FLNG系统液化过程模拟及火用效率分析

Simulation of Liquefaction Process and Exergy Efficiency Analysis for FLNG System

浮式天然气液化是新兴的海上油气开发技术,但受到海洋环境和船体场地限制,天然气液化时耗功高、效率低,须开展浮式LNG制冷流程模拟及系统火用效率分析优化液化流程.以筛选的P-R方程为天然气液化相平衡计算基础,对天然气液化流程中压缩机、混合器、多股流换热器等设备的热力过程进行模拟;同时基于火用分析原理分析系统中各设备的火用损失,绘制系统的火用流图;揭示能量消耗的主要环节.用敏度分析法计算系统中主要设备的敏度,分析设备对系统火用效率的影响.结果表明:当设备位于系统的主干部位,权重大时,设备的敏度高;系统中各设备的敏度均为正值,即改进任意系统中任一环节火用效率,系统火用效率均提高;换热器和节流阀的敏度相对高,是改善系统效率的最有利环节;而压缩机是制冷系统中主要的火用损失设备,但却不是敏度最大设备.压缩机火用损失最大,占总火用损失的61.44%,节流阀占18.17%,换热器与散热器分别占9.32%和11.07%.

Floating LNG is the emerging technology the marine environment and hull site. It is necessary to to develop offshore oil and gas, but it is limited by carry out floating LNG cooling process simulation and the analysis of exergy efficiency for optimizing liquefaction process because natural gas is liquefied with high power consumption,low efficiency. Floating LNG refrigeration process simulation and system exergy analysis are carried on for the high power consumption problem in the floating natural gas liquefaction technology. Based on the P-R equation, which is used in the phase equilibrium calculation, the thermal process simulations for compressors, mixers, multi-stream heat exchanger and other equipment are finished. And exergy loss of each equipment in the paint system is analyzed on the basis of exergy analysis principle, the exergy flow graph is done and the main steps of energy consumption are revealed. Sensitivity analysis method is used to calculate the sensitivity of main equipment of the system, and then the effects of equipment on the system exergy efficiency are analyzed. The results show that when the equipment is loca- ted in the main part of the system and the weight is high, the sensitivity of the equipment is high. The sen- sitivity of each device in the system is positive,that is to improve the exergy efficiency of any part of the system,and the exergy efficiency of the system is improved. The sensitivity of heat exchanger and throttle valve is relatively high, and it is the most favorable link to improve the efficiency of the system, while the compressor is the main exergy loss equipment in the refrigeration system, but its sensitivity is not the big- gest. The exergy loss of compressor is the largest,accounting for 61.44~ of the total exergy loss,throttle valve of 18.17 % ,heat exchanger and radiator accounted for 9.32% and 11.07%,respectinely.