利用天然气管网压力能的小型液化流程设计

针对城市天然气高中压管网调压站的压力能回收利用,综合考虑LNG储运过程中广泛面临的BOG(Boiloff gas)问题,提出了一种结合混合工质循环、利用天然气压力能生产高品质LNG的小型液化流程。研究分析了预冷温度、动部件效率、低温换热器性能及液化天然气温度对流程天然气液化比的影响,优化的流程结果参数表明,当所得液化天然气储存在4bar,-160℃时,流入系统18.26%的天然气可被液化,其余部分外输中压管网;提出了在LNG买卖市场中根据LNG品质议价的建议,以从根本上减少LNG储运、装卸及使用过程的BOG排放量,进而减少经济损失与能源浪费。该流程可应用于城市燃气调峰,也可进行二次销售,具有较好实用性和经济性。

Design of a small-scale LNG process with the utilization of natural gas pipeline's pressure energy

In facing of recycling the high pressure natural gas pipeline's pressure energy,and the BOG(boil off gas) problem in LNG industry,a small-scale mixed-refrigerant natural gas liquefaction process with the utilization of natural gas pipeline's pressure energy was proposed in this paper.Part of the work was studied on the influence of the gas liquefaction ratio of the process along with some key parameters,such as the precool temperature,efficiency of the movable equipments,the mean temperature difference of the low temperature heat exchanger and the LNG product's temperature.Another part work optimized the process,the optimization results reveals that,the gas liquefaction ratio of the process can reach to 18.26% when the LNG storage at 4 bar,-160℃.According to the analysis results,a suggestion that the LNG price in market should relate to the LNG quality(temperature) was put forward,which can eventually reduce the BOG waste and then the economic losses.This LNG process can be used for natural gas peak-shaving,and the high quality LNG product can be re-sold,which is practical and economical.