2. 

   

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(2001 10 10 , 2002 2 8 )

Combustion of Coal in a Bench Scale Circulating Fluidized Bed Unit

Dowon Shun^†, Dal-Hee Bae, Keun-Hee Han, Seong-Ho Cho and Seung-Young Lee

Korea Institute of Energy Research, Daejeon 305-343, Korea (Received 10 October 2001; accepted 8 February 2002)



  !"#$.
% & '(%)* +,- 4,529 kcal/kg#.  & /0% Balir Athol )

* +,-(as received)& 6,455 kcal/kg #$.   & * 123 4567 89 :);, NOx

0.061 mm > %? @    @ 96 BC& LL 57, 70%M 8N>O$.

Abstract−Combustion of a Korean anthracite and an imported bituminous coal in a bench scale circulating fluidized bed, 0.20 m I.D.×1 m-high bed and 0.25 m I.D.×10 m-high freeboard, was performed and the characteristics of combustion were compared. Test coals were anthracite received from Samchuk, Korea with the heating value of 4,529 kcal/kg, an imported Aus- tralian bituminous coal with the heating value of 6,455 kcal/kg. Both coals showed different vertical combustor temperature profiles, i.e., burning characteristics. Their trends of NO_x emission levels were also different. Combustibles loss of the tested anthracite and the bituminous coal by fly ash of particle diameter smaller than 0.061mm was significantly contributable to the combustion efficiency. Combustible loss of the fly ash smaller then 0.061 mm from the anthracite and the bituminous coal was, 57 and 70%, respectively.

Key words: Domestic Anthracite, Bituminous Coal, Circulating Fluidized Bed, Combustion

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†To whom correspondence should be addressed.

E-mail: dshun@kier.re.kr

 40 3 2002 6

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Fig. 1
Flow diagram of CFBC test facility.

1. Combustor 7. Loop seal

2. Heat exchanger tube 8. Air pre-heater

3. Cyclone 9. Bag filter

4. Coal hopper 10. F.D. fan

5. Limestone hopper 11. I.D. fan 6. Valve

Table 2. Analysis of coals

Analysis Bituminous coal

(Australia)

Anthracite (Samchuk) Proximate, wt% as received

Moisture Volatile Ash Fixed carbon Ultimate, wt% dry basis C

H N S Ash, wt% ash CaO MgO Al₂O₃ SiO₂ Fe₂O₃ Mean diameter, mm

Calorific value, Kcal/kg(As received)

7.28 26.9 9.8 55.9

66.8 3.5 1.5 0.5

5.3 3.6

0.4591 6,455

3.53 4.73 38.00 53.74

54.03 0.19 0.48 0.68

1.01 1.66 33.56

4.24 0.3937

4,529

Fig. 2. Particle size distribution of the test coals.

Fig. 3. The effect of heat input on combustor temperature.

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Fig. 4. Axial temperature distribution of imported bituminous coal and domestic anthracite.

Fig. 5. The effect of gas velocity on average particle diameters in the cyclone and the bag filter collects.

Fig. 6. The effect of dense bed gas velocity on carbon content of bag fil- ter ash.

Fig. 7. Thermogram of samchuk and blair athol coal.

 40 3 2002 6

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Fig. 8. The variation of heating value of particle by size(blair athol).

Fig. 9. Temperature effect on combustion efficiency.

Fig. 10. Proximate analysis of fly ash by particle size cut(blair athol).

Fig. 11. Proxiamte analysis of fly ash by particle size cut(samchuk).

Table 3. Weight fraction and combustible loss of fly ash by size cut

Dp,mm Blair Athol Samchuk

Fraction[-] Contribution combustible loss Fraction[-] Contribution combustible loss

0.249-0.104 0.03 0.01 0.11 0.04

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3. Choi, J. H., Son, J. E., Han, K. H., Bae, D. H. and Jo, S. H.: “Devel- opment of Circulating Fluidized Bed Coal Boiler Technology(I),” Korea Institute of Energy Research KE-91009G(1991).

4. Shun, D., Son, J. E., Park, Y. S., Ku, C. O., Han, K. H., Bae, D. H., Im, J. H. and Choi, J. H.: “Development of Circulating Fluidized Bed Coal Boiler Technology(II),” Korea Institute of Energy Research KE-920509G (1992).

5. Shun, D., Son, J. E., Han, K. H., Bae, D. H., Jo, S. H. and Choi, J. H.:

“Development of Circulating Fluidized Bed Coal Boiler Technol- ogy(III),” Korea Institute of Energy Research KE-93040G(1993).

6. Shun, D., Bae, D. H., Han, K. H., Son, J. E., Kang, Y., Wee, Y. H., Lee, J. S. and Ji, P. S.: HWAHAK KONGHAK, 34, 321(1996).

7. Shun, D., Bae, D. H., Han, K. H., Son, J. E. and Cen, K.: HWAHAK KONGHAK, 37, 925(1999).

8. Park, Y. S. and Son, J. E.: HWAHAK KONGHAK, 31, 287(1993).

9. Wartha, C., Winter, F. and Hofbauer, H: “Carbon and Fuel Nitrogen Conver- sion under Fluidized Bed Conditions,” Presented to 36th Int. Energy Agency Fluidized Bed Conversion Meeting(1998).

Fig. 12. Particle size distribution of fly ash.

Fig. 13. The effect of temperature on fuel-N conversion.

Fig. 14. Temperature effect on combustion CO emission.

 40 3 2002 6