Coal mine ventilation air methane oxidation driven mine water zero discharge treatment system and method thereof

Abstract

The coal mine ventilation gas oxidation driving mine water zero discharge treatment system and method belong to the technical field of coal mine ventilation gas utilization and high mineralization mine water treatment, utilize low-temperature flue gas waste heat to realize forward osmosis NH4HCO3 draw solution regeneration, solve the problem of high energy consumption of forward osmosis wastewater treatment, utilize low-quality steam turbine generator set low-temperature exhaust steam and flue gas waste heat as the heat source for the first two stages of mine water concentration, realize the evaporation and reuse of more than 95% of mine water, the remaining less than 5% of concentrated mine water consumes high-pressure steam evaporation crystallization, greatly reduces the treatment cost of high mineralization mine water; the mine water zero discharge reuse distilled water is used for NH4HCO3 solution fertilizer preparation in the carbon dioxide capture process, the carbon dioxide greenhouse gas in the flue gas realizes low-energy consumption capture by generating NH4HCO3 solution fertilizer; also solves the problem that the stable gas oxidation device flue gas load does not match the changing heat supply load, improves the stability of the coal mine ventilation gas oxidation power generation and heat supply system operation.

Description

Technical Field

[0001] This invention belongs to the field of coal mine ventilation gas utilization and high-mineralization mine water treatment technology, and specifically relates to a zero-discharge treatment system and method for mine water driven by coal mine exhaust gas oxidation. Background Technology

[0002] Coal mining in my country generates 8 billion tons of mine water annually, accounting for approximately 60% of the country's industrial and domestic water shortage. However, its utilization rate is only 25%. Large quantities of untreated mine water are discharged directly, causing not only ground subsidence or collapse but also severe environmental pollution due to coal dust and salt content. The difficulty and high cost of treating highly mineralized mine water have become one of the most prominent problems restricting the development of coal mines.

[0003] To address the low methane concentration in coal mine exhaust air, a low-concentration methane oxidation heat energy utilization technology is employed to reduce fossil fuel waste and methane emissions. Ultra-low concentration methane extracted underground undergoes an exothermic oxidation reaction in an oxidation unit, producing high-temperature flue gas. This high-temperature flue gas is then used to generate superheated steam in a waste heat boiler to drive a back-pressure turbine generator. The extraction and exhaust steam from the back-pressure turbine are used to meet the mine's winter cooling, heating, and bathing needs. How to utilize the ultra-low concentration methane oxidation heat energy for zero-discharge of high-salinity mine water in a green and low-carbon manner presents a significant technical challenge in solving the high cost of mine water treatment and reducing carbon emissions.

[0004] Chinese patents with publication numbers CN111362453B, CN116444106A, and CN222700168U disclose methods for treating mine water in high-mineralization coal mines. The article "Application of MVR Technology in Zero Discharge and Resource Utilization of Mine Water" in the 2020 issue (Vol. 39, No. 2 of *Coal Technology*) introduces a steam mechanical recompression (MVR) mine water treatment system in a coal chemical plant in Ordos. While zero discharge of mine water can be achieved using processes such as pretreatment, electrodialysis, reverse osmosis, and evaporative crystallization, reverse osmosis consumes electricity and evaporative crystallization consumes high-pressure steam, resulting in excessively high mine water treatment costs. Existing treatment methods are insufficient to effectively reduce the cost of zero discharge of mine water.

[0005] Chinese patents CN105863722A and CN101912722A disclose a gas oxidation device for exhaust gas. The use of gas oxidation technology not only utilizes the heat of gas in the exhaust gas of the mine, but also needs to solve the problem of efficient utilization of gas oxidation heat energy according to the needs of coal mines. The article "Application of Ultra-Low Concentration Gas Oxidation and Low-Temperature Thermal Energy Utilization Technology in Dingji Coal Mine" in the April 2020 issue of "Shaanxi Coal" introduced a demonstration project of ultra-low concentration gas regenerative oxidation and low-temperature thermal energy utilization. The integrated application of ultra-low concentration gas oxidation for power generation, heating, and shaft antifreeze achieved the cascade utilization of ultra-low concentration gas oxidation thermal energy. However, the flue gas from the oxidation unit and waste heat boiler was directly emitted without low-cost capture of carbon dioxide in the flue gas. It was difficult to effectively utilize the thermal energy of flue gas with a temperature exceeding 100℃, resulting in thermal pollution and energy waste. The thermal load required by the coal mine for heating and insulation varies significantly throughout the year. Compared with the stable flue gas load of the gas oxidation unit, the changes in the coal mine's thermal load cause significant changes in the steam load of the waste heat boiler and the power generation and extraction load of the steam turbine unit, making it difficult for the entire gas oxidation thermal energy utilization system to achieve stable operation.

[0006] The following problems exist in the utilization of coal mine exhaust gas oxidation heat energy and the treatment methods for high-salinity mine water: (1) Existing methods for treating high-mineralization mine water, such as evaporation crystallization, electrodialysis and reverse osmosis, consume electricity and high-temperature and high-pressure steam, making it difficult to effectively reduce the cost of zero-discharge treatment of mine water.

[0007] (2) The carbon dioxide greenhouse gas in the flue gas emitted by the coal mine exhaust gas oxidation system is not captured at low cost. The waste heat of the low-temperature flue gas is difficult to be effectively utilized due to its low quality. The coal mine heat load varies significantly with the seasons, resulting in a mismatch between the stable flue gas load of the gas oxidation unit and the changing heat supply load, which affects the stable and continuous operation of the gas oxidation heat energy utilization system.

[0008] (3) The existing coal mine exhaust gas oxidation system does not consider the treatment of high-mineralization mine water in the cascade utilization of thermal energy. The existing high-mineralization mine water treatment methods do not utilize the heat of coal mine exhaust gas oxidation. It is necessary to establish a coupling method between the two to effectively solve the key problems of high mine water treatment cost and green emission of flue gas from exhaust gas oxidation system. Summary of the Invention

[0009] This invention provides a zero-discharge treatment system and method for mine water driven by oxidation of coal mine exhaust gas, which can solve the problems pointed out in the background art.

[0010] A coal mine exhaust gas oxidation-driven zero-discharge mine water treatment system includes an exhaust gas oxidation power generation and heating unit, a mine water treatment unit, and a carbon dioxide capture unit. The waste gas oxidation power generation and heating unit includes a ventilation system return air shaft, an oxidation device, a waste heat boiler, and a steam turbine generator set connected in sequence. The mine water treatment unit includes a low-temperature evaporator, a forward osmosis membrane module, an NH4HCO3 draw solution preparation tank, a condenser, a high-temperature evaporator, and a centrifuge. The carbon dioxide capture unit includes a flue gas cooler, a carbon dioxide absorber, an ammonia tank, and an NH4HCO3 water-fertilizer tank. The ventilation system's return air shaft is connected to the oxidation device, allowing the coal mine's exhaust air to enter the oxidation device through its air inlet under the drive of a power-driven component. The high-temperature flue gas outlet of the oxidation device is connected to the high-temperature flue gas inlet of the waste heat boiler. The exhaust air from the low-temperature flue gas outlet of the oxidation device and the low-temperature flue gas outlet of the waste heat boiler is combined and connected to the flue gas inlet of the flue gas cooler. The steam outlet of the waste heat boiler is connected to the steam turbine generator set. The steam extraction port and exhaust port of the steam turbine generator set are respectively connected to the high-temperature steam inlet of the high-temperature evaporator and the low-temperature steam inlet of the low-temperature evaporator. Mine water enters the low-temperature evaporator through the mine water inlet. The low-temperature evaporator is connected to the feed liquid inlet of the forward osmosis membrane module and the steam side of the condenser through the concentrated mine water outlet and the steam outlet of the low-temperature evaporator, respectively. The feed liquid outlet, draw liquid inlet, and draw liquid outlet of the forward osmosis membrane module are connected to the concentrated mine water inlet of the high-temperature evaporator, the concentrated draw liquid outlet of the NH4HCO3 draw liquid preparation tank, and the draw liquid inlet of the flue gas cooler, respectively. The concentrated mine water outlet of the high-temperature evaporator is connected to the concentrated mine water inlet and the centrifuge. The steam outlet of the high-temperature evaporator is connected to the steam side of the condenser. The low-temperature evaporator condensate outlet, the high-temperature evaporator condensate outlet, and the condensate in the condenser are connected to the ammonia water tank inlet via pipelines. The flue gas cooler's flue gas outlet and gas outlet are respectively connected to the carbon dioxide absorber's flue gas inlet and the NH4HCO3 extractant preparation tank's gas inlet. Its fresh water outlet is respectively connected to the NH4HCO3 extractant preparation tank's fresh water inlet and the ammonia tank's inlet. The ammonia tank's outlet is connected to the upper inlet of the carbon dioxide absorber. The carbon dioxide absorber's solution outlet is connected to the NH4HCO3 fertilizer tank and the middle inlet of the carbon dioxide absorber.

[0011] Preferably, the power drive component is a pumping pump, and the steam turbine generator set is a back-pressure steam turbine generator set.

[0012] A method for a zero-discharge treatment system for mine water driven by oxidation of coal mine exhaust gas includes the following steps: A. In the exhaust gas oxidation power generation and heating unit, exhaust air with a gas concentration of 0.5%-1.2% in the return air shaft of the ventilation system is pumped into the oxidation unit by a power drive. After the gas at this concentration is oxidized and released heat in the oxidation unit, it generates high-temperature flue gas of 950℃, which then enters the waste heat boiler. The high-temperature flue gas is cooled to 170-180℃ after heat exchange in the waste heat boiler, and then merges with the low-temperature exhaust gas of 70-75℃ flowing out of the low-temperature flue gas outlet of the oxidation unit. The merged 165-175℃ low-temperature flue gas is used as the heat source for the flue gas cooler in the carbon dioxide capture unit. The superheated steam generated in the waste heat boiler enters the steam turbine generator set for power generation through the steam outlet of the waste heat boiler. The steam discharged from the steam extraction port of the steam turbine generator set is used as the heating source for the high-temperature evaporator in the mine water treatment unit. The 65℃ saturated low-temperature steam discharged from the steam exhaust port of the steam turbine generator set is used as the heating source for the low-temperature evaporator in the mine water treatment unit. B. In the mine water treatment unit, 65℃ saturated steam condenses and releases latent heat of vaporization in the tube side of the low-temperature evaporator. Mine water with a salinity of 0.25-0.30% and concentrated mine water with a salinity of 3.0-3.5% after evaporation and concentration are mixed at the mine water inlet of the low-temperature evaporator to form a 2.0-2.3% feed liquid. After being heated in the shell side of the low-temperature evaporator, the feed liquid partially evaporates. Part of the 3.0-3.5% concentrated mine water after stage I concentration is returned to the mine water inlet of the low-temperature evaporator for repeated evaporation and concentration. The remainder enters the feed liquid side of the forward osmosis membrane module for stage II concentration. At the concentrated draw liquid outlet of the NH4HCO3 draw liquid preparation tank, the 15-20% NH4HCO3 concentrated draw liquid enters the draw liquid side of the forward osmosis membrane module through the draw liquid inlet. Under the action of natural osmotic pressure difference, fresh water in the concentrated mine water passes through the forward osmosis membrane and enters the draw liquid side. The NH4HCO3 concentrated draw liquid is diluted to... After reaching 4.0-5.5%, the concentrated mineral water enters the flue gas cooler of the carbon dioxide capture unit for regeneration. After being concentrated to 6.0-6.5% by stage II, the concentrated mineral water enters the high-temperature evaporator for stage III concentration. 0.5 MPa / 150℃ steam enters the shell side of the high-temperature evaporator through the steam inlet and condenses and releases heat. The concentrated mineral water with a concentration of 6.0-6.5% enters the tube side of the high-temperature evaporator through the concentrated mineral water inlet and is heated and evaporated. The saturated concentrated mineral water after stage III concentration flows out of the concentrated mineral water outlet of the high-temperature evaporator and enters the centrifuge to obtain crystallized salt. The generated steam enters the condenser through the high-temperature evaporator steam outlet and the low-temperature evaporator steam outlet, respectively, and is condensed by cooling water. The condensed fresh water in the condenser is collected with the condensate flowing out of the low-temperature evaporator condensate outlet and the high-temperature evaporator condensate outlet and is used to prepare ammonia water in the ammonia water tank of the carbon dioxide capture unit. C. In the carbon dioxide capture unit, the 165-175℃ low-temperature flue gas discharged from the oxidation unit and waste heat boiler of the exhaust gas oxidation power generation and heating unit releases sensible heat in the flue gas cooler and then enters the carbon dioxide absorber. The 4.0-5.5% NH4HCO3 absorbent flowing out of the draw solution outlet of the forward osmosis membrane module is heated and decomposed into NH3 and CO2 gases in the flue gas cooler. The decomposed gases enter the NH4HCO3 absorbent preparation tank from the gas outlet of the flue gas cooler to generate 15-20% NH4HCO3 absorbent. A portion of the freshwater flowing out of the freshwater outlet of the flue gas cooler enters the NH4HCO3 absorbent through the freshwater inlet. Concentrated draw solution is prepared in the draw solution preparation tank. The regenerated concentrated draw solution is repeatedly recycled by the forward osmosis membrane module. The remaining fresh water enters the ammonia tank for preparing ammonia water. The ammonia water flowing out of the ammonia tank enters the carbon dioxide absorber through the upper inlet. The dilute NH4HCO3 solution flowing out of the solution outlet of the carbon dioxide absorber enters the carbon dioxide absorber through the middle inlet for spraying. Air and CO2 in the flue gas flow upward from the bottom of the carbon dioxide absorber. The dilute NH4HCO3 solution and ammonia water absorb CO2 in the flue gas to generate 3.0-5.0% NH4HCO3 solution, which enters the NH4HCO3 water-fertilizer tank. The air in the flue gas is discharged from the top of the carbon dioxide absorber.

[0013] The beneficial effects of this invention are: 1. This application designs a zero-discharge mine water treatment system based on the cascade utilization technology of low-concentration gas oxidation heat energy. It uses low-temperature flue gas waste heat to regenerate the NH4HCO3 extractant in forward osmosis, which solves the problem of high energy consumption in forward osmosis mine water treatment. It uses low-quality back-pressure steam turbine generator set low-temperature exhaust steam and flue gas waste heat as heat sources for the first two stages of mine water concentration, realizing the evaporation and reuse of more than 95% of the mine water. The remaining less than 5% of concentrated mine water is evaporated and crystallized by high-pressure extraction steam, which significantly reduces the treatment cost of high-mineralization mine water. 2. Carbon dioxide greenhouse gas in flue gas is captured with low energy consumption by generating NH4HCO3 solution fertilizer, thus realizing the efficient utilization of carbon dioxide greenhouse gas and saving the high-pressure steam consumed by conventional carbon dioxide capture and the electricity consumed by carbon dioxide compression. Distilled water recycled from mine water with zero discharge is used to prepare NH4HCO3 solution fertilizer in the carbon dioxide capture process.

[0014] 3. By coupling coal mine exhaust gas oxidation with zero-discharge treatment of mine water, and using cascaded thermal energy to provide a stable heat source for mine water concentration that does not change with the seasons, the problem of mismatch between stable flue gas load of gas oxidation unit and changing heating load is solved, and the stability of coal mine exhaust gas oxidation power generation and heating system is improved. Attached Figure Description

[0015] In the picture: Figure 1This is a diagram of a coal mine exhaust gas oxidation-driven zero-discharge treatment system for mine water.

[0016] The diagram labels are as follows: 1. Exhaust gas oxidation power generation and heating unit; 2. Mine water treatment unit; 3. Carbon dioxide capture unit; 4. Ventilation system return air shaft; 5. Extraction pump; 6. Oxidation unit; 61. Oxidation unit air inlet; 62. Oxidation unit high-temperature flue gas outlet; 63. Oxidation unit low-temperature flue gas outlet; 7. Waste heat boiler; 71. Waste heat boiler high-temperature flue gas inlet; 72. Waste heat boiler low-temperature flue gas outlet; 73. Waste heat boiler steam outlet; 8. Back-pressure steam turbine generator set; 81. Steam extraction port; 82. Exhaust port; 9. Low-temperature evaporator; 91. Low-temperature evaporator steam inlet; 92. Mine water inlet; 93. Low-temperature evaporator concentrated mine water outlet; 94. Low-temperature evaporator steam outlet; 95. Low-temperature evaporator condensate outlet; 10. Forward osmosis membrane module; 101. Feed liquid inlet; 102. Feed liquid outlet; 103. Forward osmosis membrane module draw liquid inlet; 104. 11. Forward osmosis membrane module draw solution outlet; 12. NH4HCO3 draw solution preparation tank; 13. Concentrated draw solution outlet; 14. Fresh water inlet; 15. Gas inlet; 16. Condenser; 17. High-temperature evaporator; 18. High-temperature evaporator steam inlet; 19. Concentrated mineral water inlet; 20. High-temperature evaporator concentrated mineral water outlet; 20. High-temperature evaporator steam outlet; 21. High-temperature evaporator condensate outlet; 22. Centrifuge; 23. Flue gas cooler; 14. Flue gas cooler flue gas inlet; 15. Flue gas cooler flue gas outlet; 16. Flue gas cooler draw solution inlet; 17. Fresh water outlet; 18. Gas outlet; 19. Carbon dioxide absorber; 10. Carbon dioxide absorber flue gas inlet; 11. Upper inlet; 12. Solution outlet; 19. Middle inlet; 20. Ammonia tank; 21. NH4HCO3 water-fertilizer tank. Detailed Implementation

[0017] The following detailed description of a specific embodiment of the present invention is provided in conjunction with the accompanying drawings. However, it should be understood that the scope of protection of the present invention is not limited to the specific embodiment.

[0018] like Figure 1 As shown in the figure, the present invention provides a coal mine exhaust gas oxidation-driven mine water zero-discharge treatment system, which includes an exhaust gas oxidation power generation and heating unit 1, a mine water treatment unit 2, and a carbon dioxide capture unit 3. The waste gas oxidation power generation and heating unit 1 includes a ventilation system return air shaft 4, an oxidation device 6, a waste heat boiler 7, and a steam turbine generator set 8 connected in sequence. The mine water treatment unit 2 includes a low-temperature evaporator 9, a forward osmosis membrane module 10, an NH4HCO3 draw solution preparation tank 11, a condenser 12, a high-temperature evaporator 13, and a centrifuge 14. The carbon dioxide capture unit 3 includes a flue gas cooler 15, a carbon dioxide absorber 16, an ammonia tank 17, and an NH4HCO3 water-fertilizer tank 18. The ventilation system return air shaft 4 is connected to the oxidation device 6, so that the coal mine exhaust air enters the oxidation device 6 through the oxidation device air inlet 61 under the drive of the power drive component 5. The high temperature flue gas outlet 62 of the oxidation device 6 is connected to the high temperature flue gas inlet 71 of the waste heat boiler 7. The exhaust air from the low temperature flue gas outlet 63 of the oxidation device 6 and the low temperature flue gas outlet 72 of the waste heat boiler 7 is combined and connected to the flue gas inlet 151 of the flue gas cooler 15. The steam outlet 73 of the waste heat boiler 7 is connected to the steam turbine generator set 8. The steam extraction port 81 and the exhaust port 82 of the steam turbine generator set 8 are respectively connected to the high temperature evaporator steam inlet 131 of the high temperature evaporator 13 and the low temperature evaporator steam inlet 91 of the low temperature evaporator 9. Mine water enters the low-temperature evaporator 9 through the mine water inlet 92. The low-temperature evaporator 9 is connected to the feed liquid inlet 101 of the forward osmosis membrane module 10 and the steam side of the condenser 12 through the concentrated mine water outlet 93 and the steam outlet 94, respectively. The feed liquid outlet 102, the draw liquid inlet 103, and the draw liquid outlet 104 of the forward osmosis membrane module 10 are connected to the concentrated mine water inlet 132 of the high-temperature evaporator 13 and the concentrated draw liquid outlet of the NH4HCO3 draw liquid preparation tank 11, respectively. The liquid outlet 111 is connected to the flue gas cooler draw liquid inlet 153 of the flue gas cooler 15. The high temperature evaporator concentrated mineral water outlet 133 of the high temperature evaporator 13 is connected to the concentrated mineral water inlet 132 and the centrifugal separator 14. The high temperature evaporator steam outlet 134 of the high temperature evaporator 13 is connected to the steam side of the condenser 12. The low temperature evaporator condensate outlet 95 of the low temperature evaporator 9, the high temperature evaporator condensate outlet 135 of the high temperature evaporator 13, and the condensate in the condenser 12 are connected to the ammonia water tank 17 inlet via pipelines. The flue gas outlet 152 and gas outlet 155 of the flue gas cooler 15 are respectively connected to the flue gas inlet 161 of the carbon dioxide absorber 16 and the gas inlet 113 of the NH4HCO3 extractant preparation tank 11. Its fresh water outlet 154 is respectively connected to the fresh water inlet 112 of the NH4HCO3 extractant preparation tank 11 and the water inlet of the ammonia tank 17. The outlet of the ammonia tank 17 is connected to the upper inlet 162 of the carbon dioxide absorber 16. The solution outlet 163 of the carbon dioxide absorber 16 is connected to the NH4HCO3 fertilizer tank 18 and the middle inlet 164 of the carbon dioxide absorber 16.

[0019] Preferably, the power drive component 5 is a pumping pump, and the steam turbine generator set 8 is a back-pressure steam turbine generator set.

[0020] A method for a zero-discharge treatment system for mine water driven by oxidation of coal mine exhaust gas includes the following steps: A. In the exhaust gas oxidation power generation and heating unit 1, exhaust air with a gas concentration of 0.5%-1.2% in the return air shaft 4 of the ventilation system is pumped into the oxidation unit 6 by the power drive component 5. This concentration of gas is oxidized and releases heat in the oxidation unit 6 to generate high-temperature flue gas of 950℃, which then enters the waste heat boiler 7. The high-temperature flue gas is cooled to 170-180℃ in the waste heat boiler 7 after heat exchange, and then merges with the low-temperature exhaust gas of 70-75℃ flowing out of the low-temperature flue gas outlet 63 of the oxidation unit 6. The collected 165-175℃ low-temperature flue gas is used as the heat source for the flue gas cooler 15 in the carbon dioxide capture unit 3. The superheated steam generated in the waste heat boiler 7 enters the steam turbine generator set 8 through the steam outlet 73 of the waste heat boiler to generate electricity. The steam discharged from the steam extraction port 81 of the steam turbine generator set 8 is used as the heating source for the high-temperature evaporator 13 in the mine water treatment unit 2. The 65℃ saturated low-temperature steam discharged from the steam exhaust port 82 of the steam turbine generator set is used as the heating source for the low-temperature evaporator 9 in the mine water treatment unit 2. B. In mine water treatment unit 2, 65℃ saturated steam condenses and releases latent heat of vaporization in the tube side of low-temperature evaporator 9. Mine water with a salinity of 0.25-0.30% and concentrated mine water with a salinity of 3.0-3.5% after evaporation and concentration are mixed at the mine water inlet 92 of low-temperature evaporator 9 to form a feed liquid with a salinity of 2.0-2.3%. The feed liquid is partially evaporated after being heated in the shell side of low-temperature evaporator 9. The concentrated mine water with a salinity of 3.0-3.5% after stage I concentration is partially returned to the mine water inlet 92 of low-temperature evaporator 9 for further treatment. The solution is repeatedly evaporated and concentrated, with the remainder entering the feed solution side of the forward osmosis membrane module 10 for secondary concentration. At the concentrated draw solution outlet 111 of the NH4HCO3 draw solution preparation tank 11, a 15-20% NH4HCO3 concentrated draw solution enters the draw solution side of the forward osmosis membrane module 10 through the draw solution inlet 103. Under the influence of natural osmotic pressure difference, fresh water from the concentrated mineral well water passes through the forward osmosis membrane into the draw solution side. The NH4HCO3 concentrated draw solution is diluted to 4.0-5.5% before entering... The carbon dioxide capture unit 3 is regenerated in the flue gas cooler 15. The concentrated mineral water, after being concentrated to 6.0-6.5% in stage II, enters the high-temperature evaporator 13 for stage III concentration. 0.5 MPa / 150°C steam enters the shell side of the high-temperature evaporator 13 through the steam inlet 131, where it condenses and releases heat. The concentrated mineral water with a concentration of 6.0-6.5% enters the tube side of the high-temperature evaporator 13 through the concentrated mineral water inlet 132 for heating and evaporation. The saturated concentrated mineral water after stage III concentration exits through the concentrated mineral water outlet 1 of the high-temperature evaporator. 33 flows out into centrifuge 14 to obtain crystalline salt. The generated steam enters condenser 12 through high temperature evaporator steam outlet 134 of high temperature evaporator 13 and low temperature evaporator steam outlet 94 of low temperature evaporator 9 and is condensed by cooling water. The condensed fresh water in condenser 12 and the condensate flowing out of low temperature evaporator 9 and high temperature evaporator 13 are collected and used to prepare ammonia water in ammonia water tank 17 of carbon dioxide capture unit 3. C. In the carbon dioxide capture unit 3, the low-temperature flue gas of 165-175℃ discharged from the oxidation device 6 and waste heat boiler 7 of the exhaust gas oxidation power generation and heating unit 1 releases sensible heat in the flue gas cooler 15 and then enters the carbon dioxide absorber 16. The 4.0-5.5% NH4HCO3 absorbent flowing out of the draw solution outlet 104 of the forward osmosis membrane module 10 is heated and decomposed into NH3 and CO2 gases in the flue gas cooler 15. The decomposed gas enters the NH4HCO3 absorbent preparation tank 11 from the gas outlet 155 of the flue gas cooler to generate 15-20% NH4HCO3 absorbent. A portion of the fresh water flowing out of the fresh water outlet 154 of the flue gas cooler 15 enters the NH4HCO3 absorbent through the fresh water inlet 112. Concentrated extract solution is prepared in the extract preparation tank 11. The regenerated concentrated extract solution is repeatedly recycled by the forward osmosis membrane module 10. The remaining fresh water enters the ammonia tank 17 for preparing ammonia water. The ammonia water flowing out of the ammonia tank 17 enters the carbon dioxide absorber 16 through the upper inlet 162. The dilute NH4HCO3 solution flowing out of the solution outlet 163 of the carbon dioxide absorber 16 enters the carbon dioxide absorber 16 through the middle inlet 164 for spraying. Air and CO2 in the flue gas flow upward from the bottom of the carbon dioxide absorber 16. The dilute NH4HCO3 solution and ammonia water absorb CO2 in the flue gas to generate 3.0-5.0% NH4HCO3 solution, which enters the NH4HCO3 water-fertilizer tank 18. The air in the flue gas is discharged from the top of the carbon dioxide absorber 16.

[0021] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A coal mine ventilation air methane oxidation driven mine water zero discharge treatment system, characterized in that: It includes a waste gas oxidation power generation and heating unit (1), a mine water treatment unit (2), and a carbon dioxide capture unit (3). ​ The waste gas oxidation power generation and heating unit (1) includes a ventilation system return air shaft (4), an oxidation device (6), a waste heat boiler (7), and a steam turbine generator set (8) connected in sequence. The mine water treatment unit (2) includes a low-temperature evaporator (9), a forward osmosis membrane module (10), an NH4HCO3 extract preparation tank (11), a condenser (12), a high-temperature evaporator (13), and a centrifuge (14). The carbon dioxide capture unit (3) includes a flue gas cooler (15), a carbon dioxide absorber (16), an ammonia tank (17), and an NH4HCO3 water-fertilizer tank (18). The ventilation system return air shaft (4) is connected to the oxidation device (6) so that the coal mine exhaust air enters the oxidation device (6) through the oxidation device air inlet (61) under the drive of the power drive component (5). The high temperature flue gas outlet (62) of the oxidation device (6) is connected to the high temperature flue gas inlet (71) of the waste heat boiler (7). The low temperature flue gas outlet (63) of the oxidation device (6) and the low temperature flue gas outlet of the waste heat boiler (7) are also connected. The exhaust air from outlet (72) is combined and connected to the flue gas inlet (151) of the flue gas cooler (15). The steam outlet (73) of the waste heat boiler (7) is connected to the steam turbine generator set (8). The steam extraction port (81) and exhaust port (82) of the steam turbine generator set (8) are respectively connected to the high temperature evaporator steam inlet (131) of the high temperature evaporator (13) and the low temperature evaporator steam inlet (91) of the low temperature evaporator (9). Mine water enters the low-temperature evaporator (9) through the mine water inlet (92). The low-temperature evaporator (9) is connected to the feed liquid inlet (101) of the forward osmosis membrane module (10) and the steam side of the condenser (12) through the concentrated mine water outlet (93) and the steam outlet (94) of the low-temperature evaporator, respectively. The feed liquid outlet (102), the draw liquid inlet (103), and the draw liquid outlet (104) of the forward osmosis membrane module (10) are connected to the concentrated mine water inlet (132) of the high-temperature evaporator (13) and the concentrated draw liquid of the NH4HCO3 draw liquid preparation tank (11), respectively. The outlet (111) and the flue gas cooler draw liquid inlet (153) of the flue gas cooler (15) are connected. The high temperature evaporator concentrated mineral water outlet (133) of the high temperature evaporator (13) is connected to the concentrated mineral water inlet (132) and the centrifuge (14). The high temperature evaporator steam outlet (134) of the high temperature evaporator (13) is connected to the steam side of the condenser (12). The low temperature evaporator condensate outlet (95) of the low temperature evaporator (9), the high temperature evaporator condensate outlet (135) of the high temperature evaporator (13), and the condensate in the condenser (12) are connected to the inlet of the ammonia tank (17) via pipelines. The flue gas outlet (152) and gas outlet (155) of the flue gas cooler (15) are respectively connected to the flue gas inlet (161) of the carbon dioxide absorber (16) and the gas inlet (113) of the NH4HCO3 extractant preparation tank (11). Its fresh water outlet (154) is respectively connected to the fresh water inlet (112) of the NH4HCO3 extractant preparation tank (11) and the water inlet of the ammonia tank (17). The outlet of the ammonia tank (17) is connected to the upper inlet (162) of the carbon dioxide absorber (16). The solution outlet (163) of the carbon dioxide absorber (16) is connected to the NH4HCO3 fertilizer tank (18) and the middle inlet (164) of the carbon dioxide absorber (16).

2. The coal mine exhaust gas oxidation-driven zero-discharge mine water treatment system according to claim 1, characterized in that, The power drive unit (5) is a pumping pump, and the steam turbine generator set (8) is a back pressure steam turbine generator set.

3. A method for a zero-discharge treatment system for mine water driven by oxidation of coal mine exhaust gas, characterized in that: Includes the following steps: A. In the exhaust gas oxidation power generation and heating unit (1), the exhaust gas with a gas concentration of 0.5%-1.2% in the return air shaft (4) of the ventilation system is pumped into the oxidation device (6) by the power drive (5). After the gas of this concentration is oxidized and released in the oxidation device (6), it generates high-temperature flue gas of 950°C, and enters the waste heat boiler (7) from the oxidation device (6). The high-temperature flue gas is cooled to 170-180°C after heat exchange in the waste heat boiler (7), and is collected with the low-temperature exhaust gas of 70-75°C flowing out of the low-temperature flue gas outlet (63) of the oxidation device (6). The 165-175℃ low-temperature flue gas is used as the heat source for the flue gas cooler (15) in the carbon dioxide capture unit (3). The superheated steam generated in the waste heat boiler (7) enters the steam turbine generator set (8) through the steam outlet (73) of the waste heat boiler to generate electricity. The steam discharged from the steam extraction port (81) of the steam turbine generator set (8) is used as the heating source for the high-temperature evaporator (13) in the mine water treatment unit (2). The 65℃ saturated low-temperature steam discharged from the steam exhaust port (82) of the steam turbine generator set is used as the heating source for the low-temperature evaporator (9) in the mine water treatment unit (2). B. In the mine water treatment unit (2), 65℃ saturated steam condenses and releases latent heat of vaporization in the tube side of the low-temperature evaporator (9). Mine water with a salinity of 0.25-0.30% and concentrated mine water with a salinity of 3.0-3.5% after evaporation and concentration are mixed at the mine water inlet (92) of the low-temperature evaporator (9) to form a feed liquid with a salinity of 2.0-2.3%. The feed liquid is partially evaporated after being heated in the shell side of the low-temperature evaporator (9). The concentrated mine water with a salinity of 3.0-3.5% after stage I concentration is partially returned to the mine water inlet (92) of the low-temperature evaporator (9) for repeated evaporation. The concentrate is concentrated, and the remaining portion enters the feed liquid side of the forward osmosis membrane module (10) for secondary concentration; the concentrated NH4HCO3 draw liquid with a concentration of 15-20% at the concentrated draw liquid outlet (111) of the NH4HCO3 draw liquid preparation tank (11) enters the draw liquid side of the forward osmosis membrane module (10) through the draw liquid inlet (103). Under the action of natural osmotic pressure difference, fresh water in the concentrated mineral well water passes through the forward osmosis membrane and enters the draw liquid side. The concentrated NH4HCO3 draw liquid is diluted to 4.0-5.5% and then enters the carbon dioxide capture unit ( 3) The flue gas cooler (15) is regenerated, and the concentrated mineral water is concentrated to 6.0-6.5% by stage II and then enters the high-temperature evaporator (13) for stage III concentration; 0.5Mpa / 150℃ steam enters the shell side of the high-temperature evaporator (13) through the steam inlet (131) and condenses and releases heat, and the concentrated mineral water with a concentration of 6.0-6.5% enters the tube side of the high-temperature evaporator (13) through the concentrated mineral water inlet (132) and is heated and evaporated. The saturated concentrated mineral water after stage III concentration flows out from the concentrated mineral water outlet (133) of the high-temperature evaporator and enters the centrifugal separator. The crystalline salt is obtained from the off-machine (14), and the generated steam enters the condenser (12) through the high temperature evaporator steam outlet (134) of the high temperature evaporator (13) and the low temperature evaporator steam outlet (94) of the low temperature evaporator (9) and is condensed by cooling water. The condensed fresh water in the condenser (12) and the condensate flowing out of the low temperature evaporator condensate outlet (95) of the low temperature evaporator (9) and the high temperature evaporator condensate outlet (135) of the high temperature evaporator (13) are collected and used to prepare ammonia water in the ammonia water tank (17) of the carbon dioxide capture unit (3). C. In the carbon dioxide capture unit (3), the low-temperature flue gas of 165-175℃ discharged from the oxidation device (6) and waste heat boiler (7) of the exhaust gas oxidation power generation and heating unit (1) releases sensible heat in the flue gas cooler (15) and then enters the carbon dioxide absorber (16). The 4.0-5.5% NH4HCO3 absorbent flowing out of the positive osmosis membrane module absorbent outlet (104) of the positive osmosis membrane module (10) is heated and decomposed into NH3 and CO2 gases in the flue gas cooler (15). The decomposed gas enters the NH4HCO3 absorbent preparation tank (11) from the flue gas cooler gas outlet (155) to generate 15-20% NH4HCO3 absorbent. A portion of the fresh water flowing out of the fresh water outlet (154) of the flue gas cooler enters the NH4HCO3 absorbent through the fresh water inlet (112). Concentrated extract solution is prepared in the extract solution preparation tank (11). The regenerated concentrated extract solution is repeatedly recycled by the forward osmosis membrane module (10). The remaining fresh water enters the ammonia tank (17) for preparing ammonia water. The ammonia water flowing out of the ammonia tank (17) enters the carbon dioxide absorber (16) through the upper inlet (162). The dilute NH4HCO3 solution flowing out of the solution outlet (163) of the carbon dioxide absorber (16) enters the carbon dioxide absorber (16) through the middle inlet (164) for spraying. The air and CO2 in the flue gas flow upward from the lower part of the carbon dioxide absorber (16). The dilute NH4HCO3 solution and ammonia water absorb the CO2 in the flue gas to generate 3.0-5.0% NH4HCO3 solution, which enters the NH4HCO3 water-fertilizer tank (18). The air in the flue gas is discharged from the top of the carbon dioxide absorber (16).

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