulfur oxides emitted  (measured) vs. percent             29
        sulfur oxides emitted (calculated), Alma Unit 3,
        Sarpy Creek, Montana coal.

 2-13   Percent sulfur oxides emitted  (measured) vs. percent             30
        sulfur oxides emitted (calculated), Fremont Unit 6,
        Hanna-Rosebud, Wyoming coal.

 2-14   Percent sulfur retention vs. calcium to sulfur  (Ca/S)            33
        ratio for lignite samples.

-------
                                   TABLES

Number                                                                  Page

 2-1    SO  Emission Comparison for Western and Eastern Coals             4

 2-2    Operating Conditions and Sulfur Oxide Emissions                   5

 2-3    Multiple Regression Analysis of All Coals Tested for              8
        Excess O , Load, and % Sulfur

 2-4    Sulfur Oxide Retention with Boiler Condition Variation           11

 2-5    Western Coal Ash Analysis                                        23

 2-6    Multiple Regression Analysis Formulations Assessed for           25
        Fuel Ash Composition and Boiler Conditions

 2-7a   Multiple Regression Analyses for Two Western Coals on            26
        Two Pulverized-Coal Boilers

 2-7b   Multiple Regression Analyses for Two Western Coals on            27
        Two Pulverized-Coal Boilers

 2-8    Comparison of Measured and Calculated Percent Fuel               28
        Sulfur Emitted

 2-9    Sulfur Retention by the Ash of the Coals Tested During           31
        Laboratory Ashing at 700-750 °C and Subsequent Mineral
        Analysis by Commercial Testing

 2-10   Variation of Fuel Sulfur Retention with Calcium/Sulfur Ratio     33

 3-1    Coal Compositions                                                36

 3-2    Computer Output for Lignite at 50% Theoretical Air               38

 3-3    Sulfur Distribution, Montana Coal                                40

 3-4    Sulfur Distribution, Lignite                                     42

 3-5    Sulfur Distribution, Augmented Lignite                           44

 3-6    Sulfur Distribution, Pittsburgh #8                               46
                                     VI

-------
                              TABLES (continued)






Number                                                                  Page






 3-7    Sulfur Retention by Condensed Species                            48




 3-8    Mass Balances for Calcium, Potassium and Sodium at 500 °F        50




 3-9    Sulfur Balances on a Laboratory Fuel Bed Simulator               55
                                     VII

-------
                                             CONVERSION FACTORS
                                     SI Units to Metric or English Units
H-
H-
To Obtain
g/Mcal
106 Btu
Btu
lb/106 Btu
ft
in.
ft2
ft3
Ib
Fahrenheit
Fahrenheit
psig
psia
iwg (39.2 °F)
106 Btu/hr
GJ/hr
From
ng/J
GJ
gm cal
ng/J
m
cm
2
m
m3
kg
Celsius
Kelvin
Pa
Pa
Pa
MW
MW
Multiply By
0.004186
0.948
3. 9685x10" 3
0.00233
3.281
0.3937
10.764
35.314
2.205
tp - 9/5 
-------
                               English and Metric Units to SI Units
                                                                                              Multiply*

To Obtain
ng/J
ng/J
GJ
m

cm

m2
m3
kg
Celsius
Kelvin

Pa
Pa
Pa
MW
MW



From
lb/106 Btu
g/Mcal
106 Btu
ft

in.

ft2
ft3
Ib
Fahrenheit
Fahrenheit

psig
psia
iwg (39.2 °F)
fL
10° Btu/hr
GJ/hr



Multiply By
430
239
1.055
0.3048

2.54

0.0929
0.02832
0.4536
tc - 5/9 
-------
                                 SECTION 1.0
                                INTRODUCTION

        The objective of this study was to determine the effect of boiler
conditions and coal ash compositions on the sulfur retention characteristics
of different eastern and western coals.  To this end the results of field
tests on ten industrial sized coal fired boilers have been evaluated.  These
ten industrial boilers represented a variety of firing types ranging from
mass feed stokers to pulverized coal fired boilers.  In order to support
the field test results, thennodynamic equilibrium calculations have been
performed on four of the coals tested in the field to predict the sulfur
distribution among the ash constituents at five stoichiometric ratios for
a range of temperatures.
        Conditions of temperature, stoichiometry, and ash composition have
been identified where thermodynamic equilibrium predicts large sulfur
retention in the solid ash.  Whether these large retentions are attained
in the field depends upon how good the contact is between the sulfur and
the metal compounds within the other constraints.  In addition to the contact
problem, the sulfur retention is further governed by the rates of the retention
reactions and the temperature/stoichiometry history of the sulfur and ash
components.
        In normal combustion processes, all of the fuel sulfur is converted
to sulfur oxides (SO )—mostly to SO  with a small amount being further
                    Jt               A
oxidized to SO_.  However, in some instances for the combustion of coal, the
SO  emissions have been observed to be less than expected for the complete
  x
oxidation of all of the fuel sulfur.  These reduced SO  emissions were greater
                                                      Ji
when the coal ashes were more alkaline.

-------
         To explain these reduced SO  emissions, the boiler conditions have
                                    3£
 been reported by other researchers to have a significant influence.  The SO
                                                                            A
 emissions could be related to load and percent excess oxygen by an equation
 of the type:
     Percent sulfur emitted = a + b (percent excess oxygen)
                              + c (load/100, 000) *                         (1)

         Other studies have related sulfur retention to the mineral composition
 of the fuels or their ashes.  For boilers firing lignite, Gronhovd (Ref. 1) and his
 associates found the following relationship that satisfactorily correlated
 their data:
             Sulfur emitted as % sulfur in coal =
                                     Na 0
         For EPA Contract 68-02-1863, comprehensive measurements on ten
 industrial boilers were made.  Fuel and ash samples were collected for
 analysis at recorded load and excess oxygen conditions.  The fuel samples
 were analyzed for ultimate constituents and the ash samples for chemical
 composition including CaO, Na_0, Al O_, MgO, K_0, and SiO .
*In all regression analyses, load was taken in pounds of steam.

-------
                                 SECTION 2.0
            SULFUR RETENTION CORRELATIONS WITH BOILER CONDITIONS
                          AND FUEL ASH COMPOSITION

 2.1     SULFUR RETENTION STUDIES WITH BOILER CONDITIONS
        Basically, the results of overall study showed that the retention
of sulfur by western coal was significantly greater than the retention of
sulfur by eastern coal.  The overall average western coal fuel sulfur content
 (of coals tested) was 775 ng/J  (1.81 Ib SO /10  Btu fired) with an average
fuel sulfur emitted of 79.8%.  For eastern coal, the average fuel sulfur
content was 2021 ng/J  (4.7 Ib SO2/10  Btu fired) with an average fuel
sulfur emitted of 90.4%.  Table 2-1 shows the SO  emission comparison for
western and eastern coals for the industrial-sized boilers.
        In order to evaluate the results from sulfur emissions studies of
ten industrial-sized coal-fired boilers, multiple linear regression analyses
using both combustion conditions of the boiler operations and chemical
composition of the fuel ashes were performed.  An assumption was made that
effects of load and excess oxygen were independently controllable variables.
        Table 2-2 contains the data regarding the combustion conditions
 (i.e., percent excess oxygen and load), coal sulfur levels and measurements
of sulfur oxides emitted.
        For each boiler and each type of fuel, regression analyses were
performed using the relationship:
        Percent sulfur emitted = a + b(percent excess oxygen) + c(load/100,000)
where a is a constant, and b and c are coefficients.
        Table 2-3 presents the results of these regression analyses.  The
correlations accounted for 16% to 100% of the data for eastern coals and
for 50% to 100% of the data for western coals.  Caution must be exercised
in interpreting the data; for example, the Eau Claire site with eastern
coal has only three data points.

-------
                  TABLE  2-1.  80x EMISSION COMPARISON FOR WESTERN AND EASTERN COALS
Boiler
Test Sit* Type
Alma PC
Stout VG
Madison 55
Willmar SS
Eau Claire TG
St. Johns DG
Fremont PC
Fremont PC
Alma PC
Stout TG
Willmar SS/TG
Eau Claire VG
Madison SS/TG
Fairmont PC
Coal Source (Mine)
Western Coal
Montana (Sarpy Creek)
Wyoming (Bighorn)
Montana (Colstrip)
Montana (Colstrip)
Wyoming (Bighorn)
Wyoming (Bighorn)
Wyoming (Banna-Rosebud)
Colorado (Walden)
Overall Average
Eastern Coal
Kentucky (River King)
Kentucky (Vogue, Seam 2)
So. Illinois (Stone fort)
W. Kentucky (Vogue)
W. Kentucky (Vogue)
So. Illinois (Sahara)
Overall Average
Average Fuel Sulfur
percent
0.96
0.96
0.99
1.15
0.73
0.61
1.38
0.38
3.57
2.94
2.28
2.87
3.04
2.13
ng/J
(Ib B02/106
Btu Fired)
880 (2.05)
822 (1.92)
949 (2.21)
1174 (2.74)
657 (1.53)
498 (1.16)
957 (2.23)
263 (0.61)
775 (1.81)
2800 (6.64)
2043 (4.76)
1567 (3.65)
1803 (4.72)
2167 (5.05)
1471 (3.43)
2021 (4.71)
Average SO. Emissions
pom
791
681
1044
934
695
592
1053
235
3036
2129
1815
2363
2378
1628
ng/J
(Ib S02/106
Btu Fired)
649 (1.51)
559 (1.30)
858 (2.00)
766 (1.79)
570 (1.33)
486 (1.13)
864 (2.01)
193 (0.45)
618 (1.44)
2491 (5.81)
1747 (4.07)
1489 (3.47)
1939 . (4.52)
1952 (4.55)
1336 (3.11)
1826 (4.25)
Fuel
Sulfur
Emitted
percent
73.8
69.6
90.4
65.3
86.8
97.5
90.3
73.4
79.8
87.0
85.5
94.0
95.0
90.0
89.7
90.4
Average  SO  reduction based on flue  gas emission measurements =  1206 ng/J
           *                                                                 6
Average  SO  reduction based on fuel  analysis = 1244 ng/J  (2.90 Ib SO./10
                      (2.81 Ib S02/10*

                      Btu) - 61.7%
Btu) » 66.1%
                      VG - Vibrating Grate
                    TG/SS - Spreader Stoker with Travel Grate
                      PC - Pulverized Coal
UR - Underfed stoker
TG - Travel Grate Stoker

-------
        TABLE 2-2.   OPERATING CONDITIONS AND SULFUR OXIDE EMISSIONS
As Received
Load Excess
Test Factor Oj SOx
Site No. % » ng/J
Ainu (PC
Eastern







Western


, 29 kg/s
6
7
9
11
14
16
21
53
57
63
64
85
49
57
53
89
26
26
57
74
57
74
65*
66







Stout St.
Eastern



western







68
72
73
74
75
76
78
U.
22
19
27
31
3
4
8
11
13
14
IS
36
Eau Claire
Eastern


Western




11
20
30
1
3
4
7
10
75
44
41
39
70
70
48

-------
                             TABLE 2-2  (Continued).
AB Received
Site
Madison
Eastern





Western






Willnar
Eastern






Western


Painpont
Eastern






Western







Load
Test Factor
No. %
(SS/TG,
11
12
14
IS
17
19
2
5
7
8
9
10
3
(SS/TG
26
28
30
31
32
33
34
8
15
16
(SS/TG
2
4
5
7
8
9
10
11
12
14
15
17
18
19
20
Excess
O2 SOx
% nq/J
12.6 kg/s (lOOxlO3
60
60
90
90
30
30
60
90
30
80
80
30
60
. 20.2
66
78
52
48
55
69
83
68
49
69
, 10.1
61
62
61
74
36
78
76
75
76
57
38
75
57
55
42
10.0
12.0
7.3
9.1
14.7
15.8
6.5
7.2
13.6
9.7
6.2
13.5
10.9
kg/S
8.6
6.5
10.0
8.4
11.9
6.6
5.9
8.6
8.2
6.6
kg/a
9.1
10.1
8.2
8.0
13.5
6.5
9.8
7.0
7.0
8.0
12.9
6.6
9.4
12.4
14.1
1711
1761
1739
1924
2539
2431
862
919
492
1070
1293
1155
1481
Coal Botton
Sulfur Fly Ash Ash
as SO. Sulfur Sulfur
ng/J ng/J ng/J
Ib/hr)
2119
2412
2195
2215
2053
2144
953
719
908
817
937
1224
1767
(160X103 Ib/hr)
1791
1492
1431
1550
1553
1541
1573
1031
899
937
(BOxlO3
1342
1396
1151
1564
1442
1350
1160
1252
1330
1314
1015
1222
1360
1273
1170
1644
1461
1455
1448
1468
1492
1570
1176
1000
703
Ib/hr)
1438
1674
1732
1323
1448
1425
1374
1882
1176
1412
1169
1309
1349
1535
1355
•teas, BCW)
22
25
8
IS
5
7

60
26
37
27
20
48
Heat
Value
J/g

27681
28090
27902
29085
28806
27263
21966
20228
20442
21030
19840
20540
20242
Ash
Content
%

8.79
8.88
9.6
7.98
8.7
9.2
8.26
8.29
7.99
8.12
8.68
8.95
10.22
Measured
Fuel
Sulfur Gronhovd
Emitted Prediction
t %

81
73
79 109
87
124
112
91 99
122
54
131
138
94
84 100
Calculated*
Fuel
Sulfur
Emitted
t

88.1
94.3
73.1
78.7
109.2
112.6
99.6
131.5
69.9
121.7
120.6
69.9
100.9
•team, Detroit Stoker)










steam, Erie City)





15



4

6

11

29182
29133
28978
29257
29275
29341
29022
19540
20179
20467

29050
29248
28930
28640
29255
28860
29190
24316
25400
25185
25510
25900
25020
26686
26549
8.65
8.22
8.25
8.43
7.67
8.34
7.76
9.12
8.82
8.57

8.67
9.24
8.85
8.69
8.74
8.11
8.41
9.14
8.96
8.17
8.97
9.69
8.92
10.00
7.94
109 108
102
98
107
106
103
100
88 100
90
133

93
83
66
118 108
100
95
84
67
113 106
93
87
93
101
83
86
103.5
102.4
104.7
104.7
104.8
103.0
101.9
88.0
90.0
133.0

89.9
92.2
87.9
91.7
90.9
90.0
96.3
91.7
91.5
95.5
89.7
92.7
92.0
84.9
85.0
•Load, Excess O  Regression Analysis
(continued)

-------
                               TABLE  2-2  (Continued).
As Received
Site
Test
No.
Load Excess
Factor O
* r
St. Johns (SS/DG,
Eastern





Western





Fremont
Western
Harms, WY



11
12
13
14
15
16
2
3
4
5
6
8
(PC.
3
4
5
6
7
Western 9
Walden.CO u



Waupan
Western




RDF
Blend



13
14
15
(SS/TC
1
2
3
5
6
0%
20%
RDF
30%
RDF
40%
RDF
63
45
43
43
61
59
62
41
43
42
43
65
20.2
68
41
83
73
68
87
72
70
44
70
, 3.8
54
52
91
91
90
73
75
59
76
SOx
ng/J
1.7 kg/s (13.5x10
14.2 366
15.5
16.3
15.5
15.6
13.40
13.7
16.3
16.5
15.2
17.0
13.4
354
306
413
372
351
392
508
492
608
509
474
Coal
Sulfur Ply Ash
as SO Sulfur
ng/J ng/J
3 Ib/hr) stean,
367
365
321
363
373
380
565
504
515
577
649
498
Bottom
Ash
Sulfur
ng/J
Keeler)
3
3
4
1
1

14

8
IS
8

Heat
Value
J/g
31027
31685
31046
31343
32078
30524
22273
22173
22459
22484
22786
24458
Ash
Content
t
6.63
5.31
7.10
5.92
4.42
5.29
5.52
4.99
5.59
5.66
5.28
5.14
Measured
Fuel
Sulfur
Emitted
100
97
95
114
100
92
63
101
95
105
78
95
Gronhovd
Prediction


109.9
108.6
108.3
108.3





97
Calculated*
Fuel
Sulfur
Emitted
97.0
101. J
102.5
101.5
99.0
96.7
80.1
96.4
89.6
108.4
83.2
79.2
kg/s (160xl03 Ib/hr) steam, BSH)
5.4
5.3
5.4
4.1
3.6
5.5
4.3
5.1
4.2
3.4
987
1014
1151
772
689
251
208
228
184
203
1063 88
1168 75
1072 76
812 52
795 28
221
238 9
-
268 13
258 6








kg/s (30xl03 Ib/hr) steam, Wickes)
13.2 241 747 23
11.8
11.5
11.5
11.0
9.73
9.59
11.53
10.50
469
443
265
204
227
— -
156
255
596
641
799
861
817
822
822
757
10
30
26
23
66
72
83
132
29150
28771
29095
28578
28694
28020
27706

28343
28664
20063
20121
19960
20520
20186
22774
20557
19617
18554
9.85
10.44
9.99
7.76
7.95
8.31
-
7.85
7.91
8.67
7.81
8.21
8.00
8.02
10.55



93
87
107
95
87
113
87
-
68.4
78.7
32
79
69
33
24
28
~~
32
28
106
105
104
106
106
107




99
101.6


93



97.6
85.2
104.6
93.5
88.2
112.3
88.9

68.7
78.1
41.1
69.6
38.6
38.3
49.3
27.6
™~
32.2
28.0
•Load, Excess O. Regression Analysis

-------
                     TABLE 2-3.   MULTIPLE REGRESSION ANALYSIS OF ALL COALS TESTED
                                   FOR EXCESS O ,  LOAD,  AND % SULFUR
Site
Alma (8)
(PC) (11)
(5)
Stout St. U. (4)
(TG) (8)
Eau Claire (3)
(VG) (5)
Madison (6)
(SS) (7)
Willmar (7)
(SS) (3)
Fairmont (7)
(SS) (8)
Waupun (5)
(SS) (4)
St. John's (6)
(SS-DG) (6)
Fremont (5)
(PC) (5)
Coal Type
W. Kentucky
Montana
Montana*
W. Kentucky
Wyoming
W, Kentucky
Wyoming
W. Kentucky
Montana
Illinois
Montana
So. Illinois
Blend
Montana
RDF**
Eastern
Western
Hanna, WY
Walden, CO
a.
88.693
103.065
137.584
107.159
97.143
267.766
169.449
70.038
34.090
106.383
255.141
49.467
136.478
348.850
34.536
88.617
400.946
40.679
- 6.770
b.
(Excess 02
Coefficient)
- 0.275
- 0.282
- 6.221
- 2.642
- 3.686
- 10.524
- 11.018
3.109
0.296
0.174
- 22.318
2.176
- 2.598
- 19.446
0.719
1.243
- 12.769
4.922
9.953
c.
(Load
Coefficient)
7.886
- 11.773
- 14.251
25.035
32.000
- 218.996
55.739
- 21.797
105.896
- 4.115
22.786
42.218
- 43.955
- 317.128
- 61.502
- 107.931
- 1720.779
27.942
45.991
R Fit
Correlation
0.621
0.246
0.913
0.832
0.250
1.000
0.825
0.607
0.688
0.091
1.000
0.027
0.076
0.283
1.000
0.105
0.504
0.875
0.996
  *5  high confidence points
 **Refuse-derived fuel
( )No.  of data points
(SS)  - Spreader Stoker
(DG)  - Dumping Grate
(TG)  - Traveling Grate Stoker
(PC)  -  Pulverized Coal
(VG)  -  Vibrating Grate

-------
        Figure 2-1 contains the value of R  plotted as a function of the number
of data points in Table 2-3 that were used to arrive at the R  value.  Above
the curve drawn in this figure is the region of 95 percent confidence interval
for that number of data points.  It can be seen that when the sample size is
                                  2
small, a large absolute value of R  is required to show significant correlation.
        Seven values of R  fall below the line and twelve values are above the
line.
        Specifically for the Alma site for five high confidence points, the
regression analysis yields the relationship:
  Percent sulfur emitted = 137.6 - 6.2(percent excess oxygen) - 14.3(load/100,000)
This equation accounts for 95.6% of the variations in the data.
        Table 2-4 summarizes the fit correlations for all the coals and units
tested.  The entries indicate whether the sulfur retention increases or decreases
when the percent excess oxygen is increased and when the load is increased.
Also at the bottom of Table 2-4, the total number of increases and decreases
for each variable are shown for both eastern and western coals after low confi-
dence data as well as the Waupun Refused-Derived Fuel data were eliminated.
Thirty percent of the data were removed due to low confidence factors.  The
conclusions were that, for boilers tested, a greater sulfur retention tendency
was exhibited at higher excess oxygen and a tendency for less sulfur retention
at higher loads.  The same overall trends held for both eastern and western coals.
        More specifically for the different types of boilers, two pulverized
coal-fired boilers exhibited opposing sulfur retention behavior with respect
to load and excess oxygen.  A unit-by-unit analysis of the stoker data did not
reveal an explicit explanation of the different sulfur retention behavior
between units.
        Figures 2-2 through 2-11 represent the relationships using the coeffi-
cients developed in the regression analyses as shown in Table 2-3.  In these
figures only normal boiler operating conditions are used.  The original assump-
tion regarding variation of the boiler conditions must be reassessed.  The sul-
fur retention behavior may have been artifically attributed to the boiler con-
ditions as independent variables by the formulation of the terms of the regres-
sion analyses as well as the scarcity of data.  In most cases, as the boiler

-------
i.o
0.8
0.6
0.4
0.2
o
                                             Critical Value
                                                Region
                          5                     10

                          NUMBER OF DATA POINTS
                                                        15
 Table 2-1.  R  vs. number of data points.
                                  10

-------
TABLE 2-4.  SULFUR OXIDE RETENTION WITH BOILER CONDITION VARIATION
Site
Boiler Type*3
Boiler Capac. (10 Ib/hr)
Alma PC23Q
Eastern
Western
Western
Stout TG/SS
Eastern
Western
Eau Claire VG
Eastern
Western
Madison SS
Eastern
Western
Willmar SS,-..
_ lou
Eastern
Western
Fairmont SS
Eastern
Western
Waupun SS
RDF
Western
St. Johns DG/SS14
Eastern
Western
Fremont PC. __
_ . IbU
Eastern
Western
Totals
Eastern
Western
Conclusion:

Sulfur Retention
Increase Increase R
O^ Load Correlation
1 2
Up
Up
Up
Up
Up*
Up
UP
Down
Down
Down*
Up
Up*
Up*
Down
Up*
Down*
Up
Down
Down
4 Down 7 Up 6
(2 Down) (3 Up) (3
(2 Down) (4 Up) (3
Retention Increases
Retention Decreases
Down 0 . 62
Up 0.91+
Up 0.25*
Down 0.83
Down* 0.25*
Up 1.00
Down 0.83
Up 0.61
Down 0 . 69
Up* 0.09*
Down 1.00
Down* 0.027*
Up* 0.076*
Up 1.000
Up* 0.28*
Up* 0.10*
Up 0.50
Down 0.88
Down 1;00
Down 4 Up
Down) (2 Up)
Down) (2 Up)
With Increased O2
with Increased Load.



      •Eliminated from totals
      due to blended coal supply
t5 high confidence points
iBoiler Type:
  VG - Vibrograte Stoker
  TG/SS - Traveling Grate Stoker
  SS - Spreader Stoker
  PC - Pulverized Coal
  DG/SS - Dumping Grate Spreader
  11

-------
                   110
1
H
               a
               D
               CO
               3
               H
               CO


               §
               H


               §
               CO
                   100
                    90
                    80
                    70
                                            2% O
                                  6%  O
                                            2% O,
                                                     6% O,
                           Rated load = 29 kg/s

                           (230,000 Ib/hr) steam
                                          Western
                                  I
                                          Eastern  — — — — —
                               I
                                  25          50



                                  PERCENT RATED LOAD
                                           75
100
Figure 2-2.  Percent sulfur oxides emitted vs. percent rated  load  (at

             different percent excess oxygen levels), Alma Unit  3.
                                      12

-------
                    110
                o
                u

                2
                H
                D
                to
                W
                Pk

                co
                Q
                W
                H
                CO
                H



                g
§
    100
                    90
                    80
                    70
                                                 2% O,
                                                              2% O.
                                                    6% O
                        Rated load = 29 kg/s

                        (230,000 Ib/hr) steam
                                       Western


                                        5 High

                                        Confidence
                                               T
                                   25           50          75



                                       PERCENT RATED LOAD
                                                       100
Figure 2-3.  Percent sulfur oxides  emitted vs.  percent rated load (at

             different excess oxygen  levels), Alma Unit 3.
                                      13

-------
1
z
           D
           a
           D
           CO
           W
           g
           w
           S
           H
           X
           o
           Pi
           D
           CO
                 100
                 100
                  90
                  80
                  70
                  60
                  50
                                                 5% O,
                                                             5% O,
                                                   10% O.
                                                 10% O_   —
                                          Rated load =5.7 kg/s
                                           (45,000 Ib/hr)  steam
                                          Western
                                          Eastern   —___-—,
                                             I
                                25          50

                                 .  PERCENT RATED LOAD
                                              75
100
Figure 2-4.  Percent sulfur oxides emitted vs. percent  rated load (at
             different percent excess oxygen levels), University of
             Wisconsin, Stout.
                                      14

-------
               1
               2
               H
               a,
               D
               D
               CO
               w
               cu

               to
               Q

               I
               CO
               w
               Q
               H
               X
               o
               D
               CO
                   100
      80
                   60
                   40
                   20
                                  I
                                                  10% O
                                           Rated load = 7.6 kg/s

                                           (60,000 Ib/hr)  steam
                                          Western
                                           Eastern  __ ._ ^_ ^
                                 25           50

                                   PERCENT RATED LOAD
                                              75
100
Figur.6 2-5.
Percent sulfur oxides emitted vs. percent  rated load (at

different percent excess oxygen  levels), University of

Wisconsin, Eau Claire.
                                      15

-------
                 110
              w

              8
              H

              §

              OS
              D
              s
                 100
                  90
                  80
g
u
z
H

D
a
g
              w
              A   70
    60
                  50
                                          6% 0
                            Rated load = 12.6 kg/s

                            (100,000 Ib/hr) steam
                                          Western
                                          Eastern   _


                                             »            i
                               25
                              50
75
100
                                   PERCENT RATED LOAD
Figure 2-6.  Percent sulfur oxides emitted vs. percent rated load  (at

             different excess oxygen levels), University of Wisconsin, Madison,

             Unit 2.
                                      16

-------
          8
          D
          CO
          W
          w
          04
          CO
          Q
          E
          H
          CO
           H
           §
               100
                90
80
                70
60
                50
                                               8% O.
                  Western
                  Eastern
     Rated load =20.2 kg/s
      (160,000 Ib/hr) steam
              25          50
10% O —
                                                      75
                                                   100
                                  PERCENT RATED LOAD
Figure 2-7.  Percent sulfur oxides emitted vs. percent  rated load (at
             different percent excess oxygen  levels) , Willmar Unit 3.
                                      17

-------
                     110
                §

                2
                H

                OS
                D
                8
                CO
Q
W

B
H
                C/J
                w
                Q
                H
                X
                o
                     100
     90
                      80
                      70
     60
                      50
                                                       O.


                                       Rated load =10.1 kg/s

                                       (80,000 Ib/hr)  steam
                                      Blend  Western
                                    I
                             Eastern   „ ^ .	


                                i	 I
                                   25           50          75


                                       PERCENT RATED LOAD
                                                       100
Figure 2-8.  Percent sulfur oxides emitted vs. percent rated load (at

             different percent excess oxygen levels), Fairmont Unit  3.
                                       18

-------
               u

               z
               H
               D
               CO
               u

               8
               H
               CU

               CO
e
H
               CO

               W
               Q
               H
               D
               CO
                  110
                  100
     90
     80
                   70
                   60
                    50
110% O.
                                                 12% O.
            Rated load =1.7 kg/s

        —   (13,500 Ib/hr) steam
                                                         15% O,
                                            Western
                                  I
                             Eastern   — _ — — —


                                I            I
                                  25          50          75


                                      PERCENT RATED LOAD
                                                      100
Figure 2-9.  Percent sulfur oxides  emitted vs.  percent rated load (at

             different percent  excess oxygen levels),  St.  John's Unit 2,
                                      19

-------
                  140
              u
              2
              H
              OS
              D
              g
Pi
W

Q
EH
M

CO
              M
              g
              PS
              D
                  120
                  100
      80
                   60
      40
                   20
                                                   12% O,
                                           10% O
            Rated load = 3.8 lK.g/s
            (30,000 Ib/hr) steam
                                           Western
                                  I
                      Western + RDF Blend

                     	I	
I
                     0           25           50          75          100
                                     PERCENT RATED LOAD

Figure 2-10. Percent sulfur oxides emitted  vs. percent rated load (at
             different percent excess  oxygen levels),  Waupun Unit 3.
                                      20

-------
                   110
Figure 2-11.
               2
               H
               D
               W
               w
               en
               <
               Q

               I
               W
               s
               g
                   100
                    90
                    80
      70
      60
                    50
                                             6%
            Rated load =20.2
                          kg/s
            (160,000 Ib/hr) steam
                     Hanna Western
                     Walden Western
                                   I
                                 I
                                                        2% O,
I
                                  25           50         75

                                       PERCENT  RATED LOAD
                                                        100
Percent sulfur oxides emitted vs. percent rated load (at
different percent excess oxygen levels), Fremont Unit 6.
                                      21

-------
load increased, the percent excess oxygen decreased.  Due to fan capacity
limitations, it was generally impossible to vary the excess oxygen at high
boiler loads.  At lower loads changing the excess air could disrupt the fuel
bed in a stoker unit and could lead to smoking in a pulverized-coal boiler.
This meant that the excess oxygen was strongly coupled to the load for most
boilers.  The method of formulating the linear multiple regression analysis
relationships, in the manner assumed, may have given undue weighting to the
boiler load.  It has been noted that the bulk gas temperature does not change
drastically over the load range of most industrial boilers.  The derived
relationships for sulfur retention could be the result of lower operating
excess air at higher load and not the derived dependence of sulfur retention
on boiler load.  Additional data would unquestionably increase the confidence
level in the trends and conclusions.
        The results of the equilibrium calculations indicate that if kinetic
factors and/or mixing factors are not important, which is doubtful, then the
sulfur retention should increase with decreasing temperature below about
2500 °F for all stoichiometric conditions.  Below this temperature there is
significant retention as condensed phase species if the metals are present in
sufficient quantities to combine with the sulfur.  Above 2500 °F the sulfur
species are gaseous with SO. the dominant component at 75, 100, 125 and 150
percent theoretical air.  At 50 percent air H2S, SO, and SH share the bulk of
the sulfur.
        The equilibrium calculations further indicate that increasing the
theoretical air (excess O_) in the oxidizing region at a given temperature
should reduce the sulfur emitted.  Therefore, from a thennodynamic equilibrium
viewpoint, the sulfur retention would increase with decreasing temperature
and increase with increasing excess O .

2.2     SULFUR RETENTION STUDIES WITH FUEL ASH COMPOSITION
        At two pulverized coal boilers which were fired on western coal,
comprehensive analyses on the fuel ashes were completed for five individual
test conditions as presented in Table 2-5.  These sites were Alma with a
maximum load of 29 kg/s (230,000 Ib/hr) which was burning a Montana  (Sarpy
Creek) coal and Fremont with a maximum load of 20.2 kg/s  (160,000 Ib/hr) which
was burning a Wyoming (Hanna-Rosebud) coal.
                                      22

-------
                                  TABLE  2-5.   WESTERN COAL ASH ANALYSIS
to
u>
Site (Coal)/
Test No.
Alma
Creek




(Sarpy
, MO)
72
74
75
76
78
Load
kq/s (103 Ib/h)
12.75
11.36
20.33
20.33
13.89
Fremont (Hanna-
Rosebud, WY)
3 17.55




4
5
6
7
14.52
14.14
8.84
14.14
(101)
(90)
(161)
(161)
(110)
(139)
(115)
(112)
(70)
(112)
Excess
6.7
6.8
5.8
3.8
4.8
5.4
5.3
5.4
4.1
3.6
CaO
11.32
13.50
15.20
13.52
13.50
6.77
7.50
7.72
4.70
4.27
8a2o
2.08
2.71
3.08
2.63
2.57
0.28
0.48
0.41
0.42
0.34
MgO
2.12
2.40
2.84
2.60
2.60
2.16
1.92
2.38
1.90
1.80
A1203
18.21
17.14
19.18
18.07
18.07
20.85
19.24
18.91
15.02
13.37
Meas. In (Meas.%
SiO Sulfur Sulfur
(%) Emitted, % Emitted)
41.96
39.68
37.17
40.13
38.91
48.27
50.08
47.54
61.43
62.90
85
84
76
86
91
93
87
107
95
87
4.443
4.431
4.331
4.454
4.511
4.533
4.466
4.673
4.554
4.466

-------
        As  shown  in Table 2-6, multiple regression analyses were performed
evaluating  the dependence of percent sulfur emitted on the fuel ash composi-
tion and boiler conditions.  The correlations were shown to account   for 17
to  98%  of the variation of the percent fuel sulfur emitted for the Alma data
and for 14 to 92% of the variation of the percent fuel sulfur emitted.  In
7 out of 14 relationships assessed/ the sign of the coefficients were the
same for both Alma and Fremont indicating that the dependence of sulfur
retention were similar for those particular relationships.  Tables 2-7a and
2-7b present the  coefficients and R  of the various relationships assessed
in  this study.
        Table 2-8 shows a comparison of measured percent fuel sulfur emitted
and the calculated percent fuel sulfur emitted by Gronhovd's relationship
and the various empirical correlations developed in this study.  The plots
comparing the measured and calculated percent fuel sulfur emitted for three
of the  fuel ash composition relationships are shown in Figures 2-12 and 2-13
(A, B and C in Table 2-8).   The plots show that the relationships developed
from the western coal fuel ash composition data appear to predict more
closely the sulfur emitted than Gronhovd's relationship for lignite burning
boilers.

2.3     OTHER RELATED SULFUR RETENTION PROPERTIES
        The effect of Commercial Testing Laboratories' sulfur analysis proce-
dures on sulfur retention in the sample were investigated during the course of
this study.  This was done in order to determine the effect of the temperature
history on the sample since the laboratory procedure controls the temperature
as well as provides for a longer residence time at that controlled temperature.
Table 2-9 contains the results of all coal samples tested by this laboratory
during  the project.  Two points become evident.  First, there was significant
sulfur  retention under the laboratory ashing condition at 700-750 °C and
secondly,  the occurrence of lime increased this retention on the average
by some 45 percentage points from 7.7% retention for eastern coal samples
to 53.1% retention for western coal samples.  It is significant that the
calcium content of western coal was higher than the others and that the
western coal showed correspondingly greater sulfur retention.
                                      24

-------
TABLE 2-6.  MULTIPLE REGRESSION ANALYSIS FORMULATIONS ASSESSED FOR


              FUEL ASH COMPOSITION AND BOILER CONDITIONS
A.  RELATIONSHIPS OF TYPE





    I  Percent Sulfur Emitted



   II  Percent Sulfur Emitted



  III  Percent Sulfur Emitted



   IV  Percent Sulfur Emitted



    V  Percent Sulfur Emitted



   VI  Percent Sulfur Emitted



  VII  Percent Sulfur Emitted



 VIII  Percent Sulfur Emitted



   IX  Percent Sulfur Emitted



    X  Percent Sulfur Emitted





B.  RELATIONSHIPS OF TYPE
                         Y = a + bX + cZ





                           a + b[% CaO/% Al O ] + c[% Na 0/% SiO ]




                           a + b[% CaO] + [% Na 0]




                           a + b[% Na20/% CaO] + c [Load/105]




                           a + b[% Ma 0/% CaO] + c [Excess Oxygen]




                           a + b[% CaO] + c [MgO]




                           a + b[% CaO/% MgO]




                           a + b[% CaO/% MgO] + c [Excess Oxygen]




                           a + b[% CaO/% MgO] + c [Load/10 ]




                           a + b[% CaO/% MgO] + c[ (Excess Oxygen x 10 )/Load]




                           a + b[% CaO/% MgO] + c[% MgO/% SiO2]



                                  BZ
                           = AXeorlnY=a + blnX + cZ





                                             tB L°a / ° J
   XI  Percent Sulfur Emitted = A  [% CaO/% MgO] e



  XII  Percent Sulfur Emitted = A  [% CaO/% MgO] e



 XIII  Percent Sulfur Emitted = A  [ (% CaO • % SiO_)/(% Al 0  • % MgO)] e
                                                 t


  XIV  Percent Sulfur Emitted = A  [Excess Oxygen] e
                                             [(B EXC6SS <***" X
                                               [B Load/10 1
                                                                   [B L°a '
                                25

-------
TABLE  2-7a.  MULTIPLE REGRESSION ANALYSES FOR TWO WESTERN COALS ON TWO PULVERIZED-COAL BOILERS
                               Relationship* for Percent Sulfur Emitted of the Form Y • a + bX + cZ
I II
l»CaO/%Al203], [%CaO],
Site (Coal) l«Ha.O/«SiO.) I%N«,O]
Alma
(Sarpy Creek,
Montana)
a
b
c
R2
Fit Correlation
Fremont
(Hanna-Roiebud,
Wyoming)
a
b
c
R2
Fit Correlation

67.61
39.68
-745.05
0.611
(R) 0.78

48.30
188.95
-2903.68
0.313
(R) 0.56

67.21
11.67
-53.28
0.51
0.72

82.94
2.25
-7.95
0.18
0.43
III
l%Na20/\Ca01 ,
Load/105

177.37
-460.40
-3.06
0.59
0.77

74.61
-121.41
25.55
0.70
0.84
IV
(%Na2O/«CaO) ,
Excess Oxyqen

177.66
-438.58
-1.43
0.51
0.71

121.66
-158.40
-3.17
0.049
0.22
V
(%CaO] ,
IMqOl

111.39
-6.79
25.52
0.41
0.64

23.43
-2.31
41.68
0.84
0.92
VI VII
(%CaO/%Mg01 ,
l»CaO/%HgO) Excess Oxygen

5.2 123.
68.3 -6.
-0.
0.020 0.
0.17 0.

2.37 101.
84.72 -24.
10.
0.032 0.
0.18 0.

47
51
76
13
36

16
59
82
84
92
VIII
|»CaO/»Mg01, |!
Load/105 L

241.65
-26.01
-14.62
0.72
0.85

95.64
1.28
-5.23
0.02
0.14
IX
[% CaO/% MgO),
ixceaa Oxygen x 10
Load

250.
-33.
2.
0.
0.

81.
-3.
4.
0.
0.

81
26
31
45
67

24
86
21
38
62
.- X
' [%CaO/%MgO],
-1 f%HgO/%fiiO.l

92.98
20.16
-360.39
0.38
0.62

68.88
0.91
637.09
0.48
0.69

-------
      TABLE 2-7b.   MULTIPLE REGRESSION ANALYSES FOR TWO WESTERN COALS ON TWO PULVERIZED-COAL BOILERS

                    k

                           Relationships for Percent Sulfur Emitted of the Form

                                          BZ
                                 Y = A X e   (or In Y = a •*• b In X + c Z)
to
Site (Coal)
Alma
(Sarpy Creek, Montana)
a
b
c
R2
Fit Correlation (R)
Fremont
(Hanna-Rosebud ,
Wyoming)
a
b
c
R2
Fit Correlation (R)
XI
[% CaO/% MgO] ,
Load/105


7.55
-1.72
-0.18
0.76
0.87



4.53
0.07
-0.07
0.04
0.20
XII
[% CaO/% MgO]
Excess Oxygen x 105
Load


8.28
-2.38
0.03
0.52
0.72



4.39
-0.09
0.04
0.35
0.59
XIII
%CaO ' %SiOp
%AL 0 • %MgO ,
Load/105


3.83
0.25
-0.01
0.31
0.56



5.78
-0.45
-0.22
0.61
0.78
XIV
Excess Oxygen,
Load/105


5.28
-0.29
-0.23
0.96
0.98



4.25
0.29
-0.15
0.32
0.57

-------
       TABLE 2-8.  COMPARISON OF MEASURED AND CALCULATED PERCENT FUEL SULFUR EMITTED
Fuel Sulfur Emitted



Calculated
Based
on Excess
Calculated
Based on
Gronhovda


Oxygen Coefficient

Site/Coal
Alma
Sarpy Creek,
Montana




Fremont
Hanna-Roaebudi
Wyoming




Test
No.


72
74
75
76
78


3
4
S
6
7
Measured
»


85
84
76
86
91


93
87
107
95
87
and Load
%


89
91
83
83
89


98
85
105
94
88
(%)
(A)


100
97
96
97
97


106
105
104
106
106
I
(B)


86
87
77
86
85


93
94
101
88
83
II
(0


89
80
81
85
88


96
96
97
90
81




Calculated Based on
III



90
82
79
83
86


97
84
102
94
92
IV



87
79
81
87
87


98
94
86
84
97
V



89
81
81
86
86


98
86
105
92
89
VI



96
98
96
95
95


92
94
92
91
90








Relationships in Tables 2-7a 6 b (»)
VII



84
82
84
87
86


97
96
105
91
89
VIII



88
82
79
83
99


92
95
94
95
93
IX



89
81
81
83
88


90
94
98
100
88
X



87
87
79
84
84


98
93
101
89
88
XI



88
82
79
83
91


92
95
94
95
92
XII



89
81
80
83
89


90
94
97
99
88
XIII



87
87
80
83
84


98
88
98
98
86
XIV



84
81
76
86
91


93
96
97
96
86
(A),  (B)  and (C)  indicate correlation coefficients used in Figures 2-12 and 2-13 that follow.

-------
      100
       95
     52 90
     B
     W
     w
     Q
     H
       85
     £ so
       75
Gronhovd's

New Coeff.

CaO, NaO
o
D
         75
(A) from  (2)

(B) from Equat. I, Tab. 2-

(C) from Equat. II,
          Tab. 2-6



 O    D
        80           85           90           95


        SULFUR OXIDES EMITTED CALCULATED, %
                                                                     100
Figure 2-12.  Percent sulfur oxides emitted  (measured) vs. percent sulfur
              oxides emitted (calculated). Alma Unit  3, Sarpy Creek,

              Montana coal.
                                       29

-------
  100
I
g
   95
   90
   85
   80
   75
                O   D
                          I
                      I
                           OODD
        (A)  from (2)
        (B)  from Equat.  I,
                   Tab.  2-6
        (C)  from Equat.  II,
                   Tab.  2-6
I
Gronhovd's
New Coeff.
CaO, Na_O


      \	
•  (A)
O  (B)
D  (C)


   I
     75
 80         85        90        95        100

        SULFUR OXIDES EMITTED CALCULATED, %
                   105
                         110
Figure 2-13.
Percent sulfur oxides emitted (measured)  vs.  percent sulfur
oxides emitted (calculated),  Fremont Unit 6,  Hanna-Rosebud,
Wyoming coal.
                                      30

-------
 TABLE 2-9.  SULFUR RETENTION BY THE ASH OF THE COALS TESTED DURING LABORATORY
  ASHING AT 700-750 °C AND SUBSEQUENT MINERAL ANALYSIS BY COMMERCIAL TESTING
Site/Coal Type
Alma/E
Stout/W
Stout/E
Eau Claire/W
Eau Claire/E
Madison/W
Madison/E
Willmar/W
Willmar/E
Fairmont/E
Fairmont/E
Fairmont/Blend
Fairmont/W
St. Johns/W
St. Johns/E
Waupun/Blend RDF
Waupun/W
Waupun/RDF
Fremont/Wyo
Fremont/Wyo
Fremont/Wyo
Fremont/Wyo
Fremont/Wyo
Fremont/Colo


Average
Test No.
9
14
31
7
30
5
14
8
34
3
7
12
—
8
16
2
—
—
3
4
5
6
7
9


Retention
Percent Retention
East West Blend
6.2

1.3

2.6

1.4

2.6
1.1
4.8



15.3









Eastern Coal
(Low CaO+MgO)
7.7

33.0

41.04

65.4

46.2



18.1
54.5
47.9

75.0(W + RDF)
69.2
123.6(RDF)
17.0
10.3
18.8
9.9
8.4
70.8
Western Coal
(High CaO+MgO)
53.1
E = Eastern
W = Western
Wyo = Wymoing  (Hanna-Rosebud)
Colo = Colorado  (Walden)
RDF = Refuse-Derived Fuel
                                      31

-------
        Table 2-10 presents the variations of fuel sulfur retention with cal-
cium to sulfur ratio for a series of lignite samples with and without added
lime that were evaluated in our laboratory.  These experiments are of interest
because it allows an experimental and theoretical comparison of the sulfur
retention properties of a fuel with a known added amount of one particular
metal compound.  In this case the metal was calcium.  Calcium is probably the
most economical metal to be used in the near term to reduce sulfur.  Experiments
sponsored by EPA at Battelle Columbus Labs on a stoker fired boiler using lime
augmented coal briquetts are currently underway.  This briquetting of lime and
coal technique is also being studied by the Ohio Department of Energy.  There-
fore it was of interest to present the results of these laboratory studies
since they are relevant to the topic of sulfur retention.  Figure 2-14 is the
graphical representation of these variations.  Commercial Testing processed
these lignite samples with various molar calcium to sulfur ratios for sulfur
retention under laboratory conditions.  In some cases lime was added to
increase the Ca/S ratio.  The natural lignite had about 20% lime in the ash.
The average sulfur retention of the samples with added lime was 86% while the
average retention of the naturally occurring lignite was 66%.
        Regression analyses of the data to assess possible relationships with
exponential, logarithmic and power functions lead to the power relationship
resulting in the closest agreement.  The power function was of the form

                        Y =

where Y is the percent sulfur retention,
      X is the Ca/S ratio, and
      a and b are the coefficients.
     2
The R  of fit correlation was found to be 0.784.  This correlation accounted
for 88.5% of the data.
        The  data showed that the amount of calcium in the coal does
 significantly  affect the amount of sulfur retained in the ash under  the
 proper  (residence time  and temperature)  conditions.   The boiler conditions
 dictated  how close to the optimum retention the boiler would operate.
                                       32

-------
              TABLE  2-10.  VARIATION  OF FUEL SULFUR RETENTION
                           WITH CALCIUM/SULFUR RATIO
Lignite Samples
Ca/S
0.55
0.64
1.36
1.65
2.63
2.58
1.18
2.80
0.59

% Retention
73.2
69.2
81.3
84.5
92.7
92.9
75.9
88.5
56.0
                    100 i
                     90
                     SO
                   £70
                     60
                     50
                     40
                                    I
Equation of Curve
% Sulfur Retention
• 74.1 lea/Si0'22
R2 « 0.784
R • 0.885
   I
                             0.5     1.0    1.5     2.0
                                  LIGNITE SAMPLE Ca/S RATIO
                                                       2.5
                                                              3.0
Figure 2-14.   Percent sulfur retention  vs. calcium to  sulfur  (Ca/S) ratio
                for  lignite  samples.
                                        33

-------
                                  SECTION 3.0
                THERMOCHEMICAL EQUILIBRIUM SULFUR DISTRIBUTIONS

3.1     INTRODUCTION AND BACKGROUND
        The primary objective of this task was to determine, on a thermochemical
equilibrium basis, the gas-phase and condensed-phase distributions of the fuel
sulfur as a function of coal type, temperature and air/fuel ratio (stoichiometry).
These distributions would establish the extent to which the sulfur was associated
with condensed phase (liquid and solid) species which could be electrostatically
precipitated from the flue gas or collected in the bottom ash.
        A secondary objective was to evaluate which of the coal types investi-
gated would be amenable to greater sulfur retention by augmentation with
suitable additives.  This was only a cursory evaluation and did not identify
sulfur retention sensitivity to augmentation.
        All calculations were performed by a generalized computer program
developed by the National Aeronautics and Space Administration (NASA).  This
program has received wide industrial acceptance and has recently been extended
specifically for greater flexibility in considering coal analyses.

3.2     COMPUTER PROGRAM
        The computer program described in Reference 2 was used to calculate
the thermochemical equilibrium composition of four coal types over ranges in
both temperature and air/fuel weight ratios.  This program, which has been
under development for many years, can consider up to 200 distinct species of
which a maximum of 100 may be condensed (liquid or solid).
        The coal composition is specified as part of the input and the program
searches an extensive thermochemical file to select those species which can be
formed from the chemical elements present in the coal.  The user can specify
that up to 66 species be omitted from those selected if it is known, a priori,
that these species are unimportant.

                                       34

-------
        The program then starts an iterative procedure to find product mole
fractions subject to the problem constraints.  In this instance the tempera-
ture, pressure  (one atmosphere), and elemental composition are the known
constraints.  The program then cycles to the next set of constrainst using
the previous solution as an initial estimate of species concentrations.
        At low temperature, the solution obtained may be somewhat inaccurate
because of uncertainties in species thermochemical data and the assumptions
that all gases are ideal and interactions among phases may be neglected.
        The calculations were performed on an UNIVAC 1108 with certain key
variables expressed in double precision.

3.3     COAL COMPOSITIONS
        Table 3-1 contains the coal compositions weight percentages, on a dry
basis, of the four coals investigated in the equilibrium calculations.  Chlorine
was omitted from lignite, augmented lignite and Pittsburgh #8,since its
inclusion caused the species count to exceed the 200 limitation.  This was
also justifiable since its maximum concentration was 0.02% in the coal.
Phosphorous pentoxide  (p~O,.) was not included as an ash constituent because of
its low concentration.  The ash metal oxide concentrations shown in Table 3-1
reflect their abundance in the coal and not in the ash.
        These coals were selected to cover the range of coal types in terms
of ash composition and as well as to be representative of the coals tested in
the field study.  The Montana coal was actually one of the test coals.  The
Pittsburgh coal was similar to the eastern coals tested as well as being a
major steam coal.  The lignite were investigated since there was laboratory
experimental data available for comparison.  The augmented lignite served as
a case where a controlled amount of calcium had been added as well as having
combustion laboratory data on this coal.
        •
        As shown, there is only a factor of 2 difference in the sulfur content
of the coals, and this factor could increase to 3.5 to 4 for different eastern
coals.  Even more pronounced is the difference in calcium (as CaO) content
among the coals, with Pittsburgh #8 being an order of magnitude less than the
next lower value.  Further, Pittsburgh #8 has the lowest concentrations of
magnesium (as MgO) and sodium (as Na,0).  The impact of these low concentrations
will be discussed later in more detail.
                                      35

-------
                                       TABLE  3-1.  COAL COMPOSITIONS
Weight Per
Coal C H N 0 S Ash
Montana 69.78 6.51 0.96 8.70 1.05 13.00
Lignite 66.41 4.45 1.31 17.12 1.00 9.70
Augmented
Lignite 59.27 4.58 1.10 20.99 0.98 13.07
Pittsburgh
#8 77.45 5.19 1.51 6.71 1.84 7.28
cent, Dry
SiO? A12°T Tiop Fe2°T Ca° Mg° K?° Na?°
4.34 4.15 0.13 1.50 1.50 0.33 0.08 0.96
3.72 1.68 0.12 0.73 1.98 0.78 0.04 0.09
3.45 1.47 0.10 0.61 5.39 0.68 0.08 0.07
3.59 1.81 0.08 1.42 0.15 0.05 0.11 0.02
U)
o\

-------
3.4     COMPUTER RESULTS
        A total of 160 discrete point calculations were obtained for the
following conditions:
        Pressure - 1 atmosphere
        Temperature - 3300, 2900, 2500, 2100, 1700, 1300, 900, 500 °F
        Stoichiometry - 50, 75, 100, 125,  150% theoretical air (by weight)
The calculations were performed in decreasing temperature steps in order to
minimize computer time, i.e., the solutions were  first obtained with the
fewest number of condensed species present.  Table  3-2 presents the computer
output for  lignite coal at 50% theoretical air.   The density and mole fraction
                                                             —4
print format is interpreted as follows:  8.4421-4 = 8.4421x10  .  The last
part of Table 3-2 lists those species whose concentrations were less than
1x10    (1 ppm) throughout the temperature  range.
        A sulfur mass balance was established for each of the 160 point
calculations in order to determine which species  were combined with sulfur
as a function of temperature and Stoichiometry.   The resulting distributions
were then summed by species phase, gas vs. liquid/solid.
        The results of the sulfur mass balance for each coal are presented
in Tables 3-3 to 3-6.  Only those values greater  than, or equal to, 0.1% are
shown in order to improve their readability.  The values in Tables 3-3 to
3-6 represent the weight percentage of the total  sulfur associated with
each species.  For example, in Table 3-3 at 50% theoretical air and 3300 °F,
the sulfur contained in the COS molecule represents 3.6% of the total sulfur
mass in the system.  Similarly, H S contains 36.3% of the total sulfur, etc.
Further, all the sulfur is combined with gas-phase species.  Conversely, at
500 °F  97.4% (48.0 + 2.5 + 46.9) of the sulfur is associated with condensed
species (L - liquid, S - solid).
        Table 3-7 was prepared by summing  up the  sulfur content of the
condensed species for each of the 160 discrete point calculations.  As
anticipated, low temperatures favor sulfur retention by condensed species,
i.e., except for Pittsburgh #8 over 90% of the sulfur is associated with
condensed species for temperatures of 900  °F and  less.
                                      37

-------
   09/15/78  10152111 COAL
                          TABLE  3-2.   COMPUTER OUTPUT FOR LIGNITE AT 50% THEORETICAL AIR

                          OI30AA25     000150          9     100                                  DATE  091578

                                         THERMODYNAMIC EQUILIBRIUM  PROPERTIES  AT  ASSIGNED

                                                     TEMPERATURE  AND  PRESSURE
   CASE NO.
            CHEMICAL FORMULA
FUEL
FUEL
FUEL
FUEL
FUEL
FUEL
FUEL
FUEL
FUEL
C 1.00000
31 1,00000
AL 2.00000
TI 1.00000
FE 2.00000
CA 1.00000
MG 1.00000
K 2.00000
NA 2.00000
OXIDANT N 1,56180

0/F* a. 2373
H .79670
0 2.00000
0 3.00000
0 2.00000
0 3.00000
0 1.00000
0 1.00000
0 1.00000
0 1.00000
0 .41960
PERCENT F
                                         .01690
                                                   .00570
                      .19350
                                     AR  .00930

                                    .•  19.0936
                                               C    .00030

                                               EQUIVALENCE  RATIO.  1.8211
                                                                        PAGE
NT FRACTION
(SEE NOTE)
.902982
.037203
.016812
.001154
.008673
.023369
.007790
.000960
.001057
1.000000
ENERGY STATE TEMP
CAL/MOL
.000
.000
,000
.000
.000
.000
.000
.000
.000
,000
DEC K
.00
.00
.00
.00
.00
.00
.00
.00
.00
.00
DENSITY
c/cc
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
                                  PHI* 2.0000    REACTANT DENSITY*   .0000
w
00
THERMODYNAMIC PROPERTIE8


P, ATM           1.0000   1.0000   1.0000    1.0000    1.0000    1.0000    1.0000    1.0000
T, DEC K         2089.0   1667.0   1644.0    1422.0    1200,0     976.0     756.0     533.0
RHO, G/CC      1.5750*4 1.7657-4 2.0060*4  2,3193-4  2,7484*4  3,3729*4  4.9846*4  7.3352-4
H, CAL/G           23.2    *S9.3   -136.1    -210.2    -263.3    -355.7    -596.0    -692.1
8* CAL/C6)(K)    2,3404   2,2967   2,2549    2,2065    2,1506    2.0640    1,6075    1,6603
   M, MOL NT
   (DLV/DLP)T
   (DLV/DLT)P
   CP, CAL/(6)(K)
   GAMMA (3)
   SON VEL.M/8EC
                 26.996   27.050   27.061
               •1.00099 -1.00036 -1.00003
                 1.0233   1.0069   1.0007
                  .3645    .3562    .3369
                 1.2492   1.2652   1.2792
                  696.5    852.1    803.8
  27.062   27.062   27.067   30.923   32.061
•1.00001 -1.00002 -1.00009 -1.01272 -1.00095
  1.0001   1.0002   1.0019   1.2567   1.0201
   .3313     .3270     .3247     .6526     .2964
  1.2648   1.2697   1.2935   1.1665   1.2740
   749.2     689.5     623.4     486.9     419.5
(S)  = Solid
   MOLE FRACTIONS
AL203CS)
AR
C(3)
CO
COS
CQ2
CAO(S) i
CAOH <
CA02H2(S)
CA02H2 '
CA3(S)
FE '
FEO(S)
FEO(L)
FEQ
,4421-4
.9670*3
.0000 0
.4540-1
.4013-5
.7895-2
i. 1209-3
2.942 -6
.0000 0
»,569 -6
.0000 0
S.206 -4
.0000 0
.0000 0
1.007 -5
6.
6.
.
2.
1.
«.
1.
1.
.
1.
3.
4.
•
5.
«.
4514-4
9736-3
0000 0
4265-1
0594-4
0875-2
7976-3
736 -7
0000 0
536 -6
3671-4
560 -5
0000 0
0145-4
659 -7
6.
6.
.
2.
5.
4,
1.
«.
.
1.
1.
1.
5.
.
7.
4543-4
9762-3
0000 0
3852-1
0240*5
5157-2
0292-3
548 .9
0000 0
456 .7
1074-3
770 -6
5293-4
0000 0
919 .9
8.4546-4
6.9765-3
,0000 0
2.3311-1
1.6590-5
5.0615-2
7.2344-4
3.742-11
,0000 0
6,357 -9
1,4134-3
1.674 -8
5.5669-4
.0000 0
2.746-11
6
6

2
4
5
5
4

8
1
3
5

1
.4546-4
.9766-3
,0000 0
.2547-1
.6679*6
,6272*2
.7952-4
,927-14
.0000 0
.131-11
.5573-3
.515-11
.5697-4
.0000 0
.072-14
6.4555-4
6,9772-3
,0000 0
2,1499-1
6,1142*7
6,6758-2
5,2979-4
2.929-18
,0000 0
1.261-13
1.6072-3
3.656-15
5.5702-4
.0000 0
1.052-19
6.4555-4
6.9772-3
1.2359-1
1.6566-2
3.9398*8
1,4361-1
5.7560-4
3.026-25
.0000 0
3.061-17
1.5612-3
6.920-23
5.5702-4
.0000 0
8.592-28
8.4719-4
6.9907-3
1.5369-1
4.6367*5
1.6639*6
1,2962*1
.0000 0
.000 0
6.6600-4
3.757-27
1,4551-3
,000 0
.0000 0
,0000 0
.000 0

-------
                                             TABLE    3-2.   (Continued)
vo
   09/15/79  10152111  COAL    0130AA25
000130
100
FE02H2
FE304(S)
H
H2
H20
H28
K
KOH
K202H2
K2S04(3)
MG
MCCOJ(S)
HCO(S)
HGOH
MC02M2
N6TI205(S)
MG2TIOa(S)
MC2TI04U)
NO
N2
NA
NACN
NAOH(L)
NAOH
NA2S04(8)
OH
8
SH
80
302
820
SIO
8102(8)
8102(8)
3102(8)
8I02U)
8102
SIS
2.538 .5 9.230 -6 2.243 -6 2.553 -7 1.212 -8 1.272*10 6.426-13 7,121-19
.0000 0 .0000 0 .0000 0 .0000 0 .0000 0 .0000 0 .0000 0 1.8603-4
7.300 -4 1.576 -4 2.250 -5 1.788 -6 5.649 -8 3.778-10 8.290-14 9.273-21
6.4144-2 6,6778-2 7.0555-2 7.5973-2 8.3634-2 9.4147-2 4.5676-2 3,1254-3
4.7897-2 «.5403-2 4.2180-2 3.7023-2 2.9476-2 1.8969-2 6.7465-2 1.0962-1
4.5112-4 8.1685-4 4.3284-4 1,8302-4 5.4036-5 8.5603-6 3,1908-6 2.4160-5
8.634 -5 7..98J -5 6.927 -5 5.345 -5 3.258 -5 1.269 -5 1.329 -9 4.571-22
1.804 -5 2.465 -5 3.525 -5 5,107 -5 7.192 -5 8,874 -5 7.470 -7 2.657-16
2.172-13 1.489-12 1.617-U 3.051-10 1.242 -8 1.552 -6 1.380 -7 6,934-21
.0000 0 .0000 0 .0000 0 .0000 0 .0000 0 .0000 0 5.1754-5 5.2366-5
6.486 -5 2.736 -6 4.692 -8 2.286-10 1.522-13 3,635-18 7.030-27 .000 0
.0000 0 ,0000 0 .0000 0 .0000 0 .0000 0 .0000 0 .0000 0 9.5578-4
7.6560-4 8.3867-4 8.4259-4 8.4273-4 8.4275-4 8.4282-4 8.4282-4 .0000 0
7.094 -6 4.204 -7 1.113 -8 9.348-11 1.276-13 8.088-18 9.417-25 .000 0
3.758 -6 5.729 -7 5.108 -8 2,07l -9 2*411-11 3,292-14 6.621-18 4.442-27
.0000 0 .0000 0 .0000 0 .0000 0 ,0000 0 .0000 0 ,0000 0 3,7109-5
.0000 0 7.4039-5 7.4065-5 7,4068-5 7.4069-5 7.4075-5 7.0075-5 .0000 0
7.3913-5 .0000 0 .0000 0 .0000 0 ,0000 0 ,0000 0 .0000 0 ,0000 0
7.902 -6 6.917 -7 3.074 .8 5.104-10 1.806-12 4.637-16 1.632-20 7.689-29
5.8739-1 5.8797-1 5.8817-1 5.8819-1 5.8821-1 5.8824-1 5.8825-1 5.8939-1
1.631 -4 1.599 .4 1.544 .4 1.449 -4 1.265 -4 2.890 -5 4.128-10 4.242-21
2.315 -9 6.783 -9 2.670 -8 1.635 -7 1.949 -6 2.171 -5 8.306-10 1.973-20
.0000 0 .0000 0 .0000 0 .0000 0 .0000 0 1.0111-4 1.7492-4 .0000 0
1.127 -5 1.463 -5 2.021 -5 2.960 -5 4.632 -5 2.319 -5 1.480 -8 5.338-17
.0000 0 .0000 0 .0000 0 .0000 0 ,0000 0 ,0000 0 ,0000 0 8.7635-5
6.283 -5 8.063 -6 5.839 .7 1,831 -8 1.535-10 1,354-13 2.107-17 7.622-25
6.039 -5 1.6B8 -5 5.715 -7 6.650 -9 1.451-11 1.864-15 2.103-20 3.945-27
2.400 -4 1.330 -4 1.551 -5 9.039 -7 1.772 -8 5.402-11 6.096-14 2.363-17
3.383 -4 7.736 -5 2.898 .6 3.725 -8 8.969-11 1.235-14 2.852-18 9.015-23
4.323 -4 1.264 -4 6.470 -6 1.218 -7 4.825-10 1.296-13 1.635-15 5.627-17
1.737 -6 8.765 -7 2.227 .8 1.666-10 1.852-13 7.819-18 5.261-21 2.284-22
3.534 -4 1.064 -5 1.142 -7 2*992-10 8.419-14 5.511-19 1.264-28 .000 0
.0000 0 .0000 0 .0000 0 .0000 0 .0000 0 .0000 0 3.1753-3 3.1815-3
.0000 0 .0000 0 .0000 0 .0000 0 .0000 0 3.1753-3 .0000 0 .0000 0
.0000 0 3.1628-3 3.1747-3 3.1750-3 3.1751-3 ,0000 0 .0000 0 .0000 0
2.6121-3 .0000 0 .0000 0 .0000 0 .0000 0 .0000 0 .0000 0 .0000 0
1.065 -6 2.050 -6 1.221-10 1.461-13 1.368-17 1.810-23 6.277-33 .000 0
4.106 -6 2.690 -7 1.932 -9 2.978-12 4.032-16 9.099-22 3.868-32 .000 0
DATE 091578
PACE
                                                                                                     (S)  = Solid
   ADDITIONAL PRODUCTS MHICH MERE CONSIDERED BUT  WHOSE  MOLE  FRACTIONS  MERE  LESS  THAN     .10000-05 FOR ALL ASSIGNED CONDITIONS
AL
CN
FES(8)
K(8)
MGN
N20
NA2804C8)
SI
TIO(8)
TI305(8)
AL02
CS
FE8(8)
ML)
MGO(L)
NA(S)
NA2804(8)
SIH
TIO(S)
TI305(8)
AL02H
CS2
FES(L)
KO
MGO
NA(L)
NA2804U)
TI(S)
TIO(L)
TI30SCL)
AL20
C2H
FE804O)
K2
HG02H2O)
NAH
NA2S04
TH3)
TIO
TI407(8)
AL202
CA
FES2(S)
K20(8)
M68(8)
NAO
0
TKL)
TI02(8)
TI407U)
AL203U)
CAO
FE203(S)
K2804(8)
HGS
NAOH(S)
02
TI
TI02U)

C
CAS04(S)
FE2S3012O)
K2S04(L>
MGSOU<8)
NA2
8(8)
TIC(S)
TI02

CH
FE02H2(S)
HCN
MG(8)
MCSOflCL)
NA20
8(L)
TIC(L)
TI203O)

CH2
FE03H3(8)
H2S04(L)
HG(L)
MGTI205CL)
NA202(8)
803
TIN(8)
TI203(S)

CH20
FE8(S)
H2804
MGH
N02
NA202O)
8KS)
TIN(L)
TI203U)

   NOTE. HEIGHT FRACTION OF FUEL IN TOTAL FUELS AND OF  OXIDANT IN TOTAL  OXIDANTS

-------
                          TABLE  3-3.   SULFUR DISTRIBUTION, MONTANA COAL
Species
COS
CaS(S)
caso4(S)
FeS(S)
V
"V»4
N.2S04(S,
Na S04 (L)
Na2S04
s
SH
SO
"2
s2o
sis

50» TA
Temperature, 10
33 29 25 21 17
3.6



36.3




4.9
16.8
18.0
20.0
0.2
0.3
5.9
8.7


65.0




1.0
9.2
4.1
5.9
0.1

2.8
60.8


34.8





1.1
0.2
0.3


1.3
80.9


17.7





0.1




1.1
80.9


18.0










2-F
13
0.6
80.9

6.9
11.6










9
0.1
80.9

8.1
8.4
2.5









5

48.0


2.6
2.5
46.9








Woiqht % of Total Sulfur
33
0.1



0.7




0.4
0.7
11.1
87.0


29
0.8



5.0




0.3
1.4
8.7
87.3


75% TA
Temperature, in °F
25 21 17 13 9
4.9



37.0




0.1
2.3
4.1
51.7


3.G
59.0


35.1





0.3
0.1
2.0


1.3
80.9


17.8










0.8
80.9


18.3










0.1
80.9

7.9
8.6
2.5









5

48.8


1.8
2.5
46.9








33











0.6
99.4


29











0.1
99.9


1001 TA
Temperature, 10 *F
25 21 17 13 9 5








0.1



99.9









32.0
0.7



67.4







1.9

46.7




51.4




45.6

0.6
2.5
46.9





4.5



6.6
43.6

0.5
2.5
46.9









12.2
36.9

1.5
2.5
46.9








Note i  Only non-zero entries are shown.
 (s)  = solid
(continued)

-------
                              TABLE 3-3  (Continued).
Species
COS
CaS(S)
CaS04(S)
FeS(S)
W*
Na2S04(S)
Ha2S04(L)
Na2S04
s
SH
SO
"2
"3
SiS
Weight % of
125* TO
Teoperature, 10 °?
33 29 25 21 17 13 9 5










0.2
99.8
0.1












99.8
0.2








1.3



98.1
0.4



22.7



43.8
0.8



3?. 3
0.4



51.0

2.2

46.8









50.6

2.5
46.9










50.6

2.5
46.9










50.6

2.5
46.9








Total Sulfur
150% TA
Temperature, 10 °F
33 29 25 21 17 13 9 5











99.9
0.1












99.8
0.2








1.4



98.1
0.5



25.5



43.5
1.0



29.6
0.4



51.0

2.2

46.8









50.6

2.5
46.9










50.6

2.5
46.9










50.6

2.5
46.9








Note:  Only non-zero entries are shown.
(s)  =  solid

-------
                                     TABLE 3-4.   SULFUR DISTRIBUTION,  LIGNITE
Species
COS
CaS(S)
CaS04 (S)
H2S
WS)
Na2S04(S)
Na2S04(L)
Na2S04
S
SH
SO
so2
so3
s2o
SiS

33
4.0


28.0




5.0
14.9
21.0
26.8

0.2
0.3
29
6.6
20.9

50.6




1.1
8.2
4.8
7.8



50» TA
Temperature, 10 T
25 21 17 13
3.1
68.5

26.8





1.0
0.2
0.4



1.2
87.5

11.3





0.1





0.3
96.4

3.3












99.4

0.5











9

96.6

0.2
3.2










5

89.9

1.5
3.2
5.4









Weight % of Total Sulfur
33
0.1


0.4




0.4
0.5
10.1
88.5



29
0.7


3.2




0.3
1.1
8.2
86.6



75* TA
Temperature), 10 °F
25 21 17 13
5.2


27.9




0.1
2.0
4.4
60.3

0.2

3.7
68.2

25.7





0.2
0.1
2.1



0.8
90.6

8.6











0.1
98.2

1.7











9

96.6

0.2
3.2










5

90.3

1.0
3.2
5.4









33










0.6
99.5




100\ TA
Temperature, 10
29 25 21 17










0.1
99.9














100.0









0.3
0.6



99.1





8.7

3.0

5.3




83.0




2 «F
1395


85.3
1.0
3.2
5.4





5.0




12.0
79.0
0.3
3.2
5.4










17.2
73.4
0.8
3.2
5.4









Is)
         Hotei  Only non-zero entries are shown.
         (s) = solid
(Continued)

-------
                                                   TABLE  3-4  (Continued).
it*
W
Species
COS
CaS(S)
CaS04(S)
H2S
K2S04(S)
Na2S04(S)
Na2S04(L)
Na2S04
S
SH
SO
so2
so3
s2o
SIS
Weight * of Total Sulfur
125* TA
Temperature, 10 *F
33 29 25 21 17 13 9 5










0.2
99.8
0.1













99.8
0.2













99.6
0.4




67.1



2.9
0.8



29.0
0.3




91.7

3.0

5.3










91.4

3.2
5.4











91.4

3.2
5.4











91.4

3.2
5.4









ISO* TA 2
Temperature, 10 °F
33 29 25 21 17 13 9 5











99.9
0.1













99.8
0.2













90.5
0.5




69 . 6



2.6
0.9



26. f.
0.4




91.7

3.0

5.3










91.4

3.2
5.4











91.4

3.2
5.4











91.4

3.2
5.4









                    Note:  Only non-zero entries are shown.
                    (s) =  solid

-------
                    TABLE 3-5.   SULFUR DISTRIBUTION,  AUGMENTED LIGNITE
Species
COS
CaS(S)
CaS04(S)
H2S
K2S04(S)
Ha2S04(S)
Ha2S04(L)
S
SH
SO
"a
"3
s2o
SIS

50» TA
Temperature, 10 *P
33 29 25 21 17 13



25.8



4.3
13.3
21.3
31.7

0.2
0.2

6.1

58.7



1.1
9.3
6.1
11.7

0.2


63.4

31.4




1.1
0.2
0.6




85.3

13.4




0.1





0.3
95.7

4.1










99.3

0.7










9 5
98.1

0.2
1.7









100.0












Weight % of Total Sulfur
33
0.1

0.5



0.3
0.5
9.9
88.7



29
0.7

3.4



0.3
1.1
7.9
86.7



75» TA
Temperature, 10 *P
25 21 17 13 9 S
4.7

28.8



0.1
1.9
4.2
60.0

0.2

3.4
66.5

27.5




0.2
0.1
2.2



0.8
89.9

9.3










0.1
98.1

1.8










98.1

0.2
1.7









92.fi

1.2
1.8
4.5








100* TA
Temperature, 10 *F
33 29 25 21 17 13 9 5








0.6
99.4











0.2
99.9











0.1
99.9












100.0





0.1
1.2

4.3



94.5



0.1
17.4
66.9
3.3
1.8
4.5




6.1



37.7
55.7
0.4
1.8
4.5








42.8
50.0
1.0
1.8
4.5








Note:  Only non-sero entries are shown.
(s) -  solid      \
(Continued)

-------
                              TABLE  3-5  (Continued).
Species
COS
CaS(S)
CaS04(S)
K.,S04(S)
Na2S04(S)
Na2S04(L)
H.2S04
S
SH
SO
so2
so3
s2o
SiS
Hoiqht \ of Total Sulfur
125% TA
Temperature, 10 *F
33 29 25 21 17 13 9 5









0.2
99.8
0.1












99.8
n.2












99.fi
0.4




69.9


2.0
0.7



?7.P
0.3




94.0
1.5

4.4










93.8
1.8
4.5











93.8
1.8
4.5











91. n
i.a
4.r>









150t TA ,
Temporal uro , 10" °F
33 29 25 21 17 13 0 5










99. 9
.1.1












99. fi
0.2












99. S
n.s




72.4


1.7
n.n


94..
..S

4...




.'4.7
n.4










9 i.n
I.H
4.5











91.11
I.H
4 . S






•>-..„
1 ."
4.'.




i








Note:  Only non-zero entries are shown.
 (s)  = solid

-------
                         TABLE 3-6.   SULFUR DISTRIBUTION,  PITTSBURGH #8
Species
COS
CaS(S)
CaS04(S)
FeS(S)
FeS(L)
FeSj(S)
Fe2(S04)3(S)
H2S
£.
HgS04(S)
Na2S04(S)
Ha2S04(U
S
SH
SO
S02
"3
s2o

50% TO
Temperature, 10 °F
33 29 25 21 17 13
4.7



35.5




5.9
18.2
18.3
17.3

0.3
8.0




65.9




1.3
10.4
4.3
5.3

0.2
7.2

19.7


65.2




0.1
2.3
0.3
0.5


5.7
31.9



57.4





0.3




5.0
32.0



58.3










4.5
32.0



58.9










9
0.7
32.0



59.8
2.2

0.7







5



63.9

28.6
2.2

0.7







Weight % of Total Sulfur
33
0.2



0.6




0.4
0.6
11.1
87.2


29
0.9



4.0




0.3
1.3
8.8
84.6

0.1
75% TA
Temperature, 10 °F
25 21 17 13
5.8



31.7




0.2
2.2
4.4
55.4

0.3
11.0




77.8





0.7
0.3
5.4

0.1
5.7
31.9



57.6










3.7
31.9



59.6










9
1.1
31.9



59.4
2.2

0.7







5



63.9

28.6
2.2

0.7







33











0.6
99.5


100% TA
Temperature, 10 "F
29 25 21 17 13 9 5











0.1
99.9














100.0














100.0








2.1


0.6



92.6








2.2

0.7




92.5







1.6
2.2

0.7




90.9





4.6

0.2
2.2
2.1
0.7




85.6


Mote:  Only non-zero entries are shown.
 (s)  = solid
                                                                                            (Continued)

-------
                             TABLE  3-6  (Continued).
Species
COS
CaS(E)
CaS04(S)
PeS(S)
FeS(L)
PeS2(S)
Fe2(S04)3(S)
H2S
H2S04
KjSC^IS)
KjSO^IL)
HgS04(S)
Ha2S04(s>
Na2S04U>
Ha2S04
S
SH
SO
so2
so3
s2o
Weight t of Total Sulfur
125% TA
Temperature, 10 'f
33 29 25 21 17 13 9 5















0.2
99.8
0.1

















99.8
0.2

















99.6
0.4


4.7






0.9



0.3



93.1
1.1


4.7





2.2



0.7




87.9
4.6


4.7





2.2

2.1
0.7





61.3
29.1


4.7'


47.9

0.3
2.2

2.1
0.7





2.4
39.8


4.7


47.9

36.7
2.2

2.1
0.7






5.8

150% TA 2
Temperature, 10 *F
33 29 25 21 17 13 9 5















0.1
99.8
0.1

















99.8
0.2

















99.5
0.5










0.8



0.3



92. B
1.4









2.2



0.7




86.7
5.8









2.2

2.1
0.7





55.9
34.5






47.9

0.3
2.2

2.1
0.7





1.9
40. 3






47.9

35.8
2.2

2.1
0.7






6.7

Notei  Only non-zero entries are shown.
(s)  =  solid

-------
                            TABLE  3-7.  SULFUR RETENTION BY CONDENSED SPECIES


                                           Weight % of Total Sulfur
*>
GO
Coal
Montana




Lignite




Augmented Lignite




Pittsburgh #8




% TA
50
75
100
125
150
50
75
100
125
150
50
75
100
125
150
50
75
100
125
150
3300
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2900
8.7
0
0
0
0
20.9
0
0
0
0
6.1
0
0
0
0
4.7
0
0
0
0
2500
60.8
0
0
0
0
68.5
0
0
0
0
63.4
0
0
0
0
24.3
0
0
0
0
Temperature
2100
80.9
59.0
32.0
66.5
68.9
87.5
68.2
0.3
69.9
72.1
85.3
66.5
0
72.0
74.2
36.6
4.7
0
5.6
5.5
, °F
1700
80.9
80.9
48.6
100.0
100.0
96.4
90.6
17.0
100.0
100.0
95.7
89.9
5.5
100.0
100.0
36.6
36.6
7.4
7.5
7.5
1300
87.8
80.9
95.0
100.0
100.0
99.4
98.2
94.0
100.0
100.0
99.3
98.1
90.5
100.0
100.0
36.6
36.6
7.5
9.6
9.6
900
91.5
91.2
99.5
100.0
100.0
99.8
99.8
99.7
100.0
100.0
99.8
99.8
99.7
100.0
100.0
39.5
39.5
7.5
57.5
57.5
500
97.4
98.2
98.6
100.0
100.0
98.5
99.0
99.2
100.0
100.0
100.0
98.8
99.1
100.0
100.0
71.4
71.4
14.2
57.5
57.5

-------
        As previously mentioned, Pittsburgh #8 had a low calcium content in
comparison with the other coals—by at least a factor of 10.  An examination
was made of the computer output at 500 °F for all coals in order to perform
calcium, potassium and sodium mass balances with the results shown in
Table 3-8.  The results were that all the calcium in Pittsburgh #8 combined
with sulfur to form CaS(s) at 50 and 75% theoretical air, and form CaSO (s)
at the higher air levels.  The calcium in the other three coals was present
in sufficient quantities so that it formed Ca(OH) (s) , a non-sulfur containing
compound, in addition to CaS(s) and CaSO.(s).  The additional calcium  (as
CaO) in augmented lignite appears to be converted directly to additional
Ca(OH)_(s), instead of forming additional condensed sulfur compounds.

        Aside from augmented lignite at 50% theoretical air, all the potassium
and sodium was associated with their respective  sulfates.
        Based on the results of thermochemical equilibrium considerations, it
may be possible to increase the condensed phase  sulfur retention of
Pittsburgh #8 coal by augmentation primarily with calcium  (as CaO).  Augmenta-
tion with potassium and/or sodium does not appear to offer significantly
greater condensed phase sulfur retention.

3.5     DISCUSSION OF THE EQUILIBRIUM RESULTS
        The potential performance of sulfur retention by the ash for different
combustion modes can be demonstrated by observing the predicted equilibrium
ash composition at the various theoretical air levels and temperatures for the
Montana coal shown in Table 3-3.  The combustion modes considered  are:
        .  pulverized coal combustion
           fuel bed coal combustion
           cyclone coal combustor
        The degree of sulfur retention in each of these combustion systems
is governed by the equilibrium consideration of:
           ash composition
           temperature
           stoichiometry
                                      49

-------
                   TABLE  3-8.  MASS BALANCES FOR CALCIUM, POTASSIUM AND SODIUM AT  500  °F


                                     Weight Percent of Total Element
Coal
Montana
Lignite
Augmented
Lignite
Pittsburgh 18
Element
Calcium
Potassium
Sodium
Calcium
Potassium
Sodium
Calcium
Potassium
Sodium
Calcium
Potassium
Sodium
50
40.6* CalOII). IS),
Si. 4% CaS 1ST

32.0» Ca(OH) IS),
68.3% CaS 1ST

2 4
100% CaS (S)
100% K2(OH)2
100% NaOH (S)
100% CaS (S)


Percent Theoretical Air (by Weight)
T> ion 125 no
39.7% C.I (Oil), IK), 19.2% Ca(OII) (S), 37.4% Ca(OH) IS), 37 .4% r,i (OH) , (S) ,
&0.3\ CaS (St r>.l% CaS 1ST, 62. 6\ CaSO TS) r,2.f>\ CaPO Ts)
4S.7\ CaS04 (S) * 4

31.7% Ca (OH), (S), 31.5% Ca (OH) (S) , 30.9%Ca(OH* (S) , 30.9%Ca(OH) (S) ,
68. 3\ CiS (St 13.0% CaS ISj, 69.1% CaSO TS) 69.1% CaSO TS)
55.5% CaS04 (S) * *

75.6% Ca (OH). (S), 75.5% Ca(OH). (S) , 75.3%Ca(OH) (S) . 75.3%Ca(OH) (S) ,
24.4% CaS (ST 11.3% CaS (ST, 24.7% CaSO TS) 24.7% CaSO TS)
lj.2% CaS04 (S) 4





Ul
o

-------
On top of these considerations must be added
        .  mixing or contact of sulfur with metals
           kinetic limitations of the sulfur reactions
           temperature and stoichiometry as a function of time
           in the combustor
Each of these factors will be discussed for each combustor type listed above.
        The equilibrium calculation show that calcium and sodium are the major
species that combine with sulfur and form liquids or solids at temperatures in
the furnace.
3.5.1   Pulverized Coal
        In a pulverized coal flame the reactants are fairly well mixed so that
good contact of the sulfur and metals should occur.  However when the coal
particles approach the flame they are heated and begin to devolatilize the
carbon, hydrogen, and sulfur.  The metals in the ash are concentrated in the
particle until such time as they are heated to their melting point or vaporize.
In a pulverized coal flame it is very difficult to make the gas phase fuel
rich.  The overall bulk stoichiometry may be fuel rich but in the flame the
rate of devolatilization and combustion is not sufficiently rapid to make the
gaseous region surrounding the coal particle fuel rich.  Therefore there is
always oxygen available to form sulfur oxides.  This along with the equilibrium
constraints are the reasons that large amounts of SO  are formed even in sub-
stoichiometric flames.
        The temperature and stoichiometry history of the coal particle can
severely affect the sulfur retention.  For example, as the particle heats
up it passes through a low temperature fuel rich region where the predicted
equilibrium products are calcium sulfide.  However, if these products are
formed in this stage they ultimately pass into a high temperature oxidizing
region where the favored equilibrium products are SO_.  Controlling the
temperature of this stage of the flame can shift the favored equilibrium
products to CaSO  and Na SO..
        It is interesting to note that the same control measures that favor
low NO  emissions from P.C. coal flames are also the condition that should
      x
favor high sulfur retention by the metals in the coal ash.  These conditions
                                      51

-------
 are  staged  combustion with  a  fuel rich  first stage  followed by excess  air
 addition  to render  the mixture oxidizing.  However  this excess air addition
 stage is  critical in terms  of both NO   and sulfur retention.  NO  emissions
                                     2C                          X
 are  a strong function of excess air in  the second stage.  The goal in  terms
 of NO  is to supply just enough second  stage air to complete carbon burn out.
     X
 This will be the minimum acceptable NO  point.  In  the case of sulfur  reten-
                                      Xt
 tion, increasing the excess air in the  second stage favors the condensed
 sulfate below 2500  °F.  Table 3-3 shows that a minimum in the condensed phase
 sulfur species occurs at the  stoichiometric point,  TA = 100, at the optimum
 retention temperature, below  2500 °F.   Condensed phase sulfides are formed at
 low  stoichiometric  ratios,  this shifts  to the sulfates at high stoichiometric
 ratios.  Therefore  the conditions for high sulfur retention predicted  from
 thermodynamic equilibrium are temperatures below 2500 °F and theoretical air
 of 125%.
        The  reactivity of sodium compounds such as  sodium bicarbonate with
SO   is well  known and forms the foundation for the  dry SO  adsorption
  ^                                                      ^
processes using nahcolite (mostly NaHCO,)  and trona (mostly Na_CO ).
        The  reaction of sodium with SO_ is thought  to proceed via an
adsorption step followed by reaction to form the sulfate.  This has been
demonstrated  in baghouses by  Shah, et al. (Ref. 3)  in which a filter cake
containing nahcolite continued to remove SO  from the flue gas stream after
the  sorbent  injection had been stopped.  The reactions also occur in suspension
presumably by adsorption onto the sorbent particles.
        The  reaction of calcium with SO_ is also thought to be a  heterogeneous
process.  Therefore the contact and mixing processes at the lower temperatures
is important.  In pulverized  coal flames 80 to 90 percent of the ash is still
suspended in  the flue gas in  the convective section where the temperatures
for  good sulfur capture occur.  For the case where  sufficient sodium is
present in the ash  the only parameter limiting the  attainment of the full
thermodynamic equilibrium product would be kinetic  considerations.  Such
kinetic limitations might be:
           insufficient surface area
           inactive surface
                                       52

-------
        It is well established that sodium can capture sulfur via a
heterogeneous reaction with SO .  However the reaction of calcium with
sulfur under reducing conditions can form the sulfide.  This reaction is
more than likely heterogeneous, as well as the reaction steps that take the
calcium sulfide to calcium sulfate.  Calcium therefore has a fuel rich
reaction mode that the sodium doesn't have.  This mode may be important
under the strongly reducing condition exhibited by such combustion systems
as the fuel bed and the cyclone burner.
3.5.2   Fuel Bed Coal Combustion
        Combustion systems that operate with the bulk of the combustion
taking place in a thick bed of coal have characteristically low flue gas
particulate loadings.  Most of the ash is retained on the bed and discharged
into the ash pit.  Combustion takes place within much larger coal particles
and as such, a larger component of the burning is of a diffusion nature.
The bulk temperature of the fuel bed increases from the grate where the
combustion air is supplied to the top of the bed which receives radiant heat
from furnace as well as from exothermic reactions.  However, within the fuel
bed surrounding individual coal pirticles, the temperature is not well defined.
The coal particle itself will have a temperature gradient from the coal core
to a hot surface.  As the particle heats up, the coal devolatilizes and
thermally cracks.  The ash inclusions within the particle can conceivably
experience a temperature  stoichiometry history that is conducive to sulfur
retention.  Within these inclusions, the calcium could react with sulfur to
form the sulfide under the fuel rich condition.  Due to the nature of the
combustion,and the cooling effect of the combustion air, these ash packets may
never experience a temperature emission high enough to decompose the calcium
sulfide compound to SO .
        The stoichiometry in the fuel bed varies through the bed and around
the coal particles.  The sulfur retention will be lessened to the extent that
the variation from the optimum conditions are great.
                                       53

-------
        The fact that sulfur is retained in a fuel bed system, coupled with
the dependence on calcium content of the coal, point to a rather different
reaction mechanism than is found with sodium sulfur capture.  The specific
surface area of the coal/ash mixture in the fuel bed is many times less than
the surface area of the fly ash particles from a pulverized coal flame.  This
combined with the condition that most of the ash remains in the bed and is not
in intimate contact with the SO  in the flue gas indicates that the sulfur
migrates through the bed until contact with the metals occurs.
        In a well controlled laboratory fuel bed simulator, sulfur balances
have been made on the gaseous SO  emissions and the sulfur retained in the ash.
Table 3-9 contains the data for the solids analysis and gas analysis.  Under
the solids analysis three layers of the fuel bed were analyzed separately;
the top unburned coal, the middle partially burned coal, and the ash layer.
The ash was used as a tracer and the pounds of sulfur per pounds of ash are
shown for each layer.  Based on the top coal layer and the ash layer, the ash
retained 57% of the available sulfur.  Also shown in this table are the gaseous
measurements of SO  emitted during the test burn.  The theoretical maximum
SO  emission at 3% excess O  is 783 ppm.  The measured value of 364 ppm
represents a 54% retention.  This compares very well with the solids analysis.
This test was performed on a coal that had been ground, mixed with additional
lime and reformed into briquettes.  The lime addition brought the Ca/S molar
ratio up to 1.65 from the naturally occuring ratio of 0.60 in the coal.  This
information implies that only 35% of the available calcium in the fuel bed was
effective in retaining sulfur.
3.5.3   Cyclone Coal Combustor
        No test data are available on sulfur retention in cyclone furnaces.
However these systems represent what might be optimal conditions for large
retentions.  The cyclone is a relatively well mixed system in which most of
the ash remains in the combustor.  This mixing provides good contact of metals
and sulfur.  The slag layer temperatures are in the range of 2000 to 2500 °F
since this represents the range of fluid temperatures of most coal ashes under
reducing conditions.  The slag layer collects the larger raw incoming coal
particles which devolatilize and burn in the slag.  Smaller particles remain
                                      54

-------
        TABLE 3-9.  SULFUR BALANCES ON A LABORATORY FUEL BED SIMULATOR
Solids Analysis
Moisture , %
Ash, %
Sulfur, %
Gross Heat of
Combustion
Net Heat of
Combustion
Ib Sulfur/lb Ash
Top Coal - 8-9"
41.89
8.45
0.47
9796*
9366*
0.0556
Middle Coal 20.5-21.5"
2.12
18.78
0.74
10,200*
9923*
0.0394
Ash
0.12
96.68*
Dry Basis
3.06*
—
—
0.0317
(57% retention)
Ca/S (molar) =1.65
Gaseous Analysis
SO,, at 3% 0^, ppro
Theo. max.
Measured
Percent retention
       783
       364
        54
                                      55

-------
entrained in the gas stream where they burn.  Exit gas temperatures from the
cyclone are higher than 2500 °F, however the molten slag layer loses heat to
the water-cooled furnace walls and typically remains just hot enough to flow
out of the furnace.  The conditions of rapid mixing, temperatures below 2500 °F,
and containment of most of the ash would presumably favor a high degree of
sulfur retention.  The equilibrium calculation predict significant quantities
of liquid sodium sulfate at 2100 °F at 125% theoretical air.  The addition of
sodium fluxing compounds to a coal ash usually lowers the fluid temperature of
the slag.  Such action would be in the right direction for increased sulfur
retention by both calcium and sodium.
        Although it has not been the practice in the past, cyclone combustors
could be run at substoichiometric fuel to air ratios with secondary air addition
to complete burnout.  Such a system would be similar to the two stage low
NO  combustor developed at B&W  (Ref. 4).  However by running the cyclone first
stage fuel rich the ash fluid temperatures could be reduced to the 2000 °F
region.  Under reducing conditions at these temperatures calcium sulfide is
a favored product which would be removed with the slag.
        It would be desirable in order to control sulfur oxides emissions
to investigate the sulfur retention characteristics of cyclone combustors
and to change the process variables in order to optimize the retention of
sulfur in the slag.
                                      56

-------
                                 SECTION 4.0
                                 CONCLUSIONS

        The results of field tests, laboratory tests and equilibrium calcula-
tions show that sulfur can be retained in coal ash by reacting with the calcium,
sodium and potassium components of that ash under reducing as well as oxidizing
conditions.  Sodium sulfate is the only condensed phase sulfur compound that
occurs as a liquid.
        The field data generally indicated that increasing boiler load and
excess O_ results in increased sulfur retention.  This conclusion is supported
by the equilibrium calculation which showed increasing retention with increas-
ing excess O_ up to temperatures of 2100 °F.  At this temperature a minimum
sulfur retention was exhibited as the fuel/air mixture passed through the
stoichiometric condition.  The retention then increased as the mixture became
increasingly fuel rich.
        Although the results do not indicate the mechanism for the sulfur
retention they do point to the condition under which the retention could be
expected.  The three major modes of coal combustion, pulverized,  fuel bed
and cyclone combustion were analyzed in terms of the potential for sulfur
retention in each.  The assessment concluded that the new developing low
NO  technology for coal combustion also produces the conditions of stoichiometry
  2i
and temperature that are necessary for enhanced sulfur retention.
                                      57

-------
                                 REFERENCES
1.      Gronhovd, G. H., Tufte, P. H. and Selle, S.  J., "Some Studies on
        Stack Emissions from Lignite-Fired Power Plants," Presented at
        1973 Lignite Symposium, Grand Forks, ND, May 9-10, 1973.

2.      Gordon, S., and McBride, B. J., "Computer Program for Calculation of
        Complex Chemical Equilibrium Compositions, Rocket Performance,
        Incident and Reflected Shocks, and Chapman-Jouquet Detonations,"
        NASA SP-273, Interim Revision, March 1976.

3.      Shah, N. D., Teixeira, D. P. and Muzio, L. J.,  "Bench-Scale
        Evaluation of Dry Alkalis for Removing SO2 from Boiler Flue Gases,"
        Presented at Symposium on Transfer and Utilization of Particulate
        Control Technology, Denver, CO, July 24-28,  1978.

4.      Johnson, S. A., Cioffi, P. L., and McElroy,  M.  W., "Development of
        an Advanced Combustion System to Minimize NOX Emissions from Coal-
        Fired Boilers," 1978 Joint Power Conference, Dallas, Texas,
        September 11, 1978.
                                      58

-------
                                TECHNICAL REPORT DATA
                          fPleaie read Instructions on the reverie before completing)
1. REPORT NO. ,
EPA-600/7-78-153b
                                3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Sulfur Retention in Coal Ash
                                5. REPORT DATE
                                 November 1978
                                                       6. PERFORMING ORGANIZATION CODE
 . AUTHOR(S)
/. MW I nwni^l
K. L. Maloney, P.K. Engel, and S.S. Cherry
                                                       8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
KVB, Inc.
17332 Irvine Boulevard
Tustin, California  92680
                                10. PROGRAM ELEMENT NO.
                                EHE624A
                                11. CONTRACT/GRANT NO.
                                68-02-1863
12. SPONSORING AGENCY NAME AND ADDRESS
 EPA, Office of Research and Development
 Industrial Environmental Research Laboratory
 Research Triangle Park, NC  27711
                                13. TYPE OF REPORT AND PERIOD COVEMED
                                Final; 2/75 - 2/78	
                                14. SPONSORING AGENCY CODE
                                 EPA/600/13
15.SUPPLEMENTARY NOTES T£RL-RTP project officer is David G. Lachapelle, MD-65, 919/
541-2236.
i6. ABSTRACT Tne ygp^ gives results of an analytical study to assess the potential for
sulfur retention in various types of coal-fired boilers. Results of a field test of 10
industrial coal-fired boilers were used to evaluate the impact on sulfur retention of
the operating variables (load and excess O2).  The effect of ash composition on sulfur
retention was also evaluated,  using a linear regression analysis. The expression
% S Emitted = a+b (% Na2O/% CaO) + c  (Load/100,000), where a, b, and c are
constants, gave the best overall fit to the two pulverized coal-fired boiler data. The
field test and regression analysis results were supported by equilibrium coal ash
composition calculations over a range of temperatures and theoretical air for four
coal ash compositions.  The calculations show that significant fractions of the sulfur
can be tied up as Ca and Na salts under both reducing and oxidizing  conditions at
temperatures below 2500 F.  A minimum in the total condensed phase sulfur species
is predicted at stoichiometric conditions for all temperatures.
17.
                              KEY WORDS AND DOCUMENT ANALYSIS
                 DESCRIPTORS
                                           b.IDENTIFIERS/OPEN ENDED TERMS
                                            c.  COSATI Field/Group
Air PoUution
Coal
Combustion Products
Sulfur Oxides
Sulfur
Stokers
Ashes
Loading
Oxygen
Linear Regression
Air Pollution Control
Stationary Sources
Excess Oxygen
Alkaline Salts
Sulfur Balance
13B
2 ID
21B       12A
07B

13A
IS. DISTRIBUTION STATEMENT
 Unlimited
                    19. SECURITY CLASS (This Report)
                    Unclassified
                                                                    21. NO. Or PAGtS
                                                                        68
                    20. SECURITY CLASS (Thispage)
                    Unclassified
                                             22. PRICE
   Form 2220-1 (9-73)
                                          59

-------