Preparation method of coal gangue composite grouting material

Abstract

The invention discloses a preparation method of a coal gangue composite grouting material, which comprises the following steps: step 1, preparing coal gangue aggregate: drying crushed coal gangue, and screening to obtain the coal gangue aggregate consisting of fine aggregate and coarse aggregate; step 2, preparing a coal gangue gel material: uniformly mixing the crushed coal gangue with graphite, performing microwave activation, adding a chemical activator, mixing, and grinding to obtain the coal gangue gel material; and mixing the coal gangue gel material and the coal gangue aggregate, adding water, and uniformly stirring. According to the method, the technological process is simple and easy to implement, efficient utilization of mine solid waste is achieved, the mining cost is greatly reduced, the grouting filling material with the excellent mechanical property is successfully obtained, and progress and development of the coal gangue based grouting technology are powerfully promoted.

Description

Technical Field

[0001] The invention relates to the technical field of mine solid waste utilization, and in particular to a method for preparing a coal gangue composite grouting material. Background Art

[0002] Gangue is a solid gangue waste discharged during the washing and processing of coal. Its total emission accounts for about 15%-20% of the total coal production. At present, most coal mining enterprises in my country still use underground transportation to the ground and then discharge it to designated areas. In the past 10 years, the average annual growth rate of gangue in my country has been about 3.92%, and the average annual growth of gangue in the past five years has been about 30 million tons. As of 2021, the total amount of accumulated gangue waste in my country has reached 7 billion tons. According to relevant data from the National Bureau of Statistics, the national coal production in 2021 was 4.13 billion tons, a year-on-year increase of 5.7%, a record high; in 2021, Shaanxi Province's coal production was 699.9375 million tons, a year-on-year increase of 2.66%, accounting for 17.2% of the national coal production, ranking third in the country. At the same time, my country's gangue production is about 743 million tons, with a year-on-year increase of 5.84%. A large amount of open-air dumping of coal gangue, after rainfall leaching, some soluble substances migrate with rainwater and infiltrate into the soil and groundwater, causing an imbalance in the surrounding ecological environment and damaging the soil properties. Therefore, actively carrying out coal gangue treatment and realizing green and efficient coal mining is in line with the country's overall requirements for green mine construction and has important promoting significance for the efficient and sustainable development of coal energy.

[0003] Most common theories of gangue activation are based on high-temperature calcination, which has the obvious disadvantages of high energy consumption, high pollution and long time consumption. This is why gangue has not been widely used in industry so far. Microwave activation is a new type of activation method with low energy consumption and low pollution, and the process takes a short time. By using microwave irradiation to activate gangue, it can achieve the same or even better activity as conventional calcination, so as to achieve the country's overall requirements for green mine construction.

[0004] The composite activation of coal gangue is the result of a cross-combination of multiple activation methods. Studies have shown that the result of a single activation is usually weaker than the combination of two or three activation methods. The aggregate screened out and the cementitious material made after composite activation constitute the composite activated coal gangue grouting material.

[0005] A Chinese patent application with publication number CN114560651A discloses a coal gangue-based mine cementitious filling material and a preparation method thereof, wherein a filling body mixed with coal gangue and slag is disclosed, and the coal gangue is ground and mixed with slag, and then the cementitious materials of coarse and fine particle size coal gangue are mixed and stirred, and finally the chemical activators calcium hydroxide and sodium hydroxide are mixed and stirred evenly to prepare the mine cementitious filling material. Summary of the invention

[0006] In view of the above technical problems, the present invention provides a method for preparing a coal gangue composite grouting material, which can produce the coal gangue grouting material without using cement materials.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A method for preparing a coal gangue composite grouting material comprises the following steps:

[0009] Step 1: Preparation of coal gangue aggregate:

[0010] The crushed coal gangue is dried and then sieved to obtain coal gangue aggregate consisting of fine aggregate and coarse aggregate;

[0011] Step 2: Preparation of coal gangue gel material:

[0012] The crushed gangue is mixed with graphite, and then activated by microwaves, and then a chemical activator is added and mixed, and then ground to obtain a gangue gel material;

[0013] The gangue gel material is mixed with the gangue aggregate and then water is added and mixed evenly.

[0014] Optionally, in the step 2, the amount of graphite added is 5% to 7% of the amount of coal gangue added by mass.

[0015] Optionally, in step 2, the chemical stimulant is a mixture of calcium hydroxide and sodium hydroxide, and the added amounts of calcium hydroxide and sodium hydroxide are both 2% to 4% of the mass of the coal gangue.

[0016] Optionally, the mass ratio of the coal gangue gel material to the coal gangue aggregate is 1.2:1.

[0017] Optionally, in step 1, the particle size of the fine aggregate is 0.20-4.55 mm, the particle size of the coarse aggregate is greater than 4.55 mm, and the water content is <0.3%.

[0018] Optionally, in the step 2, the temperature of microwave activation is controlled to be 650-750° C., and the microwave activation time is 7-15 min.

[0019] Optionally, in the step 2, the mixture after microwave activation is further cooled to a temperature below 40°C.

[0020] Optionally, the cooling adopts a multi-stage vertical cooling method, and the air supply system of the first-stage cooling unit selects a dry cooling blower with an air volume of 2900m 3 / t; The secondary cooling unit system uses a normal temperature blower with an air volume of 1600m3 / t.

[0021] Optionally, the gangue gel material is mixed with the gangue aggregate and then stirred with water to have a water-cement ratio of 0.35 to 0.55.

[0022] Optionally, the coal gangue in step 1 and step 2 are taken from the same portion;

[0023] The coal gangue with a particle size greater than or equal to 0.20 mm is the raw material for preparing coal gangue aggregate, and the remaining coal gangue with a particle size less than 0.20 mm is the raw material for preparing coal gangue gel material.

[0024] The advantages of the present invention are:

[0025] 1. The process flow is simple and efficient: The process flow of the present invention is simple and easy to implement. It not only realizes the efficient utilization of mine solid waste and greatly reduces the mining cost, but also successfully obtains grouting filling materials with excellent mechanical properties, which effectively promotes the progress and development of coal gangue-based grouting technology.

[0026] 2. Significant ecological and environmental benefits: Using coal gangue as filling raw materials helps to reconstruct the geological conditions and ecological system of the coal field and achieve the goal of "zero" emissions from mines. This can not only effectively prevent ground subsidence, but also completely solve the environmental pollution problem caused by open-air storage of coal gangue.

[0027] 3. Strong material adaptability and high cost-effectiveness: The present invention can flexibly adjust the ratio of the composite activated gangue gel and coarse and fine aggregates, thereby obtaining grouting materials suitable for a variety of complex environments. While avoiding the introduction of high-cost cement materials, it significantly improves the utilization efficiency of mine solid waste, providing solid technical support for the realization of green and efficient mining.

[0028] 4. Innovative activation method that saves energy and time: It successfully solved the problem of high energy consumption and long time consumption in the conventional coal gangue thermal activation process, and greatly improved production efficiency.

[0029] 5. Economical and practical selection of absorbing materials: The present invention cleverly selects graphite and water as absorbing materials. Graphite heats up quickly in a microwave environment and has a relatively moderate price, while water is a material that easily absorbs microwaves. The synergistic effect of the two not only reduces the amount of graphite added, effectively reduces costs, but also significantly shortens the time required for a microwave activation.

[0030] 6. Breakthrough of technical bottlenecks: The technical difficulties of low utilization rate and difficult treatment of coal gangue in existing technologies have been overcome. Finally, coal gangue grouting materials that meet the quality standards have been successfully prepared, achieving efficient conversion and utilization of mine solid waste, truly turning waste into treasure, and successfully solving the key and difficult problems in the process of coal gangue treatment.

[0031] 7. Obvious cost advantage: The present invention successfully prepares coal gangue grouting materials without relying on cement. The production process and materials used are simpler, which greatly reduces the production and processing costs and has significant economic advantages. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention are described in full below. Only some embodiments of the present invention are described, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] First of all, compared with the prior art, the present application presents distinct and key distinguishing technical features in terms of process methods. Specifically, it is characterized by the pioneering introduction of a microwave activation process and a multi-stage vertical cooling process, and is unique in the selection of activators. In the prior art, although methods for preparing mine cementing filling materials using coal gangue have been disclosed, the coal gangue involved therein that has not been treated with high-temperature activation or microwave activation cannot achieve deep excitation and comprehensive release of the activity of coal gangue due to the limitations and insufficiency of the activation mechanism. The microwave activation method adopted in the present application, with its unique energy transfer mode and microscopic action mechanism, can accurately reach the active sites inside the coal gangue in a more targeted and efficient manner, achieve deep excitation of active ingredients, and greatly improve the active utilization efficiency of coal gangue. The content of calcium in coal gangue is relatively low, and calcium ions can react faster than sodium ions. By introducing calcium hydroxide and sodium hydroxide, CSH and CASH gels are generated to improve the strength of the material. The carefully designed multi-stage vertical cooling process effectively optimizes the microstructure and performance distribution of the material by precisely controlling the cooling rate and temperature gradient, promotes the preferential growth of crystals and the rational control of defects, thereby significantly enhancing the comprehensive performance of mine cementing filling materials, including but not limited to key indicators such as strength, stability and fluidity.

[0034] Specifically, the preparation method of the coal gangue composite grouting material of the present invention comprises the following steps:

[0035] ①Raw material selection: Aggregate and cementitious material are taken from the same coal gangue;

[0036] ② Crushing: crushing the gangue in step ① to obtain crushed material;

[0037] ③ Screening: Screen the gangue crushed materials in step ②, dry part of the gangue to obtain gangue filling aggregate, and put the remaining crushed materials and graphite into a stirring device to stir them evenly;

[0038] ④ Drying: The crushed material in step ③ is dried to obtain coal gangue aggregate;

[0039] 5. Screening aggregate: Screening the gangue aggregate obtained in step 4 to obtain fine aggregate and coarse aggregate;

[0040] ⑥ Controlling the discharge amount: Controlling the aggregate discharge amount in step ⑤, and synthesizing the coal gangue material to meet different grouting requirements by changing the ratio of coarse and fine aggregates;

[0041] ⑦ Microwave activation: Mix the gangue and graphite in step ③ and use Microwave equipment Perform microwave activation;

[0042] ⑧ Cooling: Cooling the mixture after microwave activation in step ⑦, and finally the temperature of the cooled material is lower than 40° C.;

[0043] ⑨ Grinding: mixing the cooled material in step ⑧ with a chemical activator and grinding to obtain microwave-mechanical-chemical composite activated coal gangue;

[0044] ⑩Stirring: Mixing and stirring the coarse and fine aggregates obtained in step ⑥ and the activated coal gangue material obtained in step ⑨;

[0045] Add mixing water to the obtained product for mixing and stirring. Chemical activation will occur at this stage, further stimulating the activity of the coal gangue powder to generate a composite activated coal gangue grouting material.

[0046] In step ③, the coal gangue with a particle size greater than or equal to 0.20 mm is taken as aggregate and dried, and the remaining particle size less than 0.20 mm is put into a mixing device.

[0047] In step ④, the moisture content of the obtained dry gangue aggregate is <0.3%.

[0048] In step ⑤, aggregate with a particle size of 0.20 to 4.55 mm is used as fine aggregate, and aggregate with a particle size greater than 4.55 mm is used as coarse aggregate.

[0049] In step ⑦, the temperature of microwave activation is controlled at 650-750° C., the time is set at 7-15 min, and the amount of graphite added is selected to be 5%-7% of the total amount of coal gangue.

[0050] In step ⑧, a multi-stage vertical cooling method is adopted, and the air supply system of the first-stage cooling unit selects a dry cooling blower with an air volume of 2900m 3 / t; The secondary cooling unit system uses a normal temperature blower with an air volume of 1600m 3 / t.

[0051] In step ⑨, the chemical stimulants are calcium hydroxide and sodium hydroxide, and the addition amount of solid sodium hydroxide and calcium hydroxide powder is 2% to 4% of the total amount of coal gangue powder, preferably 3%, and the final requirement is that the residue of the mixture after passing through a 300-mesh sieve is less than 7%.

[0052] In step ⑨, the grinding time of the obtained material particles is 10 to 25 minutes.

[0053] In step ⑩, the coarse and fine aggregates obtained in step ⑥ and the coal gangue cementitious material obtained in step ⑨ are mixed and stirred for 10 to 25 minutes, and the mass ratio of the two is 1:1.2.

[0054] In step ⑩, the water-cement ratio of the stirred cementitious material is 0.35-0.55.

[0055] Embodiment 1:

[0056] ① Raw material selection: Select coal gangue samples with an aluminum oxide content of 50% and a silicon oxide content of 19.6%;

[0057] ② Crushing: crushing the gangue selected in step ① to obtain gangue crushed materials;

[0058] ③ Screening: Screen the gangue crushed materials in step ②, dry part of the gangue to obtain gangue filling aggregate, and put the remaining crushed materials and graphite into a stirring device to stir them evenly, and the amount of graphite added is 7% of the total amount of gangue;

[0059] ④ Drying: The crushed material in step ③ is dried to a moisture content of less than 0.3%, thereby obtaining coal gangue aggregate;

[0060] ⑤ Screening: The aggregate with a particle size of 0.20 to 4.55 mm in step ④ is used as fine aggregate, and the aggregate with a particle size greater than 4.55 mm is used as coarse aggregate;

[0061] ⑥ Controlling the aggregate discharge amount: Controlling the coarse and fine aggregate discharge amount obtained in step ⑤, and preparing the coal gangue grouting material meeting different environmental requirements by controlling the coarse and fine aggregate ratio. In this embodiment, the mass ratio of the coarse and fine aggregates is 1:1.15;

[0062] ⑦ Microwave activation: put the mixture of gangue and graphite in step ③ into industrial microwave equipment, the addition amount is 5% of the total amount of gangue, the temperature of the industrial microwave equipment is adjusted to 700°C, and the time is set to 15min;

[0063] ⑧ Cooling: The product obtained in step ⑦ is cooled by multi-stage vertical cooling. The air supply system of the first-stage cooling unit is a dry cooling blower with an air volume of 2900m 3 / t,; the secondary cooling unit system uses a normal temperature blower with an air volume of 1600m 3 / t, the product temperature after cooling is less than 40℃;

[0064] ⑨ Grinding: adding the cooled material in step ⑧ and calcium hydroxide and sodium hydroxide powders into a grinding mill for grinding, wherein the addition amount of calcium hydroxide and sodium hydroxide is 3% of the mass of the coal gangue, and the residue of the mixture after passing through a 300-mesh sieve is less than 7%, thereby obtaining microwave-mechanical-chemical composite activated coal gangue powder;

[0065] ⑩ Mixing and stirring: Mix the coarse and fine aggregate coal gangue cementitious material obtained in step ⑥ and the activated coal gangue material obtained in step ⑨ for 15 minutes, and the mass ratio of the two is 1:1.2;

[0066] Add mixing water and mix: Add mixing water to the product of step ⑩ and stir. Chemical activation will occur at this stage, further stimulating the activity of the gangue powder to generate a composite activated gangue grouting material. The water-cement ratio of the grouting material is 0.35, and the fluidity of the prepared gangue composite grouting material is 262mm, and the 3d and 28d compressive strengths are 4.23MPa and 6.54Mpa, respectively, meeting the corresponding requirements of C7.5S3 cement-based backfill materials (JC / T 2468-2018) and meeting the grouting filling requirements.

[0067] Embodiment 2:

[0068] ① Raw material selection: select coal gangue sample with aluminum oxide content of 45.2% and silicon oxide content of 23.2%;

[0069] ② Crushing: crushing the gangue selected in step ① to obtain gangue crushed materials;

[0070] ③ Screening: Screen the gangue crushed materials in step ②, dry part of the gangue to obtain gangue filling aggregate, and put the remaining crushed materials and graphite into a stirring device to stir them evenly;

[0071] ④ Drying: The crushed material in step ③ is dried to a moisture content of less than 0.3%, thereby obtaining coal gangue aggregate;

[0072] ⑤ Screening: The aggregate with a particle size of 0.20 to 4.55 mm in step ④ is used as fine aggregate, and the aggregate with a particle size greater than 4.55 mm is used as coarse aggregate;

[0073] ⑥ Controlling the aggregate discharge amount: Controlling the coarse and fine aggregate discharge amount obtained in step ⑤, and preparing the coal gangue grouting material meeting different environmental requirements by controlling the coarse and fine aggregate ratio. In this embodiment, the mass ratio of the coarse and fine aggregates is controlled to be 1:1.2;

[0074] ⑦ Microwave activation: put the mixture of gangue and graphite in step ③ into industrial microwave equipment, the addition amount is 7% of the total amount of gangue, the temperature of the industrial microwave equipment is adjusted to 680°C, and the time is set to 8min;

[0075] ⑧ Cooling: The product obtained in step ⑦ is cooled by multi-stage vertical cooling. The air supply system of the first-stage cooling unit is a dry cooling blower with an air volume of 2900m 3 / t; The secondary cooling unit system uses a normal temperature blower with an air volume of 1600m 3 / t, the product temperature after cooling is less than 40℃;

[0076] ⑨ Grinding: adding the cooled material in step ⑧ and calcium hydroxide and sodium hydroxide powders into a grinding mill for grinding, wherein the addition amount of calcium hydroxide and sodium hydroxide is 3% of the mass of the coal gangue, and the residue of the mixture after passing through a 300-mesh sieve is less than 7%, thereby obtaining microwave-mechanical-chemical composite activated coal gangue powder;

[0077] ⑩ Mixing and stirring: Mix the coarse and fine aggregate coal gangue cementitious material obtained in step ⑥ and the activated coal gangue material obtained in step ⑨ for 15 minutes, and the mass ratio of the two is 1:1.2;

[0078] Add mixing water and mix: Add mixing water to the product of step ⑩ and stir. Chemical activation will occur at this stage, further stimulating the activity of the gangue powder to generate a composite activated gangue grouting material. The water-cement ratio of the grouting material is 0.45, and the fluidity of the prepared gangue composite grouting material is 248mm, and the 3d and 28d compressive strengths are 3.83MPa and 5.74Mpa, respectively, meeting the corresponding requirements of C7.5S3 cement-based backfill materials (JC / T 2468-2018) and meeting the grouting requirements.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a coal gangue composite grouting material, characterized in that: The following steps are involved: Step 1: Preparation of coal gangue aggregate: The crushed coal gangue is dried and then sieved to obtain coal gangue aggregate consisting of fine aggregate and coarse aggregate; Step 2: Preparation of coal gangue gel material: The crushed gangue is mixed with graphite, and then activated by microwaves, and then a chemical activator is added and mixed, and then ground to obtain a gangue gel material; The gangue gel material is mixed with the gangue aggregate and then water is added and mixed evenly.

2. The method for preparing the coal gangue composite grouting material according to claim 1, characterized in that: In the step 2, the amount of graphite added is 5% to 7% of the amount of coal gangue added by mass.

3. The method for preparing the coal gangue composite grouting material according to claim 1 or 2, characterized in that: In the step 2, the chemical stimulant is a mixture of calcium hydroxide and sodium hydroxide. The added amounts of calcium hydroxide and sodium hydroxide are both 2% to 4% of the mass of the coal gangue.

4. The method for preparing the coal gangue composite grouting material according to claim 1 or 2, characterized in that: The mass ratio of the coal gangue gel material to the coal gangue aggregate is 1.2:

1.

5. The method for preparing the coal gangue composite grouting material according to claim 1 or 2, characterized in that: In the step 1, the particle size of the fine aggregate is 0.20-4.55 mm, the particle size of the coarse aggregate is greater than 4.55 mm, and the water content is less than 0.3%.

6. The method for preparing the coal gangue composite grouting material according to claim 1 or 2, characterized in that: In the step 2, the temperature of microwave activation is controlled to be 650-750° C., and the microwave activation time is 7-15 minutes.

7. The method for preparing the coal gangue composite grouting material according to claim 1 or 2, characterized in that: In the step 2, the mixture after microwave activation is further cooled to a temperature below 40°C.

8. The method for preparing the coal gangue composite grouting material according to claim 7, characterized in that: The cooling adopts a multi-stage vertical cooling method. The air supply system of the first-stage cooling unit selects a dry cooling blower with an air volume of 2900m 3 / t; The secondary cooling unit system uses a normal temperature blower with an air volume of 1600m 3 / t.

9. The method for preparing the coal gangue composite grouting material according to claim 1 or 2, characterized in that: The coal gangue gel material is mixed with coal gangue aggregate and then stirred with water to have a water-cement ratio of 0.35 to 0.

55.

10. The method for preparing the coal gangue composite grouting material according to claim 1 or 2, characterized in that: The coal gangue in step 1 and step 2 are taken from the same portion; The coal gangue with a particle size greater than or equal to 0.20 mm is the raw material for preparing coal gangue aggregate, and the remaining coal gangue with a particle size less than 0.20 mm is the raw material for preparing coal gangue gel material.