FLNG装置双氮膨胀天然气液化工艺参数的确定

Parameter determination of dual nitrogen expansion technology for gas liquefaction in FLNG unit

为了明确FLNG(Floating Liquefi ed Natural Gas)开发模式在我国海上气田应用的可行性,对海上气田双氮膨胀天然气液化工艺过程及主要参数进行了模拟分析。以目标气田气体组分和温压数据为基础,在保持气体组分、流量、进入液化段的温度及其压力不变的情况下,利用HYSYS软件分析了预冷、液化及过冷3个阶段的出口温度、液化段与过冷段的制冷剂循环压力对液化工艺流程的压缩功率、换热器功率、制冷剂流量、比功率以及冷箱负荷等的影响。结果表明:当液化段中气体的出口温度设定为-75℃,液化段和过冷段制冷剂的循环入口压力分别为3 450 k Pa和1 710 k Pa时,循环系统压缩机组的压缩功率和比功率达到最小值;预冷段的温度设定对制冷剂总压缩功率没有影响,但能够调整预冷段和液化段之间的换热负荷分配。该研究可以为FLNG开发方案的设备选型、技术和经济评估提供参考。

In order to confirm the feasibility to apply FLNG （Floating Liquefied Natural Gas） development model in offshore gas fields, the technological process and main parameters of dual nitrogen expansion for gas liquefaction in domestic offshore gas fields were simulated and analyzed. After the gas composition, temperature and pressure of domestic aimed deepwater gas field were reviewed, the effects of outlet temperature at three stages （precooling, liquefaction and subcooling） and circulating pressure of refrigerant at two stages （liquefaction and subcooling） on compression power of liquefaction process, power of heat exchanger, flow rate of refrigerant, specific power and refrigerator loading were analyzed by HYSYS software while the gas composition, the flow rate and the temperature and pressure at the initial period of liquefaction were kept constant. It is shown that the compression power and the specific power of compressor set in circulating system are the minimum when the gas outlet temperature at the liquefaction stage is set at -75℃ and the refrigerant inlet pressure is 3 450 kPa at the liquefaction stage and 1 710 kPa at subcooling stage. The temperature at the precooling stage has no effect on the total compression power of refrigerant, but it can adjust the distribution of heat exchanging load between the precooling stage and the liquefaction stage. The research results can provide the basis for the equipment selection and technical and economic evaluation of FLNG development program. （7 Figures, 4 Tables, 20 References）