Method for producing cementitious material for mine filling and method for filling using the cementitious material

Abstract

The present application relates to a preparation method of cementing material for mine filling and a filling method of the cementing material, comprising: using mining tailings, calcium-containing solid waste, aluminum correction material and iron correction material to prepare mixed raw materials, after crushing and grinding, raw materials are obtained; calcining the raw materials to obtain clinker and flue gas containing CO2; when grinding the clinker, input the flue gas to make the clinker have carbonization reaction; then add gypsum to prepare the cementing material. The filling method comprises: mixing the cementing material with tailings aggregate, water and additive, inputting the flue gas to prepare the filling slurry; the filling slurry is transported to the filling well, the flue gas is mixed with the transported filling slurry; then the filling slurry is input to the underground goaf through the slurry pipeline, the flue gas is input to the underground goaf through the gas pipeline, and filling is carried out.

Description

Technical Field

[0001] This invention belongs to the field of mine void management technology, specifically relating to the preparation method of cementitious material for mine backfilling and the backfilling method of the cementitious material. Background Technology

[0002] Cemented backfilling in mines is a crucial technology for controlling ground pressure, disposing of tailings, improving resource recovery rates, and ensuring safe production in underground mines. Unlike building materials, cementitious materials used in mine backfilling place greater emphasis on low cost, compatibility with tailings aggregates, moderate early strength, low heat of hydration, and good slurry fluidity and pumpability. Backfilling projects involve large quantities of cementitious materials, with concentrated consumption; their performance and cost directly impact the operational efficiency of the backfilling system and the economic viability of mine production.

[0003] At present, ordinary Portland cement is commonly used in mine backfilling systems. Although this type of material can meet certain strength requirements, it still has the following shortcomings: (1) Traditional cement clinker has a high firing temperature, high energy consumption, and high carbon emissions; (2) Ordinary cement has a fast early reaction and high heat of hydration, which can easily lead to unnecessary heat accumulation and volume stability problems under large volume backfilling conditions.

[0004] In existing technologies, although there have been studies and applications of using industrial solid waste to prepare cement or cementitious materials, most of them focus on replacing part of the clinker in the form of admixtures, still rely on a high proportion of traditional cement clinker systems, and rarely take into account the actual requirements of mine backfilling for workability, low heat resistance and medium-low strength development for targeted design. Summary of the Invention

[0005] To address the above problems, the present invention provides a method for preparing a cementitious material for mine backfilling and a method for filling with the cementitious material. In a first aspect, the method for preparing the cementitious material for mine backfilling includes:

[0006] S1: A mixed raw material is prepared using mining tailings, calcium-containing solid waste, aluminum corrective material and iron corrective material. After crushing and grinding, the mixed raw material is used to obtain raw meal.

[0007] S2: The raw materials are calcined to obtain clinker and flue gas containing CO2;

[0008] S3: During the grinding process of clinker, the flue gas is introduced to cause the clinker to undergo a carbonization reaction; then gypsum is added to obtain the cementitious material.

[0009] Optionally, in step S1, the mining tailings are selected from one or more of iron tailings, copper tailings, gold tailings, molybdenum tailings, and lead-zinc tailings; the calcium-containing solid waste is selected from one or more of steel slag, ore slag, carbide slag, desulfurization slag, carbide slag, and limestone tailings.

[0010] The aluminum corrective material is selected from one or more of fly ash, red mud, and bauxite tailings; the iron corrective material is selected from one or more of iron tailings, steel slag, iron slag, and iron-containing sludge.

[0011] Mining tailings serve as the primary siliceous raw material, while calcium-containing solid waste serves as the primary calcareous raw material. The complementary nature of these two components increases the proportion of mining solid waste used in the preparation of cementitious materials. Aluminum and iron corrective agents are introduced to adjust the proportions of calcium, silicon, aluminum, and iron components in the raw materials.

[0012] Optionally, in step S1, the amount of mining tailings used is 30-80 parts by mass, the amount of calcium-containing solid waste used is 10-60 parts by mass, the amount of aluminum corrective material used is 1-10 parts by mass, and the amount of iron corrective material used is 1-10 parts by mass.

[0013] Optionally, in step S1, the raw materials of each component after batching are mixed evenly to obtain mixed raw materials, which are then crushed, ground and homogenized to obtain raw materials with stable composition.

[0014] The above-mentioned powder should be ground to an 80μm sieve with a residue of no more than 20%, or the specific surface area of ​​the raw material should be controlled to be 250-500 m². 2 / kg. By controlling the fineness of the raw meal, the siliceous components in the mining tailings, the calcium components in the calcium-containing solid waste, and the aluminum and iron components in the corrective material are fully contacted, thereby improving the uniformity of the raw meal reaction and the stability of the clinker firing.

[0015] This invention utilizes grinding to increase the contact between siliceous components and calcium-containing solid waste in mining tailings, thereby improving the combustibility of raw materials. Homogenization is used to reduce the impact of fluctuations in the composition of solid waste from different sources on clinker mineral formation. Based on the characteristics of low activity and uneven particle size distribution of siliceous components in mining tailings, this invention controls the fineness and homogenization degree of raw materials to promote the reaction between calcium and siliceous components during subsequent firing, reduce the free calcium oxide content in the clinker, and improve the stability of the cementitious material.

[0016] Optionally, in step S2, the raw material is fed into a conventional calcining device for calcination at a temperature of 1150-1350℃ and a holding time of 10 min to 90 min. After calcination, the clinker is cooled and then enters the grinding process in step S3.

[0017] The calcination device is selected from one of the following: decomposition furnace, rotary kiln, vertical furnace, and fluidized bed furnace.

[0018] After firing, the raw meal forms a clinker system with belite minerals, aluminoferrate minerals, and / or calcium aluminate minerals as the main cementing active components. This system is used to meet the requirements of mine backfill materials for low heat of hydration, moderate early strength, sustained strength development in the later stages, and low-cost preparation. By controlling the firing temperature and holding time, belite minerals, aluminoferrate minerals, and / or calcium aluminate minerals are formed in the clinker, and the content of free calcium oxide in the clinker is reduced.

[0019] Optionally, in step S2, the flue gas generated during the clinker calcination process is collected, and the flue gas contains CO2; the flue gas is then treated by dust removal, cooling, humidity adjustment, pressure stabilization and / or necessary desulfurization and denitrification, and used as the gas source for step S3.

[0020] Optionally, in step S3, the clinker is ground, and during the grinding process, the treated flue gas is continuously or intermittently fed into the grinding device so that the CO2 in the flue gas reacts with the reactive calcium phase in the clinker in a controlled carbonization reaction to form calcium carbonate and silica gel, thereby improving the reactivity of the clinker; this is the first stage of flue gas utilization, namely carbon mineralization utilization in the cementitious material preparation stage.

[0021] The carbonized powder is ground or mixed with gypsum to obtain the cementitious material.

[0022] Further optionally, in step S3, the volume fraction of CO2 in the flue gas is 5-20%, the moisture content of the clinker powder is 0.5-3%, and the grinding temperature is 30-50℃;

[0023] When the average particle size of the clinker powder reaches 100 mesh, flue gas is introduced until the grinding is completed; the ratio of flue gas flow rate to clinker powder mass is (10-30) ml / min: 1g.

[0024] The controlled carbonization reaction does not aim to completely carbonize the clinker, but rather to regulate the early hydration activity, water demand, setting time, and micro-filling effect of the cementitious material through limited reaction between flue gas and clinker powder. By controlling the above process conditions, limited carbonization occurs between the flue gas and the reactive calcium phase in the clinker powder, preventing excessive overall carbonization of the clinker. Specifically, this invention also studied the specific parameters of the flue gas input, finding that to achieve a suitable carbonization effect, a dual coordination of clinker powder and flue gas is required. The clinker powder is first ground to a certain degree (i.e., the average particle size reaches 100 mesh), resulting in a large specific surface area. At this point, flue gas is introduced, allowing it to fully react with the clinker powder surface. Subsequently, as the powder continues to be ground, the flue gas continues to react with the newly exposed powder surface, thus fully utilizing the CO2 in the flue gas. Furthermore, the volume fraction of CO2 in the flue gas and the flue gas flow rate parameters must be coordinated to achieve a suitable degree of carbonization. The grinding device is equipped with an exhaust port to discharge excess waste gas.

[0025] Further optionally, in step S3, the gypsum is selected from one or more of natural gypsum, desulfurized gypsum, phosphogypsum, titanium gypsum, and fluorogypsum;

[0026] The amount of gypsum used is 3-15 wt% based on the total mass of the cementing material. The specific surface area of ​​the cementing material is 300-600 m². 2 / kg.

[0027] Secondly, the filling method of the cementitious material includes:

[0028] (i) The cementitious material is mixed with tailings aggregate, water and additives, and then introduced into the flue gas to prepare a filling slurry;

[0029] (ii) The filling slurry is transported to the filling well through the above-ground pipeline in the mining area, and the flue gas is input into the above-ground pipeline and mixed with the transported filling slurry;

[0030] (iii) The filling slurry of the mixed flue gas obtained in step (ii) is input into the underground goaf through the slurry pipeline, and the flue gas is input into the underground goaf through the gas pipeline for filling; both the slurry pipeline and the gas pipeline extend into the underground goaf through the filling well.

[0031] In this invention, the flue gas collected and processed in step S2 is introduced into the filling slurry preparation process, the filling slurry transportation process (it can also be introduced into the filling slurry temporary storage silo), and the filling process of underground goaf areas. Steps (I), (II), and (III) above represent the second, third, and fourth stages of utilization of the flue gas, that is, carbon mineralization utilization during the mine filling stage. CO2 in the flue gas reacts with mineralizable components such as calcium and magnesium in the filling slurry to form carbonate mineralization products, thereby improving the density and early bearing capacity of the filling body, while simultaneously achieving CO2 consolidation.

[0032] Optionally, in step (i), the tailings aggregate is selected from one or more of whole tailings, graded tailings, and waste rock fines; the admixture is selected from one or more of water-reducing agents, retarders, early-strength agents, thickeners, foam stabilizers, and dispersants.

[0033] The mass concentration of the filling slurry is 60-78%, and the mass ratio of cementitious material to tailings aggregate (mortar ratio) is 1:(4-12).

[0034] Further optionally, in step (i), the flue gas is introduced during the overall process of preparing the filling slurry, and the ratio of the flow rate of the flue gas to the total volume of the filling slurry is (25-35) ml / min: 100 ml.

[0035] Flue gas is introduced into the filling slurry preparation process. The flue gas reacts with the hydration products of the cementitious materials and the unreacted calcium phase to improve the slurry's early structural formation ability. By adjusting the slurry's mass concentration, mortar ratio, and the amount of flue gas introduced, the filling slurry can meet the requirements for pipeline transportation, goaf filling, and hardening strength. Flue gas can be introduced into the tank used to prepare the filling slurry below the liquid level through a gas pipe.

[0036] Optionally, the initial fluidity of the filling slurry is 160-300 mm, and after being stirred, the filling slurry sequentially enters the temporary storage bin, the filling pump, the ground / dedicated pipeline, and the goaf.

[0037] Optionally, in step (ii), several interfaces are evenly arranged along the length of the above-ground pipeline, each interface connecting to the outlet of a jet mixer. The flue gas is connected to the gas inlet of the jet mixer through a pipeline, and the water source is connected to the liquid inlet of the jet mixer. The flue gas and water are mixed in the jet mixer and then fed into the filling slurry of the above-ground pipeline. The flow rates of the flue gas and water are adjusted according to the actual situation.

[0038] The flue gas remains in continuous contact with the filling grout within the above-ground pipeline to achieve in-situ carbon mineralization during transport. In step (II), the flue gas is not directly introduced into the above-ground pipeline; instead, it is first mixed with water, causing some CO2 to dissolve and generating a certain amount of carbonate ions. This facilitates direct reaction with the filling grout after the flue gas is introduced into the above-ground pipeline. Furthermore, this method promotes rapid and uniform diffusion of the flue gas within the filling grout, preventing mixing issues that could result from directly introducing the flue gas into the grout within the above-ground pipeline.

[0039] Optionally, step (iii) specifically includes:

[0040] (1) Determine the scope and boundary of the underground goaf area, drill several vertical shafts evenly at the boundary of the goaf area, and drill several filling shafts evenly inside the mining area; both the vertical shafts and the filling shafts extend vertically from the ground to the underground goaf area.

[0041] (2) The bottom end of the bottom section of the filling well is provided with a horizontal cap, and the center of the cap is provided with a first through hole, allowing the bottom of the slurry pipe to pass through the first through hole to exit the filling well;

[0042] Several second through holes are provided around the outer side of the first through hole. Each second through hole corresponds to a gas pipeline, allowing the gas pipeline to pass through the corresponding second through hole to exit the filling well.

[0043] (3) Concrete is poured into the boundary of the goaf through the vertical shaft to seal the boundary;

[0044] (4) The flue gas is introduced into the goaf through the gas pipeline; then, the filling slurry is introduced into the goaf through the slurry channel to fill the goaf.

[0045] Optionally, in step (2), when the bottom section of the filling well is on the ground, the cap is fixedly installed at the bottom end of the well section, and the edge of the cap is sealed to the edge of the well section.

[0046] The first through hole is concentrically set with the cap and filling well, and the diameter of the first through hole is slightly larger than the outer diameter of the slurry pipe; several second through holes are evenly set along the circumference of the cap, and the diameter of the second through holes is slightly larger than the outer diameter of the gas pipe.

[0047] Further optionally, in step (2), the slurry pipeline is composed of several sections of branch pipes connected end to end. After the filling well is completed, the branch pipes are connected section by section during the lowering process, so that the bottom of the bottommost branch pipe passes through the first through hole to exit the filling well, and the top of the topmost branch pipe passes through the filling well opening and connects to the ground pipeline; the topmost branch pipe is connected to the support device near the filling well opening to support the entire slurry pipeline.

[0048] Alternatively, the lower part of the outer wall of the bottommost branch pipe is provided with an outwardly protruding limiting component. The limiting component is a horizontal ring, with its inner side fixedly connected to the outer wall of the branch pipe and its outer side pointing towards the inner wall of the filling well.

[0049] A sealing gasket is laid on the lower surface of the limiting component. The sealing gasket is circular, with its inner side tightly attached to the outer wall of the branch pipe and its outer diameter larger than the diameter of the first through hole. This ensures that the sealing gasket can cover the gap between the first through hole and the outer wall of the bottommost branch pipe, thus ensuring the sealing performance at the first through hole.

[0050] Further optionally, the outer wall of the slurry pipe is provided with several limiting rings, which are horizontal and concentric with the slurry pipe, and the several limiting rings are arranged sequentially and evenly from top to bottom;

[0051] The limiting ring has a locking part at the position of the corresponding gas pipe to limit the position of the gas pipe, so that the gas pipe enters the filling well together with the slurry pipe.

[0052] Optionally, the outer edge of the limiting component is provided with several recesses, each of which corresponds to a gas pipe. The upper surface of the recess is curved, and the four edges are also smooth curved surfaces, which are used to push the gas pipe passing through the limiting component toward the inner wall of the filling well.

[0053] Optionally, in step (4), flue gas is introduced into the goaf through the gas pipelines of all filling wells, and the total amount of flue gas introduced is in the ratio of the volume of the goaf to the volume of (0.4-0.5):1.

[0054] This invention introduces CO2-containing flue gas during the grinding of clinker powder, the preparation of filling slurry, and the slurry transportation. Even with adjustments to process parameters and the use of jet mixers in these steps to maximize the reaction between CO2 and related substances, the inherent properties of the powder and slurry prevent the reaction from being fully effective (this is an inherent physicochemical property of the substances, difficult to change). This invention innovatively introduces flue gas into the goaf simultaneously during the filling slurry injection process, a groundbreaking measure that further compensates for the shortcomings of previous steps.

[0055] The flue gas is introduced into the goaf backfill during the initial setting to hardening stage, so that the carbon mineralization reaction is coordinated with the setting and hardening process of the backfill slurry. Specifically, the flue gas enters the pores of the backfill in the initial setting, final setting, or early hardening stage, and undergoes a mineralization reaction with the alkaline components therein to improve the compactness of the backfill and the CO2 retention.

[0056] In this invention, the flue gas is utilized in a segmented and coupled manner (the four stages of utilization mentioned above) to achieve the synergistic effect of on-site reuse of flue gas during the preparation of cementitious materials, performance regulation of filling colloids, CO2 mineralization and storage, and resource utilization of mining solid waste. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of the internal structure of the filling well;

[0058] Figure 2 This is a schematic diagram of the sealing area;

[0059] Figure 3 This is a schematic diagram of a seal.

[0060] Among them, 1-cap, 2-first through hole, 3-second through hole, 4-filling well, 5-limiting ring, 6-clamping part, 7-limiting component, 8-pit, 9-seal, 10-seal gasket, 11-slurry pipe, 12-gas pipe, 13-branch pipe. Detailed Implementation

[0061] Example 1

[0062] This embodiment provides a method for preparing cementitious materials for mine backfilling, including:

[0063] S1: A mixed raw material is prepared using mining tailings, calcium-containing solid waste, aluminum corrective material and iron corrective material. After crushing and grinding, the mixed raw material is used to obtain raw meal.

[0064] S2: The raw materials are calcined to obtain clinker and flue gas containing CO2;

[0065] S3: During the grinding process of clinker, the flue gas is introduced to cause the clinker to undergo a carbonization reaction; then gypsum is added to obtain the cementitious material.

[0066] In step S1, the mining tailings include iron tailings, copper tailings, and lead-zinc tailings; the calcium-containing solid waste includes steel slag, ore slag, and carbide slag; the aluminum corrective material includes fly ash, red mud, and bauxite tailings; and the iron corrective material includes iron tailings and iron slag. The masses of each component in the following mining tailings, calcium-containing solid waste, aluminum corrective material, and iron corrective material are equal.

[0067] The amount of the mining tailings used is 30 parts by weight, the amount of calcium-containing solid waste used is 60 parts by weight, the amount of aluminum corrective material used is 10 parts by weight, and the amount of iron corrective material used is 10 parts by weight.

[0068] In step S1, the raw materials of each component after batching are mixed evenly to obtain mixed raw materials, which are then crushed, ground and homogenized to obtain raw materials with stable composition.

[0069] The raw material is ground until the residue on an 80μm sieve is no more than 20%, and the specific surface area of ​​the raw material is controlled to be 300m². 2 / kg.

[0070] In step S2, the raw material is fed into a conventional rotary kiln for calcination at a firing temperature of 1150°C and a holding time of 90 min. After calcination, the clinker is cooled and then enters the grinding process in step S3.

[0071] In step S2, the flue gas generated during the clinker calcination process is collected. The flue gas contains CO2. After conventional dust removal, cooling, humidity adjustment, pressure stabilization and desulfurization and denitrification treatment, the flue gas is used as the gas source for step S3.

[0072] In step S3, the clinker is ground, and during the grinding process, the treated flue gas is continuously fed into the grinding device so that the CO2 in the flue gas reacts with the reactive calcium phase on the surface of the clinker in a controlled carbonization reaction to form calcium carbonate mineral products; the carbonized powder is ground or mixed with gypsum to obtain the cementitious material.

[0073] The volume fraction of CO2 in the flue gas is 5%, the moisture content of the clinker powder is 0.5%, and the grinding temperature is 30℃.

[0074] When the average particle size of the clinker powder reaches 100 mesh, flue gas is introduced until the grinding is completed (at the end, the average particle size of the clinker powder is 200 mesh); the ratio of flue gas flow rate to clinker powder mass is 10 ml / min: 1 g.

[0075] In step S3, the gypsum includes natural gypsum, desulfurized gypsum, and phosphogypsum (each component has an equal mass).

[0076] The amount of gypsum used is 8 wt% based on the total mass of the cementing material. The specific surface area of ​​the cementing material is 500 m². 2 / kg.

[0077] Comparative Example 1

[0078] This comparative example provides a method for preparing cementitious materials for mine backfilling, which is the same as that in Example 1. The difference is that in step S3, the flue gas generated in step S2 is not input into the clinker during the grinding process, and gypsum is directly added after grinding to obtain the cementitious material.

[0079] Example 2

[0080] This embodiment provides a method for preparing cementitious materials for mine backfilling, which is the same as in Embodiment 1, except that in step S1, the amount of mining tailings is 80 parts by mass, the amount of calcium-containing solid waste is 10 parts by mass, the amount of aluminum corrective material is 1 part by mass, and the amount of iron corrective material is 1 part by mass.

[0081] Example 3

[0082] This embodiment provides a method for preparing cementitious materials for mine backfilling, which is the same as in Embodiment 1, except that in step S1, the amount of mining tailings is 29 parts by mass, the amount of calcium-containing solid waste is 61 parts by mass, the amount of aluminum corrective material is 1 part by mass, and the amount of iron corrective material is 1 part by mass.

[0083] Example 4

[0084] This embodiment provides a method for preparing cementitious materials for mine backfilling, which is the same as in Embodiment 1, except that in step S3, the volume fraction of CO2 in the flue gas is 20%.

[0085] Example 5

[0086] This embodiment provides a method for preparing cementitious materials for mine backfilling, which is the same as in Embodiment 1, except that in step S3, the volume fraction of CO2 in the flue gas is 4%.

[0087] Example 6

[0088] This embodiment provides a method for preparing cementitious materials for mine backfilling, which is the same as that in embodiment 1, except that in step S3, the moisture content of the clinker powder is 3% and the grinding temperature is 50°C.

[0089] Example 7

[0090] This embodiment provides a method for preparing cementitious materials for mine backfilling, which is the same as in Embodiment 1, except that in step S3, the ratio of flue gas flow rate to clinker powder mass is 30 ml / min: 1 g.

[0091] Example 8

[0092] This embodiment provides a method for preparing cementitious materials for mine backfilling, which is the same as in embodiment 1, except that in step S3, the ratio of flue gas flow rate to clinker powder mass is 9 ml / min: 1 g.

[0093] Example 9

[0094] This embodiment provides a method for preparing cementitious materials for mine backfilling, which is the same as in embodiment 1, except that in step S3, flue gas is introduced when the clinker powder just begins to be ground.

[0095] The compressive strength of the cementitious materials prepared in Examples 1-9 and Comparative Example 1 after curing at room temperature on the ground for 28 days is shown in the table below.

[0096] Table 1. Performance comparison of the cementitious materials prepared in Examples 1-9 and Comparative Example 1

[0097]

[0098] The experimental results of Example 9 are comparable to those of Example 1. However, Example 9 uses a larger amount of flue gas and produces more waste gas, wasting some flue gas. Therefore, the method of Example 1 is superior.

[0099] Example 10

[0100] This embodiment provides a method for filling the cementitious material, including:

[0101] (i) The cementitious material prepared in Example 1 is mixed with tailings aggregate, water and additives, and then introduced into the flue gas to prepare a filling slurry;

[0102] (ii) The filling slurry is transported to the filling well through the above-ground pipeline in the mining area, and the flue gas is input into the above-ground pipeline and mixed with the transported filling slurry;

[0103] (iii) The filling slurry of the mixed flue gas obtained in step (ii) is input into the underground goaf through the slurry pipeline, and the flue gas is input into the underground goaf through the gas pipeline for filling; both the slurry pipeline and the gas pipeline extend into the underground goaf through the filling well.

[0104] In step (1), the tailings aggregate includes whole tailings and waste rock fines; the admixtures include 1 wt% water-reducing agent (equal mass of polycarboxylate high-efficiency water-reducing agent, naphthalene water-reducing agent, lignin sulfonate) and 1.5 wt% early strength agent (equal mass of CaCl2, water glass, triethanolamine).

[0105] The mass concentration of the filling slurry is 60%, and the mass ratio of cementitious material to tailings aggregate is 1:4.

[0106] In step (i), the flue gas is introduced during the overall process of preparing the filling slurry, and the ratio of flue gas flow rate to the total volume of the filling slurry is 25 ml / min: 100 ml. The flue gas is introduced into the tank for preparing the filling slurry below the liquid level through a gas pipe.

[0107] The initial fluidity of the filling slurry is 200 mm. After being stirred, the filling slurry enters the temporary storage bin, the filling pump, the ground / dedicated pipeline, and the goaf in sequence.

[0108] In step (ii), four interfaces (including the interface at the outlet of the filling pump) are evenly arranged along the length of the above-ground pipeline. Each interface is connected to the outlet of a jet mixer. The flue gas is connected to the gas inlet of the jet mixer through a pipeline, and the water source is connected to the liquid inlet of the jet mixer (inlet water pressure 0.2–0.6 MPa). The flue gas is drawn into the jet mixer and mixed with water in the jet mixer, and then input into the filling slurry of the above-ground pipeline.

[0109] like Figures 1-3 As shown, step (iii) specifically involves:

[0110] (1) Using existing technology to conduct surveys, and combining historical mining and exploration data, determine the scope and boundary of the underground goaf area. Drill five vertical shafts evenly at the boundary of the goaf area and drill three filling shafts evenly inside the mining area. Both the vertical shafts and the filling shafts extend vertically from the ground to the underground goaf area.

[0111] (2) A horizontal cap 1 is provided at the bottom of the bottom section of the filling well 4. A first through hole 2 is provided in the center of the cap, allowing the bottom of the slurry pipe 11 to pass through the first through hole and exit the filling well.

[0112] Three second through holes 3 are provided around the outer side of the first through hole. The second through holes correspond one-to-one with the gas pipe 12, allowing the gas pipe to pass through the corresponding second through hole to exit the filling well.

[0113] (3) Concrete is poured into the boundary of the goaf through the vertical shaft to seal the boundary;

[0114] (4) The flue gas is introduced into the goaf through the gas pipeline; then, the filling slurry is introduced into the goaf through the slurry channel to fill the goaf.

[0115] In step (1), the drilling of the vertical shaft and the filling well can be carried out using the existing vertical shaft drilling, cementing and completion technologies in the field of goaf treatment.

[0116] In step (2), when the bottom section of the filling well is on the ground, the cap is fixedly installed at the bottom of the well section, and the edge of the cap is sealed with the edge of the well section to prevent the filling slurry and flue gas with a certain pressure from entering the filling well when filling the goaf.

[0117] The first through hole is concentrically set with the cap and filling well, and the diameter of the first through hole is slightly larger than the outer diameter of the slurry pipe; the three second through holes are evenly set along the circumference of the cap, and the diameter of the second through hole is slightly larger than the outer diameter of the gas pipe.

[0118] In step (2), the slurry pipeline is composed of several sections of branch pipe 13 connected end to end. After the filling well is completed, the branch pipes are connected section by section during the lowering process, so that the bottom of the bottom branch pipe passes through the first through hole to exit the filling well, and the top of the top branch pipe passes through the filling well opening and connects to the ground pipeline; the top branch pipe is connected to the support device near the filling well opening to support the entire slurry pipeline.

[0119] The outer wall of the bottommost branch pipe is provided with an outwardly protruding limiting component 7. The limiting component is a horizontal ring, with its inner side fixedly connected to the outer wall of the branch pipe and its outer side pointing towards the inner wall of the filling well.

[0120] A sealing gasket 10 is laid on the lower surface of the limiting component. The sealing gasket is circular, with its inner side tightly attached to the outer wall of the branch pipe and its outer diameter being larger than the diameter of the first through hole. This ensures that the sealing gasket can cover the gap between the first through hole and the outer wall of the bottommost branch pipe, thus ensuring the sealing performance at the first through hole.

[0121] After the bottom of the slurry pipe passes through the first through hole, the limiting component and the sealing gasket are supported by the cap. Under the action of the slurry pipe's own weight and the cooperation of the limiting component, the sealing gasket seals the first through hole, preventing slurry and flue gas in the goaf from entering the filling well.

[0122] The outer wall of the slurry pipe is provided with three limiting rings 5. The limiting rings are horizontal and concentric with the slurry pipe. The three limiting rings are arranged evenly from top to bottom.

[0123] The limiting ring is provided with a locking part 6 at the position of the corresponding gas pipe, which is used to limit the position of the gas pipe so that the gas pipe enters the filling well together with the slurry pipe.

[0124] The outer edge of the limiting component has three recesses 8, each corresponding to a gas pipe. The upper surface of the recess is curved, and the four edges are also smooth curved surfaces, which are used to push the gas pipe passing through the limiting component 7 toward the inner wall of the filling well.

[0125] The gas pipeline is made of deformable plastic, capable of bending under external force, and maintaining its shape without deformation when no external force is applied. The retaining ring can be integrally formed with the corresponding branch pipe, or it can be subsequently installed on the branch pipe. When connecting the branch pipes of the slurry pipeline, the three gas pipelines are simultaneously snapped into the corresponding retaining ring's snap-fit ​​portion, thus assembling the branch pipes and gas pipelines. The branch pipes and gas pipelines are lowered together into the filling well.

[0126] When assembling on the ground, the bottom of the gas pipe is bent into an inclined shape in advance, with the bottom end of the gas pipe extending beyond the bottom end of the lowest branch pipe and extending outward. The corresponding limiting component of the gas pipe fits into the corresponding recess. Further up, the inclined gas pipe extends to the outer wall of the branch pipe. Further up, the gas pipe is parallel to the branch pipe and laid along the outer wall of the branch pipe. When it encounters the limiting ring, the gas pipe is detachably connected to the corresponding snap-fit ​​part.

[0127] As the bottommost branch pipe approaches the first through hole, each gas pipe also approaches its corresponding second through hole. The bottom end of the gas pipe preferentially passes through the second through hole, whose internal channel is inclined. This allows the bottom end of the gas pipe to also exit the second through hole as the branch pipe is lowered. Then, the bottom end of the branch pipe exits the first through hole.

[0128] After the slurry pipeline is lowered and positioned, the top of the gas pipeline extends out of the filling well opening, and there is a certain length of gas pipeline on the ground (e.g., 3-5 meters), leaving a margin so that the gas pipeline can continue to extend into the goaf when the filling slurry is injected into the goaf.

[0129] Step (3) is a conventional method in this field and can be performed according to existing technology.

[0130] In step (4), following the above method, slurry pipes and gas pipes are installed and lowered into each filling well, with the bottom ends of the slurry pipes flush with the bottom ends of the corresponding three gas pipes;

[0131] Flue gas is introduced into the goaf through gas pipelines in all filling wells. If the goaf is deep and the ground stress is high, the flue gas is introduced under pressure. The total volume of flue gas introduced is 0.4:1 compared with the volume of the goaf.

[0132] Then, each filling well simultaneously inputs the filling slurry into the goaf. For a filling well, as the filling slurry spreads around the filling well, each gas channel corresponding to the filling well moves downward synchronously, and the gas channels extending out of the caps tilt and extend in all directions.

[0133] When the top surface of the filling grout in the goaf is about to touch the bottom of the gas pipe, retract all the gas pipes upwards until the bottom of the gas pipe is slightly lower than the lower surface of the cap.

[0134] In step (4), the flow rate of each slurry channel is the same, the gas flow rate and pressure of each gas pipe are the same, and the slurry flow rate and flue gas flow rate are determined according to the actual situation of the filling operation; the downward movement speed of each gas channel is also the same.

[0135] The volume of the goaf is known. By measuring the slurry flow rate in each slurry channel, the average liquid level in the goaf can be estimated, which in turn allows for control of when the gas pipeline rises. When the gas pipeline rises to the highest permissible position, the flue gas input is stopped and the top of the gas pipeline is sealed.

[0136] Regarding the method of raising and lowering the gas pipeline: This invention controls the raising and lowering of the top of the gas pipeline at the wellhead. The locking part only prevents the gas pipeline from moving away from the branch pipe, allowing the gas pipeline to move up and down within the locking part, and the locking part does not affect the diameter of the gas pipeline (i.e., it does not compress the gas pipeline). When the gas pipeline descends, its bottom contacts the corresponding recess (the surface of which is also an inclined curved surface), and it is pushed obliquely downward by the recess, thus passing through the second through hole at an inclined posture. When the gas pipeline rises, when it passes the bottom limiting ring, there is a funnel-shaped cavity below the locking part of this ring, which is smaller at the top and larger at the bottom, used to gradually straighten and reset the inclined outward gas pipeline so that the gas pipeline can smoothly pass through the various locking parts above when it rises subsequently.

[0137] A sealing element 9 is provided at the second through hole to prevent air leakage at the second through hole when the gas pipe through the second through hole is raised or lowered.

[0138] The seal is hollow and made of rubber, consisting of a central cylinder and rings at the top and bottom. Gas pipes can pass through the seal. The two rings are horizontal and can fit the upper and lower surfaces of the cap respectively. The cylinder is inclined to adapt to the internal shape of the second through hole.

[0139] The seal is pre-installed on the second through hole. The inner diameter of the cylinder is equal to the outer diameter of the gas pipe. Due to the seal's elasticity, the gas pipe is allowed to be inserted and pass through the seal, with the outer wall of the gas pipe tightly against the inner wall of the cylinder. The bottom end of the gas pipe is a wedge-shaped tip, making it easier to pass through the seal. When the gas pipe descends, it compresses and moves the seal downwards, with the upper annular plate tightly against the upper surface of the cap and supporting the seal (preventing the seal from coming out of the second through hole), ensuring the seal of the second through hole. When the gas pipe rises, it compresses and moves the seal upwards, with the lower annular plate tightly against the lower surface of the cap and supporting the seal (preventing the seal from coming out of the second through hole), also ensuring the seal of the second through hole.

[0140] Comparative Example 2

[0141] The comparative example provides a filling method for the gelling material, which is the same as that in Example 10, except that no flue gas is introduced in steps (i), (ii), and (iii).

[0142] Comparative Example 3

[0143] This comparative example provides a filling method for the cementitious material, which is the same as that in Example 10, except that no flue gas is introduced in steps (ii) and (iii).

[0144] Comparative Example 4

[0145] This comparative example provides a filling method for the cementitious material, which is the same as that in Example 10, except that no flue gas is introduced in step (iii).

[0146] Example 11

[0147] This embodiment provides a filling method for the cementitious material, which is the same as that in embodiment 10, except that in step (i), the mass concentration of the filling slurry is 78%.

[0148] Example 12

[0149] This embodiment provides a filling method for the cementitious material, which is the same as that in embodiment 10, except that in step (i), the mass concentration of the filling slurry is 59%.

[0150] Example 13

[0151] This embodiment provides a filling method for the cementitious material, which is the same as that in embodiment 10. The difference is that in step (1), the ratio of flue gas flow rate to the total volume of filling slurry is 35ml / min:100ml.

[0152] Example 14

[0153] This embodiment provides a filling method for the cementitious material, which is the same as that in embodiment 10. The difference is that in step (i), the ratio of flue gas flow rate to the total volume of filling slurry is 24 ml / min: 100 ml.

[0154] Example 15

[0155] This embodiment provides a filling method for the gelling material, which is the same as that in embodiment 10. The difference is that in step (two), no jet mixer is set up, but the flue gas is directly input into the ground pipeline through the interface.

[0156] Example 16

[0157] This embodiment provides a filling method for the cementitious material, which is the same as that in embodiment 10. The difference is that in step (4), flue gas is introduced into the goaf through the gas pipelines of all filling wells, and the total amount of flue gas introduced is 0.5:1 to the volume of the goaf.

[0158] Example 17

[0159] This embodiment provides a filling method for the cementitious material, which is the same as that in embodiment 10. The difference is that in step (4), flue gas is introduced into the goaf through the gas pipelines of all filling wells, and the total amount of flue gas introduced is 0.3:1 to the volume of the goaf.

[0160] Example 18

[0161] This embodiment provides a filling method for the cementitious material, which is the same as that in embodiment 10, except that in step (i), the mass ratio of the cementitious material to the tailings aggregate is 1:12.

[0162] Example 19

[0163] This embodiment provides a filling method for the cementitious material, which is the same as that in embodiment 10, except that in step (i), the mass ratio of the cementitious material to the tailings aggregate is 1:13.

[0164] Examples 10-19 and Comparative Examples 2-4 all used the cementitious material prepared in Example 1 to conduct filling experiments in underground goaf areas with a depth of 500 meters. The compressive strength after 28 days is shown in the table below.

[0165] Table 2 Comparison of filling effects between Examples 10-19 and Comparative Examples 2-4

[0166]

[0167] When cementitious materials are mixed with tailings aggregate and then used to fill underground goaf areas, their compressive strength after 28 days of curing is lower than that of cementitious materials cured alone after 28 days. However, the compressive strength of embodiments 10-19 of this invention still meets the requirements for filling underground goaf areas.

[0168] As can be seen from the above, in the filling method of the cementitious material provided by the present invention, the appropriate addition of flue gas containing carbon dioxide is beneficial to improving the final compressive strength.

Claims

1. A method for preparing cementitious materials for mine backfilling, characterized in that, include: S1: A mixed raw material is prepared using mining tailings, calcium-containing solid waste, aluminum corrective material and iron corrective material. After crushing and grinding, the mixed raw material is used to obtain raw meal. S2: The raw materials are calcined to obtain clinker and flue gas containing CO2; S3: During the grinding process of clinker, the flue gas is introduced to cause the clinker to undergo a carbonization reaction; then gypsum is added to obtain the cementitious material.

2. The preparation method according to claim 1, characterized in that, In step S1, the amount of mining tailings used is 30-80 parts by mass, the amount of calcium-containing solid waste used is 10-60 parts by mass, the amount of aluminum corrective material used is 1-10 parts by mass, and the amount of iron corrective material used is 1-10 parts by mass. In step S1, the raw materials of each component after batching are mixed evenly to obtain a mixed raw material, which is then crushed, ground, and homogenized to obtain a raw meal with stable composition; the above grinding is carried out until the residue on an 80μm sieve is no more than 20%, or the specific surface area of ​​the raw meal is controlled to be 250-500m². 2 / kg.

3. The preparation method according to claim 1, characterized in that, In step S3, the volume fraction of CO2 in the flue gas is 5-20%, the moisture content of the clinker powder is 0.5-3%, and the grinding temperature is 30-50℃. When the average particle size of the clinker powder reaches 100 mesh, flue gas is introduced until the grinding is completed; the ratio of flue gas flow rate to clinker powder mass is (10-30) ml / min: 1g.

4. The filling method of the cementitious material according to any one of claims 1-3, characterized in that, include: (i) The cementitious material is mixed with tailings aggregate, water and additives, and then introduced into the flue gas to prepare a filling slurry; (ii) The filling slurry is transported to the filling well through the above-ground pipeline in the mining area, and the flue gas is input into the above-ground pipeline and mixed with the transported filling slurry; (iii) The filling slurry of the mixed flue gas obtained in step (ii) is input into the underground goaf through the slurry pipeline, and the flue gas is input into the underground goaf through the gas pipeline for filling; both the slurry pipeline and the gas pipeline extend into the underground goaf through the filling well.

5. The filling method according to claim 4, characterized in that, In step (1), the flue gas is introduced during the overall process of preparing the filling slurry, and the ratio of the flow rate of the flue gas to the total volume of the filling slurry is (25-35) ml / min: 100 ml.

6. The filling method according to claim 4, characterized in that, In step (ii), several interfaces are evenly arranged along the length of the above-ground pipeline. Each interface is connected to the outlet of a jet mixer. The flue gas is connected to the gas inlet of the jet mixer through a pipeline, and the water source is connected to the liquid inlet of the jet mixer. The flue gas and water are mixed in the jet mixer and then fed into the filling slurry of the above-ground pipeline.

7. The filling method according to claim 4, characterized in that, Step (three) is as follows: (1) Determine the scope and boundary of the underground goaf area, drill several vertical shafts evenly at the boundary of the goaf area, and drill several filling shafts evenly inside the mining area; both the vertical shafts and the filling shafts extend vertically from the ground to the underground goaf area. (2) The bottom end of the bottom section of the filling well is provided with a horizontal cap, and the center of the cap is provided with a first through hole, allowing the bottom of the slurry pipe to pass through the first through hole to exit the filling well; Several second through holes are provided around the outer side of the first through hole. Each second through hole corresponds to a gas pipeline, allowing the gas pipeline to pass through the corresponding second through hole to exit the filling well. (3) Concrete is poured into the boundary of the goaf through the vertical shaft to seal the boundary; (4) The flue gas is introduced into the goaf through the gas pipeline; then, the filling slurry is introduced into the goaf through the slurry channel to fill the goaf.

8. The filling method according to claim 7, characterized in that, In step (2), when the bottom section of the filling well is on the ground, the cap is fixedly installed at the bottom end of the well section, and the edge of the cap is sealed to the edge of the well section. The first through hole is concentrically set with the cap and filling well, and the diameter of the first through hole is slightly larger than the outer diameter of the slurry pipe; several second through holes are evenly set along the circumference of the cap, and the diameter of the second through holes is slightly larger than the outer diameter of the gas pipe.

9. The filling method according to claim 8, characterized in that, In step (2), the slurry pipeline is composed of several sections of branch pipes connected end to end. After the filling well is completed, the branch pipes are connected section by section during the lowering process, so that the bottom of the bottom branch pipe passes through the first through hole to exit the filling well, and the top of the top branch pipe passes through the filling well opening and connects to the ground pipeline. The bottommost branch pipe has an outwardly protruding limiting component on the lower part of its outer wall. The limiting component is a horizontal ring, with its inner side fixedly connected to the outer wall of the branch pipe and its outer side pointing towards the inner wall of the filling well. A sealing gasket is laid on the lower surface of the limiting component. The sealing gasket is circular, with its inner side tightly attached to the outer wall of the branch pipe and its outer diameter larger than the diameter of the first through hole. This ensures that the sealing gasket can cover the gap between the first through hole and the outer wall of the bottommost branch pipe, thus ensuring the sealing performance at the first through hole.

10. The filling method according to claim 9, characterized in that, The outer wall of the slurry pipe is provided with several limiting rings. The limiting rings are horizontal and concentric with the slurry pipe. The several limiting rings are arranged sequentially and evenly from top to bottom. The limiting ring has a locking part at the corresponding position of the gas pipeline to limit the position of the gas pipeline; The outer edge of the limiting component has several recesses, each corresponding to a gas pipe. The upper surface of the recess is curved, and the four edges are also smooth curved surfaces, which are used to push the gas pipe passing through the limiting component toward the inner wall of the filling well.

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