我国南海深水气田FLNG装置丙烷预冷双氮膨胀液化工艺试验模拟分析

Experimental Simulation Analysis of Propane Pre-Cooling and Dual Nitrogen Expansion Liquefaction Process Adaptable for Floating Liquid Natural Gas （FLNG） in Deep Water Gas Field in the SouthChina Sea

天然气液化工艺是海上浮式液化天然气船FLNG的关键技术之一,目前处在少数几个公司的专利保护之中.由于海上特殊的作业环境,海上FLNG液化工艺的选择与陆上有所不同,研究适合于我国南海海洋环境和油气物性的FLNG液化工艺以及通过试验手段验证FLNG液化工艺在海上的适应性尤为必要.论文分别通过2000m^3/d的小型装置和20000m^3/d的中试装置试验,实现了具有自主知识产权的丙烷预冷双氮膨胀FLNG液化工艺的静态和动态性能的验证.通过将液化关键设备置于晃荡平台上的动态试验以及丙烷分离罐与冷箱之间液位差变化等动态模拟手段,验证了该液化工艺具有较好的海上适应性.2000m^3/d小型试验装置的静态试验模拟表明,在设计规模下,天然气的液化率可达99.1%,能耗可达0.42kw·h/m^3.将冷箱置于晃荡平台上的动态试验表明,船体横摇3.6°时换热性能不受影响.20000m^3/d中试装置的试验表明,该液化工艺具有液化率较高和能耗较低,开停车快速的优点以及较好的海上适应性.通过小型和中试装置的静态和动态试验,表明该液化工艺具有液化率较高、能耗较低以及较好的海上适应性等特点,验证了具有自主知识产权的丙烷预冷双氮膨胀FLNG液化工艺,能较好地适用于我国南海特殊的环境条件和油气物性,可作为我国南海深远海气田开发FLNG工程模式的液化工艺方案之一.

The liquefaction process is one of the key technologies of offshore FLNG device and is charged bypatent protection of a few companies. Because of special offshore operational environment, the choice of FLNG liquefaction process is different from that of onshore. The liquefaction process in FLNG should be suitable for the marine environment and the oil and gas properties in the South China Sea. In this paper, static and dynamic performances of propane pre-cooling and dual nitrogen expansion liquefaction process with independent intellectual property rights have been verified by the simulation in two experimental loops with small scale 2000m^3/d and middle scale 20000m^3/d respectively. Dynamic simulation experimental measures for key liquefied devices such as placing the cold box on the swing platform and propane changing the difference of liquid level between the separation tank, and the cold box, are used to verify offshore adaptability of the liquefaction process. It is indicated through static experiments in a small experimental loop that the liquefaction rate of 93% and energy consumption of 0.42kw·h/m^3 can be reached. Dynamic experimental results through the cold box placed on the swinging platform show that the heat transfer performance of the cold box is not affected when rolling amplitude of the FLNG hull is up to 3.6 degrees. The mid-scale experimental simulation shows that the liquefaction process has the advantages of simple debugging process, convenient operation, quick shutdown and restart, flexible operation, and good adaptability to offshore operating parameters, and can realize 3 sets of simulation of refrigeration cycles. Through static and dynamic experiments in both small and middle scale experimental loops, the propane pre-cooling and dual nitrogen expansion liquefaction process with independent intellectual property rights is verified to have characteristics of high liquefaction rate, low energy consumption and good offshore adaptability, and can be used to develop offshore gas field and faraway from onshore in the South China Sea.