1.
 Observation of Wall Erosion in a Circulating Fluidized Bed Reactor
 

     

^†
 



  

(2001

Observation of Wall Erosion in a Circulating Fluidized Bed Reactor

Si-Moon Kim, Jong-Min Lee^†, Jae-Sung Kim, Euy-Hyun Kim and Jong-Jin Kim

Power Generation Laboratory, KEPRI, KEPCO, Daejeon 305-380, Korea (Received 17 September 2001; accepted 12 December 2001)



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Abstract−The wall erosion characteristics of a circulating fluidized bed reactor(0.25 m-L×0.62 m-W×10 m-H) was observed with various operating conditions, such as fluidizing velocity, total solid inventory and primary to secondary air ratio. The ero- sion rate was affected by solid hold-up and solid circulation rate as well as fluidizing velocity which were varied due to oper- ating conditions. The wall erosion in dilute phase of the CFB riser increased with increasing solid hold up resulted from increasing of the fluidizing velocity and the primary to secondary air ratio. The erosion of the wall in dense phase increased with increasing fluidizing velocity although the solid hold up decreased with fluidizing velocity. The extent of erosion in the transition phase was somewhere in between the dense and the dilute phases. The erosion of the roof of the CFB riser increased with increasing solid circulation rate resulted from increasing the fluidizing velocity, total solid inventory and primary to sec- ondary air ratio. The middle part of the roof where the solid circulation rate was higher than that of the side part of the roof, showed the highest erosion rate. The erosion seemed to be serious at the area around the cyclone inlet duct due to the enlarged down flow of the solid particles at this area.

Key words: Circulating Fluidized Bed, Wall Erosion, Solid Hold-up, Solid Circulation Rate

1.  

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†To whom correspondence should be addressed.

E-mail: jmlee@kepri.re.kr

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 H"?4 V a ~# Y 2¦§ iT aT E•L ‘1 ? ¢zŽ

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 H"?I "f º>[9, 10].

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 QR(riser, cyclone, downcomer, loopseal,

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Q[Loopseal, 0.1 m(I.D.)] YJ %

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 loop Ë%# ¢=(7 N ÌQ &[FBHE, fluidized bed heat exchanger, 0.3 m(L)É0.3 m(W)É0.5 m(H)] ST(

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Fig. 1. Cold model circulating fluidized bed reactor.

Table 1. Position and size of the erosion sample plate

Sample plate Position(m) Size(W×L×t)(m)

Front 0.1-0.150 0.05×0.05×0.015

0.35-0.40 0.05×0.05×0.015

0.95-1.00 0.05×0.05×0.015

3.05-3.10 0.05×0.05×0.015

5.45-5.50 0.05×0.05×0.015

6.00-6.05 0.05×0.05×0.015

8.95-9.00 0.05×0.05×0.015

Rear 8.95-9.00 0.05×0.05×0.010

Side 0.95-1.00 0.05×0.05×0.015

3.05-3.10 0.05×0.05×0.010

5.45-5.50 0.05×0.05×0.010

6.00-6.05 0.05×0.05×0.010

8.95-9.00 0.05×0.05×0.010

Roof 10.00 0.10×0.10×0.010

10.00 0.10×0.10×0.010

10.00 0.10×0.10×0.010

 40 2 2002 4

2-2.


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Fig. 3. Effects of fluidizing velocity and solid inventory on axial solid hold-up in the CFB riser; (a) 100 kg, (b) 150 kg, (c) 200 kg.

Fig. 2. Details of erosion sample plate.

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Fig. 4. Effect of fluidizing velocity on solid circulation rate with differ- ent particle size.

Fig. 5. Erosion at different height of the riser(U_o=3.2 m/s, solid inventory

=150 kg).

 40 2 2002 4

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Q
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: ‰ ~# ­(X>. Y?/, :x à 3% ûÜ F ÁQ UV| 3%4 %0 ,, ýþF UV üx ‰m$ ÷t4 %0 ~# E•">.

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˜\%  2ó %ˆ¨ C  UV ¹F E•
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  L /&K: 3 UV  Fig. 7. Effect of solid inventory on erosion at different height of the riser.

Fig. 8. Effect of secondary air on erosion at different height of the riser.

Fig. 6. Effect of fluidizing velocity on erosion at different height of the riser.

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% ' "-:x à 3% uv  ©ª 3% Œ1 +,

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OH2 G > ¢” ' ²a ;:T ? 2 N ~#  G¼>.

 

¸ S @OKJÐ A”@O½8 O×ak "# 2

±(X#‚, : ‰aB>.



a : decay constant in transition region [m⁻¹] d_p : particle size [m]

h : height [m]

H_d : dense bed height [m]

H_exit : exit height [m]

K : decay constant in dilute phase [m⁻¹] U_mf : minimum fluidizing velocity [m/s]

U_o : superficial velocity in the riser [m/s]

U_t : terminal velocity [m/s]

 

ε : void fraction [-]

ε_exit : volume fraction of solid at exit [-]

ε_s : volume fraction of solid [-]

ε^*_s : the lowest volume fraction of solid in the riser [-]

ε_sd : volume fraction of solid in the dense bed [-]

ρ_s : density of solid [kg/m³] ρ_g : density of gas [kg/m³]



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Fig. 10. Erosion of the upper part of the riser wall.

Fig. 9. Effect of fluidizing velocity on erosion at the roof of the riser.

 40 2 2002 4

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