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Babcock & Wilcox 1

M. MaryamchikD.L. Wietzke

Babcock & WilcoxBarberton, Ohio, U.S.A.

Presented to:POWER-GEN International 2000November 14-16, 2000Orlando, Florida, U.S.A.

Circulating Fluidized Bed Design ApproachComparison

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AbstractThe paper provides an annual update of the latest exper iencewith commercially operating B&W IR-CFB boilers. Addition-

ally, this paper presents a technical comparison of CFB boilersolids separation designs. A number of case studies are analyzedfor different boiler capacities and fuel types , for both greenfieldand retrofit applications.

IntroductionThere are two major types of CFB boilers competing in

today’s market: hot-cyclone type and impact-separator type. Thehot-cyclone type unit has many varieties including plate cy-clones, cooled cyclones, square cyclones (Compact) and inter-nal furnace cyclones (CYMIC ™). Each of those features

cyclone(s) immediately following the furnace along the gas path,for separating solids from gases leaving the furnace.

The impact-separator type features a two-stage solids sepa-ration system with a primary stage being an impact-type solidsseparator located at the furnace exit and providing separationof the bulk of the solids. It is arranged as an array of U-shapedbeams (U-beams). The secondary separation stage is located inthe lower gas temperature region of the boiler convection pass(may vary among projects from 150C to 500C). This stage car-ries out collection of the finest fraction of circulating solids andemploys either a mechanical dust collector (MDC) or the firstfield(s) of an electrostatic precipitator (ESP).

Babcock & Wilcox (B&W) and its licensees have mastered

the latter type of a CFB boiler. As the majority of or all solidscollected in the U-beams are I nternally R ecycled within thefurnace, the design is named “ IR -CFB.”

Experience UpdateLong-term B&W CFB performance can be illustrated by the

operational data from the boiler at Ebensburg, Pennsylvania,firing waste bituminous coal (Figure 1). (1,2) This unit, designedfor 55 MWe capacity (211 t/hr steam flow), for the number of years has operated at ~10% overload due to increased load de-mand. Boiler performance and availability are shown in Table 1and Figure 2, respectively. This boiler has about 2/3 of its sol-ids collected in U-beams recycled internally with the remain-

ing 1/3 recycled through an external loop.In later designs, represented by two boilers currently in op-eration, solids circulation from the primary collector back tothe furnace became entirely internal. (3,4) The first one, shown inFigure 3, is located at Southern Illinois University (SIU) inCarbondale, Illinois, U.S.A. and is designed for 35 MW t outputfor cogeneration application, utilizing high-sulfur, low-ash Illi-nois coal. This boiler features MDC as a secondary solids col-lector. Boiler performance and availability are shown in Table2 and Figure 4, respectively.

The second boiler (Figure 5) is located at Kanoria Chemi-cals & Industries Ltd. (KCIL) in Renukoot, India and is designed

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for 81 MW t output for captive power requirement, firing high-ash, low-sulfur coal. This boiler was supplied by Thermax B&WLtd., a joint venture company of B&W and Thermax of India.This project utilizes the first two fields of ESP as a secondarysolids collector. Boiler performance and availability are shownin Table 3 and Figure 6, respectively.

Table 4 is a chart comparing the design features of B&W IR-CFB and Hot-Cyclone CFB.

New Design ApplicationsThe following projects in progress will be used as illustra-

tions for the current IR-CFB design approach.

EC Tychy S.A., Poland

A boiler for Elektrocieplownia EC Tychy S.A. power plant,Tychy, Poland (Figure 7) will produce 700 klb/hr (317 t/hr) steamof 1740 psia/1005F (120 bar/540C). The boiler wil l fire a blendof high-ash bituminous coal with up to 5% by heat input of biofuels. The contract was signed in June 2000, and commer-cial operation is expected in late 2002.

Table 1Ebensburg Operating Data

Operating Steam Flow, t/hr (klb/hr) 234 (516)

Steam Flow @ MCR, t/hr (klb/hr) 211 (465)

Steam Temperature, C (F) 512 (953)

Steam Pressure, MPa (psig) 10.6 (1540)SH Steam Temperature Control Range, % 30-110

Load Turndown Ratio Without Auxiliary Fuel 5:1

EmissionsNO x, ppm (lb/10

6 Btu)

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Table 2SIU Operating Data

Steam Flow @ MCR, t/hr (klb/hr) 46 (101.5)


Steam Pressure, MPa (psig) 4.4 (640)

SH Steam Temperature Control Range, % 40-100

Load Turndown Ratio Without Auxiliary Fuel 5:1


6 Btu)

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Table 3Kanoria Operating Data

Steam Flow @ MCR, t/hr (klb/hr) 103 (227)


Steam Pressure, MPa (psig) 6.2 (884)

SH Steam Temperature Control Range, % 60-100Load Turndown Ratio Without Auxiliary Fuel 5:1


6 Btu)

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Figure 7 Tychy IR-CFB boiler.

Figure 8 Size comparison of PC boiler firing anthracite culm and its repowering CFB boiler.

CFB Boiler PC Boiler (TP-230 type)

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1. Belin, F. et. al., “Coal Fired CFB Boilers—Babcock &

Wilcox’s Experience,” International Joint Power GenerationConference, San Diego, California, October 6-10, 1991.

2. Alexander, K.C. and Eckstein, T.G., “Maintenance Expe-rience with Circulating Fluidized Bed Boilers,” CompetitivePower Congress ’94, Philadelphia, Pennsylvania, June 8-9, 1994.

3. Belin, F. et. al., “Update of Operating Experience of B&WIR-CFB Coal-Fired Boilers,” 15 th International Conference on Flu-idized Bed Combustion, Savannah, Georgia, May 16-19, 1999.

Copyright © 2000 by The Babcock & Wilcox Company,a McDermott company.

All r ight s reserved.

No part of th is work may be publi shed , trans lated or repr oduce d in any form or by any means , or incor porat ed into any informat ion ret rieval system,without the written permission of the copyright holder. Permission requests should be addressed to: Market Communications, The Babcock & WilcoxCompany, P.O. Box 351, Barberton, Ohio, U.S.A. 44203-0351.

Disc laim er

Although t he information prese nted in this work is be lieved to be reli able , this wo rk is pub lished wit h the underst anding that The Babcock & WilcoxCompany and the authors are supplying general information and are not attempting to render or provide engineering or professional services.

Nei ther T he Babcock & W ilcox Company nor any of its employees make any warranty, guarantee, or representat ion, wh ethe r expr esse d or implied,with respect to the accuracy, completeness or usefulness of any information, product, process or apparatus discussed in this work; and neither The

Babc ock & Wilcox Company nor any of i ts employees shall be l iabl e for any loss es or damages with resp ect to or result ing f rom t he use of , or theinability to use, any information, product, process or apparatus discussed in this work.

4. Maryamchik, M. and Wietzke, D.L., “B&W IR-CFB

Boiler Operating Experience Update and Design,” Power-GenInternational ’99, New Orleans, Louisiana, November 30-De-cember 2, 1999.

5. Berdin, S.V. and Shaposhnik, D.A., “Prospects of UsingCirculating Fluidized Bed Technology in Power Plant Retro-fits,” Tyazholoye Mashinostroyeniye (Heavy Mechanical Engi-neering—Russian magazine), 2000 (in Russian).

References

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