Low-concentration coalbed methane oxidation device and oxidation method

Abstract

The present invention relates to the technical field of coal mine energy utilization, and specifically to a low-concentration coalbed methane oxidation device and oxidation method. The device includes: an oxidizer, a lifting device, a heat carrier input pipeline and a heat carrier output pipeline; wherein the oxidizer is connected in parallel with the lifting device through the heat carrier input pipeline and the heat carrier output pipeline, so that the heat carrier particles filled in the oxidizer can be circulated between the oxidizer and the lifting device, and are used to contact the feed coalbed methane with the heat carrier particles in the oxidizer for oxidation reaction, and discharge the product flue gas obtained by the reaction. By using a heat carrier circulating moving bed as an oxidation reactor and movable solid hot particles as a heat carrier, it is possible to achieve oxidation treatment of coalbed methane with lower concentrations, with high oxidation efficiency, good continuous stability of device operation, simple operation process and low cost.

Description

Technical Field

[0001] The invention relates to the technical field of coal mine energy utilization, and in particular to a low-concentration coalbed methane oxidation device and an oxidation method. Background Art

[0002] Coalbed methane is a by-product mineral resource produced during coal mining. It contains a large amount of CH4 and is an important clean resource. The development and utilization of coalbed methane resources is particularly important.

[0003] The methane concentration of coalbed methane extracted underground is mostly between 3% and 60%, and contains a considerable proportion of low-concentration coalbed methane. In addition, in the process of coalbed methane mining, in order to ensure safety, the methane concentration in the mining working face and the return air tunnel is required to be less than 1%. The mine often uses air blowing measures to dilute it. This part of extremely low-concentration coalbed methane containing methane is currently mainly discharged directly, and the actual emission volume is huge. Medium- and high-concentration coalbed methane (CH4 content higher than 30%) is easier to use, and the existing coalbed methane utilization technology is also mostly aimed at medium- and high-concentration coalbed methane. It can be directly used as industrial / civilian fuel, enriched and purified to produce natural gas, and gas turbines or internal combustion engines for power generation, with a high utilization rate. However, the utilization technology of low-concentration coalbed methane (CH4 content lower than 30%) is lacking, especially for extremely low-concentration coalbed methane (CH4 content lower than 5%).

[0004] For extremely low concentration coalbed methane, it is difficult to achieve combustion or oxidation. This is mainly because the heat released during the combustion or oxidation process is not enough to maintain the required temperature. The main heat loss in this process is the heat carried away by the high-temperature flue gas from the combustion or oxidation equipment. The current main solution is to achieve self-heating balance in the oxidation and combustion processes through heat storage oxidation with gas circulation switching. Specifically, the device used includes at least one combustion chamber and two honeycomb heat storage bodies A and B. The coalbed methane must be repeatedly switched to flow from the two heat storage bodies into the combustion chamber in turn. During this process, the heat storage body through which the coalbed methane passes is cooled, and at the same time, the coalbed methane is preheated to above the ignition point so that combustion or oxidation occurs, while the other heat storage body absorbs the heat of the high-temperature flue gas generated by the combustion and heats up. One of the two heat storage bodies is used to preheat the coalbed methane, and the other is used to absorb the heat in the high-temperature flue gas, and the operation is repeatedly switched. The main disadvantages of this method include: 1) The heat storage body has a complex structure and high cost, and the repeated switching between high and low temperatures produces large thermal stress and is easily damaged; 2) The frequent and repeated switching of gases requires a high-temperature switching valve, which has extremely high requirements for the valve and is expensive to switch; 3) This method is a cyclic process that requires repeated switching, which has high requirements for the control system, and because it is a non-steady-state operation, there are large fluctuations in the operation, which is not conducive to the operation of the downstream system.

[0005] Therefore, providing a low-concentration coalbed methane combustion or oxidation device with simple structure, continuous operation and low cost is of great significance for the utilization of coalbed methane with a CH4 content below 30%, especially for the utilization of extremely low-concentration coalbed methane. Summary of the invention

[0006] The present invention aims to solve the problem that low-concentration coalbed methane, especially extremely low-concentration coalbed methane, is difficult to stably burn or oxidize, and the problems that existing devices for burning or oxidizing low-concentration coalbed methane have complex structures, poor operating stability and high costs. The present invention provides a low-concentration coalbed methane oxidation device and oxidation method.

[0007] In order to achieve the above-mentioned object, the first aspect of the present invention provides a low-concentration coalbed methane oxidation device, comprising: an oxidizer 1, a lifting device 3, a heat carrier input pipeline 4 and a heat carrier output pipeline 5;

[0008] Among them, the oxidizer 1 is connected in parallel with the lifting equipment 3 through the heat carrier input pipeline 4 and the heat carrier output pipeline 5, so that the heat carrier particles 2 filled in the oxidizer 1 can circulate between the oxidizer 1 and the lifting equipment 3, and are used to bring the feed coalbed methane into contact with the heat carrier particles 2 in the oxidizer 1 for oxidation reaction, and discharge the product flue gas obtained by the reaction.

[0009] The second aspect of the present invention provides a method for oxidizing low-concentration coalbed methane using the low-concentration coalbed methane oxidation device described in the first aspect, the method comprising:

[0010] (A) filling heat carrier particles at room temperature into an oxidizer, and heating the heat carrier particles to increase the temperatures of a preheating zone, a high-temperature oxidation zone, and a heat recovery zone in the oxidizer;

[0011] (B) When the high-temperature oxidation zone of the oxidizer reaches the temperature required for the oxidation reaction, the heating is stopped, and low-concentration coalbed methane is introduced from the bottom of the oxidizer, moves from bottom to top and contacts the heat carrier particles in countercurrent, and preheating, oxidation reaction and heat recovery are successively performed to obtain product flue gas and discharge it from the top of the oxidizer;

[0012] During the preheating, oxidation reaction and heat recovery process, the heat carrier particles circulate between the oxidizer and the lifting equipment under the action of gravity and the elevator, and switch between absorbing and releasing heat while moving from top to bottom in the oxidizer to maintain the continuous oxidation reaction.

[0013] Through the above technical solution, the present invention has the following beneficial effects:

[0014] (1) A heat carrier circulating moving bed is used as an oxidation reactor, so that part of the heat for maintaining gas oxidation is retained inside the equipment instead of being completely lost with the flue gas, thereby maintaining the minimum temperature required for oxidation. At the same time, the use of a complex heat storage body is avoided, and the device structure is simple and the cost is low;

[0015] (2) Using movable solid heat particles as heat carriers, the heat capacity is high, the specific surface area of ​​gas-solid contact is much higher than that of the heat storage body in the prior art, the heat exchange effect is better, and the oxidation treatment of coalbed methane with lower concentration can be achieved;

[0016] (3) It does not involve any gas switching, can achieve continuous and stable operation, has a simple operation process, and will not affect the upstream and downstream processes;

[0017] (4) During the heat absorption and release process, if the heat carrier particles are broken due to thermal stress, they can be removed by simple screening and fresh particles can be added at the same time. This solves the problem that in traditional technology, once the heat storage body is broken, the operation must be stopped for maintenance, and the maintenance cost is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0019] Figure 1 This is the intention of the low-concentration coalbed methane oxidation device provided by the present invention.

[0020] Description of Reference Numerals

[0021] 1- Oxidizer 2- Heat carrier particles 3- Lifting equipment

[0022] 4-heat carrier input pipeline 5-heat carrier output pipeline 6-loading silo

[0023] 7-Screening equipment 11-Preheating zone 12-High temperature oxidation zone

[0024] 13- Heat recovery area 14- Coal bed gas inlet 15- Flue gas outlet

[0025] 16-heat carrier inlet 17-heat carrier outlet DETAILED DESCRIPTION

[0026] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0027] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0028] The first aspect of the present invention provides a low-concentration coalbed methane oxidation device, comprising: an oxidizer 1, a lifting device 3, a heat carrier input pipeline 4 and a heat carrier output pipeline 5;

[0029] Among them, the oxidizer 1 is connected in parallel with the lifting equipment 3 through the heat carrier input pipeline 4 and the heat carrier output pipeline 5, so that the heat carrier particles 2 filled in the oxidizer 1 can circulate between the oxidizer 1 and the lifting equipment 3, and are used to bring the feed coalbed methane into contact with the heat carrier particles 2 in the oxidizer 1 for oxidation reaction, and discharge the product flue gas obtained by the reaction.

[0030] According to the present invention, Figure 1 As shown, preferably, the oxidizer 1 can be a circulating moving bed reactor having an inner cavity for loading heat carrier particles 2, and the aspect ratio of the inner cavity is preferably (3-5): 1, so that the heat carrier particles 2 have a suitable filling height in the oxidizer 1.

[0031] In the present invention, preferably, the inner cavity of the oxidizer 1 is provided with a high temperature resistant wear-resistant layer to reduce the wear of the inner cavity by the heat carrier particles 2 during movement, so that the oxidizer 1 has a longer service life. The oxidizer 1 is also provided with a heat preservation layer to effectively reduce the heat loss caused by the heat inside the reactor being transferred to the outside through heat conduction during the oxidation reaction.

[0032] According to the present invention, preferably, a coalbed methane inlet 14 and a heat carrier outlet 17 are respectively provided at the bottom of the oxidizer 1 , and the heat carrier outlet 17 is connected to the heat carrier output pipeline 5 .

[0033] According to the present invention, preferably, a flue gas outlet 15 and a heat carrier inlet 16 are respectively provided at the top of the oxidizer 1, and the heat carrier inlet 16 is connected to the heat carrier input pipeline 4. Raw coalbed methane is introduced into the oxidizer 1 from the coalbed methane inlet 14, moves from bottom to top in the oxidizer 1 and undergoes oxidation reaction, and the product flue gas obtained by the reaction is discharged from the flue gas outlet 15 and subsequently utilized.

[0034] In the present invention, preferably, both the heat carrier inlet 16 and the heat carrier outlet 17 are provided with gas seals ( Figure 1 ), so as to effectively reduce the leakage of gas in the reactor generated during the process of the heat carrier particles 2 entering or exiting the oxidizer 1.

[0035] In the present invention, preferably, the heat carrier input pipeline 4 and the heat carrier output pipeline 5 are each independently provided with a flow valve ( Figure 1 ), so as to control the flow rate of the heat carrier particles 2 entering the oxidizer 1 and the flow rate of the heat carrier particles 2 discharged from the oxidizer 1.

[0036] According to the present invention, preferably, a burner ( Figure 1 (not shown) is used to heat the heat carrier particles 2 during the startup phase of the oxidation device. Preferably, the burner can be connected to natural gas, liquefied gas or diesel as fuel. Before the oxidation device is started, the heat carrier particles 2 pre-filled in the inner cavity of the oxidizer 1 are at room temperature, and the burner is turned on to release a high-temperature flame into the inner cavity to heat the heat carrier particles 2. The heat carrier particles 2 are contacted with each other for heat conduction to gradually increase the temperature in the oxidizer 1 until the temperature requirement for the oxidation reaction is met and the burner is turned off. One or more burners can be provided, preferably multiple.

[0037] According to the present invention, preferably, the oxidizer 1 is provided with a preheating zone 11, a high-temperature oxidation zone 12 and a heat recovery zone 13 in sequence from bottom to top; wherein, in the oxidizer 1, the feed coalbed methane passes through the preheating zone 11, the high-temperature oxidation zone 12 and the heat recovery zone 13 in sequence from bottom to top, and is in countercurrent contact with the heat carrier particles 2 entering from the top of the oxidizer 1 and moving downward, and the obtained cooled heat carrier particles 2 move downward and are discharged from the oxidizer 1, and the obtained product flue gas is discharged upward from the oxidizer 1.

[0038] In the present invention, the raw coalbed methane is introduced into the oxidizer 1 from the coalbed methane inlet 14, and first enters the preheating zone 11 located at the lower part. In this zone, the feed coalbed methane is countercurrently contacted with the high-temperature heat carrier particles 2 moving downward from the high-temperature oxidation zone 12 during its upward movement. After heat exchange, the feed coalbed methane is preheated and continues to move upward, and the heat carrier particles 2 are cooled and discharged from the heat carrier outlet 17; the preheated coalbed methane enters the high-temperature oxidation zone 12 upward, where it is continuously heated and an oxidation reaction occurs, and the high-temperature flue gas generated by the reaction is The gas continues to move upward and enters the heat recovery zone 13, and the heat released by the reaction maintains the high temperature in the high-temperature oxidation zone 12; the heat carrier particles 2 at room temperature enter the oxidizer 1 from the heat carrier inlet 16 and enter the heat recovery zone 13, and in the process of moving downward, they are in countercurrent contact with the high-temperature flue gas moving upward. After heat exchange, the high-temperature flue gas is cooled and discharged from the flue gas outlet 15 as product flue gas, and the heat carrier particles 2 are heated to a high temperature and continue to move downward into the high-temperature oxidation zone 12, maintaining the temperature of this area so that the oxidation reaction can continue.

[0039] According to the present invention, the lifting device 3 is connected to the oxidizer 1 through the heat carrier input pipeline 4 and the heat carrier output pipeline 5, and is used to lift the heat carrier particles 2 discharged from the bottom of the oxidizer 1 and circulate them into the oxidizer 1 from the top of the oxidizer 1. The lifting device 3 in the present invention has a wide range of choices, and can be any device that can lift granular solids, preferably a lifter.

[0040] According to the present invention, preferably, the heat carrier particles 2 can be solid granular heat storage materials, more preferably porcelain balls and / or ceramsite. The heat carrier particles 2 move from top to bottom in the oxidizer 1 by gravity, and combined with the lift provided by the lifting device 3, they can circulate between the oxidizer 1 and the lifting device 3.

[0041] According to the present invention, preferably, the device further comprises a loading bin 6 and a screening device 7;

[0042] The upper bin 6 is connected to the top of the lifting device 3 and is connected to the oxidizer 1 through the heat carrier input pipeline 4;

[0043] The screening device 7 is connected to the bottom of the lifting device 3 and is connected to the oxidizer 1 through the heat carrier output pipeline 5, so as to screen out the broken heat carrier particles 2 and replenish fresh heat carrier particles 2.

[0044] In the present invention, the loading bin 6 is connected to the oxidizer 1 and the lifting device 3 respectively through the heat carrier input pipeline 4, and is used to store the heat carrier particles 2 lifted up by the lifting device 3, and to circulate a suitable amount of the heat carrier particles 2 into the oxidizer 1 according to the needs of the oxidation reaction.

[0045] In the present invention, the screening device 7 is connected to the oxidizer 1 and the lifting device 3 respectively through the heat carrier output pipeline 5. During the circulation of the heat carrier particles 2, the thermal stress generated by repeated absorption and release of heat or the mutual collision and friction during movement may cause breakage. The broken heat carrier particles can be screened out by the screening device 7, and fresh particles can be added at the same time to ensure the use effect.

[0046] The second aspect of the present invention provides a method for oxidizing low-concentration coalbed methane using the low-concentration coalbed methane oxidation device described in the first aspect, the method comprising:

[0047] (A) filling heat carrier particles at room temperature into an oxidizer, and heating the heat carrier particles to increase the temperatures of a preheating zone, a high-temperature oxidation zone, and a heat recovery zone in the oxidizer;

[0048] (B) When the high-temperature oxidation zone of the oxidizer reaches the temperature required for the oxidation reaction, the heating is stopped, and low-concentration coalbed methane is introduced from the bottom of the oxidizer, moves from bottom to top and contacts the heat carrier particles in countercurrent, and preheating, oxidation reaction and heat recovery are successively performed to obtain product flue gas and discharge it from the top of the oxidizer;

[0049] During the preheating, oxidation reaction and heat recovery process, the heat carrier particles circulate between the oxidizer and the lifting equipment under the action of gravity and the elevator, and switch between absorbing and releasing heat while moving from top to bottom in the oxidizer to maintain the continuous oxidation reaction.

[0050] According to the present invention, the main components of the low-concentration coalbed methane include CH4, CO2 and N2. Preferably, the water vapor dew point temperature of the low-concentration coalbed methane is ≤40°C, and the CH4 content is ≤30v%.

[0051] According to the present invention, the heat carrier particles as heat exchange medium have a high heat capacity, preferably solid granular heat storage materials, more preferably ceramic balls and / or ceramsite that can withstand temperatures of 1500° C. In order to obtain a better heat exchange effect, preferably, the average particle size of the heat carrier particles can be 3-100 mm.

[0052] According to the present invention, step (A) is a preparatory stage before the oxidation reaction. First, heat carrier particles at room temperature are loaded into the inner cavity of the oxidizer, so that the preheating zone, high-temperature oxidation zone and heat recovery zone of the oxidizer are all filled with the heat carrier particles. After that, the filled heat carrier particles are heated, and the heat carrier particles absorb heat and heat up rapidly, and transfer heat by contacting each other, so that the preheating zone, high-temperature oxidation zone and heat recovery zone of the oxidizer are heated. Preferably, by the heating, the temperature of the high-temperature oxidation zone reaches 800-1400°C.

[0053] According to the present invention, in step (B), before the low-concentration coalbed methane is fed to the oxidizer, the low-concentration coalbed methane is preferably subjected to dehydration pretreatment to reduce the moisture content and facilitate the oxidation reaction. The dehydration pretreatment can be carried out by conventional methods in the art, such as cyclone method, molecular sieve adsorption method, air cooling method, etc. Preferably, the water vapor dew point temperature of the low-concentration coalbed methane after dehydration treatment is ≤5°C.

[0054] According to the present invention, in step (B), the low-concentration coalbed methane flow passes through the preheating zone, high-temperature oxidation zone and heat recovery zone of the oxidizer from bottom to top in sequence; wherein, in the preheating zone, it countercurrently contacts with the high-temperature heat carrier particles coming from the high-temperature oxidation zone and moving downward, the feed coalbed methane is preheated and continues to move upward, the high-temperature heat carrier particles are cooled and discharged from the bottom of the oxidizer; the preheated coalbed methane enters the high-temperature oxidation zone, the temperature of which is higher than the ignition point of methane, so that after the coalbed methane enters the zone, the methane undergoes an oxidation reaction rapidly, and the heat released by the reaction maintains the high temperature in the high-temperature oxidation zone. Temperature; the high-temperature flue gas generated by the oxidation reaction continues to move upward and enters the heat recovery zone, in which it is countercurrently contacted with the heat carrier particles with lower temperature that enter the oxidizer from the external circulation and move downward. After heat exchange, the high-temperature flue gas is cooled and discharged from the upper part of the oxidizer as product flue gas, and the heat carrier particles with lower temperature are heated to high temperature to recover the heat brought away by the high-temperature flue gas, and continue to move downward, bringing this part of the heat back to the high-temperature oxidation zone to help maintain the temperature of this area, so that the oxidation reaction of the low-concentration coalbed methane can continue.

[0055] According to the present invention, in step (B), in order to enable the oxidation process of the low-concentration coalbed methane to better achieve self-heating balance, preferably, the ratio of the feed amount of the low-concentration coalbed methane to the circulation amount of the heat carrier particles per unit time (Nm 3 / kg) is (0.5-10): 1. In the present invention, the circulation amount of the heat carrier particles refers to the mass of the heat carrier entering the oxidizer per unit time.

[0056] According to the present invention, in step (B), preferably, the temperature of the oxidation reaction can be 800-1500°C; during the oxidation process of the low-concentration coalbed methane, the temperature of the heat carrier particles discharged from the oxidizer can be 50-120°C, and then enter the screening equipment to screen out the broken particles, while further cooling is achieved, and fresh particles are added as needed to maintain the number and use effect of the heat carrier particles.

[0057] According to the present invention, in step (B), preferably, the temperature of the product flue gas can be 100-400°C. The product flue gas can be used to generate hot water for heating after heat exchange; or introduce a waste heat boiler to generate superheated steam to drive a steam turbine to do work, and connect to a generator to generate electricity.

[0058] The following combination Figure 1 The application process of the low-concentration coalbed methane oxidation method provided by the present invention on the low-concentration coalbed methane oxidation device of the present invention is described.

[0059] The heat carrier particles 2 at room temperature (capable of withstanding a temperature of 1500°C and having an average particle size of 3-100mm) are loaded into the inner cavity of the oxidizer 1, so that the preheating zone 11, the high-temperature oxidation zone 12 and the heat recovery zone 13 are all filled with the heat carrier particles 2; the burner is turned on to release a high-temperature flame to heat the filled heat carrier particles 2, so that the preheating zone 11, the high-temperature oxidation zone 12 and the heat recovery zone 13 are gradually heated up, and the temperature of the high-temperature oxidation zone 12 reaches 800-1400°C;

[0060] Dehydration pretreatment is performed on low-concentration coalbed methane (water vapor dew point temperature ≤ 40°C, CH4 content ≤ 30v%) to make the water vapor dew point temperature ≤ 5°C; after the temperature of the high-temperature oxidation zone 12 rises to the temperature required for the methane oxidation reaction, the burner is turned off, and the dehydrated coalbed methane is introduced into the oxidizer 1 from the coalbed methane inlet 14;

[0061] The feed coalbed methane moves from bottom to top in the oxidizer 1, and first enters the preheating zone 11, where it countercurrently contacts with the high-temperature heat carrier particles 2 moving downward from the high-temperature oxidation zone 12. After heat exchange, the feed coalbed methane is preheated and continues to move upward, and the high-temperature heat carrier particles 2 are cooled to 50-120°C and discharged from the heat carrier outlet 17.

[0062] The preheated coalbed methane moves upward into the high-temperature oxidation zone 12, where an oxidation reaction occurs (the reaction temperature is 800-1500°C), and the high-temperature flue gas generated by the reaction continues to move upward and enters the heat recovery zone 13. The heat released by the reaction maintains the high temperature in the high-temperature oxidation zone 12;

[0063] The heat carrier particles 2 at room temperature enter the heat recovery zone 13 from the heat carrier inlet 16, and in the process of moving downward, they are countercurrently contacted with the high-temperature flue gas moving upward. After heat exchange, the high-temperature flue gas is cooled and discharged from the flue gas outlet 15 as product flue gas (temperature is 100-400°C). The heat carrier particles 2 are heated to a high temperature to recover the heat taken away by the high-temperature flue gas, and continue to move downward to bring part of the heat back to the high-temperature oxidation zone 12 to help maintain the temperature of this area, so that the oxidation reaction of the low-concentration coalbed methane can continue; wherein, the ratio of the feed amount of the low-concentration coalbed methane to the circulation amount of the heat carrier particles 2 per unit time (Nm 3 / kg) is (0.5 -10): 1;

[0064] The heat carrier particles 2 discharged from the heat carrier outlet 17 enter the screening device 7 through the heat carrier output pipeline 5, and the broken particles therein are screened out, and further cooled and replenished with fresh particles; then they are lifted to the upper bin 6 for storage through the lifting device 3, and according to the needs of the oxidation reaction, the cooled heat carrier particles 2 are circulated into the oxidizer 1 through the heat carrier input pipeline 4;

[0065] During the preheating, oxidation reaction and heat recovery process, the heat carrier particles 2 circulate between the oxidizer 1 and the lifting device 3 under the action of gravity and the lifting device 3, and switch between absorbing and releasing heat during the movement from top to bottom in the oxidizer 1 to maintain the continuous oxidation reaction.

[0066] The present invention will be described in detail below by way of examples. In the following examples and comparative examples,

[0067] The content of CH4 in low-concentration coalbed methane and the content of CH4 in the flue gas produced by the oxidation reaction are determined by gas chromatography.

[0068] Example 1

[0069] use Figure 1 The low-concentration coalbed methane oxidation device of the present invention is used to oxidize low-concentration coalbed methane.

[0070] (1) Alumina ceramic balls 2 (capable of withstanding a temperature of 1300° C. and having an average particle size of 25 mm) at room temperature are loaded into the inner cavity of the oxidizer 1, so that the preheating zone 11, the high-temperature oxidation zone 12, and the heat recovery zone 13 are all filled with the alumina ceramic balls 2; the burner is turned on to release a high-temperature flame to heat the filled alumina ceramic balls 2, so that the preheating zone 11, the high-temperature oxidation zone 12, and the heat recovery zone 13 are gradually heated, and the temperature of the high-temperature oxidation zone 12 reaches 1100° C.;

[0071] (2-1) low-concentration coalbed methane (CH4 content of 0.5v%, water vapor dew point temperature of 20°C) is pre-dehydrated by a cyclone method to reduce the water vapor dew point temperature to -2°C; after the temperature of the high-temperature oxidation zone 12 rises to the temperature required for the methane oxidation reaction, the burner is turned off, and the dehydrated coalbed methane is introduced into the oxidizer 1 from the coalbed methane inlet 14;

[0072] (2-2) The feed coalbed methane moves from bottom to top in the oxidizer 1 and first enters the preheating zone 11, where it countercurrently contacts the high-temperature alumina ceramic balls 2 moving downward from the high-temperature oxidation zone 12. After heat exchange, the feed coalbed methane is preheated and continues to move upward, and the high-temperature alumina ceramic balls 2 are cooled to 50° C. and discharged from the heat carrier outlet 17;

[0073] The alumina ceramic balls 2 discharged from the heat carrier outlet 17 enter the screening device 7 through the heat carrier output pipeline 5, where the broken particles are screened out, further cooled, and fresh particles are added; then they are lifted by the lifting device 3 to the upper bin 6 for storage, and the cooled heat carrier particles 2 are circulated into the oxidizer 1 through the heat carrier input pipeline 4 for continued use;

[0074] (2-3) The preheated coalbed methane moves upward into the high-temperature oxidation zone 12, where an oxidation reaction occurs (the reaction temperature is 1150°C). The high-temperature flue gas generated by the reaction continues to move upward and enters the heat recovery zone 13. The heat released by the reaction maintains the high temperature in the high-temperature oxidation zone 12.

[0075] (2-4) The alumina ceramic balls 2 at room temperature enter the heat recovery zone 13 from the heat carrier inlet 16, and in the process of moving downward, they are countercurrently contacted with the high-temperature flue gas moving upward. After heat exchange, the high-temperature flue gas is cooled and discharged from the flue gas outlet 15 as product flue gas (temperature is 150°C). The alumina ceramic balls 2 are heated to a high temperature and continue to move downward into the high-temperature oxidation zone 12 to help maintain the temperature of this area so that the oxidation reaction of the low-concentration coalbed methane can continue; wherein, the ratio of the feed amount of low-concentration coalbed methane to the circulation amount of the alumina ceramic balls 2 per unit time (Nm 3 / kg) is 5:1;

[0076] During the above-mentioned preheating, oxidation reaction and heat recovery process, the alumina ceramic balls 2 circulate between the oxidizer 1 and the lifting device 3 under the action of gravity and the lifting device 3, and switch between absorbing and releasing heat during the movement from top to bottom in the oxidizer 1 to maintain the continuous oxidation reaction.

[0077] According to the test, the CH4 content in the product flue gas discharged from the flue gas outlet 15 is 0.0025v%, and the oxidation efficiency of the low-concentration coalbed methane is calculated to be 99.5%.

[0078] Example 2

[0079] The method of Example 1 is used, except that: the average particle size of the alumina ceramic balls is 40 mm; in step (2-1), the low-concentration coalbed methane (CH4 content is 1v%, and the water vapor dew point temperature is 15°C) is dehydrated by a cyclone method to reduce the water vapor dew point temperature to 2°C; in step (2-2), the temperature of the alumina ceramic balls 2 discharged from the heat carrier outlet 17 is 80°C; in step (2-3), the temperature of the oxidation reaction is 1260°C; in step (2-4), the temperature of the product flue gas discharged from the flue gas outlet 15 is 265°C, and the ratio of the feed amount of low-concentration coalbed methane to the circulation amount of the alumina ceramic balls 2 per unit time (Nm 3 / kg) was 1:1. Other processes and conditions were the same as in Example 1.

[0080] According to the test, the content of CH4 in the product flue gas discharged from the flue gas outlet 15 is 0.015v%, and the oxidation efficiency of the low-concentration coalbed methane is calculated to be 98.5%.

[0081] Example 3

[0082] The method of Example 1 is used, except that: the average particle size of the alumina ceramic balls is 60 mm; in step (2-1), the low-concentration coalbed methane (CH4 content is 20v%, and the water vapor dew point temperature is 30°C) is dehydrated pre-treated by a water-cooled dryer to reduce the water vapor dew point temperature to -5°C; in step (2-2), the temperature of the alumina ceramic balls 2 discharged from the heat carrier outlet 17 is 100°C; in step (2-3), the temperature of the oxidation reaction is 1300°C; in step (2-4), the temperature of the product flue gas discharged from the flue gas outlet 15 is 380°C, and the ratio of the feed amount of low-concentration coalbed methane to the circulation amount of the alumina ceramic balls 2 per unit time (Nm 3 / kg) was 2:1. Other processes and conditions were the same as in Example 1.

[0083] According to the test, the CH4 content in the product flue gas discharged from the flue gas outlet 15 is 0.4v%, and the oxidation efficiency of the low-concentration coalbed methane is calculated to be 98%.

[0084] Comparative Example 1

[0085] The dehydrated pretreated coalbed methane with the same composition as in Example 1 was used, and the coalbed methane was oxidized according to the method disclosed in paragraphs 0020-0023 of the "Specific Implementation Method" of the specification of CN202483648U. The components of the high-temperature gas generated by the oxidation and decomposition of the coalbed methane in the combustion chamber were tested, and the oxidation efficiency of the low-concentration coalbed methane was calculated to be 99%.

[0086] Through the above embodiments and comparative examples, it can be seen that the present invention uses a heat carrier circulating moving bed as an oxidation reactor, and switches between absorbing and releasing heat by circulating solid heat carrier particles in the inner and outer cycles in the process of moving from top to bottom in the oxidizer, which can ensure the efficient oxidation of methane in the gas, and ensure the appropriate amount of heat recovery and heat storage while the gas is continuously oxidized, thereby maintaining the minimum temperature required for oxidation, so that the oxidation process of coalbed methane can reach self-heating balance, and realize continuous oxidation treatment of low-concentration coalbed methane (especially extremely low-concentration coalbed methane), with high oxidation efficiency, simple operation process and low cost. Comparing Example 1 with Comparative Example 1, both oxidize the same extremely low-concentration coalbed methane. In addition to the above advantages, the device and method of the present invention can further improve the oxidation efficiency.

[0087] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A low-concentration coalbed methane oxidation device, characterized in that: include: An oxidizer (1), a lifting device (3), a heat carrier input pipeline (4) and a heat carrier output pipeline (5); The oxidizer (1) is connected in parallel with the lifting device (3) through the heat carrier input pipeline (4) and the heat carrier output pipeline (5), so that the heat carrier particles (2) filled in the oxidizer (1) can be circulated between the oxidizer (1) and the lifting device (3), so as to make the feed coalbed methane contact with the heat carrier particles (2) in the oxidizer (1) for oxidation reaction, and discharge the product flue gas obtained by the reaction; The bottom of the oxidizer (1) is provided with a coalbed methane inlet (14) and a heat carrier outlet (17), and the heat carrier outlet (17) is connected to the heat carrier output pipeline (5); The top of the oxidizer (1) is provided with a flue gas outlet (15) and a heat carrier inlet (16), and the heat carrier inlet (16) is connected to the heat carrier input pipeline (4); The lifting device (3) is connected to the oxidizer (1) through the heat carrier input pipeline (4) and the heat carrier output pipeline (5), and is used to lift the heat carrier particles (2) discharged from the bottom of the oxidizer (1) and circulate them into the oxidizer (1) from the top of the oxidizer (1).

2. The device according to claim 1, wherein: A burner is provided on the lower inner wall of the oxidizer (1) for heating the heat carrier particles (2) during the start-up phase of the oxidizer.

3. The device according to claim 1 or 2, wherein: The oxidizer (1) is provided with a preheating zone (11), a high-temperature oxidation zone (12) and a heat recovery zone (13) in order from bottom to top; Wherein, in the oxidizer (1), the feed coalbed methane passes through the preheating zone (11), the high-temperature oxidation zone (12) and the heat recovery zone (13) from bottom to top in sequence, and is in countercurrent contact with the heat carrier particles (2) entering from the top of the oxidizer (1) and moving downward, and the obtained cooled heat carrier particles (2) move downward and are discharged from the oxidizer (1), and the obtained product flue gas is discharged upward from the oxidizer (1).

4. The device according to claim 1 or 2, wherein: The heat carrier particles (2) are porcelain balls and / or ceramsite.

5. The device according to any one of claims 1 or 2, wherein: The device also includes a loading bin (6) and a screening device (7); The loading bin (6) is connected to the top of the lifting device (3) and is connected to the oxidizer (1) through the heat carrier input pipeline (4); The screening device (7) is connected to the bottom of the lifting device (3) and is connected to the oxidizer (1) through the heat carrier output pipeline (5) to screen out the broken heat carrier particles (2) and replenish fresh heat carrier particles (2).

6. A method for oxidizing low-concentration coalbed methane using the low-concentration coalbed methane oxidation device according to any one of claims 1 to 5, the method comprising: (A) filling heat carrier particles at room temperature into an oxidizer, and heating the heat carrier particles to increase the temperatures of a preheating zone, a high-temperature oxidation zone, and a heat recovery zone in the oxidizer; (B) When the high-temperature oxidation zone of the oxidizer reaches the temperature required for the oxidation reaction, the heating is stopped, and low-concentration coalbed methane is introduced from the bottom of the oxidizer, moves from bottom to top and contacts the heat carrier particles in countercurrent, and preheating, oxidation reaction and heat recovery are successively performed to obtain product flue gas and discharge it from the top of the oxidizer; During the preheating, oxidation reaction and heat recovery process, the heat carrier particles circulate between the oxidizer and the lifting equipment under the action of gravity and the elevator, and switch between absorbing and releasing heat while moving from top to bottom in the oxidizer to maintain the continuous oxidation reaction.

7. The method according to claim 6, wherein: The water vapor dew point temperature of the low-concentration coalbed methane is ≤40°C, and the CH4 content is ≤30v%.

8. The method according to claim 6 or 7, wherein: The heat carrier particles are porcelain balls and / or ceramsite particles that can withstand temperatures of 1500°C; And / or, the average particle size of the heat carrier particles is 3-100 mm.

9. The method according to claim 6 or 7, wherein: In step (A), the temperature of the high temperature oxidation zone is raised to 800-1400°C.

10. The method according to claim 6 or 7, wherein: In step (B), the ratio of the feed amount of the low-concentration coalbed methane to the circulation amount of the heat carrier particles per unit time is (0.5-10):

1.

11. The method according to claim 10, wherein: In step (B), the temperature of the oxidation reaction is 800-1500°C.

12. The method according to claim 10, wherein: In step (B), the temperature of the product flue gas is 100-400°C.

13. The method according to claim 10, wherein: In step (B), during the oxidation process of the low-concentration coalbed methane, the temperature of the heat carrier particles discharged from the oxidizer is 50-120°C.

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