• Title, Summary, Keyword: coal

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Current Status and Future Tasks of Clean Coal Technologies in the Asia Pacific Region

  • Son, Jae-Ek
    • Journal of Energy Engineering
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    • v.5 no.1
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    • pp.1-7
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    • 1996
  • Coal consumption in Asia is projected to increase by about 1.3 billion tons over the 1993-2010 period. The expansion in coal consumption for electricity generation is the dominant factor in the large increase in coal consumption. Without effective control measures, the projected increase in coal consumption will have a serious impact on environmental effects of increased coal use in Asia. Thus, the introduction of appropriate CCTs is considered essential to achieving the twin goals of expanded use of coal decreased environmental impacts.

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The Study on the Combustion and Ash Deposition Characteristics of Ash Free Coal and Residue Coal in a Drop Tube Furnace (DTF를 이용한 무회분 석탄과 잔탄의 연소 및 회 점착 특성에 관한 연구)

  • Moon, Byeung Ho;Kim, Jin Ho;Sh, Lkhagvadorj;Kim, Gyu Bo;Jeon, Chung Hwan
    • Journal of Energy Engineering
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    • v.24 no.4
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    • pp.89-96
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    • 2015
  • Recently, much research has been put into finding the causes and solutions of slagging/fouling problems that occur at the end of the boiler. This slagging/fouling, caused by low-rank coal's ash, disturbs the thermal power and greatly reduces efficiency. In environmental aspects, such as NOx pollution, governments have been implementing restrictions on the quantity of emission gases that can be released into the atmosphere. To solve these problems, research on Ash Free Coal (AFC), which eliminates ash from low-rank coal, is in progress. AFC has advantages over similar high-rank coals because it increases the heating value of the low grade coal, reduces the contaminants that are emitted, and decreases slagging/fouling problems. In this study, using a DTF, the changes of NOx emissions, unburned carbon, and the characteristics of ash deposition were identified. KCH raw coal, AFC extracted from KCH, residue coal, Glencore, and Mixed Coal (Glencore 85wt% and residue coal 15wt%) were studied. Results showed that AFC had a significantly lower emission of NOx compared to that of the raw coal and residue coal. Also, the residue coal showed a higher reactivity compared to raw coal. And finally, In the case of the residue coal and mixed coal, they showed a lower ash deposition than that of low-rank coal.

Numerical and experimental study for Datong coal gasification in entrained flow coal gasifier

  • Park, Y. C.;Park, T. J.;Kim, J. H.;Lee, J. G.
    • Proceedings of the Korea Society for Energy Engineering kosee Conference
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    • pp.69-76
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    • 2001
  • The coal gasification process of a slurry feed type, entrained-flow coal gasifier was numerically predicted in this paper. By divding the complicated coal gasification process into several simplified stages suh as slurry evaporation, coal devolitilisation and two-phase reactions coupled with turbulent flow and two-phase heat transfer, a comprehensive numerical model was constructed to simulate the coal gasification process. The k-$\varepsilon$turbulence model was used for the gas phase flow while the Random-trajectory model was applied to describe the behavior of the coal slurry particles. The unreacted-core shrinking model and modified Eddy Break-Up(EBU) model were used to simulate the heterogeneous and homogeneous reactions, respectively. The simulation results obtained the detailed informations about the flow field, temperature inside the gasifier. Meanwhile, the simulation results were compared with the experimental data as function of $O_2$/coal ratio. It illustrated that the calculated carbon conversions agreed with the measured ones and that the measurd quality of the atngas was better than the calculated one when the $O_2$/coal ratio increases. The result was related with the total heat loss through the gasifier and uncertain kinetics for the heterogeneous reactions.

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Cross-section micrography of burning pulverized coal particles (연소중 미분탄의 단면관측)

  • 한재현;최상민
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.13 no.4
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    • pp.717-725
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    • 1989
  • An experimental investigation on the combustion behavior of pulverized coal particles was performed using the cross-section micrography techniques while sample coal particles were collected in-situ from the flow reactor. The coal particles were representative of pulverized bituminous coal undergoing a raped pyrolysis and combustion, however, quenched at the time when the particles were deposited onto a sample plate. The internal structure of coal was observed to change as deposited. Upon injection into a flow reactor, bituminous coal particles showed many holes which represented internal pore formation during the pyrolysis. The relative portion of the remaining matrix of coal was decreasing as the residence time progressed. This direct observation of cross-section of burning particles enabled better understanding of the coal combustion behavior.

Thermogravimetric study for the co-combustion of coal and dried sewage sludge

  • Park, Jeong Min;Keel, Sangin;Yun, Jinhan;Yun, Ji Hye;Lee, Sang-Sup
    • The Korean Journal of Chemical Engineering
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    • v.34 no.8
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    • pp.2204-2210
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    • 2017
  • The co-combustion of dried sewage sludge with coal is a promising method to dispose of and treat sewage sludge waste. Because sewage sludge has a different elemental composition than coal, the co-combustion of sewage sludge with coal may have different combustion characteristics than the single combustion of coal. In this study, the co-combustion of dried sewage sludge with coal was tested varying heating rates and mixing ratios of the dried sewage sludge. The results were analyzed using thermogravimetric (TG) and derivative thermogravimetric (DTG) curves and modeled using Ozawa-Flynn-Wall and Vyazovkin models. The mixed samples of coal and dried sewage sludge showed similar TG curves to the coal sample. The co-combustion showed activation energies close to that of the single coal combustion. This suggests that the co-combustion of coal and dried sewage sludge has similar combustion behavior to the single combustion of coal for mixing percentages of dried sewage sludge up to 20%.

Reaction Characteristics of Coal and Oxygen Carrier Particle in a Thermogravimetric Analyzer (열중량분석기에서 석탄과 산소공여입자의 반응 특성)

  • Ryu, Ho-Jung;Kim, Young-Joo;Park, Yeong-Seong;Park, Moon-Hee
    • Transactions of the Korean hydrogen and new energy society
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    • v.22 no.2
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    • pp.213-222
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    • 2011
  • To check adaptability of low ash coal(hyper coal) to chemical looping combustion, reaction characteristics of two coals (Roto and Hyper coal) with two oxygen carriers (NiO/bentonite, OCN703-1100) have been investigated in a thermogravimetric analyzer. Hyper coal represented low combustion rate and high ignition temperature, high volatile content and high devolatilization rate, and therefore, showed worse oxygen transfer during successive 10 cycle reduction-oxidation test than Roto coal. Finally we selected Roto coal as the candidate coal for chemical looping combustion. For Roto coal, OCN703-1100 particle showed better oxygen transfer than NiO/bentonite particle. During 10 cycle reduction oxidation test, change of the extent of oxidation (Wo) was negligible and we could conclude that both oxygen carriers have sufficient regeneration ability.

Study on the Correlation between Thermal Characteristics and Heat Accumulation in the Coal Pile (석탄의 열적 특성과 석탄 내부의 승온 특성과의 상관관계 연구)

  • Lee, Hyun-Dong;Kim, Jae-Kwan
    • Journal of the Korean Society of Combustion
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    • v.15 no.4
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    • pp.58-64
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    • 2010
  • Spontaneous ignition tests of five different coals with non-iso-thermal and iso-thermal test method based on the standard test procedure of NF T20-036 were carried. These five coals included the 2 low rank coals and 3 bituminous coals. Test results showed that the ignition temperatures of all coals at the iso-thermal conditions were higher than that of non-isothermal condition, and those of low rank SM and BR coal in both nonisothermal and isothermal conditions were lower than bituminous AN and CN coals. The chemical species of coals such as oxygen and hematite also plays an important role in enhancing the ignition rate that the ignition temperature of SM coal was lowered. The heat accumulation tendency of five coals inside outdoor stack pile was monitored with emphasis on the change in the temperature of the coal depth in stack pile. In case of low rank BR coal, its temperature inside coal stack pile due to the rate of high heat accumulation and oxidation was $59^{\circ}C$ compared to $51^{\circ}C$ for other SW bituminous coal. And the heat accumulation rate inside coal stack piles was increased with increased the Cp value which it was defined as the specific heat of coal at constant pressure, whereas other factors such as thermal diffusivity and conductivity of coal relatively had less effect on heat accumulation.

Coal Gasification Performance with Key Operating Variables (주요 운전 변수에 따른 석탄의 가스화 성능 예측)

  • Lee, Seung-Jong;Chung, Seok-Woo;Yun, Yong-Seung
    • 한국신재생에너지학회:학술대회논문집
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    • pp.437-440
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    • 2007
  • Gasification converts coal and other feedstocks into a very clean and usable gas, called syngas, that can be used to produce a wide variety products such as electricity, chemicals, transports fuels, hydrogen production, etc. This paper was studied the gasification performance effects with the variation of the gasification operating parameters such as the feeding amounts of oxygen, steam and coal. When $O_2/coal$ ratio was below 0.8, $H_2$ mole % was increased as increasing $O_2/coal$ ratio. CO mole % was increased when $O_2/coal$ ratio was below 1.2 as increasing the $O_2/coal$ ratio. As increasing steam/coal ratio, $H_2$ mole %was increased and CO mole % was decreased. The $O_2/coal$ and steam/coal ratio was $0.8{\sim}0.9$ and $0.0{\sim}0.4$, respectively, to keep the proper gasification condition that the gasifier temperature was $1300^{\circ}C{\sim}1450^{\circ}C$ and the cold gas efficiency was over 76%.

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Spray Characteristics of a Coal Slurry with Liquid Carbon Dioxide (고압 저등급탄-이산화탄소 슬러리 분무특성에 관한 연구)

  • KIM, CHANGYEON;KIM, HAKDUCK;SONG, JUHUN
    • Transactions of the Korean hydrogen and new energy society
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    • v.26 no.4
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    • pp.357-362
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    • 2015
  • There is potential method to utilize the liquid carbon dioxide ($LCO_2$) in coal gasification plants. The $LCO_2$ could be used to effectively transport coal particles instead of conventional carrier such as liquid water ($H_2O$) particularly in wet-fed gasifier. However, there is a lack of fundamental study on the atomization behavior of $LCO_2$ coal slurry under high pressure condition. In this study, the flashing spray characteristics of a coal mixture with $LCO_2$ was examined during a throttling process by using a flow visualization system. The spray of coal water slurry which is in the Rayleigh-type break up mode was significantly different. This difference indicates that the coal water slurry did not effectively transport the coal, as compared to $LCO_2$ coal slurry.

Study on the propagation mechanism of stress wave in underground mining

  • Liu, Fei;Li, Lianghui
    • Computers and Concrete
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    • v.25 no.2
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    • pp.145-154
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    • 2020
  • For the influence of the propagation law of stress wave at the coal-rock interface during the pre-blasting of the top coal in top coal mining, the ANSYS-LS/DYNA fluid-solid coupling algorithm was used to numerical calculation and the life-death element method was used to simulate the propagation of explosion cracks. The equation of the crushing zone and the fracturing zone were derived. The results were calculated and showed that the crushing radius is 14.6 cm and the fracturing radius is 35.8 cm. With the increase of the angles between the borehole and the coal-rock interface, the vibration velocity of the coal particles and the rock particles at the interface decreases gradually, and the transmission coefficient of the stress wave from the coal mass into the rock mass decreases gradually. When the angle between the borehole and the coal-rock interface is 0°, the overall crushing degree is about 11% and up to the largest. With the increase of the distance from the charge to the coal-rock interface, the stress wave transmission coefficient and the crushing degree of the coal-rock are gradually decreased. At the distance of 50 cm, the crushing degree of the coal-rock reached the maximum of approximately 12.3%.