• Title, Summary, Keyword: fluidized bed combustor

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Heat Transfer Characteristics of a Horizontal Fin Tube in a Fluidized Bed Combustor (유동층 연소로 내에서 수평전열관의 열전달 특성에 관한 연구)

  • 맹민재;정준기;정태용
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.9
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    • pp.2365-2372
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    • 1995
  • The objective of this study is to get the basic data for the development of fluidized bed combustor. For this purpose, various rake angles(.theta.=20.deg., 25.deg., 30.deg., 35.deg.) of finned tubes and a smooth tube were installed horizontally in the fluidized bed combustor of 410*250mm. The effect of fluidized bed temperature, superficial velocity in bed, size of bed materials, rake angle of finned tubes on the heat transfer coefficient was experimentally investigated. The following results were obtained. (1) Under the fluidized bed temperature(750.deg. C-900.deg. C), and the gas velocity in bed(1.1-2.8m/sec), The highest heat transfer coefficient was measured with the rake angle of finned tubes was .theta.=25.deg. and .theta.=35.deg. for the average fluidized material particle size of 1.22mm and 1.54mm, respectively. Generally, the heat transfer coefficient of finned tubes is 1.4 to 2.4 times larger than that of smooth tubes. (2) The size of bed materials influences the rake angle of finned tubes which can have the highest heat transfer coefficient. As the temperature in bed gets higher, the effect of the rake angle of finned tubes on the heat transfer coefficient becomes greater.

Analysis of Combustion Characteristics of Bituminous and Anthracite Coal in a Fluidized Bed Combustor (유동층연소로에서 유연탄과 무연탄의 연소특성 해석)

  • Jang, Hyun Tae;Park, Tae Sung;Hong, Sung Chang
    • Applied Chemistry for Engineering
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    • v.10 no.4
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    • pp.586-591
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    • 1999
  • Mixed-firing of a bituminous and an anthracite coal carried out in a batch fluidized bed combustor(0.109 m-I.D., 0.9 m-height). Effect of particle size an mixing fraction of anthracite and bituminous coal combustion characteristics were studied. The temperature profiles and pressure fluctuation properties were measured to interpret the combustion characteristics in a batch fluidized bed combustor. The used domestic anthracite coal has heating value of 2010 kcal/kg and the imported high-calorific bituminous coal has heating value of 6520 kcal/kg. The combustion characteristics in a batch fluidized bed combustor could be interpreted by using pressure fluctuation properties and temperature increasing rates. It was found that the optimum anthracite mixing percentage could be predicted analyzing the combustion rate and fluidization characteristics, The optimum mixing fraction was about 30 %. The different burning region of fluidized bed combustor was measured by temperature increasing rates.

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Solid fuel combustion in a fluidized bed - Characteristics of a lab-scale combustor and experimental parameters (고체 연료의 유동층 연소 - 시험 연소로 특성 및 실험 인자 설정)

  • Choi, Jin-Hwan;Park, Young-Ho;Choi, Sang-Min
    • 한국연소학회:학술대회논문집
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    • pp.236-245
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    • 2000
  • A laboratory scale fluidized bed reactor was developed to treat the combustion characteristics of some fuels (wood, paper sludge, refuse derived fuel). The aims were to introduce the means of experiment and interpretation of the results and finally determine the particle characteristics on the pyrolysis and combustion process of the fuel. A single particle combustion process in the fluidized bed was closely observed. Understanding experimental facility characteristics and determining parameters were also carried out. The fuel combustion processes were observed by carbon conversion rate, recovery and mean carbon conversion time. They were estimated with the CO, $CO_2$ gas concentration monitored at the exit of the combustor. Fuel drying and pyrolysis process were governed by temperature distribution in the fuel particle. There was a significant overlap of the drying and devolatilization. However, transition process from devolatilization to char combustion seemed to be determined by mechanical solidity of the fuel particle after devolatilization process.

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A Study on Combustion & Flue Gas Characteristics of Coal at Pressurized Fluidized Bed Combustor (가압유동층연소로에서 석탄의 연소 및 배가스특성 연구)

  • Han, Keun-Hee;Oh, Dong-Jin;Ryu, Jung-In;Jin, Gyoung-Tae
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.5
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    • pp.677-686
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    • 2000
  • The characteristics of combustion and of emissions in pressurized fluidized bed combustor are investigated. The pressure of the combustor is fixed at 6 atm, and the combustion temperatures are set to 850, 900, and $950^{\circ}C$. The gas velocities are 0.9, 1.1, and 1.3 m/s. The excess air ratio is varied from 5 to 35%. The coal used in the experiment is Shenhwa coal in China. All experiments are executed at 2m bed height. Consequently, NOx & $N_2O$ concentration in the flue gas is increased with incresing excess air ratio but $SO_2$ concentration is decreased with incresing excess air ratio. CO concentration is maintained below 100ppm at over 15% of excess air ratio.

The Effects of Desulfurization by Screen using Ca-based Absorbent in a Solid Waste Fluidized-bed Combustor (유동층연소로에서 제지공장 폐기물을 이용한 황산화물 제어시 스크린에 의한 탈황효과)

  • 조상원;이재홍;조기철;장상용;오광중
    • Journal of Environmental Science International
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    • v.7 no.6
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    • pp.783-791
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    • 1998
  • The objectives of this study were to investigate the characteristics of desulfurization under different experimental conditions and the effects of desulfurization bed fluidized bed combuster installed with the screen. The experimental results were as follows ; First, as the height of fluidized bed combustor becomes higher, the concentrations of $SO_2$ mainly increased and sulfur retion of paper sludge was higher than that of natural limestone. Second, the desulfurzation by natural limestone occurred at in-bed and the desulfurization by paper sludge occurred in the whole of fluidized bed combuster. In addition, we identified calcium sulfate by the analysis of SEM and XRD. Third, screen at splash region increased sulfur retention 2~5%, air velocity and anthracite fraction had a little effect on the sulfur retention.

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A Study on Contaminant Emission and Combustion of Anthracite-Bituminous Coal Blend in a Fluidized Bed Coal Combustor (유동층 연소로에서 유$cdot$무연탄 혼합 연소시 대기오염물질 배출에 관한 연구)

  • 조상원;정종현;손병현;김영식;오광중
    • Journal of Environmental Health Sciences
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    • v.22 no.3
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    • pp.28-36
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    • 1996
  • The objects of this study were to investigate emissions of air pollutant the particles as well as the combustibility of the low grade domestic anthracite coal and imported high-calorific bituminous coal in the fluidized bed coal combustor. The production of air pollution from anthracite-bituminous coal blend combustion in a fluidized bed coal combustor was evaluated. The effects of air velocity and anthracite fraction on the reaching time of steady state condition was also evaluated. We used coal samples the domestic low grade anthracite coal with heating value of 2,010 kcal/kg and the imported high grade bituminous coal with heating value of 6,520 kcal/kg. The experimental results are presented as follows. The time of reaching to steady state was affected by the temperature variation. The steady state time was about 120 minute at 0.3 m/s which was the fastest. It has been found that $O_2$ and $CO_2$ concentration were reached steady state at about 100 minute. As the height of fluidized bed becomes higher, the concentration s of $SO_2$ and $NO_x$ mainly increased. The concentration of freeboard was the highest and emission concentration was diminished. Also, as anthracite fraction increased, the emission of $SO_x$ concentration was increased. But, it has been found that the variation of $NO_x$ concentration with anthracite fraction was negligible and the difference of emission concentration according to air flow rates was negligible, too. It has been found that $O_2$ concentration decreased and $CO_2$ concentration increased as the height of fluidized bed increased. As anthracite fraction increased, the mass of elutriation particles increased, and $CO_2$ concentration decreased. Also, as air velocity increased, $O_2$ concentration decreased and $CO_2$ concentration increased. Regardless-of anthracite fraction and flow rate, the combustible weight percentage in elutriation particles were high in the case of fine particles.

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A Numerical Study on the Effect of Coefficient of Restitution to Heat Transfer in a Conical Fluidized Bed Combustor (원추형 유동층 연소기 내의 열전달에 미치는 복원계수의 영향에 대한 수치해석 연구)

  • Kang, Seung Mo;Park, Woe-Chul;Abdelmotalib, Hamada;Ko, Dong Kuk;Im, Ik-Tae
    • Journal of the Semiconductor & Display Technology
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    • v.14 no.4
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    • pp.38-44
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    • 2015
  • In this paper, numerical simulations on conical fluidized bed combustors were carried out to estimate the effect of coefficients of restitution between particle and particle and particle to wall on hydrodynamics and heat transfer. The Eulerian-Eulerian two-fluid model was used to simulate the hydrodynamics and heat transfer in a conical fluidized bed combustor. The solid phase properties were calculated by applying the kinetic theory of granular flow. Simulations results show that increasing the restitution coefficient between the particle and particle results in increasing the bed pressure drop. On other hand, the increasing of particle to wall coefficient of restitution results in decreasing the bed pressure drop. It is found that the coefficient of restitution has little effect on heat transfer.

Effect of Secondary Air Injection on CO and NOx Emission in an Internally Circulating Fluidized Bed Combustor (이중 순환식 유동층 연소로내에서 2차 공기 주입에 의한 CO, NOx 저감효과)

  • Jang, S.D.;Shin, D.H.;Hwang, J.H.
    • 한국연소학회:학술대회논문집
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    • pp.204-211
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    • 2002
  • Combustion experiments are carried out to obtain the fundamental data for application of a internally circulating fluidized bed combustor to the combustion of paper sludge wastes. Experimental parameters are identified as secondary air ratio, sludge weight and water contents. The secondary air ratio was varied from 0 to 20% and water content was 14%, 25%, 35%, 45%, 62% and sludge weight was 30g, 60g, 90g. As a result, carbon conversion ratio was higher than injection of primary air. Emission of CO and NOx reduced with an increase of secondary air injection.

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Effect of Excess Air and Superficial Air Velocity on Operation Characteristics in a Fluidized Bed Coal Combustor (공탑속도 및 과잉공기비에 따른 석탄유동층연소로의 조업특성)

  • 장현태;차왕석;태범석
    • Journal of the Korean Society of Safety
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    • v.14 no.3
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    • pp.84-92
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    • 1999
  • The effects of air velocity and excess air on combustion characteristics were studied in a fluidized bed combustor. The domestic low-grade anthracite coal with heating value of 2010 kcal/kg and the imported bituminous coal from Australia with heating value of 6520 kcal/kg were used as coal samples. The combustion characteristics of mixed fuels in a fluidized bed combustor could be interpreted by pressure fluctuation properties, ash distribution and gas emission. The properties of the pressure fluctuations, such as the standard deviation, cross-correlation function, dominant frequency and the power spectral density function, were obtained from the statistical analysis. From this study, the combustion region increased with increasing air velocity but decreased with excess air due to combustion characteristics of anthracite and bituminous coal.

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Analysis on the fuel concentration distribution in a fluidized bed for the scale-up of a FBC (유동층 연소로의 스케일-업을 위한 유동층 내 연료농도분포 해석)

  • Lee, Dong-U;Park, Seung-Ho
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.6
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    • pp.747-757
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    • 1997
  • A numerical investigation of the fuel concentration field in a fluidized bed has been carried out for the scale-up of a fluidized bed combustor (FBC). A two-dimensional transient model is developed using the two-phase fluidization, a simple chemical reaction, and lateral solid mixing theories. The uniformity of fuel concentration distributions is controlled by the location and the number of fuel feeders, fluidizing velocities and the bed-heights. While larger bubbles owing to greater fluidizing velocities enhance the fuel-dispersion in the bed, they have adverse effects on fuel combustion and thus result in the increase of fuel concentration, since a greater bubble means a larger bypass which reduces gas-exchange rates between bubble and emulsion phases. Average or maximum values of the bed fuel concentration are utilized as criteria for the scale-up from a pilot/lab-scale to a commercial-size bed.