Method and device for low-pressure processing of coal bed gas

Abstract

The invention relates to a method for low-pressure processing of coal bed gas, comprising the steps of: introducing the coal bed gas into a hydration reactor from the bottom part of a hydration reactor so as to be contacted with hydrate working liquid in the hydration reactor, leading methane contained in the coal bed gas and water in the hydrate working liquid to generate hydration reaction to form a hydrate which is removed from the coal bed gas; meanwhile, the purified gas is obtained after the methane in the coal bed gas is removed; wherein the operation pressure of the hydration reactor is 0.11-0.85MPa, and the temperature is 3-18 DEG C. The formed hydrate can be further introduced into a hydrate decomposition device for decomposition, thereby obtaining the methane with high concentration. The invention simultaneously relates to a device for realizing the method for low-pressure processing of the coal bed gas. The invention can safely purify the oxygen-containing coal bed gas under lower pressure and remove the contained methane to be lower than 0.05 molar fraction, thereby reducing the emission of the methane, reducing the greenhouse effect and simultaneously avoiding the risk of explosion.

Description

technical field [0001] The present invention relates to a method and device for treating coalbed methane, in particular, the present invention relates to a method for purifying oxygen-containing coalbed methane by using a method of forming hydrate under low pressure conditions to remove methane therein, And a device for realizing the method. Background technique [0002] In coal seams, most of them are accompanied by coalbed methane. There are two main types of coalbed methane, one is the coalbed methane extracted from the ground, and the methane content in this kind of coalbed methane is generally >90%, which is easy to handle and utilize; the other is underground The extracted coalbed methane, also known as gas, is mixed with a large amount of air and has a low methane content, generally around 20% to 60%. Since the explosion limit of methane is 5% to 15%, the utilization of gas has considerable difficulties and risks. Coal mines often directly vent the gas, causing a ...

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Problems solved by technology

[0003] In my country, coalbed methane with high concentration of methane (volume fraction of methane greater than 0.40) is generally utilized through compression or power generation; however, it is difficult to utilize coalbed methane with low methane concentration, especially for methane volume fraction Coalbed methane with a concentration of 0.05 to 0.40, because it is within the explosion limit, is prone to explosion, causing safety accidents, difficult to use and handle, and more directly discharged, which has a great impact on the environment

[0004] Membrane separation and pressure swing adsorption processes currently used to separate mixed gases need to increase the pressure. If membrane separation and pressure swing adsorption technologies are used to treat coalbed methane with a methane volume fraction of 0.05-0.40, the explosion range will be reduced. Larger, difficult to operate at this concentration range and low pressure

[0005] CN85103557B discloses a method for separating and enriching methane from coal mine gas by using pressure swing adsorption technology. However, the oxygen content of the waste gas discharged during the concentration and purification process of methane is also concentrated and increased, and the molar fraction of methane in the waste gas is inevitably It will pass through the range of 5% to 15% explosive gas composition, so that there is always an explosion hazard in the exhaust gas pipeline, and the scheme is difficult to implement

Using the method of cryogenic liquefied gas to purify and separate coalbed methane, under 0.1MPa absolute pressure, CH4, N 2 , O 2 and CO 2 The boiling points are -162°C, -196°C, -133°C and -78°C, respectively, that is, the most difficult to remove N must be lower than -162°C 2 removal, if the oxygen and CO in coalbed methane 2 High content of oxygen and CO at -162°C 2 It will freeze on the refrigeration equipment to block the equipment and reduce the refrigeration efficiency. For gas with an air content of 40% to 60%, liquefaction requires high energy consumption and high equipment costs

[0008] The deoxygenation in coalbed methane generally adopts catalytic deoxidation process, which mainly uses a deoxidation catalyst to react with methane at about 300°C to be removed. Generally, removing 1% of oxygen will cause the catalyst bed to rise by 150°C, and the catalyst bed will rise by 150°C. The upper limit of temperature resistance is generally around 500°C, and the deoxidation limit of each stage is about 1.5%. Therefore, once the oxygen content in coalbed methane is high, multi-stage deoxidation is required. Not only the process is complicated, the operation is difficult, but also a large amount of heat is produced by-product, 1%. Oxygen consumes 0.5% methane at the same time, resulting in low methane yield and uneconomical production implementation

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