Thermo-Economic Analysis on Waste Heat and Water Recovery Systems of Boiler Exhaust in Coal-Fired Power Plants

Kaixuan Yang, Ming Liu, Junjie Yan
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Abstract

Waste heat and water recovery from boiler exhaust fluegas is significant for reducing coal and water consumption of coal-fired power plants. In this study, waste heat and water recovery system No.1 (WHWR1) and No.2 (WHWR2) were proposed with a 330MW air-cooling coal-fired power plant as the reference power plant. In these systems, boiler exhaust fluegas is cooled to 95 °C in fluegas coolers before being fed to the electrostatic precipitator. Moreover, a fluegas condenser is installed after the desulfurizer to recover water from fluegas. The recovered waste heat is used to heat the condensation water of the regenerative system, boiler feeding air and the fluegas after fluegas condenser. Then, thermodynamic and economic analyses were carried out. Heat exchangers’ areas of WHWRs are affected by heat loads and heat transfer temperature differences. For the unit area cost of heat exchangers is different, the cost of WHWRs may be decreased by optimizing multiple thermodynamic parameters of WHWR. Therefore, the optimization models based on Genetic Algorithm were developed to obtain the optimal system parameters with best economic performance. Results show that the change in coal consumption rate (Δb) is ∼ 4.8 g kW−1 h−1 in WHWR2 and ∼ 2.9 g kW−1 h−1 in WHWR1. About 15.3 kg s−1 of water can be saved and recovered when the fluegas moisture content is reduced to 8.5%. The investment of WHWR2 is higher than WHWR1, while the static recovery period of WHWR2 is shorter than that of WHWR1 for the additional Δb of pre air pre-heater.
燃煤电厂锅炉排烟余热及水回收系统的热经济性分析
锅炉废气余热和水的回收利用对降低燃煤电厂的煤和水消耗具有重要意义。本研究以330MW空冷燃煤电厂为参考电厂,提出了余热水回收系统1号(WHWR1)和2号(WHWR2)。在这些系统中,锅炉排出的烟气在进入静电除尘器之前在烟气冷却器中冷却到95°C。此外,在脱硫器后还安装了烟气冷凝器,以回收烟气中的水。回收的余热用于加热蓄热系统冷凝水、锅炉进气和烟气冷凝器后的烟气。然后进行了热力学和经济分析。水冷堆换热器面积受热负荷和换热温差的影响。由于换热器单位面积成本不同,可以通过优化水暖堆的多个热力参数来降低水暖堆的成本。为此,建立了基于遗传算法的优化模型,以获得具有最佳经济性能的最优系统参数。结果表明,在WHWR2和WHWR1中,煤炭消耗率(Δb)的变化分别为~ 4.8 g kW−1 h−1和~ 2.9 g kW−1 h−1。当烟气含水率降至8.5%时,可节约和回收约15.3 kg s−1的水。WHWR2的投资高于WHWR1,但由于增加了Δb空气预热器,WHWR2的静态回收期比WHWR1短。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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