A method for plugging and optimizing pores in the middle-layer structure of coal and rock

Abstract

The present invention relates to the technical field of coal and rock stratum reinforcement, and particularly to a method for plugging and optimizing pores in the middle-layer structure of coal and rock. A method for plugging and optimizing pores in the middle-layer structure of coal and rock includes the following steps: polishing and drying the surface of the coal sample; adding additive A to mine water to prepare standard solution A; adding additive B to deionized water to prepare standard solution B; taking out the dried coal sample and placing it in a device filled with standard solution A, standing still, observing that no bubbles overflow on the liquid surface within 30 s, closing the device, taking it out and placing it in a cool place to stand still; placing the sample standing still in the cool place in a clamp, dripping standard solution B at both ends of the clamp, when no liquid flows out of the liquid outlet pipe within 1 min, wiping the liquid on the surface, repeating 2 to 3 times, and then placing it in a cool place to stand still. The present invention uses mine water as the base material, reduces the content of mine water, thereby reducing the physicochemical action of mine water eroding coal and rock, and enhancing the integrity and stability inside the coal and rock.

Description

Technical Field

[0001] The present invention relates to the technical field of coal and rock stratum reinforcement, and particularly to a method for plugging and optimizing pores in the middle-layer structure of coal and rock. Background Art

[0002] In the primary energy production and consumption structure of our country, coal occupies a dominant position. With the continuous optimization of the primary energy consumption structure, although the proportion of coal is constantly decreasing, the total amount is still increasing.

[0003] During the coal mining process, the excavation of coal roadways and the drilling along the coal seams will induce stress concentration, which will further lead to coal and rock damage and the formation of fractures, and gradually expand to form a fracture network, which may form a leakage and oxygen transmission pipeline, increasing risks. And due to the continuous erosion of mine water, the risks of water seepage and water inrush accidents are gradually increasing.

[0004] At the present stage, to solve the above problems, the patent with the application number CN202210182908.3 discloses "a toughened spray plugging and airtight material and its construction process". This material is composed of calcium oxide, silicon dioxide, aluminum oxide, iron oxide, an expanding agent, a flame retardant, a polymer emulsion and water. It is sprayed on the surfaces of coal and rock masses, metals, woods, etc., with high adhesion, closing surface fractures, blocking air leakage and isolating air. The patent with the application number CN202111294595.2 discloses a paste quick-setting material for coal and rock fracture-pore consolidation and its preparation method. This material is a quick-strength solidifying material with a short setting time and easy to stack and form in plugging coal and rock fractures.

[0005] Although the above patents have repaired the fracture network of coal and rock strata to a certain extent and reduced the permeability of coal and rock. However, coal and rock are porous materials, and micropores and mesopores are the main adsorption sites for gases and liquids, and fractures mainly serve as the migration channels for fluids in coal and rock. For these plugging materials, such as concrete slurry, polymer emulsion coatings, etc., each has its own disadvantages. Among them, the concrete slurry has a large density and a large viscosity coefficient, and it is difficult to penetrate into the deep fracture structure of coal and rock. If the grouting pressure is increased, a new fracture network may be formed. And the polymer emulsion coating often can only form a cured layer on the surface of coal and rock, and it still cannot plug and optimize the fracture network from the internal structure of coal. Therefore, a method for plugging and optimizing pores in the middle-layer structure of coal and rock is needed to solve the above technical problems Summary of the Invention

[0006] The purpose of the present application is to provide a method for plugging and optimizing pores in the middle-layer structure of coal and rock, using mine water as the base material, reducing the physical and chemical erosion of mine water on coal and rock while overcoming the problem that the existing plugging base materials cannot penetrate into the pore network inside the coal and rock for plugging, so as to solve or alleviate the problems existing in the above prior art.

[0007] To achieve the above object, the present application provides the following technical solutions:

[0008] A method for plugging and optimizing pores in the middle-layer structure of coal and rock, comprising the following steps:

[0009] (1) Pretreatment: Grind the surface of the coal sample and dry the ground coal sample.

[0010] (2) Prepare standard solution A and standard solution B. Add additive A to mine water to prepare standard solution A; add additive B to deionized water to prepare standard solution B.

[0011] (3) Take out the dried coal sample from step (1), place it in a vacuum saturation device filled with standard solution A, let it stand for 4 - 6 h, observe that no bubbles overflow on the liquid surface within 30 s, close the vacuum saturation device, take out the saturated sample, dry the surface liquid and place it in a cool place to stand.

[0012] (4) Place the sample that has stood in a cool place in step (3) in a holder, drip standard solution B at both ends of the holder. When no liquid flows out of the liquid outlet pipe within 1 min, dry the surface liquid, repeat 2 - 3 times, and then place it in a cool place to stand.

[0013] Preferably, in step (1), place the ground coal sample in an oven and dry it at 60 °C for 4 - 8 h.

[0014] Preferably, in step (2), the additive A is one or more of potassium sulfate, calcium chloride, magnesium chloride, and sodium bicarbonate. The main function of the standard solution A is to balance the original ions in the mine water and increase the electrolytic degree of the original mine water solution.

[0015] More preferably, the mass ratio of the additive A to the mine water is 1:10 - 15.

[0016] Preferably, in step (2), the additive B is one or more of magnesium sulfate, sodium bicarbonate, sodium silicate, ethylenediamine, tartaric acid, metaaluminum acid, sodium chloride, and sodium sulfate. As a penetrating crystallization liquid, the standard B liquid can quickly react with the standard A liquid to generate a complex precipitate of 3CaO·Al2O3·3CaSO4·32H2O after entering the pore structure filled with the standard A liquid, thereby sealing and optimizing the internal fissure network. Among them, magnesium sulfate, sodium bicarbonate, sodium chloride, and sodium sulfate provide the main raw materials for the penetrating crystallization reaction with the standard A liquid, while ethylenediamine, tartaric acid, and metaaluminum acid, as chelating agents, can adhere to the surface of the complex precipitate, resulting in electrostatic interactions at the negative charge sites on the surface of the complex precipitate of sodium ions, potassium ions, and magnesium ions, thereby forming an adsorption layer on the surface of the precipitate. It can also change the ion distribution of sodium ions, potassium ions, silicate ions, etc. on the surface of the complex precipitate, thereby changing the growth direction of the complex precipitate to make it close to columnar crystals and more evenly distributed in the pore network of coal rock.

[0017] Further preferably, the mass ratio of the additive B to deionized water is 1:10 - 15.

[0018] Preferably, in step (3), take out the coal sample dried in step (1), place it in a ZK-270 vacuum saturation device filled with the standard A liquid. The temperature in the vacuum saturation device is 20 - 30°C, the pumping rate is 1 ± 0.2 L / S, and its vacuum degree is 0 - 0.1 MPa. Let it stand for 4 - 6 h, observe that no bubbles overflow on the liquid surface within 30 s, close the vacuum saturation device, take out the saturated sample, dry the surface liquid, and place it in a cool place at 15 - 23°C for 1 - 2 h.

[0019] Preferably, in step (4), place the sample standing in the cool place in step (3) in a TY-5A holder, drip the standard B liquid at both ends of the holder. When no liquid flows out of the liquid outlet pipe within 1 min, dry the surface liquid, repeat 2 - 3 times, and then place it in a cool place at 15 - 23°C for 2 - 3 h.

[0020] Beneficial effects:

[0021] (1) Compared with the traditional method, the present invention uses a relatively small pressure slightly higher than atmospheric pressure to ensure the integrity of the coal sample during the test while minimizing the emergence of new fissures as much as possible. The solvents of the standard A liquid and the standard B liquid are mine water and deionized water respectively to ensure that the standard A liquid and the standard B liquid have lower viscous resistance in coal rock, so that they have stronger penetration performance and can penetrate into the deep fissures of the coal sample.

[0022] (2) The traditional direct slurry injection method is to directly inject the pre-prepared slurry into the coal sample under pressure or spray it on the surface of the coal sample. The plugging principle is to plug from the outside to the inside, so that the slurry cannot enter the deep fissure network of the coal and rock for solidification plugging. However, the step-by-step liquid injection method adopted in the present invention enables the standard liquid A and the standard liquid B to enter the specimen respectively. The standard liquid A and the standard liquid B generate complex-precipitates in the pore network inside the coal and rock, and optimize the plugging of the deep pore network of the coal and rock from the inside, fundamentally solving the problem, rather than temporarily forming a solidified layer on the surface of the coal sample.

[0023] (3) The present invention uses mine water as the base material, reducing the content of mine water in the underground mine, thereby reducing the physical and chemical effects of mine water eroding the coal and rock, and further enhancing the integrity and stability inside the coal and rock. In addition, the remaining mine water from the experiment can be recycled, avoiding the complexity of making the slurry and making the plugging optimization process more simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The specification drawings forming a part of this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation to this application. Among them:

[0025] Figure 1 is a flow chart of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The present application will be described in detail below with reference to the drawings and in conjunction with the embodiments. Each example is provided by way of explanation of the present application rather than a limitation of the present application. In fact, those skilled in the art will clearly understand that modifications and variations can be made to the present application without departing from the scope or spirit of the present application. For example, the features shown or described as part of one embodiment can be used in another embodiment to yield yet another embodiment. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the embodiments of the present invention shall fall within the scope of protection of the embodiments of the present invention.

[0027] A method for optimizing the plugging of pores in the middle layer structure of coal and rock includes the following steps:

[0028] (1) Pretreatment: Grind the surface of the coal sample, and place the ground coal sample in a drying oven and dry it at 60 °C for 4 - 8 h.

[0029] (2) Prepare standard liquid A and liquid B. Add additive A to the mine water to prepare standard liquid A; additive A is one or more of potassium sulfate, calcium chloride, magnesium chloride, and sodium bicarbonate, and the mass ratio of additive A to the mine water is 1:10 - 15. The main function of the standard liquid A is to balance the original ions in the mine water and increase the electrolytic degree of the original mine water solution.

[0030] Additive B is added to deionized water to prepare standard solution B; Additive B is one or more of magnesium sulfate, sodium bicarbonate, sodium silicate, ethylenediamine, tartaric acid, metaaluminum acid, sodium chloride, and sodium sulfate. The mass ratio of additive B to deionized water is 1:10 - 15. As a permeable crystallization liquid, standard solution B can quickly react with standard solution A to generate a complex precipitate of 3CaO·Al2O3·3CaSO4·32H2O and then block and optimize the internal crack network after entering the pore structure filled with standard solution A. Among them, magnesium sulfate, sodium bicarbonate, sodium chloride, and sodium sulfate provide the main raw materials for the permeable crystallization reaction with standard solution A, while ethylenediamine, tartaric acid, and metaaluminum acid, as chelating agents, can adhere to the surface of the complex precipitate, resulting in electrostatic interactions at the negative charge sites on the surface of the complex precipitate of sodium ions, potassium ions, and magnesium ions, thereby forming an adsorption layer on the surface of the precipitate. It can also change the ion distribution of sodium ions, potassium ions, silicate ions, etc. on the surface of the complex precipitate, thereby changing the growth direction of the complex precipitate to make it close to columnar crystals and more evenly distributed in the pore network of coal rock.

[0031] (3) Take out the coal sample dried in step (1), place it in a ZK-270 vacuum saturation device filled with standard solution A. The temperature in the vacuum saturation device is 20 - 30 °C, the pumping rate is 1 ± 0.2 L / S, and its vacuum degree is 0 - 0.1 MPa. Let it stand for 4 - 6 h. Observe that no bubbles overflow on the liquid surface within 30 s, then close the vacuum saturation device, take out the saturated sample, dry the surface liquid, and place it in a cool place at 15 - 23 °C for 1 - 2 h.

[0032] (4) Place the sample standing in the cool place in step (3) in a TY-5A clamp, drip and infiltrate standard solution B at both ends of the clamp. When no liquid flows out of the liquid outlet pipe within 1 min, dry the surface liquid, repeat 2 - 3 times, and then place it in a cool place at 15 - 23 °C for 2 - 3 h.

[0033] Example 1

[0034] A method for blocking and optimizing the pores in the middle layer structure of coal rock, comprising the following steps:

[0035] (1) Pretreatment: Grind the surface of the coal sample, and place the ground coal sample in a drying oven to dry at 60 °C for 4 - 8 h.

[0036] (2) Prepare standard solution A and standard solution B. Add additive A to mine water to prepare standard solution A. The composition of standard solution A includes 92.5 wt% of mine water, 1.5 wt% of potassium sulfate, 2.3 wt% of calcium chloride, 1.7 wt% of magnesium chloride, and 2 wt% of sodium bicarbonate;

[0037] Add additive B to deionized water to prepare standard solution B; wherein, the composition of standard solution B includes 91.8 wt% of deionized water, 0.8 wt% of magnesium sulfate, 1.3 wt% of sodium silicate, 2.4 wt% of sodium chloride, 0.2 wt% of sodium aluminate, 0.1 wt% of tartaric acid, 0.3 wt% of ethylenediamine, 1.7 wt% of sodium bicarbonate, and 1.4 wt% of sodium sulfate.

[0038] (3) Take out the dried coal sample, place it in the ZK-270 vacuum saturation device filled with standard solution A, and ensure that the temperature in the vacuum saturation device is between 20 and 30 °C, the pumping rate is about 1 L / S (between 0.9 and 1 L / S), and the vacuum degree is between 0 and 0.1 MPa. Let the coal sample stand in this vacuum saturation device for 4 to 6 h. When no bubbles overflow from the liquid surface within 30 s, close the vacuum saturation device. Take out the saturated sample, dry the surface liquid, and place it in a cool place at 15 to 23 °C for 1 to 2 h.

[0039] (4) Place the sample standing in the cool place in step (3) in the TY-5A holder (hereinafter all referred to as the holder), drip standard solution B at both ends of the holder. When no liquid flows out of the liquid outlet pipe within 1 min, close the device, dry the surface liquid, repeat this 2 to 3 times, and then place it in a cool place at 15 to 23 °C for 2 to 3 h. The flow chart is as Figure 1 shown.

[0040] Comparative Example 1

[0041] A method for optimizing the pore blocking of the middle-layer structure of coal and rock includes the following steps:

[0042] (1) Pretreatment: Grind the surface of the coal sample, and place the ground coal sample in an oven to dry at 60 °C for 4 to 8 h.

[0043] (2) Take out the dried coal sample, place it in the ZK-270 vacuum saturation device filled with mine water, and ensure that the temperature in the device is maintained between 20 and 30 °C, the pumping rate is about 1 L / S, and the vacuum degree is between 0 and 0.1 MPa. Let it stand for 4 to 6 h. When no bubbles overflow from the liquid surface within 30 s, close the vacuum saturation device. Take out the saturated sample, dry the surface liquid, and place it in a cool place for 1 to 2 h.

[0044] (3) Place the sample in the holder and drip deionized water solution at both ends of the TY-5A holder (hereinafter all referred to as the holder). When no liquid flows out of the liquid outlet pipe within 1 min, close the device, dry the surface liquid, repeat this 2 to 3 times, and then place it in a cool place at 15 to 23 °C for 2 to 3 h.

[0045] Comparative Example 2

[0046] A method for plugging and optimizing pores in the middle-layer structure of coal and rock, comprising the following steps:

[0047] (1) Pretreatment: Grind the surface of the coal sample, and place the ground coal sample in a drying oven to dry at 60 °C for 4 - 8 h.

[0048] (2) Prepare standard solution A and standard solution B. Add additive A to mine water to prepare standard solution A. The composition of standard solution A includes 92.5 wt% of mine water, 1.5 wt% of potassium sulfate, 2.3 wt% of calcium chloride, 1.7 wt% of magnesium chloride, and 2 wt% of sodium bicarbonate.

[0049] (3) Take out the dried coal sample, place it in a ZK-270 vacuum saturation device filled with standard solution A, and ensure that the temperature in the device is maintained between 20 - 30 °C, the pumping rate is about 1 L / S, and the vacuum degree is between 0 - 0.1 MPa. Let it stand for 4 - 6 h. When no bubbles overflow on the liquid surface within 30 s, close the vacuum saturation device. Take out the saturated sample, dry the surface liquid, and place it in a cool place at 15 - 23 °C for 1 - 2 h.

[0050] (4) Place the sample in a holder, drip deionized aqueous solution at both ends of the TY-5A holder (hereinafter referred to as the holder for short). When no liquid flows out of the liquid outlet pipe within 1 min, close the device, dry the surface liquid, repeat this 2 - 3 times, and then place it in a cool place at 15 - 23 °C for 2 - 3 h.

[0051] Comparative Example 3

[0052] A method for plugging and optimizing pores in the middle-layer structure of coal and rock, comprising the following steps:

[0053] (1) Pretreatment: Grind the surface of the coal sample, and place the ground coal sample in a drying oven to dry at 60 °C for 4 - 8 h.

[0054] (2) Add additive B to deionized water to prepare standard solution B; wherein, the composition of standard solution B includes 91.8 wt% of deionized water, 0.8 wt% of magnesium sulfate, 1.3 wt% of sodium silicate, 2.4 wt% of sodium chloride, 0.2 wt% of sodium metaaluminate, 0.1 wt% of tartaric acid, 0.3 wt% of ethylenediamine, 1.7 wt% of sodium bicarbonate, and 1.4 wt% of sodium sulfate.

[0055] (3) Take out the dried coal sample, place it into the ZK-270 vacuum saturation device filled with mine water solution, ensure that the temperature inside the device remains between 20 and 30 °C, the air extraction rate is about 1 L / S and the vacuum degree is between 0 and 0.1 MPa, let it stand for 4 to 6 h. When no bubbles overflow on the liquid surface within 30 s, close the vacuum saturation device. Take out the saturated sample, dry the liquid on the surface and place it in a cool place at 15 to 23 °C for 1 to 2 h.

[0056] (4) Place the sample into the holder and drip standard solution B at both ends of the TY-5A holder (hereinafter all referred to as the holder). When no liquid flows out of the liquid outlet pipe within 1 min, close the device, dry the liquid on the surface. Repeat this 2 to 3 times, and then place it in a cool place at 15 to 23 °C for 2 to 3 h.

[0057] Detection and analysis

[0058] Perform a result determination test on the methods of the above-mentioned examples and comparative examples. The results of the permeability are shown in Table 1.

[0059] Table 1 Test results of examples and comparative examples

[0060]

[0061] In Comparative Example 1, the liquid placed in the vacuum saturation device is mine water, and the liquid used for the dripping infiltration test is deionized water.

[0062] Compared with Comparative Example 1, Comparative Example 2 changed the type of liquid placed in the vacuum saturation device (standard solution A). As can be seen from Table 1, the vacuum saturation time of Comparative Example 2 is significantly lower than that of Comparative Example 1. The permeability of Comparative Example 2 decreased by about 32.41% compared with Comparative Example 1, and the porosity decreased by about 18.34% compared with Comparative Example 1.

[0063] Comparative Example 3 changed the type of liquid used for dripping infiltration (standard solution B). As can be seen from Table 1, compared with Comparative Example 1, the vacuum saturation time of Comparative Example 3 did not significantly shorten, but the time used for the dripping infiltration test was significantly reduced. The permeability decreased by about 32.25%, and the porosity decreased by about 15.52%.

[0064] Compared with Comparative Example 1, in Example 1, the types of liquids placed in the vacuum saturation device (standard A liquid) and the types of liquids used for the drip infiltration test (standard B liquid) were changed simultaneously. As can be seen from Table 1, compared with Comparative Example 1, both the vacuum saturation time and the time used for the drip infiltration experiment in Example 1 were significantly reduced. Moreover, the reduction rate of Example 1 in terms of permeability was about 77.78%, and the reduction rate in terms of porosity was about 50.97%, which was significantly better than that of the comparative example. Therefore, the method for optimizing the pores in the middle layer structure of coal rock provided by the present invention can generate complex precipitates from the inside while not damaging the external pore network of the coal rock, thereby achieving a better plugging effect.

[0065] The present invention adopts a step-by-step liquid injection method to separately introduce the standard A liquid and the standard B liquid into the interior of the specimen. The standard A liquid and the standard B liquid generate complex-precipitates in the pore network inside the coal rock, completing the optimized plugging of the deep pore network of the coal rock from the inside, fundamentally solving the problem, rather than temporarily forming a solidified layer on the surface of the coal sample.

[0066] In the present invention, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0067] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for plugging and optimizing pores in the middle-layer structure of coal and rock, characterized in that, It includes the following steps: (1) Pretreatment: polish the surface of the coal sample and dry the polished coal sample; (2) Prepare standard solution A and standard solution B. Add additive A to mine water to prepare standard solution A; add additive B to deionized water to prepare standard solution B. The additive A is one or more of potassium sulfate, calcium chloride, magnesium chloride, and sodium bicarbonate; the additive B is magnesium sulfate, sodium bicarbonate, sodium silicate, sodium sulfate, and a chelating agent, and the chelating agent is one or more of ethylenediamine, tartaric acid, and meta-aluminum acid; (3) Take out the dried coal sample in step (1), place it in a vacuum saturation device filled with standard solution A, let it stand for 4 - 6 h, observe that no bubbles overflow on the liquid surface within 30 s, close the vacuum saturation device, take out the saturated sample, dry the surface liquid, and place it in a cool place to stand; (4) Place the sample standing in the cool place in step (3) in a holder, drip standard solution B at both ends of the holder. When no liquid flows out of the liquid outlet pipe within 1 min, dry the surface liquid, repeat 2 - 3 times, and then place it in a cool place to stand.

2. The method for optimizing the pores in the middle layer structure of coal and rock according to claim 1, characterized in that, In step (1), place the polished coal sample in an oven and dry it at 60 °C for 4 - 8 h.

3. The method for optimizing the pores in the middle-layer structure of coal and rock according to claim 1, characterized in that, The mass ratio of the additive A to the mine water is 1:10 - 15.

4. The method for plugging and optimizing pores in the middle-layer structure of coal and rock according to claim 1, characterized in that, The mass ratio of the additive B to the deionized water is 1:10 - 15.

5. The method for plugging and optimizing pores in the middle-layer structure of coal and rock according to claim 1, characterized in that, In step (3), take out the dried coal sample in step (1), place it in a ZK-270 vacuum saturation device filled with standard solution A. The temperature in the vacuum saturation device is 20 - 30 °C, the air extraction rate is 1 ± 0.2 L / S, and its vacuum degree is 0 - 0.1 MPa. Let it stand for 4 - 6 h, observe that no bubbles overflow on the liquid surface within 30 s, close the vacuum saturation device, take out the saturated sample, dry the surface liquid, and place it in a cool place at 15 - 23 °C to stand for 1 - 2 h.

6. The method for optimizing the pores in the middle layer structure of coal and rock according to claim 1, characterized in that, In step (4), place the sample standing in the cool place in step (3) in a TY-5A holder, drip standard solution B at both ends of the holder. When no liquid flows out of the liquid outlet pipe within 1 min, dry the surface liquid, repeat 2 - 3 times, and then place it in a cool place at 15 - 23 °C to stand for 2 - 3 h.

Images