Method and device for low-pressure treatment of coalbed methane

Abstract

The invention relates to a method for treating coalbed methane at low pressure. The method comprises the steps of: introducing the coalbed methane into the hydration reactor from the bottom of the hydration reactor, and contacting the hydrate working liquid in the hydration reactor to make the methane contained in the coalbed methane Hydrate reaction with water in the hydrate working fluid to form hydrate and be removed from the coalbed methane, and at the same time methane in the coalbed methane is removed to obtain purified gas; the operating pressure of the hydration reactor is 0.11-0.85MPa , the temperature is 3 ~ 18 ℃. The formed hydrate can be further introduced into the hydrate decomposer for decomposition to obtain high-concentration methane. At the same time, the invention also relates to a device for realizing the method for processing coal bed gas under low pressure. The invention can safely purify the oxygen-containing coalbed methane at a relatively low pressure, so that the methane in it can be removed to a mole fraction below 0.05, thereby reducing methane emissions, lowering the greenhouse effect, and avoiding the danger of explosion at the same time .

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 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 lot of w...

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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, CH 4 , 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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