System for preventing coal spontaneous combustion by using coal ash mineralized CO2 and product and application method thereof

Abstract

The invention belongs to a carbon dioxide storage and goaf coal spontaneous combustion prevention and control technology, and particularly relates to a coal spontaneous combustion prevention and control system through coal ash mineralization CO2 and products and an application method of the coal spontaneous combustion prevention and control system. The system comprises a slurry preparation unit, a flue gas pretreatment unit, a mineralization reaction unit and a slurry filling unit; fly ash treatment, CO2 capture and mineralization and mine grouting fire prevention and extinguishing are combined, alkaline earth metal ions in fly ash are promoted to be leached through a pulping stirring tank, CO2 in reaction flue gas is mineralized through calcium and magnesium ions in slurry, CO2 dissolution is promoted through pressurization, an impeller is arranged in a reactor, gas spirally ascends in the ascending process, and the gas is recycled. According to the method, the coal ash slurry serves as a gas inlet, the stroke of the gas in the slurry is increased, the retention time is prolonged, gas, liquid and solid mixing is promoted, meanwhile, the additive is combined to improve the mineralization reaction efficiency, continuous CO2 mineralization of the large-flow coal ash slurry is finally achieved, a product is injected into an underground goaf to be used for preventing and controlling coal spontaneous combustion, and then the multiple effects of coal ash solid waste treatment, CO2 emission reduction and disaster prevention and control are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of carbon dioxide storage and prevention of spontaneous combustion of coal in goaf areas, and in particular to a fly ash mineralized CO2 and product prevention and control system for spontaneous combustion of coal and an application method thereof. Background Art

[0002] The Guiding Opinions on Comprehensive Utilization of Bulk Solid Waste points out that by 2025, the comprehensive utilization capacity of fly ash and other bulk fly ash will be significantly improved, and the comprehensive utilization rate of newly added bulk fly ash will reach 60%. Fly ash and other fly ash can react with CO2 for mineralization, achieving long-term storage of CO2. Integrating fly ash grouting fire prevention and extinguishing with CO2 storage to form a set of key technologies for coordinated emission reduction and disaster prevention not only meets the national dual carbon goals, but also improves the level of fire prevention and extinguishing in coal mines, which has important practical significance.

[0003] At present, relevant research on the mineralization of CO2 from fly ash has been widely reported. The key to the mineralization reaction lies in the leaching of alkali metal ions such as calcium and magnesium in the fly ash slurry, and the absorption and reaction of CO2 in the slurry. Since both ion leaching and carbonation reactions require a certain amount of time, most existing studies use discontinuous feeding, that is, adding fly ash slurry and CO2 to the reactor and stirring them thoroughly, and collecting the mineralized products after the reaction is completed. However, this method has a small amount of CO2 and fly ash processing, and cannot achieve the purpose of large-scale carbon capture and grouting fire prevention and extinguishing.

[0004] In order to achieve large flow and continuous mineralization of CO2, CN 114984716 A proposed a method for continuously capturing flue gas CO2 using a fly ash adsorption box, wherein the fly ash particle size used is less than 500 mesh, but the dry mineralization efficiency is low. CN113413754 A proposed a carbon fixation and alkali reduction reaction device and its control method, which uses fly ash slurry to absorb flue gas CO2, but lacks strengthening measures in the alkali metal ion leaching, CO2 absorption, and gas-liquid-solid mixing process, and the overall mineralization efficiency is low. Summary of the invention

[0005] The purpose of the present invention is to solve the problem of low efficiency of fly ash mineralization to CO2 in the prior art, and to propose a fly ash mineralization CO2 and product prevention and control of coal spontaneous combustion system and its application method, which integrates fly ash grouting fire prevention and extinguishing with CO2 storage to form a complete set of key technologies for coordinated emission reduction and disaster prevention.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A fly ash mineralization CO2 and product prevention and control system for coal spontaneous combustion, comprising a slurry preparation unit, a flue gas pretreatment unit, a mineralization reaction unit, and a slurry injection unit;

[0008] The slurry preparation unit includes a fly ash silo, a first screw feeder, a leaching agent silo, a second screw feeder, a water supply pipeline, a slurry stirring tank, and a slurry pump; the fly ash silo is installed at the inlet of the first screw feeder, the leaching agent silo is installed at the inlet of the second screw feeder, the outlets of the first screw feeder, the second screw feeder and the water supply pipeline are all connected to the slurry stirring tank, and the outlet of the slurry stirring tank is connected to the top of the mineralization reaction unit through a slurry pump;

[0009] The flue gas pretreatment unit includes an initial gas supply pipeline, a filter, a compressor, a high-pressure gas pipeline, a pressure gauge, a flow meter, and a gas valve; the filter is arranged on the initial gas supply pipeline, the initial gas supply pipeline is connected to the compressor inlet, the compressor outlet is connected to the bottom of the initial gas supply pipeline through the high-pressure gas pipeline, and the pressure gauge, gas flow meter, and gas valve are installed on the high-pressure gas pipeline;

[0010] The mineralization reaction unit includes a reactor and a gas inlet, a slurry inlet, and a mineralization product outlet arranged on the reactor; the gas inlet is connected to a high-pressure gas pipeline, the slurry inlet is connected to a slurry stirring tank pipeline, and the mineralization product outlet is located at the bottom of the reactor;

[0011] The slurry injection unit includes a buffer tank, a slurry valve, and a grouting pipeline. One end of the grouting pipeline is connected to the buffer tank, and the other end is connected to the goaf. The buffer tank is connected to the mineralized product outlet through a pipeline, and the slurry valve is arranged on the grouting pipeline.

[0012] As a further preferred solution, the first screw feeder is controlled by a first variable frequency motor to control the speed of the first screw feeder to adjust the rate of adding fly ash;

[0013] The second spiral feeder is controlled by a second variable frequency motor to control the speed and adjust the addition rate of the leaching agent;

[0014] The water supply pipeline is equipped with liquid valves and liquid flow meters for regulation and monitoring.

[0015] As a further preferred solution, the flow range of the water supply pipeline is 0~80m 3 / h, the feeding rate range of the first screw feeder is 0-20t / h, and the feeding rate range of the second screw feeder is 0-4t / h.

[0016] As a further preferred solution, the operating pressure range of the compressor is 0-2 MPa, and the gas mass flow range is 0-4 kg / s.

[0017] As a further preferred embodiment, the reactor is filled with slurry, and the flow direction is gas upward and liquid and solid downward;

[0018] The reactor is equipped with a multi-stage impeller, the speed of which is controlled by a third variable frequency motor to enhance the gas-liquid-solid mixing process.

[0019] As a further preferred solution, the grouting pipeline is also connected to a flushing pipeline, and when the mineralized CO2 product blocks the pipeline, the flushing pipeline is activated for flushing.

[0020] A method for applying a fly ash mineralized CO2 and product system for preventing and controlling spontaneous combustion of coal, comprising the following steps:

[0021] Step 1: Start the motors of the first screw feeder, the second screw feeder and the pulping and mixing tank, open the water supply pipeline, and mix the fly ash, additives and water in the pulping and mixing tank;

[0022] Step 2: When the liquid level in the slurry mixing tank reaches a specified height, the slurry pump is turned on to deliver the fly ash slurry to the reactor;

[0023] Step 3: When the reactor is filled with fly ash slurry, the outlet of the mineralized product is opened to allow it to flow to the buffer tank;

[0024] Step 4: When the liquid level in the buffer tank reaches the specified height, open the slurry valve on the grouting pipeline to inject grout into the goaf;

[0025] Step 5: Open the gas valve on the high-pressure gas pipeline to allow the CO2-containing flue gas to enter the reactor for mineralization reaction. The overall system is started up, and the continuous preparation of large-flow fly ash slurry, mineralization of CO2 and grouting for fire prevention and extinguishing are achieved.

[0026] Beneficial Effects

[0027] (1) In order to utilize fly ash slurry to efficiently mineralize CO2, it is first necessary to fully leach out alkali metal ions such as calcium and magnesium in the fly ash particles. Without taking additional measures, the leaching rate of fly ash alkali metal ions is low and the time required is long. Therefore, additives such as ammonium salts are often used to promote their leaching. However, related research mostly stays in laboratory reaction conditions with small processing volume and discontinuous feeding. The present invention realizes continuous feeding and ratio adjustment of fly ash and additives (the ratio of water, fly ash and additives is 6:1:1) through a silo, a screw feeder, and a continuous weighing device, thereby enhancing the leaching of alkali metal ions in the fly ash slurry, and ensuring that the residence time meets the time required for leaching during the continuous feeding and slurrying process of the slurry mixing tank.

[0028] (2) When there are a large number of alkali metal ions in the slurry, how to ensure the dissolution or absorption of CO2 in the slurry is the key to the efficiency of the subsequent mineralization reaction. The present invention pressurizes the flue gas containing CO2 and sends it to the high-pressure mineralization reactor, so that the dissolution amount of CO2 in the slurry is significantly increased, thereby improving the mineralization efficiency.

[0029] (3) Studies have shown that the CO2 mineralization reaction rate in alkaline fly ash slurry is slow, and the residence time in the reactor under continuous feeding and discharging conditions is short, which is insufficient to complete the mineralization reaction. The present invention arranges a multi-stage adjustable impeller in the reactor, and uses the rotation of the impeller to make the gas spiral upward during the upward process, thereby increasing the gas stroke in the slurry, increasing the residence time, and promoting the mixing of gas, liquid, and solid, thereby maximizing the CO2 mineralization efficiency under continuous feeding and discharging conditions.

[0030] (4) Traditional fire prevention and extinguishing technologies used in coal mine goafs: fly ash grouting fire prevention and extinguishing technology costs 150 yuan per cubic meter, and liquid CO2 direct injection inertization and cooling technology costs 210 yuan per ton. After the fly ash slurry mineralization and CO2 storage is combined with goaf fire prevention and extinguishing, every 100 tons of mineralized products used for goaf fire prevention and extinguishing effectively saves 21,000 yuan. Each ton of fly ash adsorbed and sealed CO2 can also bring corresponding carbon emission reduction benefits. The fly ash slurry mineralization CO2 product can block the oxidation process of the coal in the goaf, eliminate the risk of spontaneous combustion of the coal in the goaf, ensure the safe production of the mine, significantly improve the production efficiency of the mine, and help increase the production of coal mining enterprises. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of a method for preventing and controlling coal spontaneous combustion by using fly ash to mineralize CO2 and its products according to the present invention;

[0032] Figure 2 It is a schematic diagram of the process of the present invention;

[0033] Figure markings: 1-slurry preparation unit, 2-flue gas pretreatment unit, 3-mineralization reaction unit, 4-slurry perfusion unit, 5-fly ash silo, 6-first screw feeder, 7-leaching agent silo, 8-second screw feeder, 9-water supply pipeline, 10-slurry mixing tank, 11-slurry pump, 12-gas supply pipeline, 13-filter, 14-compressor, 15-high-pressure gas pipeline, 16-pressure gauge, 17-gas flowmeter, 18-gas valve, 19-gas inlet, 20-slurry inlet, 21-mineral product outlet, 22-reactor, 23-buffer tank, 24-slurry valve, 25-grouting pipeline, 26-first variable frequency motor, 27-second variable frequency motor, 28-liquid valve, 29-liquid flowmeter, 30-third variable frequency motor, 31-flushing pipeline. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0035] Embodiment 1

[0036] Combination Figure 1 As shown, the present invention is an integrated system for preventing and controlling coal spontaneous combustion by grouting fly ash mineralized CO2 and its products, the system comprising a slurry preparation unit 1, a flue gas pretreatment unit 2, a mineralization reaction unit 3, and a slurry injection unit 4;

[0037] The slurry preparation unit 1 includes a fly ash silo 5, a first screw feeder 6, a leaching agent silo 7, a second screw feeder 8, a water supply pipeline 9, a slurry mixing tank 10, and a slurry pump 11;

[0038] The flue gas pretreatment unit 2 includes an initial gas supply pipeline 12, a filter 13, a compressor 14, a high-pressure gas pipeline 15, a pressure gauge 16, a gas flow meter 17, and a gas valve 18;

[0039] The mineralization reaction unit 3 includes a gas inlet 19, a slurry inlet 20, a mineralization product outlet 21, and a reactor 22;

[0040] The slurry injection unit 4 includes a buffer tank 23 , a slurry valve 24 , and a grouting pipeline 25 .

[0041] Combination Figure 1 As shown, the lower part of the fly ash silo 5 is connected to the inlet of the first screw feeder 6, the lower part of the leaching agent silo 7 is connected to the inlet of the second screw feeder 8, the outlets of the first screw feeder 6, the second screw feeder 8 and the water supply pipeline 9 are all connected to the pulping and stirring tank 10, and the outlet of the pulping and stirring tank 10 is connected to the slurry pump 11;

[0042] The initial gas supply pipeline 12 is connected to the filter 13, the initial gas supply pipeline 12 is connected to the inlet of the compressor 14, the outlet of the compressor 14 is connected to the high-pressure gas pipeline 15, and the high-pressure gas pipeline 15 is equipped with a pressure gauge 16, a flow meter 17, and a gas valve 18;

[0043] The slurry pump 11 is connected to the slurry inlet 20 of the reactor 22, and the high-pressure gas pipeline 15 is connected to the gas inlet 19 of the reactor 22;

[0044] The mineralized product outlet 21 is connected to a buffer tank 23 , and the outlet of the buffer tank 23 is connected to a grouting pipeline 25 , on which a slurry valve 24 is installed.

[0045] The speed of the first screw feeder 6 is controlled by a first variable frequency motor 26 , and the speed of the second screw feeder 8 is controlled by a second variable frequency motor 27 .

[0046] The flow rate of water supply pipeline 9 is 40m 3 / h, the feeding rate of the first screw feeder 6 is 10t / h, the leaching agent silo 7 is loaded with ammonium chloride, and the feeding rate range of the second screw feeder 8 is 0.8t / h. The working pressure of the compressor 14 is 1.5MPa, the initial gas composition is 86% N2 and 14% CO2, and the gas inlet mass flow rate is 1.36kg / s. The reactor 22 is filled with slurry, and the flow direction is gas upward and liquid and solid downward; the reactor 22 is equipped with a multi-stage impeller, and the speed is controlled by the third frequency converter 30 to strengthen the gas-liquid-solid mixing process. The grouting pipeline 25 is also connected to the flushing pipeline 31. When the mineralized CO2 product blocks the pipeline, the flushing pipeline 31 is started for flushing.

[0047] Application method of the fly ash mineralization CO2 and its product grouting system for preventing and controlling coal spontaneous combustion:

[0048] First, start the motors of the first screw feeder 6, the second screw feeder 8, and the pulping and mixing tank 10, open the water supply pipeline 9, and mix the fly ash, additives and water in the pulping and mixing tank;

[0049] Secondly, when the liquid level in the slurry mixing tank 10 reaches a specified height, the slurry pump 11 is turned on to deliver the fly ash slurry to the reactor 22;

[0050] Next, when the reactor 22 is filled with fly ash slurry, the mineralized product outlet 21 is opened to allow it to flow to the buffer tank 23;

[0051] Once again, when the level of the buffer tank liquid 23 reaches the specified height, the slurry valve 24 on the grouting pipeline 25 is opened to inject grout into the goaf;

[0052] Finally, the gas valve 18 on the high-pressure gas pipeline 15 is opened to allow the CO2-containing flue gas to enter the reactor 22 for a mineralization reaction. The overall system is started up, and continuous preparation of a large flow of fly ash slurry, mineralization of CO2 and grouting for fire prevention and extinguishing are achieved.

[0053] Although the price of fly ash per ton varies slightly, the national average price fluctuates around 120 yuan per ton. For example, in a certain mine, the standard coal price is 740 yuan / t, the CO2 selling price is 200 yuan / t, the carbon tax price is 50 yuan / t, and the carbon quota trading price is 58 yuan / t. According to the current carbon trading price of about 50 yuan per ton in my country, the CO2 adsorbed and stored by every 100 tons of fly ash can bring a carbon emission reduction benefit of 500 yuan. The traditional fire prevention and extinguishing technology used in coal mine goafs, the fly ash grouting fire prevention and extinguishing technology costs 150 yuan per cubic meter, and the liquid CO2 direct injection inertization and cooling process costs 210 yuan per ton. After the fly ash slurry mineralization and CO2 storage is combined with goaf fire prevention and extinguishing, every 100 tons of mineralized products used for goaf fire prevention and extinguishing effectively saves 21,000 yuan. The CO2 product of fly ash slurry mineralization can block the oxidation process of the residual coal in the goaf, eliminate the risk of spontaneous combustion of the residual coal in the goaf, ensure the safe production of the mine, significantly improve the production efficiency of the mine, and help increase the production of coal mining enterprises.

[0054] Embodiment 2

[0055] Compared with the first embodiment, the present embodiment is different in that the flow rate of the water supply pipeline 9 is 80m 3 / h, the feeding rate of the first screw feeder 6 is 20t / h, the leaching agent silo 7 is loaded with ammonium acetate, and the feeding rate range of the second screw feeder 8 is 2.2t / h. The working pressure of the compressor 14 is 2MPa, the initial gas composition is 86% N2 and 14% CO2, and the gas inlet mass flow rate is 2.72kg / s. The continuous feeding amount of water and solid in this embodiment is large, and the CO2 mineralization amount in this embodiment is twice that of the CO2 mineralization amount in the first embodiment.

[0056] Although the price of fly ash per ton varies slightly, the national average price fluctuates around 120 yuan per ton. For example, in a certain mine, the standard coal price is 740 yuan / t, the CO2 selling price is 200 yuan / t, the carbon tax price is 50 yuan / t, and the carbon quota trading price is 58 yuan / t. According to the current carbon trading price of about 50 yuan per ton in my country, the CO2 adsorbed and stored by every 100 tons of fly ash can bring a carbon emission reduction benefit of 1,000 yuan. The traditional fire prevention and extinguishing technology used in coal mine goafs, the fly ash grouting fire prevention and extinguishing technology costs 150 yuan per cubic meter, and the liquid CO2 direct injection inertization and cooling process costs 210 yuan per ton. After the fly ash slurry mineralization and CO2 storage is combined with goaf fire prevention and extinguishing, every 100 tons of mineralized products used for goaf fire prevention and extinguishing effectively saves 21,000 yuan. The CO2 product of fly ash slurry mineralization can block the oxidation process of the residual coal in the goaf, eliminate the risk of spontaneous combustion of the residual coal in the goaf, ensure the safe production of the mine, significantly improve the production efficiency of the mine, and help increase the production of coal mining enterprises.

[0057] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A fly ash mineralization CO2 and product prevention and control system for coal spontaneous combustion, characterized by: It comprises a slurry preparation unit (1), a flue gas pretreatment unit (2), a mineralization reaction unit (3), and a slurry perfusion unit (4); The slurry preparation unit (1) comprises a fly ash silo (5), a first screw feeder (6), a leaching agent silo (7), a second screw feeder (8), a water supply pipeline (9), a slurry stirring tank (10), and a slurry pump (11); the fly ash silo (5) is installed at the inlet of the first screw feeder (6), the leaching agent silo (7) is installed at the inlet of the second screw feeder (8), the outlets of the first screw feeder (6), the second screw feeder (8) and the water supply pipeline (9) are all connected to the slurry stirring tank (10), and the outlet of the slurry stirring tank (10) is connected to the top of the mineralization reaction unit (3) through the slurry pump (11); The flue gas pretreatment unit (2) comprises an initial gas supply pipeline (12), a filter (13), a compressor (14), a high-pressure gas pipeline (15), a pressure gauge (16), a flow meter (17), and a gas valve (18); the filter (13) is arranged on the initial gas supply pipeline (12), the initial gas supply pipeline (12) is connected to the inlet of the compressor (14), the outlet of the compressor (14) is connected to the bottom of the initial gas supply pipeline (12) through the high-pressure gas pipeline (15), and the pressure gauge (16), the gas flow meter (17), and the gas valve (18) are installed on the high-pressure gas pipeline (15); The mineralization reaction unit (3) comprises a reactor (22) and a gas inlet (19), a slurry inlet (20), and a mineralized product outlet (21) arranged on the reactor (22); the gas inlet (19) is connected to a high-pressure gas pipeline (15), the slurry inlet (20) is connected to a pipeline of a slurry stirring tank (10), and the mineralized product outlet (21) is located at the bottom of the reactor (22); The slurry injection unit (4) comprises a buffer tank (23), a slurry valve (24), and a grouting pipeline (25); one end of the grouting pipeline (25) is connected to the buffer tank (23), and the other end is connected to the goaf; the buffer tank (23) is connected to the mineralized product outlet (21) through a pipeline; and the slurry valve (24) is arranged on the grouting pipeline (25).

2. A fly ash mineralization CO2 and product prevention and control system for coal spontaneous combustion according to claim 1, characterized in that: The first screw feeder (6) has a rotation speed controlled by a first variable frequency motor (26) to adjust the rate of adding fly ash; The second screw feeder (8) has a rotation speed controlled by a second variable frequency motor (27) to adjust the addition rate of the leaching agent; The water supply pipeline (9) is provided with a liquid valve (28) and a liquid flow meter (29).

3. A fly ash mineralization CO2 and product prevention and control system for coal spontaneous combustion according to claim 1, characterized in that: The flow rate range of the water supply pipeline (9) is 0 to 80 m 3 / h, the feeding rate range of the first screw feeder (6) is 0-20 t / h, and the feeding rate range of the second screw feeder (8) is 0-4 t / h.

4. A fly ash mineralization CO2 and product prevention and control system for coal spontaneous combustion according to claim 1, characterized in that: The operating pressure range of the compressor (14) is 0-2 MPa, and the gas mass flow rate range is 0-4 kg / s.

5. A fly ash mineralization CO2 and product prevention and control system for coal spontaneous combustion according to claim 1, characterized in that: The reactor (22) is filled with slurry, and the flow direction is gas upward and liquid and solid downward; The reactor (22) is equipped with a multi-stage impeller, the rotation speed of which is controlled by a third variable frequency motor (30).

6. A fly ash mineralization CO2 and product prevention and control system for coal spontaneous combustion according to claim 1, characterized in that: The grouting pipeline (25) is also connected to a flushing pipeline (31). When the mineralized CO2 product blocks the pipeline, the flushing pipeline (31) is activated for flushing.

7. The application method of the fly ash mineralization CO2 and product prevention and control of coal spontaneous combustion system according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: Start the motors of the first screw feeder (6), the second screw feeder (8), and the pulping and mixing tank (10), open the water supply pipeline (9), and mix the fly ash, additives, and water in the pulping and mixing tank; Step 2: When the liquid level in the slurry mixing tank (10) reaches a specified height, the slurry pump (11) is turned on to deliver the fly ash slurry to the reactor (22); Step 3: When the reactor (22) is filled with fly ash slurry, the mineralized product outlet (21) is opened to allow the product to flow to the buffer tank (23); Step 4: When the liquid level in the buffer tank (23) reaches a specified height, the slurry valve (24) on the grouting pipeline (25) is opened to inject grout into the goaf; Step 5: Open the gas valve (18) on the high-pressure gas pipeline (15) to allow the CO2-containing flue gas to enter the reactor (22) for a mineralization reaction. The overall system is started up, and continuous preparation of a large flow of fly ash slurry, mineralization of CO2 and grouting for fire prevention and extinguishing are achieved.

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