• Title, Summary, Keyword: coal

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Strength and durability characteristics of bricks made using coal bottom and coal fly ash

  • Ashish, Deepankar Kumar;Verma, Surender Kumar;Singh, Joginder;Sharma, Namesh
    • Advances in concrete construction
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    • v.6 no.4
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    • pp.407-422
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    • 2018
  • The study evaluates properties of brick having coal ash and explores the possibility of utilization of coal bottom ash and coal fly ash as an alternative raw material in the production of coal ash bricks. Lower cement content was used in the investigations to attain appropriate strength and prohibit high carbon content that is cause of environmental pollution. The samples use up to 7% of cement whereas sand was replaced with bottom ash. Bricks were tested for compressive strength, modulus of rupture, ultrasonic pulse velocity (UPV), water absorption and durability. The results showed mix proportions of bottom ash, fly ash and cement as 1:1:0.15 i.e., M-15 achieved optimum values. The coal ash bricks were well bonded with mortar and could be feasible alternative to conventional bricks thus can contribute towards sustainable development.

Influence of water content on dynamic mechanical properties of coal

  • Gu, Helong;Tao, Ming;Wang, Jingxiao;Jiang, Haibo;Li, Qiyue;Wang, Wen
    • Geomechanics and Engineering
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    • v.16 no.1
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    • pp.85-95
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    • 2018
  • Water affects the mechanical properties of coal and stress wave propagation. To comprehensively investigate the effect of water content on the properties of coal, laboratory tests including X-Ray Diffraction (XRD) analysis, P-wave test, S-wave test, static and dynamic compression test with different water contents were conducted. The compressive strength, elastic modulus and failure strain and their mechanism of coal specimen under coupled static-dynamic load with the increased water content were observed. Meanwhile, energy transmission and dissipation characteristics of a stress wave in coal specimens with different water contents under dynamic load and its relation with the failure features, such as fragmentation and fractal dimension, of coal was analyzed. Furthermore, the dynamic interpretation of water infusion to prevent coal burst based on water infusion model of coal seam roadway was provided.

Determination of Metals of Coal and Respirable Coal Dust in Gangneung and Taebaek Coal Mines (강릉·태백지역 석탄광산의 탄 및 호흡성 탄분진중 금속 농도 비교에 관한 연구)

  • Kim, Hae Jeong;Choi, Ho Chun;Chung, Ho Keun
    • Journal of Korean Society of Occupational and Environmental Hygiene
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    • v.1 no.1
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    • pp.82-88
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    • 1991
  • Determination of Cu, Fe, Ni, Pb, and Zn concentrations in coal and respirable coal dust were performed by atomic absorption spectrophotometry. The coal samples of 18 coal mines in Gangneung area were collected and 25 coal mines in Taebaek area. Crushed coal samples were divided into three mesh sizes. The results were as follows : 1. Metal concentrations of coals in Gangneung area by sieve sizes( -100/+200 mesh, -200/+325 mesh, -325 mesh) were as follows: Cu ; 20, 18, 19, Fe ; 1,830, 1,765, 1,107, Pb ; 6, 8, 14, Ni ; 17, 17, 14, Zn ; 4, 2, $4{\mu}g/g$, respectively. Metal concentrations in coals in Taebaek area by sieve sizes(-100/+200 mesh, -200/+325 mesh, -325 mesh) were as follows: Cu ; 30, 32, 26, Fe ; 1,741, 1,822, 1,773, Pb ; 8, 9, 7, Ni ; 13, 13, 13, Zn ; 8, 5, $4{\mu}g/g$, respectively. There were not significant differences of Cu, Fe, Ni, Pb, and Zn concentrations of coals statistically in Gangneung and Taebaek area by sieve size. 2. Metal concentrations of coals in Gangneung and Taeback area were as follows : Cu ; 19, 30, Fe ; 1,514, 1,778, Pb ; 9, 8, Ni ; 16, 13, Zn ; 3, $6{\mu}g/g$, respectively. Differences of copper and zinc concentrations of coal samples were significant between Gangneung and Taebaek area, but those of iron, nickel and lead concentrations were not significant. 3. Copper, iron, lead, nickel and zinc concentrations of coals and respirable coal dust were as follows : Cu ; 30, 6, Fe ; 1,779, 5,075, Pb ; 8, 7,814, Ni ; 13, 5,681, Zn ; 5, $134{\mu}g/g$, respectively. Differences of nickel, lead and zinc concentrations were significant between coals and respirable coal dust but those of copper and iron concentrations were not significant.

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Influence of Surrounding Gas and Coal Characteristics on Flame Propagation in Oxy-Fuel Combustion of Pulverized Coal (미분탄 순산소 연소에서 주위 기체와 석탄 특성이 화염전파에 미치는 영향)

  • Kang, Young-Min;Shim, Young-Sam;Moon, Cheor-Eon;Sung, Yon-Mo;Seo, Sang-Il;Kim, Tae-Hyung;Choi, Gyung-Min;Kim, Duck-Jool
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.33 no.1
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    • pp.38-45
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    • 2009
  • Oxy-fuel combustion of pulverized coal is one of the promising new technologies to reduce $CO_2$ and NOx from coal combustion. However, the stability of pulverized coal flame is reduced in the oxy-fuel combustion. This flame stability is concerned with the flame propagation that is affected by surrounding gas and coal characteristics, such as gas temperature, gas composition, coal volatile, coal activation energy and coal size. In this paper, a study on the influence of surrounding gas and coal characteristics on the flame propagation velocity in oxy-fuel combustion of pulverized coal was preformed. One dimensional model was used to calculate the flame propagation velocity of pulverized coal clouds. In this model, the radiation is considered to be the main source of heat exchange, and Monte Carlo method was adopted for accurate calculation of radiation heat flux. It was found that the flame propagation velocity become higher with the decrease of coal activation energy and the increase of coal volatile. Also, according to the increase of gas temperature and $O_2$ concentration, flame propagation velocity increased.

Comparison Study for Domestic Coal and Material Characteristics of Coal from the Shipwreck of Koryo Dynasty (고려시대 선체출토 석탄의 재료학적 특성 및 국산 석탄과의 비교 연구)

  • Lee, JangJon;Park, SukWhan;Lim, SungTae;Han, MinSu
    • Journal of Conservation Science
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    • v.29 no.4
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    • pp.345-354
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    • 2013
  • This study analyses geochemistrical, microscopic, mineralogical characteristics of coals which have been collected from in and out of the shipwreck No 1 of Mado island during underwater excavation in Taean. The result from mineralogical and geochemical analysis reveals that the specific gravity of the coals is $1.28g/cm^3$. Considering that coals contains 10% mineral of it and the specific gravity of the pure is $1.15g/cm^3$, it is believed that the collected coals would be lignite or biturminous coal. The X-ray diffraction analysis which displays the peak of $2{\theta}$ is 20~25C degree, proves that the collected coals would be categorised as low rank coal. The collected coals is composed of: 93%-94%(93.5%) of vitrinite maceral group, 5%-6%(5.5%) of exinite maceral group, and 1% of inertinite maceral group. In addition, the average of reflection rate is $R_{mean}$: 0.627 showing that it would be either high volatile bituminous C coal or sub-bituminous C coal. Such result confirms that the coal is sub-bituminous C or high volatile bituminous C coal in accordance with the U.S Bureau of Mine(USBM) classification system. The element analysis reveals that the coal is the coking coal which is grouped as the bituminous coal. Comparative analysis between the coals of Mado Shipwreck No 1 and domestic coals shows that the coals of Mado Shipwreck is similar to the bituminous coal used in the area of Janggi in Pohang city.

Investigation of Tar/soot Yield of Bituminous and Low Rank Coal Blends (발전용 역청탄과 저열량탄 혼소시 Tar/Soot의 배출 특성 연구)

  • Lee, Byung Hwa;Kim, Jin Ho;Kim, Gyu Bo;Kim, Seng Mo;Jeon, Chung Hwan
    • Journal of Energy Engineering
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    • v.23 no.2
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    • pp.42-48
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    • 2014
  • Soot and tar which were derived from combustion or pyrolysis processes in Puverized Coal(PC) furnace or boiler have been significantly dealing in a radiative heat transfer and an additional source of NOx. Furthermore, the increasing for the use of a coal with low caloric value gives rise to a lot of tar-soot yield and LOI in a recycled ash for using cement materials. So, the ash with higher tar-soot yield and LOI can not recycle due to decreased strength of concrete. In this study, tar-soot yields and flame structures were investigated using the LFR for a blending combustion with bituminous coal and sub-bituminous coal. Also, The investigation were conducted as each single coals and blending ratio. The coals are used in a doestic power plant. In the experimental results, sub-bituminous coal with high volatile contents shows longer soot cloud length than bituminous coal, but overall flame length was shorter than bituminous coal. Tar-soot yields of sub-bituminous coal is lower than those of bituminous coal. Combustion characteristics are different between single coal and blended coal. Therefore, finding an optimal coal blending ratio according to coal rank effects on tar-soot yields.

Evaluation of Static and Dynamic Characteristics of Coal Ashes (석탄회의 정적 및 동적 특성 평가)

  • Yoon, Yeowon;Chae, Kwangsuk;Song, Kyuhwan
    • Journal of the Korean Geoenvironmental Society
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    • v.10 no.3
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    • pp.5-12
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    • 2009
  • This study presents static and dynamic strength of coal ashes collected from disposal site of power plant. Main compositions of coal ashes were bottom ashes. In order to evaluate static and dynamic characteristics of coal ash, NGI direct-simple shear tests, cyclic simple shear tests and direct shear tests were conducted. The strengths of coal ashes from those tests were compared to those of sands. Bottom ashes among coal ashes used for this study were classified as sand from the grain size distribution and show higher strength properties than the sands. For utilization of coal ashes in civil engineering project, mixing coal ashes with sandy soil using batch plant is inconvenient and the cost is higher than the spreading sand layer and coal layer alternately. In order to simulate both mixing type and layered type construction, sands and coal ashes were mixed with volume ratio 50:50 and prepared sand and coal ash layers alternately with the same volume ratio. From the tests mixed coal ashes-specimen shows slightly higher static and cyclic strength than the layered specimen at the same density. The higher strength seems due to the angular grain of bottom ashes. The cyclic stress ratio at liquefaction decreases rapidly as the number of cycle increases at mixed specimen than that of layered specimen.

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CFD Modeling for 300MW Shell-Type One-Stage Entrained Flow Coal Gasifier : Effect of $O_2$/Steam/Coal Ratios, Coal Particle Sizes, and Inlet Angles on the Gasifier Performance (300MW급 Shell형 1단 분류층 석탄 가스화기의 전산수치해석 : 산소/스팀/석탄 주입비, 석탄입자 크기, 주입 노즐 각도가 가스화기 성능에 미치는 영향)

  • Song, Ji-Hoon;Kang, Min-Woong;Seo, Dong-Kyun;Lim, Sung-Jin;Paek, Min-Su;Hwang, Jung-Ho
    • Transactions of the Korean hydrogen and new energy society
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    • v.21 no.3
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    • pp.227-240
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    • 2010
  • Coal gasification is heading for a great future as one of the cleanest energy sources, which can produce not only electricity and heat, but also gaseous and liquid fuels from the synthesis. The work focuses on 300MW shell type one-stage entrained flow coal gasifier which is used in the Integrated coal Gasification Combined Cycle(IGCC) plant as a reactor. As constructing an IGCC plant is considerably complicated and expensive compared with a pulverized-coal power plant, it is important to determine optimum design factors and operating conditions using a computational fluid dynamics (CFD) model. In this study, the results of numerical calculations show that $O_2$/Coal ratio, 0.83, Steam/Coal ratio, 0.05, coal particle diameter, $100{\mu}m$, injection angle, $4^{\circ}$ (clockwise) are the most optimum in this research.

Circulating Fluidized Bed Combustion of Korean Anthracite and Fabricated Anthracite Fines (국내 무연탄과 미분을 성형한 무연탄의 순환유동층 연소)

  • Shun, Do-Won;Bae, Dal-Hee;Oh, Chang-Sup;Kim, Heon-Chang
    • Applied Chemistry for Engineering
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    • v.21 no.5
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    • pp.553-558
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    • 2010
  • To solve the problems of the low combustion activity of Korean anthracite and the abundant loss of unburned carbon in fly ash, pellet coal was fabricated from coal fines and fly ash, and the mixed combustion of coarse coal with the pellet coal was examined in the circulating fluidized bed combustor of a 0.1 MW scale test unit. In the combustion of the raw coal only, the significant amount of coal fines was entrained, resulting in overheat at the top of the combustor. With the coarse coal that most fines were eliminated, however, the combustion temperature was maintained stable. The mixed combustion of coarse and raw coals was also feasible even though it often went unstable. The mixed combustion of the coarse coal with the pellet coal was as stable as the coarse coal combustion, showing a promise that the combustion of the Korean anthracite in commercial circulating fluidized bed boilers could be further enhanced.

Measurement and Analysis of Coal Conversion Efficiency for a Coal Recirculating Fuel Cell Simulator (석탄순환형 연료전지 모사시스템용 석탄전환율 측정 및 분석법개발에 관한 연구)

  • Lee, Sangcho;Kim, Chihwan;Hwang, Munkyeong;kim, Minseong;Kim, Kyubo;Jeon, Chunghwan;Song, Juhun
    • Transactions of the Korean hydrogen and new energy society
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    • v.23 no.5
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    • pp.503-512
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    • 2012
  • There is a new power generation system such as direct coal fuel cell (DCFC) with a solid oxide electrolyte operated at relatively high temperature. In the system, it is of great importance to feed coal continuously into anodic electrode surface for its better contact, otherwise it would reduce electrochemical conversion of coal. For that purpose, it is required to improve the electrochemical conversion efficiency by using either rigorous mixing condition such as fluidized bed condition or just by recirculating coal particle itself successively into the reaction zone of the system. In this preliminary study, we followed the second approach to investigate how significantly particle recycle would affect the coal conversion efficiency. As a first phase, coal conversion was analyzed and evaluated from the thermochemical reaction of carbon with air under particle recirculating condition. The coal conversion efficiency was obtained from raw data measured by two different techniques. Effects of temperature and fuel properties on the coal conversion are specifically examined from the thermochemical reaction.