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삼화 원탄과 무회분탄의 촉매(K₂CO₃) 가스화 반응성 비교 연구
공용진(Yongjin Kong),임정환(Junghwan Lim),임영준(Youngjoon Rhim),전동혁(Donghyuk Chun),이시훈(Sihyun Lee),유지호(Jiho Yoo),이영우(Young-Woo Rhee) 한국청정기술학회 2014 청정기술 Vol.20 No.3
석탄의 가스화는 촉매 도입 시 온순 조건에서 가능하나, 석탄 내 회분에 의한 비활성화에 의해 반복적인 촉매 활용이 힘들다. 이에 본 연구에서는 삼화 원탄에서 회분을 제거하여 삼화 무회분탄(ash-free coal, AFC)을 제조한 후 가스화 반응성을 원탄과 비교하여 알아보았다. 우선 원탄을 대상으로 고정층 반응기에서 수증기 공급량, 공간 속도(space velocity), 온도 및 촉매를 변수로서 가스화 조건을 결정하였다. 고체상 혼합법으로 다양한 촉매 도입 시, 유동성을 갖는 K₂CO₃가 가장 높은 활성을 보였다. 무회분탄은 원탄보다 낮은 반응성을 보였으며, 이는 용매(1-methylnaphthalene, 1-MN)를 이용한 고온 추출 및 건조 공정 중에 소모된 산소 기능기 함량과 증가된 탄화도(carbonization)에 기인한다. K₂CO₃ 가 혼합된 무회분탄의 반응성은 급격히 증가하여 낮은 온도 (700 ℃)에서도 높은 전환율을 보였다. 이때 H₂/CO와 CO₂/CO 비율도 증가하는데, 이는 촉매에 의해 수성가스전환(water-gas shift) 반응이 활성화됨에 기인한다. 본 연구에서는 무회분탄의 저온 촉매 가스화 반응을 통해 석탄 가스화 공정의 경제성이 개선될 수 있음을 확인하였다. Catalytic gasification of raw coals at mild condition is not realized yet mainly due to deactivation of catalysts via their irreversible interaction with mineral matters in coal. In this work, the gasification behavior of ash-free coal (AFC) was compared with that of the parent raw coal. In order to modify the gasification conditions, the raw coal gasified with fixed variables (water supply, space velocity, temperature, catalysts) in a fixed bed reactor. When catalysts are added by physical mixing method with coal, K₂CO₃ was the most effective additives for steam gasification of coal. However, the activity of ash-free coal (AFC) was much less reactive than raw coal due to high temperature extraction in a 1-methylnaphthalene under 30bar at 370 ℃ for 1 h, almost removed oxygen functional groups, and increased carbonization. The addition of K₂CO₃ in AFC achieved higher conversion rate at low temperature (700 ℃). At that time, the molar ratio of gases (H₂/CO and CO₂/CO) was increased because of water-gas shift reaction (WGSR) by addition of catalysts. This shows that catalytic steam gasification of AFCs is achievable for economic improvement of gasification process at mild temperature.
Priscilla, Lia,Kong, Yongjin,Yoo, Jiho,Choi, Hokyung,Rhim, Youngjoon,Lim, Jeonghwan,Kim, Sangdo,Chun, Donghyuk,Lee, Sihyun,Rhee, Youngwoo American Chemical Society 2017 ENERGY AND FUELS Vol.31 No.10
<P>Utilization of coal is currently limited to coal-fired power plants and iron smelting, partly because of the incombustible ash in coal and the inability of existing technologies to modify its properties. This work investigates whether the gasification behavior of ash-free coals (AFCs) can be modified. Sixteen different AFCs were prepared using variously ranked coals (Eco, Cyprus, Drayton, and Hail Creek) and extraction solvents with different polarities (N-methyl-2-pyrrolidone, ethylenediamine, 1-methylnaphthalene, and tetralin). Next, the reactivities of the AFCs in steam gasification at 800 degrees C were tested, and the results are discussed taking into consideration their compositional differences. A combination of low-rank coals and polar solvents produces reactive AFCs that can be catalytically gasified under mild conditions. In contrast, AFCs extracted using nonpolar solvents are less reactive and possibly applicable as a carbon electrode precursor. In short, the properties of AFCs can be changed to some extent using the appropriate combination of coals and extraction solvents.</P>
Torrefaction Effect on the Grindability Properties of Several Torrefied Biomasses
( Daru Setyawan ),( Jiho Yoo ),( Sangdo Kim ),( Hokyung Choi ),( Youngjoon Rhim ),( Jeonghwan Lim ),( Sihyun Lee ),( Dong Hyuk Chun ) 한국화학공학회 2018 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.56 No.4
Torrefaction is the promising process of pretreating biomass materials to increase the quality of their energy, especially to upgrade the materials’ grindability so that it is suitable for a commercial pulverizer machine. In this study, torrefaction of oak, bamboo, oil palm trunk, and rice husk was carried out under different torrefaction temperatures (300 ℃, 330 ℃, and 350 ℃) and different torrefaction residence times (30, 45, and 60 minutes). Complete characterization of the torrefied biomass, including proximate analysis, calorific value, thermogravimetric analysis, mass yield, energy yield, and grindability properties (Hardgrove Grindability Index) was carried out. Increasing the torrefaction temperature and residence time significantly improved the calorific value, energy density (by reducing the product mass), and grindability of the product. Furthermore, for commercial purposes, the torrefaction conditions that produced the desired grindability properties of the torrefied product were 330 ℃-30 minutes and 300 ℃-45 minutes, and the latter condition produced a higher energy yield for bamboo, oil palm trunk, and rice husk; however, torrefaction of oak did not achieve the targeted grindability property values.
Nickel supported on low-rank coal for steam reforming of ethyl acetate
Ruhswurmova, Nikola,Kim, Soohyun,Yoo, Jiho,Chun, Donghyuk,Rhim, Youngjoon,Lim, Jeonghwan,Kim, Sangdo,Choi, Hokyung,Lee, Sihyun Elsevier 2018 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.43 No.33
<P><B>Abstract</B></P> <P>Ethyl acetate is a volatile organic compound (VOC) that has emerged as a major environmental pollutant and also one of representative components of bio-oil. In this study, mostly metallic Ni particles (size: <10 nm) were finely dispersed on low-rank coal (LRC) by the ion-exchange process. Catalytic steam reforming of ethyl acetate (EA) was performed over Ni supported on Eco LRC (Ni/Eco) to reduce EA emissions and simultaneously produce H<SUB>2</SUB>. EA reforming over 17.7 wt% Ni/Eco at 400 °C results in H<SUB>2</SUB> yield of 70%–80%; this is comparable to that achieved with reforming over commercial Ni/Al<SUB>2</SUB>O<SUB>3</SUB>. Advantageously, metallic Ni particles are dominant over Ni oxides on LRC, and therefore, the pre-reduction step routinely required for an alumina-supported catalyst can be skipped. Furthermore, deactivation by coking is slower with Ni/Eco than with Ni/Al<SUB>2</SUB>O<SUB>3</SUB> during long-term operation, probably because of the smaller particle size and preferential adsorption on the coal support.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nano-dispersion of Ni on low rank coal (LRC) is achieved. </LI> <LI> LRC-supported Ni catalyses the steam reforming of ethyl acetate. </LI> <LI> Ni particles on LRC are mostly in active metallic form. </LI> <LI> Ni on LRC is less susceptible to coking-related deactivation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>