Deoxidation and denitrification system for oxygen-containing coal bed gas

Abstract

The invention discloses a deoxidation and denitrification system for an oxygen-containing coal bed gas. The deoxidation and denitrification system comprises a cold box, a rectifying tower, a coal bed gas deoxidation and denitrification mechanism, a hybrid refrigerant circulation mechanism and a nitrogen refrigerant circulation mechanism, wherein the hybrid refrigerant circulation mechanism is used for supply cooling capacity for the cold box; the nitrogen refrigerant circulation mechanism is used for supply cooling capacity for the cold box and the rectifying tower; the coal bed gas deoxidation and denitrification mechanism comprises a feed gas pipeline, a after-condenser arranged on the top of the rectifying tower and a reboiler arranged at the bottom of the rectifying tower; the feed gas pipeline is communicated with the cold box, is subsequently led out from the cold box, and is communicated with the reboiler; the feed gas pipeline is led out from the reboiler, is subsequently fed into the cold box, is led out from the cold box and is communicated with the rectifying tower; a gas phase outlet of the reboiler is communicated with the cold box through a pipeline; the pipeline is cooled through the cold box and is subsequently communicated with an LNG (Liquefied Natural Gas) storage tank. Due to adoption of the deoxidation and denitrification system, a hybrid coal bed gas that the methane content of the feed gas is 30-90% can be gasified, carbon emission is reduced, and natural gas resources can be recycled to the maximum extent.

Description

technical field [0001] The invention relates to a deoxygenation and denitrification system for oxygen-containing coal bed gas, belonging to the technical field of natural gas liquefaction. Background technique [0002] The coalbed methane extracted during the coal mining process has relatively low methane content, usually 30% to 70% (volume fraction), and other components mainly include carbon dioxide and air. In 2010, 7.6 billion m3 of coalbed methane was extracted underground in my country, and the utilization amount was about 2.43 billion m3, which was less than 32%. my country's coalbed methane resources are abundant, but relatively little development, almost no industrial application. Because coalbed methane pours into the coal mine roadway or explodes, it will cause disasters. Therefore, the coal industry has always regarded coalbed methane as a disaster gas. At present, the drainage treatment of oxygen-containing coalbed methane mixed with air is only based on the s...

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Problems solved by technology

[0003] At present, there are several invention patent applications for the separation process and equipment of oxygen-containing coalbed methane, such as the Chinese patent application No. 200610080889.4. The stage rectification process is complicated, there are many equipments, and the pressure loss of the rectification tower is relatively large. Since the system adopts a low-pressure process, the energy consumption of the process is relatively high

No. 200610103425.0 Chinese patent application adopts cryogenic rectification method for the separation and liquefaction of oxygen-containing coalbed methane, but this process adopts conventional refrigeration methods such as mixed refrigeration or expansion refrigeration, and the auxiliary mechanical refrigeration efficiency such as turbo expander is low, which reduces the separation and liquefaction capacity

This process is relatively complicated, and it needs to consume a large amount of methane to react with oxygen, and the contained N 2 still needs further processing

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