Abstract:

Aiming at the problem of waste heat recovery and energy utilization, LNG and heavy oil extraction exhaust gas are used as cold source and heat source respectively, and a waste heat recovery and utilization system combined with natural gas liquefaction and exhaust gas power generation and CO₂ capture is proposed. The effect of key parameters on thermodynamic performance is evaluated. The results show that increasing the turbine inlet temperature, decreasing of turbine outlet pressure and in the compression ratio, have a positive effect on the organic Rankine cycle and refrigeration cycle. The maximum net output power and waste heat recovery efficiency are 454.9 kW and 34.2%, respectively. For the natural gas liquefaction system, the nonlinear optimization of natural gas liquefaction cycles was calculated by using C++. The total power consumption within the nitrogen expansion refrigeration compressors has been selected as the objective function. The nonlinear constrained optimization problem of the liquefaction process is constructed. The optimal total power consumption of the compressors is 101.54 kW. The gas peak load regulation can be taken by decreasing the natural gas compressor (K110) inlet temperature, nitrogen turbine (T3) outlet pressure and its mass flow rate; the maximum value is 378.8 kg/h. On the contrary, the volume of carbon dioxide captured can be increased by 28.6%.

Key words: natural gas, liquefaction, power generation, CO₂ capture, optimization

摘要：

针对余热回收和能源利用的问题，以液化天然气(LNG)作为冷源，稠油开采废气作为热源，提出了一种结合天然气液化和废气发电与CO₂捕集的余热回收利用系统。分析了关键热力学参数对系统热力学性能的影响。结果表明：对于有机朗肯循环和制冷循环，增加透平膨胀机的进口温度，降低其出口压力以及减少制冷循环压缩机进出口的压缩比，可获得最大净输出功为454.9 kW，余热回收效率为34.2%。对于天然气液化系统，采用C++进行非线性约束优化计算，以氮膨胀制冷循环压缩机总功耗为目标函数进行优化，得到压缩机最优总功耗为101.54 kW。降低天然气压缩机(K110)进口温度，氮气膨胀机(T3)出口压力以及氮气质量流量，可获得最大LNG调峰量为378.8 kg/h，反之，CO₂捕集量可提高28.6%。

关键词: 天然气, 液化, 发电, CO₂捕集, 优化