基于单循环混合冷剂的天然气液化工艺优化研究

Research on the optimization of natural gas liquefaction process based on single cycle mixed coolant

为降低液化天然气的单位生产能耗,解决单循环混合冷剂液化工艺中冷剂配比及参数优化的问题,在筛选混合冷剂的前提下,通过混料实验确定了不同冷剂配比下的工艺比功耗和冷剂循环量,在约束条件的限制下,利用回归方程获取了混合冷剂的最佳配比,并进一步优化了冷箱入口混合冷剂的节点参数。结果表明,对于制冷温区为30~-160℃的工艺而言,N_(2)、CH_(4)、C_(2)H_(4)、C_(3)H_(8)和i C_(5)H_(12)作为混合冷剂的效果较好:最佳混合冷剂配比为N_(2):CH_(4):C_(2)H_(4):C_(3)H_(8):i C_(5)H_(12)=8.85%:25.60%:30.55%:19.00%:16.00%,两级压缩机的出口压力有所上升,换热器的出口温度有所降低;冷剂循环量降低,降幅为13.63%;比功耗降低,降幅为25.88%,与优化前相比,能耗大幅降低。该研究结果可为同类天然气处理工艺的能耗优化提供实际参考。

In order to reduce the unit production energy consumption of liquefied natural gas and solve the problem of coolant ratio and parameter optimization in the single cycle mixed coolant liquefac-tion process,under the premise of screening mixed coolant,the process specific power consumption and coolant cycle amount under different coolant ratio are determined through mixing experiments.Under the constraint conditions,the optimal ratio of mixed coolant is obtained by using the regression equation,and the node parameters of the mixed coolant at the inlet of the cold box are further opti-mized.The results show that N_(2)、CH_(4)、C_(2)H_(4)、C_(3)H_(8) and i C_(5)H_(12) are effective as mixed coolants when the cooling temperature range is from 30℃to 160℃.When the optimal mixing coolant ratio is N2∶CH4∶C2H4∶C3H8∶i C_(5)H_(12)=8.85%∶25.60%∶30.55%∶19.00%∶16.00%,the outlet pressure of the two-stage compressor will be increased.But the outlet temperature of the heat exchanger will be decreased.The coolant circulation is reduced,with a decrease of 13.63%.The power consump-tion is reduced,with a decrease of 25.88%,which significantly reduces the energy consumption com-pared with pre-optimization.Even more to the point,the research results can be provided a practical reference for the energy conservation in the same natural gas treatment process.