A potash ore solid-liquid tailings filler and its preparation method

Abstract

This invention relates to the field of non-metallic mine backfilling technology, and particularly to a potash mine solid-liquid tailings-based backfill material and its preparation method. The preparation method of the backfill material includes: mixing potassium phosphate with tailings to obtain a phosphate brine solution; dry mixing composition 1 of a composite binder with the tailings to obtain a uniform dry material; adding the phosphate brine solution to obtain a uniform slurry 1; adding a mineral carrier-loaded slow-release alkali source to the uniform slurry 1 to obtain a uniform slurry 2; first adding a polycarboxylate superplasticizer to the uniform slurry 2 and mixing, then adding an associative thickener solution and mixing, and finally adding anionic polyacrylamide to obtain the backfill material. The backfill material prepared by this invention achieves a coordinated balance between slurry fluidity, anti-segregation, pumpability, and backfill strength, providing an economical, environmentally friendly, and efficient technical solution for backfilling non-metallic mine goaf areas.

Description

Technical Field

[0001] This invention relates to the field of non-metallic mine backfilling technology, to resource recycling and the inorganic non-metallic materials industry, and particularly to a potash mine solid-liquid tailings-based backfill material and its preparation method. Background Technology

[0002] Goaf areas of varying sizes are formed during underground non-metallic mineral mining. If these goaf areas are not addressed promptly, they can easily lead to problems such as surrounding rock instability, roof collapse, and surface deformation, affecting mine safety and normal mining operations. Therefore, filling goaf areas with backfill materials is an important technical method in underground non-metallic mineral mining.

[0003] In non-metallic minerals, potash mine goaf backfilling places high demands on the fluidity, stability, transportability, and strength of the backfill material. This is especially true in potash mine backfill systems primarily composed of tailings and old brine. Due to the coarse tailings particles, high salinity of the old brine, and high ion concentration in the system, phenomena such as old brine exudation, tailings sedimentation, and slurry segregation easily occur during the preparation and transportation of the backfill slurry, thus affecting the continuity and effectiveness of the backfilling operation.

[0004] Furthermore, the high-salt brine environment weakens the dispersion effect of commonly used additives, leading to enhanced particle flocculation, forming larger flocs that encapsulate unreacted powders, further deteriorating slurry flowability and reaction uniformity. Simultaneously, the reaction between magnesium chloride and magnesium oxide in the brine readily generates rapidly coagulating magnesium-based cementitious products, causing a rapid increase in viscosity of the filling slurry during pumping, posing a risk of pipe blockage. While existing potash mine backfilling technologies can meet the backfilling needs of mined-out areas to some extent, there is still a lack of targeted raw material formulation and preparation methods for coordinating anti-brine secretion, anti-segregation, flowability maintenance, and pumpability in high-salt brine-tailings salt systems.

[0005] Therefore, it is necessary to provide a filling material and its preparation method that is suitable for potash mine goaf areas, has good fluidity and stability, and is transportable, in order to meet the application requirements of potash mine goaf filling. Summary of the Invention

[0006] In view of this, the present invention proposes a potash mine solid-liquid tailings-based filling material and its preparation method. By synergistically combining multiple components in the composite binder with tailings, old brine, and PCE, PAM, etc., and through a stepwise addition process, the slow release of alkali source is controlled, significantly improving the stability, fluidity, and pumpability of the filling slurry in the high-salt old brine-tailings system.

[0007] The technical solution of this invention is implemented as follows: In a first aspect, the present invention provides a method for preparing a potash ore solid-liquid tailings-based filling material, comprising the following steps: S1, mix potassium phosphate with the tailings liquid, stir to dissolve, and obtain phosphate brine solution; S2, dry mix composition 1 and tailings salt in the composite binder to obtain a uniform dry material; then add the phosphate brine solution from step S1 and stir evenly to obtain a uniform slurry 1. S3, add a mineral carrier-loaded slow-release alkali source to the homogeneous slurry 1 from step S2, stir evenly, and obtain homogeneous slurry 2. S4. First, add polycarboxylate superplasticizer to the homogeneous slurry 2 from step S3, mix well, then add associative thickener solution, mix well, then add anionic polyacrylamide, mix well, and obtain filler.

[0008] Tailings salt can provide a skeleton for the filling slurry through crystallization. Magnesium ions in the chemical components of old brine can hydrate to produce magnesium oxychloride cement, which provides a cementing effect. Chloride ions can also promote the hydration reaction of calcium aluminate, enabling the filling body to gain early strength more quickly.

[0009] Magnesium oxide plays a major cementing role. MgO hydration reacts with MgCl2 in the old brine under certain conditions to form MOC (magnesium oxychloride cement), increasing the alkalinity of the system. It also reacts with potassium phosphate to form a magnesium potassium phosphate framework. The chemical reaction formula is as follows:

[0010] MgO + H₂O → Mg(OH)₂ 5MgO+MgCl2+13H2O→5Mg(OH)2·MgCl2·8H2O MgO+KH2PO4+5H2O→MgKPO4·6H2O.

[0011] CaO acts as an alkaline initiator; CaO hydrates to form Ca(OH)₂, increasing the alkalinity of the system and providing CaO for the formation of CSH. 2+ The chemical reaction formula is as follows:

[0012] CaO + H₂O → Ca(OH)₂ Ca(OH)2+SiO2(am)+(m-1)H2O→CaO·SiO2·mH2O.

[0013] However, when the CaO content is high, it will consume some H2PO4. - The formation of calcium phosphate precipitate is not conducive to the formation of magnesium potassium phosphate. Therefore, a slow-release alkali source is loaded onto a carrier to allow MgO to preferentially react with potassium phosphate to form a framework.

[0014] When potassium phosphate is added to the old brine, it rapidly releases phosphate ions. MgO hydration provides magnesium ions, which quickly generate potassium magnesium phosphate. Due to the high ion concentration in the slurry at this point, potassium magnesium phosphate rapidly precipitates in crystal form, causing the slurry to coagulate quickly and reducing its fluidity. Therefore, PCE (polycarboxylate superplasticizer) is introduced. By adsorbing onto the surface of MgO and potassium magnesium phosphate crystals, it slows down the rapid thickening of the slurry, thus balancing fluidity, reducing segregation, and minimizing the secretion of old brine. PAM (anionic polyacrylamide) adsorbs tailings particles and gelling agents through bridging flocculation, forming flocs and a network structure. This inhibits the sedimentation of tailings particles and gelling agents, reduces slurry segregation, and fixes free water in the material to reduce the secretion of old brine. However, when various materials are mixed into the slurry, the ion concentration in the system increases significantly, leading to excessive flocculation and excessively large flocs that encapsulate dry powder. Therefore, introducing PCE first can fully wet and disperse the fine cementitious powder, as well as the early-formed magnesium cement crystals and magnesium phosphate crystals in the slurry, resulting in smaller and more uniform flocs formed by PAM, reducing the problem of insufficient cementitious reaction caused by excessive flocculation. Therefore, PCE should be added before PAM.

[0015] Fly ash (FA) utilizes its spherical shape and fine particle size to lubricate the friction between tailings salt particles, improving fluidity. Furthermore, after CaO increases alkalinity, it forms CAH and CASH gels under high pH conditions, contributing to material strength. GGBS (blast furnace slag) incorporated into the MOC system can alter hydration products and pore structure. Under alkaline-activated conditions, it generates hydrotalcite-like substances that can bind with chloride ions, reducing the negative effects of chloride ions.

[0016] In the above technical solution, the tailings are tailings generated during the mining or beneficiation of potash mines, with a sodium chloride content of ≥95%, in granular form, with a relatively coarse particle size, and the content of particles with a particle size of less than 200 mesh (75μm) is 1.07%; the tailing liquid is liquid magnesium chloride tailing liquid generated during the mining or beneficiation of potash mines, with a magnesium chloride concentration of 20~35%, and the concentration is saturated.

[0017] Based on the above technical solutions, preferably, according to the mass percentage and 100%, the mass percentage of tailings salt: composite binder: polycarboxylate superplasticizer: anionic polyacrylamide: associative thickener is (48~60%): (12~20%): (0.006~0.12%): (0.0006~0.02%): (0.002~0.05%), with the balance made up to 100% by tailings liquid.

[0018] Based on the above technical solution, a further preferred embodiment is that the mass percentages of tailings salt: composite binder: polycarboxylate superplasticizer: anionic polyacrylamide: associative thickener are 54%: 16%: 0.06%: 0.006%: 0.01%, with the remainder made up to 100% by tailings liquid.

[0019] Associative thickeners are salt-resistant, hydrophobic associative thickeners used to form a weak network in a static state to inhibit sedimentation and segregation, and to decompose in a shear state to maintain pumpable flowability.

[0020] Based on the above technical solutions, preferably, in step S2, the components of composition 1 include magnesium oxide, blast furnace slag and fly ash.

[0021] In the above technical solution, the blast furnace slag contains 34.10% CaO, 34.10% SiO2, and 17.61% Al2O3; the fly ash is a grayish-black powder with a density of 2.10 g / cm³. 3 The loss on ignition was 2.62%, of which CaO content was 4.5%, SiO2 content was 45.1%, and Al2O3 content was 36.8%.

[0022] Based on the above technical solutions, preferably, the composite binder further includes a mineral carrier-loaded slow-release alkali source and potassium phosphate.

[0023] Based on the above technical solutions, preferably, the mass percentages of the potassium phosphate, blast furnace slag, fly ash and mineral carrier-loaded slow-release alkali source are (3~12%):(18~35%):(5~12%):(5~20%), with the remainder supplemented with magnesium oxide to make up to 100%.

[0024] Based on the above technical solution, a further preferred embodiment is that the mass percentages of the potassium phosphate, blast furnace slag, fly ash and mineral carrier-loaded slow-release alkali source are 8%:26%:6%:15%, with the balance being 45% magnesium oxide.

[0025] Based on the above technical solutions, preferably, in step S3, the mineral carrier-loaded slow-release alkali source is prepared using aluminosilicate mineral as the carrier and CaO as the alkali source. The aluminosilicate mineral is a fibrous / tubular / lamellar aluminosilicate mineral.

[0026] Based on the above technical solutions, preferably, the silica-alumina minerals include one or more of attapulgite, sepiolite, halloysite nanotubes, kaolinite, or metakaolinite.

[0027] Based on the above technical solutions, preferably, the mass ratio of the carrier to the alkali source is 1:0.2~2.

[0028] Based on the above technical solutions, a further preferred method is to use attapulgite as a carrier and CaO as an alkali source, with a mass ratio of attapulgite to CaO of 1:1, and prepare the solution through dry mixing or surface adsorption.

[0029] Based on the above technical solutions, preferably, in step S1, the potassium phosphate components include KH2PO4 and K2HPO4.

[0030] Based on the above technical solutions, preferably, the mass of KH2PO4 is 70-90% of the total mass of potassium phosphate; more preferably, the mass of KH2PO4 is 80% of the total mass of potassium phosphate.

[0031] Secondly, a potash mine solid-liquid tailings-based filling material is provided, which is prepared by the potash mine solid-liquid tailings-based filling material preparation method described above.

[0032] The potash ore solid-liquid tailings-based filling material of the present invention has the following advantages over the prior art: 1. This invention achieves a coordinated and sequential addition process of tailings salt, old brine, composite binder (MgO, slag, fly ash, carrier-loaded slow-release alkali source, potassium phosphate) and additives (PCE, PAM, associative thickener) in a high-salt complex system, thereby achieving a balance between slurry fluidity, anti-segregation, pumpability and filling strength. This provides an economical, environmentally friendly and efficient technical solution for filling goaf areas in potash mines.

[0033] 2. Using tailings (solid waste) and old brine (liquid waste) generated during the mining and beneficiation of potash ore as the main raw materials, the tailings provide skeletal strength through gradation and crystallization. Magnesium chloride and magnesium oxide in the old brine react to form magnesium oxychloride cement cementitious material, realizing the large-scale disposal of solid and liquid waste. The friction effect between tailings particles is lubricated by fly ash, which reduces the setting speed of magnesium cement and improves the fluidity of the slurry. Furthermore, under the action of alkali activation, blast furnace slag and fly ash can provide higher strength to the material in the later stage, making up for the disadvantage of magnesium cement absorbing moisture and reverting to brine in high humidity environments.

[0034] 3. The carrier-loaded slow-release alkali source reduces the risk of early rapid thickening and pipe blockage by controlling the release of alkalinity, while ensuring the mid-to-late stage alkali-activated reaction, thus improving the later strength and structural stability. The fibrous / tubular / lamellar silica-alumina mineral carrier has a fibrous / tubular / lamellar microstructure that can adsorb some of the free water in the slurry, thereby inhibiting the sedimentation and segregation of tailings particles and brine secretion; at the same time, its surface can provide heterogeneous nucleation sites, making the MgKPO4 distribution more uniform. The uniform and refined cementitious skeleton and the carrier's adsorption and water-locking effect work synergistically to help inhibit free water migration, thereby improving the slurry's stability against brine secretion and segregation, and may also reduce the later pore connectivity and improve the microstructure density.

[0035] 4. PAM inhibits the sedimentation of tailings particles and cementitious substances through bridging flocculation, reducing slurry segregation. It can also fix free water in the material to reduce the secretion of old brine. PCE fully wets and disperses the fine cementitious powder, early-formed magnesium cement crystals, and magnesium phosphate crystals in the slurry, making the PAM-formed flocs smaller and more uniform, reducing the problem of insufficient cementitious reaction caused by excessive flocculation. This can reduce the risk of pipe blockage and improve fluidity. At the same time, the fiber / tubular / lamellar silica-alumina mineral carrier can improve particle size distribution, which is more conducive to the PCE dispersion system and enhances the initial fluidity of the slurry. Moreover, the fiber / tubular / lamellar silica-alumina mineral carrier can also work synergistically with PAM to form a composite network that does not segregate or secrete brine. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a flowchart illustrating the preparation process of the potash ore solid-liquid tailings-based filling material according to the present invention. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] The tailings salt used in this invention is taken from a potash mine beneficiation plant. Its main component is sodium chloride (content ≥95%), with relatively coarse particles; particles smaller than 200 mesh account for 1.07%. Before use, it is dried, crushed, and sieved, with particles ≤1.25mm in diameter collected for later use. The old brine is also taken from a potash mine beneficiation plant; it is magnesium chloride tailings with a magnesium chloride concentration of 20-35%. Its chemical composition is analyzed before use. Magnesium oxide (MgO) was purchased from Tianjin Huasheng Chemical Reagent Co., Ltd. Blast furnace slag (GGBS) has the main chemical components of CaO 34.10%, SiO2 34.10%, and Al2O3 17.61%, and was purchased from Hebei Jingye Steel Co., Ltd. Fly ash (FA) is a grayish-black powder with a density of 2.10 g / cm³. 3The following materials were purchased from Shijiazhuang Shang'an Power Plant: Loss on ignition 2.62%, chemical composition CaO 4.5%, SiO2 45.1%, Al2O3 36.8%; attapulgite: fibrous aluminosilicate mineral, purchased from Henan Borun Foundry Materials Co., Ltd.; calcium oxide (CaO): purchased from Tianjin Juhengda Chemical Co., Ltd.; polycarboxylate superplasticizer (PCE): solid content 10.0%, water reduction rate 35.0%, purchased from Sichuan Dongrun Baisheng New Materials Co., Ltd.; anionic polyacrylamide (PAM): solid content 96.7%, purchased from Shanghai Yuqin Chemical Co., Ltd.; associative thickener: salt-resistant hydrophobic associative thickener, purchased from Anhui Xinfeng Chemical Co., Ltd.

[0040] Example 1 This embodiment provides a potash ore solid-liquid tailings-based backfill material for filling non-metallic mine goafs. The raw material composition, by mass percentage, is: tailings salt 48-60%, composite binder 16%, anionic polyacrylamide (PAM) 0.006%, polycarboxylate superplasticizer (PCE) 0.06%, associative thickener 0.01%, and the balance being old brine (i.e., old brine 22-38%). The composite binder consists of the following components by mass percentage: magnesium oxide 45%, blast furnace slag 26%, fly ash 6%, attapulgite-loaded slow-release alkali source 15%, and potassium phosphate 8%.

[0041] Taking a 1000g filler slurry as an example, slurries with solid concentrations (i.e., the percentage of total solid mass in the slurry) of 67%, 70%, and 73% were prepared, corresponding to tailings salt mass ratios of approximately 51%, 54%, and 58%, respectively. The specific feed amounts and preparation steps are as follows: 1. Preparation of carrier-loaded slow-release alkali source: Weigh 12g of attapulgite and 12g of CaO (mass ratio 1:1), place them in a mixer and dry mix for 10 minutes to make CaO uniformly loaded on the surface of attapulgite, and obtain 24g of attapulgite-loaded slow-release alkali source for later use.

[0042] 2. Preparation of admixture solution: PAM solution: Weigh 0.06g of PAM solid, add 59.94g of water, stir to dissolve, and prepare 60mL (about 60g) of PAM solution with a mass fraction of 0.1%.

[0043] Associative thickener solution: Weigh 0.1g of associative thickener solid, add 9.9g of water, stir to dissolve, and prepare 10mL (about 10g) of thickener solution with a mass fraction of 1%.

[0044] PCE solution: Take 6 mL (about 6 g) of polycarboxylate superplasticizer (containing 0.6 g of solid PCE and 5.4 g of water).

[0045] 3. Preparation of phosphate brine solution: According to the target solid concentration, weigh the corresponding mass of brine as shown in Table 1, add 12.8g of potassium phosphate, stir until completely dissolved, and obtain phosphate brine solution.

[0046] 4. Dry mixing: Weigh the following solid materials: 72g magnesium oxide, 41.6g blast furnace slag, 9.6g fly ash, and tailings salt: Weigh the corresponding mass of tailings salt as shown in Table 1, add the above materials together to the mixer, and dry mix for 2 minutes to obtain uniform dry material.

[0047] 5. Add the phosphate brine solution prepared in step 3 to the dry material and continue stirring for 5 minutes to obtain a homogeneous slurry. Weigh 24g of the attapulgite-loaded slow-release alkali source prepared in step 1 and add it to the above slurry, continuing to stir for 5 minutes to ensure thorough mixing and reaction. First, add 6g of the prepared PCE solution and stir for 30 seconds; then add 10g of the prepared associative thickener solution and stir for 30 seconds; finally, add 60g of the prepared PAM solution and stir for 30 seconds to obtain the final filling slurry.

[0048] Based on the above steps, by adjusting the amount of old brine and tail salt, filling slurries with solid concentrations of 67%, 70%, and 73% were prepared respectively. The specific amount of materials added and the performance test results are shown in Table 1.

[0049] Table 1. Raw material feed amount (total slurry mass 1000g) and performance at different solid concentrations

[0050] Example 2 This embodiment provides a potash ore solid-liquid tailings-based backfill material for filling non-metallic mine goafs. Its raw material composition, by mass percentage, is: tailings salt 48%~60%, composite binder 12%, anionic polyacrylamide (PAM) 0.0006%, polycarboxylate superplasticizer (PCE) 0.006%, associative thickener 0.002%, and the balance being old brine (i.e., old brine 28~40%). The composite binder consists of the following components by mass percentage: magnesium oxide 69%, blast furnace slag 18%, fly ash 5%, attapulgite-loaded slow-release alkali source 5%, and potassium phosphate 3%.

[0051] Taking a filling slurry with a total mass of 1000g as an example, slurries with solid concentrations (i.e., the percentage of total solid mass in the slurry) of 67%, 70%, and 73% were prepared respectively. The specific feed amounts and preparation steps are as follows: 1. Preparation of carrier-loaded slow-release alkali source: Weigh 5g of attapulgite and 1g of CaO (mass ratio 1:0.2), place them in a mixer and dry mix for 10 minutes to uniformly load CaO onto the surface of the attapulgite, and obtain 6g of attapulgite-loaded slow-release alkali source for later use.

[0052] 2. Preparation of admixture solution: PAM solution: Weigh 0.006g of PAM solid, add 5.994g of water, stir to dissolve, and prepare 6mL (about 6g) of PAM solution with a mass fraction of 0.1%.

[0053] Associative thickener solution: Weigh 0.02g of associative thickener solid, add 1.98g of water, stir to dissolve, and prepare 2mL (about 2g) of thickener solution with a mass fraction of 1%.

[0054] PCE solution: Take 0.6 mL (about 0.6 g) of polycarboxylate superplasticizer directly.

[0055] 3. Preparation of phosphate brine solution: According to the target solid concentration, weigh the corresponding mass of brine as shown in Table 2, add 3.6g of potassium phosphate, stir until completely dissolved, and obtain phosphate brine solution.

[0056] 4. Dry mixing: Weigh the following solid materials: 82.8g magnesium oxide, 21.6g blast furnace slag, 6g fly ash, and tailings salt: Weigh the corresponding mass of tailings salt as shown in Table 2, add the above materials together to the mixer, and dry mix for 2 minutes to obtain uniform dry material.

[0057] 5. Add the phosphate brine solution prepared in step 3 to the dry material and continue stirring for 5 minutes to obtain a homogeneous slurry. Weigh 6g of the attapulgite-loaded slow-release alkali source prepared in step 1 and add it to the above slurry, continuing to stir for 5 minutes to ensure thorough mixing and reaction. First, add 0.6g of the prepared PCE solution and stir for 30 seconds; then add 2g of the prepared associative thickener solution and stir for 30 seconds; finally, add 6g of the prepared PAM solution and stir for 30 seconds to obtain the final filling slurry.

[0058] Based on the above steps, by adjusting the amount of old brine and tail salt, filling slurries with solid concentrations of 67%, 70%, and 73% were prepared respectively. The specific amount of materials added and the performance test results are shown in Table 2.

[0059] Table 2. Raw material feed amount (total slurry mass 1000g) and performance at different solid concentrations

[0060] Example 3 This embodiment provides a potash ore solid-liquid tailings-based backfill material for filling non-metallic mine goafs. The raw material composition, by mass percentage, is: tailings salt 48%~60%, composite binder 20%, anionic polyacrylamide (PAM) 0.02%, polycarboxylate superplasticizer (PCE) 0.12%, associative thickener 0.05%, and the balance being old brine (i.e., old brine 28~40%). The composite binder consists of the following components by mass percentage: magnesium oxide 21%, blast furnace slag 35%, fly ash 12%, attapulgite-loaded slow-release alkali source 20%, and potassium phosphate 12%.

[0061] Taking a filling slurry with a total mass of 1000g as an example, slurries with solid concentrations (i.e., the percentage of total solid mass in the slurry) of 67%, 70%, and 73% were prepared respectively. The specific feed amounts and preparation steps are as follows: 1. Preparation of carrier-loaded slow-release alkali source: Weigh 13.3g of attapulgite and 26.7g of CaO (mass ratio 1:2), place them in a mixer and dry mix for 10 minutes to uniformly load CaO onto the surface of the attapulgite, and obtain 40g of attapulgite-loaded slow-release alkali source for later use.

[0062] 2. Preparation of admixture solution: PAM solution: Take 0.2 g of anionic polyacrylamide solid, add 19.8 g of water, and prepare 20 mL (about 20 g) of 1% solution.

[0063] Associative thickener solution: Take 0.5 g of associative thickener solid, add 9.5 g of water, and prepare 10 mL (about 10 g) of 5% solution.

[0064] PCE solution: Take 1.2 g of solid polycarboxylate superplasticizer, add 4.8 g of water, and prepare 6 mL (about 6 g) of 20% solution.

[0065] 3. Preparation of phosphate brine solution: According to the target solid concentration, weigh the corresponding mass of brine as shown in Table 3, add 24g of potassium phosphate, stir until completely dissolved, and obtain phosphate brine solution.

[0066] 4. Dry mixing: Weigh the following solid materials: 42g magnesium oxide, 70g blast furnace slag, 24g fly ash, and tailings salt: Weigh the corresponding mass of tailings salt as shown in Table 3, add the above materials together to the mixer, and dry mix for 2 minutes to obtain uniform dry material.

[0067] 5. Add the phosphate brine solution prepared in step 3 to the dry material and continue stirring for 5 minutes to obtain a homogeneous slurry. Weigh 40g of the attapulgite-loaded slow-release alkali source prepared in step 1 and add it to the above slurry, continuing to stir for 5 minutes to ensure thorough mixing and reaction. First, add 6g of the prepared PCE solution and stir for 60 seconds; then add 10g of the prepared associative thickener solution and stir for 60 seconds; finally, add 20g of the prepared PAM solution and stir for 60 seconds to obtain the final filling slurry.

[0068] Based on the above steps, by adjusting the amount of old brine and tail salt, filling slurries with solid concentrations of 67%, 70%, and 73% were prepared respectively. The specific amount of materials added and the performance test results are shown in Table 3.

[0069] Table 3. Raw material feed amount (total slurry mass 1000g) and performance at different solid concentrations

[0070] As shown in Tables 1-3, under the same solid concentration conditions, by adjusting the dosage of the composite binder and the carrier composition of the slow-release alkali source, potash ore solid-liquid tailings-based filling slurry with good fluidity can be obtained, and a certain 28-day compressive strength can be achieved. Compared with Examples 2 and 3, the 28-day compressive strength of Example 1 at 67%, 70%, and 73% solid concentrations reached 2.8–3.1 MPa, 3.3–3.7 MPa, and 3.7–4.2 MPa, respectively, which are significantly higher than those of Example 2 (1.5–1.8 MPa, 2.0–2.3 MPa, and 2.2–2.6 MPa) and Example 3 (1.3–1.6 MPa, 1.6–1.9 MPa, and 1.8–2.1 MPa). Meanwhile, the spread of Example 1 was 215–235 mm, 190–210 mm, and 175–195 mm, respectively, still within the pumpable range. This demonstrates that the formulation system used in this application can balance the fluidity of the slurry and the strength of the hardened body, with Example 1 exhibiting the best overall performance.

[0071] Example 4 This embodiment is basically the same as Embodiment 1, except that: in the composite binder, the mass ratio of attapulgite loaded with slow-release alkali source is 5%, that is, in the preparation of carrier loaded with slow-release alkali source in step 1: weigh 4g of attapulgite and 4g of CaO (mass ratio 1:1), put them in a mixer and dry mix for 10 minutes to make CaO uniformly loaded on the surface of attapulgite, and obtain 8g of attapulgite loaded with slow-release alkali source for later use.

[0072] Example 5 This embodiment is basically the same as Embodiment 1, except that: in the composite binder, the mass ratio of attapulgite loaded with slow-release alkali source is 20%, that is, in the preparation of carrier loaded with slow-release alkali source in step 1: weigh 16g of attapulgite and 16g of CaO (mass ratio 1:1), put them in a mixer and dry mix for 10 minutes to make CaO uniformly loaded on the surface of attapulgite, and obtain 32g of attapulgite loaded with slow-release alkali source for later use.

[0073] Comparative Example 1 This comparative example is basically the same as Example 1, except that: in the composite binder, the mass ratio of attapulgite loaded with slow-release alkali source is 4%, that is, in the preparation of carrier loaded with slow-release alkali source in step 1: weigh 3.2g of attapulgite and 3.2g of CaO (mass ratio 1:1), put them in a mixer and dry mix for 10 minutes to make CaO uniformly loaded on the surface of attapulgite, and obtain 6.4g of attapulgite loaded with slow-release alkali source for later use.

[0074] Comparative Example 2 This comparative example is basically the same as Example 1, except that: in the composite binder, the mass ratio of attapulgite loaded with slow-release alkali source is 22%, that is, in the preparation of carrier-loaded slow-release alkali source in step 1: weigh 17.6g of attapulgite and 17.6g of CaO (mass ratio 1:1), place them in a mixer and dry mix for 10 minutes to make CaO uniformly loaded on the surface of attapulgite, and obtain 35.2g of attapulgite loaded with slow-release alkali source for later use.

[0075] Comparative Example 3 This comparative example is basically the same as Example 1, except that in the composite binder, the alkali source is not loaded with a carrier, but 12g of CaO is added directly.

[0076] Comparative Example 4 This comparative example is basically the same as Example 1, except that PCE solution was not added in step 5.

[0077] Comparative Example 5 This comparative example is basically the same as Example 1, except that PAM solution was not added in step 5.

[0078] Comparative Example 6 This comparative example is basically the same as Example 1, except that in step 5, no associative thickener solution was added.

[0079] Comparative Example 7 This comparative example is basically the same as Example 1, except that in step 5, PAM solution is added first and then PCE solution is added.

[0080] Comparative Example 8 This comparative example is basically the same as Example 1, except that in step 5, PCE, associative thickener and PAM solution are added simultaneously.

[0081] Using Examples 4 and 5, and Comparative Examples 1 to 8, as an example of a total mass of 1000g of filling slurry, a slurry with a solid concentration (i.e., the total mass ratio of solids in the slurry) of 70% was prepared, that is, the tailings salt mass ratio should be about 54%. The remaining steps were the same as in Example 1, and the performance test results are shown in Table 4.

[0082] Table 4 Performance of Examples 4-5 and Comparative Examples 1-8 at 70% solid concentration

[0083] Table 4 shows that, under a solids concentration of 70%, the dosage of attapulgite-loaded slow-release alkali source in the composite binder has a significant impact on the performance of the filling slurry. When the dosage of attapulgite-loaded slow-release alkali source is reduced from 15% to 5% or 4% (Example 4, Comparative Example 1), the alkali activation effect of the system is insufficient, and the gelation reaction is incomplete, resulting in a significant decrease in the 28-day compressive strength, but a slight increase in spread. When the dosage is increased to 20% or 22% (Example 5, Comparative Example 2), the slurry viscosity increases, the fluidity decreases, and the strength improvement is not significant; the overall performance is still lower than that of Example 1. In addition, Comparative Examples 4-8 show that the admixture system and its addition order also have an important impact on the performance of the filling slurry. Without PCE (Comparative Example 4), the slurry dispersibility was insufficient, and the spread was significantly reduced. Without PAM (Comparative Example 5), the slurry cohesiveness and water retention were insufficient; although the spread increased, segregation was prone to occur, leading to a decrease in strength. Without the addition of the associative thickener (Comparative Example 6), the slurry stability deteriorated, manifested as a larger spread and a decrease in strength. Comparative Examples 7 and 8 further illustrate that changing the order of additive addition, especially adding PAM before PCE, or adding PCE, the associative thickener, and PAM simultaneously, is detrimental to the effective dispersion of particles in the slurry and the rational construction of the cohesive structure, resulting in slurry fluidity and hardened body strength inferior to Example 1. Therefore, in this application, the synergistic effect of PCE, the associative thickener, and PAM, and the addition order of PCE first, then the associative thickener, and finally PAM, resulted in the best overall performance of the filling slurry.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a potash ore solid-liquid tailings-based filling material, characterized in that, Includes the following steps: S1, mix potassium phosphate with the tailings liquid, stir to dissolve, and obtain phosphate brine solution; S2, dry mix composition 1 and tailings salt in the composite binder to obtain a uniform dry material; Add the phosphate brine solution from step S1, stir well, and obtain a uniform slurry 1; S3, add a mineral carrier-loaded slow-release alkali source to the homogeneous slurry 1 from step S2, stir evenly, and obtain homogeneous slurry 2. S4. First, add polycarboxylate superplasticizer to the homogeneous slurry 2 from step S3, mix well, then add associative thickener solution, mix well, then add anionic polyacrylamide, mix well, and obtain filler.

2. The method for preparing potash ore solid-liquid tailings filler as described in claim 1, characterized in that: Based on a total mass percentage of 100%, the mass percentages of the tailings salt, composite binder, polycarboxylate superplasticizer, anionic polyacrylamide, and associative thickener are (48~60%): (12~20%): (0.006~0.12%): (0.0006~0.02%): (0.002~0.05%), with the remainder made up to 100% by tailings liquid.

3. The method for preparing potash ore solid-liquid tailings filler as described in claim 1, characterized in that: In step S2, the components of composition 1 include magnesium oxide, blast furnace slag, and fly ash.

4. The method for preparing potash ore solid-liquid tailings filler as described in claim 3, characterized in that: The composite binder also includes a mineral carrier-loaded slow-release alkali source and potassium phosphate.

5. The method for preparing potash ore solid-liquid tailings filler as described in claim 4, characterized in that: Based on a total mass percentage of 100%, the mass percentages of the potassium phosphate, blast furnace slag, fly ash and mineral carrier-loaded slow-release alkali source are (3~12%):(18~35%):(5~12%):(5~20%), with the remainder made up to 100% with magnesium oxide.

6. The method for preparing potash ore solid-liquid tailings-based filling material as described in claim 1, characterized in that: In step S3, the mineral carrier loaded with slow-release alkali source is prepared using silica-alumina mineral as the carrier and CaO as the alkali source.

7. The method for preparing potash ore solid-liquid tailings filler as described in claim 6, characterized in that: The silica-alumina minerals include one or more of attapulgite, sepiolite, halloysite nanotubes, kaolinite, or metakaolinite.

8. The method for preparing potash ore solid-liquid tailings filler as described in claim 7, characterized in that: The mass ratio of the carrier to the alkali source is 1:0.2~2.

9. The method for preparing potash ore solid-liquid tailings-based filling material as described in claim 1, characterized in that: In step S1, the potassium phosphate comprises KH2PO4 and K2HPO4; the mass of KH2PO4 is 70-90% of the total mass of the potassium phosphate.

10. A potash ore solid-liquid tailings-based filling material, characterized in that: It is prepared by the method for preparing potash ore solid-liquid tailings filler according to any one of claims 1 to 9.

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