A method for improving the flow properties of coal gasification slag filling slurry using calcium chloride

Abstract

The purpose of this invention is to provide a method for improving the flowability of coal gasification slag backfill slurry using calcium chloride, belonging to the field of mining engineering technology. This invention effectively improves the flowability of the coal gasification slag backfill slurry by adding a quantitative amount of calcium chloride powder to it, resulting in slurry that can smoothly pass through conveying pipelines without clogging, segregation, or exhibiting good viscosity and plasticity. This invention relates to a coal gasification slag backfill slurry base material, specifically comprising cement, coal gangue, coal gasification slag, and water. Coal gasification slag and coal gangue are the main components, both being industrial solid wastes. To address the problem of easy pipe blockage and production disruption during long-distance pumping of coal gasification slag backfill slurry, this invention introduces calcium chloride powder. By adding calcium chloride powder, the above problems can be effectively solved, and the utilization of solid waste materials such as coal gasification slag can be further realized. This not only promotes the sustainable development of the coal gasification industry but also achieves the goals of cost reduction and environmental protection.

Description

Technical Field

[0001] This invention belongs to the field of mining engineering technology, specifically relating to a method for improving the flow properties of coal gasification slag backfill slurry using calcium chloride. Background Technology

[0002] Compared to traditional thermal power generation, coal gasification cycle technology offers higher production efficiency and lower carbon dioxide emissions. However, during coal gasification, incomplete combustion occurs between coal and oxygen or oxygen-enriched air. Inorganic minerals in the coal undergo various physicochemical transformations, converting organic matter into chemicals. Residual carbon particles are discharged as gasification ash, forming coal gasification slag. As a solid waste product of coal gasification technology, coal gasification slag is the third largest coal-based solid waste after coal gangue and fly ash. Currently, the main method of treating coal gasification slag is landfill, causing serious environmental pollution. With increasing societal awareness of environmental protection, the harmless treatment and further reuse of industrial solid wastes such as coal gasification slag are urgently needed. Therefore, the application of coal gasification slag backfill slurry is a crucial step. Coal gasification slag backfill slurry, obtained through simplified processing, can be used for mine backfilling. Compared to traditional thermal power generation, coal gasification cycle technology offers higher production efficiency and lower carbon dioxide emissions. However, during coal gasification, incomplete combustion occurs between coal and oxygen or oxygen-enriched air. Inorganic minerals in the coal undergo physicochemical transformations, converting organic matter into chemicals. Residual carbon particles are discharged as gasification ash, forming coal gasification slag. As a solid waste from coal gasification technology, coal gasification slag is the third largest coal-based solid waste after coal gangue and fly ash. Currently, coal gasification slag is mainly treated through stockpiling and landfilling, causing serious environmental pollution. With increasing public awareness of environmental protection, the harmless treatment and reuse of industrial solid wastes such as coal gasification slag have become urgent. Therefore, preparing coal gasification slag into filling slurry for mine backfilling is a crucial step. Through simplified processing, coal gasification slag filling slurry can be obtained, allowing for further utilization of the coal gasification slag.

[0003] In the production process of coal gasification slag backfill slurry, the workability of the slurry is difficult to control effectively. If the coal gasification slag slurry has poor fluidity, it may cause blockage in the conveying pipeline, leading to increased backfilling and mining costs. If the slurry is too thin, the fluidity will be improved, but segregation may easily occur, which may not be able to provide effective support to the overlying strata in the early stage of the backfill body. Summary of the Invention

[0004] To address the aforementioned problems, this application provides a method for improving the flowability of coal gasification slag filling slurry using calcium chloride. On the one hand, this solves the problem of production quality issues caused by the difficulty in effectively controlling the flowability of coal gasification slag slurry in the prior art; on the other hand, it enables the full utilization of industrial solid wastes such as coal gasification slag and coal gangue, promoting the sustainable development of the coal gasification industry.

[0005] The present invention adopts the following technical solution: A method for improving the flow properties of coal gasification slag filling slurry using calcium chloride includes the following steps: 1. Adjust the flowability of the coal gasification slag slurry according to its properties. The specific steps for adjusting the flowability of the coal gasification slag slurry are as follows: (1) Control the phase composition and specific surface area of ​​calcium chloride; (2) When the water-cement ratio of the coal gasification slag slurry remains unchanged, the designed amount of anhydrous calcium chloride powder is added to the coal gasification slag filling slurry and stirred evenly, the slurry fluidity becomes better.

[0006] As a preferred embodiment of the present invention, the specific steps for testing the fluidity of coal gasification slag slurry are as follows: (1) Wet the inner wall of the flowability measuring cylinder and other tools, place the flowability measuring cylinder on a rigid horizontal base plate that does not absorb water, and evenly fill the cylinder with the coal gasification slag filling slurry sample mixed with calcium chloride. Use a tamping rod to tamp the slurry evenly from the outside to the center in a spiral direction 25 times. (2) When pouring the top layer, the slurry should be poured to the height of the cylinder opening. After the top layer is tamped, scrape off the excess slurry and smooth it with a trowel. (3) After removing the slurry from the bottom plate of the cylinder, lift the measuring cylinder vertically and steadily. The slurry forms a cake on the horizontal bottom plate. Measure the spreading diameter of the cake on the experimental table, measure a maximum value and a minimum value, and take the average value as the spreading diameter of the cake. (4) The flowability of the coal gasification slag filling slurry is judged by measuring the spread diameter of the filling slurry cake.

[0007] As a preferred embodiment of the present invention, the consistency container is a funnel-shaped conical container with an upper diameter of 40 mm, a lower diameter of 60 mm, and a height of 60 mm.

[0008] As a preferred embodiment of the present invention, the process for determining the consistency of coal gasification slag slurry is as follows: The standard range for the diameter of the spread cake is 90-140mm, and the optimal range is 100-135mm. If the diameter of the cake spread out is lower than the standard range, the coal gasification slag slurry is considered to be too thick. If the diameter of the cake spread out exceeds the optimal range, the coal gasification slag slurry is considered to be too thin. If the diameter of the cake spread out exceeds the optimal range but is within the standard range, the consistency of the coal gasification slag slurry is considered to be moderate. If the diameter of the cake spread out is within the optimal range, then the consistency of the coal gasification slag slurry is determined to be optimal.

[0009] The coal gasification slag, coal gangue, cement, and calcium chloride mentioned in this invention are all conventional raw materials in the field and can all be obtained commercially.

[0010] The specific operation includes the following steps: The first step is the pretreatment of coal gasification slag: collect the solid residue after coal gasification, perform carbon capture and removal, and remove impurities such as gravel and leaves mixed in during the coal gasification process by passing it through a 3mm square hole sieve. The second step is calcium chloride pretreatment: the refined neutral calcium chloride solution is sprayed into a mist from the top of the spray drying tower through a nozzle, and dried and dehydrated by countercurrent contact with a 300°C hot air stream to obtain powdered anhydrous calcium chloride. The third step is the preparation of the coal gasification slag filling slurry: According to the designed raw material mass fractions, weigh each raw material, and put water, cement, coal gangue and coal gasification slag into the mixer in sequence. At room temperature, stir at a speed of 57-67 r / min for 60s, stir at 115-135 r / min for 30s, stop stirring for 90s, and use a scraper to scrape the slurry on the blades, pot wall and pot bottom into the pot. Then stir at 115-135 r / min for 60s to obtain the coal gasification slag filling slurry. The fourth step is to add the designed mass fraction of calcium chloride to the coal gasification slag filling slurry prepared above and stir it evenly.

[0011] Furthermore, the coal gasification slag filling slurry comprises the following components in parts by weight: 7-9 parts coal gasification slag, 2-4 parts coal gangue, 1-2 parts cement, 2.5-3 parts water, and 0.07-0.09 parts calcium chloride.

[0012] Furthermore, the coal gasification slag filling slurry comprises the following components in parts by weight: 7 parts coal gasification slag, 2 parts coal gangue, 1 part cement, 2.5 parts water, and 0.07 parts calcium chloride.

[0013] Furthermore, the coal gasification slag is dried in an 80°C forced-air drying oven until its weight remains constant. The dried coal gasification slag is then added to a planetary ball mill and ball-milled for 100 minutes. After passing through a 200-mesh square-hole sieve, the residue on the sieve is <5%.

[0014] Furthermore, the planetary ball mill rotates at 500 r / min, and the ball milling method is to grind for 20 minutes, pause for 5 minutes to allow the ball mill to dissipate heat fully, and then continue to grind in the above manner until 120 minutes are completed.

[0015] Furthermore, the coal gangue is crushed using a jaw crusher, and then screened using vibrating screens of 5mm, 10mm and 15mm respectively to obtain fine aggregate of 0-5mm, medium aggregate of 5-10mm and coarse aggregate of 10-15mm; the mass ratio of coal gangue to coarse aggregate: medium aggregate: fine aggregate = 1:1:3.

[0016] Furthermore, the cement is P.O42.5 silicate cement.

[0017] Furthermore, the density of the gasification slag is 2.13 g / cm³. 3 The particle size range is 0.5–2.0 mm; the specific surface area of ​​the cement is 349 m². 2 / kg, density is 3.1g / cm³ 3 .

[0018] The beneficial effects of this invention are as follows: This invention uses industrial waste as the main raw material for coal gasification slag filling slurry. By adding an appropriate amount of calcium chloride powder, the flow properties of the slurry are improved. Firstly, when calcium chloride dissolves in water, the calcium ions produced by hydrolysis combine with hydroxide ions from water dissociation to form slightly soluble calcium hydroxide. Hydrolysis equation: Ca... 2+ +2H₂O→Ca(OH)₂+2H + Therefore, calcium chloride can promote the hydration reaction in coal gasification slag backing slurry, forming a gel, thereby increasing the slurry's adhesion and viscosity, and improving its fluidity. Secondly, in coal gasification slag backing slurry, the presence of fine solid particles with a large specific surface area leads to electrostatic forces, causing attraction or repulsion between particles, resulting in particle aggregation and accumulation. This increases the internal friction of the slurry and reduces its fluidity. As an electrolyte, calcium chloride decomposes into calcium ions (CaO) when dissolved in water. 2+ ) and chloride ions (Cl - These ions interact with the electrostatic charge on the particle surface, neutralizing it and reducing the electrostatic forces between fine particles in the gasification slag. This makes the particles easier to disperse and maintain a flowable state, thereby improving the flow properties of the slurry. Furthermore, the gasification slag filling slurry may contain sulfides from the gasification process, thus containing sulfate ions (SO42-). 2- When calcium chloride dissolves in water, it decomposes to produce calcium ions (Ca). 2+ ) and sulfate ions (SO4) 2- They combine to form calcium sulfate (CaSO4). The reaction equation is: Ca 2+ +SO4 2-→CaSO4, a soluble double salt, can increase the number of particles in the slurry and provide a better lubrication environment, which helps to improve the flow properties of the slurry.

[0019] In summary, adding an appropriate amount of calcium chloride can effectively improve the flow properties of coal gasification slag filling slurry, and help solve problems such as easy pipe blockage and production impact during pumping, thereby achieving better utilization of solid waste materials such as coal gasification slag.

[0020] This invention is rationally designed, using industrial solid wastes such as coal gasification slag and coal gangue as the main raw materials. It is simple to prepare and its overall production cost is significantly lower than that of existing flowability improvers. It also improves flowability quickly and promotes the resource utilization of industrial solid waste. Furthermore, under the "dual carbon" target, the solid waste utilization of this invention greatly reduces carbon emissions and pollution to the ecological environment, and has great practical application value. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the consistency detection of coal gasification slag slurry according to the present invention; Figure 2 This is a schematic diagram illustrating the implementation of the fluidity measurement of coal gasification slag slurry according to the present invention; Figure 3 The graph shows the variation of the diameter and viscosity of the packing slurry cake for coal gasification slag with the amount of calcium chloride added. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0023] Example Referring to Table 1, a coal gasification slurry was prepared by weighting 7 parts coal gasification slag, 2 parts coal gangue, 1 part cement, and 2.5 parts water. The anhydrous calcium chloride content was set at 0%, 1%, 2%, 3%, and 4% of the coal gasification slag mass, respectively. Taking the coal gasification slag filling slurry without anhydrous calcium chloride powder as Example 1, the flow properties of the coal gasification slag filling slurry with 1% anhydrous calcium chloride powder (Example 2), 2% anhydrous calcium chloride powder (Example 3), 3% anhydrous calcium chloride powder (Example 4), and 4% anhydrous calcium chloride powder (Example 5) were determined at room temperature.

[0024] A method for improving the flow properties of coal gasification slag filling slurry using calcium chloride, wherein each component consists of the following raw materials in parts by mass: Table 1. Gasification Slag Backing Slurry Examples 1-5 of methods for improving the flow properties of coal gasification slag filling slurry using calcium chloride include the following steps: (1) Pretreatment of coal gasification residue: Collect the solid residue after coal gasification and remove impurities such as gravel and leaves mixed in during the coal gasification process by passing it through a 3mm square hole sieve. (2) Pretreatment of calcium chloride: The refined neutral calcium chloride solution is sprayed into a mist through a nozzle from the top of the spray drying tower and dried and dehydrated by countercurrent contact with a 300°C hot air stream to obtain powdered anhydrous calcium chloride. (3) Preparation of coal gasification slag filling slurry: Weigh each raw material according to the designed raw material mass fraction, and put water, cement, coal gangue and coal gasification slag into the mixer in sequence. Stir at low speed for 60s at room temperature, stir at high speed for 30s, stop stirring for 90s, and scrape the slurry on the blades, pot wall and pot bottom into the pot with a scraper. Then stir at high speed for 60s to obtain coal gasification slag filling slurry. (4) Add the designed mass fraction of calcium chloride to the coal gasification slag filling slurry prepared above and stir evenly; (5) The consistency of the slurry is tested according to the method for testing the consistency of coal gasification slag slurry, including the following steps: ① Moisten the inner wall of the consistency cylinder and other tools, place the consistency cylinder on a rigid horizontal base plate that does not absorb water, and evenly fill the cylinder with the coal gasification slag filling slurry sample mixed with calcium chloride. Use a tamping rod to evenly tamp the slurry 25 times from the outside to the center in a spiral direction. ② When pouring the top layer, the slurry should be poured to a height above the cylinder opening. After the top layer is tamped, scrape off the excess slurry and smooth it with a trowel. ③ After removing the slurry from the bottom plate of the cylinder, lift the consistency cylinder vertically and steadily. The slurry forms a cake on the horizontal bottom plate. Measure the spreading diameter of the cake on the experimental table, measure a maximum value and a minimum value, and take the average value as the spreading diameter of the cake. ④ Measure the diameter of the spread-out material cake, see Table 2: Table 2. Diameter of gasification slag cake spread out in Examples 1-5 (mm) As shown in Table 2, calcium chloride can effectively improve the flow properties of coal gasification slag filling slurry.

[0025] (6) The consistency of the coal gasification slag slurry was determined based on the diameter of the spread coal gasification slag cake, and the results are shown in Table 3: Table 3. Judging the consistency of coal gasification slag slurry by the spread diameter of coal gasification slag cakes in Examples 1-5. The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for improving the flow properties of coal gasification slag filling slurry using calcium chloride, characterized in that: Includes the following steps: The first step is the pretreatment of coal gasification slag: collect the solid residue after coal gasification, perform carbon capture and removal, and remove gravel, leaves and other impurities mixed in during the coal gasification process by passing it through a 3mm square hole sieve. The second step is calcium chloride pretreatment: the refined neutral calcium chloride solution is sprayed into a mist from the top of the spray drying tower through a nozzle, and dried and dehydrated by countercurrent contact with a 300°C hot air stream to obtain powdered anhydrous calcium chloride. The third step is the preparation of the coal gasification slag filling slurry: According to the designed raw material mass fractions, weigh each raw material, and put water, cement, coal gangue and coal gasification slag into the mixer in sequence. At room temperature, stir at a speed of 57-67 r / min for 60s, stir at 115-135 r / min for 30s, stop stirring for 90s, and use a scraper to scrape the slurry on the blades, pot wall and pot bottom into the pot. Then stir at 115-135 r / min for 60s to obtain the coal gasification slag filling slurry. The coal gangue is crushed using a jaw crusher, and then screened using vibrating screens of 5mm, 10mm and 15mm respectively to obtain fine aggregate of 0-5mm, medium aggregate of 5-10mm and coarse aggregate of 10-15mm; the mass ratio of coal gangue to coarse aggregate: medium aggregate: fine aggregate = 1:1:

3. The cement is P.O42.5 silicate cement; The density of the coal gasification slag is 2.13 g / cm³. 3 The particle size range is 0.5–2.0 mm; the specific surface area of ​​the cement is 349 m². 2 / kg, density is 3.1g / cm³ 3 ; The coal gasification slag filling slurry comprises the following components in parts by weight: 7-9 parts coal gasification slag, 2-4 parts coal gangue, 1-2 parts cement, 2.5-3 parts water, and 0.07-0.09 parts calcium chloride; The fourth step is to add the designed mass fraction of calcium chloride to the coal gasification slag filling slurry prepared above and stir it evenly.

2. The method for improving the flow properties of coal gasification slag filling slurry using calcium chloride according to claim 1, characterized in that: The coal gasification slag filling slurry comprises the following components in parts by weight: 7 parts coal gasification slag, 2 parts coal gangue, 1 part cement, 2.5 parts water, and 0.07 parts calcium chloride.

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