Department of Mechanical Engineering, KAIST, Daejeon 305-701, Korea (Received 31 March 2002; accepted 18 June 2002)
! "# $% &' (. ) * +,- . /0 12 34 56 789
:; < =(. >?/ 34@ AB,C DE F? GHI JB 789 KL
MNO 789 DP@ QR S , TU V W . NO XY @ :Z S(. * [ . \], G^ _`^, a _`^ bc Qd . e S(. fg(700oC)C 7^h 789 ^i a cm . NO jN S(. XY k l[C mnh CO, CxHy, CO2 op A n* q,C r
W XY 34@ , s * W t S(. . auv 56 wU xy@ z{| , N I . 34 789 "# w < 34@ @ GJ S(.
Abstract−The information on the processes of volatile combustion and devolatilization is important in designing and oper- ating the combustor of solid waste fuels of which volatile proportion in the combustible is very high. The aims were to com- pare the reactions of the waste fuels having different origin and to sort out their own distinguishable characteristics that are important in designing the FBC(fluidized bed combustor). Waste fuels were selected to examine their characteristics of pyrolysis and combustion in a laboratory scale combustor in which a nearly single particle combustion condition was reproduced. Wood, paper sludge, sewage sludge and RDF were selected and the fuel particles whose characteristic lengths were a few centimeters were injected into a fluidizing environment of 700oC sand in the thermally maintained reactor. By introducing some experimental parameters such as the rate and the fraction of carbon conversion, the combustion characteristics of the fuels were checked for the two separated processes of devolatilization and char combustion. Additional experimental work was carried out to determine the influence of the high water content of sludge fuels on its combustion process. The comminution effects on the combustion process of the large fuel particle were rechecked by performing the experiments for the wood particles of various size. The meanings of the fuel combustion characteristics in designing of FBC were checked and some design strategies were suggested.
Key words: Devolatilization, Solid Waste Fuel, Char Combustion, FBC
1.
!. " #$ % &'
;<= >?@ AB@C D ![1, 2].
&' D EF G HIJ ( K
G LM NO ! PQ RS@T &' UAC VW2X !.
_(V &'` aC bcd[3].
X9 3 e<, fg hi K [
Rj (. X9 kl, -. \X ,m n, - . op LM q ; a rs. tu v X9 rt3 op LM q ; PQ
wx !) X rt Rj yz
B;[4, 5].
2{|2 } X9 ~ U [ (
†To whom correspondence should be addressed.
E-mail: smchoi@kaist.ac.kr
40 4 2002 8
M ) C r U [ / ;=) !.
b X9 rt U I[ B
=) !Cm tG ( x ;V [4]. @ X9
,I/ rtG @C (V X9
rtG >?-C o U@T rs G ,I }X rt ¡
¢G £[( a.
2.
Fig. 1 wx wB !) ¤z rt 7 ¥ x 3F@C m¦}§.
wx !) @C ¨= © ª B« ¬
, © eg , K'X l. B ®7[ d. 7B
e> ¯° ±²., e., ( ³G ®B
¶j ; ·_.m ^G ®B.
LM ¸¹ º';¹ m»)2 ¸¹
7B ¼¨=X º';¹ kl, ½ >«d [
t ª 2q [ )¼. \ ]^7 eI ¾¿
wx(X +b( [< yz ·À (m ¸
¹/º';¹ Á3 2 '. wx Âx @B Á3 wB(
*$ ¸¹ º';¹ à U ±² ^G ®B(V
© ª B«G IÄ . K1m ±²d rt Åd B;[ Æ Ç È Ã ( ®B( a ÉÊ(.
wx 7B rt I ®Bd ,I Ë3 © ^
G @_(V ¸¹ º';¹ © ª B«F#G ®6Ì
º';¹ EÐ= , G ®B( a. kl,
¸¹Ñu ÒÓp º';¹3 = ^ J Ë3, ¸¹
« f3, Á3 ³7 ´ +b op Ôp¼.
kl, >y \ X9 ¶j kl, ¸¹/º';¹
^G ®B( a ÕÖ yzI¼. wx !) ¸¹/
º';¹ Á3 wx ¯° 2( I
kl, -., ×kl Ë3, kl, 7B U B;[ ¤ @.
3.
3-1.
<¡ Fig. 2 ´ 2Ø 100 mm ÙTÚ C u#)
¼ \ 1,100 mm ¬Û . ¸¹ £Ü 2 Ø 550µmT ÝÞ )ßC \ 200 mmX à J Ë3 Á 0.15 m/sec. J [ á
[ [(V } Á3 OB(M 2Ì !3â wx(ã. [ Ð Ë@C äå=) ,
f3 B )¼. CO CO2 [ B >,« @á æç f3 B, J (Hydrocarbon, CxHy) Jè ÁJç f3
B, « ¶j tç B[ _d. , ÐSd é¥ êë I ìí <d.
3-2.
¸¹ Á3[ 700oC 2= îÝ X9
² ÂO ½ ¾ Â( 5 g I= .)
±²(X : o [(CO2, CxHy, CO, O2) B ®7 ÛI
X9 ² ,I, 7BG (ã. J [ e
·_ïC ,I 7BG Ì P e Ué ª[
J [ ·_(V ²[ 9( ¸¹ H« , t (ã[6]. Fig. 2 d a7 ´ º';¹ «(20 Nl/min)
ð²(V 7B lñd ,I ñt(kl,)G ò.
H« , ,I ×kl 7B ó ô õ
×kl 7B öm Y J [ ª e b÷(
V ò. ×kl 7B öm Y O«J ½ «J
lñ Õ m¦m2 ø YC æBï. EçC
×kl 7B7 õ 7BG ,'I Ì [ !§.
Bd CO2, CxHy CO f3 _(V d .G x«(
Fig. 1. Schematic diagram for the relation between fuel properties and FBC design parameters.
ãC aC b÷ Ë3(rate of carbon conversion, 1/sec),
n ^(carbon recovery, %)7 £Ü b÷ :(mean carbon conversion time, sec) ³G x«(ã. # T Table 1 B'=
) !C ù I Eç7 x b ld úQ û=§
[7-9].
3-3.
U X9 mH, û
= ( 012, û2 012, K'X üý(pellet)C
tþd RDF(refuse derived fuel) äÿ(ã. Table 2 U
, ®7 m¦}§. mH B$9(2×2×2 cm), RDF ¬
(2Ø 2 cm, \ 2 cm) þÇ 012 2Ø 2 cmT ) ' þÇ iß. U [, y kl, -. 85%- 88%
Rj \. õ [ t,G [B(X ¬ , ®7 _($ b9 . y kl, -d . "Ì !. m H 70%, ( 012 68%, û2 012 68%, RDF 79% [ k l, y %( aC x«=§.
4.
4-1.
² L[ cmT >?@ X9 7B ²
, 7B Rj yz ÃÌG [10]. G Û I ² 7 , 7BG (ã. mH d ( 012
¶j õ ¾ ² m») ¼¨= d û2 0 12 [ H'` P|2 ² þG 2(ã. $
RDF J ó ) ² ¦ aG Ì [ !
. M d û2 012 ( 012 ó
¸¹ ² þÇ n,G ô8. û2 012 n, ²
±² Þ þÇ 2(X !C ( 012 ¶j ¾
² ¾¼ þÇ[ =§.
4-2.
U d 4[2 UI J [ e
®7 ª b÷(V ¸¹ û ,I
®7 Fig. 37 Table 3 m¦}§C 3n ®7
£Ü.
n ^ e ð² ¶j Ý UI 90% 3Ô (ãC ®7 e ð² ¶j X9 ² ±²d U
, [ [ [(CO, CO2, CxHy) Ð=) [ , I n d aG . K1m J [ ª [
$ kl, = Ã º';¹ « ð²
Ð|2=) } kl, 9: Ò¼.
Ð Á3[ µX : ,(2 ø PQ
lñ(V n ^ Table 3 ®7 ´
; µM m.
Fig. 3(a) ×kl 7B õ b÷= YG J
Fig. 2. Lab-scale fluidized bed combustor.
N=
∫
0tBQ C( CO+CCO2+CCxHy)dtTable. 2 Results of ultimate analysis, proximate analysis and calorimetric analysis of the fuels
Fuels Water
(%)
HHV (cal/g)
Dry base
Combustible (%) Ash
C H O N S Volatile Char Sum (%)
Wood 6 4,200 49.8 5.2 44.5 <.01 <.01 85 15 100 <.1
Sewage sludge 74 2,100 17.6 3.0 14.6 2.8 <.01 32 6 38 62
Paper sludge 57 2,400 27.9 4.2 27.9 0.4 <.01 50 9 59 41
RDF 4 5,600 51.2 7.6 23 1.4 <.01 72 11 83 17
40 4 2002 8
(ãC a U w ld úQ ù §
[7]. t op : 2u b÷ Ý
È [2 þÇ ,` !. Fig. 3(a) mH d 01 2 ×kl 7B7 õ 7B ,= · ¶¢G ;
m, RDF õ I( : M m¦m2 ø a G ! !. RDF ² ¶j È 7B y"=) O)m X !. ² , rt 7B ®B@T ÃÌG aC # Âd. kl, -. U@C \C $M 2X %ÜO L
/ õ ² 2 t¢ RDF ¶j ù(M
¼ ² u#) &C Rj 'M ¼¨d. ¼ ²
« « Ë3 ;<( PQ ×kl, õ 7B ÝÈ[ '
M ¼¨d. ®7@C $M 2 ² ¶j ×kl 7B 7 õ 7B , (M m¦m2 ø.
4-3.
Fig. 3(b) ®7 Z Í w ,I ®
7. J [ ª ·_ ×kl 7B7 e b÷ ) õ 7B (M ,= aG ! !. $M
õ [ 'M ¼¨=) ×kl 7B7 õ 7B , )*
*+ RDF ¶j3 È 7B (M ,=X !.
®7 >?(V ×kl 7B b÷ þÇ LM q ;2 ø.
b÷ Ë3 , ! ×kl Ë3 H« ÷¶
op LM 2 ø aG TÌ !.
Fig. 3(b) 100 A ×kl 7B Ý7 Ë3[
û2 012 ûá m-2 [ ÝÈ >.(M m¦mX !. ×
kl 7B UI x«d £Ü b÷ : 102-129
op LM q m2 ø. ² þÇ[ 2= d û2 012 ¶j ² } ×kl 7B I lñd kl, È /+ n,G Û7IÄ ( PQ ×kl 7B V1 DC
2 >?(V 0'M ¼¨= aC #Âd. K1m õ
Ë3 : op , rt PQ LM Ôp 2 a Td. õ Ë3 $M 2 RDF ¶j[ [<
\X ² þÇ[ 2= d û2 012 ¶j [< µ.
4-4. ! "
Z Í ®7 ² L[ 2 cm ¶j ² ,
]7[ t ¢G ð aG , !§. ×kl 7B ó
3 ² þÇ[ >?@ 1 2= mH L 2J3 ²
L[ ¡ ¢G @C 4;5. Fig. 4 mH
² L 1, 2, 3 cm(2 6) 2J3[$ ®7
[8]. ² L[ G â 'M [= PQ Ë3[ 7 [( aG b÷ Ë3 , [ !.
Table 4 ®7 ² ·8[ G P mH ¶j n ^
9)2 a ×kl Ë3 7[[ :^G 2m¡M \ V G OCò PQC #Âd. £Ü :C
L[ ;2$ : 7[( ¶¢G (M ! !.
4-5. #$% & '( )*
012 , -. \Ò l. µ PQ ; -
< =m ±²( b d. 012
, -. o rt 012 wx !)
yz(.
Fig. 3. Fraction and rate of carbon conversion: dry wood, paper sludge, RDF, sewage sludge, Tbed 700oC, flow rate 120 Nl/min(0.86 m/sec), size : 2 cm, fluidization gas : N2, air.
Table 3. Carbon recovery(%), mean conversion time tc(sec)
Case Wood Sewage sludge Paper sludge RDF
Combustion environment Air Fig. 3(a)
T(oC) C_Rec. tc C_Rec. tc C_Rec. tc C_Rec. tc
Total 95 113 91 134 92 192 97 93
Pyrolysis N2→air Fig. 3(b)
Total 85 151 89 186 90 249 89 124
Volatile 59 115 51 102 50 129 75 118
Char 26 36 38 84 41 120 14 6
¶j B* Cp¼. , -. ² þÇ DÐ ! x E)$ $M RDF ´ þÇ 7B ¼¨=
aG , !. £Ü b÷ :G ;$ ,-. 7[($
F)m[ N)¹ aG Table 5 TÌ !. ,-.
\ ¶j ² ,[ 012 7BG 2( aG , !.
±²d ² © ×kl 7B ,7 kl,
' m[$ ñ8 } GÚ I ,d. õ 7B
×kl 7B ó å@I¼ ² · HI I ²
,d. , 7B ² L N PQ ® 7 ´ G I¼= ÃÌG .
5.
wx/+b [< yz ·À (m ¸¹/º'
;¹ Á3 2 '. õ t, >I kl, -. \ 01 2, BR, X, kl, ðz ¬ =
PQ ¸¹ º';¹ kl, .G Í(V . e G à@JIÄu ¸¹ º';¹ Á3 @Í(M 2Ì !.
Fig. 6 rt7 wx x :J(M B'
(ã. ,I/ G ûe(X
¢G . ´ @C ®=) ! È
¥_C ¸¹ º';¹ :^ ®Bd
. :^ rt op Ôp2 +b
G 2JKC a Í [L(. wx 7B ,I/ rtG X*(V aG û)Ì !3 â wx G wBIÄ .
Fig. 4. Fraction and rate of carbon conversion : wood, Tbed 700oC, flow rate 120 Nl/min(0.86 m/sec), size 1, 2, 3 cm cube.
Table 4. Carbon recovery(%), mean conversion time tc(sec)
case wood(cube)
Size (cm) C_Rec.(%) tc(sec)
1 83 51
2 94 105
3 97 166
Fig. 5. Fraction and rate of carbon conversion: sewage sludge, water 0- 67%, paper sludge, water 0-63%, Tbed 700oC, flow rate : 120 Nl/
min(0.86 m/sec), size : 2 cm, fluidization gas : air. Fig. 6. Fuel properties connected to the FBC design.
40 4 2002 8
®7 ;V U D
rtG ¸¹/º';¹ Á3 2p wx Y
£[( a ¤z(.
RDF ´ l. \X $M 2 'M (
¸¹ 9: X ¼ ù ² >«7 º';¹ b
d kl, I º';¹ :^G [y !.
U>(V º';¹ Á3 ' 2q EA ÝM
=)Ä Ì aC #Âd. ¶j l. \ PQ ¸
¹ Á3 2( a )N2 ø2u à@ 3Ô( I º';¹ 9:, 2q e ð², e>, e "Á3 ´ wx T wB ùÏ ð [ zd.
,G . - 012 l. Rj µ PQ ¸¹ Á 3 2( I ; ´ á ¬ ¤z(.
[ w¡=) 012[ ±²= b = ¶j,
^ op rt Ôp2 aG wx wB IÄu
. , -. / ¶j Ë3[ 9)22u 7B
$M 2 PQ b9 : B* d 012;
Ò¼. 012 ² , -. \G â ² ¸¹ 9
: Ò2X ¸¹ Á3[ 9)¼. P kl, ¸¹ ^
O (=) kl, Ã º';¹ Ì [Lt
!. ¸¹ Á3 2( I ¸¹ EÐ.G 7[
! 7 ´ õ t, / [ ; @(. RDF m mH ´ kl, -. / ; ·_Ì ¶j
J e "Á3 wB ð [ z= ; ·_.
ûU wB=2 øG ¶j º';¹ :^G 2m¡M \O
!
6.
_ } X9 ² © ,I G ¨ (ã. ®7 X9 o ,I © r tG £[Ì !§.
, rt rt Rj ¢G ð§. × kl 7B ?3[ @I2 RDF ¶j ¸¹ ²[
$M ,=) ×kl7B7 õ 7B O)m b9@
C 'M ¼¨= a T=§. ² ,[ @M O )m ² þÇ[ 2= mH, d ( 012 û2 01 2 ¶j Âx@C ¼¨=§.
H« ¸¹ ÷¶G t-C , rt ? P-
Ý UI ×kl 7B7 õ 7BG ,Ì !§. × kl 7B op LM 2J[ Æ2u õ
, rt op LM ¢G Q5.
012 ¶j , -. op rt 2( aG TÌ
!§. , -. \Ò2$ , 7B I ×kl 7 B 0*22u ó [ ,=$ ×kl 7B7 õ
ÝÈ[ [Ë= aG TÌ !.
¸¹/º';¹ Á3 2p wx Y ®
7 ;V U D rtG £[(ã.
+,-. /
C* : concentration of CO, CO2, CxHy(CH base) [mol/Nm3] f : fraction of carbon conversion [%]
fC : carbon mass fraction from element analysis F_rate : flow rate [l/min]
HHV : higher heating value [cal/g]
MFC : mass flow controller mfuel : mass of fuel input [g]
n : mole number [mol]
N : total mole number [mol]
C_Rec : carbon recovery [%]
Q : combustion gas flow rate [Nm3/sec]
t : time [sec]
: overall burnout time [sec]
tc : mean carbon conversion time [sec]
! "#
1 Hodgkinson, N. and Thurlow, G. G.: AIChE symposium series, 73, 109(1977).
2. Lee, J. K., Lee, K. H., Jang, J. G., Lee, N. S., Lim, J. S. and Chun, H. S.: HWAHAK KONGHAK, 30, 228(1992).
3. Jacobs, J. P.: Chem. Eng. Science, 54, 5559(1999).
4. Bautista-Margulis, R.G., Siddall, R.G. and Manzanares-Papayanop- oulos, L.Y.: Fuel, 75, 1737(1996).
5. Winter, F., Prah, M. E. and Hofbauer, H.: Combustion and Flame, 108, 302(1997).
6. Kim, J.-S., Kim, S.-J., Yun, J.-S., Kang, Y. and Choi, M.-J.: HWA- HAK KONGHAK, 39, 465(2001).
7. Lau, I. T. and Friedrich, F. D.: AIChE symposium series, 84, 89(1980).
8. Choi, J., Park, Y. and Choi, S.: HWAHAK KONGHAK, 39, 629(2001).
9. Choi, J., Park, Y. and Choi, S.: J. Korean Solid Wastes Eng. Society, 18, 1(2001).
10. Arena, U., Cammarota, A. and Mastellone, M. L.: Fuel, 77, 1185(1998).
tB
