Preparation method of coal mine goaf filling paste

Abstract

The invention provides a preparation method of coal mine goaf filling paste, and relates to the technical field of mining area paste filling, and the preparation method comprises three steps of material and equipment preparation, coal gangue slurry preparation and filling paste preparation. Coal slime water from the bottom of a concentration tank of a coal cleaning plant is introduced to serve as a part of a filling paste material, coal slime in the coal slime water belongs to superfine particles, coal ash belongs to a fine particle size, then the fine particle size particles are used for filling gaps among coarse particles, and the superfine particle size particles are large in specific surface area and have enough water saturation; the coarse particles are distributed among the coarse particles after being combined with the water molecules, so that the stability among the solid particles in the paste filling material is ensured, and the paste filling material has enough plasticity to maintain the three-dimensional structure of the paste filling material when the paste filling material is static, therefore, in the process of preparing the filling paste, under the condition that the strength of the filling paste can be ensured, the filling efficiency is improved. The dosage of the coal gangue and the fly ash is reduced, and the cost of preparing the filling paste is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of paste filling in mining areas, and in particular to a method for preparing a paste for filling a coal mine goaf area. Background Art

[0002] Coal mines occupy a dominant position in my country's energy structure, but the harm caused by coal mining to the ecological environment is also obvious to all, mainly including surface collapse caused by coal mining, coal gangue accumulation and damage to the ecological environment of the mining area. Among them, the impact of surface collapse on the environment is particularly serious. Coal mine goaf filling paste refers to a special filling material transported to the goaf during coal mining in order to control surface subsidence, protect the ecological environment of the mining area and improve resource utilization. This material is usually mixed with coal gangue, fly ash, cement and other additives in a certain proportion, and after stirring, it forms a paste with certain fluidity and pumpability.

[0003] Filling materials are the core content of filling mining technology. In the past, the materials used for paste filling are generally coal gangue, fly ash, slag and cement. With the country's redevelopment and utilization of these materials, the cost of these materials has increased, resulting in an increase in the overall preparation cost of the filling paste. If the preparation cost is to be reduced, the strength of the filling paste will be affected, and then it will be unable to meet the strength requirements of coal mine filling mining. Therefore, the present invention proposes a method for preparing a filling paste for coal mine goaf to solve the problems existing in the prior art. Summary of the invention

[0004] In view of the above problems, the purpose of the present invention is to propose a method for preparing a filling paste for coal mine goaf, which adopts a wet addition method and introduces coal slurry water to replace part of the fly ash, thereby effectively reducing the cost of preparing the filling paste and solving the problems existing in the prior art.

[0005] To achieve the purpose of the present invention, the present invention is implemented by the following technical scheme: a method for preparing a filling paste for a coal mine goaf, comprising the following steps:

[0006] Step 1: Preparation of materials and equipment

[0007] Prepare filling equipment for filling paste preparation, and prepare raw materials for filling paste preparation in advance according to the formula, wherein the formula includes the following raw materials in weight percentage: 35-45% of coal gangue, 14-24% of fly ash, 5-8% of coal slurry, 5-10% of cement, 4-9% of inferior soil blocks, 18-20% of water and 1-2% of admixture, and pre-treat the inferior soil blocks and coal gangue;

[0008] Step 2: Preparation of coal gangue slurry

[0009] Adding coal gangue, inferior soil blocks, fly ash, cement and water into a mixer according to the formula, stirring, and obtaining coal gangue slurry after stirring;

[0010] Step 3: Preparation of filling paste

[0011] The gangue slurry obtained in step 2 is added into the filling equipment, and then the coal slime water is input into the filling equipment and mixed with the gangue slurry. An admixture is added during the mixing process to obtain a filling paste after mixing, wherein the coal slime water comes directly from the bottom of the thickening tank of the coal washing plant.

[0012] A further improvement is that in step 1, the specific steps of pre-processing are:

[0013] S1: First, the inferior soil blocks are dried in a drying oven;

[0014] S2: After drying, it is put into a crusher together with coal gangue to obtain crushed material.

[0015] A further improvement is that in step one, the filling equipment includes a filling water tank and a coal slurry water buffer tank, and both the filling water tank and the coal slurry water buffer tank are provided with stirring equipment.

[0016] A further improvement is that in step 1, a mortar concentration detector is provided in both the filling water tank and the coal slurry water buffer tank.

[0017] A further improvement is that in step 1, the particle size of the coal slime in the coal slime water is less than 20 μm.

[0018] A further improvement is that in step 1, the fly ash particle size is less than 50 μm.

[0019] A further improvement is that in step 2, the specific steps of stirring are:

[0020] A1: First add coal gangue, fly ash and inferior soil into the mixer and mix them for 5 to 8 minutes;

[0021] A2: Then add cement and water into the mixer in sequence and mix for 10 to 15 minutes.

[0022] A further improvement is that in step three, the admixture includes a water reducer, a retarder and water glass, and the ratio of the water reducer, the retarder and the water glass is 2:1:2.

[0023] A further improvement is that in step three, the mixing time is 10 to 30 minutes.

[0024] The beneficial effects of the present invention are as follows: a method for preparing a filling paste for a coal mine goaf provided by the present invention adopts a wet preparation method to introduce coal sludge water from the bottom of a thickening tank in a coal washing plant as a part of the filling paste material. The coal sludge in the coal sludge water is an ultrafine particle, while the fly ash is a fine particle. Then, the fine particle size particles are used to fill the gaps between the coarse particles. The ultrafine particle size particles have a large specific surface area and sufficient water saturation. After combining with water molecules, they are distributed between the coarse particles, thereby ensuring the stability between the solid particles in the paste filling material, so that the paste filling material has sufficient plasticity to maintain its three-dimensional structure when stationary. Therefore, in the process of preparing the filling paste, the present invention can reduce the amount of coal gangue and fly ash used while ensuring the strength of the filling paste, thereby reducing the cost of preparing the filling paste. At the same time, the wet preparation method is relatively direct, has good controllability, and is not prone to environmental problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the steps of the present invention. DETAILED DESCRIPTION

[0026] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with examples. The examples are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0027] In the following embodiments, the materials are purchased from the market, the water reducer is a naphthalene-based high-efficiency water reducer, and the retarder is gypsum; in the present invention, the proportion of coal slime in the coal slime water is 70% of the coal slime water, for example, 50 kg of coal slime water contains 35 kg of coal slime; poor-quality soil blocks generally refer to soils that are not suitable for agricultural use, such as sand, clay, silt, etc. In the following embodiments, the poor-quality soil blocks are derived from the poor-quality soil blocks generated when excavating foundations or carrying out earthworks at construction sites.

[0028] Embodiment 1

[0029] according to Figure 1 As shown, this embodiment proposes a method for preparing a coal mine goaf filling paste, comprising the following steps:

[0030] Step 1: Preparation of materials and equipment

[0031] Prepare filling equipment for filling paste preparation, and prepare raw materials for filling paste preparation in advance according to the formula, wherein the formula includes the following raw materials in weight percentage: 45% coal gangue, 14% fly ash, 5% coal slime water, 10% cement, 4% inferior soil block, 20% water and 2% admixture, wherein the coal slime particle size in the coal slime water is less than 20 μm, and the fly ash particle size is less than 50 μm, and the inferior soil block and coal gangue are pretreated, and the specific steps of pretreatment are as follows:

[0032] S1: First, dry the inferior soil blocks in a drying oven until the moisture content does not exceed 5%;

[0033] S2: Put the dried inferior soil blocks and coal gangue into a crusher for crushing to obtain crushed materials;

[0034] The filling equipment includes a filling water tank and a coal slurry water buffer tank, both of which are equipped with stirring equipment, and both of which are equipped with mortar concentration detectors;

[0035] Step 2: Preparation of coal gangue slurry

[0036] Add coal gangue, inferior soil, fly ash, cement and water into a mixer according to the formula and stir to obtain coal gangue slurry. The specific steps of adding materials and stirring are as follows:

[0037] A1: First, add coal gangue, fly ash and inferior soil into the mixer and mix them for 8 minutes;

[0038] A2: Then add cement and water into the mixer in sequence and mix for 15 minutes;

[0039] Step 3: Preparation of filling paste

[0040] The gangue slurry obtained in step 2 is added into the filling water tank of the filling equipment, and then the coal slime water is input into the filling water tank, that is, the other raw materials are first prepared into gangue slurry, and then mixed with the coal slime water in the filling water tank, and the mixed material is used for subsequent filling operations. Furthermore, an admixture is added during the mixing process with the gangue slurry, and a filling paste is obtained after mixing, wherein the coal slime water comes directly from the bottom of the thickening tank of the coal washing plant, and the admixtures include water reducer, retarder and water glass (sodium silicate), and the ratio of water reducer, retarder and water glass is 2:1:2, and the mixing time is 30 minutes.

[0041] Embodiment 2

[0042] according to Figure 1 As shown, this embodiment proposes a method for preparing a coal mine goaf filling paste, comprising the following steps:

[0043] Step 1: Preparation of materials and equipment

[0044] Prepare filling equipment for filling paste preparation, and prepare raw materials for filling paste preparation in advance according to the formula, wherein the formula includes the following raw materials in weight percentage: 35% coal gangue, 24% fly ash, 8% coal slime water, 5% cement, 9% inferior soil block, 18% water and 1% admixture, wherein the coal slime particle size in the coal slime water is less than 20 μm, and the fly ash particle size is less than 50 μm. Pre-treat the inferior soil block and coal gangue, and the specific steps of pre-treating are as follows:

[0045] S1: First, the inferior soil blocks are dried in a drying oven;

[0046] S2: After drying, the mixture is put into a crusher together with coal gangue to obtain crushed material;

[0047] The filling equipment includes a filling water tank and a coal slurry water buffer tank. Both the filling water tank and the coal slurry water buffer tank are provided with stirring equipment. At the same time, both the filling water tank and the coal slurry water buffer tank are provided with a mortar concentration detector. The coal washing plant directly transports the coal slurry water at the bottom of the concentration tank to the filling water tank. The method can effectively reduce the operation amount of the filter press in the coal washing plant, thereby saving the filter pressing cost. Then, both the filling water tank and the coal slurry water buffer tank are provided with stirring equipment for mixing and preparation. At the same time, both the filling water tank and the coal slurry water buffer tank are provided with a mortar concentration detector. The corresponding concentrations in the filling water tank and the coal slurry water buffer tank are monitored by a concentration meter. Then, when the concentration decreases, corresponding adjustments can be made to stabilize it at a certain concentration, thereby reducing the influence of the coal slurry water concentration on the paste, increasing the controllability of the addition process, and making the addition amount more accurate. Specifically, the coal slurry water buffer tank plays a pre-storage effect. When not filled, the coal slurry water is transported to the coal slurry water buffer tank and waits for subsequent use.

[0048] Step 2: Preparation of coal gangue slurry

[0049] Add coal gangue, inferior soil, fly ash, cement and water into a mixer according to the formula and stir to obtain coal gangue slurry. The specific steps of adding materials and stirring are as follows:

[0050] A1: First, add coal gangue, fly ash and inferior soil into a mixer and stir for 5 minutes;

[0051] A2: Then add cement and water into the mixer in sequence and mix for 10 minutes;

[0052] Step 3: Preparation of filling paste

[0053] The gangue slurry obtained in step 2 is added into the filling equipment, and then the coal slime water is input into the filling equipment and mixed with the gangue slurry. During the mixing process, an admixture is added to obtain a filling paste after mixing, wherein the coal slime water comes directly from the bottom of the thickening tank of the coal washing plant, and the admixtures include water reducer, retarder and water glass (sodium silicate). The ratio of water reducer, retarder and water glass is 2:1:2, and the mixing time is 10 minutes.

[0054] Embodiment 3

[0055] according to Figure 1 As shown, this embodiment proposes a method for preparing a coal mine goaf filling paste, comprising the following steps:

[0056] Step 1: Preparation of materials and equipment

[0057] Prepare filling equipment for filling paste preparation, and prepare raw materials for filling paste preparation in advance according to the formula, wherein the formula includes the following raw materials in weight percentage: 40% coal gangue, 20% fly ash, 7% coal slime water, 8% cement, 5% inferior soil block, 19% water and 1% admixture, wherein the coal slime particle size in the coal slime water is less than 20 μm, and the fly ash particle size is less than 50 μm. Pre-treat the inferior soil block and coal gangue, and the specific steps of pre-treating are as follows:

[0058] S1: First, the inferior soil blocks are dried in a drying oven. The inferior soil blocks refer to the soil that is not suitable for agricultural use, and are used as aggregate to increase the volume and stability of the filling material solid granular material;

[0059] S2: After drying, the coal gangue is put into a crusher together with the coal gangue to obtain crushed materials. During the crushing process, a preliminary mixing effect can be achieved. Furthermore, after crushing, screening is performed to produce coarse aggregate and fine aggregate;

[0060] Furthermore, the filling equipment includes a filling water tank and a coal slurry water buffer tank. By laying pipelines, the coal washing plant directly transports the coal slurry water at the bottom of the concentration tank to the filling water tank. The method can effectively reduce the operation amount of the filter press in the coal washing plant, thereby saving the filter pressing cost. Then, the filling water tank and the coal slurry water buffer tank are both provided with stirring equipment for mixing and preparation. At the same time, the filling water tank and the coal slurry water buffer tank are both provided with a mortar concentration detector. The corresponding concentrations in the filling water tank and the coal slurry water buffer tank are monitored by the mortar concentration detector. Then, when the concentration decreases, corresponding adjustments can be made to stabilize it at a certain concentration, thereby reducing the influence of the coal slurry water concentration on the paste, increasing the controllability of the addition process, and making the addition amount more accurate. Specifically, the coal slurry water buffer tank plays a pre-storage effect. When not filled, the coal slurry water is transported to the coal slurry water buffer tank and waits for subsequent use.

[0061] Step 2: Preparation of coal gangue slurry

[0062] Add coal gangue, inferior soil, fly ash, cement and water into a mixer according to the formula and stir to obtain coal gangue slurry. The specific steps of adding materials and stirring are as follows:

[0063] A1: First, add coal gangue, fly ash and inferior soil blocks into the mixer, that is, mix the crushed materials and fly ash in step 1 for 7 minutes;

[0064] A2: Then add cement and water into the mixer in sequence and mix for 12 minutes;

[0065] Step 3: Preparation of filling paste

[0066] The gangue slurry obtained in step 2 is added into the filling equipment, and then the coal slime water is input into the filling equipment and mixed with the gangue slurry. An admixture is added during the mixing process to obtain a filling paste after mixing, wherein the coal slime water comes directly from the bottom of the thickening tank of the coal washing plant, and the admixtures include water reducer, retarder and water glass (sodium silicate). The ratio of water reducer, retarder and water glass is 2:1:2, and the mixing time is 10 to 30 minutes. The water glass is used to improve the early strength and durability of the filling paste, the retarder is used to adjust the setting time of the filling paste, and the water reducer is used to reduce the amount of water required in the filling paste while maintaining or improving its fluidity. Specifically, the coal slime water and the filling raw materials are first mixed together to make a gangue filling slurry for subsequent filling operations, wherein the water content in the coal slime water needs to be determined in advance and input into the control system, and the control system is used to adjust the amount of water in the filling material ratio at any time to ensure that a qualified slurry is made.

[0067] In combination with Example 1, Example 2 and Example 3, for the dry addition method, the dry addition is to dry the tail coal slime cake produced by the filter press to less than 15% moisture, and add it to the gangue to crush it together. The disadvantage is that the tail coal slime cake has a high water content, which is easy to clog the drum screen during the crushing process, reducing the crushing efficiency. After entering the gangue bin, it is easy to agglomerate and stick to the wall, causing poor material discharge, affecting the filling efficiency. Therefore, it needs to be dried on the spot before use, but the air-drying cycle of the tail coal slime cake is too long, about 20 days, and it occupies a large area, affecting the storage of gangue, and cannot be used in large quantities. Therefore, the present invention adopts a wet addition method. By laying pipelines, the coal washing plant directly transports the coal slime water at the bottom of the concentration tank to the filling pool, and then mixes it according to the formula to obtain a filling paste. This method can effectively reduce the operation amount of the filter press in the coal preparation plant, thereby saving the filter pressing cost. Since the concentration of coal sludge water at the bottom of the thickening tank is relatively stable and the delivery flow rate is adjustable, fluid delivery is more convenient, will not cause environmental problems, and is more controllable, thereby reducing the overall cost of the filling paste.

[0068] Secondly, in the present invention, the particle size of the coal slurry in the coal slurry water is less than 20μm, which belongs to ultrafine particles. The chemical substances of the coal slurry are mainly SiO2 and A12O3, which form colloidal particles on the surface of the coal slurry with negative charge, so that these particles remain dispersed in the water. Polar water molecules are attracted to the surrounding to form a layer of "hydration film", and the "hydration film" forms gaps between the colloid particles. Under the action of the above factors, the coal slurry water forms a stable colloidal dispersion state and has a certain suspension ability. Furthermore, the particle size of the fly ash in the present invention is less than 50μm, which belongs to fine-grained particles. Fine-grained particles are used to fill the gaps between coarse particles, while ultrafine particles have a large specific surface area and sufficient water saturation. After combining with water molecules, they are distributed between coarse particles, thereby ensuring the stability between solid particles in the paste filling material, so that the paste filling material has sufficient plasticity to maintain its three-dimensional structure when it is static.

[0069] Taking compressive strength as the benchmark target, the increase in the amount of coal slime added will lead to a small decrease in compressive strength. Therefore, the present invention controls the amount of coal slime added, and further uses no coal slime water and inferior soil blocks as a control group (the formula of the control group is: 46% coal gangue, 26% fly ash, 8% cement, 19% water and 1% admixture), and compares the filling paste prepared in Examples 1 to 3 of this invention with the paste sampling. The performance is shown in the following table:

[0070]

[0071] As shown in the above table, although the addition of coal slurry water will reduce the compressive strength, it can still meet the needs of filling mining. On this basis, the addition of coal slurry water can reduce the amount of coal gangue and fly ash. For one square meter of filling paste (about 1945gk), an average of 22.6kg of coal slurry is used in each cubic meter of paste. After adding coal slurry, the amount of gangue in each cubic meter of paste is reduced by an average of 30kg, and the amount of fly ash is reduced by 20kg, thereby reducing the overall preparation cost and bringing economic benefits to the company.

[0072] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the framework and scope of application of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a filling paste for coal mine goaf, characterized in that: The following steps are involved: Step 1: Preparation of materials and equipment Prepare filling equipment for filling paste preparation, and prepare raw materials for filling paste preparation in advance according to the formula, wherein the formula includes the following raw materials in weight percentage: 35-45% of coal gangue, 14-24% of fly ash, 5-8% of coal slurry, 5-10% of cement, 4-9% of inferior soil blocks, 18-20% of water and 1-2% of admixture, and pre-treat the inferior soil blocks and coal gangue; Step 2: Preparation of coal gangue slurry Adding coal gangue, inferior soil blocks, fly ash, cement and water into a mixer according to the formula, stirring, and obtaining coal gangue slurry after stirring; Step 3: Preparation of filling paste The gangue slurry obtained in step 2 is added into the filling equipment, and then the coal slime water is input into the filling equipment and mixed with the gangue slurry. An admixture is added during the mixing process to obtain a filling paste after mixing, wherein the coal slime water comes directly from the bottom of the thickening tank of the coal washing plant.

2. The method for preparing a coal mine goaf filling paste according to claim 1, characterized in that: In the step 1, the specific steps of pretreatment are: S1: First, the inferior soil blocks are dried in a drying oven; S2: After drying, it is put into a crusher together with coal gangue to obtain crushed material.

3. The method for preparing a coal mine goaf filling paste according to claim 1, characterized in that: In the step 1, the filling equipment includes a filling water tank and a coal slurry water buffer tank, and the filling water tank and the coal slurry water buffer tank are both provided with stirring equipment.

4. The method for preparing a coal mine goaf filling paste according to claim 1, characterized in that: In the step 1, a mortar concentration detector is provided in both the filling water tank and the coal slurry water buffer tank.

5. The method for preparing a coal mine goaf filling paste according to claim 1, characterized in that: In the step 1, the particle size of the coal slime in the coal slime water is less than 20 μm.

6. The method for preparing a coal mine goaf filling paste according to claim 1, characterized in that: In the step 1, the particle size of fly ash is less than 50 μm.

7. The method for preparing a coal mine goaf filling paste according to claim 1, characterized in that: In the step 2, the specific steps of stirring are: A1: First add coal gangue, fly ash and inferior soil into the mixer and mix them for 5 to 8 minutes; A2: Then add cement and water into the mixer in sequence and mix for 10 to 15 minutes.

8. The method for preparing a coal mine goaf filling paste according to claim 1, characterized in that: In the step three, the admixtures include a water reducer, a retarder and water glass (sodium silicate), and the ratio of the water reducer, the retarder and the water glass is 2:1:

2.

9. The method for preparing a coal mine goaf filling paste according to claim 1, characterized in that: In the step 3, the mixing time is 10 to 30 minutes.

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