U.S. Environmental Protection Agency Industrial Environmental Research EPA-600/7-78~048d
Office of Research and Development Laboratory _ _ . . «^o
Research Triangle Park. North Carolina 27711 MafCn 1978
SURVEY OF FLUE GAS
DESULFURIZATION SYSTEMS:
LA CYGNE STATION, KANSAS CITY
POWER AND LIGHT CO.
Interagency
Energy-Environment
Research and Development
Program Report
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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.
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EPA-600/7-78-048d
March 1978
SURVEY OF FLUE GAS DESULFURIZATION
SYSTEMS: LA CYGNE STATION,
KANSAS CITY POWER AND LIGHT CO.
by
Bernard A. Laseke, Jr.
PEDCo Environmental, Inc.
11499 Chester Road
Cincinnati, Ohio 45246
Contract No. 68-01-4147
Task3
Program Element No. EHE624
EPA Project Officer: Norman Kaplan
Industrial Environmental Research Laboratory
Office of Energy, Minerals and Industry
Research Triangle Park, N.C. 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, D.C. 20460
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ACKNOWLEDGMENT
This report was prepared under the direction of Mr. Timothy
W. Devitt and Dr. Gerald A. Isaacs. The principal author was Mr.
Bernard A. Laseke.
Mr. Norman Kaplan, EPA Project Officer, had primary respon-
sibility within EPA for this project report. Information on
plant design and operation was provided by Mr. Clifford McDaniel,
SO2 Superintendent, Kansas City Power and Light Company; and Mr.
Jack Stewart, Sales Manager, Babcock and Wilcox Company.
11
-------
CONTENTS
Acknowledgment
List of Figures and Tables
Summary
1. Introduction
2. Facility Description.
3. Flue Gas Desulfurization System
Background Information
Process Description
Process Chemistry: Principal Reactions
Process Operating Parameters
Process Control
4. FGD System Performance
Rationale of Facility Operation
Operating History and Performance
Start-up and Subsequent Operation:
Problems and Solutions
System Economics
Appendix
A.
Plant Survey Form
Page
ii
iv
vi
1
2
7
7
9
13
15
17
22
22
23
33
39
43
ill
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LIST OF FIGURES
No.
1 Process flow diagram for the La Cygne No. 1 scrubbing 6
system
2 B&W wet-limestone-scrubbing pilot plant facility 8
3 Cutaway view of a La Cygne FGD module and ancillary 10
components
4 Gas and liquid circuits of a La Cygne FGD module 19
LIST OF TABLES
No. Page
1 Data Summary: La Cygne Facility and FGD System ix
2 Typical Analysis of La Cygne No. 1 Coal 3
3 Design, Operation Emission Data, La Cygne Units 1 5
and 2
4 Composition and Concentration of the Recirculation 15
Tank Species
5 Summary of Data: Particulate and SO, Scrubbers 20
6 Summary of Data: FGD System Hold Tanks 21
7 Typical Pressure Drop Across Components of FGD 21
Train
8 Module Availability Summary - La Cygne January 25
1974 to December 1977
9 La Cygne Unit 1 4-Hour Full Load Test 29
10 La Cygne Unit 1 8-Hour Maximum Continuous Load Test 31
iv
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List of Tables (continued)
No. Page
11 FGD Operating Costs, La Cygne Unit 1, June 1973 to 41
September 1977
12 Total Capital Costs for the La Cygne Unit 1 Power 42
Generating Unit and FGD Facility
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SUMMARY
The wet limestone FGD system at the La Cygne Power Station
of the Kansas City Power and Light Company simultaneously removes
particulates and sulfur dioxide from flue gases. This scrubbing
system, which consists of eight modules, was designed and fabri-
cated by the Babcock & Wilcox Company and installed as an
integral part of the electric power generating facility. All
flue gases are treated, and the ductwork is arranged so that they
cannot bypass the FGD modules. Facilities for limestone grinding
and storage and final disposal of flue gas cleaning wastes are
located on the plant grounds.
Construction started in April 1969 and reached the halfway
point in October 1971, at which time the construction force
exceeded 900 men. Unit 1 was nearing completion when the boiler
was first fired on December 26, 1972, and was considered complete
when the generating unit was declared commercial on June 1, 1973.
This date was only 1 month behind schedule. The peak generating
load (832 MW) was attained on June 2, 1973.
Initial operation of the FGD system began in February 1973,
and full commercial operation, on June 1, 1973. Several major
problems accompanied start-up and subsequent operation of the FGD
modules. These included massive scale formation, widespread
corrosion, induced-draft-fan problems related to vibration and
bearing overheating, limited capability of limestone preparation
and handling systems, valve and piping failures, nozzle plugging,
pump liner failures, and control malfunctions.
Many modifications had to be made in the design and opera-
tion of the system to overcome the operational problems without
applying a 100-man work crew or imposing sizable load restric-
vi
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tions. These modifications resulted in improved mechanical
reliability and cost-effective operation.
The total PGD system availability index has increased
steadily each year since commercial start-up. Values achieved in
1974, 1975, 1976, and 1977 were 76, 84, 92, and 93 percent,
.respectively. These values indicate an annual average increase
of approximately 4 percent.
The utility conducted a series of stack sampling tests in
March and May of 1975 to check the efficiency of the system.
Testing was at full load and maximum continuous load. Results
showed particulate and S02 removal efficiencies of 98.2 and 80.14
percent, respectively, an indication that design values were
being attained.
The system is designed for. closed-water operation. Spent
2
limestone slurry and fly ash are removed to a 0.65-km (160-acre)
unlined settling pond via rubber-lined piping. Clear makeup
water is returned to the process. The loop is closed by recycl-
ing ball mill and module makeup water into the system.
Initial installed capital cost of the La Cygne wet scrubbing
system was approximately $34 million, which is equivalent to
$41/kW for a net generating capacity of 820 MW. Subsequent
equipment modifications have increased the cost to about $47
million or $59/kW. The reported operating cost for 1977 was 1.69
mills TcWh ($1.79 million), which includes operating materials,
operating labor, maintenance materials, maintenance labor, and
limestone.
In April 1977 the utility completed installation of an
additional FGD module, which went into commercial service on July
5, 1977. The capital cost of this eight module was approximately
$5.2 million. Its installation enabled the utility to increase
the maximum net continuous generating capacity of the unit from
700 to 800 MW and still comply with emission regulations.
Availability index: the number of hours the FGD system is avail-
able for operation (whether operated or not), divided by the
number of hours in the period, expressed as a percentage.
vil
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Table 1 summarizes pertinent data on the facility and the
FGD system.
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Table 1. DATA SUMMARY: LA CYGNE FACILITY AND FGD SYSTEM
Unit rating, net MW
Fuel
Fuel characteristics
Type
Gross heating value,
MJ/kg (Btu/lb)
Ash content, %
Sulfur content, %
FGD system supplier
Process
New or retrofit
Initial start-up date
Commercial start-up date
Number of FGD modules
Removal efficiency, %
Particulate (measured)
Sulfur dioxide (measured)
Sludge disposal
Unit cost
Capital (1977)
Operatinga (1977)
820
Coal
Subbituminous
21 to 23 (9000 to 9700)
25
5
Babcock & Wilcox
Wet limestone scrubbing
New
February 1973
June 1973
8
98.20
80.14
Unstabilized sludge is
disposed of in an on-site
unlined pond
$46.8 million or
$59/kW net
$3.038 million or
1.693 mills/kWh
The reported operating costs are for the first 9 months of 1977.
ix
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SECTION 1
INTRODUCTION
The Industrial Environmental Research Laboratory (IERL) of
the U.S. Environmental Protection Agency (EPA) has initiated a
study to evaluate the performance characteristics and reliability
of flue gas desulfurization (FGD) systems operating on coal-fired
boilers in the United States.
This report, one of a series dealing with FGD-systems,
describes a limestone scrubbing process developed by Babcock &
Wilcox (B&W) and installed at the La Cygne Power Station of
Kansas City Power and Light Company (KCP&L).
This report updates an earlier one that was based on
information obtained during an inspection of the La Cygne Power
Station on June 5, 1974, and on data provided by utility and
system supplier personnel during that visit. The installation
was visited again on June 23, 1976, to gather additional informa-
tion for this report. The utility has also provided additional
data since the second visit.
Section 2 provides information and data on facility design
and operation. Section 3 describes the FGD system, the process
chemistry, and the control strategy. Section 4 presents an
analysis of FGD system performance. The appendices present
details of plant and system operation.
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SECTION 2
FACILITY DESCRIPTION
The La Cygne power station is a new coal-fired facility,
jointly owned by the Kansas Gas and Electric Company and KCP&L.
It is located in Linn County, Kansas, 88 km (55 miles) due south
of Kansas City. The site is surrounded by relatively flat
farmland and pasture. There are no other major industrial
facilities in the immediate area. The nearest population center
is the town of La Cygne (approximately 1000 people), which is
located approximately 9.6 km (6 miles) west of the station.
Unit 1 at La Cygne is a wet-bottom, cyclone-fired, boiler
manufactured by B&W. This supercritical, once-through balanced-
draft unit generates 2800 Mg (6,200,000 Ib) of steam per hour,
with 543°C, 26.3 MPa (1010°F, 3825 psig) at the superheat outlet
and 543°C (1010°F), at the reheater outlet. The turbine genera-
tor, manufactured and supplied-by the Westinghouse Company, has
a design-rated gross output of 874 MW, with 5 percent overpres-
sure and 24 MPa (3500 psi) throttle pressure. The station also
contains three auxiliary oil-fired boilers, which are used for
plant start-ups or to power a 20-MW house turbine generator.
Since 30 MW of the total gross megawatt rating of the turbine
generator is used to power the plant's auxiliary equipment and 24
MW is required to operate the emission control system, the net
electrical power output is 820 MW.
Particulate and SO, emissions are controlled by a system
consisting of eight identical modules, each with a two-stage
venturi scrubber and tray tower absorber. These modules were
designed, manufactured, and installed by B&W as an integral part
of the power generating facilities. Ductwork is arranged so that
flue gases cannot bypass the scrubbing modules.
2
-------
The boiler burns low-grade, subbituminous coal, which is
delivered to the plant in off-the-road 108-Mg (120-ton) trucks
from nearby surface mines operated by the Pittsburgh & Midway
Coal Mining Company. Deposits at these mines are estimated at 70
million tons. This supply is considered adequate for the life
span of La Cygne Unit 1. Table 2 presents a typical analysis of
this coal.
Table 2. TYPICAL ANALYSIS OF LA CYGNE NO. 1 COAL
(percent except as noted)
Description
Heating value (as-fired), MJ/kg (Btu/lb)
Volatile matter
Fixed carbon
Sulfur
Ash
Chloride
Moisture
Grindability
Value
21.95 (9421)
28.63
37.94
5.39
24.36
0.027
8.60
59.59
The utility has installed a second electric power-generating
unit (Unit 2), rated at 630 MW. Power is supplied to the
generator from a coal-fired boiler that fires low-sulfur Wyoming
coal (0.32 % sulfur). Unit 2 was placed in commercial service on
May 15, 1977. The emission control system for this second unit
consists of a full-capacity electrostatic precipitator (ESP),
supplied by Lodge-Cottrell, for primary particulate control.
Burning low-sulfur coal enables plant operators to comply with
S02 emission regulations without controls.
For Unit 1, the maximum particulate emission allowed under
Kansas State Department of Health and Environment Regulation No.
28-19-31-A is 60 ng/J (0.13 lb/106 Btu) of heat input to the
boiler. A test measuring particulate emission from the FGD
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system showed, actual emissions to be equivalent to 77.5 ng/J
(0.18 lb/106 Btu).
The maximum sulfur emission allowed under Regulation No. 28-
19-31-C is 645 ng/J (1.5 lb/106 Btu) of heat input to the boiler.
The present SCU emission rate from the La Cygne station/ based on
80 percent removal efficiency in the FGD system, is equivalent to
about 860 ng/J (2 lb/106 Btu). This figure is based on 95
percent conversion of the sulfur to sulfur dioxide. Thus, the
actual SO2 emissions are well below the emission limitation level
of 1290 ng/J (3 lb/106 Btu).
Table 3 presents data on plant design, operation/ and
atmospheric emissions for Units 1 and 2. Figure 1 is a process
flow diagram of the La Cygne wet limestone FGD system, including
the additional module now in service.
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Table 3. DESIGN, OPERATION AND EMISSION DATA,
LA CYGNE UNITS 1 AND 2
Description
Maximum generating capacity, net MW
Boiler capacity factor, percent
(1977)
Served by stack no.
Boiler manufacturer
Year placed in service
Maximum coal consumption:
Mg/hr
(Short tons/hr)
Maximum heat input:
GJ/hr
(106 Btu/hr)
Stack height above grade:
Meters
(ft)
Design maximum flue gas rate:
m3/sec
acfm
Design flue gas temperature.
«C («F)
Emission controls:
Particulate
SO,
2
Particulate emission rate:
Allowable, ng/J (lb/106 Btu)
Actual, ng/J (lb/10B Btu)
SO 2 emission rate:
Allowable, ng/J (lb/106 Btu)
Actual, ng/J (lb/10» Btu)
Unit 1
820
44
1
BtH
1973
366
(404)
8100
(7676)
213
(700)
1300
2,760,000
140 (285)
Venturi
scrubber
Venturi
scrubber
and
counter -
current
absorber
tower
56 (0.13)
775 (0.18)
645 (1.5)
860 (2.0)
Unit 2
630
BO
2
BSW
1977
213
(700)
1250
2,643,000
302 (150)
Electrostatic
precipitator
(todge-Cottrell/
Dresser Industries)
None; low-sulfur
coal
43 (0.10)
516 (1.2)
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Figure 1. Process flow diagram for the La Cygne No. 1 scrubbing system.
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SECTION 3
FLUE GAS DESULFURIZATION SYSTEM
BACKGROUND INFORMATION
The wet limestone FGD system at the La Cygne Power Station
was designed, fabricated, and installed by B&W. The research,
development, bench-scale work, and pilot-plant testing that
ultimately led to the development of this process took place at
B&W's Research and Development Center in Alliance, Ohio.
B&W originally became involved in FGD technology late in the
1960's when they initiated a research and development program on
both regenerable and nonregenerable scrubbing processes.
Experimental work in nonregenerable processes eventually led to
the investigation of a number of chemical-based processes for
removal of S02 as a waste product. The investigation included
bases such as sodium carbonate, sodium hydroxide, ammonia, lime,
and limestone. Economics were also considered. Factors.such as
raw material costs and necessary waste handling equipment
eventually led to emphasis being placed on a process using
limestone slurry and a design configuration that would allow S0_
removal from flue gas streams at a minimum efficiency of 80
percent.
Follow-up research on limestone FGD processes consisted of
mathematical and computer modeling, factorial analyses of process
variables, chemical analyses evaluating the suitability of
various types of limestone, further and more detailed economic
analyses, and, finally, the construction of a pilot plant at
B&W's Research Center in Alliance.
A schematic equipment and flow diagram of the pilot facility
is presented in Figure 2. The pilot plant contained the follow-
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00
FLUE GAS REHEATER
THICKENER
COUNTERCURRENT
TRAY
PARTICULATE VENTURI
SCRUBBER
WATER TUBE
SECTION
LIMESTONE SLURRY
PREPARATION AND
FEED
RECYCLE
TANK
230 kg/hr
(500 Ib/hr)
COAL-FIRED
FURNACE
VACUUM
BELT FILTER
Figure 2. B&W wet-limestone-scrubbing pilot plant facility.
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ing components: a 230 kg/hr (500 Ib/hr) pulverized-coal furnace,
a steam generating bank, a venturi scrubber and countercurrent
tray absorber module, a steam coil gas reheater, and an induced-
draft fan. The pilot facility also included a limestone prepara-
tion and circulation system, a thickener, and a vacuum belt
filter.
The facility design allows maximum water recovery which
makes it possible to determine the effects of dissolved solids
buildup and scale formation potential of various types of lime-
stone and fuel.
Following completion of the pilot program, a full-scale
facility was installed for demonstration on the new coal-fired
boiler at the La Cygne power station.
PROCESS DESCRIPTION
The La Cygne wet limestone FGD system consists of eight
scrubber-absorber modules designed to treat the total boiler flue
gas load capacity of 1300 m /sec (2,760,000 acfm). This is equal
to 185 m3/sec (394,300 acfm) per module at 140°C (285°F).
Ductwork design is such that flue gas cannot bypass the scrubbing
system, but the individual damper systems allow each module to be
isolated for maintenance and repairs. Figure 3 presents a
cutaway view of one of the scrubber modules.
Limestone is obtained from nearby quarries owned and operated
by the Bates City Rock Co. and delivered to the plant site in
off-the-road 45-Mg (50-ton) trucks. The delivered limestone
consistently averages 1.9 cm. x 0 cm. (3/4 in. x 0 in.). A 54
Gg (60,000-ton) supply is maintained near the plant coal storage
area. It is transported continuously by a separate conveyor
system. Two wet ball mills, each capable of processing 100 Mg/hr
(110 ton/hr) of limestone, grind the rock to a fineness of 95
percent minus 200 mesh at 66 percent solids before it is mixed
into a slurry. The limestone has the following chemical charac-
teristics: a minimum of 85 percent calcium carbonate, a maximum
of 2.5 percent magnesium carbonate, 8 percent moisture, and 7
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MIST ELIMINATOR
SIEVE TRAY
(PREDEMISTER)
RECIRCULATION
PUMP
RECIRCULATION
TANK
RECIRCULATION
7^> - PUMP-
Figure 3. Cutaway view of a La Cygne FGD module
and ancillary components.
10
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percent gangue. The two ball mills are housed in a separate
building, which also contains two limestone preparation tanks and
two slurry tanks. The slurry, which is 20 percent solids by
weight, is pumped to each module at a rate of 12.2 I/sec to 36
I/sec (200 to 600 gpm). Total annual limestone consumption is
estimated to be 453 to 635 Gg (500,000 to 700,000 tons).
The hot boiler flue gas first enters the system through the
venturi scrubber of each module, where it is contacted with jets
of limestone slurry in a crosscurrent fashion. The slurry is
injected into the flue gas by 48 spinner-vane spray nozzles. At
this stage of the process, up to 99 percent of the particulates
in the flue gas is agglomerated and collected in the sump below.
Additional limestone slurry is injected through 32 wall wash
nozzles around the periphery of the venturi. This step wets the
convergent sides of the venturi, thereby preventing fly ash
deposition and providing an additional interface. The venturi
recirculation pump provides a continuous cycle of the slurry at
a rate of 305 to 366 I/sec (5000 to 6000 gpm}.
The gas flow continues through the sump, turns 90 degrees in
an upward direction, and proceeds through a series of sieve
trays. As the gas exits the venturi and flows through the sump
into the absorber, its superficial velocity decreases from 39.6
m/sec (130 ft/sec) at the throat to 4.6 m/sec (15 ft/sec) and
then to 2.6 m/sec (8.4 ft/sec) at the mist eliminator. The gas
passes through two layers of stainless steel absorber sieve
trays, which have 3.5-cm (1-3/8-in.) diameter holes and 38-cm
(15-in.) skirts that form many open frothing boxes. Slurry is
pumped to the absorber through 16 spinner-vane spray nozzles,
where it showers through the trays counter to the flue gas flow.
The SO, is removed from the flue gas and converted to calcium
2£
salts.
The cleaned gas passes through a predemister (actually a
third stainless steel sieve tray), then upward through a 25-cm-
11
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deep (lO-in.-deep) chevron mist eliminator constructed of
fiberglass-reinforced plastic. Entrained moisture droplets are
removed from the gas stream and fall to the trays below. Chev-
rons are provided with an overspray wash system to prevent
clogging in the 8-cm (3-in.) spacings. The overspray consists of
blended pond water applied at a rate of 14.5 I/sec (230 gpm).
The saturated flue gas exits the mist eliminator at a
temperature of 50°C (122°F) and enters an in-line stack gas steam
tube reheat system, which provides a temperature boost of 28°C
(50°F) before the gas is discharged to the atmosphere. The
reheater in each module consists of eight banks of steam tube
bundles of four rows per bank . The steam tubes are 1.6-cm (5/8-
in.) outer diameter, 316L stainless steel bare tubes which
convey 0.96 kg/sec (7600 Ib/hr) of 965 kPa (140 psig), 365°C
(690°F) extraction steam. Each reheat unit also contains a set
of four soot blowers, which operate every 4 hours to clean the
reheater tubes.
After passing through the reheat section, the gases enter a
common plenum at a temperature of 78°C (172°F) . The gas then
feeds into six ducts 3.6m (12 ft) in diameter and is discharged
to a 312-m (700-ft) steel-lined stack via six 5200-kW (7000-hp)
induced-draft booster fans. One booster fan is installed in each
of the six ducts that discharge into the base of the stack at
equal 60 degree spacings.
The venturi scrubber and countercurrent tray absorber of
each module use a common recirculation tank for completion of
chemical reactions, addition of fresh alkali, and discharging of
spent slurry and fly ash to the waste disposal area. The venturi
recirculation line from the tank to the scrubber is equipped with
*
Currently three of the eight modules include two-stage chevron
mist eliminators. The remaining five modules include single-
stage mist eliminators.
Currently three of the eight modules include eight banks of
four tubes/bank steam heat exchangers. The remaining five
modules include four banks of four tubes/bank steam heat ex-
changers .
12
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a hydroclone which centrifugally separates large particles of
scale from the scrubbing liquor and discharges them through a
screen back to the recirculation tank. This minimizes plugging
of the nozzles and strainers and reduces erosion in the pumps,
pipes, and nozzles.
Scrubbing wastes in the amount of 3200 Mg (3500 ton) of
solids per day are removed from the module recirculation tanks
2
through a spent slurry valve and rubber-lined pipes to a 0.65-km
(160-acre) settling pond. Clear makeup water is pumped from the
pond, and the water loop is closed by recycling ball mill and
module makeup water into the system. Water is recycled to the
process at a rate of 447 kg/sec (3,550,000 Ib/hr) . The settling
pond is equipped with an overflow weir, which permits water to
flow into a larger pond that is used primarily for plant cooling
water. Utility analyses of the return water concentrations of
the calcium and sulfate ion species to be 856 and 2130 ppm,
respectively .
PROCESS CHEMISTRY: PRINCIPAL REACTIONS
The chemistry involved in the wet limestone system at the La
Cygne Power Station is complex, and details are beyond the scope
of this report. The principal chemical mechanisms are discussed
briefly in the following paragraphs.
The first and most important step in the wet-phase absorp-
tion of S05 from the flue gas stream is diffusion of the species
from the gas to the liquid phase. Sulfur dioxide is an acidic
anhydride that readily forms an acidic species in the presence of
water ,
S02 * ±==^ S°2(aq.)
S02(aq.) +H2° ^^ H2S°3
In addition, some SO- is formed by the additional oxidation of
-
e flue
2S0
the S02 in the flue gas stream.
2
This species, like S02/ is an acidic anhydride, readily forming
13
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an acid in the presence of water,
S03 * *=* S03(aq.)
S03(aq.) +H2° ±=^ H2S04
The sulfurous and sulfuric acid compounds are polyprotic
species, the sulfurous species weak, and the sulfuric species
strong. Their respective dissociation reactions into ionic
species occur in the following manner:
H2S03 •* > H+ + HSO~
HSO~ * > H+ + SO3
HS0 ±= H+ + HSO~
ESO~ ±=£ H+
Analogous to the oxidation of sulfur dioxide to form sulfur
trioxide, sulfite ion has a limited tendency to undergo oxidation
by dissolved oxygen in the slurry,
2S03+02(aq.) =Z 2S°4
The limestone is originally slurried with water for use in
the scrubbing system. The absorbent, which is approximately 85
percent calcium carbonate by weight, is quite insoluble in
water, the solubility increasing only slightly as the temperature
increases. The slurry dissolves and ionizes into an acidic
aqueous medium when introduced into the scrubbing system, yield-
ing the ionic products of calcium, carbonate, bicarbonate, and
hydrogen .
The chemical absorption of sulfur dioxide occurs in the wet
scrubber vessels and is completed in the external recirculation
tank. The reaction products precipitate as calcium salts, and
the scrubbing solution is recycled to the scrubbers for further
use. The principal reaction mechanisms for product formation and
precipitation are as follows.
14
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CaS03
CaS03 + 1/2 H20 * „ CaS03-l/2 H20
Ca++ + SO^ •* » CaS04
CaS04 + 2H20 * » CaS04-2H20
The hydrated calcium sulfite and calcium sulfate products, along
with the collected fly ash and unreacted limestone, are then
transferred to the sludge pond for settling and final disposal.
The supernatant is recycled to the system.
Reactions in the recirculation tank are completed in the 5.5
to 6.0 pH range. Table 4 lists the various components present
and their corresponding concentrations/ as determined by the
utility.
Table 4. COMPOSITION AND CONCENTRATION OF THE
RECIRCULATION TANK SPECIES
Calcium carbonate
Calcium sulfite
Calcium sulfate
Fly ash
Solids
pH
70 g/1 (0.6 Ib/gal.)
35 g/1 (0.3 Ib/gal.)
25 g/1 (0.2 Ib/gal.)
40 g/1 (0.3 Ib/gal.)
10 percent/ weight
5.5 to 6.0
PROCESS OPERATING PARAMETERS
The utility and the system supplier have made many major
modifications to the scrubbing system, resulting in alteration of
many of the original design parameters. The modifications were
intended'primarily to reduce or ameliorate problems encountered
in operation of the boiler and FGD facility. Section 4 explains
the rationale and nature of these modifications. Actual operating
conditions are described below:
(1) Each of the original seven scrubber-absorber modules
was designed to treat approximately one-seventh of the
15
-------
total boiler flue gas at full-load capacity [185 m /sec
at 140°C (394,285 acfm at 285°F)]. Because of scrubber
process control considerations, however, the unit was
forced to operate at a maximum continuous generating
capacity well below full load (i.e., 700 to 720 MW
instead of 820 MW). The actual flue gas flow per
module at maximum continuous generating capacity
(actual operating conditions) was approximately 130 to
140 m3/sec (280,000 to 300,000 acfm) at 57°C (135°F).
The addition of an eighth scrubber-absorber module in
June 1977 allowed operation of the unit at full load
capacity.
(2) Each module is equipped with a 100-percent-capacity
venturi recirculation pump rated at 472 I/sec (7750
gpm), and supplied with 261-kW (350-hp) drives. After
hydroclones were installed in the venturi recirculation
lines, however, the pressure head of the recirculation
pump increased, and the recirculation rate is now
approximately 305 I/sec (5000 gpm).
(3) The design liquid-to-gas ratio (L/G) for the venturi
scrubber is 2.4 1/m (18 gal./lOO acf) of gas. The
actual L/G is approximately 1.6 1/m (12 gal./lOOO
acf).
(4) The original design reheater exit temperature was
63.9°C (147°F). Because this temperature was insuffi-
cient to protect downstream equipment from corrosion
and provide adequate plume buoyancy, additional reheat
was supplied by providing 287°C (550°F) steam to the
reheat coils and by injecting 257°C (495°F) hot air
from the boiler air heaters into the gas stream prior
to the reheat section. This latter practice was
reduced when the eight scrubber-absorber module was
placed in service in April 1977 (almost all the hot air
from the boiler air heaters was required for full-load
operations). Additional reheat banks were installed to
maintain an exit temperature of 88°C (190°F).
16
-------
(5) The original design stoichiometric requirement for
limestone addition was 1.7- The actual amount was
maintained at twice stoichiometric during manually
controlled operations. Limestone addition was tied
into the automatic pH-controlled circuit in early 1977.
The success of this mode of operation has reduced the
limestone stoichiometric requirement to the original
design value of 1.7, reducing daily consumption from
5000 Mg (5500 ton) to 1360 Mg (1500 ton).
PROCESS CONTROL
The process control system relies primarily on the pH and
the solids content of-the scrubbing solution. The pH is main-
tained between 5.6 and 5.8, a range that permits optimum per-
formance of the stainless steel components. Chemical reactions
within the scrubbing system also depend on pH. If the pH exceeds
5.8, limestone utilization decreases, stoichiometric requirements
increase, and soft scale tends to accumulate rapidly. If the pH
drops below 5.6, a hard gypsum scale builds up within a short
time. Operation below this pH range tends to promote acid and
chloride attack, especially in creviced and uncleared scrubber
areas. The 5.6 to 5.8 pH range is maintained by regulating the
amount of limestone added to the system. The pH of the scrubbing
solution is monitored by a meter located in the wall wash header
at the throat area inside the venturi scrubber. The amount of
limestone feed is regulated as a function of the pH readings
inside the venturi. Specifically, if the solution pH drops below
5.6, more limestone is added automatically by opening the slurry
feed valves. The utility also stores an adequate supply of lime
in the scrubber area to cover emergencies caused by a sudden pH
drop.
The solids content of the scrubbing solution is maintained
in the range of 18 to 20 percent. Recirculation of the scrubbing
liquor at this level allows maximum S02 removal with minimum
problems. The abrasion of scrubbing equipment, such as pumps and
17
-------
piping, and the corrosion of scrubber internals, such as mist
eliminators and reheaters, are reduced and kept to a minimum.
The solids content of the scrubbing solution is monitored in the
venturi recirculation line by a nuclear density meter. When the
solids content exceeds the 20 percent level, a bleed stream is
2
discharged from the recirculation line to the 0.65-km (160-acre)
settling pond.
Figure 4 presents a diagram of the major equipment and
control components of a typical La Cygne FGD module. Tables 5,
6, and 7 summarize operating and design parameters and specifi-
cations for the major components.
18
-------
-5 kPa
(-20 in: H-0)
FLUE -'
GAS
^
N
\
VENTURI SPRAY
WALL
WASH
SPRAY
VEMTURI
THROAT
FLUSH
»•
HYDROCLONE
SPENT SLURRY
TO POND
44 V sec (700 gpm)
454 Mg/day (500 tons/day
89.800 Mg/yr (99.000 tow/yr
58,000 m3/yr (47 ACRE ft/yr)
"^-^—
-11 kPa
-43 In. H,0)
•v 1000 ppw S02 's
\ STEAM 88*C (190°F) x^
\ 288»C (550BF) REHEAT COILS
J i n n o 0 n n r,— .
] A" ^ HOI AIR
. /I X XI c-nftn
\ /I / MIST ELIMINATOR* \ "— FROM
y^^'TP / \ BOILER 4S
TO
I.D.
FAN
5°F
NUOUS
1 I '/\ /\ S\~/\ X^"7W\ OVERSPRAY
kt- 5S5$55^55$> HIST EL1MIMATOR
\ / [yiv^1-1- V V V \/ \/ \/ \/ CONTINUOUS
\ / V=^= ' ' WtDERSPRAY
n
\
\
2
1/s
too
•->
c
s
gpm]
i
"if \ \ PREOEMISTER /
/ \ \ / ABSORBER
/ \ \ / SPRAY
1 £^£F:
ABSORBER
\ /
^V X ClfUD f
\SCREENS 5UHK SCREEN/ so£ VENT
a 13-38 l/sec U
(200-600 gpro) (^
H: .
RECIRCULATION TANK
CaC03 70 g/1 (0.6 lb/gal.)
CaS03 35 g/1 (0.3 lb/gal-)
CaS04 25 g/1 (0.2 Ib/gal-)
FLYASh 40 g/1 (0.3 lb/gal.)
IpH • 5.5-6.0 1 /"/
18-20X SOLIDS j \JJ
LIMESTQK
SLURRY
20«
SOLIDS
VENTURI
RECIRC. PUMP
315 I/sec (5000 gpm)
*2nd STAGE MIST ELIMINATOR INCLUDED IN 3 OF 8 NODULES
RECIRC. PUMP
568 Usec (9000 g|»)
Figure 4." Gas and liquid circuits
of a La Cygne FGD module.
19
-------
Table 5. SUMMARY OF DATA: PARTICULATE AND S02 SCRUBBERS
Venturi scrubber
S02 scrubber
tower
L/G, l/m° (gal./lOOO'acf)
Superficial gas
velocity, m/sec (ft/sec)
Dimensions
Equipment internals
Material of
construction:
Shell
Internals
1.6 (12)
40-45 (130-150)
6.55 m (21-1/2 ft)
long x 56 cm
(22 in.) wide
Adjustable throat
maintained at
widest opening
316L stainless
steel"
Kaocrete ceramic,
(throat blocks
area)
3.5 (26.5)
2.6 (8.4) at
mist eliminator
9.7 m x 4.9 m
x 20 m
(32 ft x 16 ft
x 65 ft) high
Sieve trays
3.5-cm
(1-3/8-in.)
diameter holes
316L stainless
steel
316L stainless
steel
20
-------
Table 6. SUMMARY OF DATA: FGD SYSTEM HOLD TANKS
Recirculation
tank
Limestone
slurry
makeup tank
Total number of tanks
Dimensions, m (ft)
Retention time at full
load, minutes
Temperature, °C (°F)
PH
Limestone concentration,
Total solids concentra
tion, %
Material of
construction
8
9 (30) dia. x 7.3
(24) high
8
49 (121)
5.5-6.0
8-10
18-20
Rubber-lined
carbon steel
11 (36) dia. x 7.9
(26) high
120
Ambient
7.5
20
Rubber-1ined
carbon steel
Table 7. TYPICAL PRESSURE DROP ACROSS COMPONENTS OF
FGD TRAIN
Equipment
Pressure drop,
kPa (in. W.G.)
Venturi scrubber
SO2 absorber trays
Predemister
Mist eliminators
Reheater
Ductwork
Total FGD system
1.7 (7)
1.5 (6)
0.3 (1.2)
0.1 (0.2)
0.9 (3.6)
1.0 (4)
5.5 (22)
21
-------
SECTION 4
FGD SYSTEM PERFORMANCE
RATIONALE OF FACILITY OPERATION
The FGD system at the La Cygne power station is an integral
part of the power production system. Because the modules provide
primary control of both S02 and particulates, the ductwork design
does not permit flue gas to bypass the FGD system. Each module
can be removed and isolated from the gas stream for maintenance,
but not without reducing boiler loads.
The La Cygne boiler-scrubber design is such that emphasis
has had to be placed on optimizing FGD system operation. This
emphasis, which is not necessary for many emission control
systems that incorporate dry particulate removal components
upstream of wet scrubbers (thus allowing flue gas bypass of the
FGD system), has had the following ramifications.
1. Before installation of the eighth module, the maximum
continuous load capacity of La Cygne Unit 1 was 700 MW.
This power generation capacity allowed maximum scrubbing
system availability over an extended period of time.
Exceeding this output made the scrubbers susceptible to
chemical and mechanical problems, which resulted in
forced outages and subsequent cutbacks in power produc-
tion.
2. The utility appointed a separate superintendent and
support crew for FGD operation and maintenance. This
crew consists of operators, maintenance, and administra-
tive personnel totalling 54 people, who are deployed
over all three operating shifts.
3. An extensive preventive maintenance program is followed.
Generally, the night-load requirement is such that the
22
-------
unit operates at 50 to 67 percent capacity during an 8-
to 10-hour period extending from late evening to early
morning. During this period, one or two of the modules
are shut down for inspection, cleanout, and if necessary,
modifications and repairs. Shutdowns are rotated so
that preventive maintenance is conducted on each module
at least once each week.
4. The purpose of the FGD system is to enable the utility
to achieve compliance with air quality regulations
while producing the maximum number of kilowatt hours of
electricity. Thus, achieving optimum daily operations
takes precedence over research and development of
scrubbing technology. Priority for solution of
problems is in this order: mechanical, chemical, and
instrumental. At present, the utility is emphasizing
reliability of mechanical components. Investigations
into the chemical and instrumental aspects of the
system will proceed when the utility believes that
mechanical reliability has been achieved.
5. Two scrubber modules (A and D) are being used for
limited research testing. Tests are concentrating
primarily on modifications of the mechanical design of
the modules.
OPERATING HISTORY AND PERFORMANCE
Trial operation of the boiler and FGD system began on
December 26, 1972. Numerous problems, mostly mechanical, were
encountered. These problems (primarily concerned with fabrica-
tion and design) were corrected, and the boiler and FGD system
began operating commercially in June 1973.
Many major mechanical problems accompanied this subsequent
operation as well, along with some chemical problems. These
include massive formation of scale, serious corrosion, fan blade
vibration, problems.with limestone handling and slurry prepara-
tion, plugging of nozzles, control malfunctions, and failure of
23
-------
valves, piping, pump liners, and expansion joints.
An extensive preventive maintenance program and continuing
system modifications have resulted in a steady annual increase in
the number of FGD scrubber operation hours since start-up in June
1973. Total system availability index values for 1974, 1975,
1976, and 1977 averaged 76, 84, 92, and 93 percent, respectively.
Table 8 summarizes the performance of the La Cygne FGD system on
an individual module basis.
The La Cygne air quality control system is designed for
98.75 percent particulate removal which corresponds to an outlet
particulate emission of 60 ng/J (0.13 lb/10 Btu) heat input.
The system is designed for 80 percent SO9 removal, which corre-
*• c
spends to an outlet SO2 emission rate of 860 ng/J (2 lb/10 Btu)
heat input. Design values are based on high-sulfur Kansas coal
with a heating value of 19 to 23.8 MJ/kg (8200 to 10,200 Btu/lb),
an ash content 20 to 30 percent, and a sulfur content of 5 to 6
percent.
The utility conducted two system performance tests to
determine actual particulate and S02 removal efficiency values.
Tests were conducted under two different boiler load conditions:
a full-load capacity of 800 to 830 MW and a maximum continuous
capacity of 700 to 720 MW. A 4-hour, full-load test was con-
ducted on March 24, 1975. The unit maintained a load range of
800 to 830 MW throughout the test, with seven modules fully
loaded. The SO2 removal efficiency of the total system, for the
six modules from which the results were obtained, was 76.2
percent. An 8.5-hour test was conducted by an independent test
group on May 15, 1975, to ascertain maximum continuous capacity.
The load range during the test was 700 to 720 MW. The particulate
and SO2 removal efficiencies for seven modules combined were 98.2
and 80.14 percent, respectively. Tables 9 and 10 present details
of these performance tests.
24
-------
Table 8. MODULE AVAILABILITY SUMMARY - LA CYGNE JANUARY 1974
TO DECEMBER 1977
Period
January 74
February 74
March 74
April 74
May 74
June 7 4
July 74
? August 74
September 74
October 74
November 74
December 74
Total
Boiler
operating
hours
364
364
332
500
480
313
571
606
662
386
4578
Module availability, percent
A
49
66
67
69
92
75
90
69
71
90
75
B
32
68
70
83
84
80
90
88
61
71
74
C
44
59
D
87
76
E
23
52
P
37
100
Turbine and boiler shutdown
75
78
83
80
73
73
59
60
Ti
69
88
85
90
81
81
76
81
61
irbine and b
81
74
78
82
85
81
83
79
84
oiler shutd
74
100
84
83
79
78
89
93
85
own
84
G
81
65
88
80
87
77
99
86
89
84
83
Average
50
69
80
80
86
80
85
81
76
76
76
LT.
(Continued)
-------
Table 8. (Continued1)
Period
January 75
February 75
March 75
April 75
Hay 75
June 75
July 75
August 75
September 75
October 75
November 75
December 75
Total
Boiler
operating
hours
394
683
667
590
630
610
231
346
597
5048
Module availability, percent
A
82
95
88
78
75
78
66
93
91
83
B
96
85
85
90
88
84
77
90
87
87
C
T>
T\
90
Tl
94
84
90
87
84
46
80
81
82
D
E
F
rbine and boiler shutdown
1 1
rbine and boiler shutdown
76
rbine and t
90
85
84
78
85
74
93
85
83
93
oiler shutd
90
84
85
92
79
72
96
87
86
82
iwn
89
86
87
85
78
73
89
89
85
G
96
83
89
85
83
74
65
94
84
84
Average
90
89
86
86
84
80
68
91
86
84
to
a\
(Continued)
-------
Table 8. (Continued).
to
Period
January 76
February 76
March 76
April" 76
Hay 76
June 76
July 76
Augustb 76
September 76
Octoberb 76
November 76
December 76
Total
Boiler
operating
hours
618 >
594
643
143
436
656
688
521
256
627
706
5888
Module availability, percent
A
86
94
92
92
96
93
96
94
97
95
87
93
B
85
90
90
91
92
94
95
93
97
93
89
91
C
91
86
88
89
93
94
92
92
D
72
91
93
97
96
95
93
94
E
84
92
94
96
89
92
93
92
Turbine repair, stack relining
98
94
81
90
89
95
94
91
96
94
94
92
P
52
93
91
98
95
94
94
90
96
93
95
88
G
84
95
91
95
96
91
94
88
96
94
91
92
Average
83
92
91
94
94
93
94
92
96
94
90
92
* A scheduled turbine and boiler outage lasting 24 days occurred during the month.
The unit was taken out of service on August 24 for turbine blade repairs. KCPtL took advantage of this turbine outage
to reline the stack. The outage lasted from August 24 to October 20.
(Continued)
-------
Table 8. (Continued)
Period
January 77
February 77
March 77
April 77
Hay 77
June 77
July 77
August 77
September 77
October 77
November 77
December 77
Total
Boiler
operating
hours
539
590
558
384
15
485
501
524
456
234
4286
Module availability, percent '
A
94
93
94
96
95
89
93
91
93
93
B
90
93
92
94
93
55
94
96
96
89
C
95
93
86
97
Turbine
Turbine
94
93
89
89
93
D
95
94
94
94
E
95
93
91
95
repair, stack relining
repair, stack relining
95
93
90
94
94
Turbine repair
92
94
95
90
93
93
92
93
P
92
94
94
96
95
93
95
94
92
94
G
90
88
90
95
95
93
92
88
96
92
H
95
94
93
93
95
94
Average
93
93
92
95
95
87
92
92
94
93
NJ
00
-------
Table 9. LA CYGNE UNIT 1 4-HOUR PULL-LOAD TEST
Date: March 24, 1975
Time: 6:10 p.m. to 10:25 p.m.
Power: 800 to 83,0 MH
Ambient Temp: 60°F.
Parameter
Gas flow, m /sec (cfra)
Throat, cm (in.)
Reheat temp, °C (°F)
Absorber pump
Venturi pump flow
I/sec (gpm)
Venturi AP,
kPa (in. H..O)
Reheater AP,
kPa (in. H.,0)
Absorber mist eliminator AP,
kPa (in. HjO)
Hot air damper poa.,
» open
Reheat outlet damper pos.,
» open
Scrubber outlet press.,
kPa (in. HjO)
I.D. fan, amp
I.D. fan inlet damper poa.,
% open
Solution pH
Modular values
A
178 (380,000)
56 (22)
77 (170)
ON
252 (4000)
1.9 (8.0)
1.0 (4.0)
-
46
51
9.5 (38.3)
540
100
5.95
B
169 (360,000)
52 (22)
82 (180)
ON
252 (4000)
1.9 (7.5)
0.87 (3.5)
1.4 (5.5)
23
37
520
98
5.89
C
188 (400,000)
56 (22)
82 (180)
ON
315 (5000)
-
0.75 (3.0)
-
44
98
9.6 (38.4)
620
98
5.80
D
192+ (410,000+)
56 (22)
66 (150)
ON
252 (4000)
2.7 (11.0)
0.87 (3.5)
2.1 (8.5)
-
84
600
100
5.68
E
188 (400,000)
56 (22)
66 (150)
ON
315 (5000)
26 (10.0)
0.25 (1.0)
2.1 (8.5)
48
100
380
100
5.92
P
183 (390.000)
56 (22)
77 (170)
ON
315 (5000)
2.7 (11.0)
1.1 (4.5)
2.2 (9.0)
32
96
380
23
5.79
G
160 (340,000)
56 (22)
85 (185)
ON
315 (5000)
2.2 (9.0)
3.1 (12.5)
2.2 (9.0)
64
100
5.73
to
vr>
(Continued)
-------
Table 9. (Continued).
Sulfite concentration
Ib/gal. (g/1)
Carbonate concentration
Ib/gal. (g/1)
SOj removal efficiency, »
Inlet, ppro
Outlet, ppro
0.34 (41.1)
0.78 (94.4)
75.1
5700
1419
0.30 (36.2)
0.70 (84.1)
79.1
513B
1075
0.38 (45. 9)
0.58 (69.4)
72.2
5516
1533
0.30 (35.4)
0.70 (84.4)
72.0
4995
1220
0.38 (45.1)
0.77 (91.9)
5700
0.25 (29.4)
0.91 (109.0)
82.9
5017
857
0.46 (54.7)
0.64 (76.6)
75.7
5120
1243
U)
o
-------
Table 10. LA CYGNE UNIT 1 8-HOUR MAXIMUM CONTINUOUS LOAD TEST
Date:
Time:
power:
Ambient Temp:
Overall average S02 removal: 80%
Overall particulate removal; 98.2%
Hay IS, 1975
11:30 a.m. to 8:00 p.m.
700 to 720 MW Continuous
72°F
Parameter
Gas flow, m /sec (cfm)
Throat, cm (in.)
Reheat temp, °C (°F)
Absorber pump
Venturi pump flow
I/sec (gpm)
Venturi AP.
kPa (in. H-,O)
Reheater AP,
kPa (in. HjO)
Absorber mist eliminator AP,
kPa (in. HjO)
Hot air damper pos., % open
Reheat outlet damper pos. ,
% open
Scrubber outlet press..
kPa (in. HjO)
I.D. fan, amp
I.D. fan inlet damper pos.,
% open
Solution pH
A
150 (320,000)
56 (22)
77 (170)
ON
249 (4000)
1.7 (7)
1.0 (4)
46
40
9.5 (38)
460
60
5.95
B
132 (280,000)
52 (22)
88 (190)
ON
244 (4000)
1.5 (6)
0.7 (3)
1.0 (4)
20
35
480
60
6.02
C
141 (300,000)
56 (22)
77 (170)
ON
244 (4000)
1.7 (7)
0.7 (3)
50
55
460
60
5.93
D
160 (340,000)
56 (22)
64 (148)
ON
244 (4000)
1.7 (7)
2.0 (8)
2.0 (8)
75
7.0 (28)
400
60
5.80
E
150 (320,000)
56 (22)
82 (180)
ON
244 (4000)
2.0 (8)
1.5 (6)
2.0 (8)
50
82
400
60
5.98
F
141 (300,000)
56 (22)
71 (160)
ON
244 (4000)
1.7 (7)
2.7 (11)
2.0 (8)
94
100
440
32
5.90
G
141 (300,000)
56 (22)
88 (190)
ON
244 (4000)
2.0 (8)
2.0 (8)
2.0 (8)
100
100
5.90
u>
(Continued)
-------
(jj
NJ
Table 10. (Continued).
SulCite concentration
Ib/gal. (g/1)
Carbonate concentration
Ib/gal. (g/l)
SO. removal efficiency, »
Inlet ppm
Outlet ppm
0.45 (53.9)
0.88 (105.0)
76
4506
1068
0.31 (37.0)
0.71 (85.3)
81
4297
834
0.31 (37.4)
0.90 (108)
81
4663
892
0.49 (58.4)
0.63 (75.3)
82
4273
776
0.51 (61.6)
0.91 (109)
77
4982
1121
0.46 (54.7)
0.78 (93.1)
83
4156
704
0.54 (64.8)
0.80 (95.9)
81
4834
917
-------
START-UP AND SUBSEQUENT OPERATION: PROBLEMS AND SOLUTIONS
The start-up and ensuing operation of the FGD system at La
Cygne were accompanied by major problems. Solutions to these
problems were conceived and implemented primarily by utility
personnel as a result of continuing modification work and an
extensive preventive maintenance program. The major problem
areas and their respective solutions are discussed in the follow-
ing paragraphs.
Scale Formation
The buildup of a hard gypsum scale film inside the modules
has been a persistent problem since start-up. The primary areas
on which this scale forms are absorber internals, sieve trays,
the predemister sieve tray, mist eliminators, reheat tubes, and'
induced-draft fan blades.
To control scale, the utility instigated a program that
emphasizes regular cleaning and washing as well as fine control
of scrubbing solution chemistry and the use of specified con-
struction materials in areas prone to develop scale.
Each scrubber is cleaned and washed weekly (i.e., one module
is taken out of service nightly on a rotational basis). A
three-man crew works inside the scrubber module for 10 to 12
hours (from approximately 9 p.m. to 7 a.m.). They use large
amounts of fresh water to flush away scale accumulations and a
31-MPa (4500-psi) needle stream of water to clean the more
difficult spots. As a last resort, the hard gypsum scale is
chipped off manually, sometimes with sledge hammers.
The use of 316L stainless steel as the material of construc-
tion for the La Cygne scrubbers has also helped to prevent scale
buildup, especially in highly susceptible areas, since scale has
less tendency to adhere to the surfaces of equipment constructed
of 2.75 percent molybdenum bearing chromium-nickel stainless
steel.
33
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Corrosion
Corrosion has been a serious problem in reheaters, expansion
joints, induced-draft fans, breeching, and the carbon steel liner
of the stack. Serious corrosion problems have been combatted by
methods similar to those used to combat scale formation. Thoroughly
cleaning each module weekly virtually eliminates corrosion
throughout the system by minimizing the formation of crevices in
which acids and chlorides can concentrate and attack metal
surfaces. Corrosive attack in crevices can become especially
severe when dirty scrubbers circulate solution with a low pH and
a high chloride content.
The chloride content in the slurry at the point of discharge
of the bleed is 300 to 500 ppm. Pond water returned to the
process contains an average of 168 ppm of chlorides. These
concentration levels in conjunction with the 5.6- to 5.8- pH
range maintained in the scrubber provide an optimum performance
environment for the stainless steel components.
The use of compatible stainless steel components has been an
important factor in preventing severe corrosion. Type 316L
stainless steel was originally specified throughout the scrubber
system from a point just before the venturi throat through the
duct beyond the reheaters. The only exceptions were the fiber-
glass-reinforced polyester (FRP) chevron mist eliminators and the
Type 304 stainless steel reheater tubes. Extensive pitting
corrosion, some chloride stress corrosion cracking, and subse-
quent mechanical failure around the tube supports occurred in the
original steam tubes. To rectify this problem all the reheat
tube bundles that failed were replaced with sturdier ones con-
structed of Type 316L stainless steel. The sturdier design has
reduced the likelihood of mechanical failure at the supports and
provided a stronger support platform for the cleaning crew.
Also, when a module is taken out of service for cleaning and
repairs, steam flow continues through the tubes, thereby keeping
the surface temperature above the acid dew point until thorough
flushing has been completed.
34
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Scale carryover to the induced-draft fans can provide areas
and crevices that foster corrosive attack. To resist the effects
of acid corrosion, various epoxy paints are applied to the fans
every 8 to 10 months. The utility is also initiating a program
to protect those areas and mating surfaces most affected by acid
runs by cladding them with Inconel 625 stainless steel. Serious
corrosion is also a problem in the breeching from the fans to the
stack and in the carbon steel liner of the stack. These latter
areas have also been coated with an epoxy paint (Plasite 4005)
that resists corrosion and erosion.
Plugging
Plugging in the La Cygne modules occurs as deposition of
soft solids on the internals. These soft solids originate from
three different sources: fly ash, calcium carbonate, and calcium
sulfite. Calcium sulfite forms what is commonly known as soft
scale. Soft scale tends to accumulate rapidly when the pH of the
scrubbing solution exceeds the control level (5.6 to 5.8) and
enters the alkaline range. This results in the precipitation of
large leaf-like masses of calcium sulfite on the internals.
Because this material is soft and easily altered mechanically, it
provides deposition areas for the calcium carbonate and fly ash
material in the scrubbing solution. High calcium carbonate
concentrations in the scrubbing solution result from the high
stoichiometric feed rate of lijmestone slurry.
Areas that have been susceptible to plugging are sieve
trays, walls, predemister sieve trays, mist eliminators, reheater
tubes, and induced-draft fan blades. Freshwater sprays are used
to remove accumulations of soft deposits from module internals.
Erosion
The venturi throat and the sump floor immediately below the
venturi are areas within the modules that are susceptible to wear
and abrasion. To protect these areas, silicon-carbide brick and
cementitious coating are applied to the stainless steel.
35
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Erosion has also been detected on the stainless steel
slurry nozzles and the carbon steel coated induced-draft fans.
Another preventive measure involves rubber-lining the
process piping network to protect the carbon steel base from
abrasive slurry. This has been generally successful, although
there have been a few reported incidents of wear in the area of
the spent slurry valves. This wear was attributed to the throt-
tling action of the valve to modulate the flow of slurry. The
problem was solved by operating the valve only in a completely
open or completely closed position.
Mechanical Failures
Several miscellaneous mechanical problems have occurred
during FGD operations. The major problems are described briefly
in the following paragraphs.
The rubber lining in venturi pumps on the circulation tanks
has been damaged many times, primarily because of frequent
plugging of the strainer at the suction end of the pump. As
plugging causes the flow to cease or to be drastically reduced,
the pump cavitates and the liner is sucked into the path of the
impeller and shredded. The suction strainers were located
inside the recirculation tank, and the tank had to be drained to
clean them. Installation of a hydroclone in the recirculation
line of each module for the purpose of extending the life of the
limestone slurry spray nozzles on the venturi scrubber and
reducing wear and erosion in the slurry recirculation loop
solved pump problems as well. The hydroclone separates the
larger particles of scale from the main slurry steam by means of
centrifugal action. This made the strainer unnecessary- and its
removal eliminated plugging problems.
The mist eliminators and gas reheater tubes have been
susceptible to heavy scaling and plugging. Droplets of slurry
are carried over with the flue gas and deposited on the mist
eliminators, which are made of Z-shaped fiberglass boards. As
the slurry builds up, the gas flow is restricted and its velocity
36
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through the mist eliminator increases, causing solids carryover
and deposition on the reheater tubes. Some slurry carryover also
reaches the induced-draft fan and is deposited on the fan blades.
These interrelated problems of carryover to the mist elim-
inator, the reheater, and the induced-draft fan have necessitated
many modifications to equipment and corrections in operating
procedures. A continuous overspray now keeps the mist eliminators
clean. The steam soot blower has been modified so that it is
reasonably successful in maintaining the reheaters, thereby
greatly reducing the need for fan washing.
Another modification involved replacing 304 stainless steel
reheater tubes with 316L stainless steel tubes. The rapid
corrosion of the former material prompted the utility to install
hot air headers and inject a slip stream of hot combustion gas
into the saturated flue gas upstream of the reheater. This
additional reheat load was required to raise the temperature
above the acid dew point at which the 304 stainless steel bundles
were susceptible to attack [88° to 93°C (190 to 200°F)]. Form-
erly, 17 to 20 percent of the reheat was provided in this manner.
This procedure has been reduced because of the sturdier 316L
stainless steel bundles and also because most of the entire hot
combustion air stream is required for full-load capacity operation.
Problems have occurred with the induced-draft fans since
these units were first balanced in September 1972. Initially the
fans were sensitive to imbalance, and severe vibration in the fan
housing resulted from the fans operating close to the critical
speed. The vibration caused cracks in the inlet cones, and
additional stiffeners had to be installed to strengthen the
housing. •
Another problem involved high running temperatures of the
thrust collars on the fan bearings, which reached the 180°F alarm
set point within a short time after the fans were started.
Examination of the bearings revealed that the thrust collars were
not stable and their movement attributed to air turbulence
37
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in the inlet ductwork, causing the rotor to shift from side to
side. Several aerodynamic configurations were tried to eliminate
this air turbulence. A splitter foil and directional vanes were
installed in the duct and in the fan inlet box, but the thrust
collars continued to overheat and to move during operation. The
temperature was finally controlled by cutting oil grooves in the
thrust collar and installing forced-lubrication systems on all
the fans. These modifications effected a decrease in the thrust
collar temperature to a range of 140° to 160°F. Movement of the
thrust collars were checked by installing split backup collars
designed to give an interference fit.
Problems with the induced-draft fan began with the initial
firing of the boiler. Fly ash and slurry carried over from the
scrubber and deposited on the blades of the impeller aggravated
the tendency of the fan to be out of balance and promoted fan
blade erosion. (One blade was nearly destroyed by erosion.)
Examination of all the blades by magnaflux revealed several
cracks, indicating the need for reinforcement. By June 1974 all
I.D. fan rotors had been replaced with units of heavier design.
Shaft diameter was increased from 51 to 61 cm (20 to 24 in.).
Radial tip blades and side plates of the wheels are 1.6 cm (5/8
in.) thick instead of 0.64 cm (1/4 in.). The thick center plate
was scalloped to hold down the weight, and the critical frequency
was moved farther away from the operating speed to reduce the
tendency to vibrate. The leading edge of each blade was covered
with a stainless steel clip to deter erosion. Although fly ash
carry-over still requires intermittent washing of the fans, the
cleaning frequency is being steadily reduced.
Fly ash carry-over has also caused erosion of the inlet and
outlet dampers of the induced draft fans. Metal on the dampers
has been rewelded or replaced several times. Deposits have
interferred with operation to the extent that dampers have bound
and pins have sheared. Seal air has been provided to keep the
bearings clean.
Limestone and coal are stored separately in two adjacent
38
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piles. A single conveying system was used to transport both
materials to the boiler on a time-sharing basis. Most of the
problems created by this arrangement were logistic. However, the
size of the fines had to be increased to 5 x 0.3 cm (2 x 1/8 in.)
because fines of proper size, 2 x 0 cm (3/4 x 0 in.), clogged the
delivery chutes. This created other problems in that the steel
balls in the mills were not large enough to properly grind the
larger fines. This resulted in a limestone slurry of undesirable
consistency. The addition of a separate limestone delivery
system has since alleviated these problems.
The quality of the limestone shipped to the plant was also a
source of some concern. The presence of large amounts of gangue
and other foreign matter resulted in occasional plugging of the
limestone feed nozzles. To correct this, the utility installed
catch buckets to filter out larger inert materials from the
limestone before it enters the preparation tanks.
The limestone for the FGD system comes from a local quarry.
Two different grades come from the same quarry, a top cut and a
lower cut. The top cut, which is off-white to brownish, has a
high content of iron oxides and grinds easily. The lower cut,
which is gray to white, is more difficult to grind. Because of
the different physical and chemical properties, each requires
different process control ranges to maintain optimum utilization
and minimize scaling and corrosion.
Since initial start-up of the system, spray nozzle arrange-
ment in the scrubber modules has been a source of many problems,
including plugging and poor spray distribution. The utility is
now attempting to recitify these problems by installing ceramic
spinner-vane spray nozzles.
SYSTEM ECONOMICS
The total cost of the La Cygne emission control system to
date amounts to approximately 22 percent of the total plant cost
of $213.5 million.. This translates into an installed value of
$46.8 million or $59/kW. The utility invested an additional $7
39
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million to achieve optimum system performance, $5.2 million of
which covers the installation of the eighth scrubber module. In
1977 energy costs for Unit 1 averaged 8.23 mills/kWh. Approx-
imately 21 percent of this total was devoted to the emission
control system, including the purchase and preparation of the
limestone and the operation and maintenance of the system hardware.
Unit 2, a 630-MW coal-fired power generator, was placed in
commercial service in May 1977. This unit burns low-sulfur (0.48
percent) Wyoming coal supplied by Amax Coal Company mines in the
Gillette area. Compliance with new source performance standards
for SO- does not require FGD, but an ESP is used to control
particulate emissions. The strategy for Unit 2 was developed
along different lines from that for Unit 1 because of coal supply
commitments. The coal supplied for the boiler in Unit 1 originates
from nearby surface mines operated by the Pittsburgh & Midway
Coal Mining Company. Total deposits are estimated to be 64 Tg
(70 million tons), which is sufficient to supply the fuel needs
of the unit over its designed 30-year life span. Because local
coal could not be obtained for Unit 2, the utility negotiated a
long-term commitment for rail delivery of low-sulfur Wyoming
coal, which the boiler will burn at a rate of 1.8 million Mg (2
million tons) per year.
Tables 11 and 12 present operating and capital costs for the
La Cygne Unit 1 scrubbing system. FGD operating and maintenance
costs cover approximately 4 years of operation following commer-
cial start-up. Capital cost figures include unit allocations and
coal and limestone costs.
40
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Table 11. FGD OPERATING COSTS, LA CYGNE UNIT 1, JUNE 1973 TO SEPTEMBER 1977
Description
Operating
labor
Operating
materials
Maintenance
labor
Maintenance
materials
Limestone
Total
1973 operation3
dollars
162,934
3,460
189,400
441,737
264,51,4
1,062,065
mills/kWh
0.233
0.005
0.259
0.604
0.362
1.453
1974 operation13
dollars
284,541
67,032
401,414
335,486
780,297
1,868,770
mills/kHh
0.223
0.053
0.315
0.263
0.613
1.467
1975 01
dollars
601,029
195,926
416,206
366,397
1,256,043
2,685,606
Deration0
mills/kHh
0.265
0.086
0.184
0.171
0.554
1.260
1976 operation*3
dollars
683,939
415,226
358,941
93,292
1,717,949
3,269,347
mills/kHh
0.229
0.139
0.129
0.574
0.574
1.102
1977 operation6
dollars
524,409
189.945
363,159
947,000
1,013,717
3,038,230
mills/kHh
0.292
0.106
0.202
0.528
0.565
1.693
1973 operation figures include operation from full commercial start-up on June 1 to December 31.
1974 operation figures are based upon a 23 percent unit capacity factor.
1975 operation figures are based upon a 32 percent unit capacity factor.
1976 operation figures are based upon a 44 percent unit capacity factor.
1977 operation figures include only the first 9 months of operation. Unit capacity factor for this period was 44
percent.
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Table 12. TOTAL CAPITAL COSTS FOR THE LA CYGNE UNIT 1
POWER GENERATING UNIT AND FGD FACILITY
Description
Capital costs (1977 dollars)
Total
$/kW
Power generation facility
Scrubbing facility
Total plant costs
Capital cost basis:
Coal: $ll,919/Mg ($10.813/ton)
$0.56/GJ ($0.535/106 Btu)
2.2 GG/year
2.4 x 106
tons/year) usage
166,586,000
46,861,000
213,447,000
208
59
267
Limestone:
$3.381/Mg
($3.068/ton)
454 Mg/year
(500,000 tons/year) usage
Unit rating: 820 MW, net
42
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APPENDIX A
PLANT SURVEY FORM
A. Company and Plant Information
1. Company name; Kansas City Power and Light (KCP&L)
2. Main office; Kansas City, Missouri
3. Plant name; La Cygne Station
4. Plant location; La Cygne/ Kansas (Linn County)
5. Responsible officer; Mr. Trask
6. Plant manager; Charles Ryan
7. Plant contact: Cliff McDaniel
8. Position; Superintendent of scrubbing operations
9. Telephone number; 913/757-4451
10. Date information gathered; June 23, 1976
Participants in meeting Affiliation
Cliff McDaniel KCP&L
Rav Cain KCP&L
G.A'. Isaacs PEDCo Environmental, Inc,
B.A. Laseke PEDCo Environmental, Inc,
TtC. Ponder PEDCo Environmental. Inc,
PEDCo Environmental, Inc,
43
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B. Plant and Site Data
1. UTM coordinates:
2. Sea Level elevation:
3. Plant site plot plant (Yes, No); NO
(include drawing or aerial overviews)
4. FGD system plan (yes, No); No
5. General description of plant environs; Flat, rural, no
manor industry in the area
6. Coal shipment mode; Coal is delivered to the plant in
off-the-road 108-Mg (120-ton) trucks from nearby
surface mines operated by the Pittsburgh & Midway Coal
Mining Company.
C. FGD Vendor/Designer Background
1. Process name: Wet limestone
2. Developer/licensor name; Babcock & Wilcox
3. • Address: Power Generation Group, 20 S. Van Buren Ave.,
Barberton, Ohio
4. Company offering process:
Company name; Babcock & Wilcox
Address: 20 S. Van Buren Avenue
44
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Location; Barberton, Ohio
Company contact: Jack Stewart
Position: Sales Manager
Telephone number; (216) 753-4511
5. Architectural/engineers name:
Address:
Location:
Company contact:
Position:
Telephone number:
D. Boiler Data
1. Boiler; La Cygne Unit 1
2. Boiler manufacturer; pabcock & Wilcox
3. Boiler service (base, standby, floating, peak):
Base load: Maximum continuous generating capacity for
two-thirds of a service day; two-thirds capacity during
the remainder of the service day.
4. Year boiler placed in service; 1973
5. Total hours operation: 19,000 hr (approximate to Nov.
1977)
6. . Remaining life of unit:
Dry bottom, pulverized-coal, cyclone-
7. Boiler type; fired, supercritical, once-through
balanced-draft
8. Served by stack no.; One
9. .Stack height; 200 m (700 ft)
10. Stack top inner diameter:_
11. Unit ratings (MW):
Gross unit rating; 874 MW
Net unit rating without FGD; 844 MW
45
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Net unit rating with FGD; 820 MW
Name plate rating; 874 MW
12. Unit heat rate; 11/400 kJ/kWh )10,800 Btu/kWh)
Heat rate without FGD: N/A
Heat rate with FGD; 11,400 kJ/kWh (10,800 Btu/kWh)
13. Boiler capacity factor, (1976); 57%
14. Fuel type (coal or oil); Coal
15. Flue gas flow:
Maximum: 1,297 m /sec (2,760,000 acfm)
Temperature: 140°C (285°F)
16. Total excess air: 18-20%
17. Boiler efficiency:
E. Coal Data
1. Coal supplier:
Name: Pittsburgh & Midway Coal Mining Co.
Location: Linn County. La Cvane. Kansas
Mine location: La Cygne - 3.2 km (2 miles) from plant
County, State; Linn County, Kansas
Seam:
2. Gross heating value; 21-23 MJ/kg (9000-9700 Btu/lb)
3. Ash (dry basis); 24-25%
4. Sulfur (dry basis): 5-6%
5. Total moisture: 9-10%
6. Chloride: Q.02-0.03%
7. Ash composition (See Table A2)
8. Coal Analysis: (See Comments, Section M)
-Not Applicable
46
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Table A2. ASH COMPOSITION
Constituent Percent weight
Silica, Si02 46.05
Alumina, A1203 14.07
Titania, TiO2 1.02
Ferric oxide, Fe-O- 19.23
Calcium oxide, CaO 6.86
Magnesium oxide, MgO 1.02
Sodium oxide, Na_0 0.60
Potassium oxide, K2O 2.48
Phosphorous pentoxide, P2°5 0.15
Sulfur trioxide, SO- 7.85
Other 0.67
Undetermined
F. Atmospheric Emission Regulations [Data given in ng/J (lb/10 Btu)]
1. Applicable particulate emission regulation
a) Current requirement; 56 (0.128)
AQCR priority classification; III
Kansas Air Pollution Emission
Regulation and section No.; Control Regulation 28-19-31A
b) Future requirement (Date: ):
Regulation and section No.:
2. Applicable SO- emission regulation
a) Current requirement: 640 (1.5)*
AQCR Priority Classification; m
Kansas Air Pollution Emission
Regulation and section NO. t Contrnl Ttepnlatinn 23-1Q-3lr!
b) Future requirement (Date: )
* Sulfur emission regulation limitation. Boiler installed
prior to Federal NSPS - subject to Kansas Dept. of Health
regulation.
47
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Regulation and section No.:
G. Chemical Additives; (Includes all reagent additives -
absorbents, precipitants, flocculants, coagulants, pH
adjusters, fixatives, catalysts, etc.)
1. Trade name: Limestone
Principal ingredient; CaCOi (85-93%)
Function: Scrubbing reagent
Source/manufacturer: Bates City Rock Co.
Quantity employed; 454 Mq/yr (500,000 tons/yr)
Point of addition; Milling system
2. Trade name: Lime
Principal ingredient; CaO
Function: Emergency p^H control additive
Source/manufacturer: _^_______^_____
Quantity employed; Emergency only - has never been required
Point of addition; Recirculation tanks _
3. Trade name ; N/A _
Principal ingredient: _
Function : _ _
Source/manufacturer : _
Quantity employed: _
Point of addition : ___ ___ _
4. Trade name;
Principal ingredient:
Function:
Source/manufacturer:
Quantity employed:
48
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Point of addition:
5. Trade name: N/A
Principal ingredient:
Function:
Source/manufacturer:
Quantity employed:
Point of addition:
H. Equipment Specifications
1. Electrostatic precipitator(s) N/A
Number: None
Manufacturer:
Particulate removal efficiency:
Outlet temperature:
Pressure drop:
2. Mechanical collector(s) N/A
Number: None
Type:
Size:
Manufacturer:
Particulate removal efficiency:
Pressure drop:
3. Particulate scrubber(s)
Number: Eight, one per scrubbing train
Type; Variable-throat VRnturi
Manufacturer: Babcock & Wilcox
Dimensions; 6.6 m x 56 cm (21.5 ft x 22 in.)
49
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Material, shell: 316LSS
Material, shell lining; Kaocrete ceramic
Material, internals: None
No. of modules; One per scrubbing train, eight total
No. of stages: One
Nozzle type; Coors ceramic spinner vane
Nozzle size:
No. of nozzles; 48 spray and 32 wall wash
Boiler load; 100% for all 8
Scrubber gas flow; 160 m3/sec @ 141°C (345.000 acfm @ 285°f)
(design value)
Liquid recirculation rate; 238 I/sec (5000 gpm)
Modulation: None
L/G ratio; i.g i/m3 .(12 gal./lOQQ acf)
Scrubber pressure drop; 1.7 kPa (7 in H?0)
Modulation: None (see Comments, Section M)
Superficial gas velocity;. 39.6 m/sec (130 ft/sec)
Particulate removal efficiency; 98.2%
Inlet loading; 4250 na/J (9.9 lb/106 Btu)
Outlet loading: See SOo absorber, item No. 4
SO- removal efficiency: Unknown
Inlet concentration: 4500
Outlet concentration: See SO? absorber, item No. 4
4. SOg absorber(s)
Number: Eight, one per scrubbing train
Types .Two-stage sieve tray absorber
Manufacturer: Babcock & Wilcox
50
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Dimensions; 9.7 x 4.9 x 19.8 m (32 x 16 x 65 ft)
Material, shell: 316L SS
Material, shell lining; None
Material, internals: 316L SS sieve trays
No. of modules; One per scrubbing train, eight total
No. of stages:_2_
Packing type; N/A
Packing thickness/stage: N/A
Nozzle type; Coors ceramic spinner vane
Nozzle size; 1.9 cm (0.75 in.)
No. of nozzles: 16
Boiler load; 100% for all 8 absorbers
Absorber gas flow: H2 m3/sec @ 50°C (238.500 acfm @ 122°F)
(design value)
Liquid recirculation rate; 500 i/sec (9000 gpm)
Modulation:
L/G ratio; 3.5 m3/sec (26.5 gal/1000 acf)
Absorber pressure drop; 1.5 kPa (6 in. H->O)
Modulation: None
Superficial gas velocity; 4.6 m/sec (15 ft/sec)
See particulate
Particulate removal efficiency; scrubber. Item No. 3
Inlet loading: See particulate scrubber. Item No. 3
Outlet loading; 77 na/J fQ.13 lb/106 Btu)
SO, removal efficiency: 80% .
Inlet concentration: See particulate scrubber. Item No. 3
Outlet concentration; 1000 ppm
51
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5. Predemister
Number: Eight, one per scrubbing train
Type: Sieve tray, 3.5-cm (1.375-in.) diameter holes
Materials of construction: 316L SS
Pressure drop; 0.3 kPa (1.2 in. H2O)
Source of water:
6. Mist eliminator(s) (Eight, one per scrubbing train)
Number:
Type: chevron
Materials of construction; FRP fDurakane)
Manufacturer: B&W
Configuration (horizontal/vertical); Horizontal
Distance between scrubber bed and mist eliminator:
3.6 m (12 ft)
Mist eliminator depth; 26.2 cm (10.3 in.) per stage
Vane spacing; 7.6 cm (3 in.)
Vane angles; 45°
Type and location of wash system; Continuous blended pond
water overspray [14.5 I/sec (230 gpm) 1
Superficial gas velocity; 2.6 m/sec (8.4 ft/sec)
Pressure drop; 5Q pa (012 in. H20)
Comments: Three of the eight modules currently have two-
T^f'-v
stage, three-pass mist eliminators, the remaining five
have one-sjiage. j-.hree-pass. uni-hs.
7. Reheater(s): 1 per scrubbing train, 8 total
Type (check appropriate category):
52
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(x] in-line
[x] indirect hot air
O direct combustion
[~] bypass
Q exit gas recirculation
Q waste heat recovery
D other
Gas conditions for reheat: (per module)
Flow rate; 145 m3/sec (307.500
Temperature : i22°F
SO2 concentration; IQQQ ppm
Heating medium; Extraction steam
Combustion fuel: N/A
Percent of gas bypassed for reheat: N/A
Temperature boost (AT): 28°C (50°F)
Energy required: 0.65% of boiler input
Comments: The reheaters are stainless steel bare tubes
which convey 0.96 kg/sec (7600 Ib/hr) of 965 kPa (140
psig) 365°C (690°F) extraction steam.
8. Fan(s) (9 fans total)
Type: 3 forced-draft (FD) fans. 6 induced-draft (ID)
booster fans
Materials of construction:
Manufacturer: Green Fuel Economizer Co. and Stmrt-mian+ Co,
Location; 3 FD fans with boiler: 6 ID fans dnwnst-rgam nf
reheaters
Fan/motor speed:__
Motor/brake power; 5250 w (7QQQ hp)
53
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9.
Variable speed drive:
Tank(s)
Function
Limestone slurry
stage
Slurry
recirculation
Number
2
8
Dimensions
11 m * x 8 m
(36 ft « x 26 ft)
9 m 4 x 7 m
(30 ft 4 X 24 ft)
Capacity
450,000 1
(200,000 gal.)
440,000 1
(116,000 gal.)
Retention
time
120 min
8 min
Materials of
construction
Rubber-lined
carbon steel
Rubber-lined
carbon steel
10. Recirculation/slurry pump(s)
Function
Venturi
recirculation
Absorber
recirculation
Number
8
8
8
Manufacturer
A-S-H
A-S-H
A-S-H
Type
Rubber
lined
Rubber
lined
Capacity
315 I/sec
(5000 gpm)
(9000 gpm)
Motor
260 kW
C350 hp)
300 kW
(400 hp)
11.
Thickener(s)/clarifier(s) N/A
Number:
Type:
Manufacturer:
Materials of construction:
Configuration:
Diameter:
Depth:
Rake speed:
12. Vacuum filter(s) N/A
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Number:
Type:
Manufacturer:
Materials of construction:
Belt cloth material:
Design capacity:
Filter area:
13. Centrifuge(s) N/A
Number:
Type:
Manufacturer:
Materials of construction:
Size/dimensions:
Capac ity:
14. Interim sludge pond(s)
Number: One
Description: Settling pond equipped with overflow weirs
2
Area: 0.65 km (160 acres)
Depth: 3.0-3.5 m (10-12 ft)
Liner type; None ; __
Location: Plant grounds
Typical operating schedule; Clarified solution overflows
into larger settling pond
Ground water/surface water monitors:
15. Final disposal site(s)
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Number:
Description:
Area:
Depth:
Location:
Transportation mode; Pipe
Typical operating schedule; Continuous
16. Raw materials production
Type; Limestone ball mills
Number: Two
Manufacturer: Koppers
Capacity: 28 kg/sec (110 tons/hr)
Product characteristics; Limestone rock .ground.... to a
firmness of 95% minus 200 mesh at 66% solids befgre
slurried
I. Equipment Operation, Maintenance, and Overhaul Schedule
1. Scrubber(s)
Design life; Life span of unit
Elapsed operation time; 20,000 hr (approximate)
Cleanout method: Manual: 3-man maintenance view
Cleanout frequency: One module nightly/once per week
Cleanout duration: 8-10 hr
Other preventive maintenance procedures:
2. Absorber(s)
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Design life; Life span of unit
Elapsed operation time; 20.000 hr f approximate)
Cleanout method: Manual;
Cleanout frequency; One module nightly /once per week
Cleanout duration: 8-10
Other preventive maintenance procedures:
3. Reheater(s)
Design life; 1-2 years
Elapsed operation time:
Cleanout method; Soot blowers
Cleanout frequency:
Cleanout duration:
Other preventive maintenance procedures; Cleaned during
manual preventive maintenance, one module once per week
4. Scrubber fan(s) (Same as scrubbers and absorbers)
Design life:
Elapsed operation time:
Cleanout method:
Cleanout frequency:
Cleanout duration:
-Other preventive maintenance procedures:
5. Mist eliminator(s) (Same as scrubbers and absorbers)
Design life:
Elapsed operation time;
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Cleanout method:
Cleanout frequency:
Cleanout duration:
Other preventive maintenance procedures:
6. Pump(s) (Same as scrubbers and absorbers)
Design life:
Elapsed operation time:
Cleanout method:
Cleanout frequency:
Cleanout duration:
Other preventive maintenance procedures:
7. Vacuum filter(s)/centrifuge(s) N/A
Design life:
Elapsed operation time:
Cleanout method:
Cleanout frequency:
Cleanout duration:
Other preventive maintenance procedures;
8. Sludge disposal pond(s)
Design life:
Elapsed operation time:
Capacity consumed:
Remaining capacity:
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Cleanout procedures:
J. Cost Data
1. Total installed capital cost; $46.8 MM ($59/kW)
2. Annualized operating cost; $3.038 MM (1.693 mills/kWh)
3. Cost analysis (see breakdown: Table A2) see comments (below)
4. Unit costs
a. Electricity;
b. Water;
c. Steam:_
d. Fuel (reheating/FGD process):
e. Fixation cost:
f. Raw material:
g. Labor:
Comments: Details on the total installed capital and
operating costs, for La Cygne No. 1 are provided in the
text of the report (see Section 4, System Economics,
and Tables 13 and 14)
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Table A2. COST BREAKDOWN
Cost elements
A. Capital Costs
Scrubber modules
Reagent separation
facilities
Waste treatment and
disposal pond
By -product handling
and storage
Site improvements
Land, roads, tracks,
substation
Engineering costs
Contractors fee
Interest on capital
during construction
B. Annualized Operating
Cost
Fixed Costs
Interest on capital
Depreciation
Insurance and taxes
Labor cost including
overhead
Variable costs
Raw material
Utilities
Maintenance
Included in
cost estimate
Yes
cm
en
cm
cm
im
cm
cm
cm
cm
cm
cm
Cm
•cm
im
cm
cm
No
im
cm
cm
cm
im
C=J
cm
cm
cm
im
dD
Cm
cm
cm
Estimated amount
or % of total
capital cost
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K. Instrumentation
A brief description of the control mechanism or method of
measurement for each of the following process parameters:
Reagent addition:
0 Liquor solids content:
e Liquor dissolved solids content:
9 Liquor ion concentrations
Chloride:
Calcium:
Magnesium:
Sodium:
Sulfite:
Sulfate:
Carbonate:
Other (specify):
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Liquor alkalinity:
Liquor pH:
Liquor flow:
Pollutant (SO», particulate, NO ) concentration in
£* • X
flue gas:
0 Gas flow:
Waste water
Waste solids:
Provide a diagram or drawing of the scrubber/absorber train
that illustrates the function and location of the components
of the scrubber/absorber control system.
Remarks: A thorough discussion of the instrumentation and
and process control network for the La Cygne scrubbing
system is provided in Section 3 (see Process Control)
L. Discussion of Major Problem Areas: see text - Start-up and
and Subsequent Operation: Problems and Solutions
1. Corrosion; Some
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2. Erosion: Some
3. Scaling; See text - Start-up and Subsequent Operation:
Problems and Solutions
4. Plugging; See text - Start-up and Subsequent Operation:
Problems and Solutions
5. Design problems; See text - Start-up and Subsequent
• Operation: Problems and Solutions
6. Waste water/solids disposal: See text - Start-up and
Subsequent Operation; Problems and Solutions
-------
7. Mechanical problems:
M.
General comments:
1. La Cygne coal proximate and ultimate analysis:
Proximate
Volatile
Fixed carbon
Ash
Moisture
Heat content, MJ/kg
(Btu/lb) 22
Grindability
28.63
37.94
24.36
9.07
100.00
(9421)
59.59
Ultimate
Moisture
Carbon
Hydrogen
Nitrogen
Chlorine
Sulfur
Ash
Oxygen
8.60
51.93
3.43
0.94
0.02
5.39
24.36
5.33
100.00
2. The venturi scrubbers are maintained at widest- opening
with no modulation; the eighth module includes a fixed
throat venturi.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1 REPORT NO.
EPA-600/7-78-048d
3. RECIPIENT'S ACCESSION NO.
4 .TITLE AND SUBTITLE Survey of Flue Gas Desulfurization
Systems: La Cygne Station, Kansas City Power and
Light Co.
5. REPORT DATE
March 1978
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Bernard A. Las eke, Jr.
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
PEDCo Environmental, Inc.
11499 Chester Road
Cincinnati, Ohio 45246
10. PROGRAM ELEMENT NO.
EHE624
11. CONTRACT/GRANT NO.
68-01-4147, TaskS
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 COVERED
Subtask Final; 1-6/77
14. SPONSORING AGENCY CODE
EPA/600/13
15. SUPPLEMENTARY NOTES ffiRL-RTP project officer is Norman Kaplan, Mail Drop 61, 919/
541-2556. Report EPA-650/2-75-057b gives first survey results.
16. ABSTRACT
The report gives results of a second survey of the flue gas desulfurization
(FGD) system on Unit 1 of Kansas City Power and Light Co. 's La Cygne Station. The
FGD system, first started up in February 1973 and commercially available in June
1973, utilizes a limestone slurry in eight scrubbing modules to control fly ash and
SO2 from the combustion of high sulfur subbituminous coal. Each module includes
a venturi scrubber, sump, and two-stage sieve tray absorber. All the flue gas is
treated: it cannot bypass the scrubbing modules. Facilities for limestone grinding
and storage and final disposal of the flue gas cleaning wastes are on the plant
grounds. Clear water is recycled from the pond to the FGD system for additional
use. SO2 and particulate removal efficiency measurements indicate that the design
values of 80 and 98.75%, respectively, have been met or exceeded.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Air Pollution
Flue Gases
Desulfurization
Fly Ash
Limestone
Slurries
Ponds
Scrubbers
Coal
Combustion
Cost Engineering
Sulfur Dioxide
Dust Control
Air Pollution Control
Stationary Sources
Wet Limestone
Particulate
13B
21B
07A,07D
11G
08H
21D
14A
07B
13. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
>1. NO. OF PAGES
74
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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