Low-temperature distillation and liquefying separation recovery system and method for coal bed gas high in nitrogen content, oxygen content and hydrogen content

Abstract

The invention relates to a low-temperature distillation and liquefying separation recovery system and method for coal bed gas high in nitrogen content, oxygen content and hydrogen content. The low-temperature distillation and liquefying separation recovery system is provided with a cold box, a heavy hydrocarbon separation tank, a rectifying tower, an LCPM storage tank, a refrigerant compressor, a cooler, a final-stage gas-liquid separator, a flash gas compressor and a flash gas cooler. The low-temperature distillation and liquefying separation recovery method of the coal bed gas high in nitrogen content, oxygen content and hydrogen content comprises the steps that heavy hydrocarbon separation and liquefaction are conducted on feedstock gas after the feedstock gas is pre-cooled through a pre-cooling section of the cold box; the liquefied feedstock gas enters the rectifying tower for nitrogen removal, oxygen removal and hydrogen removal, and then the liquefied feedstock gas returns into the cold box to be further cooled and then enters the LCPM storage tank; after the gas mixed with refrigerants is compressed and cooled by two stages, the liquid-phase refrigerant separated by the final-stage gas-liquid separator is used for providing cold energy for the pre-cooling section of the cold box; the gaseous-phase refrigerant obtained after separation is used for providing cold energy for the liquefying section and the supercooling section of the cold box; purge gas is heated and then completely exhausted; and flash gas is pressurized and returns to the liquefying section of the cold box to be liquefied again after heat exchange is conducted between the flash gas and the liquid-phase refrigerant. By the adoption of the low-temperature distillation and liquefying separation recovery system and method, the recovery rate of methane can be increased, so that the processing capacity of a device is improved, the energy consumption of the system is reduced, and the production cost is reduced.

Description

technical field [0001] The invention relates to a system and method for separating nitrogen, oxygen and hydrogen in raw gas, in particular to a system and method for separating and recovering high-nitrogen and hydrogen-containing coalbed methane by low-temperature rectification and liquefaction using the principle of liquefaction. Background technique [0002] my country is rich in coalbed methane resources, and the state has continuously introduced policies to promote the development of the coalbed methane industry and improve the utilization rate of coalbed methane resources. Coalbed methane is mainly methane, which is a relatively important energy source and chemical fuel. The composition of coalbed methane is complex. Due to the limitation of processing technology, most of coalbed methane has not been rationally utilized, and its industrial application is seldom. Most of coalbed methane is directly vented, which not only causes a waste of resources, but also seriously po...

AI Technical Summary

Problems solved by technology

At present, various technologies have appeared in the direction of coalbed methane liquefaction. The document with application number 200610103425.0 discloses a low-temperature rectification method applied to the separation and liquefaction of oxygen-containing coalbed methane, which has the advantages of high separation purity and simple device structure. However, this process uses conventional refrigeration methods such as mixed refrigeration or expansion refrigeration, which has a complex structure and low refrigeration efficiency, which reduces the processing capacity of the separation and liquefaction device; the document with the application number 200610080889.4 discloses an air-containing coalbed methane liquefaction process and equipment, using low-temperature two-stage rectification method, the separation purity is high, but the process is complex and the energy consumption is high; the document with the application number 201110319450.3 discloses a coalbed methane liquefaction method and a coalbed methane liquefaction system, the content of which is that coalbed methane is obtained from The process of raw gas from the well to tank storage and transportation takes into account the recovery and utilization of materials and energy, but does not disclose the specific liquefaction process and technical methods for removing impurities in coalbed methane

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