System for preparing LNG from oxygen-bearing coal-bed gas based on thermoacoustic technology and method

Abstract

The invention discloses a system for preparing liquefied natural gas (LNG) from oxygen-bearing coal-bed gas based on a thermoacoustic technology and a method. The system comprises a supercharging unit, a purifying unit, a multistage pressure swing adsorption unit, a low-temperature liquefying unit and an LNG storage and transportation unit which are connected sequentially. The system further comprises a thermoacoustic engine unit connected with the low-temperature liquefying unit, wherein the thermoacoustic engine unit combusts part of the coal-bed gas by using the thermoacoustic technology soas to drive a pulse tube refrigerator to work and provide cold energy required by the low-temperature liquefying unit. A liquefying part does not need external power supply completely, the recovery efficiency of the coal-bed gas is increased, factors of the traditional liquefying process that a mixed refrigerant is difficult to prepare, the varying-load working condition adaptability is poor, andthe like are overcome, and thus, the system and the method are particularly applicable to working conditions that the quantity of disperse coal mine or oil-gas wells is small or electric power supplyis absent. In addition, LNG is optionally introduced into the multistage pressure swing adsorption unit, and thus, an adsorption effect is strengthened; and evaporated gas generated by the LNG storage and transportation unit is subjected to heat exchange and then is applied to regeneration of an adsorptive purifier, so that the energy consumption of the system is further lowered, and pollutant emission is reduced.

Description

technical field [0001] The invention relates to the technical field of producing LNG from oxygen-containing coal-bed methane, in particular to a system and method for producing LNG from oxygen-containing coal-bed methane based on thermoacoustic technology. Background technique [0002] The rational development and utilization of coalbed methane can not only supplement natural gas resources to a certain extent, alleviate the shortage of oil and gas resources, but also reduce greenhouse gas emissions and improve coal mine production safety, which has important economic and social benefits. [0003] Coalbed methane can be divided into medium and high concentration coalbed methane (methane content greater than 30%), low concentration coalbed methane (methane content is 10%-30%), very low concentration coalbed methane (methane content 1%-10%) and wind exhaust gas (methane content is less than 1%), which respectively account for 6%, 11% (including low concentration and very low con...

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Problems solved by technology

[0006] In order to solve the problems in the existing oxygen-containing coalbed methane liquefaction process, such as complex process, huge energy consumption, difficult mixing ratio of mixed refrigerants, poor adaptability to variable load conditions, and the need for external power supply, the purpose of the present invention is to provide a thermoacoustic-based System and method for producing LNG from oxygen-containing coalbed methane

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