温降速率对LNG储罐预冷影响的数值模拟

Simulation on the influence of temperature drop rate on the precooling of LNG storage tanks

LNG储罐在投产前需要进行调试,其中LNG储罐预冷是最重要的环节。采用MATLAB软件,建立16×104 m3地上全容式常压LNG储罐预冷模型,研究预冷过程中LNG喷淋量、BOG排放量、储罐压力、LNG气化率及温降速率的变化规律对LNG储罐预冷的影响。研究结果表明:在恒定温降速率下,LNG喷淋流量逐渐增加、BOG排放流量及储罐压力先增后减、LNG气化率仅在预冷后期逐渐降低;随着温降速率增大,LNG喷淋流量、BOG排放流量及罐内压力均增加,但LNG喷淋总量及BOG排放总量减小,LNG气化率仅在预冷后期随温降速率增大而增大;在温降速率超过3 K/h后,对LNG储罐预冷影响较小;在对LNG储罐进行预冷分析时,太阳辐射的影响不可忽略。为了保障LNG储罐投产工作的顺利开展,建议在预冷前期,将温降速度控制在1 K/h之内;在预冷后期,为提高LNG冷量利用率,应增大温降速率,将平均温降速率控制在2～3 K/h。经过实例验证,LNG储罐预冷模型模拟误差均小于10%,可以满足工程应用要求,对于LNG储罐实际预冷过程、预冷方案设计及预冷参数优化具有参考意义。(图2,表2,参20)

A series of debugging work should be carried out before an LNG tank is put into operation, in which the pre-cooling of LNG tank is the most important part. In this paper, the pre-cooling model of 16×104 m3 ground fullcontainment LNG storage tank was established by MATLAB, to study the changing rules of LNG spray flow, BOG emission flow, tank pressure and LNG vaporization rate in the process of pre-cooling and the influence of the temperature drop rate on the pre-cooing of LNG storage tank. It is indicated that in the process of pre-cooling, the LNG spray flow increases gradually, the BOG emission flow and the tank pressure increase firstly and then decrease, and the LNG vaporization rate only decreases in the late stage of pre-cooling. As the temperature drop rate increases, the LNG vaporization rate only increases in the late stage of pre-cooling, and the LNG spray flow, the BOG emission flow and the tank pressure increase, but the total amounts of LNG spray and BOG emission decrease. When the temperature drop rate exceeds 3 K/h, its effect on the pre-cooling of LNG storage tank is smaller. Solar radiation shall not be neglected in the analysis on the pre-cooling of LNG storage tank. In order to ensure the smooth commissioning of LNG storage tank, it is recommended to control the temperature drop rate less than 1 K/h in the early stage of pre-cooling, and to increase the temperate drop rate and keep the average temperature drop rate 2-3 K/h in the late stage to increase the utilization rate of LNG cold energy. It is verified by actual case that the simulation error of the pre-cooling model of LNG storage tank is less than 10%, which satisfies the engineering application requirements. The research results can be used as the reference for actual pre-cooling process, pre-cooling plan design and pre-cooling parameter optimization of LNG storage tanks.