基于NSGA-Ⅱ的二氧化碳氢化反应热力学多目标优化

Multi-objective optimization of the thermodynamics of the hydrogenation of carbon dioxide based on NSGA-Ⅱ

二氧化碳氢化合成低碳烯烃反应是化学储能技术路径中重要的单元反应,二氧化碳首先与由可再生能源获得的氢气进行化学反应合成低碳烯烃,随后通过齐聚反应将能量储存到清洁燃料中。以二氧化碳氢化合成低碳烯烃反应为研究对象,使用Gibbs自由能最小化方法进行了平衡热力学分析,得到反应温度、反应压力、进料气H2与CO_(2)的物质的量比对CO_(2)平衡转化率、低碳烯烃选择性及平衡组分的影响;基于统计学理论建立了反应参数对CO_(2)平衡转化率、低碳烯烃选择性和反应系统中H2O平衡摩尔分数的回归函数模型;最后采用基于快速非支配排序遗传算法(NSGA-Ⅱ)的多目标优化方法对反应系统性能进行多目标优化。结果表明:从提高反应系统性能和降低催化剂水解失效风险角度进行的多目标优化与CO_(2)平衡转化率最大的单目标优化相比,H2O的平衡摩尔分数从47.2%减少到24.9%;与低碳烯烃选择性最大的单目标优化相比,H2O的平衡摩尔分数从51.1%减少到18.7%;与H2O平衡摩尔分数最小的单目标优化相比,CO_(2)平衡转化率和低碳烯烃选择性从64.9%和8.7%分别提高到72.9%和58.6%。

Hydrogenation of carbon dioxide to lower olefins is an important reaction in chemical energy storage technology paths.Carbon dioxide is first chemically reacted with hydrogen obtained from renewable energy sources to form lower olefins,which are then stored as clean fuels through oligomerization.An equilibrium thermodynamic analysis of the hydrogenation of carbon dioxide to lower olefins has been performed using the Gibbs free energy minimization method.The effects of varying the reaction temperature,reaction pressure,the molar ratio of H2to CO_(2)in the feed gas on the CO_(2)equilibrium conversion,the selectivity to lower olefins and the equilibrium components were obtained.Based on statistical theory,regression function models of the effect of the reaction parameters on the CO_(2)equilibrium conversion,the selectivity to lower olefins and the equilibrium mole fraction of H2O in the reaction system were established.Finally,the NSGA-Ⅱmulti-objective optimization algorithm was used to optimize the performance of the reaction system.The results show that compared with the single-objective optimization of maximum CO_(2)equilibrium conversion,multi-objective optimization from the perspective of improving the performance of the reaction system and reducing the risk of catalyst hydrolysis failure reduced the equilibrium mole fraction of H2O from 47.2%to 24.9%.Compared with the single-objective optimization of maximum selectivity to low olefins,the equilibrium mole fraction of H2O was reduced from 51.1%to 18.7%.Compared with the single-objective optimization of minimum equilibrium mole fraction of H2O,the CO_(2)equilibrium conversion and the selectivity to lower olefins increased from 64.9%and 8.7%to 72.9%and 58.6%,respectively.