Oxidation apparatus, oxidation method, and oxidation power generation method for low-concentration coal-bed gas

Abstract

The present application relates to the technical field of coal mine energy utilization, and particularly relates to an oxidation device, an oxidation method and an oxidation power generation method for low-concentration coal seam gas. The device comprises a shell, a gas distribution plate, a fixed tube plate and a plurality of heat exchange tubes arranged in the interior of the shell; wherein the gas distribution plate and the fixed tube plate sequentially divide the interior of the shell into an air inlet buffer zone, a gas transmission and heat exchange zone and a combustion zone, and the plurality of heat exchange tubes are arranged in the gas transmission and heat exchange zone and communicate with the air inlet buffer zone and the combustion zone. The low-concentration coal seam gas can be rapidly and continuously oxidized, the oxidation efficiency is high, the device can be continuously and stably operated, the operation process is simple, and the cost is saved.

Description

Technical Field

[0001] This invention relates to the technical field of coal mine energy utilization, specifically to oxidation devices, oxidation methods, and oxidation power generation methods for low-concentration coalbed methane. Background Technology

[0002] Coalbed methane (CBM) is a by-product of coal mining, containing a large amount of methane. To ensure safety during CBM extraction, the "Coal Mine Safety Regulations" require that the methane concentration in the working face and return airway be less than 0.75%. Mines typically use forced draft ventilation to dilute this extremely low concentration of CBM, which is currently mostly directly vented into the atmosphere. Reports indicate that the annual emissions nationwide exceed 20 billion cubic meters (pure methane), a massive amount. The direct release of this extremely low-concentration CBM poses a significant environmental hazard and results in substantial energy waste.

[0003] At present, for exhaust gas with methane concentration below 0.75%, and low-concentration extracted gas with concentration below 1.5% after dilution and blending, regenerative thermal oxidation or regenerative catalytic oxidation devices are mainly used for oxidation, recovering heat while oxidizing the methane. The main disadvantages of existing oxidation devices are: 1) Discontinuous operation, requiring repeated switching of the cycle process. Due to the unsteady-state operation, the upstream and downstream pressure fluctuations are large, which is detrimental to the operation of the downstream system, placing high demands on the control system. Furthermore, repeated switching inevitably leads to residual methane gas in the device, affecting oxidation efficiency; 2) The heat storage body structure is complex and expensive. Repeated switching between high and low temperatures generates significant thermal stress, easily causing damage to the heat storage body; 3) Frequent gas switching requires high-temperature switching valves, placing extremely high demands on the valves and incurring high switching valve costs; 4) Regenerative catalytic oxidation and regenerative thermal oxidation devices are generally similar, but the former also requires a catalyst, which is expensive and economically inefficient.

[0004] Therefore, providing a low-concentration coalbed methane combustion or oxidation device that can operate rapidly and continuously, has high oxidation efficiency, and saves costs is of great practical significance. Summary of the Invention

[0005] In order to overcome the problems of existing coalbed methane oxidation devices and technologies, such as difficulty in achieving rapid and continuous oxidation, repeated switching between high and low temperature processes leading to residual methane gas in the device affecting oxidation efficiency, unsteady operation affecting system stability, and high cost, this invention provides an oxidation device, oxidation method, and oxidation power generation method for low-concentration coalbed methane.

[0006] To achieve the above objectives, the first aspect of the present invention provides an oxidation device for low-concentration coalbed methane, comprising: a shell 1, a gas distribution plate 5, a fixed tube sheet 6, and a plurality of heat exchange tubes 31 disposed inside the shell 1;

[0007] The gas distribution plate 5 and the fixed tube plate 6 divide the interior of the housing 1 into an air intake buffer zone 2, a gas transmission and heat exchange zone 3 and a combustion zone 4 in sequence. The plurality of heat exchange tubes 31 are arranged in the gas transmission and heat exchange zone 3 and connect the air intake buffer zone 2 and the combustion zone 4.

[0008] A second aspect of the present invention provides a method for oxidizing low-concentration coalbed methane using the apparatus described in the first aspect, comprising:

[0009] Low-concentration coalbed methane is introduced into the device and passes sequentially through the inlet buffer zone, gas transmission zone, and heat exchange tube in the heat exchange zone into the combustion zone for oxidation reaction to obtain product flue gas.

[0010] The product flue gas, after leaving the combustion zone, first enters the gas transmission and heat exchange zone, and exchanges heat with the low-concentration coalbed methane through the heat exchange tube, and finally exits from the device.

[0011] A third aspect of the present invention provides a method for generating electricity from low-concentration coalbed methane by oxidation, comprising oxidizing low-concentration coalbed methane using the method described in the second aspect above.

[0012] Through the above technical solution, the present invention has the following beneficial effects:

[0013] (1) The low-concentration coalbed methane oxidation device provided by the present invention is provided with a gas transmission and heat exchange zone. The coalbed methane raw material is transported to the combustion zone for oxidation through multiple heat exchange tubes in the gas transmission and heat exchange zone. During the transportation process, it exchanges heat with the high-temperature product flue gas discharged from the combustion zone in the opposite direction. Through high-efficiency heat exchange, the coalbed methane reaches the ignition point when it enters the combustion zone. The high-temperature product flue gas leaves the device after heat exchange, thereby realizing the rapid and continuous oxidation of low-concentration coalbed methane.

[0014] (2) It does not involve the gas switching process required in existing equipment, avoids methane residue caused by gas switching in traditional technology, and the oxidation efficiency can reach more than 98.5%;

[0015] (3) It can operate continuously and stably, improves processing capacity, simplifies operation, and ensures good system stability.

[0016] (4) The device has a simple structure and does not require the use of complex and expensive heat storage materials, resulting in significant cost savings. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0018] Figure 1 This is a schematic diagram of an oxidation device for low-concentration coalbed methane according to one embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of the gas distribution plate of a low-concentration coalbed methane oxidation device according to one embodiment of the present invention.

[0020] Figure 3 This is a schematic diagram of the fixed tube sheet of a low-concentration coalbed methane oxidation device according to one embodiment of the present invention.

[0021] Explanation of reference numerals in the attached figures

[0022] 1-Shell; 2-Inlet buffer zone; 3-Gas transfer and heat exchange zone

[0023] 4-Combustion zone 5-Gas distribution plate 6-Fixed tube sheet

[0024] 7-Igniter 11-Product flue gas outlet 21-Air inlet

[0025] 31-Heat exchange tube; 51-Gas distribution plate; 52-Inlet hole

[0026] 61-Fixed tube sheet body; 62-Fixed tube hole; 63-Flue gas passage hole

[0027] 64-Fixed Tube Sheet Support Feet Detailed Implementation

[0028] The endpoints and any values ​​of the ranges disclosed herein 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 the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0029] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0030] The first aspect of this invention provides an oxidation device for low-concentration coalbed methane, such as... Figure 1 As shown, it includes: a housing 1, a gas distribution plate 5, a fixed tube sheet 6 and a plurality of heat exchange tubes 31 disposed inside the housing 1;

[0031] The gas distribution plate 5 and the fixed tube plate 6 divide the interior of the housing 1 into an air intake buffer zone 2, a gas transmission and heat exchange zone 3 and a combustion zone 4 in sequence. The plurality of heat exchange tubes 31 are arranged in the gas transmission and heat exchange zone 3 and connect the air intake buffer zone 2 and the combustion zone 4.

[0032] According to the present invention, the shell 1 provides the main structure of the device. The present invention does not have any particular limitations on it; it can be manufactured using conventional materials and parameters, as long as it meets the usage requirements of shells for coalbed methane oxidation devices in the art. Preferably, the shell 1 is provided with linings constructed of refractory bricks and / or refractory castables in the gas transmission and heat exchange zone 3 and the combustion zone 4, and uses heat insulation materials to ensure the strength of the main structure of the device and meet the heat storage and insulation requirements of the area.

[0033] According to the present invention, the gas distribution plate 5 is disposed between the inlet buffer zone 2 and the gas transmission and heat exchange zone 3. The present invention does not impose any particular limitation on the shape of the gas distribution plate 5, as long as it can completely separate the inlet buffer zone 2 and the gas transmission and heat exchange zone 3. The inlet buffer zone 2 is provided with an inlet 21. Coalbed methane feedstock is introduced into the device through the inlet 21, first entering the inlet buffer zone 2 for buffering, and then entering the gas transmission and heat exchange zone 3 through multiple heat exchange pipes 31 connected to the gas distribution plate 5. In the present invention, the inlet buffer zone 2 can reduce the flow rate and concentration of the inlet feedstock, effectively reducing the dead zone of the gas distribution plate 5.

[0034] According to the present invention, the gas distribution plate 5 includes a gas distribution plate body 51, on which a plurality of air inlet holes 52 are distributed. In the present invention, the shape of the air inlet holes 52 and the distribution pattern of the air inlet holes 52 on the gas distribution plate body 51 can be varied, and the present invention does not particularly limit this. A regular and uniform distribution is preferred; for example, it can be including, but is not limited to, the following... Figure 2 The shape and distribution of the air intake holes are shown.

[0035] According to the present invention, preferably, the opening ratio of the gas distribution plate 51 is 30-60%; the cross-sectional area of ​​each air inlet hole 52 in the direction parallel to the gas distribution plate 51 is 3-20% of the area of ​​the gas distribution plate 51. In the present invention, the number of air inlet holes 52 is the same as the number of heat exchange tubes 31. The above-mentioned opening ratio and cross-sectional area parameters of the air inlet holes facilitate a more reasonable distribution of the heat exchange tubes 31 in the bulk transmission and heat exchange zone 3, thereby obtaining better heat exchange effect and coalbed methane oxidation efficiency.

[0036] According to the present invention, the fixed tube sheet 6 is disposed between the gas transmission and heat exchange zone 3 and the combustion zone 4. In this invention, the fixed tube sheet 6 includes a fixed tube sheet body 61, on which fixed tube holes 62 and flue gas passage holes 63 are distributed. The fixed tube holes 62 are used to pass through and fix one end of the heat exchange tube 31, and the flue gas passage holes 63 are used for the high-temperature product flue gas generated in the combustion zone 4 to pass through and enter the gas transmission and heat exchange zone 3. In this invention, the number of fixed tube holes 62 is the same as the number of heat exchange tubes 31.

[0037] According to the present invention, preferably, the area of ​​the fixed tube sheet 6 is 60-85% of the cross-sectional area of ​​the combustion zone 4 in the vertical direction, so that a portion of the high-temperature product flue gas generated in the combustion zone 4 can enter the gas transmission and heat exchange zone 3 from the upper and / or lower part of the combustion zone 4, which is conducive to the faster and more uniform transfer of the high-temperature product flue gas, and promotes better heat exchange effect and coalbed methane oxidation efficiency.

[0038] According to the present invention, the shapes of the fixed pipe holes 62 and the flue gas passage holes 63, as well as the distribution of the fixed pipe holes 62 and the flue gas passage holes 63 on the fixed pipe plate body 61, can be varied. The present invention does not have a particular limitation on this, but a regular and uniform distribution is preferred. For example, it can adopt various forms including but not limited to... Figure 3 The shapes and distribution of the fixed pipe holes and flue gas passages are shown.

[0039] According to the present invention, the fixed tube plate 6 can be connected and fixed to the inner wall of the housing of the device via a plurality of support feet 64. The present invention does not impose any particular limitation on the shape of the fixed tube plate 6.

[0040] According to the present invention, the heat exchange tube 31 penetrates the gas transmission and heat exchange zone 3, and one end of the heat exchange tube 31 is connected to the air inlet 52, while the other end passes through the fixed pipe hole 62 and extends into the combustion zone 4. In the present invention, the heat exchange tube 31 serves as a transport channel for coalbed methane feedstock and also has a highly efficient heat exchange function. The coalbed methane feedstock is transported to the combustion zone 4 through the heat exchange tube 31 for combustion and oxidation, while the high-temperature product flue gas generated in the combustion zone 4 is transferred out. Both enter the gas transmission and heat exchange zone 3 and move in opposite directions, undergoing indirect heat exchange through the heat exchange tube 31, so that the coalbed methane reaches its ignition point when entering the combustion zone 4. Preferably, the heat exchange tube 31 is made of a heat-storing inorganic material, and more preferably, it is made of a heat-storing ceramic.

[0041] According to a preferred embodiment of the present invention, the gas distribution plate 5 and the fixed tube sheet 6 are coaxially arranged. The inlet holes 52 on the gas distribution plate 5 and the fixed tube holes 62 on the fixed tube sheet 6 are uniformly distributed according to the same rule, and the inlet holes 52 and the corresponding fixed tube holes 62 are coaxially arranged. In this case, the multiple heat exchange tubes 31 are arranged parallel and uniformly in the space of the gas transmission and heat exchange zone 3, which facilitates the more uniform entry of coalbed methane into the combustion zone 4 for combustion and oxidation. Furthermore, the consistent gas intake rate promotes better heat exchange and coalbed methane oxidation efficiency.

[0042] According to the present invention, the gas transmission and heat exchange zone 3 is provided with a product flue gas outlet 11. Preferably, the product flue gas outlet 11 is located on the side away from the combustion zone 4, which facilitates the high-temperature product flue gas to leave the device through the product flue gas outlet 11 after sufficient heat exchange.

[0043] According to the present invention, the combustion zone 4 is used for the combustion and oxidation of coalbed methane feedstock to obtain high-temperature product flue gas. The combustion zone 4 is equipped with an igniter 7. Preferably, the igniter 7 is located at the bottom or side wall of the combustion zone 4. The igniter 7 can be externally connected to natural gas, liquefied petroleum gas, or diesel oil as fuel. One or more igniters 7 may be provided.

[0044] According to the present invention, in the oxidation device for low-concentration coalbed methane, there are no particular limitations on the length ratio and vertical cross-sectional area ratio of the gas inlet buffer zone 2, the gas transmission and heat exchange zone 3, and the combustion zone 4. Those skilled in the art can make corresponding settings according to the heat exchange effect and arrangement of the heat exchange tube 31.

[0045] A second aspect of the present invention provides a method for oxidizing low-concentration coalbed methane using the apparatus described in the first aspect, comprising:

[0046] Low-concentration coalbed methane is introduced into the oxidation device of the low-concentration coalbed methane, and passes through the inlet buffer zone, gas transmission and heat exchange tube in the heat exchange zone of the device in sequence, and enters the combustion zone for oxidation reaction to obtain product flue gas.

[0047] The product flue gas, after leaving the combustion zone, first enters the gas transmission and heat exchange zone, and exchanges heat with the low-concentration coalbed methane through the heat exchange tube, and finally exits from the device.

[0048] According to the present invention, the main components of the low-concentration coalbed methane include CH4, CO2 and N2, and preferably, the CH4 content of the low-concentration coalbed methane is ≤1.5v.

[0049] According to the present invention, before the low-concentration coalbed methane is introduced into the device, it is preferable to dehydrate the low-concentration coalbed methane to facilitate the oxidation reaction. The present invention does not particularly limit the dehydration treatment; conventional methods in the art can be used, such as cyclone separation, air cooling, molecular sieve adsorption, etc. The dehydration treatment is only required to ensure that the water content of the low-concentration coalbed methane meets the requirements for combustion oxidation.

[0050] According to the present invention, low-concentration coalbed methane feedstock is introduced into the device after dehydration treatment. It first enters the inlet buffer zone of the device, where the gas velocity decreases and the distribution becomes more uniform. Then, it passes through a gas distribution plate between the inlet buffer zone and the gas transmission and heat exchange zone, and enters multiple heat exchange tubes through inlet holes distributed on the gas distribution plate, and is then transported to the combustion zone. The low-concentration coalbed methane feedstock undergoes combustion oxidation in the combustion zone, producing high-temperature product flue gas containing carbon dioxide and water vapor. In the above process, the low-concentration coalbed methane feedstock is continuously transported to the combustion zone through the heat exchange tubes for combustion oxidation, while the high-temperature product flue gas generated in the combustion zone is continuously transferred out of the combustion zone and into the gas transmission and heat exchange zone. The two move in opposite directions in the gas transmission and heat exchange zone and undergo efficient indirect heat exchange through the heat exchange tubes. The low-concentration coalbed methane feedstock continuously absorbs heat and heats up through heat exchange, reaching its ignition point when it leaves the heat exchange tubes and enters the combustion zone. After entering the combustion chamber, it immediately undergoes an oxidation reaction under high-temperature conditions, achieving rapid and continuous oxidation of the low-concentration coalbed methane.

[0051] According to the present invention, the heat exchange allows the low-concentration coalbed methane to reach a temperature of 700-1000°C when it enters the combustion zone.

[0052] According to the present invention, in the combustion zone, the temperature of the oxidation reaction is 700-1300°C.

[0053] According to the present invention, the temperature of the product flue gas discharged from the device is 50-600°C, and it can be utilized accordingly depending on the temperature. For example, it can be used to generate hot water for use in the mining area after heat exchange, or it can be used for power generation.

[0054] The following combination Figure 1 , Figure 2 and Figure 3 This invention describes a method for oxidizing low-concentration coalbed methane using the oxidation device provided by the present invention.

[0055] Cold start-up stage: Ignition 7, located in combustion zone 4, is turned on to preheat combustion zone 4. When the temperature of combustion zone 4 gradually reaches 700-1000℃, ignition 7 is turned off. Low-concentration coalbed methane (CH4 content ≤1.5v%) is dehydrated and then slowly introduced into combustion zone 4 of the device. Pre-combustion begins at the preheated temperature. The generated high-temperature flue gas enters gas transmission and heat exchange zone 3 from combustion zone 4 and is led out from product flue gas outlet 11. Pre-combustion causes the temperature of combustion zone 4 to rise again. During pre-combustion, the amount of low-concentration coalbed methane entering the device is increased to the rated flow rate. Once the temperature of combustion zone 4 reaches the 700-1300℃ required for oxidation reaction and combustion is stable, the start-up operation is complete.

[0056] Operational Phase: The low-concentration coalbed methane after dehydration is introduced into the device through inlet 21, first entering the inlet buffer zone 2, where the gas velocity decreases and the distribution becomes more uniform. Then, it passes through the gas distribution plate 5 between the inlet buffer zone 2 and the gas transport and heat exchange zone 3, and enters multiple heat exchange tubes 31 through the inlet holes 52 distributed on the gas distribution plate 5. It is then transported to the combustion zone 4 for oxidation reaction (reaction temperature 700-1300℃), producing high-temperature product flue gas containing carbon dioxide and water vapor (temperature 700-1300℃).

[0057] The dehydrated low-concentration coalbed methane is continuously transported to the combustion zone 4 through multiple heat exchange tubes 31. At the same time, the high-temperature product flue gas generated in the combustion zone 4 continuously enters the gas transport and heat exchange zone 3 through the upper and / or lower parts of the combustion zone 4 and the flue gas passages 63 on the fixed tube sheet 6. The two move in opposite directions in the gas transport and heat exchange zone 3 and undergo indirect heat exchange through the heat exchange tubes 31. The low-concentration coalbed methane in the heat exchange tubes 31 continuously absorbs heat and rises in temperature during the transport process, reaching 700-1000°C when it leaves the heat exchange tubes 31 and enters the combustion zone 4. It immediately undergoes an oxidation reaction after entering the combustion chamber 4. After the high-temperature product flue gas undergoes the above-mentioned indirect heat exchange, its temperature drops to 50-600°C and is finally led out from the product flue gas outlet 11 and leaves the device.

[0058] Through the above process, rapid and continuous oxidation of low-concentration coalbed methane can be achieved.

[0059] A third aspect of the present invention provides a method for generating electricity from low-concentration coalbed methane by oxidation, comprising oxidizing low-concentration coalbed methane using the method described in the second aspect above.

[0060] According to the present invention, in the method for generating electricity from low-concentration coalbed methane oxidation, preferably, the product flue gas discharged by the method described in the second aspect of the present invention is sent to a waste heat boiler to generate superheated steam to drive a steam turbine or expander to do work, and connected to a generator to generate electricity.

[0061] According to the present invention, in the oxidation power generation method for low-concentration coalbed methane, preferably, the temperature of the product flue gas is 400-600°C. It should be emphasized that when the temperature of the product flue gas is below 400°C, the power generation requirements cannot be met. In this case, the product flue gas can be used for heat exchange to generate hot water for use in the mining area.

[0062] The present invention will be described in detail below through embodiments. In the following embodiments and comparative examples,

[0063] The CH4 content in low-concentration coalbed methane and the CH4 content in the flue gas produced by oxidation reaction were determined by gas chromatography.

[0064] Example 1

[0065] use Figure 1 The shown oxidation device for low-concentration coalbed methane oxidizes low-concentration coalbed methane. The device employs... Figure 2 The gas distribution plate shown and Figure 3 The fixed tube sheet shown has the same uniform distribution of air inlet holes on the gas distribution plate and fixed tube holes on the fixed tube sheet; the opening ratio of the gas distribution plate is 30%, and the cross-sectional area of ​​each hole on the gas distribution plate in the direction parallel to the gas distribution plate is 18% of the area of ​​the gas distribution plate; the area of ​​the fixed tube sheet is 85% of the cross-sectional area of ​​the combustion zone 4 in the vertical direction; the gas distribution plate and the fixed tube sheet are coaxially arranged, and the air inlet holes are coaxially arranged with the corresponding fixed tube holes.

[0066] Cold start-up phase: Ignition 7 (using natural gas) is turned on to preheat combustion zone 4. When the temperature of combustion zone 4 gradually rises to 900℃, ignition 7 is turned off. Low-concentration coalbed methane (CH4 content of 0.2v%) is dehydrated using a cyclone method and then slowly introduced into combustion zone 4 through inlet 21. It passes through inlet buffer zone 2, gas distribution plate 5, and heat exchange tube 31 (alumina material) for pre-combustion. The high-temperature flue gas generated enters gas transmission and heat exchange zone 3 from combustion zone 4 and preheats heat exchange tube 31. Finally, it is led out from product flue gas outlet 11. Pre-combustion causes combustion zone 4 to heat up again. During pre-combustion, the amount of low-concentration coalbed methane entering the device is gradually increased to the rated flow rate until the temperature of combustion zone 4 reaches 950℃ and combustion is stable. The device startup is complete and ready for oxidation reaction.

[0067] Operational Phase: The dehydrated, low-concentration coalbed methane at the rated flow rate is introduced into the device through inlet 21. It first enters the inlet buffer zone 2, where the gas velocity decreases and the distribution becomes more uniform. Then, it passes through the gas distribution plate 5 and the inlet holes 52 distributed on the plate, entering multiple heat exchange tubes 31 and being transported to the combustion zone 4 for oxidation (reaction temperature 950℃), producing high-temperature product flue gas containing carbon dioxide and water vapor (temperature 950℃).

[0068] The dehydrated low-concentration coalbed methane is continuously transported to the combustion zone 4 through multiple parallel and uniformly arranged heat exchange tubes 31 at the same inlet rate. At the same time, the high-temperature product flue gas generated in the combustion zone 4 continuously enters the gas transmission and heat exchange zone 3 through the upper and lower parts of the combustion zone 4 and the flue gas through-holes 63 on the fixed tube sheet 6. The two move in opposite directions in the gas transmission and heat exchange zone 3 and undergo indirect heat exchange through the heat exchange tubes 31. The low-concentration coalbed methane in the heat exchange tubes 31 continuously absorbs heat and rises in temperature during the transportation process, reaching 900°C when it leaves the heat exchange tubes 31 and enters the combustion zone 4. It immediately undergoes an oxidation reaction after entering the combustion chamber 4. The high-temperature product flue gas continues to undergo the above-mentioned indirect heat exchange as it moves towards the product flue gas outlet 11 in the gas transmission and heat exchange zone 3. The temperature eventually drops to 70°C and is led out from the product flue gas outlet 11, leaving the device.

[0069] The product flue gas drawn from the product flue gas outlet 11 is heated to produce hot water for use in the mining area.

[0070] Tests showed that the CH4 content in the product flue gas discharged from the product flue gas outlet 11 was 0.002v, and the oxidation efficiency of the low-concentration coalbed methane was calculated to be 99.0%.

[0071] Example 2

[0072] The method described in Example 1 differs in that:

[0073] The opening ratio of the gas distribution plate is 45%, and the cross-sectional area of ​​each air inlet hole on the gas distribution plate in the direction parallel to the gas distribution plate is 10% of the area of ​​the gas distribution plate; the area of ​​the fixed tube sheet is 70% of the cross-sectional area of ​​the combustion zone 4 in the vertical direction.

[0074] Low-concentration coalbed methane (CH4 content 0.6v%) is pre-treated by cyclone dehydration. During the cold start-up phase, combustion zone 4 is preheated to 850℃, and after pre-combustion, it finally reaches 990℃. During operation, the oxidation reaction temperature of combustion zone 4 is 990℃, and the temperature of the high-temperature product flue gas containing carbon dioxide and water vapor produced in combustion zone 4 is 990℃. The low-concentration coalbed methane in heat exchange tube 31 reaches 850℃ when it leaves heat exchange tube 31 and enters combustion zone 4. The temperature of the product flue gas drawn from product flue gas outlet 11 is 200℃.

[0075] The product flue gas drawn from the product flue gas outlet 11 is heated to produce hot water for use in the mining area.

[0076] The other processes and conditions are the same as in Example 1.

[0077] Tests showed that the CH4 content in the flue gas discharged from the product gas outlet 11 was 0.009v, and the oxidation efficiency of the low-concentration coalbed methane was calculated to be 98.5%.

[0078] Example 3

[0079] The method described in Example 1 differs in that:

[0080] The gas distribution plate has an opening ratio of 60%, and the cross-sectional area of ​​each air inlet hole on the gas distribution plate in the direction parallel to the gas distribution plate is 5% of the area of ​​the gas distribution plate; the area of ​​the fixed tube sheet is 62% of the cross-sectional area of ​​the combustion zone 4 in the vertical direction.

[0081] Low-concentration coalbed methane (CH4 content 1.2v%) is pre-treated for dehydration using a cyclone method; during the cold start-up phase, combustion zone 4 is preheated to 750℃, and after pre-combustion, it finally reaches 1100℃; during operation, the oxidation reaction temperature of combustion zone 4 is 1100℃, and the temperature of the high-temperature product flue gas containing carbon dioxide and water vapor produced in combustion zone 4 is 1100℃; the low-concentration coalbed methane in heat exchange tube 31 reaches 750℃ when it leaves heat exchange tube 31 and enters combustion zone 4; the temperature of the product flue gas drawn from product flue gas outlet 11 is 420℃;

[0082] The product flue gas drawn from the product flue gas outlet 11 is fed into the screw expander to drive the expander to do work, and the expander is connected to a generator to generate electricity.

[0083] The other processes and conditions are the same as in Example 1.

[0084] Tests showed that the CH4 content in the product flue gas discharged from the product flue gas outlet 11 was 0.018v, and the oxidation efficiency of the low-concentration coalbed methane was calculated to be 98.5%.

[0085] Comparative Example 1

[0086] The device employs a thermal countercurrent oxidation apparatus, currently the most widely used in the field. This apparatus features two parallel packed beds of regenerators. Self-heating equilibrium for coalbed methane oxidation is achieved by repeatedly switching low-concentration coalbed methane between these different packed beds. The low-concentration coalbed methane (CH4 content 0.2 vol%) is dehydrated and then enters the high-temperature packed bed for oxidation (oxidation reaction temperature 950°C). While the high-temperature flue gas is discharged, the heat released by the oxidation reaction is conducted to the low-temperature packed bed, thus preheating it. When the low-temperature packed bed is preheated to 900°C, a high-temperature metal switching valve switches the gas to the low-temperature packed bed for oxidation. This process is repeated to oxidize the low-concentration coalbed methane. The calculated oxidation efficiency for the low-concentration coalbed methane is 91%.

[0087] As can be seen from the above embodiments and comparative examples, the low-concentration coalbed methane oxidation device and method provided by the present invention transport the coalbed methane raw material to the combustion zone through a heat exchange tube for oxidation. During the transportation process, it exchanges heat with the high-temperature product flue gas discharged from the combustion zone, so that the coalbed methane reaches its ignition point when it enters the combustion zone, and then quickly completes the oxidation reaction. This achieves rapid and continuous oxidation treatment of low-concentration coalbed methane. The oxidation process does not involve the gas switching process of the prior art, and it can operate continuously and stably with strong processing capacity and oxidation efficiency of over 98.5%. At the same time, it does not require the use of expensive heat storage materials, thus reducing costs.

[0088] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An oxidation device for low-concentration coalbed methane, characterized in that, include: The shell (1) includes a gas distribution plate (5), a fixed tube sheet (6), and multiple heat exchange tubes (31) disposed inside the shell (1). The gas distribution plate (5) and the fixed tube plate (6) divide the interior of the shell (1) into an air intake buffer zone (2), a gas transmission and heat exchange zone (3) and a combustion zone (4) in sequence. The plurality of heat exchange tubes (31) are arranged in the gas transmission and heat exchange zone (3) and connected to the air intake buffer zone (2) and the combustion zone (4). The gas distribution plate (5) includes a gas distribution plate body (51), on which air inlet holes (52) are distributed; the opening ratio of the gas distribution plate body (51) is 30-60%; the cross-sectional area of ​​each air inlet hole (52) in the direction parallel to the gas distribution plate body (51) is 3-20% of the area of ​​the gas distribution plate body (51); the gas distribution plate (5) is disposed between the air inlet buffer zone (2) and the gas transmission and heat exchange zone (3); the air inlet buffer zone (2) is provided with an air inlet (21). The fixed tube sheet (6) includes a fixed tube sheet body (61), on which fixed tube holes (62) and flue gas passage holes (63) are distributed; the area of ​​the fixed tube sheet (6) is 60-85% of the cross-sectional area of ​​the combustion zone (4) in the vertical direction; the fixed tube sheet (6) is disposed between the gas transmission and heat exchange zone (3) and the combustion zone (4); the heat exchange tube (31) passes through the gas transmission and heat exchange zone (3), and one end of the heat exchange tube (31) is connected to the air inlet passage hole (52), and the other end passes through the fixed tube hole (62) and extends into the combustion zone (4); The gas distribution plate (5) is coaxially arranged with the fixed tube plate (6). The air inlet hole (52) on the gas distribution plate (5) and the fixed tube hole (62) on the fixed tube plate (6) are evenly distributed according to the same rule, and the air inlet hole (52) and the corresponding fixed tube hole (62) are coaxially arranged.

2. The apparatus according to claim 1, wherein, The gas transmission and heat exchange zone (3) is provided with a product flue gas outlet (11). And / or, the combustion zone (4) is provided with an igniter (7).

3. A method for oxidizing low-concentration coalbed methane using the apparatus of claim 1 or 2, comprising: Low-concentration coalbed methane is introduced into the device and passes sequentially through the inlet buffer zone, gas transmission zone, and heat exchange tube in the heat exchange zone into the combustion zone for oxidation reaction to obtain product flue gas. The product flue gas, after leaving the combustion zone, first enters the gas transmission and heat exchange zone, and exchanges heat with the low-concentration coalbed methane through the heat exchange tube, and finally exits from the device.

4. The method according to claim 3, wherein, The CH4 content of the low-concentration coalbed methane is ≤1.5v.

5. The method according to claim 3 or 4, wherein, Through the heat exchange, the temperature of the low-concentration coalbed methane reaches 700-1000℃ when it enters the combustion zone.

6. The method according to claim 3 or 4, wherein, The oxidation reaction is carried out at a temperature of 700-1300℃; And / or, the temperature of the product flue gas discharged from the device is 50-600°C.

7. A method for generating electricity from low-concentration coalbed methane by oxidation, comprising oxidizing low-concentration coalbed methane using the method described in any one of claims 3-6.

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