中温烟气余热动力回收CO_2超临界回热循环优化  

Optimization of CO_2 regenerative super-critical cycle for waste heat from exhaust gases at moderate temperature

作　　者：朱晓杰[1] 王怀信[1] 孙宏科[1] 

机构地区：[1]天津大学机械工程学院,天津300072

出　　处：《化学工程》2014年第4期13-17,共5页Chemical Engineering(China)

基　　金：高等学校博士学科点专项科研基金资助项目(20110032110046)

摘　　要：考虑烟气的放热特性、一般冷源条件、中高温工况对工质热稳定性的要求和工质的环境特性,提出以CO2超临界循环(CO2-SC)作为初温300—500℃的烟气余热动力回收基础循环;针对CO2-SC吸热过程工质初温低、有限循环压比下膨胀过程终温过高的问题,对CO2-SC引入回热过程得到了CO2回热超临界循环(CO2-RSC)。对CO2-SC和CO2-RSC开展了以单位质量烟气的循环净输出功(比净功)最大为目标函数,以膨胀过程初温、初压、终压和回热度(对CO2-RSC)为优化变量的优化对比研究,结果表明:回热过程的引入,有效改进了循环效率,使循环比净功明显提高;在指定的换热器传热窄点温差和系统部件效率值下,烟气初温分别为300,400,500℃时,CO2-RSC的比净功较CO2-SC高50.9%,52.7%,49.6%。回热还使得CO2-RSC工质吸热过程初温高于烟气的酸露点,避免了超临界加热器烟气侧低温腐蚀问题。CO2 super-critical cycle （CO2-SC） was suggested as the basic power cycle for waste heat from exhaust gases of initial temperature of 300-500 ℃, considering the heat releasing character of the exhaust gas as the waste heat source, general temperature levels of heat sinks, requirements to the thermal stability of the working fluid for moderate/high temperature operating conditions, as well as the environmental characters of the working fluid. The regenerative process was adopted, resulting in the CO2 regenerative super-critical cycle （CO2-RSC）, to improve the thermal efficiency by increasing the average heat addition temperature and decreasing the average heat releasing temperature of the cycle. The optimization on the initial temperature, initial pressure, final pressure of the expansion process （for both C02-SC and C02-RSC） and the regeneration degree （for CO2-RSC ） was carried out aimed at the maximum network of each cycle. The results show that the great improvements on thermal efficiency and network are obtained by the introduction of regenerative process. Under specified heat transfer pinch point temperature differences and components＇ efficiencies, the maximum network of C02-RSC are 50.9%, 52.7%, and 49.6% higher than that of CO2-SC, when the initial temperatures of the exhaust gas are 300, 400, and 500℃respectively. No low-temperature erosion would happen to the CO2-RSC system, since the initial temperature of C02 in the heat addition process is higher than the acid dew point of the exhaust gases owing to the regeneration.

关 键 词：中温烟气余热 CO2超临界循环 CO2回热超临界循环 优化对比 

分 类 号：TK115[动力工程及工程热物理—热能工程]