Preparation method of coal gangue-based high-porosity mine geothermal development filling material

Abstract

The invention discloses a preparation method of a coal gangue-based high-porosity mine geothermal development filling material, which comprises the following steps: crushing coal gangue into aggregates in a certain particle size range, screening the aggregates into three particle size ranges, putting the aggregates in the three particle size ranges into a stirring container according to a ratio, adding a certain amount of alkaline activated water, stirring until the aggregates are completely stirred, and cooling to room temperature to obtain the coal gangue-based high-porosity mine geothermal development filling material. And adding quantitative water, quantitative cement and quantitative water reducing agent, continuously stirring, pouring out, and tamping layer by layer to obtain the high-porosity mine geothermal development filling material. The prepared filling material is high in porosity, good in water permeability, high in bearing capacity and suitable for occasions of underground filling mining and geothermal exploitation comprehensive utilization.

Description

Technical Field

[0001] The present invention relates to the technical field of resource utilization of coal mine solid waste, and specifically relates to a preparation method of a gangue-based high-porosity mine geothermal development filling material. Background Art

[0002] In China, the geothermal resources in the main coal-bearing areas are rich in thermal reserves. The large-scale energy storage and geothermal utilization in coal fields will become the main direction of coal field geothermal research and development. By using coal mine filling mining, an underground heat storage layer can be constructed while developing coal, and the coordinated development of geothermal and coal resources has broad technical prospects. In filling mining, traditional filling materials are not suitable for the coordinated mining of coal and geothermal with water as the heat exchange medium due to their low porosity and poor water permeability. Summary of the Invention

[0003] The purpose of the present invention is to provide a preparation method of a gangue-based high-porosity mine geothermal development filling material. The prepared filling material has good water permeability and high bearing capacity, and is suitable for the coordinated operation mode of geothermal development and filling mining.

[0004] The technical solution adopted by the present invention: A preparation method of a gangue-based high-porosity mine geothermal development filling material, comprising:

[0005] Step S1: Crush 100 parts of gangue into aggregates with a particle size of 2.36 - 13.2 mm, and screen them into fine aggregates with a particle size of 2.36 - 4.75 mm, medium aggregates with a particle size of 4.75 - 9.5 mm, and coarse aggregates with a particle size of 9.5 - 13.2 mm. Then, put the three kinds of aggregates into a stirring container according to a certain ratio, and the proportion of medium aggregates is the largest among the three kinds of aggregates;

[0006] Step S2: Add 2.07 - 2.73 parts of alkaline activated water with a pH value of 10.5 - 11.5 to the stirrer, and stir at a speed of 120 r / min for 2 minutes to uniformly wet the surface of the aggregates;

[0007] Step S3: Add 4.83 - 6.37 parts of water, 18 - 26 parts of cement, and 0.17 - 0.19 parts of water reducer, stir at a speed of 150 r / min for 3 minutes, and then pour out the material and compact it to obtain a high-porosity mine geothermal development filling material.

[0008] As a further improvement of the present invention, in step S1, the ratios of the fine aggregates, medium aggregates, and coarse aggregates are divided into four kinds, which are 0:1:0, 0.05:0.85:0.10, 0.10:0.70:0.20, and 0.15:0.55:0.30 respectively.

[0009] As a further improvement of the present invention, in step S2, the alkaline activated water is a 0.5 - 1.5 mol / L NaOH solution.

[0010] As a further improvement of the present invention, in step S3, the cement grade is Portland cement of 425 or above.

[0011] As a further improvement of the present invention, in step S3, the water reducer is an aliphatic water reducer.

[0012] As a further improvement of the present invention, in step S3, the layered ramming method is adopted. For every 50 mm increase in the new accumulation thickness of the mixture, it needs to be rammed 20 - 30 times.

[0013] The beneficial effects of the present invention are as follows:

[0014] (1) The present invention mixes three kinds of aggregates made from coal gangue in proportion, with the medium - sized particles having the largest proportion. Through the three - level aggregate gradation (fine / medium / coarse) and the ratio design dominated by medium - sized aggregates, a stable pore structure can be formed, which is beneficial to the penetration of geothermal fluid and heat exchange.

[0015] (2) The coal - gangue - based high - porosity mine geothermal development filling material has high mechanical strength and good supporting effect on the overlying strata, which can prevent the damage of the overlying strata, ensure the sealing of the water - storage and heat - extraction layer, and avoid the cross - pollution between the heat - extraction medium and groundwater.

[0016] (3) By adding a certain proportion of alkaline activated water, the alkaline activated water can activate the surface activity of coal gangue, enhance the bonding with cement, and improve the stability of the filling material.

[0017] (4) The coal - gangue - based high - porosity mine geothermal development filling material has good water - permeability, can construct a highly permeable water - storage layer in the goaf of the coal mine, eliminates the need for buried - pipe heat extraction, and reduces the operation and maintenance costs.

[0018] (5) Using coal gangue to prepare the filling material can consume the solid waste in the mine, reduce the material preparation cost, and protect the ecological environment of the mining area. Description of the Drawings

[0019] Figure 1 is a physical diagram of the coal - gangue - based high - porosity mine geothermal development filling material prepared by the method of the present invention; Detailed Embodiments

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present invention.

[0021] The present invention provides a preparation method of a coal gangue-based high-porosity filling material for mine geothermal development, aiming to produce a filling material with good water permeability and certain mechanical strength. The following introduces its specific production process through examples.

[0022]

Example 1

[0023] Take 100 parts of gangue and crush it into a particle size of 4.75 - 9.5 mm. Place the crushed gangue in a stirring device; add 2.45 parts of 0.5 - 1.5 mol / L NaOH alkaline activation aqueous solution and stir for 2 minutes; then add 23.34 parts of 425# cement, 5.72 parts of water, and 0.19 part of aliphatic series water reducer; continue to stir for 3 minutes and then pour out the mixed material. After ramming, a coal gangue-based high-porosity filling material is obtained.

[0024]

Example 2

[0025] Take 100 parts of gangue and crush it into a particle size of 2.36 - 13.2 mm, where the proportion of 2.36 - 4.75 mm is 10%, the proportion of 4.75 - 9.5 mm is 85%, and the proportion of 9.5 - 13.2 mm is 5%. Place the crushed gangue in a stirring device; add 2.32 parts of 0.5 - 1.5 mol / L NaOH alkaline activation aqueous solution and stir for 2 minutes; then add 22.1 parts of 425# cement, 5.42 parts of water, and 0.18 part of aliphatic series water reducer; continue to stir for 3 minutes and then pour out the mixed material. After ramming, a coal gangue-based high-porosity filling material is obtained.

[0026]

Example 3

[0027] Take 100 parts of gangue and crush it into a particle size of 2.36 - 13.2 mm, where the proportion of 2.36 - 4.75 mm is 20%, the proportion of 4.75 - 9.5 mm is 70%, and the proportion of 9.5 - 13.2 mm is 10%. Place the crushed gangue in a stirring device; add 2.19 parts of 0.5 - 1.5 mol / L NaOH alkaline activation aqueous solution and stir for 2 minutes; then add 20.8 parts of 425# cement, 5.1 parts of water, and 0.17 part of aliphatic series water reducer; continue to stir for 3 minutes and then pour out the mixed material. After ramming, a coal gangue-based high-porosity filling material is obtained.

[0028]

Example 4

[0029] Take 100 parts of gangue and crush it into a particle size of 2.36 - 13.2 mm, where the proportion of 2.36 - 4.75 mm is 30%, the proportion of 4.75 - 9.5 mm is 55%, and the proportion of 9.5 - 13.2 mm is 15%. Place the crushed gangue in a stirring device; add 2.45 parts of 0.5 - 1.5 mol / L NaOH alkaline activation aqueous solution and stir for 2 minutes; then add 23.34 parts of 425# cement, 5.72 parts of water, and 0.19 parts of aliphatic series water reducer; continue to stir for 3 minutes and then pour out the mixed material. After ramming, a coal gangue-based high-porosity filling material is obtained.

[0030] After the coal gangue-based high-porosity filling material is made, performance tests need to be carried out. The test methods include the 28-day uniaxial compressive strength, splitting tensile strength, porosity (tested by the immersion method), and water permeability coefficient of the coal gangue-based high-porosity filling material for mine geothermal development. Table 1 shows the test results.

[0031] Table 1

[0032] Group 28-day compressive strength / MPa 28-day splitting tensile strength / MPa Porosity / % <![CDATA[Permeability coefficient / mm·s -1 > Example 1 8.40 1.62 13.03 48.96 Example 2 4.43 1.01 15.26 66.39 Example 3 2.80 0.85 15.59 68.02 Example 4 6.00 1.15 15.61 43.97

[0033] It is found from the above experimental results that the coal gangue-based high-porosity filling material for mine geothermal development prepared by the technology of the present invention has a 28-day compressive strength of 2.80 - 8.40 MPa, which can meet the requirements of the coal mine filling support performance; the water permeability coefficient is greater than 40 mm / s, and it has excellent pore connectivity and water permeability ability.

[0034] The above has described the embodiments of the present invention in detail with reference to the drawings. However, the present invention is not limited to this. Various changes that can be made within the knowledge of those skilled in the art without departing from the gist of the present invention are within the protection scope of the claims of the present invention.

Claims

1. A preparation method of a coal gangue-based high-porosity filling material for mine geothermal development, characterized in that, Including: Step S1: Crush 100 parts of coal gangue into aggregates with a particle size of 2.36 - 13.2 mm, and screen them into fine aggregates with a particle size of 2.36 - 4.75 mm, medium aggregates with a particle size of 4.75 - 9.5 mm, and coarse aggregates with a particle size of 9.5 - 13.2 mm. Then, put the aggregates of the three particle sizes into a mixing container according to a certain ratio, and the proportion of medium aggregates is the largest among the three types of aggregates. Step S2: Add 2.07 - 2.73 parts of alkaline activated water with a pH value of 10.5 - 11.5 to the mixer, and stir at a speed of 120 r / min for 2 minutes to uniformly moisten the surface of the aggregates. Step S3: Add 4.83 - 6.37 parts of water, 18 - 26 parts of cement, and 0.17 - 0.19 parts of water reducer, stir at a speed of 150 r / min for 3 minutes, then pour out the material, and obtain the filling material for high - porosity mine geothermal development after ramming.

2. The preparation method of the gangue-based high-porosity mine geothermal development filling material according to claim 1, characterized in that, In step S1, the ratios of the fine aggregates, medium aggregates, and coarse aggregates are divided into four types, which are 0:1:0, 0.05:0.85:0.10, 0.10:0.70:0.20, and 0.15:0.55:0.30 respectively.

3. The preparation method of the gangue-based high-porosity mine geothermal development filling material according to claim 1, characterized in that In step S2, the alkaline activated water is 0.5 - 1.5 mol / L NaOH solution.

4. The preparation method of the gangue-based high-porosity mine geothermal development filling material according to claim 1, characterized in that In step S3, the cement grade is Portland cement with a grade of 425 or above.

5. The preparation method of the gangue-based high-porosity mine geothermal development filling material according to claim 1, characterized in that, In step S3, the water reducer is an aliphatic series water reducer.

6. The preparation method of the gangue-based high-porosity mine geothermal development filling material according to claim 1, characterized in that, In step S3, the layered ramming method is adopted. Every time the newly added stacking thickness of the mixture reaches 50 mm, it needs to be rammed 20 - 30 times.

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