基于[火用]分析的CO_(2)压缩液化能耗分析及新工艺

Energy consumption analysis and new process of CO_(2) compression liquefaction based on exergy analysis

在各种二氧化碳捕获技术中,有机胺吸收是当下应用最广泛且最可靠的选择。将液化天然气冷能与二氧化碳压缩液化工艺相结合,一方面可以解决液化天然气冷能利用问题,另一方面也可以直接获得液化二氧化碳所需要的低温,降低能耗。提出一种将液化天然气冷能应用于化学吸收法捕集的二氧化碳压缩液化新工艺,采用有机胺吸收捕集到的高体积分数二氧化碳原料气,运用Aspen Hysys软件,利用Peng-Robison状态方程,对工艺流程进行模拟。探究了传统压缩工艺与泵送压缩工艺的系统性能,发现在泵送工艺下,系统单位质量能耗可由931.65 kJ降低到892.61 kJ,系统[火用]效率从63.28%上升到63.67%,单位质量耗水量从3.84 kg降低到3.01 kg。在此基础上,对泵送工艺进行优化,根据换热介质串联方式的不同,提出了5种优化流程,在最佳优化流程下,系统单位质量能耗为892.60 kJ,系统[火用]效率从63.67%提高到64.10%,单位质量耗水量从3.01 kg降低到2.44 kg。最后对最佳优化流程进行级间冷却温度、换热介质流量的系统敏感性分析,结果表明,级间冷却温度越低,系统能耗越低,[火用]效率越大,10℃时,单位质量能耗最低为879.5 kJ,系统[火用]效率最大为65.5%;换热介质流量对系统能耗影响不明显,但系统[火用]效率随换热介质流量增大而增加,且液化天然气质量流量对系统[火用]效率影响更大,水质量流量为8000 kg/h、液化天然气质量流量为1000 kg/h时,系统[火用]效率最大为68.91%。

Among various carbon dioxide capture technologies,the organic amine absorption is the most widely used and reliable choice today.The combination of liquefied natural gas cold energy with carbon dioxide compression and liquefaction process can not only solve the problem of liquefied natural gas cold energy utilization but also obtain the low temperature required for liquefied carbon dioxide directly,which can reduce energy consumption.A new process of carbon dioxide compression and liquefaction by applying liquefied natural gas cold energy to chemical absorption capture is proposed,using organic amine to absorb the high concentration carbon dioxide feed gas captured,and using Aspen Hysys software to simulate the process flow with Peng-Robison equation of state.Firstly,the system performance of the conventional compression process and the pumping compression process were investigated.It was found that the system unit energy consumption could be reduced from 931.65 kJ/kg gas source to 892.61 kJ/kg gas source under the pumping process,the system exergy efficiency increased from 63.28%to 63.67%,and the water consumption decreased from 3.84 kg gas source to 3.01 kg gas source.On this basis,the pumping process was optimized and five optimized processes were proposed ac-cording to the different ways of heat exchange series connection.Under the optimal optimized process,the system unit en-ergy consumption was 892.61 kJ/kg gas source,the system exergy efficiency increased from 63.67%to 64.10%,and the water consumption decreased from 3.01 kg gas source to 2.44 kg gas source.Finally,the system sensitivity analysis of in-terstage cooling temperature and heat transfer medium flow rate was conducted for the optimal optimized process.The res-ults showed that the lower the interstage cooling temperature,the lower the system energy consumption and the greater the exergy efficiency.The lowest unit energy consumption was 879.5 kJ/kg gas source at 10℃,and the maximum system ex-ergy efficiency was 65.5%.The effect of heat transfer mass flow rate on the system energy consumption was not obvious,but the system exergy efficiency increased with the increase of heat transfer mass flow rate.The effect of liquefied natural gas mass flow rate on the system exergy efficiency was greater,and the system exergy efficiency was 68.91%when the water mass flow rate was 8000 kg/h and the liquefied natural gas mass flow rate was 1000 kg/h.