Coalbed methane deoxidation and concentration method and device based on nitrogen displacement

Abstract

The invention relates to the technical field of gas separation by pressure swing adsorption, and provides a method for deoxygenating and concentrating coalbed methane based on nitrogen replacement, comprising steps: 1. Adsorption; the oxygen in the coalbed methane is removed in an adsorption tower by an adsorption method to obtain rich The collected product gas; 2. Nitrogen replacement; after adsorption, the methane in the adsorption tower is replaced by nitrogen replacement; 3. Pressure reduction and desorption; the oxygen concentration in the enriched product gas is below 0.5%; The concentration of methane in the stripped gas after replacement is below 5%. The invention also provides a device for deoxidizing and concentrating coal bed gas by using the method. The beneficial effects of the present invention are: the concentration of coalbed methane by pressure swing adsorption method is good, the investment and operation cost is low, and the operation is flexible and convenient; nitrogen replacement is used in the separation process to replace part of the methane in the adsorption tower out of the adsorption tower to improve the recovery rate of methane ; At the same time, the concentration of methane in the desorption gas is lower than 5%, ensuring the safety of the desorption process.

Description

technical field [0001] The invention relates to the technical field of pressure swing adsorption gas separation, in particular to a method and device for deoxygenating and concentrating coal bed gas based on nitrogen replacement. Background technique [0002] The content of methane in coalbed methane is generally 20-45%. The shallow coalbed methane resources within 2000 meters in my country are about 36 trillion cubic meters, which is almost the same as the total amount of natural gas resources and ranks third in the world. At present, my country's coal-bed methane emissions due to coal mining are more than 20 billion cubic meters per year, accounting for 1 / 3 of the world's total coal-bed methane emissions from coal mining, ranking first in the world. This not only pollutes the environment, but also causes a lot of waste of energy resources. [0003] One of the main reasons for the low utilization rate of coalbed methane in my country is that the concentration of coalbed me...

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Problems solved by technology

However, this method needs to mix a large amount of nitrogen in the process of use, which undoubtedly increases the difficulty of separation in the process of methane enrichment and increases the energy consumption of methane separation.

[0006] Removing oxygen and then separating it can solve the safety problem in the process of coalbed methane enrichment. For example, patents CN201010256294.6, CN200910083925.6, and CN201110136093.7 propose to use an oxidation method to remove oxygen before enriching, but this method It will undoubtedly increase the complexity of the system and cause the loss of methane

[0007] Patent CN200910312874.X proposes a method of removing oxygen by pressure swing adsorption. However, since the adsorbent mainly adsorbs oxygen, and a small amount of methane is adsorbed by the adsorbent, some methane gas will remain in the gap between the adsorbent, which may lead to desorption of gas. In the case where the concentration of oxygen in the medium is high and the concentration of methane is reduced to the limit of methane explosion, there are certain potential safety hazards

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