地下煤制气制取液化天然气和液氢工艺研究

Process research on producing liquefied natural gas and liquid hydrogen by using underground coal-to-gas

关键词:  地下煤制气  低温精馏法  脱酸气  加压液化天然气  液氢 

Key words:  underground coal-to-gas  low temperature rectification method  removement of acid gas  pressurized liquefied natural gas(PLNG)  liquid hydrogen(LH₂)

摘要:

目的 脱除地下煤制气中的酸气,将地下煤制气中的CH₄和H₂分离出来并液化。方法 对常见的分离方法进行对比,确定采用低温精馏法对煤制气进行脱酸气、分离CH₄和H₂并液化。根据低温精馏法的原理,设计了一种全新的地下煤制气脱酸气、分离CH₄和H₂并液化的工艺流程,该工艺主要由两个精馏塔、一个两相分离器和三级氦膨胀制冷系统组成。同时利用HYSYS软件对其进行模拟分析,确定最优参数。结果 该工艺可以将地下煤制气中CO₂的摩尔分数脱除到0,H₂S的摩尔分数脱除到3.65×10-14,满足处理要求。同时可以实现CH₄回收率为99.97%,加压液化天然气(PLNG)的摩尔分数为99.97%,H₂的回收率为98.30%,液氢(LH₂)的摩尔分数为99.99%。结论 该工艺可以有效利用地下煤制气制取PLNG和LH₂,且所需能耗较传统工艺能耗降低了11.64％,具有较高的经济效益。 

Abstract:

Objective The aim is to remove the acid-to-gas, separate and liquefy CH₄ and H₂ in underground coal-to-gas. Methods Comparing the common separation methods, the low temperature rectification method is determined to use for removing acid gas, separating and liquefying CH₄ and H₂. According to the principle of cryogenic rectification, a new process is designed for underground coal-to-gas to remove acid gas and separate and liquefy CH₄ and H₂. This process mainly consists of two rectification towers, a two-phase separator and three-stage helium expansion refrigeration system. Simultaneously, HYSYS software is used to simulate and analyze the process for determination of its optimal parameters. Results This process can remove the molar fraction of CO₂ to 0 and H₂S to 3.65×10-14, meeting the processing requirements. At the same time, the recovery rate of CH₄ is 99.97%, the molar fraction of pressurized liquefied natural gas (PLNG) is 99.97%, the recovery rate of H₂ is 98.30%, and the molar fraction of liquid hydrogen (LH₂) is 99.99%. Conclusion sThis process can effectively use underground coal-to-gas to produce PLNG and LH₂, and the required energy consumption is 11.64% lower than that of traditional processes, which has high economic benefits.