&EPA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
EPA-600/7-79-221b
September 1979
Full-Scale Dual-Alkali
Demonstration System
at Louisville Gas and
Electric Co. — Final Design
and System Cost
Interagency
Energy/Environment
R&D 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-600/7-79-221b
September 1979
Full-Scale Dual -Alkali Demonstration System
at Louisville Gas and Electric Co. — Final
Design and System Cost
by
R.P. VanNess, R.C. Somers, R.C. Weeks (LG&E);
T. Frank, G.J. Ramans (CEA);
C.R. LaMantia, R.R. Lunt, and J.A. Valencia (ADL)
Louisville Gas and Electric Company
311 W. Chestnut St.
Louisville, KY 40201
Contract No. 68-02-2189
Program Element No. EHE624A
EPA Project Officer: Norman Kaplan
Industrial Environmental Research Laboratory
Office of Environmental Engineering and Technology
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
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ABSTRACT
The dual alkali process developed by Combustion Equipment Associates, Inc.
(CEA) and Arthur D. Little, Inc. (ADL) has been installed in Unit No. 6,
a coal-fired boiler at Louisville Gas and Electric Company (LG&E) Cane Run
Station for controlling SOo emissions. The Federal Environmental Protec-
tion Agency (EPA) has selected this system as the demonstration plant for
dual alkali technology and is participating in funding of the operation,
testing, and reporting of the project.
The project consists of four phases: Phase I - preliminary design and
cost estimation; Phase II - engineering design, construction, and mechani-
cal testing; Phase III - startup and performance testing; and Phase IV -
one year operation and test programs.
This report covers the work in Phase II of the program including: the
final engineering design; construction and mechanical testing; and installed
capital cost for the system. Construction of the system was completed in
February 1979 and system startup was initiated in March 1979.
iii
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CONTENTS
Abstract
List of Figures
List of Tables
Applicable Conversion Factors
English to Metric Units
Acknowledgement s
I. SUMMARY
A. Overall Purpose and Scope
B. CEA/ADL Dual Alkali System
C. Capital Investment
II. INTRODUCTION
A. Purpose of Project
B. Scope of Work
C. Project Schedule
III. CEA/ADL DUAL ALKALI PROCESS TECHNOLOGY
A. Process Chemistry
B. Pollution Control Capabilities
IV. DESCRIPTION OF THE DUAL ALKALI PROCESS APPLICATION
AT THE CANE RUN STATION
A. Boiler System Description
B. Design Conditions for the Dual Alkali System
C. Guarantees
D. Process Description
E. Material Balances
F. Operating and Control Philosophy
Page No.
iii
vii
viii
x
xi
1
1
2
3
6
6
6
8
11
11
17
19
19
19
22
24
33
«
41
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CONTENTS (Continued)
Page N
V. DUAL ALKALI PLANT CONFIGURATION AND
EQUIPMENT SPECIFICATIONS 54
A. Plant Layout 54
B. Process Equipment 54
C. Offsites and Auxiliaries 60
D. Mechanical Testing of Equipment 64
VI. CAPITAL COSTS FOR THE DUAL ALKALI SYSTEM
AT THE CANE RUN STATION 68
A. FGD System 68
B. Lime Slurry Feed 73
C. Waste Disposal 73
VII. GLOSSARY 74
APPENDIX - EQUIPMENT DETAILS
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FIGURES
Figure No. Page No.
II-l Dual Alkali Demonstration Overall Project
Schedule 9
II-2 Phase II Schedule 10
III-l Dual Alkali Process Flow Diagram 13
V-l Overall View of Cane Run Unit No. 6
and the Dual Alkali System 55
V-2 Gas Reheaters and Absorber Ducting 56
V-3 Overall View of the Chemical Plant 57
DRAWINGS
Process Flow Diagram 040044-1-1, Rev. G
Process Flow Diagram 040044-1-2, Rev. G
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TABLES
Table No. Page No.
1-1 Capital Costs for the Dual Alkali System
at LG&E's Cane Run Unit No. 6 5
IV-1 Ultimate Analysis of Coal Fired in Unit
No. 6 20
IV-2 Design Basis 21
IV-3 Flue Gas Conditions at the Inlet of the
Dual Alkali System 23
IV-4 Carbide Lime Specifications 31
IV-5 Basis for Material Balances at Design
Conditions 34
IV-6 Overall Material Balance at Design Conditions 35
IV-7 Overall Water Balance at Design Conditions 36
IV-8 Material Balance - Absorber Section 38
IV-9 Material Balance - Reactor, Solids Dewatering
and Raw Materials Section 39
IV-10 Control Philosophy for the Absorber Section 43
IV-11 Control Philosophy for the Reactor Section 46
IV-12 Control Philosophy for the Solids Separation
Section 49
IV-13 Control Philosophy for the Raw Materials
Section 52
V-l Ancillary Requirements for the Dual Alkali
System at LG&E Cane Run Unit No. 6 62
VI-1 Capital Costs for the Dual Alkali System
at Cane Run Unit No. 6 59
VI-2 Capital Cost Breakdown by Sub-System 70
VI-3 Material Costs for the FGD System - Process
Materials 71
VI-4 Material Costs for the FGD System - Additional
Materials 72
viii
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TABLES (Continued)
Table No. Page No.
A-l Equipment List A-l
A-2 Materials of Construction A-4
A-3 Agitators A-7
A-4 Dampers A-8
A-5 Ductwork A-9
A-6 Expansion Joints A-10
A-7 Booster Fans A-ll
A-8 Reheaters A-12
A-9 Pumps A-l3
A-10 Tanks A-14
A-ll Soda Ash Silo A-15
A-12 Thickener A-16
A-13 Vacuum Filter A-17
A-14 Absorber A-18
ix
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APPLICABLE CONVERSION FACTORS
ENGLISH TO METRIC UNITS
British
5/9 (°F-32)
1 ft
1 ft2
1 ft3
1 grain
1 in
lin2
lin3
1 Ib (avoir.)
1 ton (long)
1 ton (short)
1 gal
1 Btu
Metric
°C
0.3048 meter
0.0929 meters2
3
0.0283 meters
0.0648 gram
2.54 centimeters
6.452 centimeters
3
16.39 centimeters
0.4536 kilogram
1.0160 metric tons
0.9072 metric tons
3.7853 liters
252 calories
x
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ACKNOWLEDGEMENTS
This report was prepared by Arthur D. Little, Inc.; however, the information
and data contained in the report represent the work of many individuals
from several organizations who have been involved in this project. The
principal participating organizations are Louisville Gas and Electric,
Inc., Combustion Equipment Associates, Inc., and Arthur D. Little, Inc.
In addition, we would like to acknowledge the efforts and contributions
from persons in other organizations. Norman Kaplan, the EPA Project
Officer for this demonstration program, has made important technical con-
tributions and has been instrumental in the management of the entire
project. Mike Maxwell, the Director of Emissions/Effluent Technology
at EPA's Industrial Environmental Research Laboratory, was responsible
for overall planning and review for this program and has provided invalu-
able guidance and support. And Randall Rush of the Southern Company
Services has made important contributions of a technical nature to the
design of the system.
xi
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I. SUMMARY
A. OVERALL PURPOSE AND SCOPE
The dual alkali process developed by Combustion Equipment Associates, Inc.
(CEA) and Arthur D. Little, Inc. (ADL) has been installed in Unit No. 6,
a coal-fired boiler at Louisville Gas and Electric Company (LG&E) Cane
Run Station for controlling SOj emissions. The Federal Environmental
Protection Agency (EPA) has selected this system as a demonstration plant
for dual alkali technology and is participating in funding of the opera-
tion, testing, and reporting of the project.
The project consists of four phases:
I Preliminary Design and Cost Estimation
II Engineering Design, Construction, and Mechanical Testing
III Startup and Performance Testing
IV One Year Operating and Test Program
Construction of the system was completed in February, 1979 and system
startup was initiated in March, 1979. At the conclusion of startup,
the system will undergo acceptance testing followed by a one year demon-
stration test program. The test program will be conducted by Bechtel
National, Inc. (Becthel) under contract to EPA. The objectives of the
demonstration program are:
• Characterize the system operation over the range of conditions
encountered on Cane Run Unit No. 6 including exploratory testing
of the effect of fly ash inclusion and the substitution of
commercial lime for carbide lime on system chemistry;
• Monitor the performance of the system relative to design criteria
and performance guarantees set forth in the LG&E EPA contract;
• Evaluate the overall technical and economic feasibility/applicability
of the system;
• Demonstrate long-term reliability;
• Investigate environmentally acceptable methods of waste disposal;
and
• Study the effect of the system (in a generic sense) on plume
dispersion.
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This report covers the work in Phase II of the program including: the
final engineering design; construction and mechanical testing; and
installed capital cost for the system.
B. THE CEA/ADL DUAL ALKALI SYSTEM
1. General System Description
The dual alkali system involves absorption of 862 using an aqueous solu-
tion of alkaline sodium salts. Regeneration of the spent absorbent solu-
tion is accomplished using lime which produces a solid waste of calcium-
sulfur salts. The system operates in a closed loop, the only waste
material being a washed filter cake—there are no other solid waste or
liquid purged streams. In most applications, the system involves basically
four process subsections: flue gas contacting (S02 absorption); absorbent
solution regeneration and formation of waste solids; waste solids dewatering
(thickening and filtration); and raw materials storage and feed preparation
(for soda ash and lime). In some cases, the waste filter cake may be further
processed in a treatment facility to produce a stabilized material for
disposal.
The process operates in a concentrated active sodium mode3 and is capable
of S02 removal efficiencies in excess of 95% over a range of inlet S02
concentrations normally encountered in coal fired utility boiler applica-
tions. In addition to S02 removal, the system is highly effective in
absorption of chlorides from the flue gas; and particulate removal can
also be accommodated by appropriate scrubber selection.
2. Application to Cane Run Unit No. 6
Cane Run Unit No. 6 is a high sulfur, coal fired boiler having a gross
peak capacity of 300 Mw. The sulfur content of the coal burned in this
unit ranges from about 3.0% to 6.3% (dry basis); and the chloride content
typically varies from 0.03% to 0.06% (dry basis). The system is designed
for S02 control only and is capable of operating with coal sulfur contents
in excess of 5.0% (dry basis). Design flue gas conditions down stream of
the induced draft fan and at the inlet of the dual alkali system are as
follows:
• two parallel trains
• gas flow rate—1,065,000 acfm
• temperature—300°F
• pressure—minus 1 to plus 2 inches W.G.
• S02 concentration—3,471 ppm (dry basis)
• particulate matter concentration—<0.0537 grains/acf
aSee glossary for definition of dual alkali terminology.
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The system is modular in nature and includes two absorber modules, two
reactor trains (each train consisting of two reactors in series), one
thickener, and three filters. The absorption system can be operated
from 20% to 100% of the gross peak capacity. At loads less than 60%
of the design capacity, the system can be operated with a single absor-
ber module. The system can also be operated with one reactor train at
100% load for short durations under design conditions. Spare capacity
in the system includes: pumps—100%; filters—50%; and instrumentation
for operation—100%. Normally, the system will utilize locally available
carbide lime, a byproduct of acetylene production. However, commercial
lime will also be used for some test periods during the demonstration
program. Waste filter cake produced by the system will be stabilized
in a separate waste processing plant to be installed by IU Conversion
Systems, Inc. (IUCS). The stabilized material will then be disposed of
in landfills adjacent to the plant.
The CEA/ADL dual alkali system has been designed to meet the following
process performance guarantees:
• Emissions from the system shall be no greater than 200 ppm S02
(dry basis) at coal sulfur contents of up to 5.0%; and the sys-
tem will provide 95% 862 removal for coal containing greater
than 5.0% sulfur.
• The system will cause no increase in particulate matter in the
flue gas.
• Consumption of lime will not exceed 1.05 moles of available
CaO per mol of S02 removed from the flue gas.
• Sodium make up will not exceed 0.045 moles of Na2COo per mole
of SOy removed from the flue gas.
• The system will consume less than 1.2% of the power generated
by the boiler at peak boiler load.
• The filter cake will contain a minimum of 55% insoluble solids.
• The system will have an availability13 of at least 90% for a one
year period.
C. CAPITAL INVESTMENT
The installation of the dual alkali system at Cane Run Station Unit No. 6
required capital investment in three different facilities: the flue gas
desulfurization (FGD) system itself, the lime slurry feed system, and a
waste processing and disposal system. Each of these facilities have
DAvailability is defined as the ratio of the hours the system is available
for operation and the total hours in the operating period (expressed as a
percentage).
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involved independent design and installation efforts, and their costs
are reported separately. While construction of the FGD system was
essentially completed in February, 1979, a significant amount of work
remained on the lime feed and waste processing facilities. Therefore,
the costs presented here represent the actual expenditures incurred
plus estimates for completion of the system.
Table 1-1 gives a summary of the capital investment for all three facil-
ities. The total projected cost of $20.6 million includes actual expen-
ditures reported through February 28, 1979 and the estimated capital
required for completion. Approximately 80% of this total projected
capital cost was expended through the end of February. Most of the
remaining 20% is related to the waste processing plants.
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Subsystem
FGD
Lime Slurry Feed
Waste Disposal
TABLE 1-1
CAPITAL COSTS FOR THE DUAL
ALKALI SYSTEM AT LG&E'S
CANE RUN UNIT NO. 6
($000)*
Erection and Engineering
Material Costs"
10,256
800
1,959
Costs
6,207
416
959
Total
16,463
1,216
2,918
20,597
As-incurred costs plus estimate for completion basis.
^Including spare parts
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II. INTRODUCTION
A. PURPOSE OF PROJECT
The project covers the full scale application of the CEA/ADL dual
flue gas desulfurization (FGD) system to Unit No. 6, a coal-fired boiler
at Louisville Gas and Electric Company's (LG&E) Cane Run Station in
Louisville, Kentucky.
The system has been installed on this existing 300 Mw (gross peak capacity)
unit to comply with requirements3 of the Jefferson County Air Pollution
Control District, the Kentucky State Division of Air Pollution, and
Region IV of the U.S. EPA. EPA selected the dual alkali S02 control pro-
cess at LG&E as a demonstration system for dual alkali technology and
is participating in funding of the operation, testing, and reporting of
the project.
The dual alkali system has the capability to control the S02 emissions
to less than 200 ppm dry basis without additional air dilution when
burning coal containing up to 5% sulfur. When burning coal containing
greater than 5% sulfur, the system will remove at least 95% of the sul-
fur dioxide in the inlet flue gas. The dual alkali system is not designed
for removal of particulate matter; however, it is designed not to increase
the loading of particulate matter in the flue gas. As a demonstration
system, the purpose of the installation and operation is to establish:
• overall performance - S02 removal, lime utilization, sodium
makeup, regeneration of spent liquor, water balance, scaling
and solids buildup problems, materials of construction, waste
cake properties, reliability, and availability.
• economics - capital investment and operating cost.
B. SCOPE OF WORK
The scope of work for the project includes the design, construction,
startup, acceptance testing, and one year of operation of a CEA/ADL
concentrated mode dual alkali system on Unit No. 6, a 280 Mw coal-fired
boiler at LG&E's Cane Run Station. The system is to be designed to
treat all of the flue gas emitted at the nominal rated capacity (280 Mw)
with the capability for treating flue gas equivalent to a minimum boiler
load of 60 MW and a maximum load of 300 Mw.
aRemoval of 85% of the S02 present in the flue gas at the scrubber inlet.
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LG&E is the prime contractor with overall responsibility for all aspects
of the project. CEA, as a subcontractor to LG&E, is responsible for the
engineering design, for the supply of all process equipment, and for
engineering assistance during startup and acceptance testing. CEA is
also responsible for compliance with all process guarantees and equipment
warranties. ADL, a subcontractor to CEA, will provide process engineering
support to CEA during design, startup, and acceptance testing; and will
provide process assistance to LG&E in the operation of the system during
the one year test program. ADL is also responsible for the preparation
of all reports required under the EPA/LG&E contract.
The work is divided into four phases:
• Phase I - preliminary design and cost estimates;
• Phase II - engineering, design, construction, and mechanical
testing;
* Phase III - startup and performance testing; and
• Phase IV - one year of operation and testing.
Baseline testing on the boiler and monitoring of the system performance
during acceptance testing and the one year test program is not included
as a part of this contract. This work will be carried out by Bechtel
under a separate contract with EPA.
This report covers work performed in Phase II of the project. During
this phase, LG&E/CEA/ADL were to:
• complete all aspects of the detailed engineering including
material and equipment specifications;
• fabricate or procure the materials and equipment;
• construct the dual alkali plant;
• provide a system for disposal of all waste products from the
plant operation;
• provide all spare parts, maintenance supplies, and operating
materials;
• demonstrate the mechanical acceptability of the plant;
• prepare an operating manual; and
• select and train operators to properly operate the demonstration
plant and establish and properly staff a control laboratory.
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This report describes in detail the plant, as built, and its planned
mode of operation. It includes: a description of the process; the
operating and control philosophy; material balances and utility require-
ments; plant layout; a description of major items of process equipment;
a description of offsites and auxiliaries; results of the mechanical
testing; and actual capital costs for the system.
C. PROJECT SCHEDULE
The overall project schedule covering all phases of the dual alkali
demonstration project is given in Figure II-l. The overall project,
including the one-year test program, was originally scheduled for 40
months (with an additional one month for completion of the final draft
report).
Phases I and II were scheduled to begin simultaneously to expedite the
overall project. Phase I (preliminary design) was scheduled for five
months including preparation of the draft report. Phase II (engineering
design and construction) was scheduled for 24 months starting with the
signing of the contract. A detail of the schedule for Phase II is given
in Figure II-2.
As indicated in Figures II-l and II-2, the project has been delayed due
to the severe winter of 1977/1978. The projected schedule for comple-
tion of the project is shown in Figure II-l.
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1976
1977
-I I-
1978
-) I-
1979
I-
1980
-I
Phase I
ONDJFMAMJJASONDJFMAMJJASONDJFMAMJJASONDJFMAMJJ
0 4 8 12 16 20 24 28 32 36 40 44
• Preliminary Engineering -
• Cost Estimation
• Phase I Report
Phase II
• Detailed Engineering
• Material and Equipment
Specification
• Purchasing
• Field Construction
• Operating Manual
• Operator Training
• Maintenance Plan
• Mechanical Testing
• Phase II Report
Phase III
• Process Startup
• Acceptance Testing
• Phase III Report
Phase IV
• Review/Input Test Plan
• Test Program
• Phase IV Report
• Final Report
Initial Project Plan
Actual Schedule
Projected
Figure II-l: Dual Alkali Demonstration Overall Project Schedule
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1976
1977 " 1978 1979
• Engineering
• Material & Equipment Specification
• Purchasing
• Delivery
• Site Work
• Foundations & Pump Buildings
• Breeching Tie-in
• Fan & Reheater Erection
• Absorber Erection
• Tank Erection
• Duct Erection & Insulation
• Vacuum Filter Building
• Pumps & Piping Installation
• Electrical & Control
*
• Mechanical Testing
* Operator Training
Maintenance plan
• Operating Manual
fe
• Phase II Report
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III. CEA/ADL DUAL ALKALI PROCESS TECHNOLOGY
Dual alkali (or double alkali) is a generic term used to describe flue
gas desulfurization (FGD) systems involving the absorption of S02 using
a soluble alkali, followed by reaction of the spent scrubber solution
with lime and/or limestone to regenerate the alkali and produce a waste
calcium-sulfur salt for disposal.
The two principal features of dual alkali technology which set it apart
from conventional direct lime and limestone scrubbing are: (1) the use
of a clear solution rather than a slurry for contacting the flue gas in
the absorber; and (2) reaction of the solution in a separate absorbent
regeneration section to form the waste solids rather than forming the
waste solids as a part of the scrubbing operation. The use of solution
(rather than slurry) scrubbing has a number of important advantages.
First, with alkaline solutions, high S02 removal efficiencies (95%+) can
be easily achieved over a wide range of inlet S02 concentrations. Second,
the precipitation of the waste calcium sulfite/sulfate solids is performed
outside the scrubber circuit in a specially designed reactor system. The
control of the crystallization reactions allows for the formation of
waste solids with good dewatering properties. Finally, since S02 absorp-
tion is accomplished using clear solutions and precipitation reactions
occur outside the scrubber, there is minimal scale potential in the
scrubber circuit. Hence, there is no need for washing the mist eliminator
to prevent solids deposition and scale formation.
A. PROCESS CHEMISTRY
The dual alkali system installed on Unit No. 6 at Cane Run Station
utilizes alkaline solutions of sodium salts for scrubbing the gas and
absorbing SOo. The solution is regenerated using carbide lime, a waste
product from the production of acetylene.
The process is designed to operate as a concentrated-mode dual alkali
system (in contrast to a dilute mode). The term "concentrated-mode"
indicates the range of concentration of alkaline sodium salts in the
absorbent liquor. In a concentrated-mode system the concentration of
the absorbent solution is such that the precipitation of gypsum (CaSO, •
2H90) as a separate crystalline phase does not occur during absorbent
regeneration, so the system operates unsaturated with respect to gypsum.
Based on the major steps of the dual alkali technology, the flue gas
desulfurization system can be broken down into four process areas :
gas scrubbing; regeneration of scrubbing solution; solids separation;
and raw materials preparations. Some variations in equipment and
operation of the system would be expected for different applications of
the dual alkali technology. The following description represents a
11
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concentrated-mode system utilizing alkaline sodium solutions for the
removal of S02 with commercial, slaked lime for regeneration of the
sodium solution. A generalized process flow diagram is shown in
Figure III-l.
1. Flue Gas Scrubbing
Dual alkali systems are, in general, capable of simultaneous particulate
matter and S02 control as are most wet scrubbing nonrecovery FGD systems.
However, Cane Run Unit No. 6 is equipped with an existing high efficiency
electrostatic precipitator for control of particulate matter. Therefore,
the following description shall be restricted to that of a scrubbing
system designed for S02 removal only.
In the absorption section of the system, SC>2 is removed from the flue gas
by contacting the gas with a solution of sodium salts. This is usually
accomplished in a tray tower equipped with quench sprays for cooling and
humidifying the gas. The scrubbed gas is then reheated to prevent conden-
sation and corrosion in the ducts and stack and to improve atmospheric
dispersion after being exhausted from the stack.
The alkaline solution used to remove SC>2 from the flue gas contains sodium
sulfite (Na2S03), hydroxide (NaOH), carbonate (Na2C03), sulfate (Na2SO^),
and chloride (NaCl). During the process of removing S02, the carbonate,
hydroxide, and some sulfite are consumed resulting in a spent sodium
sulfite/bisulfite liquor. The S02 removal process can be represented by
the following overall reactions:
2Na2C03 + S02 + H20 -»• Na2SC>3 + 2NaHCC>3 (1)
NaHC03 + S02 -»• NaHS03 + CO^ (2)
2NaOH + S02 -»• Na2S03 + H20 (3)
Na2S03 + S02 + H20 •*• 2NaHSC>3 (4)
Although the actual reactions within the absorber are more complex, involving
various intermediate ionic dissociations, the above set of simplified, over-
all reactions is an accurate representation of the overall consumption and
generation of the various components.
Sodium sulfite plays the most important role in the absorption of SO since
it is usually present in the greatest concentration. The hydroxide and
carbonate are present in the absorber feed only in small amounts. The con-
centration of these three alkaline components is a measure of the SO removal
capacity of the absorbing liquor. This capacity is conveniently expressed
in terms of the "active sodium" concentration where [active sodium] - 2 x
[Na2S03] + [NaOH] + 2 x [Na2C03]. It must be pointed out that the use of
the term active sodium is simply one of convenience since it is only an
indirect indication of the absorptive capacity of the liquor SO is
actually absorbed by or reacts with the sulfite, hydroxide, or carbonate
ions rather than the sodium ion. The dual alkali system for Cane Run Unit
No. 6 is designed to operate at an "active sodium" concentration of 0.45 M
in the absorber feed.
12
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Set ubbed Gjs
Solids
Figure III-l: Dual Alkali Process Flow Diagram
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Sodium sulfate and sodium chloride do not participate in the S02 removal
process. In this sense, they are considered "inactive" components. The
presence of sodium sulfate and sodium chloride is principally the result
of secondary absorption reactions. Sodium sulfate" is formed'by the
oxidation of sodium sulfite via reaction with oxygen absorbed from the
flue gas. Oxidation also occurs in other parts of the system where
process solutions are exposed to air; however, the amount of oxidation
is sraill relative to the oxidation which occurs in the absorber.
For a concentrated-mode dual alkali system, the rate of oxidation in the
absorber is proportional to oxygen mass transfer, which is a function of
the absorber design, oxygen concentration in the gas, gas temperature,
and the nature and concentration of the species in the scrubbing solution.
For a given set of process parameters, the oxidation rate in moles of
sulfite oxidized per unit of time is relatively independent of the S02
removal rate. For convenience, though, the amount of oxidation is fre-
quently expressed, on an equivalent basis, as a percentage of the S02
removed. For example, in the case of a high sulfur, coal-fired utility
boiler with a flue gas containing about 4-5% 02 and about 2500 ppm S02,
on the order of 5% to 10% of the S02 removed from the flue gas would be
expected to be oxidized and appear as sulfate in the spent scrubbing solu-
tion. The remaining 90% to 95% would appear in the spent scrubbing solu-
tion as sulfite/bisulfite. Under similar conditions of absorber design
and solution characteristics, much higher relative oxidation rates can be
encountered at higher oxygen concentrations in the gas (higher oxygen mass
transfer rates) or at much lower S09 removal rates (as in low sulfur coal
applications).
At steady state, the sulfate must leave the system either as calcium
sulfate or as a purge of sodium sulfate at the rate at which it is being
formed in the system. As will be discussed later, relative oxidation
rates as high as about 25-30% of the S02 removed can be tolerated in
concentrated-mode systems without intentional purge of sodium sulfate with
the waste solids.
Sodium chloride is formed in the absorber by the reaction of chloride,
present in the flue gas as HC1 vapor, with the alkaline sodium solutions.
The level of sodium chloride in the system builds up to a steady state
concentration, such that the rate at which sodium chloride leaves the
system with the washed filter cake is equivalent to the rate at which it
is picked up in the absorber.
2. Absorbent Regeneration
The S02 absorptive capacity of the spent scrubbing solution bleed stream
is regenerated in this section of the dual alkali system. The regenera-
tion is accomplished in a two-stage reactor system using carbide lime
slurry.
14
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The regeneration of acidic sodium sulfite/sulfate scrubber effluent
solutions can be envisioned as a two-step process involving neutraliza
tion of bisulfite to sulfite followed by conversion of sulfite to
hydroxide:
Ca(OH)2 + 2NaHS03 -> CaSO-j • 1/2 H2CH + Na2S03 + 3/2 H20 (5)
Ca(OH) + NaS0 + 1/2 H0 -> CaS0 • 1/2 H(H + 2NaOH (6)
The first of these reactions is a neutralization reaction which goes to
completion. The second is a precipitation reaction in which the equi-
librium hydroxide concentration is limited by the relative solubility
products for calcium sulfite and calcium hydroxide, and the concentra-
tions of hydroxide and sulfite in solution. Both of these reactions
result in the formation of calcium sulfite solids. The usual form of
the calcium sulfite is as the hemihydrate salt (calcium sulfite =1/2 H?0)
Simultaneously with the neutralization and precipitation reactions in-
dicated above, a limited amount of calcium sulfate will also be
precipitated :
Ca + S0~ + xH2• CaS04» xH2(H (7)
In a concentrated-mode dual alkali system, the sulfate co-precipitates
with the calcium sulfite, resulting in a mixed crystal (or solid solution)
of calcium-sulfur salts. Gypsum is not formed. The relatively high sulfite
concentrations in the solution prevent soluble calcium concentrations from
reaching the levels required to exceed the gypsum solubility product, and
the system operates unsaturated with respect to calcium sulfate (as gypsum) .
The amount of sulfate co-precipitated with the calcium sulfite is a func-
tion of the concentrations of sulfate and sulfite and the reactor solution
pH. As the concentration of sulfate increases relative to sulfite, the
amount of sulfate precipitation increases. Thus, as the rate of oxidation
increases, the ratio of sulfate to sulfite in solution will increase until
the rate of calcium sulfate precipitation is sufficient to keep up with the
rate of sulfate formation by oxidation. Co-precipitation enables the sys-
tem to keep up with oxidation rates equivalent to 25% to 30% of the SC>2
absorbed without intentionally purging sodium sulfate. Under such con-
ditions, the solution will remain unsaturated with respect to calcium
sulfate, thereby avoiding high soluble calcium concentrations and atten-
dant scaling problems. The sulfate/sulfite ratio can obviously be in-
creased by increasing sulfate concentrations in the liquor and/or by
decreasing the sulfite or active sodium concentration. However, it is
desirable to operate with active sodium concentrations above about 0.15
M, below this concentration the system becomes "dilute" in active
sodium — a condition in which the system can become saturated or super-
saturated in calcium sulfate with soluble calcium concentrations rising
to levels of 400-800 ppm. The result would be higher scale potential
and a general deterioration in cake properties.
15
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In practice, a concentrated-mode system would normally be operated at a
total sodium concentration consistent with the highest sustained level
of oxidation expected—that is, a sodium concentration high enough that
under the worst conditions, with regard to oxidation, the active sodium
concentration would not fall below about 0.15 M Na+. The liquor compo-
sition can then vary with changes in oxidation, the sulfate/sulfite ratio
adjusting to whatever level is required to keep up with sulfate formation
in the system.
3. Solids Dewatering
Solids dewatering is a purely mechanical process involving thickening of
the reactor effluent slurry to 15-30 wt % solids, followed by filtration
to produce a waste filter cake. While the cake is being formed, it is
washed with fresh water to recover sodium salts that would otherwise be
lost in the process liquor discharged with the cake. The filter cake
represents the only waste discharged from the process. There are no
other purges from the system.
The solids content and chemical composition of the waste cake produced
from S0~ control alone will depend primarily upon the amount of oxidation,
the quality of raw lime, and the chloride content of the coal. In
general, for utility boilers firing medium to high sulfur coal, the waste
cake would normally be expected to contain 55-70 wt % insoluble solids
and have a chemical composition typically within the following ranges
(dry basis):
CaS03-l/2 H20 = 80-85 wt %
CaS04-l/2 H20 = 5-15 wt %
CaCO- + Inerts = 5-10 wt %
Soluble Sodium Salts = 1-3 wt %
The amount of sodium lost in the cake will depend primarily upon the total
sodium concentration in the process liquor (which is largely a function of
the amount of oxidation and the chloride content of the coal), and the
extent of cake washing. The minimum level of sodium losses for a concen-
trated mode system is generally on the order of 0.5-1.0 wt.% of the total
dry solids, approximately 0.01 to 0.02 moles of Na+/mole S09 scrubbed.
This minimum level is dictated by liquor which is occluded within calcium-
sulfur crystals or trapped in interstices of agglomerates which cannot be
practically washed from the waste; and the rate at which chlorides and
other highly soluble anionic species enter the system. Such highly sol-
uble species must be purged in the cake, as in any nonrecovery solid waste
producing process, at the rate at which they enter the system. In a
sodium-based dual alkali system, these would leave as soluble sodium
salts (e.g., NaCl) rather than as soluble calcium and magnesium salts
16
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4. Raw Materials Preparation
Only two chemicals are required for the operation of the dual alkali
system: lime for regeneration and soda ash to make up for sodium losses.
Typically, lime would be slaked and hydrated prior to being fed to the
reactor system. At the Cane Run Station, however, carbide lime is avail-
able to LG&E as a slurry containing 25-30% insoluble solids. The slurry
is pumped to a day tank from which lime slurry is fed to the primary
reactors.
The rate of addition of soda ash to the system is adjusted to compensate
for the losses of sodium in the cake. Typically, the soda ash makeup
requirement should amount to about 1-3% of the total alkali requirement
on a molar basis (includes the alkali required for both S02 control and
chloride absorption/neutralization).
Clarified liquor from the thickener hold tank is added to soda ash to
prepare the makeup solution in the soda ash tank. The resulting solution
may be fed to either the thickener or the absorbers. If added to the
thickener center well, the sodium carbonate will soften the regenerated
liquor, reacting with dissolved calcium and precipitating calcium carbon-
ate. The precipitation of calcium carbonate will cause a slight loss in
the overall utilization of calcium since it is not removing any sulfur
from the system. The calcium loss, however, is small and amounts to about
1% or less of the calcium fed to the system.
Alternatively, the soda ash makeup solution can be added directly to the
absorber. The sodium carbonate reacts with acidic sodium bisulfite in
the absorber, producing sodium sulfite and liberating CC^. In this manner,
the soda ash is used directly in the absorption of SC>2 and thus avoids any
small, unnecessary loss of calcium due to calcium carbonate precipitation.
At LG&E, the soda ash solution will be directed to the absorber. The
flexibility exists, however, for pumping the makeup solution to the thick-
ener center well.
B. POLLUTION CONTROL CAPABILITIES
1. SC-2 Control
The sodium-based dual alkali process, operating in the concentrated active
sodium mode, is capable of SC>2 removal efficiencies in excess of 95% over
any range of inlet S02 concentrations encountered in coal-fired utility
boiler applications. In most cases, removal efficiencies approaching 99%
can be achieved on a continuous basis, as was demonstrated during the test
program on a 20 MM dual alkali prototype system . These high efficiencies
are accomplished by proper selection and design of the absorber unit
lLaMantia, C.R., et. al., "Final Report: Dual Alkali Test and Evaluation
Program", Volume III, EPA Contract 600/7-77-050, May 1977-
17
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and by adjustment of the active sodium/S02 stoichiometry in the absorber.
Such variation in S02 absorption efficiency can be effected without influ-
encing the overall lime stoichiometry or the sodium makeup requirement.
These high S02 removal efficiencies can be achieved in tray-type absorbers
at low L/G ratios, typically in the range of 5-10 gpm/1,000 acfm of satu-
rated gas. The pressure drop across the trays may be minimal, in the
range of 4-6 inches WG.
The high S02 removal capability of this process, when used in conjunction
with a boiler equipped with adequate control of particulate matter, allows
the option of removing virtually all of the S02 from the flue gas treated
in the scrubber and bypassing hot, untreated gas to provide part or all
of the reheat while still meeting the overall plant S02 emission regula-
tions in the combined treated and untreated flue gas. In such a system,
the scrubber size can be reduced since not all flue gas is treated and
the reheat requirements are reduced or eliminated.
2. Control of Particulate Matter
Removal of particulate matter can be accommodated in the process by appro-
priate selection of scrubbers. If particle removal is to be accomplished
as part of the overall system, then a higher energy particulate matter
removal device, such as a venturi scrubber, may be incorporated in this
system to provide for removal of both S02 and particulate matter. Removal
of particulate matter down to 0.02 grains/scfd or lower can be accomplished
using venturi scrubbers at moderate pressure drops on the order of about
20 inches WG.
3. Chloride Control
A major fraction of the chlorides in coal (greater than 90%) is volatilized
and appears in the flue gas as HC1. Any aqueous-based scrubbing system
would be highly effective in absorption of HC1 (and any HF) in the flue
gas. As a result, chloride concentrations will build in the closed liquor
loop to levels such that the rate at which chloride is discharged from the
system in the washed cake will equal the rate at which chloride enters the
system with the flue gas. Steady-state levels of chloride in the closed
liquor loop of a 20 Mw prototype CEA/ADL dual alkali system rose to as
high as 11,000 ppm (0.05-0.1% Cl in coal) with no apparent effect on the
process operation^- Tests of the lime regeneration reaction at ADL have
shown that lime utilization and solids properties are unaffected by chlo-
ride concentration as high as 25,000 ppm.
18
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IV. DESCRIPTION OF THE DUAL ALKALI PROCESS APPLICATION
AT THE CANE RUN STATION
This chapter provides a description of the application of the dual alkali
technology to the specific flue gas desulfurization requirements for LG&E's
Cane Run Unit No. 6. In designing the system, consideration was given to
the sources, characteristics, and amounts of flue gas to be cleaned as
well as to the type and sources of the required raw materials.
A. BOILER SYSTEM DESCRIPTION
Cane Run Unit No. 6 consists of a pulverized coal-fired steam boiler, built
by Combustion Engineering, with a Westinghouse turbine-generator. The unit
operates from a minimum of 60 Mw during off-peak hours to a maximum load of
300 Mw during peak hours. The annual average load is equivalent to approx-
imately 180 Mw (about 60% of the gross peak capacity).
Flue gas from the boiler passes, in parallel streams, through two Ljungstrom
combustion air preheaters. Each air preheater discharges flue gas through
separate ducts to an electrostatic precipitator designed for 99.4% removal
efficiency of particulate matter (weight basis). From the precipitator, the
gasses enter two parallel induced draft fans, each handling 50% of the total
gas.
The sulfur dioxide removal system, installed between the existing induced
draft fans and the stack, draws hot flue gas from the outlet of the induced
draft fans through two booster fans. The scrubbed gas is reheated and then
returned to the existing entrance to the stack. Appropriate dampers have
been provided to allow bypass of gas around the scrubber system using the
existing ductwork.
Coal for Unit No. 6 is received from a number of sources. A dry ultimate
analysis typical of the coal fired is given in Table IV-1. The average
sulfur content on a dry basis is 4.8% and varies from 3.5% to 6.3%. The
average chloride content of the coal is 0.04% and varies from 0.03% to
0.06%. The average 4.8% sulfur content and 11,000 Btu/lb will result in
an S02 emission level equivalent to about seven times that allowed by the
present Federal New Source Performance Standards (1.2 Ibs of S02/MM Btu).
B. DESIGN CONDITIONS FOR THE DUAL ALKALI SYSTEM
The design basis for the dual alkali system is summarized in Table IV-2.
Design conditions correspond to coal containing 5% sulfur and 0.04% chlo-
ride and having a heating value of 11,000 Btu/lb on a dry basis.
19
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TABLE IV-1
ULTIMATE ANALYSES OF COAL FIRED IN UNIT NO. 6
(Dry Basis)
Typical
Analysis , %
67.15
4.72
1.28
0.04
4.81
17.06
4.94
Range,
64.0 -
4.3 -
0.6 -
0.03 -
3.5 -
15.5 -
3.8 -
%
70.0
5.25
1.5
0.06
6.33
24.5
6.2
Carbon
Hydrogen
Nitrogen
Chloride
Sulfur
Ash
Oxygen
Moisture
Heat Content, Btu/lb dry coal
100.00
8.95
11,000
8.0 - 10.75
9,500-12,400 Maximum
10,400-11,900 Normal
20
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TABLE IV-2
DESIGN BASIS
Coal (Dry Basis);
Sulfur
Chloride
Heat Content
Inlet Gas;
Flow Rate (Volumetric)
(Weight)
Temperature
S02
°2
Particulate Matter
Outlet Gas;
so2
Particulate Matter
5.0% S
0.04% Cl~
11,000 Btu/lb
1,065,000 acfm
3,372,000 Ib/hr
300°F
3,471 ppm (dry basis)
5.7 vol.%
^0.10 lb/106 Btu
-200 ppm (M).45 lb/106 Btu)
^0.10 lb/106 Btu
21
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The flue gas conditions at the inlet of the dual alkali system are given
in Table IV-3. The design gas capacity of 3,372,000 Ibs of flue gas per
hour (combined flow to both scrubbers) corresponds to the boiler peak load
capacity of 300 Mw.
The dual alkali system is designed to meet all applicable federal, state,
and local pollution control and safety regulations. The maximum S02 con-
centration in the scrubbed gas will be 200 ppm (for coal containing up to
5% sulfur), well below requirements of the current NSPS. There will be
no discharge of process liquor from the system; and the disposal of the
waste solids produced will meet all applicable federal, state, and local
solid waste disposal regulations currently in effect. None of the wastes
will be discharged to or allowed to enter any naturally occurring surface
water. Plans for disposal are discussed as a part of this report.
The existing 518 foot stack will be the only source of gaseous emissions
from the system. A flue gas bypass will be provided to allow untreated
boiler flue gas to enter the stack, bypassing the dual alkali system.
The scrubber system is designed to be isolated from the flue gas during
periods in which the bypass is open to allow safe entry into the scrubber
system for maintenance and inspection while the boiler continues normal
operation. Also, each absorber can be isolated independently and main-
tenance can be provided to one absorber while the other absorber is in
operation. The duct dampers are designed such that with the dual alkali
system in operation and the bypass closed, no more than 1.0% of the total
flue gas will leak through the bypass system into the stack.
The dual alkali system has been equipped with sufficient instruments, in
addition to those required to operate the process, to permit accurate
measurements of the appropriate streams required to calculate material and
energy balances. In particular, instrumentation has been provided to
permit continuous monitoring of S02 concentrations in the flue gas entering
and leaving the control system as well as the measurement of the quantities
of chemicals and water entering the system and filter cake discharge.
C. GUARANTEES
The process guarantees listed below include minor revisions since publica-
tion of the project manual containing the preliminary design and cost
estimate (EPA-600/7-78-010, January, 1978).
1. Sulfur Dioxide Emission
The system shall provide such control that emissions from the stack shall
be no greater than 200 ppm by volume S02 dry basis not including SO, added
from the operation of the reheaters and without additional air dilution
when burning the coal containing less than 5% sulfur. When burning coal
containing 5% sulfur or greater, the system shall remove at least 95% of
the sulfur dioxide in the inlet flue gas.
22
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TABLE IV-3
FLUE GAS CONDITIONS AT THE INLET OF THE DUAL ALKALI SYSTEM
Normal Operating Temperature
Maximum Gas Temperature for Periods up to 5 Mins.
Normal Pressure at I.D. Fan Outlet
Boiler Excess Air
Air Heater Leakage
Flue Gas Density at Sea Level @ 70°F
Total Pressure at Stack Entrance
Boiler Load Points (Ibs/hr flue gas):
Design
Boiler Maximum Continuous Rating
Control Load
Minimum Normal Operating Load
300 °F
600 °F
-1" to +2" WG
25%
Maximum 35%
10%
0.078 lb/ft3
+2" WG
3,372,000
3,003,000
1,440,000
658,000
23
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2. Particulate Matter Emission
In addition to meeting applicable regulations, the system shall also meet
Federal New Source Performance Standards for emissions of particulate
matter under all conditions of boiler operation. The dual alkali system
shall not add any particulate matter to the emissions of particulate
matter that is received by the system from the LG&E Cane Run Unit No. 6
electrostatic precipitator.
3. Lime Consumption
The consumption of lime in the system shall not exceed 1.05 moles of avail-
able CaO in the lime feed per mole of SC^ removed from the flue gas.
4. Sodium Carbonate Makeup
Soda ash makeup shall not exceed 0.045 moles of Na2C03 per mole of S02
removed from the flue gas provided that the chloride content of the coal
burned averages 0.06% or less. If the average chloride content of the
coal is above 0.06%, then additional sodium carbonate consumption will
be allowed at the rate of 1/2 mole Na2COo for each mole of chloride (Cl~)
in the flue gas resulting from chloride in excess of 0.06% in the coal.
The Seller as part of the guarantees shall perform the necessary research
and design to reduce the makeup requirements of N32C03 from the guarantee
point to a level approaching minimal makeup.
5. Power Consumption
At the peak operating rate (300 Ma), the system shall consume a maximum
of 1.2% of the power generated by the unit.
6. Waste Solids Properties
The waste produced by the vacuum filter shall contain a minimum of 55%
insoluble solids.
7_. S02 System Availability
The system shall have an availability (as defined by the Edison Electric
Institute for power plant equipment) of at least 90% for one year. Thus,
the system shall be available for operation at least 90% of the calendar
time.
D. PROCESS DESCRIPTION
The description of the dual alkali system for Cane Run Unit No. 6 can be
conveniently divided into six parts: (1) absorber section (flue gas
scrubbing); (2) reactor section (regeneration of scrubbing solution)-
(3) solids dewatering; (4) raw materials preparation; (5) waste disposal-
and (6) provisions for spills and leaks. The process flow diagram for
the overall system is shown in CEA Drawings 040044-1-1 and 040044-1-2
24
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i A.
^
EXISTING
CHIMNEY
1
11
i >
EXISTING 1
JT
II
>l
,
••-•
i KCJ) ^>
\ 2 °"- XV ^=^
I " ' sW " " A U FAN F-102
\ *'
•— OIL FIRED
REHEATER 1
E-IOI
fl -1 ^ -J ^
U "^ X/ ^* NX* ~"^j
n FROM ABSORBER A-201 =p=^L=*
. ^ ,/K\_ .| __H J L
U ^ A "~^~~^ ./^ ^^^ FROM THICKENER
i uu « HOLD TANK
1 BY CCA (n.vrn uriTtnl ^'MIST ELIMINATOR ««J XV ~ >V
ifc^" EUEROENCV WATER • -^^"^^X^^^^^^V^^T^^
L FROM REHEATER E-801 SUPPLY , \(V
T* 1 N.y v^' ".,' Nvx- H^. XV 1
! i A. ^™N5^ *
TO ABSORBER A-201 A,\ IL_ I
,-, ^ . /\ * J 1
; U \/ J^j^Q ^^ 0 ABSORBER Oj^
L BOOSTER FAN F-IOI A-IOI
n .^. ^n=^>==*
£l* 1! NX X^T v TO ABSORBER A-201
/^, "EXISTING J
1 EXISTING
] PRECIPITATO
L;X
I EXISTING BOIL
1
1
:
^ BOOSTER FAN Ij—^IO/-'
Tr^ F-201 ^_— _^
ll RECYCLE PUMP XN fc
I TYPICAL FOR (2) NX^^
| RECYCLE PUMPS
- | P-I07A a P-I07B
.J
,n
i
| PROCESS FLOW DIAGRAM
.ssutu hOR PHASE CEA-ADL-DUAL ALKALI
rOMMKTION EQUIPMENT ASSOCIATES " REPORT 6/ls/79 DESULFURIZATION PROCESS
UJNWIDIIUN cuuirmufi AMUUAIU, LOUISVILLE GAS a ELECTRIC COMPANY
INCORPORATED CANE RUN UNIT NO.S
NEW YORK. N.Y. DRAWING NO Q40044 — | - | R Q
-------
FROM ABSORBER A-gQI
REACTOR
TRANSFER
PUMP P-202
SODA ASH
SOLUTION
TANK V-106
REACTOR
TRANSFER
PUMP P-102
COMIUSTION EQUIPMENT ASSOCIATES,
INCORPORATED
NEW YORK. N.Y.
ISSUED FOR PHASE
II REPORT 6/18/79
PROCESS FLOW DIAGR/
CEA-ADL DUAL ALKALI
DESULFURIZATION PROCESS
LOUISVILLE GAS 8 ELECTRIC COMPANY
CANE RUN UNIT NO. 6
DRAWING NO.
O4OO44-\-2
RG
-------
1. Absorber Section
The absorber section consists of two identical scrubber modules. Each
module is made up of a booster fan, an absorber, an oil-fired flue gas
reheater, and two recirculation pumps (one operating and one back-up).
Flue gas is drawn from the existing induced draft fans and is forced
through the absorbers by means of the booster fans. The basic design
and control philosophy is predicated on both absorbers operating simul-
taneously with each handling half the boiler load. However, during periods
of low boiler load, one absorber is capable of handling all of the gas.
Hence, in order to allow for greater flexibility in operation and provide
for the possibility of allowing maintenance on one module while the system
is still in service, a common duct connecting the two booster fan inlets
has been incorporated. A bypass is also provided to allow complete shut-
down of the scrubbers while the boiler is still on line. The bypass and
FGD system inlet dampers have been properly interlocked to enable bringing
the absorbers on- or off-line without interruption of the boiler operation.
Hot flue gas (^300°F) entering each absorber is first cooled by a set of
sprays which direct scrubbing solution at the underside of the bottom
tray. In addition to providing temperature control at the bottom of the
absorbers, these sprays keep the underside of the tray and the bottom
of the absorber free of any buildup of fly ash solids. The cooled,
saturated gas passes through a set of two trays where SOo is removed
and then through a chevron-type demister. After leaving the absorber,
the scrubbed gas is reheated 50F° (to a temperature of about 175°F)
by mixing it with hot flue gas from an oil-fired reheater to avoid con-
densation and corrosion as it is exhausted to the stack.
The scrubbing solution which flows counter-current to the gas is collected
at the bottom of the absorber. This liquor is used for the quench sprays
and as a recycle stream to the top tray for pH control. Since the scrubbing
solution is regenerated with lime, the feed to the absorber contains sod-
ium hydroxide and therefore is very alkaline. A high tray feed pH
increases the absorption of C02 which in turn increases the potential
for CaCOo scaling in the absorber. The recycle also ensures proper
liquid loading on the trays. A bleed stream from the bottom of the
absorber is sent to the reactor system for regeneration. Provisions
have been made for an automatic emergency water supply to spray and
quench the hot flue gas in the event that the recycle pump fails.
Pressures and temperatures are measured at appropriate points throughout
the gas and scrubber systems. Removal of S02 is monitored by continuous
S02 analyzers at the inlet and outlet of the absorber. The pH of the
bleedstream and of the feed to the top tray is continuously monitored also.
27
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2. Reactor Section
This section of the system consists of two identical reactor trains each
containing a primary and secondary reactor.
At operation under design conditions, each reactor train would handle the
regeneration of solution from the corresponding absorber; although for
short periods of time, a single reactor train is capable of handling the
solutions from both absorbers operating at design conditions. When the
boiler is firing typical or average coal (3.5-4.0% sulfur), only one
reactor train is normally required.
The spent scrubbing solution is introduced to the primary reactor along
with slurried carbide lime from the lime day tank. In this short residence
time reactor (3-15 minutes), the regeneration of scrubbing solution begins.
The primary reactor overflows into a second, longer residence time reactor
(30-60 minutes) where regeneration is completed. The secondary reactors
are maintained at a pH typically in the range of 11 to 12 by controlling
the amount of lime slurry fed to the primary reactors.
The slurry from the secondary reactor is fed to the thickener feed well
where the separation of the regenerated solution from the solid waste is
initiated.
3. Solids Dewatering
The reactor effluent, a slurry containing 2-5% insoluble solids, is
directed to the feed well of the thickener. The thickener is generally
operated to provide an underflow (thickened) slurry containing 15-30
wt.% solids, even though the slurry can be thickened to 40 wt.% solids
or more. Slurries in the range of about 25 wt.% solids allow better
control of filter cake washing, control which cannot always be achieved
with variations in filter drum speed and pool depth. The thickener under-
flow slurry is recirculated past the filters in a recycle loop that returns
the slurry to the solids zone of the settler. A bleed from this recircu-
lation loop is fed to the filters. Each filter is equipped with an over-
flow pipe returning to the solids zone in the thickener to allow for
operation in an overflow mode and thereby provide against inadvertent
overflow of the filter hold tank.
There are three filters, each rated to handle 50% of the total solids
produced at the design conditions. Each filter can be operated independ-
ently. For optimum performance (to obtain cake containing high dry
solids and low soluble salts) it is desirable to operate the filters at
fixed conditions (constant drum speed, submergence, wash ratio, etc.).
Therefore, the cake rate is controlled by changing the number of filters
in operation. The number of filters in operation is determined by the
28
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quantity of solids accumulated in the thickener, which is reflected in
the solids concentration in the underflow slurry and the thickener rake
lift position indicator. The density of the underflow slurry is measured
and thickener hold tank liquor is added as required to maintain the per-
cent solids in the underflow slurry at about 20-25%. The number of filters
in operation is changed if the concentration of solids in the underflow
slurry cannot be controlled using the dilution liquor. For operation at
typical conditions (3.5% S and an average daily load of 60-70%), it is
anticipated that only 2 filters need to be operated about one shift per
day.
The solid cake is washed on the filter using a series of water spray banks.
This wash removes a large fraction (approximately 90%) of the occluded
soluble salts from the cake and returns these salts to the system, there-
by reducing sodium losses and minimizing sodium carbonate makeup. The
total wash rate will usually be set to be a constant percentage of the
cake discharge rate. The mixed filtrate and wash liquor from the filter
is collected in the filtrate sump from which it is returned to the
thickener.
Clear liquor overflow from the thickener is collected in the thickener
hold tank which both provides surge capacity for the absorbent liquor
feed to the scrubber system and maintains overall control of the volume
of liquor in the system. Water is added to this hold tank to make up
for the difference between total system water losses (evaporation and
cake moisture) and total water inputs from other sources (sodium makeup
solution, pump seals, lime feed, and cake wash).
4. Raw Materials Preparation
Two chemicals are required for the operation of the dual alkali system:
lime for absorbent regeneration and soda ash to make up for sodium losses.
Carbide lime, a byproduct of acetylene production, is available to LG&E
at a significantly lower price than commercial lime. The carbide lime is
barged to the Cane Run Station as a slurry containing approximately 30%
insoluble solids. The slurry is hydraulically unloaded and pumped to a
main storage tank at the plant. Excess liquor is then decanted from the
tank and returned for reuse in transport of carbide lime. From the main
storage tank, the lime slurry will be pumped to a grinding system consisting
of a hydroclone and wet ball mill to prevent feeding of oversized material.
From the grinding system, the lime will be pumped to the dual alkali system
day tank which supplies lime to the primary reactor at the appropriate
rate. Since the installation of the grinding equipment has been delayed
beyond the startup date for the dual alkali system, a disintegrator with
coarse screens has been temporarily installed upstream of the day tank
for rough sizing of the raw carbide lime until the permanent grinding
facility is completed.
29
-------
The utilization of available Ca(OH)2 in the slurry (conversion to CaSOx
salts) is expected to be on the order of 98%. Thus the overall feed
stoichiometry to the system (moles of available Ca(OH)2/mole of S(>2
absorbed) should be on the order 1.0 (taking into account the soda ash
makeup). The specifications for the carbide lime as delivered to the
dual alkali system are given in Table IV-A. The carbide lime contains
92.5 wt.% Ca(OH)2 and has a particle size distribution equivalent to
90% through a 325 mesh screen.
The addition of sodium carbonate to the system is to compensate for the
losses of sodium in the cake. Despite washing the cake, some liquor,
containing soluble sodium salts, will inevitably remain occluded in the
cake.
Dry, dense soda ash is received at the plant and stored in the soda ash
silo from which it is fed to the soda ash solution tank by means of a
weigh feeder. The rate of addition is proportional to the amount of lime
slurry fed to the system. Such relationship arises from the fact that
the sodium losses in the cake can be expressed as a percentage of the
solids produced, which in turn are related to the amount of lime added
to the system.
Soda ash solution can be made up using either clarified liquor drawn from
the thickener hold tank or fresh water. Provisions have also been made
to feed the soda ash solution either directly to the absorbers or to the
thickener. The normal mode of operation is to prepare the soda ash
makeup solution using clarified liquor and to feed it to the absorbers.
5. Waste Disposal
A long-range plan for the disposal of the dual alkali filter cake has
been developed as a part of an overall disposal plan for all FGD wastes
produced at the Cane Run Station. The plan involves stabilization of
the wastes generated by each of the three FGD systems via the addition
of lime and fly ash and dry landfill of the stabilized material adjacent
to the plant. Waste from the dual alkali system on Unit No. 6 will be
handled, processed, and disposed of independently of the wastes produced
by the direct lime scrubbing systems on Unit Nos. 4 and 5. Wastes from
these latter two units will be combined and handled in a common processing
plant.
The waste processing plant will be installed at the end of the filter
building. Filter cake from the dual alkali system is discharged into a
single conveyor (the filters are arranged in series—end to end), which
will carry the cake directly to the pug mill mixer in the processing
plant. A belt weigh element near the end of the conveyor measures the
quantity of cake produced. Fly ash from Unit No. 6 will be pneumatically
transported to the processing plant and stored in a live-bottom silo,
from which it will be discharged to a screw conveyor and fed to the pug
mill. The ash feed will be adjusted according to the filter cake rate
30
-------
TABLE IV-4
CARBIDE LIME SPECIFICATIONS
Carbide Lime
Slurry3
Calcium hydroxide
Ca(OH)2 92.50
Available calcium oxide
CaO 70.01
Calcium carbonate
CaC03 1.85
Silica
Si02 1.50
Iron and alumina oxides
R203 1.60
Magnesium oxides
MgO 0.07
Sulfur 0.15
Phosphorus 0.01
Free carbon 0.25
Free Water
Not analyzed 2.07
aAvailable as slurry containing 30% insoluble solids.
Source: Airco catalog (1969).
31
-------
Carbide lime will also be fed (as a 30% slurry) to the pug mill at a rate
equivalent to a few percent of the combined dry weight of ash and cake.
The carbide lime will be stored in a small day tank in the processing
plant which will be charged from the main plant storage tank.
The pug mills will discharge to radial stacking conveyors. The stackers
will spread the material in a windrow (interim stockpiling area) where it
will remain for one to three days to initiate the stabilization reactions.
The material will be removed from the windrow and loaded into rear dump
trucks using a front-end loader. The trucks will then transport the mater-
ial to a dry landfill south of the plant on LG&E property. Provisions have
also been made to allow direct loading of the trucks from the stacking
conveyors should this mode of operation prove satisfactory.
Installation of the waste processing plant is scheduled for completion
in the fall of 1979. In the interim, the filter cake conveyor will
discharge through a feed chute directly into trucks which will transport
the waste to a temporary storage area. Once the processing plant is
operational, this waste will be reclaimed from the storage area and
processed along with fresh filter cake.
6. Provisions for Spills and Leaks
Filter cake is the only product of the dual alkali system. The system
will be operated in a closed loop and there will be no other solid or
liquid discharge from the system. In order to avoid inadvertent discharge
of any process liquor, a number of provisions have been made in the pro-
cess design.
(a) Drains are provided at all pump stations and inside the
filter building to direct all process pump seal water leaks,
pump and piping flush water and equipment and building wash-
down water to the filtrate sump for return to the thickener
along with the filtrate and cake wash water.
(b) A separate sump is provided to collect vacuum pump seal
water. This is noncontact water. However, should the
vacuum pump seal water become contaminated with process
liquor, provisions have been made to also pump this water
to the thickener.
(c) The emergency overflow from the absorbers are also drained
to the filtrate sump for return to the system.
(d) The thickener has approximately three feet of sidewall above
the overflow weir instead of the usual 6-8 inches; and the
thickener hold tank has a height equal to that of the thickener.
The additional sidewall height in the thickener and hold tank
is to allow for temporary storage of liquor from the other
process vessels in the system if required during maintenance;
32
-------
and to prevent any short-term spills of liquor due to water
imbalances resulting from extreme process upsets. The total
capacity that this additional height provides is equivalent
to the total capacity of all other process vessels in the
system.
(e) The thickener hold tank is equipped with an emergency overflow
tank which will begin to fill when extreme levels have been
reached in the thickener and hold tank. Filling of this
tank will indicate the need for immediate corrective action.
E. MATERIAL BALANCES
Cane Run Unit No. 6 has a rated capacity of 280 Mw and a peak load capacity
of 300 Mw. The system has been designed to handle the peak load, and the
material balances presented here have been calculated for the design con-
ditions unless otherwise specified. The basis for the material balances
is given in Table IV-5. The design coal contains 5% sulfur and 0.04%
chloride on a dry basis. All estimates are based on 94% of the sulfur
in the coal appearing in the flue gas.
1. Overall Material Balance
The overall material balance for the dual alkali system operating at design
conditions is given in Table IV-6. Removal of 94.2% of the 390 Ibs/min
of S02 present in the inlet gas to the scrubbing system generates 1,246
Ibs/min of waste cake. The moisture content of this cake is about 36%.
Lime (as Ca(OH)2) is added to the system at a rate of 460 Ibs/min on a
dry basis. .At 30% insoluble solids in the lime slurry, the slurry
feed rate would equal 1,535 Ibs/min or a total of about 150 gpm. Soda
ash is added at a rate of 13.7 Ibs/min and process water at a rate of
369 gpm.
An overall water balance at design conditions is given in Table IV-7.
Water enters the system in the lime slurry (both as slurry water and
chemically combined water), cake wash, instrument purge, and pump seals.
All the water used for pump seals eventually enters the system. The
water that drains out of the seals is collected in sumps and returned
to the thickener.
More than 75% of the water lost from the system at design conditions is
due to evaporation of water to the flue gas. The amount of water evapor-
ated in the absorbers depends on the boiler load and the temperature and
humidity of the inlet flue gas. Water is also removed from the system
with the waste cake, both as free water and as chemically bound water.
In addition to these losses, which are directly related to process
operations, water enters and leaves the system via liquid surfaces exposed
to the atmosphere (principally the thickener and thickener hold tank).
Based on meteorological conditions at Louisville, thickener and hold tank
configurations and average liquor temperatures, it is anticipated that
33
-------
TABLE IV-5
BASIS FOR MATERIAL BALANCES AT DESIGN CONDITIONS
Coal (dry basis):
Sulfur
Chloride
Heating value
Sulfur volatilized
Inlet Gas;
Flow rate (volumetric)
(weight)
Temperature
S02
°2
Participate Matter
Outlet Gas;
S02
Particulate Matter
Absorber Feed Concentration;
Na+ associated with
OH- and 0)3
803
Oxidation and Sodium Makeup Rates;
Oxidation
Calcium Feed;
Solids in slurry
Available Ca(OH)2
Ca(OH)2 utilization
Waste Solids;
Wash ratio
Insoluble solids
5.0% S
0.04% Cl
11,000 Btu/lb
94% of S in Coal
1,065,000 acfm
3,372,000 Ib/hr
300 8F
3,471 ppm (dry basis)
5.7 vol. %
<0.1 lb/106 Btu
200 ppm (dry basis) (vO.45 lb/106 Btu)
<0.10 lb/106 Btu
0.09 M
0.36 M
10% AS02 (molar basis)
0.045 moles Na+/mdle ASO,
(criteria: <0.0495)
30%
92.5% (weight basis)
98% (equivalent to 1.003 moles available
Ca(OH)2/mole AS02; criteria: <1.01)
2.0 displacement washes
63 wt.% (criteria: £55 wt.!
34
-------
TABLE IV-6
OVERALL MATERIAL BALANCE AT DESIGN CONDITIONS
Basis: Coal - 5.0% sulfur
- 0.04% chloride
- 11,000 Btu/lb
Full load (300 megawatts)
FGD inlet S02 - 390 Ibs/min
S02 removal - 94.2%
Consumption Rate Lbs/lb Coal Fired Lbs/lb S02 Absorbed
w Makeup Materials
Ui
Process Water 369 gpm
Lime (92.5 wt.% Ca(OH)2, dry basis) 460 Ibs/min 0.111 1.25
Soda Ash 13.7 Ibs/min 0.003 0.037
Cake Production
Dry Basis 804 Ibs/min 0.194 2.18
Wet Basis 1,246 Ibs/min 0.300 3.39
-------
TABLE IV-8
Stream No.
Volume, ACFM
Temperature °F
Pressure, inches WG
Dry Gas, #/min
H20 Vapor, #/min
Total Gas, #/min
S02,
S02,PPM (Dry Vol)
Participates , #/min
Stream No.
H70, #/min
Na2C03, ///min
NaOH, #/min
Na2S03, #/min
NaHS03, ///min
Na2S04, #/min
Ca(OH)2, #/min
CaS03 • 1/2 H20, #/min
CaS04 • 1/2 H20, #/min
CaCOj, #/min
Inerts, #/min
CaCl, #/min
Total, #/min
% Solids, #/min
Flow, GPM
PH
Temp, °F
174.9
666.9
1,542.9
445.8
22,764.0
0
2,481.0
4-8
120-140
VTERIAL BALANCE - ABSORBER
I.D. Fan
Outlet
1
532,907
300
+2.0
26,699
1,316
28,015
194.95
3,471
2.48
Spray
Recycle
11
12,919.5
113.4
432.2
1,000.0
288.9
14,754.0
0
1,608.0
4-8
120-140
Absorber
Inlet
2
525,880
303
+11.5
26,699
1,316
28,015
194.95
3,471
2.43
Trav
Recycle
13
7,014.0
61.5
234.7
542.9
156.9
8,010.0
0
873.0
4-8
120-140
SECTION*
Absorber Combustion Exit
Outlet Air Flue Gas
1 A JL
436,516 11,000 487,215
126 60 176
+3.5 AMB +2.0
26,515
2,474
28,989 850 27,839
11.25 11.25
200 200
2.48 2.48
Absorber Feed Tray Emergency
Bleed Forward Feed Spray Water
14 15 16 31
13,642.8 14,828.1 21,867.0 4,582.0
6.8
50.0
119.7 347.2 582.0
456.4 95.0
1,056.0 1,016.3 1,559.2
305.1 303.6 460.5
15,580.0 16,552.0 24,563.7 4,582.0
0 000
1,698.0 1,837.0 27,101.0 550.0**
4-8 7-13 u-11
120-140 120-140 120-140
Reheater
Oil
32
3.0
AMB
For scrubber module
Emergency only, Max. Flow
Combustion Equipment Assoc.
Material Balance
for
Drawing 040O44-1-1 Rev G
See Page 25
-------
MATERIAL BALANCE - REACTOR. SOLIDS DEWATERING AND RAW MATERIALS SECTIONS
Stream Mo.
H20, fl/min
Na2C03, #/rain
NaOH, ///min
Na2S03, #/min
NaHSOj, 0/min
Na2S04, {D/min
Ca(OH)2, ///min
CaS03 • 1/2 H20, #/min
CaS04 • 1/2 H20, #/min
CaCOj, fl/min
Inerts, #/min
NaCl, 0/min
Tocal, f/mln
% Solids
Flow, GPM
pH
Temp, °F
Absorber
Bleed
14*
13,642.8
119.7
456.4
1,056.0
305.1
15,580.0
0
1,698.0
Feed
Forward
15*
14,828.1
6.8
50.0
347.2
1,016.3
303.6
16,552.0
0
1,837.0
Lime Slurry
Pumped
17
2,150.8
852.0
69.2
3,072.0
30.0
305.2
10-14
Reaccor
Lime Feed
18*
537.7
213.0
17.3
768.0
30.0
76,3
7.0
Reactor
Effluent
19*
14,233.0
50.2
349.4
1,019.8
331.0
39.4
5.8
17.3
305.1
16,351.0
2.4
1,785.0
6-13
120-140
Filter
Feed
20
2,103.5
7.3
51.0
143.7
662.0
78.8
11.6
34.6
44.5
3,147.0
25.0
302.0
7-13
120-1 40
Thickener
Overflow
21
29,182.8
13.9
101.3
704.9
2,057.6
615.5
32,676.0
0
3,618.0
7-13
120-140
Cake Wash
Water
22
756.0
756.0
0
91.0
AMB
Stream No.
H20, */min
NajCOj, f/min
NaOH, * /min
Na2S03, */min
NaHS03, 0/rain
Na2S04, »/min
Ca(OH)2, */min
CaS03 • 1/2 ttjO, 0/nin
CaS04 • 1/2 H20, #/min
CaCOj, #/min
Inerts, I/rain
NaCl, */min
Tocal. 9 /min
% Solids
Flow, GPM
PH
Temp "F
Cake
23
442.1
0.50
3.4
10.0
662.0
78.8
11.6
34.6
3.00
1,246.0
fil.l
Filtrate
24
2,421.4
6.8
47.5
138.8
41.5
2.656.0
n
299.0
7-13
120-140
Soda Ash Soda Ash
Solution Feed
25 26
403.9
13.9 13.7
1.4
9.6
27.9
8.3
465.0 13.7
n
50.0
8-14
120-140
Soda Ash
Solution Make-up Lime Slurry
Liquor Water Recycle
27 28 29
403.9 878.0 1,075.4
0.2
1.4
9.6
27.9
426.0
34.6
8.3
451.3 878.0 1.536.0
30.0
50.0 105.0** 152.6
7-13
120-140 AMB
Underflow Slurry River Water
Dilution Liquor (Startup)
30 33
250.0*** 135.0 max
7^13
120-140
Per module
Includes waCer entering process
from pump seals
Intermittent Maximum
Combustion Equipment Assoc.
Material Balance
for
Drawing 040044-1-2 Rev G
See Page 26
-------
rate of oxidation of 10% of the SO^ removed. The sulfite and sulfate
concentrations indicated in Table IV-5 are consistent with the level
required to precipitate sulfate as a calcium salt in balance with 10%
oxidation rate (taking into account losses of Na2S04 in the washed cake).
The total active sodium concentration in the feed forward to the absorbers
is set at 0.45 M ([Na2S03] = 0.18 M, [NaOH] = 0.08 M, and [Na2C03] =
0.005 M). At a 10% level of oxidation and a high wash ratio, this
results in an estimated Na2S04 concentration of 0.47 M. The NaCl con-
centration estimated in. the feed forward liquor is 0.34 M. This repre-
sents the steady-state level at which the rate of NaCl loss in the
washed cake is equivalent to the chloride absorbed from the gas
(1.8 Ibs/min).
The feed forward rate of the regenerated liquor from the thickener hold
tank to the absorber is controlled by the pH of the absorber bleed. At
design conditions the absorber bleed pH is assumed to be 6. At this
pH the absorber bleed will contain 0.31 M NaHS03 and 0.07 M Na2S03.
The Na^SO^ concentration in the bleed is increased to 0.52 M. The
changes in the concentrations in the outlet and the inlet streams reflect
10% oxidation, absorption of 368 Ibs/min of the S02 (both absorbers),
and changes in the stream volumetric flow rate due to the evaporation
of water in the absorbers.
The design feed rate to the two primary reactors is about 3,400 gpm of
spent absorber liquor (1,700 gpm to each reactor). Lime slurry containing
30% solids is also fed to the reactors at a rate of 152 gpm (76 gpm
to each reactor). The calcium hydroxide available in the solids is
taken as 92.5%. Thus, the total feed of available calcium hydroxide to
the two primary reactors is 426 Ibs/min. This rate is equivalent to
1.00 moles of calcium hydroxide per mole of S02 removed in the absorbers.
The liquor from the primary reactor overflows into the secondary reactor
where regeneration of scrubbing solutions is completed.
The composition of the liquor in the secondary reactor is dependent on
the degree of regeneration. For design purposes, the secondary reactor
is assumed to operate at a pH of 12. At this pH the regeneration reactions
are carried beyond neutralization and some sodium hydroxide is formed.
The composition of the secondary reactor liquor is: [NaOH] = 0.085 M,
[Na2S03] = 0.19 M, and [Na2SO^] = 0.48 M. The soluble calcium concentra-
tion in the liquor is less than 100 ppm. The liquor also contains
sulfite/sulfate solids, inerts and a small amount of unreacted lime.
The overall solids concentration in the slurry is 2.3%. The composition
of the solids is estimated to be approximately 1% unreacted lime, 5%
inerts (from the carbide lime slurry), 94% mixed calcium sulfite/sulfate
solids (about 84% as calcium sulfite and 10% as calcium sulfate). The
composition of these insoluble solids is essentially the composition of
the insoluble solids in the waste cake.
40
-------
The liquor from the two secondary reactors is pumped at a combined rate
of 3,570 gpm to the thickener center well where the solids are allowed
to settle. The underflow slurry is recycled around the thickener and
a bleed from this recirculation loop is sent to the filters. The con-
centration of solids in the underflow slurry from the thickener is
controlled at about 20-25% solids.
The filters are operated on overflow with the slurry level in the filter
tubs controlled by the position of the overflow weir. At design load,
the total slurry feed to the filters is 300 gpm and contains approximately
2,500 Ibs of insoluble solids/hour (assuming 20% insoluble solids). About
60% of the total slurry fed to the filters is returned in the overflow
to the thickener. The solids are filtered, forming a cake which is washed
with water to remove sodium salts in the liquor entrained in the cake.
The design wash rate is 90 gpm, which corresponds to a wash ratio of
about 2.0 (volume of wash water/volume of entrained liquor). The com-
bined filtrate (wash water and recovered liquor) is returned to the
thickener. The washed cake is discharged at a rate of 1,246 Ibs/min
from the filter drum. The washed filter cake is estimated to contain
63 wt.% insoluble solids and about 1.3 wt.% soluble salts.
The soluble salts amount to 2.1% of the total solids present. NaCl
accounts for about 40% of these solubles.
Clarified, regenerated liquor (including filtrate and wash water) over-
flows the thickener at the rate of about 3,600 gpm to the thickener hold
tank from which it is pumped to the absorbers. Clarified liquor is also
used to make up soda ash solution.
In this material balance, soda ash solution is shown as fed to the
thickener, although the capability exists for feeding soda ash solution
directly to the absorbers. The rate of soda ash makeup required to
replace the sodium value lost in the cake is 13.7 Ibs/min, equivalent
to 2.3% of the S02 absorbed on a molar basis.
Based upon the total soda ash and lime feed rates, the overall system
alkali stoichiometry is estimated to be 1.02 (moles of available CaO +
Na2C03)/(mole of AS02 + AC12).
F. OPERATING AND CONTROL PHILOSOPHY
The development of the operating guidelines for the dual alkali system
has been based on the minimization of operator interface to control and
operate the system under varying conditions, mainly boiler load and
sulfur content of the coal.
Detailed piping and instrumentation diagrams* (P&ID's) are given in CEA
drawings 040044-1-1,3,4,5, and 6. It should be noted that instrument
"*A~set of large size CEA drawings may be obtained from the IERL Project
Officer at the Environmental Protection Agency, Research Triangle Park,
North Carolina. Because of the level of details in these drawings, they
cannot be reduced, and therefore they are not included here.
41
-------
redundancy or a backup system has been provided for all principal control
loops. This includes fan controls, tank level controllers and indicators,
and process liquor pH controllers.
The basic control philosophy for the four major process sections—absorber,
reactor, solids dewatering, and raw materials handling—is discussed below.
1. Absorbers
The operation and control of the absorber section can be conveniently
divided as it applies to the gas streams and the process liquors.
The control philosophy for this section of the system is summarized in
Table IV-10.
a. Gas
Flue Gas Flow
The control of flue gas flow to the absorbers is based upon maintaining
balanced pressure at the boiler I.D. fans. The control parameter therefore
is the discharge pressure of the I.D. fans. A pressure indicating con-
troller maintains this pressure in the range of -0.5 to 1.0 inches W.G.
(depending upon boiler load) by adjusting the speed of the dual alkali
system booster fans. One pressure controller is used. The signal is
sent to each booster fan speed controller through a precalibrated bias.
The bias adjusts the signal/response to account for mechanical differences
in the two booster fan fluid drive units and effect equal speeds on both
fans and parallel fan tracking of boiler load.
Normally both absorbers and fans are operated together with each train
taking half the boiler load. However, a common duct between the booster
fan discharges and appropriate dampers provide the flexibility of operating
only one absorber at low boiler load (<60% load). This allows for main-
tenance on one absorber module while the system remains in service.
Flue Gas Reheat
Flue gas reheat is provided through injection of heated air/gas into
the saturated absorber discharge. The heated air/gas is generated by
combining ambient air with combustion gas from a No. 2 oil-fired burner.
The operation of the burner is controlled based upon the degree of flue
gas reheat as measured by the differential temperature between the
reheated gas and saturated absorber discharge. The differential tempera-
ture controls both the burner oil and combustion air fans to provide
the preset degree of reheat (usually 50F°).
The dilution air which is mixed with the burner combustion gases is
normally maintained at a constant rate regardless of load.
42
-------
TABLE IV-10
Controlled
Variable
Gas:
Flue Gas Flow
Reheater Oil Flow
Process Liquor:
Feed Forward Flow
Soda Ash Feed Flow
Tray Recycle Flow
Spray Recycle Flow
Absorber Bleed Flow
*
Total Flow
Approximate
Variable Range
(per absorber)
106,000-533,000 acfm
0-3.0 gpm
280-1850 gpm
*
0-100 gpm
260-870 gpm
1600 gpm
260-1700 gpm
CONTROL PHILOSOPHY FOR THE ABSORBER SECTION
Controlled
By Control Function Control Parameter
Fan Speed Gas Flow Balance Fan Suction Pressure
CV-56 Reheat Scrubbed Gas Gas Differential Temperature
CV-3/CV-26 SO- Removal Bleed Liquor pH
CV-60/CV-61 Sodium Makeup Flow
CV-2/CV-25 Top Tray pH Flow
Tray Loading at Low Flow
Gas Quench Manual
CV-4/CV-27 Flow Balance Absorber Tank Level
Parameter
Range Control Tag
-1.0-0.5" W.G. DF-101/DF-102
0-50°F TIC-l/TIC-2
FFIC-l/FFIC-6
0-100 gpm Manual (FIC-2)
260-870 gpm Manual
(FIC-l/FIC-3)
Manual
A '-5' LIC-l/LIC-6
-------
Emergency Water Sprays
Emergency water sprays are provided on the inlet ducting to each absorber
to protect the absorber linings from temperature excursions. These
emergency sprays are designed to quench the incoming flue gas in the
event of a failure of the spray system. The sprays are activated either
by a high temperature reading in the absorber discharge gas or low flow
in the spray recycle line.
b. Process liquor
The removal of SC>2 from the flue gas is the basic function of the absorber.
Consequently, the principal control parameter for operation of the absor-
bers is the amount of SC>2 removed. Since the pH of the bleed liquor can
be accurately related to the amount of SC>2 removed, it can be used to
provide this control. Additional control parameters for the absorbers
include the flow of the recycle streams as well as the bleed stream.
Absorber Bleed pH/Feed Forward Flow Rate
The feed forward of regenerated alkaline, scrubbing solution to the
absorber is determined by the pH of the absorber bleed liquor. The flow
is adjusted to maintain the bleed liquor pH within the range prescribed
by the required S02 concentration in the exit flue gas. Initially the
bleed pH will be controlled to a value of about 6, which is estimated
will result in an 862 concentration in the exit gas of less than 200 ppm.
The actual correlation between pH and SC>2 removal will be determined
during the early periods of operation and the actual set points modified
accordingly. The option exists for operating the absorber feed forward
rate on flow control with manual adjustment of the flow set point. This
may be required during periods of maintenance on the bleed liquor pH
monitors.
Soda Ash Makeup
An additional stream that feeds the absorbers is the soda ash makeup
solution. This solution, at a constant flow rate (usually 50 gpm) ,
is directed to either the thickener or the absorbers. The principal
mode of operation is to feed soda ash solution to the absorbers. If
both absorbers are in operation, it is distributed equally between them.
While the total flow of soda ash solution is maintained on flow control,
the distribution of solution to either or both absorbers is manually
adjusted. Soda ash flow can be switched to the thickener during periods
of abnormally high soda ash makeup rates, which would affect the bleed
liquor pH. Further details on the control of the preparation of the
soda ash makeup solution are given in the discussion of raw materials
handling.
44
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Tray Recycle
The tray recycle flow rate is normally controlled at 650 gpm (range of
260-870 gpm). Given the varying feed forward rate, the tray recycle
is needed to insure a proper liquid loading of the trays. It also
reduces the pH of the total liquor fed to the tray, thus minimizing
C02 absorption and the potential for CaCO, precipitation. The pH of
the tray feed (combined tray recycle and feed forward) will normally
fluctuate within the range of 7.5-10.5. The set point for the tray
recycle flow rate may be changed to maintain the pH within this range;
however, such adjustments would normally be required only if the pH
falls outside the range for extended periods of time (a few hours or
more). Hence, the pH of the combined liquor feed to the top tray is
monitored and alarmed, but is not used for automatic control of the
recycle flow. The flow is maintained in flow control and is adjusted
manually as required. Increasing the recycle flow rate will lower the
pH of the combined stream; decreasing the recycle flow rate will have
the opposite effect.
Spray Recycle
The spray recycle plays the important role of quenching the incoming
flue gas and protecting the absorber lining. The sprays are operated
at a constant flow rate of 1,600 gpm independent of boiler load. The
flow rate is manually controlled when required by the appropriate adjust-
ment of the spray recycle valve position.
Absorber Bleed Stream
The flow rate of the bleed stream is controlled by the liquid level in
the absorber tank, which is normally maintained at a height of 4.5 ft
(range 4-5 ft). The flow rate of the bleed stream is expected to vary
within 260-1,700 gpm over the full range of boiler load and coal sulfur
content. The option exists for operating the absorber bleed rate on
flow control with manual adjustment of the flow set point. This would
be required during periods of maintenance on the absorber level control
loop.
2. Reactor Section
The optimal operation of the reactor system involves controlling the
extent of regeneration scrubbing solution to maximize lime utilization
and produce waste solids with good dewatering characteristics. The
pH of the secondary reactor bleed stream is a measure of the extent of
regeneration and thus becomes the controlling factor in this step. A
summary of the control philosophy for the reactor section is given in
Table IV-11.
45
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TABLE IV-11
CONTROL PHILOSOPHY FOR THE REACTOR SECTION
Control Variable
Primary Reactor
Bleed Flow
Variable Range
(per reactor train)
270-1800 gpm
Controlled
By
Overflow
Control Function
Reaction Time/
Flow Balance
Control
Parameter
Tank Level
Parameter
Range Control Tag
12 ft
Overflow
Secondary Reactor
Bleed Flow
270-1800 gpm
CV-ll/CV-14 Reaction Time/
or Overflow Flow Balance
Tank Level
18-30 ft
LIC-2/LIC-3
or Overflow
Lime Feed Rate
30-120 gpm
CV-12/CV-13
Solid Waste
Properties/Lime
Utilization
Second Reactor
Bleed Liquor pH
11-12.5 ft AIC-l/AIC-2
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a. Individual Reactor Controls
Tank Level/Effluent Flow - Primary Reactors
The absorber bleed streams are mixed with carbide lime in the primary
reactors and subsequently overflow into the secondary reactors. Thus,
the tank level in the primary reactor is constant at the overflow level,
and the effluent flow rate is the same as the combined feed of absorber
bleed and carbide lime slurry. The hold-up time in these reactors is
dictated by the flow rate of the combined feed streams. The normal
operating range for the hold-up time is 3-10 minutes.
Tank Level/Effluent Flow - Secondary Reactors
Each of the secondary reactors is provided with one reactor transfer
pump and an overflow line. Thus, the effluent (or bleed) from the sec-
ondary reactors can be fed to the thickener either by pumping it on level
control or by allowing the tank to operate on overflow. In either case,
the secondary reactors are normally operated at hold-up times greater
than 30 minutes.
Under typical conditions of boiler load and coal sulfur content, it is
expected that the secondary reactors will be operated on overflow (level
of 30 ft). The flexibility is also provided to operate the secondary
reactors at lower liquid levels by using the reactor transfer pumps
(with flow controlled on liquid level). This allows adjustment of
secondary reactor hold-up times if desired during sustained periods
of extremely low boiler loads. The pumps are also used to drain the
reactors if they are to be taken out of service for maintenance.
Bleed pH/Lime Slurry Feed
The amount of lime fed to the primary reactor of each train is controlled
by the pH of the corresponding secondary reactor bleed stream. The bleed
pH is automatically controlled within the range of 11-12.5 (initial set
point of 12) by adding more lime to increase the pH or reducing the
lime feed to decrease it.
There are occasions, however, when it is desirable to override pH control
to prevent overfeeding of lime. This could occur, for example, whenever
there is a rapid and significant change in boiler load or coal sulfur
content, or the pH of the secondary reactor experiences a rapid drop due
to some upset condition. Under such circumstances, it is very likely
that lime will be overfed to the primary reactors for some period of
time since the lag time for pH sensors to detect the effect of lime
addition is greater than one-half hour (primary plus secondary reactor
hold-up times).
47
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To avoid this problem a maximum lime feed rate controller has been provided.
It sets a limit on the lime feed rate which is based in direct proportion
to the absorber bleed stream flow. Thus, the secondary reactor bleed pH
controls the lime feed rate as long as this feed rate does not exceed
the maximum rate established by the overriding controller. In the event
that only one reactor train is in operation but both absorbers are operating,
the maximum lime feed rate to the single reactor train is proportional
to the sum of both absorber streams. This is accomplished automatically
when placing a single reactor train in service.
b. One vs. Two Reactor Train Operation
The number of reactor trains in operation will generally be dictated by
the boiler load and the sulfur content of the coal. Normally, with
typical coal (^3.5% S) only one reactor train is required with the sec-
ondary reactor usually operated on overflow.
It is highly desirable, of course, to minimize switching between one and
two reactor train operation. Momentary upsets or short-term changes in
boiler loads therefore are not considered as a basis for changing the
number of trains in operation. However, during sustained periods of
operation (more than three to four hours) with the boiler firing coal
having a sulfur content of greater than about 4.0% (>3000 ppm S02 in
flue gas - dry basis) operation of both reactor trains would be desirable
unless the boiler load is consistently low (less than about 70%). Short-
term low load conditions (either with one or two trains in service) can
usually be accommodated if necessary by simply switching from operation
of the secondary reactor in overflow mode to level control (and possibly
readjusting the pH setpoint).
As indicated in the discussion of lime feed rate control, whenever the
number of reactor trains is changed, the absorber bleed flow totalizer
is automatically activated accordingly.
3. Solids Separation
The separation of the solid wastes from the regenerated scrubbing solution
is accomplished in a two step operation: thickening of the slurry followed
by vacuum filtration. A summary of the control philosophy for the solids
separation section is given in Table IV-12.
a. Slurry Thickening
Thickener
The reactor effluent fed to the thickener contains 2-5% solids. The
thickener is generally operated to provide a slurry underflow containing
20-25% solids. This solids concentration provides for reasonable control
of the filter operation. The solids generated in the reactor system
settle very well and will normally thicken to a much higher solids level,
up to 40% or more, if not controlled. Hence, clarified liquor from the
48
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a. Individual Reactor Controls
Tank Level/Effluent Flow - Primary Reactors
The absorber bleed streams are mixed with carbide lime in the primary
reactors and subsequently overflow into the secondary reactors. Thus,
the tank level in the primary reactor is constant at the overflow level,
and the effluent flow rate is the same as the combined feed of absorber
bleed and carbide lime slurry. The hold-up time in these reactors is
dictated by the flow rate of the combined feed streams. The normal
operating range for the hold-up time is 3-10 minutes.
Tank Level/Effluent Flow - Secondary Reactors
Each of the secondary reactors is provided with one reactor transfer
pump and an overflow line. Thus, the effluent (or bleed) from the sec-
ondary reactors can be fed to the thickener either by pumping it on level
control or by allowing the tank to operate on overflow. In either case,
the secondary reactors are normally operated at hold-up times greater
than 30 minutes.
Under typical conditions of boiler load and coal sulfur content, it is
expected that the secondary reactors will be operated on overflow (level
of 30 ft). The flexibility is also provided to operate the secondary
reactors at lower liquid levels by using the reactor transfer pumps
(with flow controlled on liquid level). This allows adjustment of
secondary reactor hold-up times if desired during sustained periods
of extremely low boiler loads. The pumps are also used to drain the
reactors if they are to be taken out of service for maintenance.
Bleed pH/Lime Slurry Feed
The amount of lime fed to the primary reactor of each train is controlled
by the pH of the corresponding secondary reactor bleed stream. The bleed
pH is automatically controlled within the range of 11-12.5 (initial set
point of 12) by adding more lime to increase the pH or reducing the
lime feed to decrease it.
There are occasions, however, when it is desirable to override pH control
to prevent overfeeding of lime. This could occur, for example, whenever
there is a rapid and significant change in boiler load or coal sulfur
content, or the pH of the secondary reactor experiences a rapid drop due
to some upset condition. Under such circumstances, it is very likely
that lime will be overfed to the primary reactors for some period of
time since the lag time for pH sensors to detect the effect of lime
addition is greater than one-half hour (primary plus secondary reactor
hold-up times).
47
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To avoid this problem a maximum lime feed rate controller has been provided.
It sets a limit on the lime feed rate which is based in direct proportion
to the absorber bleed stream flow. Thus, the secondary reactor bleed pH
controls the lime feed rate as long as this feed rate does not exceed
the maximum rate established by the overriding controller. In the event
that only one reactor train is in operation but both absorbers are operating,
the maximum lime feed rate to the single reactor train is proportional
to the sum of both absorber streams. This is accomplished automatically
when placing a single reactor train in service.
b. One vs. Two Reactor Train Operation
The number of reactor trains in operation will generally be dictated by
the boiler load and the sulfur content of the coal. Normally, with
typical coal (^3.5% S) only one reactor train is required with the sec-
ondary reactor usually operated on overflow.
It is highly desirable, of course, to minimize switching between one and
two reactor train operation. Momentary upsets or short-term changes in
boiler loads therefore are not considered as a basis for changing the
number of trains in operation. However, during sustained periods of
operation (more than three to four hours) with the boiler firing coal
having a sulfur content of greater than about 4.0% (>3000 ppm S02 in
flue gas - dry basis) operation of both reactor trains would be desirable
unless the boiler load is consistently low (less than about 70%). Short-
term low load conditions (either with one or two trains in service) can
usually be accommodated if necessary by simply switching from operation
of the secondary reactor in overflow mode to level control (and possibly
readjusting the pH setpoint).
As indicated in the discussion of lime feed rate control, whenever the
number of reactor trains is changed, the absorber bleed flow totalizer
is automatically activated accordingly.
3. Solids Separation
The separation of the solid wastes from the regenerated scrubbing solution
is accomplished in a two step operation: thickening of the slurry followed
by vacuum filtration. A summary of the control philosophy for the solids
separation section is given in Table IV-12.
a. Slurry Thickening
Thickener
The reactor effluent fed to the thickener contains 2-5% solids. The
thickener is generally operated to provide a slurry underflow containing
20-25% solids. This solids concentration provides for reasonable control
of the filter operation. The solids generated in the reactor system
settle very well and will normally thicken to a much higher solids level,
up to 40% or more, if not controlled. Hence, clarified liquor from the
48
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TABLE IV-12
CONTROL PHILOSOPHY FOR THE SOLIDS SEPARATION SECTION
Slurry Thickening
Thickener Underflow
Recycle Flowrate
Dilution Liquor
Flow Rate
Makeup River Water
Flow Rate
Variable
Range Controlled By
250-600 gpm
0-260 gpm
50-150 gpm
CV-17
CV-24
Control Function
Prevent Solids
Deposition
Suspended Solids
Concentration
Maintain System
Water Balance
Parameter Control
Control Parameter Range Tag
Underflow
Specific Gravity
Hold Tank Level
Manual
1.20-1.26 DIC-1
8-16' LIC-14
Dewatering
Drum Speed
Drum Submergence
Wash Water Flow Rate
Filtrate Sump
Recycle
0.8-1.2 rpm
8-10"
40-180 gpm
50-700 gpm
Filtration Rate
Weir position Filtration Rate
Minimize Na Losses
CV-53
Flow Balance
Cake Thickness
Cake Thickness
1/4-1/2" Manual
1/4-1/2" Manual
Manual
Filter Sump Level
2.5-51
LIC-9
Per filter
-------
hold tank is used to control the solids level in the thickener underflow
that is pumped to the filters. A density sensing element is located at
the discharge of the underflow pumps to measure the slurry concentration
and adjust the rate of dilution liquor addition in order to maintain a
specific gravity consistent with 20-25% solids. Part of the slurry is
recirculated past the filters and returned to the solids zone in the
thickener in order to maintain flow through the lines, thus preventing
solids deposition. The underflow and recycle flow rates are manually
set by the appropriate opening of the corresponding valves.
Thickener Hold Tank
The clarified liquor from the thickener overflows into the hold tank.
Makeup river water, required to maintain the water balance in the system,
is fed to the hold tank on level control. The hold tank liquor, which is
regenerated scrubbing solution, is pumped to the absorbers. As previously
indicated in the absorber section, the flow rate of the feed forward to
each absorber is controlled by the pH of the absorber bleed stream.
b. Vacuum Filtration
Filter Units
The most important factors in assessing filter performance are the solids
content and the level of sodium salts contained in the filter cake (i.e.,
solids dewatering and washing). These are primarily a function of the
quality of the solids produced in the reactor system, the thickness of
the filter cake and the amount of cake washing. In general, optimal
performance is achieved with a cake thickness of about 3/8 inch (a range
of 1/4-1/2 inch) and a wash ratio in the range of 1.5 to 3.0 (gals of
wash water/gal of water in the filter cake). The wash water rate, therefore,
would be a function of the rate of discharge of wet cake and the moisture
(or solids) content of the cake. Since the solids content varies only
slightly and the drum speed is usually fixed, the wash water flow rate
can be preset as long as cake thickness is controlled in the proper
range. If necessary, it can be readjusted based upon the weight of cake
produced as measured by the conveyor belt weigh element. The wash
flow rate to each filter is initially set at 120 gpm.
The cake thickness is controlled by four parameters, three of which are
preset: drum speed (1.0 rpm), drum submergence (8-10 inch), and the
filter bridge valve position (6 o'clock). The fourth parameter, the
underflow slurry concentration, is used as the primary control parameter
to maintain proper cake thickness. As indicated in the thickener section,
the slurry concentration is kept at a suspended solids level of about
20-25%. However, when the slurry concentration deviates appreciably from
this range and cannot be further adjusted by dilution liquor, operator
interface is required to either put filters in service or take them off
line.
50
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Number of Filter Units in Service
The number of filters in operation is dictated by the thickener underflow
slurry concentration and the amount of diluting hold tank liquor added.
Whenever the dilution liquor has been automatically reduced to its mini-
mum rate and the slurry concentration is below about 15%, a filter needs
to be taken off line. Similarly, when the dilution liquor rate is at its
maximum and the slurry concentration exceeds about 28%, a filter needs
to be put in service.
Filtrate Sump
The filtrate is collected in filtrate receivers and directed to the fil-
trate sump from which it is pumped to the thickener. The filtrate sump
is maintained at a constant level by controlling the flow in the sump
recycle stream. The excess fluid goes to the thickener.
4. Raw Materials
The dual alkali process requires the addition to the system of two raw
materials: carbide lime and soda ash makeup. A summary of the control
philosophy for the raw materials handling and feed systems is given in
Table IV-13.
a. Carbide Lime
Lime Feed to Day Tank
Carbide lime is available to LG&E as a slurry containing 25-30% insoluble
solids. The lime for the dual alkali system is stored in a day tank which
is filled batchwise as the slurry level drops below the preset point.
Initially, the preset level corresponds to about 60% of the tank capacity
and requires one or two fillings per shift. The preset level may be
changed, however, and the contents of the lime tank may be allowed to
drop as low as 25% of the tank capacity before proceeding to refill it.
Lime Tank Recycle
The amount of lime added to the primary reactors is controlled by the pH
of the corresponding secondary reactors with override limitation on maxi-
mum feed based upon absorber bleed flow, as previously discussed. The
lime slurry is recirculated around the lime feed tank to maintain sufficient
flow through the pipes to prevent solids deposition. A bleed from this
recycle is fed to the primary reactors. A control valve on the day tank
return line is interconnected with the control valves on the lime slurry
feed to the individual reactors. The recycle valve is used to maintain
enough pressure in the feed lines to each primary reactor to ensure
sufficient slurry feed and adequate feed control. The valve position on
the slurry return line to the day tank is controlled by the larger of
the flows to each of the primary reactors. As the larger of the reactor
feed rates increases (decreases), the control valve on the return line
closes (opens) to maintain the feed line pressure consistent with a rea-
sonable range of operation for the feed control valves.
51
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TABLE IV-13
CONTROL PHILOSOPHY FOR THE RAW MATERIALS SECTION
Control
Variable
Carbide Lime
Lime Feed
Lime Recycle
Variable
Range
Batch
150-285 gpm
Controlled
By
CV-7
CV-8
Control
Function
Sufficient Lime
Inventory
Prevent Solid
Deposition/Enough
Pressure Rxtr Feed
Control
Parameter
Lime Tank Level
Primary Reactor
Feed
Parameter
Range
150-285 gpm
Control
Tag
VPC-1
Soda Ash
Soda Ash Feed
Hold Tank
Liquor Flow
Soda Ash
Solution Flow
40-80 tons
every week
30-60 gpm
30-60 gpm
Batch
CV-22
CV-23
Sufficient Soda
Ash Inventory
Soda Ash
Solution Liquor
Flow Balance
Soda Ash Silo
Level
Flow Rate
Soda Ash Tank
Level
12 '-30'
30-60 gpm
4'-6'
Manual
FIC-2
LIC-5
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b. Soda Ash
Soda Ash Silo
Dense soda ash is received and stored in the soda ash silo, which has a
capacity of approximately 140 tons. Maintaining the silo inventory will
normally require two to four 20-ton trucks every week, depending on the
system demand.
Soda Ash Solution Tank
The soda ash is fed to the soda ash solution tank by means of a weigh
feeder. The amount fed can be set manually and readjusted daily or
weekly as required; or it can be controlled automatically in proportion
to the amount of lime fed to the reactor system. (The amount of lime
fed dictates the amount of waste cake produced and ultimately the rate
of soda ash lost in the washed cake.) On automatic control, the bias
in the controller would be adjusted periodically (about once a week)
to maintain a constant thickener overflow liquor specific gravity.
If the specific gravity is increasing, the soda ash should be decreased.
Similarly, if the specific gravity is decreasing, the soda ash feed
should be increased.
Soda ash solution is normally prepared using clarified liquor from the
thickener hold tank. Solution liquor from the hold tank is pumped
(from the discharge of the hold tank pumps) to the soda ash solution
tank at a constant rate, nominally 50 gpm. The resulting soda ash
solution is pumped to the absorbers or to the thickener on level
control. This operation is described in more detail in the Absorber
Section.
53
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V. DUAL ALKALI PLANT CONFIGURATION AND EQUIPMENT
A. PLANT LAYOUT
Cane Run Unit No. 6, the last and largest of six boilers at the Cane
Run Station, is located at the north end of the plant complex. A photo-
graphic overview of the north end of the plant in Figure V-l shows the
boiler/turbine house, the two parallel electrostatic precipitator sec-
tions and exhaust stack of Unit No. 6 and the dual alkali facility. The
two 862 absorbers have been installed behind the precipitators one on
each side of the stack. The chemical plant consisting of the reactor
system, dewatering equipment, and raw materials preparation areas are
sited north of the boiler and scrubbers. Figure V-2 shows more detail
on the gas ducting and reheaters.
The building shown behind the thickener houses the filters and associated
filtration equipment; the reactor, lime feed, and hold tank pumps, and
the system sumps. The two reactor trains are located next to and are
accessed from the filter building. The soda ash silo and soda ash solu-
tion tank are located in the north-east corner of the facility, adjacent
to the thickener in the foreground of Figure V-l. The thickener overflow
tank is located between the thickener and the filter building; and the
lime feed day tank is located behind the filter building.
The relative location of the reactor trains and the lime slurry tank is
shown in more detail in Figure V-3. The elevation of the primary reac-
tors , secondary reactors, and thickener is designed to allow operation
of the regeneration system completely in an overflow mode.
The general plot plan for the dual alkali system is given in Drawing No.
040044-2-03. General arrangements of the various parts of the system
are given in the following drawings: absorbers, lower and upper plans—
040044-2-1/040044-2-4; thickener, hold tank, and soda ash silo plan—
040044-2-5; reactors and vacuum filter building plan—040044-2-6; absorber
sections—040044-2-8/040044-2-9; thickener hold tank and silo sections—
040044-2-10; and reactors and vacuum filter building sections—040044-2-11.
B. PROCESS EQUIPMENT
The following is a brief description of the major pieces of equipment.
Further details and specifications can be found in the appendix.
A set of large size CEA drawings may be obtained from the IERL Project
Officer at the Environmental Protection Agency, Research Triangle Park,
North Carolina. Because of too many details, these drawings cannot be
reduced; and therefore, are not included here.
54
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01
Figure V-l: Overall View of Cane Run Unit No. 6 and the Dual Alkali System
-------
Figure V—2: Gas Reheaters and Absorber Ducting
-------
Figure V-3: Overall View of the Chemical Plant
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1. Absorbers
Each absorber is a carbon steel vessel, cylindrical in shape and with
a conical head. The overall height of the absorbers including the over-
head discharge duct is 75 ft. The absorbers themselves are 55 ft high
and 32 ft in diameter. The vessels are internally coated with reinforced
polyester lining.
The internals of each absorber consist of an array of spray nozzles, two
trays, and one demister. The sprays beneath the bottom trays are con-
structed of fiberglass headers with 316 stainless steel nozzles. The
trays in each absorber are fabricated out of 317L stainless steel. At
design conditions these trays have a liquid loading of 4.0 gallons/1000
acf. The pressure drop across these trays is 4-6 inches W.G. and the
overall gas pressure drop through the dual alkali system is less than
9.5 inches W.G. The four pass, chevron type, mist eliminators are made.
of noryl.
An 11 ft 8 in carbon steel duct takes the flue gas discharged by each
of the two parallel boiler induced draft (I.D.) fans and directs it
to the corresponding booster fan. Each booster fan is fabricated out of
A441 steel, and is driven by a 1250 HP motor with fluid drive speed
control. The gas exits the fans and enters the absorbers through a 13 ft
10 in duct. The ducts to the two booster fans are interconnected by the
by-pass duct. Five dampers provide flexibility in the operation of the
absorbers. Each booster fan inlet has an A36 steel, guillotine type,
damper to isolate the corresponding absorber while the flue gas is desul-
furized by the other absorber. In addition the flue gas may by-pass
entirely the FGD system by opening the multi-louver 316L stainless steel
by-pass damper while keeping the booster fan and absorber outlet duct
dampers closed. Each outlet duct from the absorbers 13 ft in diameter,
has a 316L stainless steel, guillotine type, damper which is always
maintained at the same position, open or closed, as the corresponding
booster fan inlet damper. All the ductwork carrying saturated flue gas
from the scrubber to the reheater is made of carbon steel, internally
coated with reinforced polyester lining. The ductwork carrying reheated
flue gas from the reheater to the stack is made of 317L stainless steel.
The continuous recycle flow through the sprays and trays, essential for
operation of the absorbers, is ensured by a back-up pump provided for
each absorber. Provisions have also been made to bring the back-up pump
on-line, in case of failure of the primary pump without shutting the
absorber down. The pumps are made of rubber lined cast iron and the
process piping is made of fiber reinforced plastic (FRP).
2. Reactors
The primary reactors are cylindrical tanks, 11 ft in diameter and 14 ft
in height, constructed of 316L stainless steel and equipped with a pitched
blade turbine agitator driven by a 7.5 HP motor. The primary reactors are
top fed from a 12-in line for the absorber feed and a 3-in line for the
lime reactant slurry.
58
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The overflow conduits from the primary to the secondary reactors have been
specially designed. Each conduit is a trough, trapezoidal in cross
section, with a removable top which allows easy access to the duct for
cleaning purposes, if required.
The secondary reactors are also cylindrical tanks 20 ft in diameter and
33 ft in height. The tanks are constructed of carbon steel lined with
glass reinforced polyester. Each reactor is equipped with a pitched-
blade turbine agitator driven by a 25 HP motor and a transfer pump to
direct the slurry product to the thickener. The transfer pumps are made
of rubber lined cast iron. A 24-in overflow port that feeds directly
to the thickener is also available for operation of the reactors in an
overflow mode.
3. Solids Dewatering
The thickener is a tank 125 ft in diameter and 23 ft in height with a
carbon steel shell and concrete bottom. Both shell and bottom are lined
with glass reinforced polyester. The outer wall of the thickener extends
3 ft above the overflow weir providing a surge capacity equivalent to
the capacity of all other tanks in the system to allow storage of the
total system liquor and to provide capacity for temporary water balance
upsets.
The solids at the bottom of the thickener are swept by a rake driven by
a 5 HP motor. The position of the rake is adjusted for the accumulation
of solids at the bottom by a 3 HP rake lifting motor. The center feed
well extends half-way down the tank and is 12 ft in diameter. Both
the rake and the center feed well are made of rubber covered carbon
steel.
The clarified liquor overflows through a 30-in line to the thickener hold
tank. The hold tank is a cylindrical vessel 36 ft in diameter and 23
ft in height made of carbon steel and lined with glass reinforced poly-
ester. A rubber lined cast iron pump is used to transfer liquor from
the hold tank to the absorber. This pump also supplies dilution liquor
to the thickener underflow slurry as well as solution liquor to the soda
ash make-up solution tank, A back-up pump is provided for this operation.
The thickener underflow slurry is pumped in a recirculation loop back
to the thickener. (A back-up pump is provided.) A bleed from this
recirculation loop is fed to the filters. Final dewatering of the
waste cake takes place in the three vacuum filters. The filtering
surface in these filters is a rotating drum 8 ft in diameter and 16 ft
in length. A blow back fan and a rubber tipped 317 stainless steel
scraper is used to discharge the cake. The slurry in the filter tub
is agitated by a counter weighted rocker arm and the slurry level is
controlled by an adjustable overflow weir. The drum and agitator are
made of 317 stainless steel and the filter media is made of polypropylene.
Soluble sodium salts are washed from the cake by a cake wash assembly
consisting of two banks of drip wash nozzles and a drag net.
59
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4. Raw Materials Preparation
This section qf the system consists, basically, of three pieces of
equipment, the day-tank for lime slurry, the soda ash silo, and the
soda ash solution tank.
The lime slurry tank is a cylindrical vessel, 24.5 ft in diameter and
24.5 ft in height, made of carbon steel and equipped with a 20 HP agitator.
The lime slurry is pumped in a recirculation loop back to the top of the
lime slurry tank. (A back-up pump is provided.) The lime feed to the
primary reactors is taken from this recirculation loop. Ni-hard alloy
was used in the manufacture of these pumps.
The soda ash silo is a cylindrical tank, 12 ft in diameter and 34.5 ft
in height, with a conical bottom, 6 ft bottom diameter and 5.5 ft in
height, made of carbon steel. It is equipped with a cone vibrator, a
baghouse at the top, as well as a pneumatic system to top-feed the
silo. A weigh feeder is used to transfer the soda ash from the silo
to the solution tank. A fan has also been installed to blow back the
warm, humid vapors from the solution tank. Otherwise these vapors
could cause the accumulation of soda ash crystals in the feed chute and
weigh feeder thus interfering with the normal operation of the soda ash
make-up solution.
The soda ash solution tank is a small cylindrical vessel (6 ft diameter,
8 ft height) made of carbon steel and lined with glass reinforced poly-
ester. It is equipped with a 1.5 HP agitator.
C. OFFSITES AND AUXILIARIES
The offsites required for the dual alkali system at Cane Run Unit No. 6
include: services for electrical supply, water supply and instrument air;
oil for reheating the wet flue gas, raw materials receiving and storage
facilities; a wet chemical analytical laboratory; and shop facilities
for repair and maintenance of machinery and instruments. Except for
electrical service, all of these offsites existed and are available at
Cane Run Station. An electrical substation including appropriate step-
down transformers has been installed for the dual alkali system at Unit
No. 6.
1. Electrical Power
Electrical power available at Cane Run Station for operation of the system
include the following:
4,160 V ac, three-phase, 60 hertz
480 V ac, three-phase, 60 hertz
120 V ac, single-phase, 60 hertz
60
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A feed line will be taken from the existing 14 KV substation and the
voltage will be reduced in a step-down transformer to 4,160 volts. Step-
down transformers for further voltage reduction to 480 volts and from 480
volts to 120 volts have been installed at LG&E.
The power requirement for the system is estimated at about 1% of the
total power generated by the boiler at peak load. However, since the
design gas flow rate for the dual alkali system at LG&E is higher than
the maximum flow rate, the estimated electrical energy requirement is
a conservative one. A summary of the ancillary requirements for the
dual alkali system is given in Table V-l.
2. Water Supply
The maximum water requirement for the system is estimated at 450 gpm,
not including the water associated with the slurried lime feed. Of the
450 gpm, approximately 230 gpm are required for process streams and about
220 gpm for non-contact cooling.
River water is used for all water requirements. The river water is
available at the following conditions;
Water Supply Pressure ——~ 50-100 psig
Water Temperature 35-90°F
Total Dissolved Solids — 300-500 ppm
Suspended Solids • 50-500 ppm
pH —
Na2S04 ~ ~ 20-200 ppm
Hardness ——— 80-250 ppm
CaC03 ~~ 50-250 ppm
Fe . —— 0.1-30 ppm
Mn 0.15-2.5 ppm
NaC1 10-100 ppm
An in-line filter is used to filter the water supply to the system to
prevent solids from entering the pump seals and filter spray nozzles.
61
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TABLE V-l
ANCILLARY REQUIREMENT FOR THE DUAL ALKALI SYSTEM
LOUISVILLE GAS AND ELECTRIC
CANE RUN UNIT NO. 6
Design Capacity (300 Mw, 5% S)
Electrical Power 3.1 Mw
River Water 450 gpm
No. 2 Fuel Oil 343 gal/hr
Typical Operation (180 Mw, 3.8% S)
Electrical Power 1.7 Mw
River Water 370 gpm
No. 2 Fuel Oil 206 gal/hr
62
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3. Instrument Air
Air is available at Cane Run Station at 60-125 psig. Air is used only
for instruments and air-operated controls. The total amount of air used
for the process is small and existing compressor capacity at the station
is adequate to supply the air.
4. Oil
No. 2 fuel oil is used to reheat the wet exhaust gases from the absorbers.
The oil requirement for the dual alkali system to provide 50F° of reheat
at design load is estimated to be 343 gallons/hour.
5. Carbide Lime Facility
Carbide lime slurry will be used to regenerate the spent sodium solution.
Since receiving, handling, and storage facilities for the carbide lime
slurry already exist at the plant, only a day tank to store lime slurry
for the process has been installed as part of the dual alkali system.
Carbide lime is available as a slurry containing 30% dry solids. The
slurry is shipped in LG&E barges to the Cane Run Station. The slurry
is then pumped from the barge to an agitated storage tank from which it
is pumped to the dual alkali day tank as required.
In general, calcined lime, hydrated lime, or carbide lime may be used
to regenerate the spent sodium solution. While carbide lime is cheaper
than commercial lime, it is not available at most locations. Normally,
calcined lime would be used. It would be slaked and fed to the system
as a slurry, and therefore would not be considered an offsite. It is
included as an offsite here because the carbide lime for facility already
exists.
6. Laboratory and Shop Capabilities
The Cane Run Station has the necessary laboratory and shop capabilities
for the maintenance and operation of the dual alkali system. No additional
facilities are required. The equipment needed for wet chemical analyses
is small and has been incorporated in the existing plant control labora-
tory.
a. Laboratory Capability
The following laboratory equipment and materials are needed for the chem-
ical and physical testing required during the operation and testing period
of the dual alkali system:
63
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- Analytical balances.
- Atomic absorption spectrophotometer.
- pH meter with electrodes for standard pH measurements and lead
electrodes for sulfate titration.
Forced draft-type oven with temperature control (i 0.5°C).
- Automatic burets and magnetic stirrers.
- Distilled water and various reagents for wet analyses.
- Assorted glassware for sample preparations.
Much of this equipment may already be part of an existing control labora-
tory at a power plant for use in monitoring and analysis of coal, cooling
water, boiler feed water, and waste streams; or can be easily included as
a part of the control laboratory equipment. In some cases, special analyses
for metal ions (calcium, sodium, and magnesium) requiring the use of an
atomic absorption spectrophotometer can be performed by outside testing
laboratories.
b. Shop Capability
LG&E carries out their own plant construction. The Cane Run Station
has adequate shop facilities to operate and maintain the boilers and the
existing direct lime scrubbing systems. The shops are equipped with tools
and equipment worth over $3.0 million, including 157-ton capacity crane.
In general, the required shop capacity for dual alkali systems includes
the following:
- Crane capacity to lift motor, pump, valves, etc., which need
occasional maintenance.
- Machine shop to machine relatively simple surfaces, thread
pipes, etc.
- Welding equipment, both in shop and in field.
- Instrument shop to check out instruments.
- Electrical shop.
D. MECHANICAL TESTING OF EQUIPMENT
Mechanical testing of the dual alkali system began in December, 1978 and
concluded in March, 1979. Start-up operations were initiated in early
March, 1979. The results of the mechanical testing are presented in
64
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sections according to the major functions of the system: S07 absorption;
absorbent regeneration; solids dewatering; preparation of raw materials;
and auxiliary services. In general, all the tanks were checked for leaks
and their internal linings were inspected; the pumps and agitators were
checked and operated; all the lines were flushed; and all instruments
were zeroed and checked for proper operation. Specific tests for each
section as well as relevant results are discussed below.
1. Absorber Section
a. Liquid Related
In addition to the general tests, the flow distribution in the absorber
trays and the operation of the sprays (tray underside and emergency sprays)
was checked. The following corrective actions were required: vibration
of the recycle pump motors, initially 4-20 mills, was reduced to below
5 mills by the manufacturer; two butterfly valves in the absorber recir-
culation loops failed and were replaced by heavy duty butterfly valves;
and uneven liquid distribution in the absorber trays was corrected by
leveling the trays. Testing of the other items in this section was satis-
factory.
b. Gas Related
For this section, mechanical testing consisted of checking the ductwork,
the operation of the dampers, checking and balancing the booster fans,
checking and operating the gas reheater and checking the instrumentation.
Corrective action was required for the booster fans and the dampers.
The fluid drives for the booster fans required a correction in the shaft
gap after which the fluid drives were aligned. The control of the gas
flow to the absorbers was also modified. A single pressure controller is
now used to control the speed of the booster fans. The controller signal
is sent to each booster fan through a precalibrated bias. Previously, an
independent pressure controller was used for each fan. This change has
been incorporated in the control philosophy section (Chapter IV).
The gear boxes for the outlet dampers were replaced and the motors for
the damper drives were balanced by the manufacturer. The blades in the
inlet dampers had a tendency to drift apart. This problem was caused
by defective motor brakes. The possibility of providing additional
seals for the dampers to further reduce gas leakage is currently being
considered.
2. Reactors
In the reactor section, corrective action was required for the agitators
and transfer pumps. An excessive amount of current was being drawn by
the agitator motors. The current drawn by the agitators was reduced by
trimming the edges off the impellers thereby reducing the impeller size.
At the same time, the impeller arms were reinforced to minimize flexing.
65
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Operation of the agitators will be closely checked during start-up opera-
tion and any further modifications, if needed, will be included in the
Phase III, start-up report.
The large capacity of the transfer pumps caused excessive chatter in the
discharge control valves whenever attempting to control low flow rates.
To minimize this problem, the pumps were slowed down by changing the pump
sheaves.
3. Dewatering Section
a. Thickener and Thickener Hold Tank
During mechanical testing, the thickener overflow weir was adjusted. The
thickener rake was checked for rotation and operation and it was leveled.
The lining on the rake required some patching. The rake lift mechanism
was checked and operated. Some of the rake lift instrumentation was wet
and certain parts had to be replaced.
While operating the thickener underflow pumps, an excessive water hammer
effect caused the breaking of the lines. The pumps were slowed down to
the required range by replacing the pump sheaves.
b. Filters
Mechanical testing of the filters consisted of checking and operating the
filter drum and tub agitator drives, the vacuum pumps, and the blow-back
fans. The mechanical check-out of the filters did not require any sig-
nificant corrective action.
4. Raw Materials
a. Lime Slurry Day Tank
The agitator in the lime slurry tank required a modification similar to
the one performed on the reactor agitators. The edges of the impeller
were trimmed off in order to reduce the current drawn by the agitator
motor.
The screens in the suction side of the transfer pump were being plugged
by oversized particles. As was previously indicated in Chapter IV, a
disintegrator has been installed temporarily until a ball mill is installed
in the lime supply system for the Cane Run Station.
b. Soda Ash Make-up
This section of the dual alkali system consists of two major pieces of
equipment: the soda ash silo and the solution tank.
For the soda ash silo, the vibrating bin, the dust collector, and the
weigh feeder were checked and operated. The weigh feeder was also
calibrated.
66
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A bent agitator arm in the solution tank had to be straightened. During
loading of the system with soda ash, warm vapor from the solution tank
caused crystallization of the soda ash on the feed chute to the solution
tank. A blow-back fan was installed to prevent the vapors from entering
and plugging the chute.
5. Auxiliary Equipment
In this section of the system, all the sump pumps were checked and operated
and all the water supply lines were flushed. The river water used in the
system was found to be slimy, coating the walls of rotameters and occa-
sionally hanging the floats. The rotameters are being cleaned frequently
while solutions to the problem are being considered.
In general, the individual pieces of equipment performed satisfactorily
during the testing period. Very few pieces of equipment presented sig-
nificant problems; namely, the booster fans, the dampers, the reactor
agitators, and pumps.
67
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VI. CAPITAL COSTS FOR THE DUAL ALKALI SYSTEM
AT THE CANE RUN STATION
The installation of the dual alkali system at Cane Run Station Unit No. 6
required capital investment in three different facilities: the flue gas
desulfurization (FGD), the lime slurry feed system, and a waste processing
and disposal system. Each of these facilities have involved independent
design and installation efforts, and their costs are reported separately.
While construction of the FGD system was essentially completed in February,
1979, a significant amount of work remained on the lime feed and waste
processing facilities. Therefore, the costs presented here represent the
actual expenditures incurred plus estimates for completion of the system.
Table VI-1 gives a summary of the capital investment for all three
facilities. The total projected cost of $20.6 million includes actual
expenditures reported through February 28, 1979 and the estimated capital
required for completion. Approximately 80% of this total projected capital
cost was expended through the end of February. Most of the remaining
20% is related to the waste processing plant.
A further breakdown of capital investment by subsystems is given in
Table VI-2. This table also provides information on the capital
expenditures incurred through February 28, 1979 as a percent of the
estimated total capital required for various cost elements of each
facility.
The capital costs in Tables VI-1 and VI-2 have been reported on an
"as-incurred plus estimate for completion" basis, and therefore do not
represent a constant dollar value of the capital investment. The cash
flow records kept by Louisville Gas and Electric have been used to
escalate the costs from the time of expenditure to June, 1979. The
total capital investment for the dual alkali system (including all three
systems) is $22.0 million in June, 1979 dollars.
A. FGD SYSTEM
The total cost of the FGD system is estimated to be $16.5 million. The
expenditures incurred as of February 28, 1979 were 92.7% of this value.
The remaining 7.3% were the estimated cost for completion. The installa-
tion of the FGD system has been completed and start-up operations are
in progress. It should be noted that the capital expenditure of $16.5
million includes the cost of the start-up operations. The material costs
for the FGD system include all the process equipment, instrumentation,
piping and other process related materials supplied by Combustion Equip-
ment Associates and presented in Table VI-3. The material costs also
include electrical utilities, service piping, and their associated
instrumentation as well as other materials such as foundations, buildings,
etc. The breakdown of these additional materials costs is given in Table
VI-4.
68
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TABLE VI-1
CAPITAL COSTS FOR THE DUAL ALKALI SYSTEM
AT CANE RUN UNIT NO. 6, LG&E
"AS-INCURRED PLUS ESTIMATE FOR COMPLETION BASIS"
MATERIAL COSTS:
• FGD System2
Process Materials
Additional Materials
• Utility and Service Piping and Instrumentation
• Electrical
• Other
7,392,300
228,900
731,700
1.740.300
10,093,200
• Lime Slurry Feed System
- Process Equipment 617,200
- Electrical, Piping, and Instrumentation 170,800
788,000
• Solid Waste Disposal Systemb
- Fly Ash Supply 309,600
- Waste Processing 1,060,900
- Landfill Area Materials0 559.000
1.929.500
TOTAL MATERIAL COSTS 12,810,700
ERECTION COSTS:
• Direct Labor 3,058,500
• Field Supervision*1 337,200
• Construction Overhead 2,038,900
TOTAL ERECTION COSTS 5,434,600
ENGINEERING COSTS:d
• System Supplier's Engineering 1,162,700
• Owner's Consultant Engineering 985.000
TOTAL ENGINEERING COSTS 2,147,700
SPARE PARTS: 203,900
TOTAL CAPITAL INVESTMENT 20,596,900
*See Tables VI-3 and VI-4 for breakdown of costs.
bBattery lind^: cake discharge from filters.
cincludes earth moving equipment, dikes, culverts, and bridges.
downer's engineering is included in field supervision.
69
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TABLE VI-2
CAPITAL COST BREAKDOWN BY SUB-SYSTEM3
LOUISVILLE GAS AND ELECTRIC
CANE RUN UNIT NO. 6
Sub-System
FGD
Lime Slurry
Waste Disposald
TOTAL
Material Costsb
10,256,200
(91%)
800,000
(69%)
1,958,400
( 0%)
Direct
Labor
2,400,900
(92%)
205,500
(72%)
452,100
( 0%)
Erection Costs
Field Superv.
& Engineering
281,800
(98%)
16,400
(70%)
39,000
( 0%)
Construction
Overhead
1,376,400
(92%)
194,300
(71%)
468,200
( 0%)
Engineering Costs
LG&E
Suppl. Consult.
1,162,700 985,000
(100%) (100%)
c
c
Total
16,463,000
(93%)
1,216,200
(70%)
2,917,700
( 0%)
13,014,600
3,058,500
337,200
2,038,900 1,162,700 985,000 20,596,000
Numbers in parentheses represent expenditures incurred as of February 28, 1979 as percent of the estimated total costs.
Includes spare parts at 1% of total costs.
cIncluded in Field Supervision and Engineering.
dThe estimates for waste disposal system are based on a contract awarded to IUCS to provide LG&E with the waste disposal
facilities and estimated costs for the erection of the system.
-------
TABLE VI-3
MATERIAL COSTS FOR THE FGD SYSTEM21
- PROCESS MATERIALS -
Process Equipment
- Absorbers 901,510
- Tanks 609,605
- Thickener Shell and Mechanism 340,191
- Vacuum Filters 971,298
- Reheaters 167,681
- Fans and Fluid Drives 570,249
- Pumps and Motors 835,316
- Agitators 95,905
- Weigh Feeder 49,911
- Lining 424.739
4,966,405
Process Instrumentation 439,100
Process Piping, Insulation, and Heat Tracing 634,568
Other Process Materials
- Ductwork and Dampers 1,028,702
- Structural Steel 323,543
1.352,245
7,392,318
aAs-incurred plus estimate for completion basis.
71
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TABLE VI-4
MATERIAL COSTS FOR THE FGD SYSTEM3
- ADDITIONAL MATERIALS -
Utility and Service Piping and Instrumentation
- Instrumentation 73,300
- Piping, Insulation, and Heat Tracing 86,200
- Miscellaneous 69.400
228,900
Electrical
- Electrical Auxiliaries (4160, 460, 220/110 volt) 487,900
- Station Grounding and Ducts 38,100
- Station Control (wiring to instruments) 205.700
731,700
Other
- Foundations15 964,700
- Buildings 220,200
- Land Improvements, Roads, and Storm Runoff Containment 555.400
1,740,300
aAs-incurred plus estimate for completion basis.
"Includes lagging and insulation for fans.
72
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B. LIME SLURfrY FEED
The lime slurry system encompasses all the facilities required to unload,
store, and process the carbide lime slurry being barged from a nearby
acetylene plant. Part of these facilities existed prior to the installa-
tion of the dual alkali system, but had to be expanded and modified—in
particular, the piping from the dock, the pumping, and the storage facil-
ities. This portion of the system has been completed. However, since
the carbide lime contains some oversized material, a grinding mill con-
sisting of a hydroclone and wet ball mill are being installed. It is
estimated that this system will be completed in June, 1979.
The lime slurry facilities are used by all three FGD systems on Unit
Nos. 4, 5, and 6 at the Cane Run Station. The capital costs have been
apportioned to the dual alkali plant according to the relative operating
capacity of the units. (Unit No. 6 capacity represents roughly 3/7 of
the total capacity of all three boilers.)
The total cost of the lime slurry system attributed to the dual alkali
system is estimated to be $1.2 million. The expenditures as of February 28,
1979 amounted to 70% of this value. The remaining 30% is the estimated
cost of the grinding mill.
C. WASTE DISPOSAL
The cost of the waste processing and disposal system is estimated at
$2.9 million. As of February 28, 1979, no expenditures were incurred
for this system. The estimated cost, therefore, is based on the contract
awarded to I.U. Conversions Systems (IUCS) for providing LG&E with the
equipment needed for this system, and on estimated costs for the erection
of the system. The waste disposal system involves stabilization of the
FGD waste with fly ash and lime and dry landfill of the stabilized
material in a location adjacent to the plant. The material costs include:
the discharge conveyors to transport the FGD waste from the filter to the
pug mill; the fly ash and lime supply; and pug mill for mixing the filter
cake, fly ash and lime; the stacker conveyors; and disposal equipment.
73
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VII. GLOSSARY
Active Sodium - Sodium associated with anions involved in SC>2 absorption
reactions and includes sulfite, bisulfite, hydroxide and carbonate/
bicarbonate. Total active sodium concentration is calculated as
follows :
[Na+] „, = 2 x ([Na-SO,] + [Na,CO,]) + [NaHSOo] + [NaOH] + [NaHCO-]
active z J ^ -> J ~>
Available Alkali - The percentage of the calcium hydroxide in the raw hy-
drated lime, or in the insoluble solids in the carbide lime slurry.
Calcium Utilization - The percentage of the calcium in the lime or limestone
which is present in the solid product as a calcium- sulfur salt.
Calcium utilization is defined as:
mols (CaSO- + CaSO,) generated
Calcium Utilization = - . „ — ;=— ; - x 100%
mol Ca fed
Concentrated Dual Alkali Modes - Moles of operation of the dual alkali
process in which regeneration reactions produce solids containing
CaSO_ • 1/2 H20 or a mixed crystal containing calcium sulfite and
calcium sulfate hemihydrates , but not containing gypsum. Active
sodium concentrations are usually higher than 0.15M Na in con-
centrated mode solutions.
Dilute Dual Alkali Modes - Modes of operation of the dual alkali process
in which regeneration reactions produce solids containing gypsum
• 2 HoO) . Active sodium concentrations are usually lower
than 0.15M Na in dilute mode solutions.
Sulfate Formation - The oxidation of sulfur (IV)-sulfite and bisulfate.
The level of sulfate formation relative to S02 absorption is given
by:
01* u j mols S (IV) oxidized -.__,
Sulfate Formation = - r~ZZ — - j - x 10°^
mol SO- removed
Sulfate Precipitation - The formation of CaSO^ • XH20 insoluble solids.
The level of sulfate precipitation in the overall scheme is given
by the ratio of calcium sulfate to the total calcium-sulfur salts
produced:
mols CaSO, produced
Sulfate Precipitation
mols (CaSO- + CaSO,) produced
74
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APPENDIX
EQUIPMENT DETAILS
-------
TABLE A-l
EQUIPMENT LIST
Equipment
1. Agitators
(w/motors)
Description
Reactant Feed Tank
Primary Reactor Tanks
Secondary Reactor Tanks
Soda Ash Solution Tank
Vacuum Filters
No.
Required
1
2
2
1
3
2. Dampers
Booster Fan Inlets
By-Pass
Absorber Outlets
Reheater Fans
2
1
2
2
3. Ductwork
Take-Off Connecting Ducts
Booster Fan Inlet Ducts
Booster Fan Outlet Ducts
Absorber Outlet Ducts
Duct/By-Pass Transition
2
2
2
2
1
4. Expansion Joints
Tie-ins
Booster Fan Inlets
Booster Fan Pant Legs
Booster Fan Outlets
Booster Fan Outlet Ducts
Absorber Outlet PC#1
Absorber Outlet PC#2
Breeching
By-Pass
2
2
4
2
2
2
2
1
2
A-l
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Equipment
5. Fans
TABLE A-l
(Continued)
Description
Booster Fans, Drives, & Motor
Reheater Fans & Motors
Filter Blow Back Fans & Motors
Soda Ash Chute Fan & Motor
No.
Required
2
2
3
1
6. Heaters
Reheater
7. Pumps & Feeders
Lime Reactant Feed Pump & Motor 2
Reactor Transfer Pump & Motor 2
Thickener Underflow Pump & Motor 2
Soda Ash Solution Pump & Motor 2
Thickener Hold Tank Transfer Pump & Motor 2
Absorber Recycle Pump & Motor 4
Vacuum Pumps & Motor 3
Filtrate Sump Pumps & Motor 2
Soda Ash Sump Pumps 2
Silencer Overflow Sump Pumps & Motors 2
Soda Ash Weigh Feeder & Motor 1
8. Tanks
Reactant Feed Tank
Primary Reactor Tank
Secondary Reactor Tank
Soda Ash Silo
Thickener Hold Tank
Soda Ash Solution Tank
Filtrate Receivers
Thickener
1
2
2
1
1
1
3
1
A-2
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TABLE A-l
(Continued)
Equipment
10. Thickener
Mechanism
Description
Thickener Mechanism & Motor
Thickener Lift Rake Motor
No.
Required
1
1
11. Vacuum Filter
Vacuum Filters & Drives
12. Vessels
Absorbers
A-3
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TABLE A-2
MATERIALS OF CONSTRUCTION
1. Agitators
(a) Reactant feed tank—carbon steel.
(b) Primary reactors—shaft: carbon steel, rubber lined;
hub and blades: 317L s.s.
(c) Secondary reactors—shaft: carbon steel, rubber lined;
hub and blades: 317L s.s.
(d) Soda ash solution tank—carbon steel, rubber lined.
2. Dampers
(a) Booster fan inlet—A-283 carbon steel.
(b) Bypass and absorber outlet—317L s.s.
3. Ductwork
(a) Ductwork carrying hot flue gas to the scrubber inlet—carbon
steel.
(b) Ductwork carrying saturated flue gas from the scrubber to
reheater—carbon steel, coated internally with a flake
reinforced polyester lining.
(c) Ductwork carrying reheated flue gas from the reheater to
stack—317L s.s.
(d) Bypass/transition duct—carbon steel.
4. Expansion Joints
(a) Expansion joints on inlet side of absorbers—viton.
(b) Expansion joints on outlet side of absorbers—chlorobutyl
for wet gas and viton for dry gas (after reheat).
5. Fans
(a) Housing—A441.
(b) Blades—A441, with ware plates constructed from A441 material.
A-4
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TABLE A-2
(Continued)
6. Pumps
(a) Housing—rubber lined.
(b) Impeller—rubber lined.
7. Tanks
(a) Thickener hold tank—carbon steel, flake reinforced
polyester lining.
(b) Primary reactors—316L s.s.
(c) Secondary reactors—carbon steel, flake reinforced polyester
lining, rubber pad on bottom.
(d) Reactant feed tank—carbon steel.
(e) Soda ash solution tank—carbon steel.
8. Soda Ash Silo
(a) Carbon steel.
9. Weigh Feeders
(a) Frame—mild steel.
(b) Internals—304 s.s.
10. Thickener
(a) Thickener shell—carbon steel, bottom concrete with interior,
flake reinforced lining.
(b) Rake, shaft, and centerwell—carbon steel, rubber lined.
11. Vacuum Filter
(a) Filter drum--317 ELC s.s.
(b) Agitator—317 ELC s.s.
(c) Filtrate receiver—FRP.
A-5
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TABLE A-2
(Continued)
12. Absorber
(a) Absorber shell—carbon steel, coated internally with flake
reinforced polyester lining.
(b) Absorber trays—317 s.s.
(c) Demister—noryl.
13. Piping
(a) All process piping—FRP.
(b) Piping for make-up water and service water and all other
piping not subject to corrosion—carbon steel.
-------
Number Required:
Impeller Type
Impeller dia.
RPM
Shaft dia.
H.P.
Reactant Feed Tank
1
turbine
89"
30
4.5"
20
TABLE A-3
AGITATORS
Primary
Reactors
2
turbine
67"
37
3.5"
7.5
Secondary
Reactors
2
turbine
95"
30
5"
25
Soda Ash
Solution Tank
propeller
12"
350
1.5"
1.5
Material of
Construction:
Shaft
Blades
C.S.
C.S.
317L S.S.
R.C.G•5•
317L S.S.
R. C. C. S.
R.C.C.S.
Data are given per agitator
C.S. - Carbon Steel
R.C.C.S. - Rubber Covered Carbon Steel
S.S. - Stainless Steel
-------
TABLE A-4
DAMPERS
oo
Ntimber Required:
Design flow rate
- ACFM
- °F
Size
Position of duct
Type
Entry
Normal position
Material of construction
Max. gas leakage, % of
design flow rate
Booster Fan Inlet
2
533,000
350
135-1/4" x 138-1/2"
Horizontal
Guillotine
Bottom
Open
A-36 steel
Bypass
1
1,065,000
350
162" x 240"
Horizontal
Multi-louver
—
Closed
316L S.S.
Absorber Outlet
2
487,000
200
156" dia.
Horizontal
Guillotine
Top
Open
316L S.S.
Paint external members
Zinc chromate
Zinc chromate
Zinc chromate
-------
TABLE A-5
DUCTWORK
VO
Equipment
Take off connecting duct
Booster fan inlet duct
Booster fan outlet duct
Absorber outlet duct
Duct bypass/transition
Number Required
2
Dimensions
Inlet 11'8" x 11'6"
Outlet to booster fan inlet duct 11'3" x 11'6"
Outlet to bypass transition 11fl" x 12'1"
Overall dimensions 11'8" x 11'6" x 16'10"
Inlet 11'3" x 11'6"
Outlets 16'8" x 3'2" (two)
Overall dimensions 11'6" x 28' x 16'6"
Inlet duct 10'7" d
Outlet duct 13'9" d
Overall length 12'
Inlet 13' d
Outlet 13' d
Overall length 80'
Inlets from take off connecting duct ll'l" x 12'1" (two)
Inlets from absorber outlet duct 13' d (two)
Outlet 28' x 13'6"
Overall dimensions 30'3" x 24'6" x 19'10"
Note: See Table A-2 for materials of construction
-------
TABLE A-6
Service
Tie-in (DJ 101/201)
Booster Fan Inlet (DJ 102/202)
Booster Fan Pant Leg (DJ 103A/203A)
(DJ 103B/203B)
Booster fan outlet (DJ 104/204)
Absorber inlet (DJ 105/205)
Absorber outlet 1 (DJ 106/206)
Absorber Outlet 2 (DJ 107/207)
Breeching (DJ 108)
Bypass (DJ 109)
Reheater duct (DJ 110/210)
(DJ 111/211)
EXPANSION JOINTS
Number Required
2
4
2
2
2
2
2
1
2
4
Size
11'10" x H'8-12"
11'5-1/4" x 11'8-1/2"
3'3-7/8" x 16'10-1/4"
10*9-1/4" x 8'9-l/2"
13'11-5/8" dia.
13'2" dia.
13'2" dia.
13'7-7/8" x 28'l-7/8"
11'10" x 11'8-1/2"
6'9-l/4"
Material
Viton
Viton
Vitron
Viton
Viton
Chlorobutyl
Viton
Viton
Viton
Special Hi-
Temp. Material
All the expansion joints except absorber outlet 1 and reheater duct expansion joints are designed for
400°F with excursions to 600°F for 5 minutes, 4 times a year. All the expansion joints are 9" wide,
except DJ 107/207 - 16" wide and DJ 110/210, 111/211 - 11-1/4" wide.
-------
TABLE A-7
BOOSTER FANS
Number required
Flue gas volume
Flue gas temperature
Inlet static pressure
Outlet pressure at design
flow rate
Gas density
Inlet dust loading
Maximum vibration
amplitude
Type
Fan blade design
Materials of construction
Drive
Motor HP
Volts
Motor rpm
533,000 acfm
300 °F
+2 inch WG
10.5 inch WG
0.0526 Ib/cu ft
0.0537 gr/cu ft
2.2 mils at 720 rpm
Centrifugal forced draft
Backward inclined airfoil
with wear plates
Carbon steel
Fluid drive
1,300
4,000
720
A-ll
-------
TABLE A-8
REHEATERS
Operating Conditions
Wet flue gas flow rate
Temperature
Pressure
H20 Vapor
S02
Particulates
Temperature after reheat
Heater Requirements
For flue gas
Radiation loss
Heater outlet temperature
Turndown
Heater outlet pressure
Fuel Data
Fuel type
Oil flow rate
Air Inlet Temperature
Winter
Summer
436,500 acfm
126°F
+2 inch WG
2,475 Ibs/min
11.25 Ibs/min
200 ppm dry basis
2.48 Ibs/min
176°F
25,632,000 Btu/hr
1,282,000 Btu/hr
800°F max.
To 20% of the capacity
+7 inch WG
Number 2 fuel oil
171 gal/hr
0°F
100 °F
No. of Reheaters Required
A-12
-------
OJ
Number Required
Operating
Spare
Capacity
gpm
head, ft
Speed
Material of
Construction
Packing
Drive
Motor Mounting
Voltage, volts
Drip proof
BHP/IHP
Service Factor
Overall Size3
Absorber
Recycle
Pump
2
2
4,600
130
Variable
RLCI
Yes
V belt
Overhead
4,000
Yes
215/250
1.15
12 x 10 x 25
Reactor
Pump
2
1,965
85
Variable
RLCI
Yes
V belt
Overhead
460
Yes
62/75
1.15
10 x 8 x 21
TABLE A-9
PUMPS
Thickener
Hold Tank
Pump
1
1
4,185
105
Variable
RLCI
Yes
V belt
Overhead
4,000
Yes
157/200
1.15
12 x 10 x 25
Thickener
Underflow
. Pump
1
1
665
115
Variable
RLCI
Yes
V belt
Overhead
460
Yes
33/40
1.15
5 x 5 x 14
Reactant
Feed Pump
1
1
340
115
Variable
NI-Hard
Yes
V belt
Overhead
460
Yes
25/25
1.15
3 x 1.5 x 16
Soda Ash
Solution
Pump
1
1
140
80
Variable
RLCI
Yes
V belt
Overhead
460
Yes
6/10
1.15
1 x 1.5 x 6
RLCI - Rubber lined cast iron
All pumps are centrifugal pumps
aAll dimensions are in feet
-------
>
!-•
•e-
Process Data
Liquor specific gravity
pH range
Chlorides, ppm
Operating pressure, in wg
Design pressure, in wg
Operating temperature, °F
Design temperature, °F
Specified data
Minimum thickness, inches
Seismic zone
Code
Tank shape
Dimensions, dia. x height
Baffles
Agitator
Materials
Shell and head
Internal structure
Nozzles necks/flanges
Lining
Paint
Gaskets
Erection weight, Ibs
Operating weight, Ibs
TABLE A- 10
Primary Reaction
Tank
1.1
5-11
12,000
Liquid head
Liquid head
126
3/16
1
API650
Cylindrical
11' x 14'
4
Yes
316L S.S.
316L S.S.
316L S.S.
None
Zinc chromate primer
Neoprene
7,500
97,500
TANKS
Secondary Reaction
Tank
1.1
11-12.5
12,000
Liquid head
Liquid head
126
1/4
1
API650
Cylindrical
20' x 33'
4
Yes
A283 (C.S.)
C.S.
C.S. & 316L S.S.
Glass reinforced
polyester + 3/8"
thick rubber pad
on bottom
Zinc chromate primer
Neoprene
36,000
715,000
Thickener
Hold Tank
1.1
12
12,000
Liquid head
Liquid head
110
1/4
1
API650
Cylindrical
36' x 23'
None
No
A283 (C.S.)
C.S.
C.S. & 316L S.S.
Glass reinforced
polyester
Zinc chromate primer
Neoprene
39,000
1,183,000
Reactant
Feed Tank
1.2
12
Liquid head
Liquid head
70
100
1/4
1
API650
Cylindrical
24'6" x 24'6"
4
Yes
A283 (C.S.)
C.S.
C.S.
Zinc chromate primer
Neoprene
39,000
785,000
Soda Ash
Solution Tank
1.1
12
12,000
Liquid head
Liquid head
110
1/4
1
API650
Cylindrical
6' x 8'
4
Yes
A283 (C.S.)
C.S.
C.S. & 316L S.S.
Glass reinforced
polyester
Zinc chromate primer
Neoprene
2,500
17,500
-------
TABLE A-11
SODA ASH SILO
Process Data
Specific gravity
Soda ash type
Specified Data
Minimum thickness
Wind load at 30'
Seismic zone
Code
Tank shape
Size
Thickness
Attachments
Materials
Shell and head
Internals
Nozzles necks/flanges
Paint
Gaskets
Erection weight
Operating weight
65 lbs/ft:
dense
1/4"
30 PSF
1
API650
Cylindrical plus conical bottom
12' diameter x 34'6" height-cylinder
6* bottom diameter x 5*6" height-cone
3/8" thick bottom of cylinder
5/16" thick middle of cylinder
1/4" thick top of cylinder
1/4" thick cone
Cone vibrator, baghouse at top, and
piping at top for pneumatic feed system
A283 (C.S.)
C.S.
C.S.
Zinc chromate primer
Neoprene
22,000 Ibs
300,000 Ibs
A-15
-------
TABLE A-12
THICKENER
Design stream conditions
Reactor bleed
Filter overflow
Filtrate
Soda ash solution
Thickener recycle
Thickener underflow
Operating temperature
Seismic zone
Thickener type
Diameter
Height
Feed well
Diameter
Height
Number of arms on rake
Cone scraper
Overflow weir plate
Access walk way
Rake drive motor
Rake lifting device motor
Materials
Rake
Feed well
Shell
Bottom
Weir plate
Shell and bottom
Paint
3,570 gpm
148 gpm
500 gpm
50 gpm
155 gpm
605 gpm
110 °F
Flat bottom
125'
23'
12'
11'
2
Yes
Notched
On one side of the superstructure
5 HP
3 HP
Rubber covered carbon steel
Rubber covered carbon steel
Carbon steel
Concrete
Polypropylene
Lined with glass reinforced polyester
Zinc chromate primer
A-16
-------
TABLE A-13
VACUUM FILTER
Process data
Net slurry feed
Specific gravity
Temperature
PH
Wash water
Filter requirements
% Solids in cake
Total flow
Filtrate
Flow rate
PH
Specific gravity
Cake wash rate
Number of filters required
Size
Cake discharge mechanism
Liquid level control in
filter tub
Cake wash assembly
Filter drum speed
Agitator type
Filtrate receiver
Motor
Vacuum pump
Drum drive
Filter blow back pump
Agitator drive
Materials
Filter drum
Filter agitator
Filter scraper
Filtrate receiver
Drainage grid
Filter media
Design 3,147 Ibs/min - 302 gpm
Maximum 4,533 Ibs/min - 448 gpm
1.25
140°F maximum
11-12.5
2,108 Ibs/min design
55% minimum
63% average
1,246 Ibs/min design
1,584 Ibs/min maximum
299-750 gpm
10.5-12.3
1.064
91 gpm normal
300 gpm maximum
3 including spare
8' diameter 16' face
Blower assisted scraper blade
Adjustable overflow weir
Drip wash nozzles with drag net
0.3-3.0 rpm
Counter weighted rocker arm
54" diameter x 54" height
100 HP
5 HP
2 HP
1.5 HP
317 ELC stainless steel
317 ELC stainless steel
317 stainless steel with rubber tip
FRP
Polypropylene
Polypropylene
A-17
-------
TABLE A-14
ABSORBER
Process data
Specific gravity
pH range
Chlorides, ppm
Operating pressure, inch WG
Design pressure, inch WG
Operating temperature, °F
Design temperature, °F
Upset conditions
Temperature, °F
Time, minutes
Specified data
Corrosion allowance
Wind load at 30', PSF
Seismic zone
Code
Tank shape
Size
Thickness, inch
Internals
Materials
Shell and head
Trays/supports
Spray nozzles
Internal piping/supports
Mist eliminator/supports
Nozzle necks/flanges
Internal fasteners
Gaskets
External paint
Lining
Erection
Erection weight, Ibs
Operating weight, Ibs
1.2
5-12
12,000
+11.5
+12.5
125
350
600
5
none
30
1
API650
Cylindrical shell with conical head
32' diameter x 45' height shell
10'6" height x 13' top diameter cone
3/8
Sprays + 2 trays + chevron demister
A283 (carbon steel)
317L S.S.
316 S.S. & 317 S.S.
FRP
Noryl
C.S. and S.S.
C.S.
Neoprene
Zinc chromate
Glass reinforced polyester
108,000
475,000
A-18
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
IEPORT NO.
EPA-600/7-79-221b
2.
3. RECIPIENT'S ACCESSION-NO.
TITLE AND SUBT.TLE Fuii_Scale Dual Alkali Demonstration
System at Louisville Gas and Electric Co. — Final
5. REPORT DATE
September 1979
Design and System Cost
B. PERFORMING ORGANIZATION CODE
.AUTHORIS)
Frank, *G.J. Ramans, **C.R. La Mantia, **R.R. Lunt,
and **.T.A.
B. PERFORMING ORGANIZATION REPORT NO.
. PERFORMING ORGANIZATION NAME AND ADDRESS
Louisville Gas and Electric Company
311 W. Chestnut St.
Louisville, KY 40201
10. PROGRAM ELEMENT NO.
EHE 624 A
11. CONTRACT/GRANT NO.
68-02-2189
2. 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
Final: Q/76 - 3/7Q
14. SPONSORING AGENCY CODE
EPA/600/13
is.SUPPLEMENTARY NOTES IERL-RTP project officer is Norman Kaplan, MD-61, 919/541-2556.
(*) CEA. (**) A.D. Little, Inc. EPA-600/7-78-010 and -OlOa are related reports.
16. ABSTRACT
The report describes phase 2 of a 4-phase demonstration program involving
the dual alkali process for controlling S02 emmissions from Unit 6, a coal-fired
boiler at Louisville Gas and Electric Co.'s Cane Run Station. The process was
developed by Combustion Equipment Associates, Inc., and Arthur D. Little, Inc. The
program consists of four phases: (1) preliminary design and cost estimation; (2)
engineering design, construction, and mechanical testing; (3) startup and performance
testing; and (4) 1-year operation and test programs. The. report describes final
engineering design, construction and mechanical testing, and installed system capital
cost. Construction of the system was completed in February 1979 and system startup
was initiated in March 1979. Total capital investment for the entire plant,
including waste disposal, is estimated to be $20.4 million (construction of the
waste disposal facilities is not complete).
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution
Scrubbers
Alkalies
Sulfur Dioxide
Coal
Combustion
Desulfurization
Design
Construction
Testing
Capitalized Costs
Pollution Control
Stationary Sources
Dual Alkali Process
13B
07A
07D
07B
21D
21B
I3A_
13M
14A
•*•->"• .
21. NO. OF PAGES I
H7
22. PRICE I
18. DISTRIBUTION S1ATEMEN1
Release to Public
Form 2220-1 (1-73)
Unclassified
eport)
20. SECURITY CLASS (Thispage)
Unclassified
------- |