管输工况对LNG冷能梯级利用效益的影响

Influence of pipeline transportation conditions on the cascading utilization benefit of LNG cold energy

为了拓宽LNG冷能利用厂的选址范围,实现LNG管道输送与冷能利用的协同耦合,对LNG管输与冷能梯级利用工艺流程进行模拟计算。基于化工过程模拟软件HYSYS,建立了LNG过冷态管输与冷能梯级利用的耦合模型。利用PR方程的相平衡计算能力,分析了一定输量下管径与保冷层厚度对冷态输送距离、建设费用的影响,研究了管输距离对冷能梯级利用的经济性影响。结果表明:在一定输量下,以压降为LNG气化主要影响因素的小管径输送工艺方案,其输送距离短、单位管长的造价低,提高保冷等级对其输送距离不会产生显著影响;以LNG潜热为主要冷源的第1级冷能利用工艺,其经济性对输送距离最为敏感,且随着转输距离的增加,其经济效益降低。

In order to broaden the site selection range of the cold energy utilization plants and realize the collaborative coupling between LNG pipeline transportation and cold energy utilization, the technical process of LNG pipe transportation and cascading cold energy utilization was simulated and calculated in this paper. A coupling model for the LNG supercooled pipeline transportation and cascading cold energy utilization was established based on the simulation software HYSYS of chemical process. The influences of pipe diameter and cold-keeping layer thickness on cold transportation distance and construction cost at the constant transportation were analyzed by using the phase equilibrium ability of PR equation. The economic effects of pipeline transportation distance on cascading cold energy utilization were analyzed. It is shown that at the constant transportation, the small diameter transportation scheme with pressure drop as the main influencing factor of LNG gasification is short in transportation distance and low in the cost of unit pipe length, so increasing the cold holding grade has no significant influence on the transportation distance. The first stage cold energy utilization process which takes LNG latent heat as the main cold source is economically the most sensitive to the transportation distance, and its economic benefit decreases with the increasing of transportation distance.