乙烯装置预冷系统换热网络的节能优化

Optimization of energy saving for the cold box system of ethylene plant

利用虚拟温度法(流股有效温位)对国内某乙烯装置冷箱系统进行用能诊断分析,找出过程系统的用能“瓶颈”,并针对低温过程传热温差较小以及冷公用工程采用中间公用工程的特点,提出了低温过程多流股换热器网络的综合方法;该方法能够有效的利用冷热流股的有效温位,使冷公用工程的操作费用达到最小,得到合理的换热网络,并且在优化流股传热温差贡献值过程中,考虑了各流股温度、传热膜系数和换热器材质的影响,因此可以用于不同材质、不同传热膜系数低温换热网络的设计和优化;将该方法应用于国内某乙烯装置冷箱系统的综合中,与现场用能情况相比,冷公用工程用量降低了44.5%;结果表明该方法在工程中是可行的。

Energy diagnosis on the cold box system of ethylene plant is done by using method of stream pseudo temperature(stream effective temperature level) and the 'bottleneck' of process is found.A method of synthesizing multi-stream heat exchanger network of low temperature process is presented,which can be solved by Genetic/Simulated Annealing algorithm(GA/SA) optimizing stream heat transfer temperature difference contribution values,and a reasonable multi-stream heat exchanger network is obtained.Compared with the energy used in the cold box system of an exiting ethylene plant,the quantity of the cold utility decreases 44.5%.Moreover,in optimization of stream heat transfer temperature difference contribution values,the effects of stream temperature,heat transfer film coefficient and material of construction on heat exchanger network synthesis has been considered,so this approach can be used to optimize and design heat exchanger network synthesis with unequal heat transfer film coefficients and different materials of construction.The results indicate that the method presented in this paper is feasible to solve the energy integration of large-scale engineering problem.