储能式低温空分系统热力学与经济性分析

Thermodynamic and economic analysis of air separation unit with energy storage and generation

低温空气分离设备是大型化工系统的高耗能环节,若与液态空气储能技术相结合,可有效平衡电网峰谷负荷,显著提高系统的经济效益。提出了一种储能式低温空分系统(ASU-ESG),利用谷电制取液态空气并储存,在峰电期内液态空气膨胀发电并参与低温精馏。此方案可有效降低系统在用电峰时的压缩负荷和电力成本,改善空分装置的负荷调节能力。研究结果表明,空气处理量为60000 m^(3)/h的ASU-ESG系统的日均制氧压缩功比功耗为0.378 kW·h/m^(3),储能和释能过程氧提取率分别为89.46%和93.71%。相比常规ASU系统,该系统的谷时压缩负荷提高了28%,峰时压缩负荷降低了20%,可节约年度用电成本5.72%~6.88%,动态回收期仅为3.3~4.3年,全生命周期净现值可达(19714.6~28074.7)万元。本系统可平衡电网峰谷波动,并利用电价差显著提高系统的经济效益。

Low-temperature air separation equipment is a high energy consumption link for large chemical systems.If it is combined with liquid air energy storage technology,it can effectively balance the load of the grid peak valley and significantly improve the economic benefits of the system.This paper introduces an air separation unit with energy storage and generation(ASU-ESG).It uses valley electricity to liquefy air and recovers liquid air for electricity generation and air distillation,thus reducing peak compression loads and improving load regulation ability.The results show that for an ASU-ESG system with an air processing capacity of 60000 m^(3)/h,the power consumption for oxygen production is 0.378 kW·h/m^(3).The oxygen extraction rates for energy storage and energy release processes reach 89.46%and 93.71%,respectively.Compared with conventional ASU,the ASU-ESG improves compression load by 28%during off-peak electricity periods and reduces it by 20%during on-peak electricity periods,resulting in annual electricity cost savings of 5.72%—6.88%.The dynamic payback period for the ASU-ESG system is 3.3—4.3 a,and the net present value(NPV)reaches 19714.6×10^(4)—28074.7×10^(4)CNY.The ASU-ESG system can balance the peakvalley fluctuation in power grids as well as obtain economic benefits in ASU operations.