Micro-positive pressure vacuum pressure swing adsorption system and method for safely enriching low-concentration gas

Abstract

A micro-positive pressure vacuum pressure swing adsorption system and method for safely enriching low-concentration gas, using the micro-positive pressure output by a coal mine gas extraction water ring vacuum pump (1) as the gas source pressure; the output of the gas extraction water ring vacuum pump Low-concentration gas enters the intake buffer tank (4) after passing through the dust removal device (2) and dehydration device (3), and then enters the adsorption tower (5); the adsorbent in the adsorption tower absorbs a large amount of oxygen under slightly positive pressure, and at the same time Nitrogen is adsorbed, and methane is basically not adsorbed. The gas with high methane concentration and ultra-low oxygen concentration discharged from the adsorption tower in the adsorption stage is the main product gas, and the gas with high oxygen concentration and ultra-low methane concentration discharged from the vacuum desorption stage is the secondary product gas; The invention can safely and efficiently remove oxygen and nitrogen in low-concentration gas under slight positive pressure, increase the methane concentration under the condition of improving the safety of gas separation, and realize the safe transportation of the concentrated gas.

Description

technical field [0001] The invention relates to a drainage gas concentration system, in particular to a micro positive pressure vacuum pressure swing adsorption system and a method for safe concentration of low-concentration gas, and belongs to the technical field of coal mine gas concentration concentration. Background technique [0002] Coal mine gas is the associated gas of coal, the main component is methane. In recent years, my country's coal mine gas extraction volume has grown steadily year by year, reaching 17.8 billion cubic meters in 2018. However, due to the fact that air leakage is very easy to occur in the underground gas extraction process of coal mines, a large amount of air enters the extraction pipes, resulting in a generally low gas concentration (<30%) in underground coal mine extraction, which is dangerous to explode and difficult to use. The utilization rate of gas extraction is low (<40%), and a large amount of gas is directly discharged into the...

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Problems solved by technology

[0005] Utilizing the principle of equilibrium selectivity to purify oxygen-containing low-concentration gas has obvious technical defects: (1) The oxygen concentration in the adsorption tower is high, and the mixture of methane and high-concentration oxygen has a high risk of explosion; (2) Higher adsorption is required Pressure can achieve a better gas separation effect, such as a Chinese invention patent published on July 17, 2013 with the publication number CN103205297A "A Method for Separating and Purifying Methane in Coalbed Gas in Mine Areas by Pressure Swing Adsorption", China Invention patent published on October 29, 1986 with a publication number of CN85103557 "Pressure swing adsorption method for enriching methane in coal mine gas", and a Chinese invention patent published on December 9, 2009 with a publication number of CN101596391A " A low-concentration gas pressure swing adsorption fractional concentration method" uses adsorption pressures of 0.5MPa-1MPa, 0.4MPa-0.7MPa and 0.8MPa-2.4MPa respectively, so the above methods all need to use a compressor to add coal mine gas. The explosion concentration limit range of gas under high pressure is expanded, and the high-temperature ignition source generated during the pressurization process can detonate the gas, and the pressurization also greatly increases the cost of gas separation; (3) High pressure can easily lead to pulverization of the adsorbent Ineffective, greatly shortening the service life of the adsorbent, using high adsorption pressure requires forward / reverse decompression steps (same as the above-mentioned published patents CN85103557A, CN103205297A, CN101596391A), which increases the complexity of the process; (4) The volume of the adsorption tower in the desorption stage contains A large number of weakly adsorbed components, so the desorbed gas is mixed with a large amount of impurity gas, resulting in a low concentration of methane in the product gas

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