Pre-cooled type coal bed gas nitrogen dilated and liquefied process taking advantage of variable pressure for adsorbing residual pressure

Abstract

The invention provides a coalbed methane nitrogen expansion liquefaction technique by adopting swing pressure to absorb and pre-cool the excess pressure, belonging to the chemical and low temperature technical field. The invention provides an adsorption-liquefaction integrated flow of the high nitrogen content coalbed methane. Before the liquefaction process, most part of the nitrogen in the coalbed methane is removed in the pressure-swing adsorption process; the coalbed is pre-cooled after the nitrogen is expanded by adopting the adsorption excess pressure of the nitrogen; afterwards, the coalbed methane is liquefied by the nitrogen expansion and liquefaction process. The pre-cooling process of the nitrogen with excess pressure saves the refrigerating amount provided for the nitrogen expansion circulation, thereby reducing the compression work of the nitrogen and lowering the liquefaction work of the unit product of the system. Moreover, the higher the nitrogen content in the raw material gas of the coalbed methane, the higher the adsorbed excess pressure and more power dissipation is saved.

Description

technical field [0001] The invention relates to a coalbed gas liquefaction process, in particular to a coalbed gas nitrogen expansion liquefaction process involving high nitrogen content coalbed gas and using pressure swing adsorption residual pressure precooling. It belongs to the field of chemical industry and low temperature technology. Background technique [0002] Coal bed methane (CBM) is a kind of coal mine associated gas with methane as the main component, commonly known as "coal mine gas", which belongs to unconventional natural gas. The development and utilization of coalbed methane can not only provide a clean energy with high calorific value, but also prevent mine disasters caused by gas explosions and reduce the emission of methane, a greenhouse gas, which is of great significance to coal mine safety and environmental protection. my country's coalbed methane reserves are abundant, and they are mainly distributed in the economically developed or relatively devel...

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Problems solved by technology

Zhu Jiaxin, majoring in refrigeration and low temperature at Shanghai Jiaotong University, used the adsorption-liquefaction method to realize the liquefaction of coalbed methane in his master's thesis, directly using the residual pressure of coalbed methane after separation by pressure swing adsorption to reduce the compression power consumption of coalbed methane, but due to nitrogen In the expansion liquefaction process, the nitrogen compression work accounts for a large share of the overall power consumption of the system, so the energy saving effect of reducing the compression power consumption of coalbed methane is not obvious

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