Abstract:

Naphtha and liquefied natural gas(LNG) products in refineries contain high added value light hydrocarbon resources, so it is necessary to recover light hydrocarbon resources. This paper studies the application of LNG cold energy in light hydrocarbon cryogenic separation in refineries. Four different separation sequences are proposed for light hydrocarbon cryogenic separation units. Under the designed product purity, the feed position and total theoretical plate number of the tower are optimized with the minimum heat load of the reboiler as the goal. Then, the total annual cost(TAC) of each separation sequence is calculated and compared, and the optimal light hydrocarbon cryogenic separation sequence is determined. The results show that the optimal feed position of the first tower in the optimal separation sequence is the 5 th tray, and the total theoretical plate number is 6 trays. Pinch technology is used to optimize the heat exchange network of the optimal separation sequence, heat of 4.42 MW is recovered, and the TAC reduces by 17.8% compared with the basic separation sequence. This study can provide theoretical guidance for the design of light hydrocarbon cryogenic separation process in refineries.

Key words: LNG cold energy, light hydrocarbon, cryogenic separation, total theoretical plate number, feed position, separation sequence, heat exchange network, exergy analysis

摘要：

炼油厂中石脑油及液化天然气(LNG)产品蕴含高附加值的轻烃资源，回收轻烃资源十分必要。研究了LNG冷能在炼油厂轻烃深冷分离的应用，针对轻烃深冷分离装置提出了4种不同的分离序列，在设计产品纯度下，以再沸器热负荷最小为目标对塔的进料位置及总理论板数进行了优化，随后计算每种分离序列的年总费用(TAC)并进行比较，确定了最优的轻烃深冷分离序列。结果表明：最优分离序列中第一座塔最优的进料位置为第5块塔板，总理论板数为6块塔板。采用夹点技术对最优分离序列进行换热网络优化，最终回收了4.42 MW热量，相较基础分离序列的TAC减少了17.8%,这项研究可为炼油厂轻烃深冷分离过程的设计提供理论指导。

关键词: LNG冷能, 轻烃, 深冷分离, 总理论板数, 进料位置, 分离序列, 换热网络, ?分析