• Journal of Energy Engineering
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• v.4 no.1
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• pp.42-51
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• 1995

준역청탄에서 무연탄까지의 등급을 갖는 8개탄을 대상으로 ASTM 방법으로 회분을 제조하였으며 회분조성과 용융온도를 측정하여 각 시료의 융착성향을 비교하였다. 보다 간단한 방법으로 정확하게 융착성향을 예측하기 위한 방법을 찾는 것을 목적으로 시료의 색을 측정하였으며 TGA를 이용하여 회분중 휘발량을 측정하였다. 또한 1$600^{\circ}C$에서 회분을 용융시키고 다시 응고시켜 제조한 연마시료를 대상으로 표면에 형성된 공동크기를 분석하였으며 회분의 색, 휘발량, 공동크기 등과 융착성향과의 관계를 고찰하였다. 분석결과 회분의 색은 회분의 융착성향을 크게 구분할 수 있는 지표로써 사용될 수 있으며 TGA에 의한 회분중 휘발량의 측정은 용융온도와, 그리고 용융후 응고시편의 공동크기는 1$600^{\circ}C$에서 계산된 점도와 밀접한 상관성을 갖고 있어 이들을 석탄회분의 융착성향 예측에 사용할 수 있음을 알 수 있다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.11
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• pp.697-704
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• 2016

Coal modified by acid treatment was investigated to analyze the correlation between the cell performance and electrochemical parameters in a direct carbon fuel cell (DCFC). The fuels were subjected to thermogravimetry analysis, gas adsorption test, and X-ray photoelectron spectroscopy to investigate the fuel properties and surface characteristics. After the treatment of raw coal, the thermal reactivity of the treated fuels increased, and the specific surface area decreased, though the mean pore diameters of three fuels were similar. The coal treated by $HNO_3$ showed the highest ratio of oxygen to carbon, and also an increase in the surface oxygen groups on the fuel surface. Through comparison between the fuel surface properties and electrochemical performance, it was confirmed that the surface oxygen groups have an influence on the improvement in the DCFC performance.

• Korean Chemical Engineering Research
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• v.50 no.1
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• pp.76-82
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• 2012

Biomass and coal are great potential energy sources for gasification process. These solids can be gasified to produce syngas and bio-oil which can be upgraded further to transportation fuel. Two biomass and three coals have been gasified with steam in a thermobalance reactor under atmospheric pressure in order to evaluate their kinetic rate information The effects of gasification temperature ($600{\sim}850^{\circ}C$) and partial pressure of steam (30~90 kPa) on the gasification rate have been investigated. The three different types of gas-solids reaction models have been applied to the experimental data to compare their predictions of reaction behavior. The modified volumetric reaction model predicts the conversion data well, thus that model was used to evaluate kinetic parameters in this study. The gasification reactivity of five solids has been compared. The obtained activation energy of coal and biomass gasification were well in the reasonable range. The expression of apparent reaction rates for steam gasification of five solids have been proposed as basic information for the design of coal gasification processes.

• Journal of the Korean Society of Combustion
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• v.15 no.4
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• pp.65-73
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• 2010

In order to provide fundamental information for developing reaction model in the practical blended coal power plants, effects of particle size and blending ratio on combustion characteristics and thermal reaction in co-firing with bituminous and sub-bituminous coals were experimentally investigated using a TGA and a laboratory-scale burner. Characteristic parameters including ignition, burnout temperature and activation energy were determined from TG and DTG combustion profiles. Distributions of flame length and mean particle temperature were investigated from the visualization of flames in slit-burner system. As coal particle size decreased and volatile matter content increased, characteristic temperatures and activation energy decreased. The ignition/burnout characteristics and activation energy are linearly influenced by a variation in particle size and blending ratio. These results indicated that the control of the coal blending ratio can improve the combustion efficiency for sub-bituminous coals and the ignition characteristics for bituminous coals.

• Journal of the Korean Society of Combustion
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• v.16 no.1
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• pp.22-29
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• 2011

This paper focuses on the combustion characteristics of blended coals with bituminous and sub-bituminous coals under air and oxy-fuel combustion conditions. The effects of oxygen concentration and blending ratio on the combustion characteristics were experimentally investigated using a thermogravimetric analyser (TGA). Characteristic temperatures including ignition, burnout temperature and activation energy were determined from TG and DTG combustion profiles. As oxygen concentration increased and the presence of sub-bituminous coal, characteristic temperatures and activation energy decreased. The ignitability, reactivity and kinetics have all been greatly improved under oxy-fuel combustion conditions. Based on this, co-firing with bituminous and sub-bituminous coals under oxy-fuel combustion conditions may be suggested as an alternative method to the fuel flexibility and cost-effective power production with carbon capture and sequestration.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.433-436
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• 2007

가스화기술은 화석연료에 의한 기존의 화력발전기술을 대체할 수 있는 차세대 발전기술로 여겨지고 있어 전 세계적으로 기술개발은 물론 상용 플랜트를 앞 다투어 도입 건설 중에 있다. 현재 국내에서도 2014년까지 실증플랜트 완공에 매진을 가하고 있는 실정이다. 가스화기술은 온실가스인 이산화탄소를 동시에 감축하면서 전력뿐만 아니라 수소, DME, 화학원료와 같은 2차 고급 에너지원을 생산할 수 있다는 장점을 가지고 있다. 이 연구에서는 ASPEN plus를 이용하여 다양한 원료 공급에 따른 300 MW급 IGCC 플랜트에 대한 운전 특성을 알아보고자 하였다. 가스화기에 공급되는 원료는 석탄(역청탄), 중질유(납사, 벙커C유) 등으로 구분해 고려하였으며, 가스화 플랜트 해석모델에 대한 성능을 평가하기 위하여 해외에서 운전 중인 상용 IGCC 플랜트에 대한 운전자료와 상대오차로 비교 산출해 검증하였다. 그 다음으로 가스화(gasification)공정, 산가스 제거(acid gas removal)공정, 복합발전 공정(combined cycle)등과 같은 IGCC 플랜트를 구성하고 있는 각각의 단위공정에 대한 운전 특성에 대한 해석결과를 확인하였다. 해석 결과를 바탕으로 가스화기의 냉가스 효율(cold gas efficiency)과 탄소 전환율(carbon conversion), 산가스 제거공정에 대한 이산화탄소 포획 성능과 복합발전에 따른 플랜트 발전량 및 발전 효율(plant net efficiency)을 예측하였다.

• Journal of Energy Engineering
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• v.19 no.2
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• pp.136-142
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• 2010

Combustion reactivity and thermal behavior of two imported coals used as a pulverized fuel of commercially thermal power plant were investigated by thermogravimetric analysis (TGA) and large scale test furnace of 200 kg/hr. TGA results showed that combustion efficiency of high moisture coal has lower than reference coal due to the slow combustion completion rate although it has the low ignition temperature, and activation energies of high moisture coal with 79 kJ/mol for overall combustion was higher than reference coal of 53 kJ/mol. Test furnace results ascertained that flame of black band of high moisture coal during the combustion in boiler broke out compared to reference coal and then it becomes to unburned carbon due to the less reactivity and combustion rate. But, Blending combustion of high moisture coal with design coal of high sulfur are available because sulfur content of high moisture coal was too low to generate the low SOx content in flue gas from boiler during the combustion. The ash analysis results show that it was not expected to be associated with slagging and fouling in pulverized coal fired systems due to the low alkali metal content of $Na_2O$ and $K_2O$ compared to bituminous coal.

• KSBB Journal
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• v.11 no.2
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• pp.238-245
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• 1996

Microbial desulfurization characterlstics of a bituminous coal have been determined by using Thiobacillus ferrooxidans. The effects of process variables (such as coal pulp density, particle size and addition of surfactants) on pyrite removal have been investigated in both shake and airlift-bioreactor culture experiments. In shake experiments, pyrite could be removed over 78% for pulp densifies below 20% (w/v) and removed below 40% for pulp densities over 30% (w/v) in 8 days. Pyrite removal decreased with increasing pulp densities, and it also decreased sharply with increasing particle sizes. In airlift bioreactor experiments, pyrite at 50% (w/v) pulp density could be removed about 50%. Its value is much higher than 15% at the same pulp density in a shake experiment. With addition of surfactants, pyrite removal was enhanced in shake experiments significantly, whereas it was slightly decreased in an airlift bioreactor experiment.

• Korean Chemical Engineering Research
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• v.51 no.1
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• pp.121-126
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• 2013

The objective of this research is to predict the TG curve of blends of bituminous coal and sub-bituminous coal during devolatilization. TSL (Thermal Shock Large) TGA was used for Experiments, and Coats-redfern method was used for reaction order calculation. Based on reaction order, sum method was verified to be suitable for a single coal, then, prediction and comparison of TG curve of coal blends was conducted using both of WSM (Weight Sum Method) and MWSM (Modified Weight Sum Method), where the latter was developed in this research. The presented experiment results and WSM & MWSM were showed to be reasonable using linear least square method. MWSM performed more accurately than WSM for the case that TG curve had different slopes and the case that sharp weight loss happened due to release of volatile matter. The results showed that it's possible to predict the thermal behavior of coal blends during devolatilization based on the thermal behavior of single coals.

• Journal of Energy Engineering
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• v.8 no.4
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• pp.553-559
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• 1999

This study has been implemented to investigate various characteristics of coals which are imported from abroad. KIER has developed 1 T/D bench-scale unit, entrained-flow coal-slurry gasification technology to investigate the followings: 1) to assess the appropriate foreign coals for gasification. 2) to establish the data base for gasification phenomena, 3) to minimize the technical risks prior to introduction of commercial scaled IGCC power plant, 4) to develop essential key technologies and to establish operational experiences for coal gasification. The foreign coals used in the gasification are Cyprus and Alaska coals from U. S. A. Cyprus coal(bituminous) and Alaska coal (lignite) were shown about 1.29$0^{\circ}C$. The concentrations of coal-slurry for Cyprus were maintained up to 58%, 62% and 65% in order to enable to feed satisfactorily it into the gasifier without any other problems at feeding systems. However, the Alaska coal was unable to maintain slurry concentration over the 60% due to its high viscosity. During the experiments, $O_2/coal$ ratios in both coals ere maintained from 0.6~1.2, but especially Alaska coal was required excessive oxygen feed due to its high ingerent moisture contents. During the experiments with two different coals, the concentrations of syngas $(H_2+CO)$ were shown as 40~62%, and the heating value of syngas were detected as 1,400~2,050 kcal/N㎥