天然气液化与轻烃回收联产工艺研究

Study on cogeneration of LNG and light hydrocarbon recovery process

在分析天然气液化、轻烃回收工艺共同点的基础上,提出将混合制冷循环(MRC)天然气液化与吸收塔(DHX塔)轻烃回收等传统工艺结合的联产工艺,用液化过程的混合制冷循环为轻烃回收提供冷量,同时通过轻烃回收过程对原料气中的重组分进行分离、加工。为进一步研究联产工艺在提高产量、降低能耗方面的优势以及适用气质,利用HYSYS分别对7组不同原料气的联产工艺和传统工艺进行模拟。结果显示,在所有气质条件下,两种工艺的C_3收率、液化石油气产量、稳定轻油产量基本相等,联产工艺可提高液化过程重组分分离效率,使LNG中C_3摩尔分数≤0.3%。联产工艺生产一、二级LNG分别要求原料气中C_1、C_2摩尔分数y(C_1)/y(C_2)≥5.67、y(C_1)/y(C_2)≥3。同时,联产工艺适用于C_2^+摩尔分数≥7%的原料气,在该条件下,LNG产量提高约71.89%,单位能耗降低约17.66%。

On the common base of process of liquefied natural gas and light hydrocarbon recovery, the cogeneration process of LNG and light hydrocarbon recovery has been presented, which provides cold energy for light hydrocarbon recovery process by the mixed refrigeration cycle, meanwhile separates the heavy ends of feed gas through the light hydrocarbon recovery. In order to further research of efficiency of cogeneration process on enhancing yield, reducing energy consumption and the suitable feed gases, the HYSYS simulation software has been developed to simulate the processes with seven groups of feed gas conditions and operating parameters. Results show that the recovery of C3, the yield of liquefied petroleum gas and stabilized light oil are equal basically. The cogeneration process can improve the separation efficiency of liquefaction process, and make the C3 content less than 0.3% in LNG. In order to produce the first degree or the second degree of LNG,y（C1）/y（C2）≥5.67 or y（C1）/y（C2）≥3 of feed gas is required respectively. At the same time, the cogeneration process is suitable for the feed gas whose molar fraction of C2 ^＋is more than 0.07. Under this condition, the LNG production increases 71.89% on average, and the unit energy consumption reduces 17.66% on average.