EPA-450/3-77-050b
December 1977
    ENERGY REQUIREMENTS
          FOR CONTROLLING
               SO2 EMISSIONS
           FROM COAL-FIRED
            STEAM/ELECTRIC
               GENERATORS -
       EXECUTIVE SUMMARY
   U.S. ENVIRONMENTAL PROTECTION AGENCY
      Office of Air and Waste Management
    Office of Air Quality Planning and Standards
    Research Triangle Park, North Carolina 27711

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                               EPA-450/3-77-050b
      ENERGY REQUIREMENTS
FOR CONTROLLING SO2 EMISSIONS
          FROM COAL-FIRED
 STEAM/ELECTRIC GENERATORS -
        EXECUTIVE SUMMARY
                     by

                   W.C Thomas

                 Radian Corporation
                   P.O. Box 9948
                 Austin, Texas 78766
                Contract No. 68-02-2608
                   Project No. 8
              EPA Project Officer: K.R. Durkee
                   Prepared for

           ENVIRONMENTAL PROTECTION AGENCY
              Office of Air and Waste Management
           Office of Air Quality Planning and Standards
           Research Triangle Park, North Carolina 27711

                   December 1977

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This report is issued by the Environmental Protection Agency to report
technical data of interest to a limited number of readers.  Copies are
available free of charge to Federal employees,  current contractors and
grantees,  and nonprofit organizations - in limited quantities - from the
Library Services Office (MD-35) ,  Research Triangle Park,  North Carolina
27711;  or, for a fee, from the National Technical Information Service,
5285 Port Royal Road, Springfield, Virginia 22161.
This report was furnished to the Environmental Protection Agency by
Radian Corporation, P.O. Box 9948, Austin, Texas 78766, in fulfillment
of Contract No. 68-02-2608,  Project No.  8.  The contents of this report
are reproduced herein as received from Radian Corporation.  The opinions,
findings, and conclusions expressed are those of the author and not
necessarily those of the Environmental Protection Agency •  Mention of
company or product names is not to be considered as an endorsement
by the Environmental Protection Agency.
                   Publication No. EPA-450/3-77-050b
                                  11

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                       TABLE OF CONTENTS

                                                         Page

1. 0       BACKGROUND AND PURPOSE 	 1
2. 0       APPROACH 	 2
3.0       SUMMARY OF RESULTS 	 4
          3.1 Design Assumptions 	 4
          3.2 Comparison by S02 Control Methods 	 4
          3.3 Comparison by S02 Control Level 	11
          3.4 Energy Penalty Projections 	13
                               iii

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1.0       BACKGROUND AND PURPOSE

          The existing New Source Performance Standard (NSPS) for
S02 emissions from coal-fired steam generators is 0.52 g S02/MJ
(1.2 Ib S02/106 Btu) of heat input.  Depending on coal sulfur
content and heating value, compliance with this standard can be
achieved by means of flue gas desulfurization (FGD),  coal desul-
furization, the use of low sulfur coal, or a combination of these
approaches.  Since the promulgation of the S02 NSPS in 1971, im-
provements have been made in the performance and reliability of
FGD processes.  Because of these improvements, public interest
groups have requested that the EPA promulgate more stringent S02
emission standards.  Therefore, the EPA's Office of Air Quality
Planning and Standards (OAQPS) has undertaken a program to review
the existing NSPS.  The study described in this report was done
to assist OAQPS in the review by providing information on the en-
ergy requirements of S02 control systems.  The report answers the
following questions.

          What are the amounts and types of energy required to
operate various S02 emission control systems?

          How do these energy requirements compare to those of
steam generators without emission control systems?

          How do projected energy requirements for emission con-
trol compare with projected national energy demands in 1987 and
1997?

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2.0       APPROACH

          The study was based on an EPA model including 102 sys-
tems which are combinations of power plants and S02 control meth-
ods.  The variables considered in the model are level of S02 con-
trol, method of S02 control, power plant size, and coal composi-
tion.  The levels of each variable considered in this study and
the combinations of variables were defined by EPA as shown in
Table 1.  Three levels of S02 control were considered.  They in-
clude the existing NSPS (0.52 g S02/MJ heat input), 90 percent SO2
removal, and 0.22 g S02/MJ.  Control methods considered include
regenerable FGD processes, nonregenerable FGD processes, trans-
portation of low sulfur coal to the Midwest, and a combination
of coal cleaning and nonregenerable FGD processes.

          Energy requirements for the 102 model systems were cal-
culated by extrapolating "base case energy requirements.  Base
case energy requirements for each S02 control method were calcu-
lated from material and energy balances.  The base case was 90
percent S02 removal from the flue gas of a 500 MW power plant
burning 3.5 percent sulfur coal.  Extrapolation factors which de-
scribe energy requirements in terms of flue gas rate and S02 re-
moved were defined.  The extrapolation factors were used to cal-
culate energy requirements for all the power plant/S02 control
system combinations included in the model.
                                -2-

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                             TABLE  1.    MODEL S02  EMISSION  CONTROL  SYSTEMS STUDIED
                   SO2 Control Level
Plant Sizes Considered, Mf  FGD Processes Considered*
                                                                                                       Coal
           0.52 g SOj/KJ (1.2 Ib  S02/10' Btu)
    25, 100, 500,  1000
    25, 100, 500,  1000
    25, 500

    25, 500

    500
LS, L,  MgO. W-L/A,  D-A
LS, L
                                                                      LS, L
3.5Z sulfur; 27.9 MJ/kg
7.0Z sulfur; 27.9 MJ/kg
0.6Z sulfur; 20.9 MJ/kg western coal
transported to a Midwest power plant
0.8Z sulfur; 25.6 MJ/kg western coal
transported to a Midwest power plant
2.3Z sulfur; 29.2 MJ/kg**
 I
lo
 I
90Z S02 Reaoval by FGD



0.22 g S02/MJ (0.5 Ib S02/10( Btu)



25,
25,
25,
25,
25,
25.
25,
25,
100, 500, 1000
100, 500, 1000
100, 500
100, 500
500
500
500
500
LS,
LS,
LS,
LS,
LS,
LS,
LS,
LS,
L, MgO, W-L/A, D-A
L, MgO, W-L/A, D-A
L
L
L
L
L
L
3
7
0
0
0
0
2
4
.5Z
.01
.8Z
.8Z
.81
.81
.3Z
.61
sulfur;
sulfur;
sulfur;
sulfur;
sulfur,
sulfur;
sulfur;
sulfur;
27.
27.
20.
25.
20.
25.
29.
29.
9
9
9
6
9
6
2
2
MJ/kg
MJ/kg
MJ/kg
MJ/kg
MJ/kg
MJ/kg
MJ/kg**
MJ/kg***
                      *LS    - Linestone
                       L    - Line
                       MgO   - Magnesia Slurry
                       W-L/A - Wellnan-Lord/Allled
                       D-A   - Double-Alkali
                      **Physlcally cleaned 3.5Z sulfur;  27.9 MJ/kg coal  (40Z sulfur removal)
                     ***Physically cleaned 7.0Z sulfur;  27.9 MJ/kg coal  (40Z sulfur removal)

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3.0       SUMMARY OF RESULTS

          The results of the study show how energy requirements
depend on SOa control method, level of control, and coal sulfur
content.  It was found that energy requirements for S02 control
systems (expressed as energy required per unit of electrical
generating capacity) depend only slightly on plant size.

3.1       Design Assumptions

          The energy requirements for operating flue gas
desulfurization systems were calculated based on the process
designs summarized in Table 2.   The design assumptions for coal
cleaning processes are shown in Table 3.   A unit train con-
sisting of 100 coal cars and five locomotives was the design
basis for coal transportation.   Fuel consumption rates, transport
distance,  train speeds at full and reduced power, and coal dust
blow-off losses were specified.

          Table 4 shows calculated energy requirements for the
six processing operations in FGD systems.  Particulate/chloride
removal, reheaters, and fans account for 65 to 90 percent ot
total energy requirements for nonregenerable FGD processes.
Sulfur recovery operations account for the majority of energy
requirements for regenerable FGD processes.

3.2       Comparison by SOa Control Methods

          Figure 1 shows the energy required to meet the existing
NSPS of 0.52g S02/MJ using different S02  control methods for
several coal compositions.  The total energy requirements are

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                                  TABLE  2.   PROCESS  DESIGN  BASES  FOR  FGD  PROCESSES
 i
Ul
 i
FGD Process
Process Step Limestone
Particulate/Chlorlde Removal Venturi
SO 2 Scrubbing Mobile Bed
Reheat Indirect Stem
Re heater
Fans Induced Draft Fans
Sulfur Disposal/Recovery Lined Settling
Pond
Line
Venturi
Mobile Bed
Indirect Steaa
Reheater
Induced Draft Fan*
Lined Settling
Pond
MgO
Venturi
Venturi
Indirect Steaa
Reheater
Induced Draft Fans
Production of
Sulfuric Acid
Uellman- Lord/Allied
Venturi
Valve Tray
Indirect Steam
Reheater
Induced Draft Fans
Production of
Elemental Sulfur
Double-Alkali
Venturi
Mobile Bed
Indirect Steam
Reheater
Induced Draft Fans
Lined Settling
Pond
           •Selection of processing techniques was baaed on data from the open literature which were representative of
            commercially available systems.

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separated into the types of energy required, i.e., steam, fuel
oil, natural gas, electricity, and coal losses.  Nonregenerable
FGD processes impose the lowest energy requirements.  The combi-
nation of coal cleaning and nonregenerable FGD systems requires
three times the energy required by the FGD process alone.  Trans-
portation of low sulfur western coal to the Midwest requires
25 to 100 percent more energy than combusting a high sulfur
eastern coal and using a nonregenerable FGD process.

 TABLE 3.  DESIGN ASSUMPTIONS FOR PHYSICAL COAL CLEANING FACILITY
          40% sulfur removal
          95% energy recovery efficiency
          The electric power requirements for a
          278 kg/s (500 ton/hr) cleaning plant
          are 2980 kW.
          The heat duty of a thermal dryer is
          534 kJ/kg (230 Btu/lb) of coal dried.
          One half of the clean coal product (the coal
          fines) is thermally dried.
          Heat for the thermal dryers is supplied by
          burning a portion of the clean coal
          product.
          507o of the ash content of the coal is removed.
          The average heating value of the clean coal is
          29.2 MJ/kg (12,500 Btu/lb).
Figure 2 shows the energy required to meet a standard of 90%
S02 removal using different S02 control methods for several coal
compositions.  Figure 3 shows energy requirements for meeting a
standard of 0.22 g S02/MJ.  The energy requirements for different
                               -6-

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TABLE  4.    ENERGY  REQUIREMENTS FOR  THE PROCESSING  OPERATIONS  IN FGD  SYSTEMS
Energy Requirements for Flue Gas Desulfurization, MJ/s
FGD Process
Limestone

Lime

Magnesia Slurry

Wellman-Lord/Allled

Double- Alkali

Coal Sulfur
Content
3. 51
7. 01
3. 5*
7.0Z
3.5Z
7. OX
3. 51
7.0Z
3.5Z
7.0*
Raw Material
Handling and
Preparation
2.2
4.4
0.2
0.4
0.5
0.9
0.2
0.3
0.3
0.5
Partlculate/
Chloride
Removal
9.0*
9.0*
9.0*
9.0*
3.0
3.0
3.0
3.1
3.0
3.0
S02
Scrubbing
6.8
13.5
6.3
9.4
2.5
5.0
0.9
0.9
2.4
2.4
Reheat
18.3
18.5
18.3
18.3
15.3
IS. 4
16.8
17.3
18.2
18.2
Fans
10.4*
11.1*
10.2*
10.4*
14.7
16.1
18.3
18.8
14.9
14.9
Sulfur
Recovery/
Disposal
0.3
0.6
0.3
0.5
41.1
82.8
136
281
0.7
1.3
Total System
Energy
Requirements**
49.2
57.3
44.3
48.2
77.5
124
176
321
39.8
40.7
 *Energy required by fans to overcome pressure drop associated with partlculate removal  Is included In the particulate removal operation.
"Utilities and Services for the FGD processes account for the discrepancies In system totals.
Assumptions

500 MW power plant (net generating  capacity)
901 SO: removal
Uncontrolled power  plant net heat rate - 2640 J/kW-s
                                       -
Uncontrolled power plant net heat rate - 2640 J/kW-s
Steam produced in Magnesia Slurry and Wellman-Lord/Allled process is used within the process.
Magnesia Slurry process produces sulfurlc acid as a by-product.
Wellman-Lord/Allied process produces sulfur as a by-product.

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                                  I OIL ON «AS

                                  I COAL CLIANINO ANO TNAIN WIMOAM 1.OSHS

                                  I STIAM AND ILICTNICITV

                                  ) OIIStL FUIL OIL
                                             O.ttlULFUN.
                                             20.IMJIX
                                              COAL
0.§» SULFUH.
tf.t MJ/k«
 COAL
Figure 1.   Energy requirements  for  S02  and particulate  control
             0.52g S02/MJ  control level,  500 MW plant.
                                     -8-

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                                             LtQCNO:


                                           | OIL OR «Ai


                                           I ITIAM AW ILICTMCITV
                                         O
                                         i!
                3.5% SULFUR
               ar.auj/kg COAL
 7* SULFUR     O.t* SULFUR  O.t* SULFUR
I7.9MJ/k| COAL   t0.tMJ/kv COAL tl.VMJ/hf COAL
Figure 2.   Energy penalties  for S02  and particulate control
             907o  S02 removal control  level,  500 MW plant.
                               -9-

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                                  *.•% SULFU
                                  tT.t UJ/h
                                   COAL
T.0« SULFUR.
 >?.«MJ/kt
  COAL
Figure 3.   Energy requirements for S02 and particulate
            control - 0.22  g/S02/MJ control level, 500 MW
            plant.
                           -10-

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control methods have  the  same relative variations for the more
stringent standards as  those for meeting the existing standard.
Table 5 summarizes the  energy requirements shown in Figures  1
through 3 for  combusting  a 3.5 percent sulfur coal.
          TABLE 5.  ENERGY PENALTIES ASSOCIATED WITH DIFFERENT
                   METHODS OF CONTROLLING S02 EMISSIONS - 500 MW
                   PLANT, 3.5% SULFUR COAL
S02 Control
Process
Nonregenerable FGD
Limestone
Lime
Double- Alkali
Regenerable FGD
Magnesia Slurry
Wellman-Lord/Allied
Coal Cleaning Plus
Lime/Limestone FGD
Energy Penalty (% Energy Input To
Equivalent Uncontrolled Power Plant)
Level
0.52g S02/MJ
(NSPS)

3.4
3.0
3.0

5.3
11.7
9.8
of SOz Control
90%
Removal 0

3.8
3.4
3.0

6.1
13.2
NE

.22g S02/MJ

NE
NE
NE

NE
NE
9.8/10.2
 NE = Not Examined

3.3       Comparison by SO; Control Level

          Figure  4 shows how energy penalties depend on  the  level
of S02 control.   Two levels of control are shown, the existing
standard and  90 percent SO2 removal.  Ninety percent removal  is
a more stringent  level of control than the existing standard.
Figure 4 shows that for most control methods the energy  penalty
for achieving 90  percent removal is about 10-15 percent  higher
than that required to meet the existing NSPS.
                               -11-

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 09
 I
cd
c
0)
PH
bO
fc
0)
360 -


340 -


320-


300-


280 -


260 .

    *
    !
180 -


160-


140-


120 -


100-


 80-
             Physical Coal Cleaning and
             Limestone or Lime FGD
                         ©
            Transporting Low Sulfur Western
            Coal to Midwest-No FGD
                                               Basis:
500 MW plant;
2640 J/kW-s  net heat rate;
3.5Z sulfur,
27.9 MJ/kg coal
                               Double-Alkali FGD
                  0.52 g S02/MJ
                       (NSPS)
                                          90% SO2
                                          Removal
                     Level of Control  of SO: Emissions

           Figure 4.   Energy penalties  for S02  control
                       of effects of S02 control level.
                                                        -  summary
                                    -12-

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          The results of the study also show that for combustion
of low sulfur western coal, 90 percent S02 removal requires up to
10 percent more energy than controlling emissions to 0.22 g S02/MJ
(0.5 Ib S02/106 Btu) of heat input.  For low sulfur coals, 0.22 g
S02/MJ is more stringent than the existing NSPS but less stringent
than 90 percent removal.

          For a "bare bones" S02 control system, the energy re-
quired for flue gas reheat and particulate/chloride removal is
excluded from the limestone and lime systems.  This reduces the
energy requirements of these systems by 50 to 60 percent.  For
the double-alkali, magnesia slurry and Wellman-Lord/Allied pro-
cesses, the particulate/chloride removal operation is required
to prevent buildup of chlorides in the S02 scrubbing liquor.
However, excluding flue gas reheat requirements would reduce the
energy required by the MgO system by 15 to 25 percent, the W-L/A
by about 10 percent and the double-alkali by about 50 percent.

3.4       Energy Penalty Projections

          The energy penalties associated with S02 controls were
compared with projected total U.S. energy consumption for 1987
          /
and 1997.   Depending on control level, method of control, and
sulfur content of coal,  the energy required to control S02 emis-
sions from new coal-fired power plants installed in 1983 through
1987 will be from 0.1 to 0.4 percent of total energy consumption
in 1987.  For the new capacity installed in 1983 through 1997, the
energy penalty ranges from 0.4 to 1.7 percent of projected U.S.
energy consumption in 1997.  These ranges are based on combusting
0.8 to 3.5 percent sulfur coal and controlling S02 emission to
the existing NSPS or effecting 90 percent S02 removal.  Assuming
the majority of future S02 controls are limestone or lime FGD
systems, as is presently true, estimates for 1987 and 1997 would
be 0.1 percent and 0.4 percent, respectively.
                              -13-

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                                TECHNICAL REPORT DATA
                         (Please read Instructions on the reverse before completing)
1. REPORT NO.

  EPA-450/3-77-0506b
                                                     3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
 The Energy Requirements for Controlling S02 Emissions
 from Coal-Fired  Steam/Electric Generators
            5. REPORT DATE
             January, 1978
            6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)

 W. C. Thomas
                                                     8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
                                                      10. PROGRAM ELEMENT NO.
 Radian Corporation
 P. 0. Box 9948
 Austin, Texas  78766
            11. CONTRACT/GRANT NO.
              68-02-2608
12. SPONSORING AGENCY NAME AND ADDRESS
 Environmental Protection Agency
 Office of Air Quality Planning and Standards (MD-13)
 Research Triangle Park, North Carolina  27711
            13. TYPE OF REPORT AND PERIOD COVERED
              Final
            14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
       The  report  is an  executive  summary  of the main report  (EPA-450/3-
  77-050a).   The main report is  an analysis of the energy required by
  various methods  of reducing sulfur dioxide emissions  from coal-fired
  boilers.   The energy required  for limestone, lime, double alkali, mag-
  nesium slurry and Wellman-Lord/Allied  flue gas  scrubbing systems is
  presented.   The  variation of energy requirements with coal  sulfur
  content,  emission level achieved and plant size  is presented.   The
  energy required  to transport low sulfur  coal to  the mid-west  or to
  physically clean sulfur from the coal  is presented also.
17.
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b.lDENTIFIERS/OPEN ENDED TERMS  C. COSATI Field/Group
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                                          Unclassified
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 Unclassified
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EPA Form 2220-1 (9-73)
                                        -14-

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