双循环混合制冷剂天然气液化流程的优化模拟

Optimization simulation of natural gas liquefaction process with double mixed refrigerant cycle

为了降低天然气液化工厂中液化单元双循环混合制冷剂天然气液化流程(DMR)的功耗,文中采用化工过程模拟软件HYSYS建立了优化计算模型,该模型以系统最小功耗为目标函数,以混合制冷剂压力和配比为决策变量,选取了一种典型的天然气组分对DMR液化流程进行了优化模拟,得到了流程中各点的状态参数、最优操作参数和最优混合制冷剂配比。在优化过程中发现,优化的实质是:在满足各换热器最小温差情况下,通过对混合冷剂配比和流程参数的优化使各换热器内的平均换热温差尽可能减小。此外,在保证99.6%的高天然气液化率的情况下,文中得到流程的单位质量天然气的液化功耗为271 kW/t,液化■效率为45.4%,与国内现行的DMR流程功耗相比,能耗显著降低。

In order to reduce the power consumption of the natural gas liquefaction process with double mixed refrigerant cycle(DMR)in liquefaction units of natural gas liquefaction plants,the model of optimization calculation was established by using HYSYS and simulation software of chemical process.In the model,the minimum system power consumption is regarded as the objective function,the mixed refrigerant pressure and the ratio are regarded as decision variables.The DMR liquefaction process is optimized simulation,and state parameters at various points in the process,the optimal operating parameters and the optimal ratios of mixed refrigerants are obtained through choosing a typical component of natural gas.The essence of optimization simulation is that when the minimum temperature difference of each heat exchanger is satisfied,the average heat transfer temperature difference of each heat exchanger is minimized by optimizing the ratio of mixed refrigerant and flow parameters.Gas liquefaction power consumption of unit mass in the process is 271 kW/t,the liquefied energy efficiency is 45.4%at the condition of natural gas liquefaction rate is up to 99.6%.Compared with domestic power consumption in DMR process,energy consumption decreased significantly.