中温余热热源有机朗肯循环工质比较

Comparison of Organic Rankine Cycle Working Fluids of Medium Temperature Waste Heat Source

结合算例,在建立平准化电力成本计算模型的基础上,考察7种工质(2-甲基丁烷、一氟二氯乙烷、丙酮、正庚烷、苯、辛烷、甲苯)亚临界循环、超临界循环热效率、平准化电力成本,考虑工质的环保及安全性,评价工质对中温余热热源有机朗肯循环的适用性。7种工质亚临界循环的热效率均随蒸发温度升高而增大,平准化电力成本均随蒸发温度升高而减小。7种工质超临界循环达到的最大热效率均高于亚临界循环,平准化电力成本均低于亚临界循环。膨胀机入口压力为5. 5 MPa条件下超临界循环综合性能优于入口压力6. 0 MPa。无论亚临界循环,还是超临界循环,苯、甲苯均在热效率和平准化电力成本方面表现出最佳的综合性能,一氟二氯乙烷的综合性能居中。苯、甲苯虽然毒性低,但可燃性较高,工程应用中存在较大风险,对管道、设备的密封提出更高要求。一氟二氯乙烷不仅环境友好,而且毒性低、不传播火焰,现阶段适合作为中温余热热源有机朗肯循环工质。

Based on the calculation model of Levelized Electricity Costs( LEC),the subcritical cycle,supercritical cycle thermal efficiency and LEC of 7 working fluids( 2-methylbutane,dichlorofluoroethane,acetone,n-heptane,benzene,octane and toluene) were investigated by the example,and the applicability of working fluids to organic Rankine cycle of medium temperature waste heat source was evaluated considering the environmental protection and safety of working fluids. The thermal efficiency of the subcritical cycle of the 7 working fluids increases with the increase of evaporation temperature,while the LEC decreases with the increase of evaporation temperature. The maximum thermal efficiency of supercritical cycle of 7 working fluids is higher than that of subcritical cycle,and the LEC is lower than that of subcritical cycle. The comprehensive performance of supercritical cycle is better than that of inlet pressure of 6. 0 MPa under the condition that the inlet pressure of the expander is 5. 5 MPa.Regardless of subcritical cycle or supercritical cycle,benzene and toluene show the best comprehensive performance in terms of thermal efficiency and LEC,and the comprehensive performance of dichlorofluoroethane is in the middle. Although the toxicity of benzene and toluene is low,but the flammability is high,there is a greater risk in the engineering application,which puts forward higher requirements for the sealing of pipes and equipment. Dichlorofluoroethane is not only environmentally friendly,but also has low toxicity and does not spread flame. At this stage,it is suitable as an organic Rankine cycle working fluid of medium temperature waste heat source.