United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S8-85/006 Sept. 1985
Project Summary
Shawnee Flue Gas
Desulfurization Computer
Model Users Manual
F. A. Sudhoff and R. L Torstrick
The Shawnee lime/limestone com-
puter model was developed by Bechtel
National, Inc. and the Tennessee Valley
Authority (TVA) to model lime/lime-
stone wet-scrubbing flue gas desurfur-
ization (FGD) systems and is capable of
projecting comparative investment and
revenue requirements for these sys-
tems. The computer model has been
developed to permit the rapid estima-
tion of relative economics of these sys-
tems for variations in process design
alternatives (i.e., limestone versus lime
scrubbing, alternative scrubber types,
or alternative sludge disposal meth-
ods), variations in the values of inde-
pendent design parameters (i.e., scrub-
ber gas velocity, liquid-to-gas ratio,
alkali stoichiometry, slurry residence
time, reheat temperature, and specific
sludge disposal design), and the use of
additives (MgO or adipic acid). Al-
though the model is not intended to
compute the economics of an individ-
ual system to a high degree of accuracy,
it is based on sufficient detail to allow
the quick projection of preliminary con-
ceptual design and costs for various
lime/limestone variations on a common
design and costs basis.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Triangle
Park, NC to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering in-
formation at back).
Program Development
The technical development of the
Shawnee lime/limestone computer
model is based on actual data obtained
at the Shawnee test facility. Bechtel and
TVA shared the responsibility of model
development. Bechtel was responsible
for analyzing the test results and devel-
oping the models which calculate the
overall material balance flow rates and
stream compositions. Bechtel provided
these models to TVA. TVA was respon-
sible for determining the size limitations
of the required equipment to establish
the minimum number of parallel equip-
ment trains, accumulating cost data for
the major equipment items, and devel-
oping models for projecting equipment
and field material costs as a function of
equipment capacity. Utilizing these rela-
tionships, TVA developed models to
project the overall investment cost
breakdown and procedure for using the
output of the material balance and in-
vestment models as inputs to a previ-
ously developed TVA model for project-
ing annual and lifetime revenue
requirements.
The model has been periodically up-
dated to include new or improved data
and process developments in FGD. The
basic processes in the current model
consist of limestone and lime scrub-
bing; spray tower, turbulent contact ab-
sorber (TCA), and venturi-spray tower
absorbers; and pond or landfill diposal.
Process options include three alterna-
tive modes of forced oxidation and pro-
visions for MgO or adipic acid addition.
Several dozen additional input and out-
put options provide further flexibility in
the use of the model.
The specific mathematical treatment
of material balances, including S02 re-
moval efficiencies, are not fully docu-
mented in published works. Descrip-
tions of the mathematical treatment of
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S02 removal in spray tower and TCA are
given in Shawnee test facility reports.
The absorption of S02 into scrubbing
liquid approximates the mass transfer
situation of absorption followed by a
chemical reaction, a circumstance for
which no comprehensive theoretical
basis exists. Such treatment requires
mathematical expressions of turbulent
fluid behavior and reaction orders that
cannot be rigorously defined. Overall
mass transfer models are usually based
on modifications of general theoretical
treatments that differ in concept but
mathematically approach similar con-
clusions in some cases. Standard refer-
ences and texts provide discussions
and access to the literature.
In practice, the mass transfer func-
tions are reduced by a number of sim-
plifying assumptions based on a knowl-
edge of the system and the likely or
probable important and unimportant
factors. The mathematic expression at
once becomes manageable and specific
to the situation, to which it can be fur-
ther correlated empirically. The devel-
opment of such expressions is dis-
cussed in detail in published literature
for specific FGD applications.
The Shawnee model expression is
simplified by the assumptions that
liquid-side resistance controls the ab-
sorption rate and that liquid-phase reac-
tions are not limiting (that is, dissolved
S02 does not significantly affect the ab-
sorption rate). Both of these assump-
tions are supported by experimental
results:
SO2 = 1 - exp [-<)> K£az/Hv]
The simplified expression for the frac-
tion of S02 removed contains an en-
hancement factor, <|>, to represent the
effects of chemical reaction and a group
(consisting of a liquid-side mass trans-
fer coefficient, K°; interfacial area, a;
vertical distance, z; Henry's law con-
stant, H; and gas velocity, v) to repre-
sent physical absorption. The enhance-
ment factor contains expressions for
pH, effective magnesium, flue gas, SO2
content, and (in some cases) chloride
concentration. The expression is fitted
to Shawnee test facility data for each
particular absorber and absorbent com-
bination using eight coefficients. The fit-
ted expressions have standard errors of
estimate of about 4%. Pressure drop ex-
pressions for the three absorbers were
developed by fitting expressions con-
taining pertinent variables to Shawnee
test facility data. The development of
these expressions is discussed in
Shawnee test facility reports and sym-
posium proceedings.
Model Capability
The Shawnee lime/limestone scrub-
bing model is capable of projecting a
complete conceptual design package
for these systems utilizing a spray
tower, TCA, or venturi/spray-tower ab-
sorber, each with or without use of addi-
tives; and with any of five sludge dis-
posal options, including options with
and without forced oxidation. Ranges
for basic design parameters include:
Plant size
Coal sulfur
Scrubber gas
velocity
Liquor recirculation
rate
Slurry residence
time
Scrubber slurry
solids
Reheat (steam)
100-1,300 MW
2-5% (1,500-
4,000 ppm
S02)
8-12.5 ft/sec*
25-120 gal/aft3
(at scrubber
outlet)
2-25 min
5-15%
225°F maximum
reheat
temperature
Results for conditions outside these de-
sign ranges are not necessarily invalid
but are subject to potential reduced
accuracies.
The output of the model includes pro-
jections of annual and lifetime revenue
requirements to allow comparison of
the economics of the alternative system
designs. The basis for these projections
is described in the manual appendices.
The process technology is divided
into seven major areas to facilitate pro-
jection of the process design and the
estimated capital investment. The facili-
ties included in each area are identified
in the process description along with
the basis for design of the FGD system.
Process Description
Processing Areas
The seven major processing areas
used to define the limestone- and lime-
scrubbing systems are identified below
along with a description of the facilities
*1 ft = 30.48 cm; 1 gal. = 3.785 L; 1 ft3 = 28.32 L;
and °C = 5/9 (°F-32).
included within the battery limits of
each processing area, and the basis for
design of these facilities.
Raw Material Handling
This area provides for receiving either
limestone or lime. For the limestone
slurry process, the raw-material-
handling area includes equipment for
receiving limestone by truck or rail, a
storage stockpile, and live inprocess
limestone storage equipment.
For the lime slurry process, the raw-
material-handling area includes equip-
ment for receiving lime by truck or rail
and a storage silo.
The direct investment costs of the raw
material-handling area include costs for
all of the lime/limestone receiving
equipment and field construction mate-
rials up to and including the raw mate-
rial feed bin.
Raw Material Preparation
This area provides for preparation of
a limestone or lime slurry for feed to the
S02 scrubbing area. The raw material
preparation area for the limestone
slurry process includes gyratory crush-
ers for crushing the limestone for feed
to the wet ball mills. The wet ball mills
grind the limestone to the desired size
for feed to the scrubbers. The product
slurry from the mills at a concentration
of 60% solids is pumped to a slurry feed
tank adjacent to the scrubbing area for
distribution to the scrubbers.
The raw material preparation area for
the lime slurry process includes equip-
ment for slaking the lime at a concentra-
tion of 20-25% solids for feed to the
scrubbers. The product slurry from each
of the slakers overflows to a slurry re-
ceiving tank from which it is pumped tc
a common slurry feed tank. The slurry is
then pumped to the scrubbing area foi
distribution to the scrubbers.
The direct investment costs for th«
feed preparation area include all prepa
ration equipment and field constructior
materials from the raw material bir
weight feeder to the slurry feed tanks.
Gas Handling
Flue gas from the power unit ducts is
fed to a common plenum from whicl
any number of scrubber trains can b<
fed. To minimize the problems associ
ated with gas distribution for such a sys
tem, separate fans are included on eacl
side of the plenum. The power plan
fans are conventional induced-draft (ID
fans for balanced-draft boilers. Tlr
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scrubber fans can be specified as
forced-draft (FD) or ID and are designed
to overcome the pressure drop of the
pollution control facilities.
The direct investment costs for the
gas-handling area include costs for the
flue gas equipment and field materials
downstream of the air heater up to, but
excluding, the stack plenum. Costs for
the scrubber fans are included; how-
ever, costs for the power plant fan, the
stack plenum, and the stack are consid-
ered to be an integral part of the power
plant and are, therefore, not included in
the estimate.
SO2 Scrubbing
Flue gas is contacted with a lime or
limestone slurry in either a spray tower,
TCA, or venturi/spray tower. The ab-
sorbers are equipped with a chevron-
vane mist elimination system designed
for upstream and downstream wash
with fresh makeup water. Makeup lime
or limestone slurry from the slurry feed
tank and recycled supernate of filtrate
from the waste disposal area are fed to
the absorber hold tanks where they are
blended with the slurry draining from
the absorber. The slurry recirculation
loop can be designed for use of either
one or two hold tanks below the ab-
sorber. For the two-tank option, if forced
oxidation is specified, air is injected into
the tank which receives the effluent
from the scrubber. Scrubber slurry is
bled from this tank for disposal. Over-
flow from this tank flows by gravity to
the second tank where fresh limestone
slurry is added. The combined slurry is
then recirculated to the absorber and ei-
ther the presaturator or venturi, de-
pending on the process. The bleed-
stream is pumped to the waste disposal
area where the sludge is dewatered.
The supernate or filtrate is returned to
the scrubbing and raw material prepa-
ration areas. The S02 scrubbing area
can be designed without the use of ad-
ditives or with the use of either MgO or
adipic acid to enhance S02 removal.
The SO2 removal model can be run
with any of the following four options
for relating stoichiometry, L/G ratio in
the absorber, and SO2 removal
efficiency:
Input
Direct investment costs for the S02
absorption area include all slurry and
S02 absorption equipment and field
construction materials between the
slurry feed tank and the waste disposal
feed tank. Costs for a mechanical collec-
tor may be included optionally.
Oxidation
This area is optional, providing for ox-
idation of the SOZ absorbed as calcium
sulfite to calcium sulfate to facilitate
subsequent dewatering and disposal of
the FGD wastes. If the forced-oxidation
option is not specified, the model re-
sults are based on only natural oxida-
tion occurring in the scrubbing loop
with about 5-20% of the absorbed S02
being in the oxidized (calcium sulfate)
form. Two forced-oxidation alternatives
are available: (1) within-loop forced oxi-
dation in which air is sparged into the
absorber hold tank and scrubber slurry
is recirculated to the absorber, and
(2) bleedstream forced oxidation in
which a bleedstream from the absorber
is sparged with air in a separate tank
with the bleedstream subsequently pro-
cessed for disposal. In both oxidation
alternatives, equipment—primarily
compressors and air spargers for option
(1) and compressors, air spargers,
tanks, agitators, and pumps for option
(2)—is provided.
Direct investment costs for the oxida-
tion area, when selected, include costs
for the equipment and associated field
construction materials.
Reheat
The outlet gas from the scrubber is
reheated to the desired temperature by
(1) indirect steam reheat, (2) blending
scrubber outlet gas with hot flue gas
which bypasses the scrubber (only
available if overall S02 removal effi-
ciency is less than 90%), or (3) a combi-
nation of (1) or (2). The reheater gas is
discharged to the stack plenum.
Direct investment costs for the reheat
area include costs for the reheater
equipment and field construction mate-
rials for installation.
Calculate
1
2
3
4
Stoichiometry, L/G
Stoichiometry, S02 removal
L/G, SO2 removal
Stoichiometry, L/G, and S02 removal
S02 removal
L/G
Stoichiometry
Force-through alternative,
no calculation
Waste Disposal
The model has provisions for the fol-
lowing five alternate waste disposal op-
tions:
1. Onsite pond
a. Unlined pond
b. Clay-lined pond (cost and depth
of clay lining is input)
c. Synthetic-lined pond (cost of
liner is input)
2. Thickener - pond
3. Thickener - fixation fee
4. Thickener - filter - fixation fee
5. Thickener - filter - landfill
The onsite ponding options may also
be run with fixation fees applied to
them. For options (3) and (4), the fixa-
tion fee must include costs for trans-
portation and disposal of the fixed
sludge offsite. For options (1) and (2),
however, only the costs for fixation
need to be provided since the fixed
sludge can be disposed of at the exist-
ing pond site. For option (5), a landfill-
fixation option may be provided using
model calculations. Using this option,
the disposal facility is appropriately
sized for the additional fixation volume
requirements.
For the waste disposal alternatives,
the model allows for the onsite facility
to be sized larger or smaller than the
normal projected lifetime capacity. This
option has been incorporated (1) to ac-
count for variations in the sulfur content
of fuel, (2) to evaluate design philoso-
phy in construction of ponds or landfills
for less than the total amount of sludge
to be disposed (this requires assess-
ment of additional costs for enlarging
the waste disposal area later), or (3) to
allow the feed preparation and scrub-
bing area to be sized based on maxi-
mum sulfur contents expected while
sizing the waste disposal area based on
average sulfur contents.
Direct investment costs for the waste
disposal area include costs for the
equipment and field construction mate-
rials downstream of the waste disposal
feed tank including those associated
with the supernate return pumps and
piping.
Process Equipment Design
Basis
Based on results from the material
balance model and some user-supplied
variables, major process equipment is
specified by area. The equations for pre-
dicting equipment cost were updated in
1983. The design assumptions used as a
basis for projecting the size or specifica-
-------
tions of the major process equipment
are given below for each major equip-
ment item included in the alternative
FGD options.
Gyratory Crushers
Two parallel 50% capacity gyratory
crushers are used to reduce the inlet
stone size from minus 1-1/2 in. to minus
3/4-in. for feed to the ball mills.
Ball Mills
The grinding mills are rubber-lined,
open-circuit, overflow wet ball mills that
have a 30% ball charge and produce a
60% slurry. The number of ball mills is
determined by total mill horsepower
calculated from the limestone through-
put rate specified in the material bal-
ance, and the fineness of grind and
limestone hardness factors which are
program inputs. The fineness of grind
index factor is related to the desired par-
ticle size distribution of the ground lime-
stone. One-mill systems are used for
horsepower less than 200* and two par-
allel mill systems for horsepower be-
tween 200 and 5,000. For horsepower
greater than 5,000, the number of paral-
lel mill systems is determined assuming
a maximum mill size of 2,500 horse-
power.
Lime Storage Silo
A 30-day dead storage capacity is
used to calculate the volume of the lime
storage silos. The silos are concrete,
with the height of the actual storage
section of the silo assumed to be one
and a half ttmes the diameter. Total
height of the silo is equal to the height
of the actual storage section plus the
height of the carbon steel hopper plus
5ft. Parallel storage silos are used for
storage volumes greater than the ca-
pacity of the largest silo (147,200 ft3).
Lime Slaker
Lime is slaked at slurry concentra-
tions of 20-25% solids in dual-
compartment, overflow slakers which
can be designed with slaking capacities
of up to 33 ton/day. Parallel slaking
trains are used for larger lime capac-
ities. The number and size of parallel
slakers required are determined based
on the capacity of the largest slaker
available (33 ton/day).
Fans
The fans are centrifugal (double
width, double inlet) with radial im-
pellers. The FD fans are constructed of
carbon steel and the ID fans are con-
structed of Inconel 625. They are
equipped with variable-speed fluid
drives. Fan horsepower is calculated
based on the inlet gas flow rate per train
and the calculated pressure drop for the
scrubber, mist eliminator, reheater, and
duct.
Scrubbing Trains
The following procedures are used to
determine the size or specifications of
the major process equipment in the
scrubbing area. The number of parallel
scrubbing trains is either an input to the
program or is established as an override
to the input value based on the mini-
mum number of scrubber trains re-
quired. The minimum number of trains
is calculated considering the saturated
flue gas velocity and volumetric flow
rate at the scrubber outlet in conjunc-
tion with the maximum cross-sectional
area assumed for the scrubber (1,370
ft2).* Flue gas and slurry recirculation
rates per train are calculated by dividing
the total flow rates from the overall ma-
terial balance model by the number of
operating scrubbing trains.
Scrubbers
Scrubber cross-sectional area is cal-
culated considering the outlet flue gas
rate per train in conjunction with the
specified scrubber design gas velocity.
The number of scrubber grids and beds,
and the height of spheres per bed are
inputs to the program. The height of the
scrubber is assumed to remain constant
for all scrubber sizes and internal con-
figurations. A presaturator compart-
ment is included at the scrubber inlet for
the TCA and spray tower, and chevron-
type mist eliminators are included near
the outlet. Materials of construction for
the scrubbers and internals include:
Venturi: Carbon steel with acid-
resistance lining.
Shell: Rubber-lined carbon steel.
Grids: Type 316L stainless steel.
Spheres: 1-1/2 in.-diameter, nitrite
foam.
Mist eliminator, slurry header, and
nozzles: Type 316L stainless steel.
Tanks
The size or specifications of tanks, ag-
itators, and pumps for each area are de-
termined by utilizing the following pro-
cedures. Tank volume is calculated
based on the residence time, which is
*1 HP = 9809.5 W; 1T = 907.2 kg.
*1 ft* = 0.0929 m2.
either a program input or assumed. An
additional 10% volume is added foi
freeboard. All tanks are constructed o1
carbon steel, and the slurry tanks are
flake-glass lined. Except for the ab-
sorber bleed receiving tanks and the
thickener overflow tanks, the diametei
of each tank equals its height up to s
maximum height of 60 ft. For tank di-
ameters larger than 60 ft, tank height is
fixed at 60 ft and diameter is calculated,
Absorber bleed receiving tank height is
equal to the effluent hold tank heighi
and the diameter is calculated. Thick-
ener overflow tank height is set equal tc
the height of the thickener and the di
ameter is calculated. As on override tc
the calculated diameter, a minimum di
ameter equal to half the height is fixec
for all tanks. The thickener and filtei
feed tanks are not used unless more
than one thickener or filter is required.
Agitators
All slurry tanks are equipped with t
four-blade, pitched-blade, turbine agita
tor. Agitator horsepower requirement!
are calculated on the basis of tota
torque, which is a function of the degree
of agitation required (expressed a;
torque/unit volume), total tank volume
tank diameter, and the slurry specifii
gravity. Unit torque (torque/unit vol
ume) for each tank is determined as <
function of the percent solids in thi
slurry.
Slurry Pumps
All slurry pumps are rubber lined
centrifugal with water seals, and an
equipped with either a variable- or con
stant-speed drive. Pumps are usualh
spared, with the number of operatinj
pumps determined by the maximun
available pump size of 20,000 gpm.
Water Pumps
Vertical, multiple-stage, turbini
makeup water pumps capable o
providing a static head of 200 ft are pro
vided for each 10,000 gpm of water re
quired. The pumps are carbon stee
spared.
Compressors
The compressors are sized to providt
sufficient air (oxygen) for oxidizing th<
CaSC>3 • 1/2 H20 to CaS04 • 2 H20. Th<
stoichiometric quantity of S02 absorbec
is multipled by an input stoichiometry
usually 2.5, to determine the stoichio
metric quantity of oxygen to be added
The quantity of air is then determinec
for sizing the compressors.
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Reheaters
Reheater cross-sectional area is cal-
culated based on the superficial gas ve-
locity (usually 20 to 25 ft/sec) which is
input to the program and the volumetric
gas flow rate per train at scrubber outlet
conditions. Reheater surface area re-
quirements are calculated in two steps:
(1) surface area requirements for reheat
to 150°F, and (2) requirements for reheat
to the specified reheat temperature. The
portion of the reheater tubes required to
reheat to 150°F are Inconel and the re-
maining tubes are Cor-Ten. Reheater
design and costs are based on use of
1-in.* tubes on a 2-in. square pitch.
Thickeners
The thickeners are constructed of car-
bon steel tank walls coated with epoxy
paint and 1 ft thick concrete conical
basins. Thickeners are equipped with
rake mechanisms. A concrete under-
flow tunnel, including pumps and
piping for transferring the slurry, is in-
cluded. Total thickener cross-sectional
area is calculated by the material bal-
ance portion of the model as a function
of the settling rate and settled solids
density, which are inputs into the pro-
gram, and the quantity of sludge in the
effluent slurry calculated in the material
balance model. The number of thicken-
ers required is determined assuming a
maximum thickener diameter of 400 ft.
Thickener height is calculated as a func-
tion of the diameter.
Filters
Rotary drum vacuum filters con-
structed of carbon steel and equipped
with a vacuum pump, a filtrate pump,
and a vacuum receiver are utilized. Filter
size is determined as a function of the
filtration rate expressed in tons of dry
solids/ft2 day, which is a program input,
in conjunction with the total quantity of
sludge. The minimum and maximum
sizes of filters considered have effective
filtration areas of 50 and 900 ft2, respec-
tively. Single filters are used up to re-
quired filtration areas of 100 ft2. For total
filtration areas between 100 and
1,800ft2, two parallel filters are as-
sumed. For total filtration areas greater
than 1,800 ft2, the number and size of
parallel filters required are determined
based on the capacity of the largest fil-
ter size.
*1 in. = 2.54 cm.
Field Construction Materials
Design Basis
Costs for field construction materials
are based on the materials of construc-
tion or specifications discussed below.
Piping
Carbon steel pipe and gate valves are
used for all waterlines including pond
supernate. For slurry lines less than
3-in.-diameter, stainless steel pipe is
used; whereas, for all larger size lines,
rubber-lined carbon steel piping is
used. Stainless steel strainers are used
for pipes less than 4-in. diameter and
rubber-lined strainers are used for 4-in.-
diameter and larger pipes. For slurry
lines less than 3-in. diameter, stainless
steel plug valves are used. Eccentric
plug valves are used for slurry lines be-
tween 3- and 20-in. diameter, and knife
gate valves are used for valves greater
than 20-in. diameter. Handwheel opera-
tors are used for valves less than 12-in.
diameter and air cylinder actuators for
larger valves. Typical piping layouts are
correlated to flow rates in gal./min. Con-
trol valve costs are included in instru-
mentation. Costs are included for a
rubber-lined downcomer from the
scrubber to the effluent hold tank and a
spare slurry disposal line to the disposal
site.
Ductwork
Costs are included for the inlet
plenum and all ductwork between the
inlet and stack plenums including insu-
lation. Costs for the stack plenum are
not included since this plenum is re-
quired even if an FGD system is not in-
stalled. Stack plenum elevation is set
equal to effluent hold tank height with a
minimum elevation of 20 ft for small
hold tanks. Each scrubber train includes
two guillotine dampers and costs for ex-
pansion joints.
Two partial scrubbing or emergency
bypass ducts, each designed for a mini-
mum of 25% of the total gas flow rate
from the boiler, are included in the
costs. Each duct includes two louver-
type dampers and costs for expansion
joints.
Materials of construction for all duct-
work is 3/16-in. Cor-Ten with the excep-
tion of ductwork between the scrubber
and reheater outlet which is 3/16-in.
type 316 stainless steel. All ductwork is
insulated with 2-in. rock woof. Duct size
is based on a square cross section and a
nominal design velocity of 3,000 ft/min
at local inlet conditions.
Foundations
Concrete foundations for each equip-
ment item are fixed according to equip-
ment sizes. Foundations for the struc-
ture are estimated on the basis of the
weight of the structure.
Structures
Structural estimates are based on the
structure arrangement shown in the
body of the report. The total quantity of
structure required for each scrubber
train and the corresponding costs are
related to effluent hold tank volume,
scrubber cross-sectional area, and num-
ber of scrubbing trains.
Electrical
The electrical estimate is divided into
four sections: (1) costs of feeder cables
from the power plant transformer yard
to field modules for each area; (2) trans-
former costs for each area; (3) costs of
power supply from area field modules
to individual motors; and (4) motor con-
trol costs between remote control cen-
ter, field module location, and individ-
ual motors for each area. For each area,
total connected motor horsepower is
calculated for use in establishing costs
for (1) and (2). Costs for (3) and (4) are
based on individual motor sizes and
number of connected motors. A typical
layout is assumed for each area in refer-
ence to the power plant transformer
yard, remote control center, and other
areas.
Instrumentation
Instrumentation costs are based on
(1) fixed costs for instruments which do
not change in size and cost with equip-
ment and pipe size variations, and
(2) variable costs for instruments which
increase in size and cost as equipment
and pipe sizes increase. Each cost may
depend on the number of scrubbing
trains, ball mills, and pumps, etc. Costs
are included for control valves, graphic
boards and panelboards, annunciator,
air dryers and piping, and instrument
cable and wiring systems.
Buildings
The control room and motor control
center are integrated with the power
plant, and prorated costs are included.
Costs are included for a building to
house the limestone-grinding or lime
slaking facilities. Buildings to house the
oxidation and/or disposal area equip-
ment are included. All buildings
are sized as a function of the equipment
size and number of equipment items
-------
and are constructed with concrete
floors and corrugated aluminum siding,
supported by a steel frame. They are
insulated to a value of R-19 using fiber-
glass insulation.
Pond Construction
Disposal pond size is calculated
based on a square configuration with a
diverter dike three-fourths the length of
one side. The pond model is based on
unlined, clay-lined, or synthetic-lined
design and includes the following op-
tions in running the program.
Fixed-depth pond.
Optimum-depth pond based on mini-
mum pond investment.
Optimum-depth pond based on mini-
mum pond investment with available
acreage and maximum excavation
depth as overriding constraints.
In addition to specifying pond design,
the model also itemizes the breakdown
of projected pond costs.
Landfill Construction
Disposal landfill size is calculated
based on a square configuration with
the cap sloping up to a point.
A separate model is included to de-
sign and cost the onsite landfill. The
landfill model is based on either un-
lined, clay-lined, or synthetic-lined
design.
Model Usage
The Shawnee model can be of use to
utility companies or achitectural and en-
gineering firms involved in the selection
and design of SO2 removal facilities.
The model also has potential for use by
environmental groups or regulator
agencies. Although it is not intended to
be used for projecting a final design, it
can be used to assist in the evaluation of
system alternatives prior to a detailed
design. It should also be useful for eval-
uating the potential impact of various
process variables on economics as a
guide for planning.
Although the model was not meant to
be used for comparing projected lime/
limestone economics with economics
for alternate processes, these compari-
sons should be valid as long as the
bases for the alternate process econom-
ics are comparable to those included in
the computer model for lime and lime-
stone systems.
The manual contains information re-
quired to run the overall computer
model.
F. A. Sudhoff and R. L Torstrick are with TV A. Office of Power. Muscle Shoals, AL
35660.
J. David Mobley is the EPA Project Officer (see below).
The complete report, entitled "Shawnee Flue Gas Desulfurization Computer
Model Users Manual," (Order No. PB 85-243 111 /AS; Cost: $22.95, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
•&U. S. GOVERNMENT PRINTING OFFICE:1985/559-l 11/20693
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
.. .-;•-,.-> U.S.O7
Official Business
Penalty for Private Use $300
EPA/600/S8-85/006
0000329 PS
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