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    Effects of operational parameters on emission performance and combustion efficiency in small-scale CFBCs
    (CHINESE INST CHEMICAL ENGINEER, 2008) Gungor, Afsin; Eskin, Nurdil
    A well-designed CFBC can burn coal with high efficiency and within acceptable levels of gaseous emission. In this theoretical study effects of operational parameters on combustion efficiency and the pollutants emitted have been estimated using a developed dynamic 2D (tow-dimensional) model for CFBCs. Model simulations have been carried out to examine the effect of different operational parameters such as excess air and gas inlet pressure and coal particle size on bed temperature, the overall CO, NO(x) and SO(2) emissions and combustion efficiency from a small-scale CFBC. It has been observed that increasing excess air ratio causes fluidized bed temperature decrease and CO emission increase. Coal particle size has more significant effect on CO emissions than the gas inlet pressure all the entrance to fluidized bed. Increasing excess air ratio leads to decreasing SO(2) and NO(x) emissions. The gas inlet pressure at the entrance to fluidized bed has a more significant effect on NO(x) emission than the coal particle size. Increasing excess air causes decreasing combustion efficiency. The gas inlet pressure has more pronounced effect on combustion efficiency than the coal particle size, particularly at higher excess air ratios. The developed model is also validated in terms of combustion efficiency with experimental literature data obtained from 300 kW laboratory scale test unit. The present theoretical study also confirms that CFB combustion allows clean and efficient combustion of coal. (C) 2008 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
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    Effects of operational parameters on the thermodynamic performance of FBCC steam power plant
    (ELSEVIER SCI LTD, 2009) Eskin, Nurdil; Gungor, Afsin; Ozdemir, Koray
    In this study, the effects of operational parameters on the thermodynamic performance of a FBCC steam power plant with a rated output of 7.7 MW are investigated by the developed model such as excess air, coal type and steam pressure based on the first and second laws of thermodynamics. The plant consists of a FBCC, a WHB and an economizer as subsystems and fans, pumps, cyclone and chimney as auxiliary systems. The model results are shown to agree well with plant operational data. As a result of this study. it is observed that the first and the second law efficiencies of the system decrease 5.1% and 5.2%, respectively, as the excess air increases from 10% to 70%. As the steam pressure increases from 4 to 12 bar, the energy efficiency of the system decreases to 2.1% but the exergy efficiency of the system increases to 19.9%. The amount of irreversibility occurring in the system is also calculated at each location through the developed model. The FBCC has the largest irreversibility, of about 80.4% of the total irreversibilities in the plant, mostly due to the irreversible combustion process. It is also observed that the coal type does not affect the first and the second law efficiencies considerably. (c) 2008 Elsevier Ltd. All rights reserved.
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    Thermodynamic analysis of a FBCC steam power plant
    (PERGAMON-ELSEVIER SCIENCE LTD, 2009) Eskin, Nurdil; Gungor, Afsin; Ozdemir, Koray
    This article presents the analysis of first and second laws of thermodynamics in a 7.7 MW steam power plant located in Torbali (Izmir, Turkey). it involves a fluidized bed, a waste heat boiler (WHB) and an economizer as subsystems. Fans, pumps, cyclone and chimney are also considered through the analysis as auxiliary systems in the thermal plant. The analysis is performed for the whole system and subsystems by considering the available energy balance. In this analysis which consists of a detailed fluidized bed coal combustor (FBCC) model, the amount of irreversibilities occurring in the system is calculated at each location. Analysis results are compared with the test results obtained from the measurements at several locations in the system and good agreement is observed. These measured values are the temperatures at three levels in the FBCC and boiler, economizer exit temperatures as well as flue gas composition at the boiler exit and steam flow rate. The maximum error observed in temperature values and steam flow rate is about 3.03% and 4.03%, respectively. Through the developed and validated model, effects of excess air and ambient temperature on first and second law efficiency of the subsystems and overall system are investigated. The second-law analysis reveals that the FBCC has the largest irreversibility, with about 80.4% of the total system exergy loss. The FBCC temperature, first and second law efficiencies decrease 19.8%, 5.1% and 5.2%, respectively, as the excess air increases from 10% to 70%. Also steam flow rate decreases 5.1%. As the ambient temperature increases from 25 to 45 degrees C, the FBCC temperature, system first and second law efficiencies increase 0.8%, 1.3%, and 1.3%, respectively. (C) 2009 Elsevier Ltd. All rights reserved.