7NÏ îB BBj *‚ Zinc Titanate B– 5 >wßW

7NÏ îB BBj *‚ Zinc Titanate B– 5 >wßW

ªcêÁN'²Á;ž“Á~KÁšê^†ÁfÒc*

'Î&v wÏz¦

*ã§&v z"

(1999j 5ú 31¢ 7>, 1999j 9ú 28¢ j)

A Study of Advanced Zinc Titanate Sorbent for Mid-Temperature Desulfurization

Chang-Jin Lim, Young-Kwon Cha, No-Kuk Park, Si-Ok Ryu, Tae-Jin Lee^† and Jae-Chang Kim*

School of Chemical Engineering and Technology, Yeungnam University, Kyongsan 712-749, Korea

*Department of Chemical Engineering, Kyungpook National University, Taegu 702-701, Korea (Received 31 May 1999; accepted 28 September 1999)

º £

Cê&Ê 7~ z>²¢ B–~V *~ zinc titanate îB¢ B–~ ÚîÎW 5 >wßWj ’~&. 7N

–š~ î;ö Î"'ž îB¢ B–~V *~ Î&B‚ Co3O₄f NiO¢ ÒÏ~& ÚîÎWj ËçÊV *

~ MoO3¢ Î&~&. B–‚ îB~ ÚîÎê¢ G;~&, î>wj 650^oC~ N" 480^oC~ 7NöB >¯

~  ‡>ËKj jv ¦Æ~&b– 480^oCöB 50-cycle ËV³>wj >¯~  ‡>ËKj &V~&. zBÞ, î.Özbj ŽF‚ zinc titanate îB& 480^oCöBê Nî>w(650^oC)öB~  ‡>ËK" F҂ Ö"¢ &

b– 50-cycleÿn  ‡>ËK~ 6²º z 'f ©b‚ ¾æÒ. Ò zB îB¢ 580^oCöB ÒVb– Ë V³ >w ê îB~ bWæz¢ –Ò~&.

Abstract−Zinc titanate sorbents to remove H₂S in the coal gasifier gas were formulated and their attrition resistances and reactivities were studied through the multicycle operation in a laboratory scale. In the preparation of sorbents Co₃O₄ and NiO were added to the formulation for the development of the more efficient sorbents at the mid-temperature operations as well as MoO₃ was added for the improvements in the sorbent attrition resistance. Attrition test for the prepared sorbents were per- formed by utilizing the ASTM air jet attrition method. The desulfurization tests for the new formulations were also carried out at 480^oC to make a comparison between the sulfur capacities of the new sorbents and those of the first generation of sorbents developed for high temperature operating condition. The 50-cycles of the sulfidation and regeneration for a superior formula- tion, which is selected based on the attrition tests, were performed at 480^oC to investigate its chemical and physical properties.

The result showed that the desulfurization efficiency of the selected sorbent containing the cobalt and nickel oxides was slightly better than the zinc titanates without metal oxides at 650^oC. The sorbents were regenerated at 580^oC and investigated the changes of the physical properties of the sorbents after the multiple cycle.

Key words: Zinc Titanate, IGCC, Desulfurization

1. B †

Cê²&Ê~ ¦Öbž  &æ šbî~ B–& *Òf 

¾~ ~ã', ãB'ž GšöB º’>Úæ ®b– š šbî 7  zb~ B–& &Ë – "Ïj A ®. V¢B CêšÏ b‚¦V šbîj ‚²z† > ®º Ó;CêVF~ BBš .

® º’> ®.

Ó;CêšÏVF~ ¢~b‚ Cê&ÊzB*(Integrated coal Gas- ification Combined Cycle: IGCC)ʂf ¾~ ~ãBö &¾†

> ®º VF‚ 99%~ Fª B–, 90%~ NOxB– 5 35%~ š

Özê² B–& &Ë~. 6‚ Vš~ Cê B*~ ÎNš 34%ž

– >š IGCC~ ÎNf 42-52%‚ Ö ¸ B*& 5 R¶j&

Ô[1]. IGCC ;f ’² Cê&Êz‚, &Ê;B 5 B*¦ªb‚

’W>Ú ®b– î;f &Ê;B¦ªö ³~º ©b‚ &Êz‚

öB W>Ú ¾Jº Cê&Ê 7~ H2S 5 COS¢ B–~V *‚

®ÚB &Ë – ^B6b‚ æ'> ®º Cêš ŽF~º Wª f Cê&Êz& ê¯>º ÿnö &¦ªš H2S‚ *~> ¢¦&

COS 5 CS2‚ *~B. šr WB H2Sº VÚnöB ò&Ê¢

²† r ÖWj~ "ºöžš >º SO₂‚ Öz>Ú ~ã'ž Gš

öB ë·Ïj ~² B. 6‚ H2S~ ³ê& ¸f ãÖ(> ppm) VÚn~ ÆBf ž Ëj¾ Ë~¢ ¦Ò > ®bæ‚ ò&

†E-mail: tjlee@ynucc.yeungnam.ac.kr

z B38² B1^ 2000j 2ú

ÊöB H2S~ ³ê¢ > ppmš~‚ ÔºÚ "Ú¢ ‚.

šf ?f šF‚ Nš î;f Úç~ .³Özb î

B¢ ÒÏ~ Cê&Ê7~ H₂S¢ ZnS~ ;‚ ‡>~º î

;, H2S ‡>‚ žš zB îB¢ O2Öz>wj Û~ .³Ö zb‚ Ò~º Ò;, Ò SO2 7~ j ²>~º ²>

;b‚ ’W>Ú ®[2]. ß® N~ VçöB šÚæº î

;j jW~V *šBº îB~ BBš j>'š–, Nš F ÿ[ îË~ö '‚ îBº Ö>‚ îËKj &^¢ ~º © f b† ÚîÎWš Ö>š¢ ~º– *Ò š¢ ò—Ò ©b‚ V

&> ®º ©š zinc titanateîBš[3-9]. ¾, zinc titanate îBº H₂S¢ B–~º î>wš¾ j ‡>‚ îB~ Ò

>wš N(650^oC šç)öB >¯>æ‚ î/Ò cycleš >N ö Vž îB~ ²Ö*ç"  ‡>bîž zinc~ >B*ç b‚

'‚ bW&~¢ ¢bB îËK~ &~¢ .¾‚[6, 10-12]. ß

® Ò>w~ ãÖ Ö²f >w~šB /ς B*çj ÿ>~

îB~ Nêçßj ¢bÎ[10]. V¢B 7Á&NÏ îB~ B Bš .® º’>Úæ–  ’öBê jê 7NÏ îB B Bj Ï'b‚  &æ Î&B¢ ÒÏ~ ÚîÎê 5  ‡>Ë Kš Ö>‚ îB¢ BB~¶ ~&.

2. þ

2-1.jê îB~ B–

jê îBº ZnOf TiO2ö ZVW ֏B‚ α-Al₂O₃¢ I

 &æ Î&B¢ 3-10 wt% Î&~ "&öB 12*ÿn ^

֏B‚ >#~ {ÂW;V¢ ÒÏ~ W;‚ ê 100^oCöB 24

*ÿn š–B *V‚öB 1N ²WV. 1N ²W ê ï¶Ò B‚ ªê~  NöB 2N ²WÎ ê ڂ ª/~ Fÿ [ >wVö '‚ ’Vž 150-300µm «¶‚ zinc titanate îB

¢ B–~&.

 ’öB Òς îB B––šj Table 1ö ¾æÚî.

îB~ ZnO/TiO Öjº 1.5‚ ~& ZVW ֏B‚ 3 wt% α- Al₂O₃¢ ÒÏ~&. Î&Bº 10 wt% Co3O₄, NiO¢, 3 wt% MoO3¢ Î&~&.

šç" ?š B–B îB~ bWj BET ‚š' G;V(Micro- meritics Gemini 2375), Hg-porosimetry(Micromeritics AutoPore III), XRD (X-Ray Diffractometer, RIGAKU, D/May-2500), SEM(Scanning Electron Microscope, Hitachi, S-4100) j ÒÏ~ ªC~&.

2-2.ÚîÎê þ

B–B îB~ bÒ' ßWf ASTM Ïj V¢B ¶Ú B·‚

^‚ &;~ ÚîÎê G;Ë~(attrition tester)¢ ÒÏ~ îB~

ÚîÎê¢ –Ò~&[13, 14]. Attrition testerº Fÿz Ë~~ jÑ

¦ªö 3B~ ’s(0.3 mm)j &æº air-jet plate¢ J~~& j¾

‚¦V î²&Ê¢ ªÒ~ FÿzV. šr îB~ Ïêïf 50 gš Fÿz*f 5*š– î²&Ê~ F³f 10 l/minb‚ ~

&. š –šf îB¢ Fÿ[ >wVöB ËV ³'b‚ ÒÏ

† rö jº‚ ÚîÎê¢ G;~V *Žš–, ÚîÎêº Fÿz

þš ƒÂ ê Ú(sieve)¢ ÒÏ~ «¶’Vê‚ ª/šB .V «ê º*~ ºï†" *Ú ºï†j G;~&.

2-3.>wßWþ

 ’ö šÏ‚ î/Ò>wË~¢ Fig. 1ö ¾æÚî. >wV (microreactor)º Ú㚠1 cmž C'&j ÒÏ~&b– *V‚ö >

çb‚ J~~&. >wVÚ~ Nêº chromel-alumel thermocouple j îB Ïê¦~ 7ö *~~êƒ J~~ G;~&. >w&

ʺ >wV~ ~¦öB 禂 vš² ~& >w&Ê~ F³f mass flow controller‚ –.~&. >ÃV ª{j –.~V *~

syringe pump‚ >wV «’~ &ÊbVöB VzB >wV‚ F

«~&. >wV «’f ’~ linef >ÃV~ w»j Oæ~V *

~ 150^oC‚ &~ >wV¢ †^¾&º &ʺ TCD(Thermal Conductivity Detector)& ËOB GC(Gas Chromatograph, Shimadzu GC 8A)¢ ÒÏ~ ªC~&. ªCö Òς columnf Hysep Qf Porapac T

îþj *~ îB 3 gj >wVö ÏêÊ *V‚~ 7

9,500 hr⁻¹~ *³êöBê – {K¶ ìš ö~º Fïj ¾ F æ† > ®îb– >wf &V{öB >¯~&.

ÎÒ&Ê~ –Wf VªZ; Cê&Êz‚öB Ö>º Cê&

Êf F҂ –Wb‚ ~&b– î 5 Ò~ Fïf 250 ml/min b‚ ~&. z>wš ·>š ¢;‚ * *Ïb‚ >wV Â

Table 1. Ingredient and condition of zinc titanate sorbents preparation by extrustion method

Sorbents Chief ingredient Calcination condition ZTE06 ZnO, TiO₂, α-Al2O₃ 900^oC-5 hr, 900^oC-5 hr ZTE24 ZnO, TiO₂, α-Al2O₃, Co₃O₄,

NiO, EG

300^oC-1 hr, 1,000^oC-12 hr

ZTE25 ZnO, TiO₂, α-Al2O₃, Co₃O₄, NiO, PVAc(5%)

650^oC-1 hr, 1,000^oC-12 hr

ZTE27 ZnO, TiO₂, α-Al2O₃, Co₃O₄, NiO, MoO₃, EG

1st : 750^oC-5 hr, 2nd : 1,000^oC-1 hr ZTE29 ZnO, TiO₂, α-Al2O₃, Co₃O₄,

NiO, MoO₃, EG

1st : 750^oC-5 hr, 2nd : 850^oC-30 min

Table 2. Experimental condition for zinc titanate sorbents Sulfidation Regeneration

Temperature(^oC) 480-650 580-650

Pressure(atm) 1 1

Flow rate(ml/min) 250 250

Gas composition(vol%) H₂S 1.0 O₂ 5.0

H₂ 11.7 H₂O 10

CO 19.0 N₂ balance

CO₂ 6.8

H₂O 10.0

N₂ balance

Fig. 1. Scheme of experimental apparatus.

’öB H2S ³ê~ ãæz‚ îB~ ‡>ßWj –Ò~&b–

>wV ’öB H2S~ –Wš 2,000 ppmšç >š z>wj «Ö

~&. Ò>wf î²&ʂ ’CB V¢ 10%~ Ê&" bV öB b~ îB¢ Òʖ >wV ’öB SO2& &V>

æ pj rræ Ò>wj >¯~&.

šç" ?š î-Òš ‚® ê¯B ç¢ 1-cycle‚ ~ B–

B zinc titanate îBö &~ 50-cycle ³ >þj >¯~&

.

3. Ö" 5 V

3-1.ÚîÎê þ

îB~ ڒW 5 ÚîÎW Ëçj *~ FVW ֏B 5 .

³Özb Î&B¢ IÚB B–‚ ê ÚîÎê¢ G;~&b– G;

Ö"¢ Table 3ö ¾æÚî.

b& FVW ֏B& ÚîÎêö ~º 'Ëj –Ò~V *~

ethylene glycol, polyviny acetate¢ '' îB B–ö Î&~&

ZTE25 îB~ ÚîÎêº 33.5%, ethylene glycolj Òς ZTE24 îBº 45.26%~ ÚîÎê¢ ¾æÚî. ¢>'b‚ FVW ֏

Bº ÚîÎWöº – 'Ëj "æ á~– J®J ôf ·š Î&F ãÖ Ú’Wš Ôjæº ©b‚ ¾æÒ. Ò .³Özb Î&B‚

MoO₃¢ Òς ZTE27" ZTE29 îB~ ÚîÎêº '' 86.0%

f 80.5%&b– Fÿ[;ö 'Ï&˂ «¶’Vž 100-300µm~

º*ö 'φ ãÖöº '' 93.0%f 90.6% ;ê&. ÚîÎWö

&‚ Î&B~ 'Ëj –Ò~&º– MoO3& ÚîÎêö ç‚ ' Ëj ~º ©b‚ ¾æÒ, ß® îB B– ²WNêf ²W

*ö V¢ ÚîÎWš ’² æ~º ©j r > ®î. &B 800^oC

šç~ NöB ²W† ãÖ ÚîÎê& 90% šçj ¾æÚæò 900^oC šçöBº ÚîÎWf Ö Ö>‚ >š MoO3& ²Ö>Ú îB~ "ºßWž î>wWf J®J ÎÚæº Ö"¢ .¾~

&.

V¢B  ’öBº Ö>‚ ÚîÎW" î>wWj &æº î

B~ ‚' B– –šj Table 4f ?š J;~&.

3-2.N(650^oC) 5 7N(480^oC)öB~ >wW þ

;[ microreactoröB N~ 650^oC î-650^oC Ò" 7N~

480^oC î-580^oC

¯~ >wNê &~ö Vž 'Ëj ¦Æ~&.

650^oCf 480^oCöB~ ZTE24 îB~ î>wö Vž ãæz

¢ Fig. 2, 3ö '' ¾æÚî. 1-10-cycleÿn~ 2"Ff î/Ò

 >wÅ>& Ã&†>ƒ H2S& ¦Â>º 2"*š ^Úæº ã Ëj ¾æÚ šº ZnOf TiO2òb‚ šÚê zinc titanate îB~ 2"Fš î/Ò >wÅ>& Ã&Žö V¢ 6²~º

*ç"º >&‚ ¾æÒ. Ò  >ÏËKj Fig. 4ö ¾æÚîº

– cycleš Ã&†>ƒ  >ÏËKš Ã&~ 650^oCöBº š†'ž

 >ÏËK~ 94.9%ö š~º 26.24 g S/100 g sorbent(94.9%)~ Ö

>‚  >ÏËKj & 480^oC >wöBê .VcycleöBº &–~

Table 3. Attrition resistance of sorbents prepared by extrusion method Sorbents Attrition resistance(%) Flow rate

(l/min) Total sieving 150-300µm 100-300µm

ZTE24 63.0 45.2 60.4 10

ZTE25 55.5 33.5 52.4 10

ZTE27 93.4 86.0 93.0 10

ZTE29 94.2 80.5 90.6 10

Table 4. Optimal condition of prepared sorbents(ZTE29) Condition

ZnO/TiO₂ mole ratio 1.5

Organic binder Ethylene glycol

Inorganic binder 3 wt% α-Al2O₃

Additives 3 wt% MoO₃

Calcination temperature(^oC) 1st 750^oC, 2nd 850^oC

Calcination time(hr) 1st 5, 2nd 0.5

Fig. 2. H₂S breakthrough curve of ZTE24 sorbent(650^oC).

Fig. 3. H₂S breakthrough curve of ZTE24 sorbent(480^oC).

Fig. 4. Sulfur capacity of ZTE24 sorbent.

z B38² B1^ 2000j 2ú

&æò 6N'b‚ Ã&~ 10-cycleöB 22.66 g S/100 g sorbent (81.5%)~  >ÏËKj ¾æÚî. š‚ Ö"‚ zBÞ, î.š Î

&B îB~ >wWf 7Á&N î>w–šöB .Vöº  >Ï

3-3.7N(480^oC)öB~ 50-cycle ËV>wW þ

B–‚ îB 7 ZTE24 îB& 480^oC 7NöB î>wWš

Ö>~&b– šf ‚WWª~ –Wš ?f –šöB ڒWj Ëç

Ò Ï'b‚ B–B ZTE29 îB¢ 50-cycle î/Ò ³>w

ZTE29 îB~ H₂S ‡>>wö &‚ H₂S~ ãæz 5  >

ÏËKj Fig. 5, 6ö '' ¾æÚî. 4-cycleöB  >ÏËKf ‚

& 25.64 g S/100 g sorbent(92.3%)ræ Ã&~ 10-cycleræ Fæ

>îb– šê 6N 6²~ 50-cycleöBê 17.89 g S/100 g sorbent (64.4%)~  >ÏËKj &. Ò Fig. 7ö ¾æÞ 650^oC  NöB~ ËV>wW þj >¯‚ ZTE06 îBf  >ÏËK~

6²~º ;ê¢ jv~š 480^oC~ 7NöB >¯B ZTE29 îB

&  >ÏËK~ 6²º 'f ©b‚ ¾æ¾ 7NöB ËV³ Ò ÏWš n;'ªj r > ®î. 6‚ 650^oC NöB~ >wW"

Nš& ’æ prj r > ® Co-Ni Özb Î&B¢ Òφ ãÖ 7NÏ î;ö 'Ï &ˆ ©b‚ ÒòB.

š ËV³>wö Vž  >ÏËK~ 6²öžj {ž~V *

~ îB~ bWæz¢ >w*ê~ SEM, XRD, EDX, BET ª Cj Û~ –Ò~&.

3-4. XRD ªC

50-cycle~ ËV³ î/Ò >wj >¯‚ ZTE29 .V îB f î 5 Ò >w ê~ XRD çj Fig. 8ö ¾æÚî. .V ç

~ XRD ç[Fig. 8(a)]öB Zn2TiO₄~ çš ;W>îrj r > ®

49.5-cycle î >w êöº Zn2TiO₄, ZnS, TiO₂(A), TiO₂(R), NiO

~ ßW peak& ¾æÒb– Ò>w êöº Zn2TiO₄, ZnO, TiO₂ (A), TiO₂(R), NiO~ peak& ¾æ¾ Zn₂TiO₄‚ ÒÖ;>æ á‚

Fig. 5. H₂S breakthrough curve of ZTE29 sorbent.

Fig. 6. Sulfur capacity of ZTE29 sorbent.

Fig. 7. Comparison of sulfur capacity.

Fig. 8. XRD pattern of ZTE29 sorbents.

(a) Fresh, (b) After 49.5 cycle sulfidation, (c) After 50 cycle regeneration

ZnO& î >wö Cê&Êz &Ê7~ H2f >w~ Zn~ ;

‚ >BŽb‚ î-Ò cycleš Ã&†>ƒ >wWš 6N 6²~º

©b‚ æ– EDXªCöBê Zn~ >B*çš &V>î.

3-5. SEM/EDX ªC

EDX ªCöB îB ž¦ ‚š~ Zn/Ti~ Öj æz¢ Table 5ö

¾æÚî. î-Ò cycleš ê¯>º ÿn îB ‚š~ Zn/Ti Öjº 6N Ã&~º º^¢ šº– š©f «¶Ú¦~ Znš >

B~º ";öB «¶ ž¦ ‚šb‚ {Ö>Ú ‚šöB~ ZnŽïš

Ã&~V r^ž ©b‚ º;B.

"Ò*¶*ãb‚ &V‚ ZTE29 îB~ >w*ê~ ‚šßW Ö"¢ Fig. 9ö ¾æÚî. 49.5-cycle î >wj >¯‚ îB~

‚š[Fig. 9(b)]öº ZnS Ö;š W>îrj ‚š;çb‚ {ž†

> ®îb– Ö ¦b& – sulfate~ ;Wb‚ ž‚ «¶~ f dj" > ìî. ¾, 50-cycle Ò>wš jòB îB~ ‚

š[Fig. 9(c)]f ç‚ æz& ®îb– «¶*~ ïοf *çš &

V>î ‚š;ç 6‚ .V~ zinc titanate îBfº Ò ®

‚ *çš ¾æÒ. š©f XRD ªCÖ"öB ¾æ ©" ?š

.V~ Zn2TiO₄ çj ;W~ ®~ zinc titanate îB& î/Ò

 >wÅ>& Ã&Žö V¢ Ò Zn2TiO₄~ ’–‚ ÒÖ;š š

Úææ á~ ¢¦ jš ZnO‚ Îj®rb‚ ž‚ ;çb‚ 6

B. Ö"'b‚ ZnS¢ ZnOf SO₂‚ ªÒ¢ ~&b¾ .V~

zinc titanate(Zn₂TiO₄)‚ j*‚ Òf šÚææ Ⴀ©b‚ 

ê. 6‚ îB~ ‚š'š Ã&~² >º– Table 6ö ¾æÞ ©

" ?š .V îBö j~ 50-cycle î-Ò >wê~ ‚š' f ç® Ã&~º ãËj &. š‚ ãËf ’–'b‚ n;

z>æ á~V r^ž ©b‚ 6>– –. z ê pf ’& š

Ú^¢ † ©b‚ ÒòB.

4. Ö †

Î&B¢ Òς jê îB~ ÚîÎê Ëç þ" 7&NÏ î

(1) Fÿ[;ö 'Ï &˂ îB¢ B–~V *~ Î&B‚

MoO₃¢ Òφ ãÖ 90.6% šç~ ÚîÎê¢ áj > ®îb– š

 Ö"‚ ÖÒ2šj Î&† ãÖ ÚîÎW Ëçö Î"'ªj {

ž† > ®î.

(2) 7Á&NÏ îB‚ Î&B¢ 10 wt% Co3O₄, NiO¢ Î&‚

ãÖ 480^oC~ Ôf NêöB jv' >ÏËKš ·^~– š†'

ž >ÏËK~ 92.3%ö š~º 25.64 g S/100 g sorbent~ 

>ÏËKj Fæ~&. .³ Özb Î&B¢ šÏ~ Ôf Nêö B î>wÎNj ¸¢ > ®rj {ž~&.

(3) 580^oC~ Ôf NêöB Ò>wj >¯‚ îB~ XRDö

~‚ Ö;’–¢ –Ò‚ Ö" .V~ Zn2TiO₄çš ÒöB ÒÖ;

š j*~æ á~ ZnOf TiO2~ çb‚ Îj ®b– z>w

jš >B ¶>Ú î/Ò cycleš Ã&†>ƒ >wWš 6N 6²~º ãËj ¾æÚî.

š‚ þÖ"‚¦V zinc titanate îB~ >wNê¢ 650^oC~

NöB 480^oC~ 7Nb‚ Ô > ®îb– NöB~  >Ï ËK" –~ j݂ ÎNj áj > ®î. &˂ 100-cycle šç~

‚ ڒWš º’>æ‚ ÚîÎê¢ z× çßʚ B ;ö '

6 Ò

 ’º ;¦ Öë¶ö¦~ &Úö.æVFBBÒë æöö ~š

Table 5. EDX analysis of zinc titanate sorbents Sorbents Reaction

temperature

Zn/Ti ratio

Fresh 9.5 cycle 10 cycle 49.5 cycle 50 cycle

ZTE24 650^oC/650^oC 1.73 1.95 1.94 - -

480^oC/580^oC 1.73 2.19 2.20 - -

ZTE29 480^oC/580^oC 1.71 - - 4.06 4.12

Fig. 9. Scanning electron microscopy of ZTE29 sorbent(×30,000).

a) Fresh, b) After 49.5 cycle sulfidation, c) After 50 cycle regeneration

Table 6. BET surface area of ZTE29 sorbent

ZTE29 Fresh 49.5 cycle 50 cycle

BET surface area 0.1485 m²/g 0.3878 m²/g 1.8236 m²/g

z B38² B1^ 2000j 2ú

B šÚrbæ‚ ’j æöö pf 6Ò¢ ãî.

^^ò

1. Rhee, Y. W., Lee, T. J. and Yi, C. K.: Chemical Industry and Tech- nology, 15, 237(1997).

2. Park, Y. S., Rhee, Y. W. and Son, J.-E.: Chemical Industry and Tech- nology, 11, 56(1993).

3. Lee, T. Y., Park, N. K., Kim, J. H., Park, Y. W. and Yi, C. K.: HWAHAK KONGHAK, 34, 435(1996).

4. Kang, S. H., Rhee, Y. W., Kang, Y., Han, K. H. and Jin, K. T.: HWA- HAK KONGHAK, 35, 642(1997).

5. Yi, C. K., Park, J., Cho, S. H., Jin, K. T. and Son, J.-E.: HWAHAK KONGHAK, 37, 81(1999).

6. Lee, Y. S. and Yoo, K. O.: HWAHAK KONGHAK, 32, 506(1994).

7. Gupta, R. P. and Gangwal, S. K.: Topical Report to DOE/METC, November(1992).

8. Ayala, R. E.: Topical Report to DOE/METC(1992).

9. Gangwal, S. K., Kupta, R. P. and Cicero, D. C.: Proceeding of the Advanced Coal-Fired Power System '95 Review meeting(1995).

10. Gupta, R. P. and Gangwal, S. K.: Topical Report to DOE/METC (1993).

11. Gupta, R. P., Gangwal, S. K. and Johnson, E. W.: Final Report to DOE/METC(1993).

12. Gangwal, S. K. and Gupta, R. P.: Proceeding of the Coal-Fired Power Systems ’93-Advances in IGCC and PFBC Review Meeting(1993).

13. Stephanopoulos, M. F.: U.S. patent No. 4,977,133(1990).

14. Delzen, G. A. and Porter, R. A.: U.S. patent No. 5,310,717(1994).