PQ87166609 

11111111111111111111 m1 Jill Ill 

EPA/600/ 9-87/004a 

February 1987 

PROCEEDINGS: TENTH SYMPOSIUM ON FLUE GAS DESULFURIZATION 

Atlanta, Georgia, November 1986 

Volume 1 

Compiled by 

Barbara Emmel 

Radian Corporation P. 0. Box 13000 

Research Triangle Park, North Carolina 27709 

EPA Contract 68-02-3994, Work Assignment 75 

EPRI Contract 982-40 

Project Officers: 

Julian W. Jones Robert E. Moser 

U. S. Environmental Protection Agency Air and Energy Engineering Research Laboratory Research Triangle Park, North Carolina 27711 Electric Power Research Institute 

3412 Hillview Avenue 

Palo Alto, California 93404 

AIR AND ENERGY ENGINEERING RESEARCH LABORATORY 

OFFICE OF RESEARCH AND DEVELOPMENT 

U.S. ENVIRONMENTAL PROTECTION AGENCY 

RESEARCH TRIANGLE PARK, NC 27711 

O s Department 

REPRODUCEof O 

Comm.

BY; a-rc;.e ~ , Nattot.ai i4d'ln1ca1 tnfol"'ffadon Serv,ce ::.,pringl'i•ld, vtrotniJt 22U1 

TECHNICAL REPORT DAtA (P/~Qit ttlld /IISlnJctions on tht ttvuu ~[ott compTttint} 

1. REPORT NO. ,2. 3. RECIPIENT'S ACCESSION NO, EPA/ 600/9-87 / 004a Nl7 166 6097B 4 . TITI.E ANO SUBTITLE I . IUP'OI'IT DATE 

Proceedings: Tenth Symposium on Flue Gas February 1987 

Desulfurization, Atlanta, Georgia, November 1986; •. P'EAFOAMING OI'IOANIZATION CODE 

Volume 1 

7. AUTMOPIIS) •. PERFORMING ORGANIZATION REPORT NO. 

Barbara B. Emmel, Compiler 

~· PEI'II"ORMING OFIOANIZATION NAME AND ADDI'IES$ 10. PROGRAM EI.EMENT NO. 

Radian Corporation 

P . 0. Box 13000 11. t;ONT .. A!;T/I;O .. ANT NO. 

Research Triangle Park, North Carolina 27709 68-02-3994, Task 75 

12. SPONSORING AGENCY NAME AND AOOAESS 13. TVI"E OF REPORT AND PERIOD COVERED 

EPA, Office of Research and pevelopm~nt* Proceedings; 11/17-21/ 86 

14. SPONSORING AGENCY CODE 

Air and Eneri.Y Erliineering Research Labora~ory 

Research Triangle Park, NC 277ll EPA/600/13 

15

· suPPLEMENTARY NOTEs AEERL project officer is Julian W. Jones, Mail Drop 62, 919 / 541· 

2489. {*)Cosponsored by EPRI, 3412 Hillview Ave., Palo Alto, CA 94304 under EPRI l~on ract 982..:40 EPRI nroiect nffi f'~r· Robert E. Moser. 

16· AasTRACTThe proceedings document the Tenth Symposium on Flue Gas Desulfurization {FGD), held in Atlanta, GA, November 17-21. 1986. The symposium. jointly 

sponsored by EPA and EPRI, had as its objective the exchange of technical inform ation on FGD systems and processes applicable to utility and industrial boilers. Topies covered included: federal and state clean coal programs, the commercial status 

of FGD, acid deposition issues, FGD economics, industrial applications of FGD, and 

wet FGD additives (Volume 1); and wet FGD operations and reliability, spray dryer 

FGD, dry FGD technologies, and FGD by-product disposal and utilization (Volume 2). 

The proceedings include 38 papers and summaries of 17 poster session presentations. 

~7 . ICEV WOAOS AND POCUMENT ANAL. VSIS 

ja. DESCAIPTOAS b.IPENTIFIEPIS/OP'EN ENDED TEAMS c. CDSATI Field/Group 

Pollution Additives ~ollution Control 13B llG 

Flue Gases Spray Drying ~tationary Sources 21B 13H 

Desul.furization Byproducts ~ cid Deposition 07A,07D 14G 

Coal Disposal 21D 

Acidification Utilization 07B, 07C 

Economics 

18. OISTAI8UTION STATEMENT 18. SECURITY CLASS (171U Repol'f} 21. NO. OF I'AGES 

Release to Public 

Unclassified lfl q 

20. SECURITY CI.ASS (Thbptllf} 22.1"RICE 

Unclassified 

EPA l"orm 1220·1 (l·?a) i 
\ 

\ 

NOTICE 

This document has been reviewed in accordance with 

U.S. Environmental Protection Agency policy and 

approved for publication. Mention of trade names 

or commercial products does not constitute endorsement or recommendation for use. 

ii 
ABSTRACT 

The Tenth Symposium on Flue Gas Desulfurization was held in Atlanta, 

Georgia, November 17 through 21, 1986. This Symposium, jointly sponsored by EPRI and EPA, had as its objective the exchange of technical information 

regarding FGD systems and processes applicable to utility and industrial 

boilers. Topics covered during the Symposium included: Federal and State 

clean coal programs, commercial status of FGD, acid deposition issues, FGD 

economics, industrial applications of FGD, wet FGD additives, wet FGD 

operations and reliability, spray dryer FGDt dry FGD technologies, and FGD 

by-product disposal and utilization. The Symposium Proceedings, published in 

two volumes, include 38 papers and summaries of 17 poster session 

presentations. 

iii 

CONTENTS 

VOLUME 1 

SESSION 1: CLEAN COAL PROGRAMS 

frank T. Princiotta, Chairman 

"The Federal Clean Coal Technology Demonstration Program," C. L. Miller . • . . . . . . . . . . . 1-1 

"Ohio's Clean Coal Technology," D. A. Berger . 1-15 

"Illinois Coal Development Program," J. Mead** 

SESSION 2: STATUS OF FGD 

Stuart M. Dalton, Chairman 

"Evolution of FGO Technology," A. Weir, Jr •••• 2-1 

"Trends in Commercial Applications of FGO," H. T. Melia*, 

R. s. McKibben, F. H. Jones, and J. L. Kelley • . • . . . 2-23 

"Status of Acid Rain and S02 and NOx Abatement Technology in 

Japan," J. Ando* and C. B. Sedman . • . . • . • • . • 2-44 

"Assessment of so2;Nox Emission Control Technology in Europe," W. Ellison* and C. B. Sedman . . • . • . . . . • . . . . . . . 2-66 

SESSION 3A: FGO ECONOMICS: GENERAL 

Robert E. Moser, Chairman 

"Increasing the Clarity of Pollution Abatement Cost Estimates," 

J. A. Leggett, E. S. Rubin* and I. H. Torrens . . . . . . . 3-1 

"Economic Evaluation of Twenty-Four FGO Systems," R. J. Keeth*, . P. A. Ireland, and R. E. Moser ... ·. . . • . . . . . . . . . 3-15 

SESSION 38: FGD ECONOMICS: ACID DEPOSITION RETROFIT APPLICATIONS 

Julian W. Jones, Chairman 

"Plant Specific Retrofit Factors for Lime/Limestone FGD and Lime 

Spray Drying FGD," T. E. Emmel* and J. W. Jones . . . . . . . . . 3-35 

"Evaluation of Flue Gas Desulfurization as an Acid Rain Control 

Strategy for Utility Coal-Fired Boilers in the State of Ohio," 

B. A. Laseke*, H. J. Johnson, and D. A. Berger . . . . . . 3-55 

"The Tennessee State Acid Rain (STAR) Project," W. S. Bain 3-76 

*Denotes Speaker **No written manuscript 

v Preceding page blank 
CONTENTS (Continued) 

SESS ION 4: ACID DEPOSITION ISSUES 

Michael A. Maxwell, Chairman 

"Status of the Acid Rain Debate," B. J. Mclean • . . . . . . . 4-1 

"Status of the National Acid Precipitation Assessment Program," P. M. Irving . . . . . . . . . . . . . . . . . . . . . . . . . 4-10 

SESSION 5: INDUSTRIAL APPLICATIONS 

Michael A. Maxwell, Chairman 

"A Review of Proposed Industrial Boiler S0 2 NSPS: Engineering 

Analyses of FGO Technology," 0. A. Pahl, C. B. Sedman*, and 

E. F. Au 1 , Jr. . . . . . . . . . . . . . . . . . . . . . . . . . 5-1 

SESSION 6: WET FGO : ADDITIVES 

Michael A. Maxwell, Chairman 

"Three Years of Organic Acid Use at San Miguel , " R. Cmiel* and 

D. Seeman . • . . . . . . . • • . . . . . . . . . . . . . . . . . 6--1 

"Enhancement of Wet Limestone Flue Gas Oesulfurization by Organic Acid/Salt Additives," J. C. S. Chang* and T. G. Brna . . . . . . 6-10 

"Comparison of the Effectiveness of FGD Additives for S02 Removal 

Enhancement and Additive Consumption," J. B. Jarvis*, D. R. Owens, 

and D. A. Stewart . . . . . . • . . . . . . . . . . . . . . . 6-25 

"Thiosulfate Additives for Lime/ Limestone Scrubbing," G. T. Rochelle*, Y. J. Lee, R: N. Ruiz~Alsop, J. C. S. Chang, and 

T. G. Brna . . . . . . . . . . . . . . . . . . . . . . . . . 6-45 

SESSION 7: POSTER SESSION 

"The Integrated Air Pollution Control System Design and CostEstimating Model {Version II)," P. J. Palmisano, B. A. Laseke, 

and N. Kaplan • • . . . . . • . . • . . . . . . . . . . . 7-1 

"FGD Cost-Estimating Computer Model , " R. J. Keeth , P. A. Ireland, 

K. S. VanWinkle, and R. E. Moser . • . . . • . . . . . . . 7-6 

"Computer Programs for FGD Data Management and Operation," M. J. Hebets, C. A. Berry, R. W. Donaldson, M. T. Johnston, and 

0. A. Stewart . . . . . . . . . . . . . . . . . . . . . . . 7-12 

*Denotes Speaker 

v i 
\ 

CONTENTS (Continued) 

SESSION 7: POSTER SESSION (Continued) 

"Simulation of Spray Dryer Absorber for Removal of S02 from Flue 

Gases," H. H. Haibodi, T. l. Pearson, R. H. Counce, and 

W. T. Davis . . . . . . . • . . . • . . . . . . .. .. .. 7-17 

"Interpretation of GADS Data," C. V. Weilert, D. B. Hammontree, 

and P. N. Oyer • . • . . • • • • . • • • • • . . . . . • . 7-22 

"Leaning Brick Stack Liners,• H. S. Rosenberg, C. W. Kistler, 

E. R. Dille, and R. E. Moser . • • • . • • • • • • . • • . • 7-26 

"100+ MW Demonstration of Dry Sodium Injection Flue Gas 

Oesulfurization," D. W. Ablin, J. J. Hammond, D. B. Watts, 

R. l. Ostop, and R. G. Hooper • • . . • . . • . • • • . . . . . 7-33 

"Operating Experience of a Retrofitted Dry Scrubber at an 

Industrial Steam Plant," R. Baldwin, J. Buschmann, and 

R. Goffredi • . • • . . • • . • • . . . . . . . . . • • . 7-38 

"Planning Maintenance for Flue Gas Oesulfur1zat1on Systems," L. N. Davidson, G. P. Miller, C. P. Wedig, and R. E. Moser 7-45 

"S02/ NOx Removal by Ca(OH) 2," P. Chu and G. T. Rochelle • • • 7-50 

"Combined 502/NOx Removal from Flue Gas by Electron Beam, " 

D. J. Helfritch • . ..•. • •• • . •.. • • . • •.• • 

"Removal of S02 and NOx from Stack Gases by Electron Beam 

Irradiation," D. 0. Ham and J. C. Person • ••.•••• 

"Description and Mechanism of limestone FGD Operating Problems 

Due to Aluminum/Fluoride Chemistry," J. B. Jarvis, R. W. Farmer, 

7-59 

7-64 

and D. A. Stewart • . • • • • • • • . • . . • • . • • . . • • . . 7-70 

· "Enhancing Double-Alkali and Lime/Limestone Flue-GasOesulfurization Chemistries to Promote NOx Removal," 

J. B. l. Harkness, R. D. Doctor, and C. D. Livengood 

"A Review of Methods for Increasing Limestone Reagent Fineness 

7-75 

for Flue Gas Desulfur1zation, " R. K. Seward and K. A. Brame • •. 7-82 

"FGO Materials Failure Causes,• P. F. Ellis, II, and R. E. Moser · 7-87 

"Shawnee 10-HW Spray Dryer/Electrostatic Precipitator Pilot Plant," 

R. A. Runyan , J. B. Barkley, J. G. Patterson, Jr. , L. J. Henson, 

and S. F. Newton . • • . • • . • • • . • • • . • . . . • . . . . 7-92 

vii 
CONTENTS 

VOLUME 2 

SESSION SA: WET FGD: OPERATIONS AND RELIABILITY (PART 1) Charles E. Dene, Chairman 

"Advanced Computer Control System with On-Line FGD Process 

Simulator," K. Kondo*, N. Shinoda, S. Hagiwara, S. Kouno, 

Y. Watanabe, and Y. Nonogaki . . . . . . . . 8-1 

"Materials of Construction Overview," G. H. Koch . . • . 8-19 

"Design and Operation of a Wet Process Based Flue Gas 

Desulfurization System Without Reheat," J. E. Smigelski* and 

L. A. Maroti . . . . . . . . . . . . . . . . . . . . . . . . . . 8-28 

SESSION 88: WET FGD: OPERATIONS AND RELIABILITY (PART 2) Robert Glover, Chairman 

"Improvements in FGD System Reliability at Springfield IL 

City Water, Light, and Power's Dallman Station," 0. W. Hargrove, Jr.*, 0. P. DeKraker, E. Riordan, B. Buecker, 

D. Myers, and D. A. Stewart . . . . . . . . . . . . • • . . . . . 8-54 

"Investigation of Mist Eliminator Reliability Problems at Utah 

Power & Light's Hunter Station," G. Betenson*, 0. W. Hargrove, Jr., 

C. A. Brown, D. P. DeKraker, and D. A. Stewart . . . . . . . . . 8-66 

SESSION 9A: SPRAY DRYER FGD 

Charles B. Sedman, Chairman 

"Limestone Spray Drying Absorption for S02 Control," 

E. S. Joens*, K. S. Felsvang, and R. Madhok ..... 

"Comparison of Dry Scrubbing Operation of Laramie River and Craig 

9-1 

Stations," J. B. Doyle*, B. J. Jankura, and R. C. Vetterick . . 9-22 

"Dry Scrubber Operating Experience at the North Valmy Station," 

L. Smith*, L. Garrity, and R. Goffredi . . . . . . • . . . . . 9-31 

"JoyjNiro Utility Spray Dryer FGD Operating Experience- An 

Update," J. R. Donnelly*, G. W. Tracy, M. T. Quach, K. S. Felsvang, 

R. L. Ericksen, and J. G. Eutizi . . . . . . • . . • . . . . . • 9-52 

*Denotes Speaker 

v i ii 
CONTENTS 

SESSION 98: DRY FGD TECHNOLOGIES 

Richard G. Rhudy, Chairman 

"Status of Calcium-Based Dry Sorbent Injection S02 Control," 

R. Rhudy*, H. McElroy, and G. Offen ••..• • • • •••. . 9-68 

"Pilot-Scale Studies of S0 2 Removal by the Addition of CalciumBased Sorbents Upstream of a Particulate Control Device, " 

G. Blythe*, V. Bland, c. Hartin, H. McElroy, and R. Rhudy •. .. 9-84 

"Current Status of In-Duct Scrubbing Technology," K. R. Murphy* , E. A. Samuel, and H. W. Pennline . • . . . • • • • • • • • 9- 106 

"Development and Pilot Plant Evaluation of Silica-Enhanced 

Sorbents for Dry Flue Gas Desulfurization," W. Jozewicz*, 

C. Jorgensen*, J. C. S. Chang, C. B. Sedman, and T. G. Brna . . • 9-123 

"Dry/Semi-Dry Flue Gas Oesulfurization Using the lurg1 Circulating Fluid Bed Absorption," R. E. Graf* and J. D. Riley ••.•• . .. 9-145 

SESSION 10: FGD BY-PRODUCT DISPOSAL/UTILIZATION 

Dean H. Golden, Chairman 

"Engineering and Design Aspects: Disposal and By-Product Utilization of FGD Residues,• R. W. Goodwin • •••. . • 

"Effect of Wet lime FGO Operating Conditions on Improving Pa~ticle 

Size and Dewatering of Sludge," L. B. Benson*, F. Baczek, 

10-1 

R. H. Golightley, and J. A. Wilhelm . . • • • . • • • • • • • • . 10-20 

"Design Considerations for FGD Solids Disposal/Utilization at a 

Power Plant with limited Space , " J. A. Hengel*, R. G. Chapman, and D. W. Wilterdink . • • • . • . • . • • • • • . • • • • • 10-40 

"Evaluation of Washing Alternatives for FGO Byproduct Gypsum Production," J. D. Colley*, S. H. Gray, D. A. Stewart, and 

J. A. Wilhelm • • • • . • • • • • • • • • • . . • • • • • . • 10-57 

"Design of Waste Management Systems for Calcium Spray Dryer FGD 

Technology," A. P. Klimek*, A. G. Eklund, G. W. Dawson , and 

D. H. Golden • •• • • • •..•• ~ . • • • • • • • • • • • • . 10-76 

"Influence of Particulate Control on Waste Management : Integrated Environmental Control Pilot Plant Results," J. E. Cichanowicz, 

P. H. Maroney* , and S. A. Davidson . • • . • • • . • . . . 10-98 

LIST OF ATTENDEES . . . . . . . . . • • • • • • • • . . . . . A-1 

*Denotes Speaker 

ix 
PREFACE 

The Tenth Symposium on Flue Gas Desulfurization was held in Atlanta, 

Georgia, November 17 through 21, 1986. This Symposium, jointly sponsored by EPRI and EPA, had as its objective the exchange of technical information 

regarding FGD systems and processes applicable to utility and industrial 

boilers. 

Thirty-nine papers and seventeen posters were presented by EPA and EPRI 

staff members, representatives of utility companies, equipment manufacturers, 

research and development companies and university researchers. Specific topics discussed in symposium presentations included Federal and State clean 

coal programs, the commercial status of FGO in the United States, Europe and 

Japan, FGO economics, acid deposition issues, industrial applications of FGD, 

wet FGD additives, wet FGD operations and reliability, spray dryer FGD, dry FGD technologies, and FGD by-product disposal and utilization. Participants in a poster session presented information on a variety of topics varying from 

computer applications to FGD chemistry to materials failure causes. 

The Proceedings of the Tenth Symposium have been compiled in two 

volumes. Volume 1 contains papers from the following sessions: 

Session 1: Opening Session/Clean Coal Programs Session 2: Status of FGD 

Sessions 3A/38: FGD Economics: General/ 

Acid Deposition Retrofit Applications Session 4: Acid Deposition Issues 

Session 5: Industrial Applications Session 6: Wet FGD: Additives 

Session 7: Poster Session 

Contained in Volume 2 are papers presented in these sessions: 

Session 8: Wet FGD: Operations and Reliability 

Sessions 9A/9B: Spray Dryer FGO/Dry FGD Technologies Session 10: FGD By-Product Disposal/Utilization · 

The assistance of Janet Mangum, .Radian Corporation, in compiling these 

Proceedings is gratefully acknowledged. 

X 
A Review of Methods for Increasing 

Limestone Reagent Fineness for 

Flue Gas Desulfurization 

by: Roland K. Seward and Kenneth A. Brame 

Kennedy Van Saun Corporation 

Danville, PA 17821 

ABSTRACT 

Evolving technology in flue gas desulfurization (FGD) by wet limestone 

scrubbing has indicated that finer limestone slurry products might be 

needed to improve so2 removal efficiencies. For new FGD installations 

this is not a problem because the engineer can design limestone slurry 

preparation facilities to meet his needs. ~owever, at existing FGD 

facilities where there is a need for a finer limestone product, the 

problem becomes acute. This paper presents process/operating 

modifications which will maximize the fineness of the limestone slurry 

for an existing FGD unit. A review of limestone grinding system field 

data will illustrate the effects on limestone product size of .work index 

grindability, system feed rate, cyclone feed percent solids and other 

process variables. In addition, operating methods to maximize fineness 

will be presented. Effects of classification on system efficiency and 

limestone product size will be explained. 

STATEMENT OF PROBLEM 

Bench and commercial scale demonstrations have shown that limestone 

reagent fineness has a significant effect on limestone utilization. 

The results indicate that high utilization is achieved when the 

limestone size distribution is 80 to 90 percent passing 44 micron (325 

mesh) (1, 2, 3, 4). This size is equivalent to 92 to 98 percent passing 

74 micron (200 mesh). The majority of limestone grinding systems in 

operation were designed to produce limestone coarser than this optimum; 

however, in many of these systems fineness can be increased. 

EVALUATION METHOD 

The fineness obtained from a closed circuit ball mill system with 

cyclone classifiers can be limited by either specific energy defined as 

the energy required to reduce a unit weight of limestone from a given 

feed size to a given product size, expressed in kilowatt-hours per 

metric ton (KW-HR/MT), or separation obtainable by the cyclones. In 

order to determine a measure of a limestone grinding system's specific 

energy requirements, a bench scale ball mill test, called a Work Index 

Test, is performed on a given limestone. A survey of 300 limestone 

samples exhibited a range in work indexes from 4.2 to 13.3 KW-HR/ST with 

an average of 8.8 KW-HR/ST (5). The Work Index is used to calculate 

actual specific energy requirements of given limestones at various 

product finenesses. Since ball mills essentially draw constant power, 

mill capacity is found by dividing the mill power draw by the specific 

energy requirements of the stone for a given Work Index, feed and 

product size. 

7-82 
0 

1- II < 

0:: 

W(!) 

zz 4 

o .... ..JI- <J< >-..J <J:::> :z 

<.J 

a:: 

~ 0 

a:: 

:z $ 

<no o-' so -~ ..Jw 45 0> Ulo ~ 1-w 

m~ lS (.)..J a:<.J 

w>- 30 

o.<.J 

~ 

~ .. 

~ 100 0:: (.J:Z •• •• -o Z:..J IL 1!1 • 

C'-W ""a: • 

> 

~~ ~ 

%~ · ..J 1!5 

1- <.J Z>-

w (.) (.) 10 a:: 

w 

Q. 

CYCLONE FEED PERCENT SOLIDS 

FlGURE 3 

EFFECTS Of CYCLONE FEED PERCENT SOLIDS ON 

REAGENT FINENESS, DENS{TY, AND REClRCULATlNG RAT£0 

>-

a: 

w 

~ (.) 

w 

a: 

a 

.-----~C15~~~ :_ 6· c_YC-:..::..:::..:: N:.;ES::.::> ___ ___, 

0 

• 

• 

• 

• 

.FIB.D DATA 

2 

-fXTRAPOLATIOH 

0 .• 00 1.00 2.00 3.00 4.00 S.OO 11.00 7.00 11.00 t.OO 

RECIRCULATING RATIO 

FIGURE 4 

RECOVERY AT 74 MICRON (200 MESHl VERSUS 

RECIRCULATING RATIO 

7-83 
Figure 1 shows a plot of specific energy versus percent passing 74 

microns in the product. This Figure is based on 8, 10 and 12 Work Index 

limestones crushed to give a distributed feed of 19 mm (3/4") top size. 

This Figure also assumes properly sized cyclones have been selected for 

the circuit. Figure 1 can be used to estimate the highest obtai nable 

system capacity if the cyclones are able to make the desired separation. 

An operator of a i imestone grinding system needs to be aware of the 

following conditions which effect speci fic energy requirements and thus 

produce a finer reagent: 

Decreasing system feed rate increases energy available 

for grinding • 

• Insure the mill is charged with the proper size grinding 

balls and draws full power. 

Reducing the size of the limestone feed to the system 

will reduce the specific energy requirements . 

Generally, grinding systems are designed for a 10-12 

work index limestone; use of a lower work index 

limestone will decrease specific energy requirements. 

DATA 

If a system is not specific energy limited, it may be cyclone separation 

limited. Cyclone separation is a function of cyclone diameter, feed and 

associated overflow density, and feed size distribution. 

Each diameter cyclone has a limited fineness it will be able to produce. 

The fineness limit is also effected by the cyclone feed and overflow 

density. For a given feed size and density, smaller diameter cyclones 

are able to make a finer separation than larger cyclones. 

Figure 2 shows field data collected from 101 mm (4"), 152 mm (6") and 

254 mm (10") cyclones, wit h similar feed size. If desired fineness is 

98 percent minus 74 micron (200 mesh), 101 uun (4") or 152 mm (6") 

cyclones are required and must be operated below 35 percent solids 

cyclone overflow density. 

Figure 3 shows field data collected from 152 mm (6") cyclones. The 

percent minus 74 micron (200 mesh) in the cyclone overflow is a function 

of cyclone feed percent solids, and decreases rapidly beyond 58 percent 

solids. The cyclone overflow percent solids is also a function of 

c yclone feed percent solids. Fineness is maximized at less than 35 

percent solids cyclone overflow (less than 54 percent solids cyclone 

feed) . This range also yields desirable recirculating ratios and 

recovery to overflow. 

7-84 
Recirf~~at~ng ratio is defined as the weight of limestone (dry weight) 

in the cyclone underflow divided by the weight of limestone (dry weight) 

in the cyclone overflow. The recirculating ratio is a measure of the 

amount of material returned to the mill by the classifier. Recovery to 

overflow is defined as the weight of dry material passing 74 micron (200 

mesh) in the cyclone over flow divided by the weight of dry material 

passing 74 micron (200 mesh) available in the cyclone feed . (The 

cyclone feed has the same size distribution as the mill discharge.) 

Recovery is a measure of the amount of product size particles recovered 

by the cyclone. 

Figure 4 shows the relationship between recovery and recirculating 

ratio . Typical cyclone recovery range is . 55 to .65. Low recoveries 

yield high recirculating ratios and inefficient grinding. In this 

condition, limestone that is already product size is returned to the 

mill and receives energy that could be better used on larger particles. 

Lowering the cyclone feed density will lower recirculating ratio and 

increase recovery. Low recirculating ratios (less than 1) and high 

recovery is an indication that the cyclone could accept a coarser feed 

size, specific energy requirements have been met, and the mill capacity 

could be increased. 

SOLUTION 

Fineness can be increased in many syste~s by simply maintaining the 

cyclone overflow density below 35 percent solids. 

If desired fineness is met and recovery is high but circulating ratio is 

low it may be possible to increase capacity and maintain fineness by 

increasing circulating ratio. 

To estimate the capabilities of an existing system, use Figure 1 to 

estimate the maximum obtainable mill capacity. Use Figure 2 to 

determine the limitations of cyclone classifiers. 

REFERENCES 

1. Colley, J. D., Hargrove, 0. W. and Stewart, D. A., "Effect of 

Limestone Grinding Circuit on FGD Performance and Economics". 

Paper presented at the 8th Symp . on FGD. New Orleans, LA. 1983. 

2. Colley, J . D., Glover, L. R., Donaldson, T. and Stewart, D., 

"Process Troubleshooting at a Utility Limestone FGD System". 

Paper presented at the 8th Symp. on FGD. New Orleans, LA. 1983 

3. Stewart, D., Colley, J . D. , Hargrove, o. W. and Jones, J. A., 

"Limestone Selection and Preparation for FGD" • . Paper presented 

at the 9th Symposium on FGD. Cincinnati, OH. 1985. 

4. Chang, C. S. J . , Brna, G. T. and Kaplan, N., "Effects of 

Limestone Type and Grind on Dual Alkali System Performance". 

Paper presented at the 9th Symp. on FGD. Cincinnati, OH. 1985. 

5. Gaughenbaugh, D. L. and Linn, R. J . , "Wet Limestone Grinding 

for Flue Gas Desulfurization". Paper presented at the 1986 

SME-AIME Fall Meeting. St. Louis, MO., September 7-10, 1986 . 

7-85 
>-

<.!) 

0:: 

UJ 

z 

UJ 

u 

u.. 

(..) 

32 

16 

12 

UJ 8 

!}; --THEORET I CAL 

...... 

l: 

(fl 

UJ 

X: 

0 

0 

N 

'OJ 

z 

0 

0:: 

(..) 

-l: 

~ 

['.. 

(fl 

::=» 

z 

-l: 

tz 

UJ 

(..) 

0:: 

UJ 

Q.. 

4+---~------~--~--~------~--~--~ 68 76 80 88 92 96 100 104 

PERCENT M[NUS 74 MICRONS C200 MESH> 

FIGURE 1 

SPEC[FIC ENERGY VERSUS REAGENT FINENESS 

FOR t9MM X 0 LIMESTONE FEED 

OFIELD DATA IOIHII <4'> CYC\.OHES 

80 o FIELD DATA 15311 <8•> CYCLOIE9 

0 fiELD DATA 2S4HII no•> CYQ.ONE5 

- EXTRAPOLA TIOM 

PERCENT SOLIDS CYCLONE OVERFLOW 

FIGURE 2 

PERCENT MINUS 74 MICRON C200 MESH) VERSUS 

CYCLONE OVERFLOW PERCENT SOLIDS 

7-86