• 한국연소학회:학술대회논문집
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• 2013.06a
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• pp.25-28
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• 2013

This study presents both experimental and numerical investigation of ignition characteristics of n-heptane and n-butanol mixture. The $O_2$ concentration was fixed to 9-10% to make high exhaust gas recirculation(EGR) rate condition. Experiments were performed using a rapid compression machine. In addition, a numerical study of the ignition delay time was performed using CHEMKIN codes to validate experimental results and predict chemical species after combustion process. The results showed that the ignition delay time increased with increasing n-butanol ratio and the reactivity decreased by low $O_2$ concentration.

• 한국연소학회:학술대회논문집
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• 2013.06a
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• pp.83-85
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• 2013

With an increase in the use of low rank coals in power plants, various operational issues were raised in the fuel storage and supply, combustion, boiler and flue gas treatment systems. In the fuel storage and supply system, the main issue is the self-heating propensity of low rank coals leading to spontaneous combustion in yard storage, transport and pulverization. This study evaluated the reactivity of various sub-bituminous and bituminous coals with oxygen at low temperatures by analyzing the temperature increase characteristics of coals under a constant flow rate of oxygen supply. The results were quantified to a self-heating index and the relation with the fuel properties were evaluated.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.4
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• pp.400-412
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• 2022

Hydrogen with high chemical reactivity and combustion efficiency, is expected to reduce greenhouse gas and CO emission. However, there is a problem of increase in NOx emission due to hydrogen combustion. MILD combustion technology has been proposed to resolve NOx emission. In this study, the characteristics of MILD combustion and NOx formation by flue gas recirculation (KV) in CH₄-H₂ mixture were analyzed and predicted using 0D premixed combustion model. The ignition delay time became shorter as the hydrogen co-firing rate increased, and longer as the recirculation rate increased. For NOx emission, EINO decreased as the KV increased, but EINO increased as the hydrogen co- firing rate increased. In particular, EINO was predicted to increase significiently above 80% hydrogen. Through the pathway analysis of NO formation, it was found that the influence of N₂O intermediate route and NNH route was enhanced for hydrogen co-firing.

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.843-849
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• 2012

When we use NiO based particle as an oxygen carrier in a chemical looping combustion system, the fuel conversion and the $CO_2$ selectivity decreased with increasing reaction temperature within high temperature range (> $900^{\circ}C$) due to the increment of exhaust CO concentration from reduction reactor. To improve reduction reactivity at high temperature, the applicable metal oxide component was selected by calculation of the equilibrium CO concentration of metal oxide components. After that, feasibility of reduction reactivity improvement at high temperature was checked by using solid mixture of the selected metal oxide particle and NiO based oxygen carrier. The reactivity was measured and investigated using batch type fluidized bed. The solid mixture of $Co_3O_4/CoAl_2O_4$(10%) and OCN706-1100(90%) showed higher fuel conversion, higher $CO_2$ selectivity and lower CO concentration than OCN706-1100(100%) cases. Consequently, we could conclude that improvement of reduction reactivity at high temperature range by adding some $Co_3O_4$ based oxygen carrier was feasible.

• Journal of ILASS-Korea
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• v.21 no.1
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• pp.29-36
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• 2016

The effect of high ambient temperature and pressure conditions on the combustion performance of n-butanol, n-heptane and its mixing fuel (BH 20) were studied in this work. To reveal this, the closed homogeneous reactor model applied and 1000-1200 K of the initial temperature, 20-30 atm of initial pressure and 1.0 of equivalence ratio were set to numerical analysis. It was found that the results of combustion temperature was increased and the ignition delay was decreased when the ambient conditions were elevated since the combustion reactivity increased at the high ambient conditions. On the contrary, under the low combustion temperature condition, the combustion pressure was more influenced by the ambient temperature in the same ambient conditions. In addition, the total mass and the mass density of tested fuels were influenced by the ambient pressure and temperature. Also, soot generation of mixing fuel was decreased than n-heptane fuel due to the oxygen content of n-butanol fuel.

• Journal of Energy Engineering
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• v.14 no.1
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• pp.1-10
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• 2005

The combustion reactivity of char depending on the pyrolysis pressure was investigated with Pressurized Thermogravimetric Analyser. The amounts of volatiles released at pyrolysis pressure of 1, 8 and 15 atm were, first, measured with Alaska, Adaro and Denisovsky coals. Reactivities of chars produced at var-ious pyrolysis pressure were evaluated at atmospheric pressure and 500℃, and analysed in terms of char crystal structure, surface area, pore characteristics and chemical composition of char. Finally, the combustion reactivities of three chars were examined at pressure of 1 atm, 8 atm and 15 atm. From this study, it was recognized that the amount of volatiles released decreases with increase in pyrolysis pressure, and reaction rate of char produced at higher pyrolysis pressure was lower than that at lower pyrolysis pressure. It might be resulted from the difference in char surface area and pore characteristics rather than char crystal structure and chemical characteristics. At 15 atm, kinetic parameters of Alaska char were obtained with the grain model, and these were 56.8 KJ/mole for activation energy and 222.34 (1/min) for frequency factor.

• Journal of the Korean Society of Combustion
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• v.21 no.4
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• pp.23-29
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• 2016

Reactivity of gasification defined by bouardard reaction is critical parameter in efficiency of the gasifier. In this study, char reactivity of the gasification was derived from the experiments using the intrinsic reaction kinetics model. Pressurized wire mesh heating reactor (PWMR) can produce high temperature and high pressure conditions up to 50 atm and 1750 K, respectively and PWMR was designed to evaluate the intrinsic reaction kinetics of $CO_2$ gasification. In this study, Kideco and KCH (sub-bituminous Indonesian coal) were pulverized and converted into char. Experiments used the PWMR were conducted and the conditions of the temperature and pressure were 1373~1673 K, 1~40 atm. To distinguish the pressure effect from high pressurized condition, internal and external effectiveness factors were considered. Finally, the intrinsic kinetics of the Kideco and KCH coal char were derived from $n^{th}$ order reaction rate equations.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.5
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• pp.581-588
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• 2016

To compare reduction reactivity of oxygen carrier particles, $CH_4$ combustion characteristics were measured and investigated in a bubbling fluidized bed reactor with increasing $CH_4$ concentration from 10 to 100 %. Among five oxygen carriers (OC-1, OC-2, SDN70, C14, C28), OC-1, OC-2, SDN70 particles were selected as better oxygen carriers from the viewpoints of fuel conversion and $CO_2$ selectivity. However, some oxygen carriers showed lower fuel conversion and $CO_2$ selectivity even though they have high oxygen transfer capacity. Therefore, we could conclude that not only TGA tests to measure the oxygen transfer capacity but also fluidized bed tests to analyze exhaust gas concentration should be performed to select better oxygen carrier without misunderstanding of carriers reactivity.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.47-49
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• 2014

발전소에서 설계 규격을 벗어나는 저등급 석탄을 사용하기 시작하면서, 보일러에서의 연소특성을 예측하기 어려운 다양한 성질의 석탄이 들어오게 되어 각종 연소 문제가 증가하고 있다. 이 중 약 점결 특성을 가지는 저등급 석탄의 사용은 대형 클링커로 인한 보일러 하부의 튜브 손상 사고, 재열증기온도 상승으로 인한 출력감발 등의 문제를 발생시켰다. 또한 현재 개발 중인 무회분석탄 역시 점결 특성을 가지고 있는 것으로 알려져 있어 보일러 내부의 다양한 문제를 일으킬 것으로 예상되고 있다. 발전소에서는 강점결탄 수입 규제를 위해 CSN(Crucible Swelling Number)를 이용하여 제철용으로 사용되는 강점결 석탄의 도입을 규제해왔으나, 발전소 운영에 악 영향을 미치는 약 점결탄에 대한 규제 및 대응으로는 그 효과가 미미한 실정이다. 따라서 본 연구에서는 석탄의 점결 특성 중 팽창 특성을 분석할 수 있는 Microdilatometer와 TGA를 이용한 연소반응성 분석을 통해 석탄의 점결 특성이 연소반응성에 미치는 영향을 분석하였다.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.1
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• pp.95-105
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• 2016

Spray-dried NiO-based oxygen carriers developed for chemical looping combustion required high calcination temperatures above $1300^{\circ}C$ to obtain high mechanical strength applicable to circulating fluidized-bed process. In this study, the effect of CBB ($CaO{\cdot}BaO{\cdot}B_2O_3$) addition, as a binder, on the physical properties and oxygen transfer reactivity of spray-dried NiO-based oxygen carriers was investigated. CBB addition resulted in several positive effects such as reduction of calcination temperature and increase in oxygen transfer capacity and porosity. However, oxygen transfer rate was considerably decreased. This was more apparent when a higher amount of CBB was added and MgO was added together. From the experimental results, it is concluded that CBB added NiO-based oxygen carriers are not suitable for chemical looping combustion and a new method to reduce calcination temperature while maintaining high oxygen transfer rate of NiO-based oxygen carriers should be found out.