Ventilation air methane thickening and concentration stabilizing system and method based on temperature distributed regulation and control

Abstract

The invention discloses a ventilation air methane thickening and concentration stabilizing system and method based on temperature distributed regulation and control. The system integrates a purification and energy integration unit, a concentration allocation unit and a solvent regeneration unit. The purification unit is used for extracting concentrated methane through absorption-desorption circulation, the core of the purification unit is that a closed heat energy circulation loop is arranged, waste heat generated by compressing ventilation air methane is recycled to be used for heating and desorbing rich liquor, meanwhile, cold energy is used for cooling and circulating barren liquor, and efficient self-utilization of energy is achieved. And the concentration blending unit outputs mixed gas with stable and adjustable concentration through on-line monitoring and mixing of the concentrated gas and the diluted tail gas. And the solvent regeneration unit continuously purifies and absorbs the solvent. The invention also discloses preferable structures such as a tandem type multi-tank absorption tower and the like. The system can efficiently treat ventilation air methane, and is stable in output concentration, low in energy consumption, reliable in operation and suitable for coal mine field application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coal mine gas resource utilization and energy saving and emission reduction, and particularly relates to a system and method for purification, concentration regulation and energy recovery of coal mine ventilation air methane (VAM) with a methane concentration lower than 1%. BACKGROUND

[0002] Coal mine VAM is the main mixed gas containing nitrogen, oxygen and trace methane continuously discharged by the mine ventilation system. The methane volume fraction is usually lower than 0.3%. Although the concentration is extremely low, the total amount is huge. Direct emission not only causes serious greenhouse effect, but also is a waste of energy. In order to realize its resource utilization (such as for heat storage oxidation power generation or heating), the methane concentration needs to be increased and stabilized in a usable range (for example, more than 1%).

[0003] At present, mixing VAM with high concentration of extracted gas is the main means to realize concentration increase on site, but this method highly depends on external gas source, has problems such as large concentration fluctuation, high safety risk and limited application range. Other separation technologies, such as deep cooling method and pressure swing adsorption method, generally face challenges such as high energy consumption, large equipment or complex process when dealing with such ultra-low concentration and large flow gas. The economic efficiency and practicability are insufficient, and it is difficult to realize large-scale industrial application.

[0004] As a continuous operation potential gas separation approach, solvent absorption method still has significant systematic problems when applied to VAM treatment. First, the traditional absorption-desorption process usually needs large solvent circulation amount or extremely high gas-liquid contact efficiency when dealing with ultra-low concentration methane due to small driving force, resulting in huge equipment investment and operation energy consumption. Second, a large amount of compression heat generated by the process will cause serious energy loss if not effectively recovered and utilized, further deteriorating the system energy efficiency. Third, the concentration of high concentration gas obtained by desorption is affected by factors such as inlet gas and operating conditions, and there is fluctuation. The traditional process route lacks active and stable regulation module for product gas concentration, and it is difficult to meet the strict requirements of the downstream utilization device for the stability of the inlet gas concentration. In addition, in long-term operation, the absorption solvent is easy to be degraded in performance due to carrying water and impurities, affecting the stability of long-term operation of the system. Therefore, developing a VAM treatment system that can integrate efficient mass transfer, energy cascade recovery, accurate regulation of product concentration and long-term maintenance of solvent is the key to realizing its economic and stable operation resource utilization, and is also the technical problem to be solved in the current field. SUMMARY

[0005] The present application aims to overcome the deficiencies of the prior art, and provides an integrated flue gas enrichment and concentration system and method. The system can not only efficiently purify ultra-low concentration flue gas, but also accurately and stably regulate the concentration of the purified gas to meet the requirements of the downstream utilization device. At the same time, through the innovative energy integration design, the internal waste heat of the system is recovered, the operation energy consumption is reduced, and the long-term stable operation of the system is ensured through solvent purification.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions: In a first aspect, a flue gas enrichment and concentration system based on temperature distribution regulation is provided.

[0007] The system mainly includes three core units working cooperatively: a purification and energy integration unit, a concentration regulation unit and a solvent regeneration unit.

[0008] Purification and energy integration unit

[0009] The unit is the core of the present application, responsible for capturing and enriching methane in flue gas, and realizing efficient recovery and utilization of internal energy of the system.

[0010] Basic process and components: along the flue gas flow direction, the unit includes a flue gas filter for removing solid particles, a compressor set for improving gas pressure, an intercooler for inter-stage cooling, a high-pressure gas storage tank for storing stable pressure, and the core absorption tower and desorption tower. The absorption tower is used for making the pretreated flue gas and the absorption solvent counterflow contact, selectively absorbing methane to form a rich liquid; the desorption tower is used for releasing high-concentration methane gas from the rich liquid under reduced pressure and heating conditions, and regenerating into a lean liquid.

[0011] Energy integration core-closed heat energy circulation loop: the key innovation of the unit is to set a closed heat energy circulation loop composed of heat transfer fluid (preferably high specific heat capacity silicon oil). The loop mainly includes a cold fluid tank, a hot fluid tank and corresponding connecting pipelines and heat exchangers. Specifically: Heat recovery: in the compression process, the compression heat generated by the gas is absorbed by the heat transfer fluid flowing through the cold side of the intercooler, and the high-temperature fluid after absorbing heat is collected and stored in the hot fluid tank.

[0012] Heat utilization: the high-temperature fluid stored in the hot fluid tank is pumped to the hot side of the heating heat exchanger to heat the rich liquid about to enter the desorption tower, thereby providing the heat energy required for desorption and improving the desorption efficiency. The cold fluid returns to the cold fluid tank after releasing heat.

[0013] Cold energy utilization: The low-temperature fluid in the cold fluid tank is pumped to the cold side of the cooling heat exchanger to cool the lean liquid flowing out of the desorption tower, i.e., returning to the absorption tower, thereby reducing the temperature of the lean liquid and improving its absorption capacity for methane in the absorption tower. The fluid that has been warmed after absorbing cold energy flows to the hot fluid tank.

[0014] Through this circuit, the system realizes the recovery of waste heat from the compression process and precisely uses it to promote the desorption process, while the cold energy is used to strengthen the absorption process, forming a highly efficient energy self-balancing system.

[0015] Concentration adjustment unit

[0016] This unit is used to ensure the stability and adjustability of the output gas concentration to meet the specific needs of the utilization equipment in the back end.

[0017] Composition and connection: This unit mainly includes a gas mixer and a concentration distributor. Its input end receives two gas streams from the purification and energy integration unit: one is high-concentration methane gas from the top of the desorption tower, and the other is part of the unabsorbed tail gas (as dilution gas) separated from the exhaust gas at the top of the absorption tower.

[0018] Regulation means: Concentration monitors (such as methane gas analyzers) and flow controllers (such as mass flow controllers) are respectively arranged on the high-concentration methane gas flow path and the partial tail gas flow path. By real-time monitoring of the concentration and accurate control of the mixing ratio of the two gases, a mixed gas with any desired target concentration and high stability can be produced in the gas mixer.

[0019] Distribution output: The stable concentration mixed gas produced enters the concentration distributor, which can distribute and deliver the gas to each utilization point according to the different loads or concentration requirements of multiple regenerative oxidation devices in the back end.

[0020] Solvent regeneration unit

[0021] This unit is used to maintain the long-term and efficient performance of the absorption solvent, ensuring the continuous and stable operation of the main system.

[0022] Process and components: This unit processes a part of the lean liquid (as a purification diversion) drawn from the bottom of the desorption tower. This part of the lean liquid is pumped into a liquid-liquid-solid three-phase separation cyclone in sequence, where solid particles are first filtered out, and then most of the water mixed in the solvent is preliminarily separated by centrifugal force. To further reduce the water content in the solvent, the separated water-containing solvent can enter an extraction tank for deep dehydration. Finally, the pure regenerated solvent is collected in the absorption solvent storage tank and returns to the main circulation and combines with the main lean liquid stream.

[0023] Preferably, to further enhance the mass transfer efficiency and optimize the equipment volume, the absorption tower can adopt a series multi-tank structure. The structure includes an external tower shell, at least two independent absorption tank units are arranged side by side in the internal tower shell. Each tank unit is provided with liquid flow equalizer, absorption packing bin and other internal components. The gas passages of each tank unit are connected in series through pipelines, so that the gas passes through all the tank units in turn, prolonging the contact path; and the liquid inlets of each tank unit are connected in parallel to the total liquid inlet pipe, ensuring the uniformity of liquid distribution. The desorption tower can also adopt a similar internal component design. A converging-diverging nozzle can also be arranged below the liquid flow equalizer to reduce the liquid velocity, increase the pressure, and further optimize the mass transfer conditions.

[0024] In a second aspect, a method for enriching and stabilizing the concentration of ventilation air methane based on the above-mentioned system is provided.

[0025] The method comprises the following steps: Step one, pretreatment: filtering and dust removing the ventilation air methane discharged from the coal mine, then compressing to increase the partial pressure, and cooling between compression stages; Step two, absorption and enrichment: the pretreated ventilation air methane is introduced from the bottom of the absorption tower and contacted with the low-temperature lean liquid absorption solvent sprayed from the top of the tower in counterflow. The lean liquid selectively absorbs methane to form a rich liquid, and the tail gas not absorbed is discharged from the top of the tower; Step three, desorption and regeneration: the rich liquid is pressurized and heated using recovered heat (through a closed heat energy circulation loop), and then sent to the top of the desorption tower for decompression desorption, thereby releasing high-concentration methane gas; Step four, solvent circulation and cooling: the desorbed lean liquid is divided into two paths. The main path lean liquid is pumped and cooled using recovered cold energy (through a closed heat energy circulation loop), and then returned to the top of the absorption tower for circulation. The branch path lean liquid enters a purification process, in which the branch path lean liquid is sequentially subjected to liquid-solid separation, liquid-liquid centrifugal separation and extraction dehydration to remove the water and solid impurities accumulated in the circulation, and the recovered pure solvent is returned to the main solvent circulation; Step five, concentration adjustment: the high-concentration methane gas obtained in step three is accurately mixed with part of the unabsorbed tail gas branched out in step two according to the online monitored concentration by adjusting the flow rate, to obtain mixed gas with stable concentration at a set value; Step six, energy integration: through the closed circulation of the heat exchange fluid, the waste heat generated in the compression process in step one is recovered and transferred to the rich liquid in step three for heating, and at the same time, the cold energy carried by the released heat fluid is transferred to the lean liquid in step four for cooling, realizing internal circulation and efficient utilization of system heat.

[0026] Compared with the prior art, the beneficial technical effects of the present application are: Integrated efficient concentration and concentration stabilization: The system integrates physical purification, concentration accurate regulation and energy management, and for the first time provides a complete solution from "unusable" to "stable and usable" for ultra-low concentration exhaust gas, filling the technical gap in this field.

[0027] Significant improvement in energy efficiency: The innovative closed heat energy circulation loop converts the main energy consumption point of compression heat into driving force to promote desorption, while recovering cold energy to strengthen absorption, greatly reducing the system's demand for external energy and achieving excellent operation economy.

[0028] Flexible and stable output concentration: Through online feedback and flow accurate control, stable gas of any required concentration can be produced, completely solving the problem of large concentration fluctuation in traditional blending method, and greatly ensuring the safe, efficient and stable operation of the rear-end utilization device (such as RTO).

[0029] Long-term reliable operation of the system: The independent solvent regeneration module continuously removes moisture and impurities, effectively maintaining the selectivity and absorption capacity of the absorption solvent, avoiding the decline of system efficiency caused by the performance degradation of the solvent, and ensuring the long-term reliability and availability of the device.

[0030] Compact structure, strong adaptability: The design of series connection type tower body improves the processing efficiency in limited space. The system has high modularity and can be flexibly configured according to the exhaust gas parameters of different mines, with strong adaptability and generalization. BRIEF DESCRIPTION OF DRAWINGS

[0031] The application will be further described below in conjunction with the drawings.

[0032] Figure 1 The structure diagram of the exhaust gas concentration and stabilization system based on temperature distribution regulation of the application; Figure 2 The shell structure diagram of the absorption tower of the application; Figure 3 The tank unit structure diagram of the absorption tower of the application; Figure 4 The internal structure diagram of the tank unit in the absorption tower of the application; Figure 5 The internal structure diagram of the desorption tower of the application.

[0033] Explanation of reference numerals: 1, exhaust gas filter; 2, first-stage exhaust gas compressor; 3, first-stage intercooler; 4, second-stage exhaust gas compressor; 5, second-stage intercooler; 6, high-pressure gas tank; 7, first methane gas analyzer; 8, first mass flow controller; 9, absorption tower; 10, rich-liquid solution pump; 11, temperature-increasing heat exchanger; 12, desorption tower; 13, lean-liquid solution pump; 14, temperature-decreasing heat exchanger; 15, cold fluid tank; 16, hot fluid tank; 17. Second methane gas analyzer; 18. Second mass flow controller; 19. Flue gas mixer; 20. Concentration distributor; 21. Third mass flow controller; 22. Third methane gas analyzer; 23. Impurity-containing liquid pump; 24. Liquid-liquid-solid three-phase separation cyclone; 25. Extraction tank; 26. Absorption solvent storage tank. DETAILED DESCRIPTION

[0034] In order to make the technical problems to be solved by the present application, technical solutions and beneficial effects clearer, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and not used to limit the present application.

[0035] Example 1: Overall structure and working process of the system

[0036] Reference Figure 1 The present embodiment describes a flue gas enrichment and concentration stabilization system based on temperature distribution regulation in detail.

[0037] 1. Specific structure of purification and energy integration unit: The flue gas inlet is connected to a flue gas filter 1, in this example, a cyclone separator or a bag filter, the filter material is polyester or needle-punched felt, and the filter core is activated carbon or porous aluminum oxide, etc., which is used to remove dust with a particle size greater than a threshold value.

[0038] The flue gas filter 1 outlet is connected to the first flue gas compressor 2, wherein the first flue gas compressor 2 adopts an oil-free explosion-proof compressor, and the gas pressure is increased from normal pressure to a first preset value through equal ratio compression. The first flue gas compressor 2 outlet is connected to the hot side inlet of the first intercooler 3.

[0039] The first intercooler 3 hot side outlet is connected to the second flue gas compressor 4, and the second flue gas compressor 4 also adopts an oil-free explosion-proof compressor to further increase the pressure to a second preset value. The second flue gas compressor 4 outlet is connected to the hot side inlet of the second intercooler 5.

[0040] The second intercooler 5 hot side outlet is connected to the high-pressure gas storage tank 6 for buffering and stabilizing the gas flow.

[0041] The high-pressure gas storage tank 6 outlet is connected to the first methane gas analyzer 7 and the first mass flow controller 8 in turn, and then connected to the flue gas inlet at the lower end of the absorption tower 9.

[0042] The absorption tower 9 is a vertical packed tower, which is provided with a lean liquid inlet, a waste gas outlet and a concentration balance tail gas outlet at the top, and a rich liquid outlet at the bottom. The tower is filled with stainless steel Pall ring packing.

[0043] The rich liquid outlet of the absorption tower 9 is connected to the inlet of the rich liquid solution pump 10, and the outlet of the rich liquid solution pump 10 is connected to the cold side (i.e. the rich liquid side) inlet of the warming heat exchanger 11.

[0044] The cold side outlet of the warming heat exchanger 11 is connected to the rich liquid inlet at the top of the desorption tower 12.

[0045] The desorption tower 12 is also a vertical packed tower, and is provided with a high-concentration exhaust gas outlet at the top and a first lean liquid outlet (main path) and a second lean liquid outlet (purification branch) at the bottom.

[0046] The first lean liquid outlet of the desorption tower 12 is connected to the inlet of the lean liquid solution pump 13, and the outlet of the lean liquid solution pump 13 is connected to the hot side (i.e. the lean liquid side) inlet of the cooling heat exchanger 14. The hot side outlet of the cooling heat exchanger 14 is connected to the lean liquid inlet at the top of the absorption tower 9.

[0047] The absorption solvent is selected from a special solvent with high selectivity and low volatility for methane, including but not limited to organic liquid and inorganic liquid.

[0048] The specific connection of the closed thermal energy circulation loop is as follows: The outlet of the cold fluid tank 15 (storing a high-specific-heat heat exchange fluid such as silicone oil) is divided into three paths: the first path is adjusted by a valve and then enters the cold side inlet of the first-stage intercooler 3; the second path is adjusted by a valve and then enters the cold side inlet of the second-stage intercooler 5; and the third path enters the cold side inlet of the cooling heat exchanger 14.

[0049] The cold side outlets of the first-stage intercooler 3, the second-stage intercooler 5 and the cooling heat exchanger 14 are connected in parallel and then connected to the inlet of the hot fluid tank 16.

[0050] The outlet of the hot fluid tank (storing a high-specific-heat heat exchange fluid such as silicone oil) is connected to the hot side (i.e. the silicone oil side) inlet of the warming heat exchanger 11.

[0051] The hot side outlet of the warming heat exchanger 11 is connected to the inlet of the cold fluid tank 15.

[0052] 2. Specific structure of the concentration adjustment unit: The high-concentration exhaust gas outlet at the top of the desorption tower 12 is connected to the first inlet of the exhaust gas mixer 19 after being sequentially connected to the second methane gas analyzer 17 and the second mass flow controller 18.

[0053] The concentration balance tail gas outlet at the top of the absorption tower 9 is connected to the second inlet of the exhaust gas mixer 19 after being sequentially connected to the third methane gas analyzer 22 and the third mass flow controller 21.

[0054] The outlet of the exhaust gas mixer 19 is connected to the inlet of the concentration distributor 20. The concentration distributor 20 is provided with multiple outlet valves and can be connected to different exhaust gas regenerative oxidation (RTO) devices.

[0055] 3. The specific configuration of the solvent regeneration unit: The second lean liquid outlet (purification branch) of the desorption tower 12 is connected to the inlet of the impurity-containing liquid pump 23.

[0056] The outlet of the impurity-containing liquid pump 23 is connected to the impurity-containing solvent inlet of the liquid-liquid-solid three-phase separation cyclone 24. The cyclone is internally integrated with a metal filter screen (for trapping solid particles) and a cyclone separation chamber (for separating the solvent from water based on density difference, in this embodiment, the solvent has a higher density than water).

[0057] The absorption solvent outlet at the lower end of the liquid-liquid-solid three-phase separation cyclone 24 is connected to the absorption solvent storage tank 26. The water outlet (containing a small amount of solvent) at the upper end of the liquid-liquid-solid three-phase separation cyclone 24 is connected to the liquid inlet of the extraction tank 25.

[0058] The extraction tank 25 is provided with a drain valve at the lower part and an absorption solvent recovery outlet at the upper part, which is also connected to the absorption solvent storage tank 26.

[0059] The outlet of the absorption solvent storage tank 26 is connected by a pipeline to the main pipeline before the inlet of the lean liquid solution pump 13, so that the purified solvent is merged into the main circulation.

[0060] Brief description of the working process: The methane concentration of the exhaust air gas is about 0.25%. After dust removal and two-stage compression cooling to 0.8 MPa, it enters the absorption tower 9. In the tower, it is countercurrently contacted with the downward flow of about 30°C lean liquid, and the methane is absorbed, and the rich liquid is discharged from the bottom of the tower. The rich liquid is pumped and heated to about 60°C in the warming heat exchanger 11 by 80°C silicone oil, and then enters the desorption tower 12. In the desorption tower 12, high-concentration methane (about 1.4%) is released. Most of the lean liquid after desorption (about 80%) is cooled by the 25°C silicone oil in the cooling heat exchanger 14 and then returned to the absorption tower 9; a small part (about 20%) enters the solvent regeneration unit, and after cyclone separation and extraction dehydration, the recovered pure solvent is returned to the system.

[0061] The high-concentration gas obtained by desorption is mixed with part of the lean methane tail gas (about 0.08%) discharged from the absorption tower 9 in the exhaust air gas mixer 19 according to online analysis data, and the mass flow controller is adjusted to mix the mixed gas with different concentrations in different proportions, and the mixed gas with the best concentration is selected by the concentration distributor 20 according to the required temperature of the regenerative oxidation device and is distributed to the RTO device.

[0062] In the whole process, the heat generated by compression is absorbed by silicone oil and stored in the hot fluid tank 16 for heating the rich liquid; the cooled rich liquid and silicone oil after absorbing the compression heat are stored in the cold fluid tank 15 for cooling the lean liquid. The system realizes energy self-balancing.

[0063] Example 2: Series-connected tower structure

[0064] This embodiment focuses on describing a preferred internal structure of the absorption tower 9 and the desorption tower 12 in the system.

[0065] like Figure 2 and Figure 3 As shown, the absorption tower 9 in this embodiment adopts a series-connected multi-tank structure. Its exterior is a cylindrical tower shell, and multiple absorption tank units with identical structures are fixed side by side and connected in series inside the tower shell. The top of the tower shell is provided with a main gas outlet pipe and a main lean liquid inlet pipe, and the bottom is provided with a main gas inlet pipe and a main rich liquid outlet pipe.

[0066] like Figure 4 As shown, the internal structure of a single absorption tank unit, from top to bottom, includes: Trough-type liquid distributor: Connects to the inlet pipe to evenly distribute the liquid across the tower cross section.

[0067] Diverging nozzle: Located below the trough-type liquid distributor, it slows down and pressurizes the liquid flow.

[0068] Absorption packing chamber: It is filled with stainless steel Pall ring packing, and the bottom of the packing is supported by a packing support grid, providing a huge surface area for gas-liquid mass transfer.

[0069] Liquid collector (rich liquid tank): Located at the bottom of the packing chamber, it collects the flowing rich liquid.

[0070] The top of the tank is equipped with a wire mesh demister (droplet collector), and the bottom is equipped with a gas distributor.

[0071] Taking three tank units as an example: the gas channels of the three tank units are connected in series: the gas inlet at the bottom of the first tank is connected to the main gas inlet pipe of the tower shell, and its top gas outlet is connected to the gas inlet at the bottom of the second tank via a connecting pipe; similarly, the top gas outlet of the second tank is connected to the bottom gas inlet of the third tank; the top gas outlet of the third tank is connected to the main gas outlet pipe of the tower shell. The liquid inlets of the three tank units are connected in parallel: all are connected to the main lean liquid inlet pipe at the top of the tower shell via branch pipes. This structure increases the path length of the gas flow by three times, significantly improving the methane recovery rate, and also requires a small footprint.

[0072] like Figure 5 As shown, the desorption tower 12 is a single-tank structure, but its internal components are similar to those of the absorption tank unit, including a liquid equalizer, a diffuser nozzle, a packing chamber, and a liquid collector. An exhaust pipe and exhaust valve are located at the top of the tower, and two liquid outlets are located at the bottom, corresponding to the main lean solution and the lean solution in the branch containing impurities, respectively.

[0073] Applying the tower structure of Example 2 to the system of Example 1 can further improve the mass transfer efficiency and processing capacity of the system.

[0074] Embodiment 3: The present embodiment provides a method for increasing and stabilizing the concentration of ventilation gas based on the above-mentioned system.

[0075] The method comprises the following steps: Step one, pretreatment: filtering and dust removing the ventilation gas discharged from the coal mine, then compressing to increase the partial pressure, and cooling between compression stages; Step two, absorption and concentration: the pretreated ventilation gas is introduced from the bottom of the absorption tower 9 and contacted with the low-temperature lean liquid absorption solvent sprayed from the top of the tower in countercurrent. The lean liquid selectively absorbs methane to form a rich liquid, and the tail gas not absorbed is discharged from the top of the tower; Step three, desorption and regeneration: the rich liquid is pressurized and heated using recovered heat (through a closed heat energy circulation loop), and then sent to the top of the desorption tower 12 for decompression desorption, thereby releasing high-concentration methane gas; Step four, solvent circulation and cooling: the desorbed lean liquid is divided into two paths. The main path lean liquid is pumped and cooled using recovered cold energy (through a closed heat energy circulation loop), and then returned to the top of the absorption tower 9 for circulation. The branch path lean liquid enters the purification process, and the branch path lean liquid is sequentially subjected to liquid-solid separation, liquid-liquid centrifugal separation and extraction dewatering to remove the water and solid impurities accumulated in the circulation, and the recovered pure solvent is returned to the main solvent circulation; Step five, concentration adjustment: the high-concentration methane gas obtained in step three is accurately mixed with part of the unabsorbed tail gas branched out in step two according to the online monitored concentration by adjusting the flow rate, to obtain mixed gas with stable concentration at a set value; Step six, energy integration: through the heat exchange fluid of the closed cycle, the waste heat generated in the compression process in step one is recovered and transferred to the rich liquid in step three for heating, and at the same time, the cold energy carried by the released heat fluid is transferred to the lean liquid in step four for cooling, realizing internal circulation and efficient utilization of system heat.

[0076] The system and method of the present application successfully realize efficient, stable and energy-saving resource utilization of ultra-low concentration ventilation gas through the above-mentioned modular and integrated design.

[0077] It should be noted that, in this document, relational terms such as first and second and the like can merely be used to distinguish one entity or action from another, without necessarily requiring or implying that there is any such actual relationship or order between or among the entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0078] The above described embodiments are only to illustrate the preferred modes of the present application, and are not intended to limit the scope of the present application. Any modification and improvement made by those skilled in the art to the technical solutions of the present application without departing from the design spirit of the present application shall fall within the protection scope of the present application.

Claims

1. A system for enriching and stabilizing exhaust gas based on distributed temperature control, characterized in that, include: The purification and energy integration unit is used to selectively absorb and desorb methane from the input exhaust gas and obtain high-concentration methane gas. The concentration adjustment unit is used to receive high-concentration methane gas and part of unabsorbed tail gas output from the purification and energy integration unit, and mix them in a set ratio to output a mixed gas with a stable concentration. The solvent regeneration unit is used to remove water and impurities from the circulating absorption solvent in the purification and energy integration unit. The purification and energy integration unit includes: An absorption tower is used to bring exhaust gas into contact with an absorption solvent to absorb methane. A desorption tower is used to desorb high-concentration methane gas from a rich liquid that has absorbed methane. A closed-loop thermal energy circulation loop, consisting of a circulating heat exchange fluid, is used to transfer the heat generated during the compression of the exhaust gas to the rich liquid before the inlet of the desorption tower, and to transfer the cold energy to the lean liquid returning to the absorption tower.

2. The exhaust gas enrichment and stabilization system based on temperature distributed control according to claim 1, characterized in that, The purification and energy integration unit also includes a filter and at least one stage of compression and cooling mechanism arranged sequentially along the exhaust gas flow direction; the closed thermal energy circulation loop includes a cold fluid tank, a hot fluid tank and connecting pipelines; the heat generated by the compression and cooling mechanism is stored in the hot fluid tank through a heat exchange fluid and provided to the rich liquid via a heating heat exchanger; the heat exchange fluid that provides cooling to the lean liquid comes from the cold fluid tank and is stored in the hot fluid tank after exchanging heat with the lean liquid via a cooling heat exchanger.

3. The exhaust gas enrichment and stabilization system based on distributed temperature control according to claim 2, characterized in that, The concentration adjustment unit includes a gas mixer, and a concentration monitor and a flow controller respectively located in the high-concentration methane gas flow path and the partially unabsorbed tail gas flow path; the outlet of the gas mixer is connected to a concentration distributor.

4. The exhaust gas enrichment and stabilization system based on distributed temperature control according to claim 1 or 2, characterized in that, The solvent regeneration unit includes a liquid-liquid-solid three-phase separation hydrocyclone and an extraction tank connected in sequence, used to remove water and solid impurities from the absorbent solvent. The purified solvent is returned to the main solvent circulation loop of the purification and energy integration unit.

5. The exhaust gas enrichment and stabilization system based on distributed temperature control according to claim 2, characterized in that, The absorption tower is a series-connected multi-tank structure, which includes an outer tower shell and at least two absorption tank units arranged side by side inside the shell. The gas channels of each absorption tank unit are connected in series and the liquid channels are connected in parallel.

6. The exhaust gas enrichment and stabilization system based on distributed temperature control according to claim 5, characterized in that, The absorption tank unit and / or the desorption tower are provided with a liquid equalizer and an absorption packing chamber from top to bottom.

7. The exhaust gas enrichment and stabilization system based on distributed temperature control according to claim 6, characterized in that, A gradually expanding nozzle is also provided between the liquid equalizer and the absorbent packing chamber.

8. The exhaust gas enrichment and stabilization system based on distributed temperature control according to claim 2, characterized in that, The heat exchange fluid is silicone oil.

9. A method for increasing and stabilizing the concentration of exhaust gas based on temperature-distributed control, characterized in that, The exhaust gas enrichment and stabilization system based on temperature-distributed control, as described in any one of claims 1 to 8, includes the following steps: Step 1, Pretreatment: The exhaust gas is pretreated by filtering and compression; Step 2, Absorption and Concentration: The pretreated exhaust gas is introduced into the absorption tower and contacted countercurrently with the absorption solvent to selectively absorb methane, resulting in rich liquid and tail gas. Step 3, Desorption and Regeneration: The rich liquid is heated and then sent to a desorption tower for depressurized desorption to obtain high-concentration methane gas; Step 4, Solvent Circulation and Cooling: Part of the desorbed lean solution is cooled and returned to the absorption tower for recycling, while the other part is purified by removing water and impurities and then returned to the main circulation. Step 5, Concentration Adjustment: Mix the high-concentration methane gas obtained in Step 3 with a portion of the tail gas diverted from Step 2 to obtain a mixed gas with a stable concentration. Step Six, Energy Integration: The heat generated during the compression process in Step One is recovered through a closed-loop heat exchange fluid and used for heating the rich solution in Step Three. At the same time, the cooling capacity carried by the fluid after releasing heat is used for cooling the lean solution in Step Four.

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