Ventilation air methane chemical energy recovery system and method

Abstract

The invention relates to the field of energy recovery, in particular to a ventilation air methane chemical energy recovery system and method. The system comprises a heat storage cavity, a preheater, a valve control assembly and a metal oxide heat storage medium. Wherein the heat storage cavity is provided with a plurality of gas inlets and a plurality of gas outlets; the preheater is connected with the heat storage cavity, and the heat storage cavity is heated to the autoxidation temperature of the ventilation air methane before the ventilation air methane enters the heat storage cavity; the multiple gas inlets and the multiple gas outlets can be independently opened and closed through the valve control assembly; the metal oxide heat storage medium is arranged in the heat storage cavity and used for recycling and storing chemical energy of ventilation air methane. The chemical energy of the ventilation air methane can be effectively recovered and efficiently utilized by utilizing the better heat storage density and longer heat storage time of the metal oxide heat storage medium, and the negative influence on the atmospheric environment quality in the exploitation process of petrochemical energy is reduced to a certain extent.

Description

Technical Field

[0001] The present invention relates to the field of energy recovery, and specifically to a system and method for recovering the chemical energy of ventilation air methane (VAM). Background Art

[0002] According to statistics, the amount of pure methane in the VAM directly discharged in China every year is 20 billion cubic meters. Such energy is basically not developed and utilized, including VAM.

[0003] VAM is often generated during the coal mining process. To ensure the safety of the mine, a large amount of fresh air is sent into the mine by the ventilation system, which significantly reduces the methane concentration in the mine until the VAM with a methane concentration less than 1% is diluted. Due to the low methane concentration in VAM, it is difficult to effectively recover and utilize it with existing technologies. Therefore, VAM in the mine is usually discharged into the atmosphere in the form of direct evacuation.

[0004] The current treatment method of VAM not only causes a large amount of energy waste, but also has a negative impact on the atmospheric environmental quality, endangering human health and the balance of the ecosystem. At the same time, there are still certain safety risks in directly evacuating VAM, which further affects the lives of coal miners and the normal production and operation of coal mines. Summary of the Invention

[0005] In view of the above problems, the present invention provides a system and method for recovering the chemical energy of VAM, which can conveniently and effectively recover the chemical energy of VAM originally planned to be directly evacuated and convert it into other energy products with economic value, further improving the available value of petrochemical energy and effectively reducing its pollution to the atmospheric environment.

[0006] In the first aspect of the present invention, a system for recovering the chemical energy of VAM is provided, including: a heat storage chamber, a preheater, and a metal oxide heat storage medium. Among them, the heat storage chamber is provided with a plurality of VAM inlets and a plurality of VAM outlets; the preheater is connected to the heat storage chamber and heats the heat storage chamber to the self-oxidation temperature of VAM before the VAM enters the heat storage chamber; the metal oxide heat storage medium is arranged in the heat storage chamber and is used for recovering and storing the chemical energy of VAM.

[0007] Optionally, the system for recovering the chemical energy of VAM further includes a valve control component, which can independently open and close the plurality of VAM inlets and the plurality of VAM outlets.

[0008] Optionally, the metal element in the metal oxide heat storage medium includes at least one of copper and manganese, and the state of the metal oxide heat storage medium is in the form of particles.

[0009] Optionally, the low-concentration methane chemical energy recovery system further includes a packed bed, which is arranged inside the heat storage cavity and located between the methane inlet and the methane outlet; the packed bed includes multiple layers of bed bodies, dividing the inside of the heat storage cavity into a multi-layer structure, and the metal oxide heat storage medium is distributed in the bed bodies.

[0010] Optionally, the low-concentration methane chemical energy recovery system further includes a buffer storage tank, and the exhaust port of the buffer storage tank is connected to the methane inlet of the heat storage cavity, which is used for buffering and storing the low-concentration methane to be introduced into the heat storage cavity from the outside.

[0011] Optionally, the low-concentration methane chemical energy recovery system further includes an air heat exchange unit, and the air heat exchange unit includes heat exchange tubes, which are arranged inside the heat storage cavity.

[0012] Optionally, the air heat exchange unit further includes a compressor and a turbine. The compressor compresses the cold air that is about to enter the heat storage cavity for heat exchange, and the turbine converts the thermal energy contained in the hot air after heat exchange into mechanical energy.

[0013] Optionally, the outer end of the methane outlet of the heat storage cavity faces the cold air inlet end in the air heat exchange unit, and the exhaust gas flow of the low-concentration methane is used to preheat the cold air that is about to enter the heat exchange tubes for heat exchange.

[0014] The second aspect of the present invention provides a method for recovering the chemical energy of low-concentration methane, which is used for the above-mentioned low-concentration methane chemical energy recovery system, and includes the following steps:

[0015] Preheating step: Before the low-concentration methane is introduced into the heat storage cavity, the heat storage cavity is heated to the self-oxidation temperature of the low-concentration methane through a preheater.

[0016] Oxidation heat release step: Adjust the valve control assembly to make the low-concentration methane enter the heat storage cavity through the methane inlet and start to release heat by oxidation.

[0017] Heat storage step: The metal oxide heat storage medium in the heat storage cavity undergoes a reduction endothermic reaction when heated, stores heat and releases oxygen.

[0018] Optionally, the method for recovering the chemical energy of low-concentration methane further includes:

[0019] Buffering step: Before the preheating step is completed, the low-concentration methane to be subjected to the oxidation heat release step from the outside is introduced into the buffer storage tank.

[0020] Low-concentration methane flow direction switching step: Adjust the valve control assembly to periodically switch the opening and closing of the methane inlet and the methane outlet of the heat storage cavity, so as to change the gas flow direction of the low-concentration methane gas flow in the heat storage cavity.

[0021] Heat exchange step: Cold air is introduced into the heat exchange tubes in the heat storage chamber through the air heat exchange unit to further recover the heat energy released by the exhausted mine gas during the oxidation exothermic step and convert it into the heat energy of the air in the heat exchange tubes.

[0022] Tail gas heat recovery step: After the tail gas of the exhausted mine gas that has completed the oxidation exothermic step in the heat storage chamber is discharged through the gas outlet, the tail gas flow is directed to the cold air inlet of the air heat exchange unit for heat exchange to recover heat.

[0023] When the exhausted mine gas chemical energy recovery system provided by the present invention starts to operate, first, the heat storage chamber is preheated to the self-oxidation temperature of the exhausted mine gas through the preheater, and then the collected exhausted mine gas is introduced into the heat storage chamber to start the "flameless" oxidation reaction, releasing heat and heating the gas flow. The oxidized high-temperature gas continues to flow through the downstream heat storage chamber and stores the heat in the metal oxide heat storage medium.

[0024] In the above heat storage process, the metal oxide heat storage medium is selected as the heat storage material in the exhausted mine gas chemical energy recovery system. On the one hand, because it will undergo a reduction reaction and release a large amount of oxygen when heated, which further promotes the oxidation exothermic process of the exhausted mine gas, so as to better convert the chemical energy of the exhausted mine gas into the heat energy and chemical energy of the metal oxide heat storage medium; on the other hand, the "self-adaptive" characteristic of the metal oxide heat storage medium can effectively suppress the temperature fluctuation inside the heat storage chamber. Its high energy storage density and long energy storage time enable the recovered and stored heat to meet the heating requirements of a large scale. Description of the Drawings

[0025] Figure 1 is a schematic structural diagram of an exhausted mine gas chemical energy recovery system provided by an embodiment of the present invention.

[0026] Figure 2 is a flowchart of an exhausted mine gas chemical energy recovery method provided by an embodiment of the present invention.

[0027] Figure 3 is a flowchart of another exhausted mine gas chemical energy recovery method provided by an embodiment of the present invention.

[0028] Reference numerals: 100 - Exhausted mine gas chemical energy recovery system, 1 - Heat storage chamber, 11 - Gas inlet, 111 - First gas inlet, 112 - Second gas inlet, 12 - Gas outlet, 121 - First gas outlet, 122 - Second gas outlet, 13 - Valve control assembly, 2 - Preheater, 3 - Metal oxide heat storage medium, 4 - Packed bed, 41 - Bed body, 42 - Partition board, 5 - Buffer storage tank, 6 - Air heat exchange unit, 61 - Compressor, 62 - Turbine. Detailed Embodiments

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] <The first embodiment>

[0031] Taking the large amount of exhausted air gas discharged in a mine as an example, since the methane concentration in such gas is relatively low, its calorific value is low, and it is difficult to be directly used as fuel, which makes the cost of collecting and utilizing the exhausted air gas relatively high. Aiming at the problems of energy waste and environmental pollution caused by the exhausted air gas that is often treated by evacuation, this embodiment provides an exhausted air gas chemical energy recovery system 100, which can transfer and store the heat energy released by the exhausted air gas in the form of exothermic oxidation in the heat storage chamber 1, and finally convert the chemical energy in the exhausted air gas into an energy product with economic value. Refer to Figure 1 The system includes: a heat storage chamber 1, a preheater 2, and a metal oxide heat storage medium 3. Among them, the heat storage chamber 1 is provided with a plurality of gas inlets 11 and a plurality of gas outlets 12; the preheater 2 is connected to the heat storage chamber 1 and heats the heat storage chamber 1 to the self-oxidation temperature of the exhausted air gas before the exhausted air gas enters the heat storage chamber 1; the metal oxide heat storage medium 3 is arranged in the heat storage chamber 1 and is used to recover and store the chemical energy of the exhausted air gas.

[0032] To ensure that the exhausted air gas chemical energy recovery system 100 can be normally started and operated, it is necessary to preheat the heat storage chamber 1 to the self-oxidation critical temperature of the exhausted air gas in advance, so as to provide the necessary thermodynamic conditions for the "flameless" oxidation reaction of the subsequent exhausted air gas entering the heat storage chamber 1. In this embodiment, the heat storage chamber 1 is quickly heated by the preheater 2, and the heat storage chamber 1 can be rapidly increased from room temperature to 900 °C or other required temperature ranges. After the internal temperature of the heat storage chamber 1 reaches the self-oxidation temperature of the exhausted air gas, refer to Figure 1 One of the gas inlets 11 of the heat storage chamber 1 is used to introduce the exhausted air gas into the interior of the heat storage chamber 1 to start the "flameless" oxidation reaction. During the oxidation reaction, the exhausted air gas releases heat and heats the heat storage chamber 1. Subsequently, under the heat conduction and radiation of the heat storage chamber 1, the heat generated by the exhausted air gas starts to "flow back" to the gas inlet 11 to achieve the purpose of preheating the inlet air. At this time, the preheater 2 can be turned off or the heating temperature of the preheater 2 can be reduced, and the heat generated by the exhausted air gas itself inside the heat storage chamber 1 is used to make the subsequent exhausted air gas entering the heat storage chamber 1 reach the self-oxidation temperature.

[0033] Since the methane concentration in the exhaust gas is low, the heat released during the oxidation reaction is relatively limited. If the gas inlet 11 and the gas outlet 12 of the heat storage chamber 1 are fixed, the gas intake and exhaust inside the heat storage chamber 1 are carried out in a single flow direction, so that the heat storage chamber 1 at one end of the gas inlet 11 is heated first, and the heat storage chamber 1 at one end of the gas outlet 12 is gradually absorbed by the front end due to the heat, which leads to insufficient preheating. As time goes by, the "effective preheating zone" in the heat storage chamber 1 will gradually shrink along the air flow direction and even disappear, which may eventually cause the heat storage chamber 1 to be unable to maintain the required temperature conditions. The stable operation of the heat storage chamber 1 depends on the uniform distribution of its internal temperature. If the "effective preheating zone" disappears, the temperature gradient in the heat storage chamber 1 will become unstable, resulting in a decrease in the operating efficiency of the exhaust gas chemical energy recovery system 100 or even an interruption of operation. Therefore, in this embodiment, a plurality of gas inlets 11 and gas outlets 12 are respectively provided at different positions on the outer surface of the heat storage chamber 1. At the same time, the exhaust gas chemical energy recovery system 100 is provided with a valve control component 13, which can be used to independently switch the above-mentioned multiple gas inlets 11 and multiple gas outlets 12. The operator can periodically switch the gas inlet 11 and the gas outlet 12 of the heat storage chamber 1 through the valve control component 13 according to the operating state of the heat storage chamber 1, such as temperature, pressure and other parameters, so that the exhaust gas airflow direction inside the heat storage chamber 1 can be switched regularly, effectively solving the problem of preheating area reduction caused by a single flow direction, ensuring uniform temperature distribution inside the entire heat storage chamber 1, thereby maintaining the stability of the operation of the exhaust gas chemical energy recovery system 100. Reference Figure 1 , by adjusting the valve control component 13, first open the first gas inlet 111 set on the lower side of the heat storage chamber 1 and the first gas outlet 121 set on the upper diagonal side thereof. After the exhaust gas enters the heat storage chamber 1 and oxidizes and releases heat therein for a fixed time, adjust the valve control component 13 to close the first gas inlet 111 and the first gas outlet 121, and then open the second gas inlet 112 and the second gas outlet 122 on the other side above and below the heat storage chamber 1 respectively. At this time, the direction of the exhaust gas flow in the heat storage chamber 1 changes, so that all parts of the heat storage chamber 1 can be heated by the heat released during the oxidation of the exhaust gas to maintain a uniform temperature distribution.

[0034] In this embodiment, the heat storage material used inside the heat storage chamber 1 is a metal oxide heat storage medium 3. The reason for choosing the metal oxide heat storage medium 3 is that, on the one hand, the metal oxide heat storage medium 3 can absorb heat by decomposition at high temperatures to achieve the effect of suppressing overheating, and can release heat by recombination at low temperatures to compensate for heat loss. Therefore, such "adaptive" characteristics enable the metal oxide heat storage medium 3 to suppress the temperature fluctuation inside the heat storage chamber 1, and then form a more stable reaction environment of dynamic thermal equilibrium inside the heat storage chamber 1, reducing the switching times of the flow direction of the exhausted air gas. On the other hand, the energy storage density of the metal oxide heat storage medium 3 is significantly better than that of traditional heat storage materials such as lava or ceramics, and its high thermal conductivity can significantly reduce convective or radiative heat loss, thereby maintaining a long energy storage time.

[0035] In addition, when the exhausted air gas enters the heat storage chamber 1 and starts the oxidation exothermic reaction, the metal oxide heat storage medium 3 starts the reduction reaction due to heat and stores the heat energy released by the exhausted air gas in the oxidation reaction in the metal oxide heat storage medium 3 by absorbing heat. At the same time, a large amount of O 2 . This newly generated O 2 can continue to participate in the oxidation reaction of the exhausted air gas to further promote the oxidation exothermic rate of the exhausted air gas. So far, the reduction reaction occurring in the metal oxide heat storage medium 3 and the oxidation reaction occurring in the gas mutually promote, and complete the energy transfer process of converting the chemical energy of the exhausted air gas into the heat energy and chemical energy of the metal oxide heat storage medium 3.

[0036] In this embodiment, the metal elements in the metal oxide heat storage medium 3 include at least one of copper and manganese. The copper / manganese metal oxide heat storage medium 3 has a high heat storage capacity and good thermal stability, and can absorb a large amount of heat in a high-temperature environment. And when the concentration of the exhausted air gas inside the heat storage chamber 1 is insufficient, the heat stored in the copper / manganese metal oxide heat storage medium 3 can be released to maintain the temperature of the heat storage chamber 1 or provide additional heat energy, significantly improving the oxidation exothermic efficiency of the exhausted air gas, while achieving efficient recovery and utilization of energy and reducing the environmental pollution caused by fossil energy.

[0037] As shown in the following chemical equation, the copper / manganese metal oxide heat storage medium 3 undergoes a reduction endothermic reaction in a high-temperature environment and releases a large amount of O 2 , and this part of O 2 can further promote the oxidation exothermic reaction of the exhausted air gas.

[0038]

[0039] In the above chemical equation, M represents metal elements such as Cu and Mn, O represents oxygen element, and △H represents the reaction enthalpy.

[0040] In addition, the copper / manganese metal oxide heat storage medium 3 can exhibit excellent cyclic stability in the redox reaction and can be reused multiple times without significantly reducing its performance.

[0041] In this embodiment, the metal oxide heat storage medium 3 is in the form of particles. On the one hand, because the metal oxide heat storage medium 3 particles have a high specific surface area, the contact area between the metal oxide heat storage medium 3 and the exhausted air gas can be significantly increased, thereby enhancing its reaction efficiency during the heat storage or heat release process and improving the heat transfer efficiency. On the other hand, the metal oxide heat storage medium 3 particles have good fluidity, which is convenient for filling and uniformly distributing in the heat storage chambers 1 designed in various ways or other heat storage devices, enabling it to achieve dynamic mixing with the exhausted air gas flow and improving the recovery efficiency of the chemical energy of the exhausted air gas. In addition, the metal oxide heat storage medium 3 particles have excellent properties such as high mechanical strength, melting point, and thermal stability, as well as its relatively mature manufacturing process, all of which greatly improve the use efficiency of the exhausted air gas chemical energy recovery system 100 and reduce the use cost of the system to a certain extent.

[0042] If it is necessary to further improve the energy recovery and transfer efficiency of the exhausted air gas chemical energy recovery system 100, it can be achieved by increasing the contact area between the metal oxide heat storage medium 3 particles and the exhausted air gas flow. In this embodiment, a packed bed 4 is also provided in the heat storage chamber 1. Refer to Figure 1 , the packed bed 4 is composed of multiple layers of independent bed bodies 41, dividing the interior of the heat storage chamber 1 into a multi-layer structure, and the metal oxide heat storage medium 3 particles are uniformly filled in each layer of the bed body 41. Each layer of the bed body 41 can be separated by a partition 42 or other support structures to ensure the uniform distribution of the exhausted air gas flow. In other embodiments, the height, number of layers, and arrangement direction of the bed body 41 of the packed bed 4 can be optimized according to the actual shape of the heat storage chamber 1 and the thermodynamic performance required by the exhausted air gas chemical energy recovery system 100, and no specific limitations are made here.

[0043] To enable the exhausted air gas to enter the interior of the heat storage chamber 1 with a stable concentration and flow rate and carry out the oxidation and heat release reaction, in this embodiment, the exhausted air gas chemical energy recovery system 100 further includes a buffer storage tank 5. The exhaust port of the buffer storage tank 5 is connected to the gas inlet 11 of the heat storage chamber 1, and is used for buffering and storing the exhausted air gas that will enter the heat storage chamber 1 for oxidation and heat release from the outside. After the exhausted air gas in the buffer storage tank 5 reaches the preset concentration and the preheater 2 heats the heat storage chamber 1 to the self-oxidation critical temperature of the exhausted air gas, the buffer storage tank 5 can be connected to the gas inlet 11 of the heat storage chamber 1 by adjusting the valve control assembly 13, so as to lead the exhausted air gas in the buffer storage tank 5 into the interior of the heat storage chamber 1 and start the oxidation and heat release reaction.

[0044] In this embodiment, in order to fully recover and utilize the thermal energy generated after the oxidation of the diluted wind gas, the diluted wind gas chemical energy recovery system 100 further includes an air heat exchange unit 6. The air heat exchange unit 6 includes heat exchange tubes (not shown in the figure), and the heat exchange tubes are arranged inside the heat storage cavity 1. The heat that is not completely absorbed by the metal oxide heat storage medium 3 during the oxidation of the diluted wind gas in the heat storage cavity 1 is used to heat the cold air in the heat exchange tubes, and then the heated hot air is used for heating or power generation. To further improve the heat exchange efficiency of the heat exchange tubes for the cold air, a compressor 61 is provided at the air inlet end of the air heat exchange unit 6 to increase the density of the cold air that is about to enter the heat exchange tubes, thereby increasing the air quality in the heat exchange tubes to transfer more heat released by the oxidation reaction of the diluted wind gas inside the heat storage cavity 1. Refer to Figure 1 , in this embodiment, a turbine 62 is provided at the hot air outlet end of the air heat exchange unit 6 to convert the thermal energy contained in the hot air after passing through the heat exchange tubes into mechanical energy.

[0045] When the diluted wind gas completes the exothermic oxidation reaction inside the heat storage cavity 1 and converts most of its chemical energy into the thermal energy and chemical energy of the metal oxide heat storage medium 3, and the thermal energy of the air in the heat exchange tubes, the remaining tail gas flow will be discharged from the gas outlet 12 of the heat storage cavity 1. Since the tail gas flow discharged from the inside of the heat storage cavity 1 still has a relatively high temperature, in this embodiment, the outer end of the gas outlet 12 of the heat storage cavity 1 faces the cold air inlet end in the air heat exchange unit 6, so as to utilize the remaining heat in the tail gas discharged from the inside of the heat storage cavity 1 to preheat the cold air that has not yet been heat-exchanged, thereby improving the chemical energy recovery efficiency of the diluted wind gas chemical energy recovery system 100 and reducing losses.

[0046] <Second Embodiment>

[0047] This embodiment provides a method for recovering the chemical energy of diluted wind gas for the above-mentioned diluted wind gas chemical energy recovery system 100, refer to Figure 2 , and this method for recovering the chemical energy of diluted wind gas includes the following execution steps: a preheating step S1, an exothermic oxidation step S2, and a heat storage step S3.

[0048] The execution steps in the method for recovering the chemical energy of diluted wind gas will be described below.

[0049] <Preheating Step S1>

[0050] In this embodiment, before the diluted wind gas is introduced into the heat storage cavity 1, it is necessary to heat the internal temperature of the heat storage cavity 1 to the self-oxidation temperature of the diluted wind gas through a preheater 2, so as to provide the necessary thermodynamic conditions for the "flameless" oxidation reaction of the diluted wind gas that will enter the heat storage cavity 1 subsequently.

[0051] <Exothermic Oxidation Step S2>

[0052] After the preheating step S1 is completed, adjust the valve control assembly 13 to open one of the gas inlets 11 and the gas outlet 12 of the heat storage chamber 1. Then, introduce the exhausted mine gas collected externally into the heat storage chamber 1 through the gas inlet 11 and start the "flameless" oxidation reaction at the preheating temperature, converting the chemical energy of the exhausted mine gas into heat energy and releasing it into the heat storage chamber 1.

[0053] <Heat storage step S3>

[0054] While the oxidation exothermic step S2 is proceeding, due to the heating and temperature rise of the preheater 2 and the oxidation exotherm of the exhausted mine gas inside the heat storage chamber 1, the metal oxide heat storage medium 3 inside the heat storage chamber 1 begins to undergo a reduction endothermic reaction, thereby converting the chemical energy of the exhausted mine gas in the heat storage chamber 1 into the heat energy and chemical energy of the metal oxide heat storage medium 3 particles through oxidation exotherm. At the same time, a large amount of oxygen is released during the reduction endothermic reaction of the metal oxide heat storage medium 3, further accelerating the oxidation exothermic reaction rate of the exhausted mine gas inside the heat storage chamber 1. Thus, the reduction reaction occurring in the metal oxide heat storage medium 3 and the oxidation reaction occurring in the exhausted mine gas promote each other, and the recovery and storage of the chemical energy of the exhausted mine gas are completed.

[0055] <The third embodiment>

[0056] In another method for recovering the chemical energy of exhausted mine gas provided by the present invention, refer to Figure 3 , in addition to the steps of the second embodiment of the present invention, the execution steps of the method for recovering the chemical energy of exhausted mine gas further include: a buffering step S4, an exhausted mine gas flow direction switching step S5, a heat exchange step S6, and an exhaust gas heat recovery step S7.

[0057] The following describes the execution steps in this embodiment.

[0058] <Buffering step S4>

[0059] With the start of the preheating step S1 of the exhausted mine gas chemical energy recovery system 100, the continuously produced exhausted mine gas externally will first be discharged into the buffer storage tank 5 for buffering storage. After the preheating step S1 ends, adjust the valve control assembly 13 to open one of the gas inlets 11 and the gas outlet 12 of the heat storage chamber 1, so that the exhausted mine gas exhaust port of the buffer storage tank 5 is communicated with the gas inlet 11 of the heat storage chamber 1, and then the exhausted mine gas in the buffer storage tank 5 is led to the inside of the heat storage chamber 1 at a stable concentration and flow rate and the oxidation exothermic step S2 is started.

[0060] <Exhausted mine gas flow direction switching step S5>

[0061] With the continuous progress of the oxidation exothermic step S2 of the low-concentration methane chemical energy recovery system 100, it is necessary to adjust the valve control assembly 13 so that the switches of different methane inlets 11 and methane outlets 12 in the heat storage chamber 1 are periodically switched, thereby periodically changing the gas flow direction of the low-concentration methane inside the heat storage chamber 1, and then effectively solving the problem of the reduction of the preheating zone in the heat storage chamber 1 caused by the single gas flow direction of the low-concentration methane, ensuring the uniform temperature distribution inside the heat storage chamber 1, and finally maintaining the stability of the operation of the low-concentration methane chemical energy recovery system 100.

[0062] <Heat exchange step S6>

[0063] During the progress of the oxidation exothermic step S2 and the heat storage step S3 of the second embodiment, in order to enable the heat energy generated in the oxidation reaction of the low-concentration methane to be fully recovered and utilized, and further improve the energy recovery efficiency. In this embodiment, by setting the air heat exchange unit 6 in the low-concentration methane chemical energy recovery system 100, cold air is introduced into the heat exchange tubes arranged inside the heat storage chamber 1, and the cold air in the heat exchange tubes is heated by the heat stored in the metal oxide heat storage medium 3, and then the heated hot air is used for heating or power generation, etc.

[0064] <Tail gas heat recovery step S7>

[0065] When the low-concentration methane passes through the above steps, the tail gas after oxidation will be discharged to the outside of the heat storage chamber 1 through the methane outlet 12. Since in the heat storage step S3 and the heat exchange step S6, the heat energy released by the low-concentration methane in the heat storage chamber 1 cannot be completely recovered by the metal oxide heat storage medium 3 and the air heat exchange unit 6, the tail gas generated after the oxidation reaction of the low-concentration methane still has a relatively high temperature when discharged to the outside of the heat storage chamber 1. Therefore, in this embodiment, the outer end of the methane outlet 12 of the heat storage chamber 1 faces the cold air inlet end in the air heat exchange unit 6, so as to utilize the remaining heat in the tail gas discharged from the inside of the heat storage chamber 1 to preheat the cold air that has not been heat exchanged, thereby improving the chemical energy recovery efficiency of the low-concentration methane chemical energy recovery system 100 and reducing loss.

[0066] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A system for recovering chemical energy from exhaust gas, characterized in that: include: A heat storage chamber, wherein the heat storage chamber is provided with a plurality of gas inlets and a plurality of gas outlets; A preheater connected to the heat storage chamber, heating the heat storage chamber to the self-oxidation temperature of the exhaust gas before the exhaust gas enters the heat storage chamber; The metal oxide heat storage medium is arranged in the heat storage chamber and is used to recover and store the chemical energy of the exhaust gas.

2. The exhaust gas chemical energy recovery system according to claim 1, characterized in that: Also includes: The valve control component can independently switch the multiple gas inlets and the multiple gas outlets.

3. The exhaust gas chemical energy recovery system according to claim 1, characterized in that: The metal element in the metal oxide heat storage medium includes at least one of copper and manganese, and the metal oxide heat storage medium is in the form of particles.

4. The exhaust gas chemical energy recovery system according to claim 1, characterized in that: Also includes: A stacked bed is arranged inside the heat storage chamber and between the gas inlet and the gas outlet; The stacked bed comprises a multi-layer bed body, which divides the interior of the heat storage chamber into a multi-layer structure, and the metal oxide heat storage medium is distributed in the bed body.

5. The exhaust gas chemical energy recovery system according to claim 1, characterized in that: Also includes: A buffer storage tank, the exhaust port of which is connected to the gas inlet of the heat storage chamber, is used for buffering and storing the external exhaust gas that is about to enter the heat storage chamber for oxidation.

6. The exhaust gas chemical energy recovery system according to claim 1, characterized in that: Also includes: The air heat exchange unit comprises a heat exchange tube, and the heat exchange tube is arranged inside the heat storage chamber.

7. The exhaust gas chemical energy recovery system according to claim 6, characterized in that: The air heat exchange unit also includes a compressor and a turbine. The compressor compresses the cold air that is about to enter the heat storage chamber for heat exchange, and the turbine converts the thermal energy contained in the hot air after heat exchange into mechanical energy.

8. The exhaust gas chemical energy recovery system according to claim 6, characterized in that: The outer end of the gas outlet of the heat storage chamber faces the cold air inlet end of the air heat exchange unit, and the tail gas flow of the exhaust gas is used to preheat the cold air that is about to enter the heat exchange tube for heat exchange.

9. A method for recovering chemical energy of exhaust gas, used in the exhaust gas chemical energy recovery system as claimed in any one of claims 1 to 8, characterized in that: The following steps are involved: A preheating step, before the exhaust gas is introduced into the heat storage chamber, heating the heat storage chamber to the self-oxidation temperature of the exhaust gas by the preheater; Oxidation heat release step: adjusting the valve control component to allow the exhaust gas to enter the heat storage chamber through the gas inlet and start oxidation heat release; Heat storage step: the metal oxide heat storage medium in the heat storage chamber undergoes a reduction endothermic reaction and releases oxygen after being heated.

10. The method for recovering chemical energy from exhaust gas according to claim 9, characterized in that: Also includes: Buffering step: before the preheating step is completed, the exhaust gas to be subjected to the oxidation exothermic step is introduced into the buffer storage tank; The step of switching the flow direction of the exhaust gas: adjusting the valve control component to periodically switch the gas inlet and the gas outlet of the heat storage chamber, thereby changing the flow direction of the exhaust gas in the heat storage chamber; Heat exchange step: passing cold air into the heat exchange tube in the heat storage chamber through an air heat exchange unit, further recovering the heat energy released by the exhaust gas in the oxidation heat release step and converting it into air heat energy in the heat exchange tube; Tail gas heat recovery step: after the exhaust gas of the exhaust gas of the airless gas after completing the oxidation heat release step in the heat storage chamber is discharged through the gas outlet, the exhaust gas flow is guided to the cold air inlet end of the air heat exchange unit.

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