• Journal of Hydrogen and New Energy
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• v.21 no.5
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• pp.425-434
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• 2010

Integrated gasification combined cycle (IGCC) is an efficient and environment-friendly power generation system which is capable of burning low-ranked coals and other renewable resources such as biofuels, petcokes and residues. In this study some process modeling on a conceptual entrained flow gasifier was conducted using the ASPEN Plus process simulator. This model is composed of three major steps; initial coal pyrolysis, combustion of volatile components, and gasification of char particles. One of the purposes of this study is to develop an effective and versatile simulation model applicable to numerous configurations of coal gasification systems. Our model does not depend on the hypothesis of chemical equilibrium as it can trace the exact reaction kinetics and incorporate the residence time calculation of solid particles in the reactors. Comparisons with previously reported models and experimental results also showed that the predictions by our model were pretty reasonable in estimating the products and the conditions of gasification processes. Verification of the accuracy of our model was mainly based upon how closely it predicts the syngas composition in the gasifier outlet. Lastly the effects of change oxygen are studied by sensitivity analysis using the developed model.

• Carbon letters
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• v.2 no.3_4
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• pp.176-181
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• 2001

A series of activated carbons were prepared from coconut shells and coal-tar pitch binder by physical activation with steam in this study. The effect of variable processes such as activation temperature, activation time and ratio of mixing was investigated for optimizing those preparation parameters. The activation processes were carried out continuously. The nitrogen adsorption isotherms at 77 K on pellet-shaped activated carbons show the same trend of Type I by IUPAC classification. The average pore sizes were about 19-21${\AA}$. The specific surface areas ($S_{BET}$) of pellet typed ACs increased with increasing the activation temperature and time. Specific surface area of AC treated for 90 min at temperature $900^{\circ}C$ was 1082 $m^2/g$. The methylene blue numbers continuously increased with increasing the activation temperature and time. On the other hand, iodine numbers highly increased till activation time of 60 min, but the rate of increase of iodine numbers decreased after that time. This indicates that new micropores were created and the existing micropores turned into mesopores and macropores because of increased reactivity of carbon surface and $H_2O$.

• Clean Technology
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• v.20 no.1
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• pp.64-71
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• 2014

We have investigated the effects of various additives on Eco coal gasification under $CO_2$ atmosphere. The temperature ranges from $750{\sim}900^{\circ}C$ and the gasification experimental was carried out with Eco coal adding 7 wt% $K_2CO_3$, $Na_2CO_3$, $CaCO_3$, Dolomite, and non-additive under $N_2$ and $CO_2$ gas mixture. At $850^{\circ}C$, we observed that the reaction rate increased when the concentration of $CO_2$ increased. However, we also observed that the increment of reaction rate was small at more than 70% of the concentration of $CO_2$. The additives activity was ranked as 7 wt% $Na_2CO_3$ > 7 wt% $K_2CO_3$ > non-additive > 7 wt% Dolomite > 7 wt% $CaCO_3$ at $850^{\circ}C$. At the temperatures of $750^{\circ}C$, $800^{\circ}C$, $850^{\circ}C$, and $900^{\circ}C$, when the temperature increased, the gasification rate increased. The gasification was suitably described by the volumetric reaction model. Using volumetric reaction model, the activation energy of Eco coal including 7 wt% $Na_2CO_3$ gasification was 83 kJ/mol, which was the lowest value among all the alkaline additives.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.5
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• pp.552-559
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• 2008

Three dimensional numerical analysis were performed to investigate the combustion characteristics in a tangentially fired pulverized coal boiler. The predicted values at the outlet of economizer for the gas temperature, O$_2$, NO, CO were been compared with the measured data. By using the actual operating conditions of the power plant, the distribution of velocity, gas temperature, O$_2$, CO, CO$_2$ and NO as well as the particle tracking in the boiler were investigated. Throughout the present study, the non-uniform distribution of flue gas temperature in front of the final superheater might be resulted from the residual swirl flow in the upper furnace of the boiler. The present analysis on non-uniform distribution of the gas temperature could provide the useful information to prevent the frequent tube failure from happening in the final superheater of the tangentially coal-fired boiler.

• Journal of Hydrogen and New Energy
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• v.27 no.6
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• pp.693-701
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• 2016

Steam gasification of low rank coals is possible at relatively low temperature and low pressure, and thus shows higher efficiency compared to high rank coals. In this study, the gasification reactivity of four different Indonesian low rank coals (Samhwa, Eco, Roto, Kideco-L) was evaluated in $T=700-800^{\circ}C$. The low rank coals containing $53.8{\pm}3.4$ wt% volatile matter in proximate analysis and $71.6{\pm}1.2$ wt% carbon in ultimate analysis showed comparable gasification reactivity. In addition, $K_2CO_3$ catalyst rapidly accelerated the reaction rate at $700^{\circ}C$, and all of the coals were converted over 90% within 1 hour. The XRD analysis showed no significant difference in carbonization between the coals, and the FT-IR spectrum showed similar functional groups except for differences due to moisture and minerals. TGA results in pyrolysis ($N_2$) and $CO_2$ gasification atmosphere showed very similar behavior up to $800^{\circ}C$ regardless of the coal species, which is consistent with the steam gasification results. This confirms that the indirect evaluation of the reactivity can be made by the above instrumental analyses.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.1
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• pp.53-59
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• 2015

Combustion characteristics for co-firing of biomass (Walnut Shell) as blending fuel in coal fired boiler have investigated using thermogravimetric analyser (TGA) and drop tube reactor (DTR). The results show that devolatilization and char combustion for WS occurs at lower temperature than those of existing coals and has lower activation energy value, which is resulting in higher reactivity. When the WS is blended with coal, TGA results show linear profiles depending on blending ratio for each fuel. However, DTR results exist the non-additive phenomena for blending of WS. As blending ratio of WS increase, the UBC decrease at BBR 5%, but the UBC rather increase from BBR 10% due to oxygen deficiency formed from rapid combustion of WS. This paper propose that fuel lean condition by oxygen rich lead to higher blending ratio of biomass by solving the oxygen deficiency condition.

• Applied Chemistry for Engineering
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• v.22 no.3
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• pp.312-318
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• 2011

We have investigated the kinetics and catalytic activity of $CO_2$-lignite gasification with various metal precursors as catalysts. $K_2CO_3$, $Mn(NO_3)_2$, and $Ce(NO_3)_3$ were used and impregnated on a coal using an evaporator. The gasification experiments were carried out with the low rank coal loaded with 5 wt% catalyst at the temperature range from $700{\sim}900^{\circ}C$ and atmospheric pressure with the $N_2-CO_2$ reactant gas mixture. The catalytic effect on the gasification rate of the low rank coal with $CO_2$ was determined by the thermogravimetric analyzer. It was observed that the low rank coal reached the complete carbon conversion regardless of the kinds of catalysts at $900^{\circ}C$ from the results of TGA. The catalytic activity was ranked as 5 wt% $K_2CO_3$ > 5 wt% $Mn(NO_3)_2$ > 5 wt% $Ce(NO_3)_3$ > Non-catalyst at $900^{\circ}C$. The gasification rate increased with increasing the temperature. The activation energy of the catalytic gasification with 5 wt% $K_2CO_3$ was 119.0 kJ/mol, which was the lowest among all catalysts.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.131.2-131.2
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• 2010

서부 발전 태안화력발전소에 건설 예정인 IGCC Demo plant의 설계 자료를 근거로 석탄 가스화기의 정상 상태 전산모사를 PRO/II를 사용하여 수행하였다. 석탄을 PRO/II가 받아들일 수 있는 성분으로 바꾼 후 가스화기를 버너와 가스화기 본체의 두 부분으로 나누어 모델링하였다. 버너는 단열조건의 Gibbs Reactor로 모델링하였다. 모사 결과 산소가 완전 소진될 때까지 반응이 진행되는 것을 확인하였다. 가스화기는 char gasification 반응은 kinetic reaction equation으로, gas phase reaction은 equilibrium reactor로 모사하는 알고리듬을 개발 하였으나 PRO/II의 기능에 한계가 있어 간단한 Gibbs Reactor로 모사하였다. 가스화기는 membrane wall에 의하여 냉각되는 것을 고려하여 $1550^{\circ}C$의 균일한 온도에서 반응이 일어나는 것으로 고려하였다. 전산 모사 결과 주요 성분의 조성이 실제 syngas의 조성과 5% 정도 오차가 있는 것으로 나타났다.

• Journal of Energy Engineering
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• v.11 no.3
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• pp.269-275
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• 2002

Experimental studies are carried out to find the behavior of sulfur compounds which are evolved during high temperature pyrolysis of coals at the smelting reduction process for iron ore. Three kinds of bituminous coals, such as Hunter & Mt. Thorley (Australia), and Ensham (South Africa) are used. And forms of sulfur compound and their amounts are analyzed at the temperature ranges of 800~110$0^{\circ}C$. Then H$_2$S is the major gas, but CS$_2$ and COS are minor gases. Sulfur compounds in three coals are distributed into the volatiles (gas & tar) and coal char as the ratio of approximately 50%：50%, respectively.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.227-227
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• 2003

흑연(graphite), 석탄(coal), 숯(char), soot(검댕이) 등의 탄소로 이루어진 재료들은 비정질부터 완전한 흑연결정까지 다양한 구조를 나타낸다. 이러한 탄소재료의 구조의 출발물질 뿐 아니라 열처리에 따라 강한 영향을 받는다 이러한 구조는 여러 구조인자에 의해 특성화되는데, 구조인자로는 층간거리 d, 결정립 크기 Lc 그리고 결정립 직경 La이다. 이런 구조 인자의 지식은 흑연화, 탄소화, 가스화 등과 같은 다양한 공정을 이해하는데 매우 중요하다. 많은 연구자들은 XRD, Raman 분광, 고분해능 TEM 등과 같은 여러 기술을 통하여 이러한 구조인자에 대한 해석을 시도하였다. 그 중 XRD는 정량적 분석에 있어서 가장 많이 이용되는 기술이다. XRD 회절피크의 위치로부터 층간거리 d를 구할 수 있으며, 결정립 크기 Lc 및 결정립 직경 La는 피크의 line 퍼짐(반가폭)으로 직접 구할 수 있다. 한편 섬유상 흡착제로 이용되는 등방성 탄소섬유는 이산화탄소 또는 수증기에 의해 쉽게 활성화되어 최고 약 2,500 $m^2$/g의 고 비 표면적을 얻을 수 있다. 이렇게 활성화 후 고 비표면적을 나타내는 이유는 좁은 분포를 나타내는 미세기공의 기공구조 때문에 발생하는 것으로 알려져 있다.