Underground sealing treatment method for flue gas and fly ash

Abstract

The invention discloses an underground sealing treatment method for flue gas and fly ash, which comprises the following steps: injecting fly ash slurry in a slurry mixing pool into a coal mine goaf through a grouting pump, and injecting methanogenic bacteria liquid stored in a bacteria liquid storage tank into a grouting pipe through a liquid injection pump; coal-fired flue gas in the flue gas storage tank is injected into a coal mine goaf through the air compressor, gas produced by the gas production pipe is separated through the gas separation device, separated methane is fed into the gas storage tank to be stored, separated carbon dioxide is fed into the coal-fired flue gas storage tank, and the coal-fired flue gas is fed into the coal mine goaf. When the methane concentration in the goaf is lower than a set value and the carbon dioxide concentration is higher than a set value, the gas separation device stops working, and the gas production pipe is closed; coal-fired flue gas and coal ash slurry are injected into the goaf of the coal mine, and gas injection and liquid injection are stopped when the gas pressure in the goaf rises to a set safe gas storage threshold value. The coal mine goaf, the coal-fired flue gas and the fly ash which are harmful to the environment are reasonably combined, the problem that the coal mine goaf, the coal-fired flue gas and the fly ash are harmful to the natural environment is solved, the beneficial resource methane fuel is obtained, and the purpose of changing disadvantage into advantage is achieved.

Description

Technical Field

[0001] The present invention relates to the field of carbon dioxide geological storage and solid waste utilization, and relates to a method for carbon dioxide geological storage and bio-production of CH 4 Integrated approach. Background Art

[0002] After the Industrial Revolution, human activities released a large amount of CO 2 greenhouse gases such as CO2 have caused more and more greenhouse effects, thus triggering a series of global climate problems. 2 Greenhouse gas emissions, represented by, are of great significance to alleviating global warming and improving the earth's ecological environment.

[0003] According to the "2023 Global Carbon Emissions Report" released by the International Energy Agency (IEA), global energy-related carbon dioxide emissions in 2023 will increase by 410 million tons compared to 2022, of which coal-fired emissions account for 65%. Coal-fired power plants will produce waste gas and solid waste during the combustion process. Waste gas, also known as flue gas, contains high concentrations of carbon dioxide. After these carbon dioxide are discharged into the atmosphere, they will aggravate the greenhouse effect. Solid waste mainly includes fly ash, which contains a large amount of metal elements, organic matter and minerals. If not properly handled, solid waste will cause long-term pollution to the soil, water and atmospheric environment. Therefore, the utilization of flue gas and fly ash is not only conducive to the efficient utilization of resources and environmental protection, but also conducive to improving economic and social benefits.

[0004] Carbon dioxide geological storage, that is, injecting CO into geological bodies or underground spaces 2 Long-term storage can effectively achieve low-carbon or negative carbon emissions. Generally, conventional geological structures with high pore volumes, such as saline aquifers, depleted oil and gas reservoirs, and unmineable coal seams, are often used as suitable reservoirs for geological storage. A large number of abandoned mines and goafs are generated in the global coal mining process. If these goafs are not properly handled, they will cause ground collapse, rock movement, aquifer damage and other hazards, causing great damage to the environment. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide an underground storage and treatment method for flue gas and fly ash, so as to solve the technical problems of sealing and treating flue gas and fly ash generated by coal combustion and solidification and filling treatment of abandoned mines and goafs generated during coal mining.

[0006] The underground storage treatment method of flue gas and fly ash of the present invention comprises the following steps:

[0007] 1) Drilling gas injection wells, grouting wells and extraction wells on the ground in the coal mine goaf;

[0008] 2) Arrange an air compressor and a flue gas storage tank on the ground, arrange an injection pipe in the gas injection well, and seal the wellhead of the gas injection well; connect the air compressor outlet to the main air pipe, and connect the air compressor inlet to the coal-fired flue gas storage tank;

[0009] Arrange a bacterial liquid storage tank, a slurry mixing tank and a grouting pump on the ground, arrange a grouting pipe in the grouting well, close the wellhead of the grouting well, and connect the inlet of the grouting pipe to the grouting pump; and set up an air injection pump and a liquid injection pump, the inlet of the air injection pump is connected to the smoke storage tank through a pipeline, the outlet of the air injection pump is connected to the grouting pipe through a pipeline, the inlet of the liquid injection pump is connected to the bacterial liquid storage tank through a pipeline, and the outlet of the liquid injection pump is connected to the grouting pipe through a pipeline;

[0010] A gas separation device for separating methane and carbon dioxide from gas stored in the goaf and a gas storage tank for storing methane are arranged on the ground, a methane concentration sensor, a carbon dioxide concentration sensor and a pressure sensor are arranged in the gas production pipe, the gas production pipe is arranged in the gas injection well, and the wellhead of the gas injection well is sealed, the gas outlet of the gas production pipe is connected to the gas inlet of the gas separation device, the methane outlet of the gas separation device is connected to the methane storage tank, and the carbon dioxide outlet of the gas separation device is connected to the coal-fired flue gas storage tank through an intermediate pipeline;

[0011] 3) After the coal-fired flue gas has been dust-removed, it is fed into a flue gas storage tank through a pipeline; fly ash is added into a slurry mixing tank and stirred evenly to form fly ash slurry; the fly ash slurry in the slurry mixing tank is pumped into a grouting pipe by a grouting pump, the methanogenic bacteria liquid stored in the bacteria liquid storage tank is injected into the grouting pipe by an injection pump, and the coal-fired flue gas is injected into the grouting pipe by an air injection pump to adjust the pH value of the fly ash slurry to a range suitable for the reproduction of methanogenic bacteria; when the amount of fly ash slurry injected into the coal mine goaf reaches a set value, the grouting operation is stopped;

[0012] 4) The methane concentration in the gas storage in the coal mine goaf is monitored by a methane concentration sensor. When the methane concentration reaches the mining set value, the coal-fired flue gas in the flue gas storage tank is injected into the coal mine goaf through an air compressor and an air injection pipe. At the same time, the gas in the coal mine goaf enters the gas separation device through the gas production pipe. The gas separation device sends the separated methane to the gas storage tank for storage, and sends the separated carbon dioxide to the coal-fired flue gas storage tank through the intermediate pipeline, and discharges other gases except methane and carbon dioxide into the atmosphere;

[0013] 5) The methane concentration sensor and the carbon dioxide concentration sensor are used to monitor the methane concentration and carbon dioxide concentration in the gas in the coal mine goaf. When the methane concentration is lower than the set value and the carbon dioxide concentration is higher than the set value, the gas separation device stops working and closes the gas production pipe;

[0014] 6) Inject coal smoke and fly ash slurry into the goaf of the coal mine at the same time according to the set flow rate ratio, monitor the gas pressure in the goaf through the pressure sensor, and when the gas pressure rises to the set safe gas storage threshold, stop injecting coal smoke and fly ash slurry into the goaf of the coal mine; and close the main gas pipe and grouting pipe.

[0015] Furthermore, in step 3), the pH value of the fly ash slurry is adjusted to 6.6-7.5.

[0016] Furthermore, the underground storage treatment method of flue gas and fly ash also includes providing a filtering device and a drying device to remove dust and dry the gas before entering the gas separation device.

[0017] Beneficial effects of the present invention:

[0018] 1. The underground storage and treatment method of flue gas and fly ash of the present invention mainly originates from coal-fired power plants, which are usually located in areas with rich coal resources. This makes full use of the geographical location advantages of coal mine goafs and coal-fired power plants, and can significantly reduce the transportation cost of flue gas and fly ash from coal-fired power plants, thereby significantly improving economic benefits while effectively utilizing resources.

[0019] 2. The underground storage and treatment method of flue gas and fly ash of the present invention injects fly ash slurry containing methanogenic bacteria liquid into the goaf. The methanogenic bacteria can produce methane gas by decomposing organic matter contained in coal and fly ash in the goaf. In this way, methane can be extracted while sealing carbon dioxide and fly ash, thereby improving economic benefits.

[0020] 3. The underground storage and treatment method of flue gas and fly ash of the present invention rationally combines the three objects harmful to the natural environment, namely, coal mine goaf, coal-burning flue gas and fly ash. It not only solves the problem of harm to the natural environment caused by coal mine goaf, coal-burning flue gas and fly ash, but also obtains the beneficial resource of methane fuel, thus achieving the purpose of turning disadvantages into advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of the underground storage system for flue gas and fly ash. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0023] As shown in the figure, the underground storage treatment method of flue gas and fly ash in this embodiment includes the following steps:

[0024] 1) Drill gas injection well 1, grouting well 2 and extraction well 3 on the ground facing the coal mine goaf.

[0025] 2) Arrange an air compressor 4 and a flue gas storage tank 5 on the ground, arrange an injection pipe 6 in the injection well, and seal the wellhead of the injection well; connect the air compressor outlet to the main air pipe, and connect the air compressor inlet to the coal-fired flue gas storage tank.

[0026] A bacterial liquid storage tank 7, a slurry mixing tank 8 and a grouting pump 9 are arranged on the ground, a grouting pipe 10 is arranged in the grouting well, and the wellhead of the grouting well is closed, and the inlet of the grouting pipe is connected to the grouting pump; and an air injection pump 11 and a liquid injection pump 12 are provided, the inlet of the air injection pump is connected to the smoke storage tank through a pipeline, the outlet of the air injection pump is connected to the grouting pipe through a pipeline, the inlet of the liquid injection pump is connected to the bacterial liquid storage tank through a pipeline, and the outlet of the liquid injection pump is connected to the grouting pipe through a pipeline.

[0027] A gas separation device 13 for separating methane and carbon dioxide from gas stored in the goaf and a gas storage tank 14 for storing methane are arranged on the ground, a methane concentration sensor 16, a carbon dioxide concentration sensor 17 and a pressure sensor 18 are arranged in a gas production pipe 15, the gas production pipe is arranged in a gas injection well, and the wellhead of the gas injection well is closed, the gas outlet of the gas production pipe is connected to the gas inlet of the gas separation device, the methane outlet of the gas separation device is connected to the methane storage tank, and the carbon dioxide outlet of the gas separation device is connected to the coal-fired flue gas storage tank through an intermediate pipe 19.

[0028] 3) After the coal-fired flue gas has been dust-removed, it is fed into the flue gas storage tank through a pipeline; the fly ash is added to the slurry mixing tank and stirred evenly to form fly ash slurry; the fly ash slurry in the slurry mixing tank is pumped into the grouting pipe by a grouting pump, and the methanogenic bacteria liquid stored in the bacteria liquid storage tank is injected into the grouting pipe by an injection pump. The fly ash slurry is alkaline, and the coal-fired flue gas is injected into the grouting pipe by an injection pump to adjust the pH value of the fly ash slurry to a range suitable for the reproduction of methanogenic bacteria, specifically, to adjust the pH value of the fly ash slurry to 6.6-7.5. When the amount of fly ash slurry injected into the coal mine goaf reaches the set value, the grouting operation is stopped; the specific value of the grouting amount can be determined according to the design of the space volume of the goaf.

[0029] 4) After the fly ash slurry containing methanogenic bacteria liquid is injected into the goaf, the methanogenic bacteria will produce methane gas by decomposing the organic matter contained in the coal and fly ash in the goaf. The methane concentration in the gas storage in the goaf of the coal mine is monitored by a methane concentration sensor. When the methane concentration reaches the mining set value, the coal-burning flue gas in the flue gas storage tank is injected into the goaf of the coal mine through an air compressor and an injection pipe. At the same time, the gas in the goaf of the coal mine enters the gas separation device through the gas production pipe. The gas separation device sends the separated methane to the gas storage tank for storage, and sends the separated carbon dioxide to the coal-burning flue gas storage tank through the intermediate pipeline. The gas separation device discharges other gases except methane and carbon dioxide into the atmosphere.

[0030] 5) The methane concentration sensor and the carbon dioxide concentration sensor are used to monitor the methane concentration and carbon dioxide concentration in the gas in the coal mine goaf. When the methane concentration is lower than the set value and the carbon dioxide concentration is higher than the set value, the gas separation device stops operating and closes the gas production pipe.

[0031] 6) Inject coal smoke and fly ash slurry into the goaf of the coal mine at the same time according to the set flow rate ratio, monitor the gas pressure in the goaf through the pressure sensor, and when the gas pressure rises to the set safe gas storage threshold, stop injecting coal smoke and fly ash slurry into the goaf of the coal mine; and close the main gas pipe and grouting pipe.

[0032] As an improvement to the above-mentioned embodiment, the underground storage treatment method of flue gas and fly ash also includes setting up a filtering device 20 and a drying device 21 to remove dust and dry the gas before entering the gas separation device, which can protect the gas separation device 13.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for underground storage and treatment of flue gas and fly ash, characterized in that: The following steps are involved: 1) Drilling gas injection wells, grouting wells and extraction wells on the ground in the coal mine goaf; 2) Arrange an air compressor and a flue gas storage tank on the ground, arrange an injection pipe in the gas injection well, and seal the wellhead of the gas injection well; connect the air compressor outlet to the main air pipe, and connect the air compressor inlet to the coal-fired flue gas storage tank; Arrange a bacterial liquid storage tank, a slurry mixing tank and a grouting pump on the ground, arrange a grouting pipe in the grouting well, close the wellhead of the grouting well, and connect the inlet of the grouting pipe to the grouting pump; and set up an air injection pump and a liquid injection pump, the inlet of the air injection pump is connected to the smoke storage tank through a pipeline, the outlet of the air injection pump is connected to the grouting pipe through a pipeline, the inlet of the liquid injection pump is connected to the bacterial liquid storage tank through a pipeline, and the outlet of the liquid injection pump is connected to the grouting pipe through a pipeline; A gas separation device for separating methane and carbon dioxide from gas stored in the goaf and a gas storage tank for storing methane are arranged on the ground, a methane concentration sensor, a carbon dioxide concentration sensor and a pressure sensor are arranged in the gas production pipe, the gas production pipe is arranged in the gas injection well, and the wellhead of the gas injection well is sealed, the gas outlet of the gas production pipe is connected to the gas inlet of the gas separation device, the methane outlet of the gas separation device is connected to the methane storage tank, and the carbon dioxide outlet of the gas separation device is connected to the coal-fired flue gas storage tank through an intermediate pipeline; 3) After the coal-fired flue gas has been dust-removed, it is fed into a flue gas storage tank through a pipeline; fly ash is added into a slurry mixing tank and stirred evenly to form fly ash slurry; the fly ash slurry in the slurry mixing tank is pumped into a grouting pipe by a grouting pump, the methanogenic bacteria liquid stored in the bacteria liquid storage tank is injected into the grouting pipe by an injection pump, and the coal-fired flue gas is injected into the grouting pipe by an air injection pump to adjust the pH value of the fly ash slurry to a range suitable for the reproduction of methanogenic bacteria; when the amount of fly ash slurry injected into the coal mine goaf reaches a set value, the grouting operation is stopped; 4) The methane concentration in the gas storage in the coal mine goaf is monitored by a methane concentration sensor. When the methane concentration reaches the mining set value, the coal-fired flue gas in the flue gas storage tank is injected into the coal mine goaf through an air compressor and an air injection pipe. At the same time, the gas in the coal mine goaf enters the gas separation device through the gas production pipe. The gas separation device sends the separated methane to the gas storage tank for storage, and sends the separated carbon dioxide to the coal-fired flue gas storage tank through the intermediate pipeline, and discharges other gases except methane and carbon dioxide into the atmosphere; 5) The methane concentration sensor and the carbon dioxide concentration sensor are used to monitor the methane concentration and carbon dioxide concentration in the gas in the coal mine goaf. When the methane concentration is lower than the set value and the carbon dioxide concentration is higher than the set value, the gas separation device stops working and closes the gas production pipe; 6) Inject coal smoke and fly ash slurry into the goaf of the coal mine at the same time according to the set flow rate ratio, monitor the gas pressure in the goaf through the pressure sensor, and when the gas pressure rises to the set safe gas storage threshold, stop injecting coal smoke and fly ash slurry into the goaf of the coal mine; and close the main gas pipe and grouting pipe.

2. The underground storage and treatment method for flue gas and fly ash according to claim 1, characterized in that: In the step 3), the pH value of the fly ash slurry is adjusted to 6.6-7.

5.

3. The underground storage and treatment method of flue gas and fly ash according to claim 1, characterized in that: It also includes setting up a filtering device and a drying device to remove dust and dry the gas before entering the gas separation device.

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