Full resource cementation filling process of old brine and tailing salt in potash mine based on magnesium-calcium synergistic transformation

Abstract

The present application provides a full resource cementation filling process for old brine-tail salt of potash mine based on the synergistic conversion of magnesium and calcium, which belongs to the field of filling of goaf of potash mine, wherein CaO is added to the old brine to react to obtain a mixed precipitate of Mg(OH)2 / Ca(OH)2, and then a dispersant is added, and solid-liquid separation is performed to obtain a solid mixture and a mother liquor after reaction; the tail salt is divided into coarse tail salt with a particle size of >75μm and fine tail salt with a particle size of ≤75μm according to the particle size, and the coarse tail salt is mechanically ground to a particle size of <50μm to obtain activated coarse tail salt; the fine tail salt is mixed with an activator and activated by ball milling to obtain activated fine tail salt; the activated coarse tail salt, the activated fine tail salt, the solid mixture and the mother liquor after reaction are mixed, and a retarder and a water reducer are added to stir to obtain a filling slurry, and the filling slurry is pumped underground for filling in multiple layers. The present application provides a full resource cementation filling process for old brine-tail salt of potash mine based on the synergistic conversion of magnesium and calcium, and belongs to the field of filling of goaf of potash mine, wherein CaO is added to the old brine to react to obtain a mixed precipitate of Mg(OH)2 / Ca(OH)2, and then a dispersant is added, and solid-liquid separation is performed to obtain a solid mixture and a mother liquor after reaction; the tail salt is divided into coarse tail salt with a particle size of >75μm and fine tail salt with a particle size of ≤75μm according to the particle size, and the coarse tail salt is mechanically ground to a particle size of <50μm to obtain activated coarse tail salt; the fine tail salt is mixed with an activator and activated by ball milling to obtain activated fine tail salt; the activated coarse tail salt, the activated fine tail salt, the solid mixture and the mother liquor after reaction 2+ The Mg(OH)2 / Ca(OH)2 gel phase is generated and combined with the tail salt graded activation technology to form a low-cost, high-strength filling system.

Description

Technical Field

[0001] The present invention relates to the technical field of filling goaf of potash mines, and in particular to a full-resource cementation filling process of old brine and tailing salt of potash mines based on the synergistic conversion of magnesium and calcium. Background Art

[0002] Potash ore, primarily consisting of potash and carnallite, is an important source of raw material for potash fertilizers. The mass fraction of potassium chloride in potash ore is typically 25% to 35%, while that in carnallite is 15% to 22%. During the beneficiation process of potash ore, tailings and brine are produced. Tailings are primarily granular sodium chloride crystals, while brine contains a high MgCl₂ content. If not effectively treated, these tailings and brine can cause serious environmental pollution. Furthermore, if mined-out areas in potash mines are not backfilled, they can lead to surface subsidence, posing a potential safety hazard. To prevent surface subsidence and maintain ecological balance, the backfill mining method is used. By backfilling the mined-out areas with tailings and brine, the pressure on the surface environment can be effectively reduced, preventing subsidence.

[0003] At present, the treatment technologies for potash mine tailings mainly include dry filling, wet "water-sand" filling and cementing filling. However, the traditional filling method using silicate cement as a binder has not been widely used due to problems such as poor bonding effect, poor salt corrosion resistance and high cost. Although magnesium cement as a binder has solved the problem of filling material strength to a certain extent, its filling slurry has poor fluidity and fast water exudation, which makes transportation difficult and easily causes pipeline blockage, increasing the difficulty of management. Using MgO powder as a cementing material and adding a retarder prolongs the initial setting time, it greatly increases the cost of filling. Tailings are only used as aggregates, and their potential cementing activity is not fully activated; Mg in the old brine 2+ Failure to effectively recycle the waste leads to resource waste. Therefore, the field of potash mine filling still faces many key technical challenges, especially in the effective treatment of tailing salts (such as NaCl and KCl) and high-concentration magnesium chloride brine (MgCl2 concentration of about 30%).

[0004] In view of this, it is necessary to design an improved cementation filling process for potash mine brine-tailing salt based on the synergistic conversion of magnesium and calcium to solve the above problems. Summary of the Invention

[0005] In view of the technical problems existing in the background technology, the present application provides a full resource-based cementation and filling process for old brine and tailing salt of potash mines based on the synergistic conversion of magnesium and calcium, aiming to solve the technical problems of the existing technology such as high cementation cost, insufficient filling strength, complex process, low resource utilization and poor slurry performance.

[0006] The present application provides a full resource-based cementation filling process for potash mine brine-tail salt based on magnesium-calcium synergistic conversion, comprising the following steps:

[0007] S1. CaO is added to the old brine to react to obtain a Mg(OH)2 / Ca(OH)2 mixed precipitate, followed by addition of a dispersant and solid-liquid separation to obtain a solid mixture and a mother liquor after the reaction;

[0008] S2. The tail salt is divided into coarse tail salt with a particle size of> 75μm and fine tail salt with a particle size of ≤75μm by particle size, and the coarse tail salt is mechanically ground to a particle size of <50μm to obtain an activated coarse tail salt; the fine tail salt is mixed with an activator and activated by ball milling to obtain an activated fine tail salt;

[0009] S3. The activated coarse tail salt, the activated fine tail salt, the solid mixture, and the mother liquor after the reaction are mixed, and a retarder and a water reducer are added and stirred to obtain a filling slurry; the mass ratio of the activated coarse tail salt, the activated fine tail salt, the solid mixture, and the mother liquor after the reaction is 40~50%:20~30%:15~20%:10~15%;

[0010] S4. Pump the filling slurry into the well and fill it in multiple layers.

[0011] As a further improvement of the present application, in step S1, the molar ratio of the CaO to the MgCl2 in the old brine is (1.0~1.1):1; the reaction temperature is 60~80°C, and the reaction time is 1~3h; the particle size of the Mg(OH)2 / Ca(OH)2 mixed precipitate is 20~50μm.

[0012] As a further improvement of the present application, the dispersant is sodium hexametaphosphate, and the added amount is 0.05~0.2% of the mass of the old brine.

[0013] As a further improvement of the present application, the water content of the solid mixture is less than 30%.

[0014] As a further improvement of the present application, in step S2, the stimulant is sodium sulfate, and the added amount is 3-6% of the mass of the fine tail salt.

[0015] As a further improvement of the present application, the ball milling activation time is 20 to 40 minutes.

[0016] As a further improvement of the present application, the retarder is a mixture of boric acid and sodium gluconate, and the total amount added is 0.3~0.5% of the total mass of the filling slurry; the mass ratio of the boric acid to the sodium gluconate is 3:1; the water reducer is a polycarboxylic acid-based water reducer, and the amount added is 0.4~0.6% of the total mass of the filling slurry.

[0017] As a further improvement of the present application, the slump of the filling slurry is ≥18 cm, the initial setting time is 2 to 3 hours, and the final setting time is 6 to 8 hours.

[0018] As a further improvement of the present application, in step S4, the filling method is to fill in two layers, with the bottom layer activated coarse tail salt accounting for 50% and the surface layer activated fine tail salt accounting for 30%.

[0019] The beneficial effects of this application are:

[0020] The present application provides a full resource cementation filling process for potash mine brine-tail salt based on the synergistic conversion of magnesium and calcium. CaO is added to the old brine to react to obtain a Mg(OH)2 / Ca(OH)2 mixed precipitate, and then a dispersant is added. After solid-liquid separation, a solid mixture and a mother liquor after reaction are obtained; the tail salt is divided into coarse tail salt with a particle size of >75μm and fine tail salt with a particle size of ≤75μm according to the particle size, and the coarse tail salt is mechanically ground to a particle size of <50μm to obtain activated coarse tail salt; the fine tail salt is mixed with an activator and activated by ball milling to obtain activated fine tail salt; the activated coarse tail salt, activated fine tail salt, solid mixture and mother liquor after reaction are mixed, and a retarder and a water reducer are added to stir to obtain a filling slurry, which is pumped underground for filling. The present application provides a full resource cementation filling process for potash mine brine-tail salt based on the synergistic conversion of magnesium and calcium. The process comprises the following steps: 2+ The Mg(OH)2 / Ca(OH)2 gel phase is generated, and combined with tail salt graded activation technology, a low-cost, high-strength filling system is formed. This application achieves a tail salt utilization rate of ≥90%, 100% absorption of old brine, and a filling body strength of ≥4MPa after 28 days, reducing overall costs by 45%.

[0021] This application adopts graded activation of tail salt, and releases the potential gelling activity of tail salt through dual treatment of mechanical grinding and chemical excitation; through the synergistic conversion of magnesium and calcium, calcium oxide directionally converts Mg in old brine 2+ , generating a highly active Mg(OH)2 / Ca(OH)2 gelled phase, achieving full resource utilization, and increasing the tail salt utilization rate to more than 90%.

[0022] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] To more clearly illustrate the technical solution of this application, the following is a brief introduction to the drawings used in this application. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0024] Figure 1 This application provides a process flow chart for the full resource-based cementation filling of old brine and tailing salt from potash mines based on the synergistic conversion of magnesium and calcium. DETAILED DESCRIPTION

[0025] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0027] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0028] The existing potash ore treatment methods have significant defects in the following aspects: When traditional magnesium-based cement is used as a binder, the shrinkage rate of the filling body is high and the long-term strength is significantly affected by humidity and water seepage, with the strength decay rate exceeding 30% after 28 days. In addition, due to the inability to completely absorb the Mg in the old brine, the Mg content in the old brine is greatly reduced. 2+ The slurry is prone to premature coagulation (initial coagulation time < 1h), resulting in a pipe blockage rate of over 15% during transportation. This situation requires frequent pipe cleaning, increasing operational difficulty and maintenance costs. Tailing salt is usually used only as aggregate, failing to fully tap its potential for gelling activity. At the same time, the Mg in the old brine 2+ The tail salt crystallization filling process mainly focuses on the treatment of tail salt, but it cannot effectively solve the problem of the disposal of old brine, especially in the recovery of valuable elements in the old brine (such as Mg 2+) are deficient. Traditional cementitious materials have poor applicability. For example, ordinary Portland cement, while widely used in many traditional construction applications, suffers from poor compatibility with potash mine backfill, particularly with brine. Furthermore, the high cost of traditional cementitious materials further limits their application in potash mine tailings backfill.

[0029] In order to solve the above technical problems, the present application provides a full resource cementation filling process of potash mine brine-tail salt based on magnesium-calcium synergistic conversion, wherein the Mg in the brine is converted into 2+ The Mg(OH)2 / Ca(OH)2 gel phase is generated and combined with the tail salt graded activation technology to form a low-cost, high-strength filling system.

[0030] Please refer to Figure 1 The present invention provides a method for cementing and filling potash mine brine and tailing salt based on magnesium-calcium synergistic conversion, which includes the following steps:

[0031] S1. CaO is added to the old brine to react to obtain a Mg(OH)2 / Ca(OH)2 mixed precipitate, followed by addition of a dispersant and solid-liquid separation to obtain a solid mixture and a mother liquor after the reaction;

[0032] S2. The tail salt is divided into coarse tail salt with a particle size of >75μm and fine tail salt with a particle size of ≤75μm by particle size, and the coarse tail salt is mechanically ground to a particle size of <50μm to obtain an activated coarse tail salt; the fine tail salt is mixed with an activator and activated by ball milling to obtain an activated fine tail salt;

[0033] S3. The activated coarse tail salt, activated fine tail salt, solid mixture, the reaction mixture, the mother liquor was mixed, a retarder and a water reducer were added and stirred to obtain a filling slurry;

[0034] S4. Pump the filling slurry into the well and fill it in multiple layers.

[0035] This application uses calcium oxide to convert Mg in old brine 2+, generating a highly active Mg(OH)2 / Ca(OH)2 gel phase, thus realizing resource utilization of wastewater. Simultaneously, tailing salts are activated to improve their utilization rate. Mechanically grinding the coarse tailing salts to a particle size of <50μm increases their specific surface area, helping to increase the speed and extent of chemical reactions between the tailing salts and other materials, thereby enhancing the strength of the filling. Ball milling the fine tailing salts with an activator activates the potential active components within the fine tailing salts, thereby enhancing the gelling properties and durability of the filling. The addition of retarders and water reducers improves the fluidity and stability of the filling slurry, ensuring the compactness and strength of the underground filling and enhancing mine safety. This process effectively reduces environmental pollution from wastewater and tailing salts generated during potash mining, contributing to ecological protection. By utilizing waste from potash mining, it reduces dependence on external raw materials and reduces production costs. This process is simple to operate and can be easily implemented on existing mine production lines. It is suitable for the treatment of brine-tailing salts in various potash mines and has great potential for widespread application.

[0036] Furthermore, in some embodiments, in step S1, the molar ratio of CaO to MgCl2 in the old brine is (1.0~1.1):1; the reaction temperature is 60~80°C, and the reaction time is 1~3h; the particle size of the Mg(OH)2 / Ca(OH)2 mixed precipitate is 20~50μm.

[0037] In the technical solution of the embodiment of the present application, controlling the molar ratio of CaO to MgCl2 in the old brine within an appropriate range can ensure that the magnesium ions in MgCl2 can fully react with CaO to form a mixed precipitate of Mg(OH)2 / Ca(OH)2, while avoiding excessive use of CaO, reducing costs, and preventing the generation of excessive Ca(OH)2 from affecting the efficiency and quality of subsequent processes. Specifically, the molar ratio of CaO to MgCl2 in the old brine can be 1:1, 1.05:1, 1.1:1, or any value within the range of (1.0-1.1):1.

[0038] The reaction temperature is controlled at 60~80℃, which is conducive to increasing the reaction rate and ensuring the full progress of the reaction. Too low a temperature may lead to a slow reaction rate, while too high a temperature may cause unnecessary side reactions or affect the stability of the precipitate. The reaction time is controlled at 1~3h to ensure the full progress of the reaction and avoid the reduction in production efficiency caused by too long a time. The appropriate reaction time helps to form a mixed precipitate with uniform particle size and good stability. The particle size of the Mg(OH)2 / Ca(OH)2 mixed precipitate is controlled at 20~50μm, which is beneficial to the subsequent solid-liquid separation process, can improve the separation efficiency, and at the same time ensure the activity of the precipitate, which is conducive to its application in subsequent processes.

[0039] Furthermore, in some embodiments, the dispersant is sodium hexametaphosphate, and the added amount is 0.05-0.2% of the mass of the old brine.

[0040] In the technical solution of the embodiments of the present application, sodium hexametaphosphate can effectively reduce the surface tension of the solution, prevent agglomeration of solid particles, and thus improve the dispersibility of the mixed precipitate. The addition of sodium hexametaphosphate is controlled at 0.05-0.2% of the mass of the old brine to ensure sufficient dispersion while avoiding excessive use, reducing costs and possible environmental impacts. The appropriate amount of dispersant can optimize the efficiency of solid-liquid separation and improve the purity and quality of the solid product.

[0041] Furthermore, in some embodiments, the water content of the solid mixture is less than 30%.

[0042] In the technical solution of the embodiment of the present application, a plate and frame filter press is used for solid-liquid separation and dehydration to a solid mixture moisture content of <30%, which is conducive to better control of the rheology and coagulation time of the slurry when preparing the filling slurry, thereby improving the strength and stability of the filling body.

[0043] Furthermore, in some embodiments, in step S2, the stimulator is sodium sulfate, and the added amount is 3-6% of the mass of the fine tail salt.

[0044] In the technical solution of the present embodiment, the stimulator can enhance the activity of the fine-tail salt, promoting its reactivity in subsequent processes, thereby improving the setting, hardening, and mechanical properties of the filling slurry. Controlling the addition of sodium sulfate to 3-6% of the mass of the fine-tail salt ensures the stimulating effect while avoiding the increased costs or adverse reactions caused by excessive use.

[0045] Furthermore, in some embodiments, the ball milling activation time is 20 to 40 minutes.

[0046] In the technical solution of the present embodiment, the ball milling time ensures that the fine-tail salt and the activator are fully mixed and reacted, thereby activating the potential activity of the fine-tail salt and improving its reactivity in the filling slurry. Furthermore, an appropriate ball milling time helps improve the particle size distribution of the fine-tail salt, making the particles smaller and more uniform, which is beneficial for improving the fluidity of the filling slurry and the density of the final filling.

[0047] Furthermore, in some embodiments, in step S3, the mass ratio of the activated coarse tail salt, the activated fine tail salt, the solid mixture, and the mother liquor after the reaction is 40~50%:20~30%:15~20%:10~15%.

[0048] In the technical solution of the embodiment of the present application, by precisely controlling the mass ratio of each component, it is possible to ensure that the filling slurry has optimal fluidity and stability, as well as the strength and durability of the final filling body. The ratio of activated coarse tail salt to activated fine tail salt helps to improve the overall strength of the filling body, forming a more solid structure. The addition of the solid mixture and the mother liquor after the reaction allows the original waste to be effectively utilized, reducing environmental pollution and lowering production costs. Reasonable ratios can ensure that the filling slurry has good working performance during the pumping and filling process, reducing problems such as pipe blockage and uneven filling.

[0049] Furthermore, in some embodiments, the retarder is a mixture of boric acid and sodium gluconate, and the total amount added is 0.3-0.5% of the total mass of the filling slurry; the mass ratio of boric acid to sodium gluconate is 3:1; the water reducer is a polycarboxylic acid-based water reducer, and the amount added is 0.4-0.6% of the total mass of the filling slurry.

[0050] In the technical solution of the embodiments of this application, the mixture of boric acid and sodium gluconate can effectively prolong the setting time of the filling slurry, maintaining good fluidity during pumping and filling, facilitating operation. By adjusting the ratio of boric acid to sodium gluconate, the setting time of the filling slurry can be precisely controlled to meet the construction requirements under different working conditions. Polycarboxylate-based water reducers can significantly improve the fluidity of the filling slurry, reduce water consumption, and thus improve the strength and durability of the filling.

[0051] Furthermore, in some embodiments, the slump of the filling slurry is ≥18 cm, the initial setting time is 2-3 hours, and the final setting time is 6-8 hours.

[0052] In the technical solution of the embodiment of the present application, the slurry has good fluidity, which helps the slurry to be pumped smoothly through the pipeline during the filling process and can be well filled into the voids and cracks in the mine, improving the filling efficiency and quality. By adding a retarder to extend the setting time, the slurry has sufficient time to be handled after pumping and filling, but can also begin to solidify quickly to support the early stability of the ore body. The final setting time of 6-8 hours indicates that the slurry can fully harden within a reasonable time after filling, thereby providing sufficient support and ensuring the long-term stability of the mine.

[0053] Furthermore, in some embodiments, in step S4, the filling method is two-layer filling, with the bottom layer activated coarse tail salt accounting for 50% and the surface layer activated fine tail salt accounting for 30%.

[0054] In the technical solution of the embodiment of the present application, the bottom filling uses a slurry with a high proportion of coarse tailings to provide a good skeleton effect, enhance the overall compressive strength of the filling body, make the 28-day compressive strength ≥4MPa, and maintain the stability of the mine. In addition, the use of coarse tailings helps to quickly fill large volumes and improve construction efficiency. The use of slurry with a high proportion of fine tailings for surface filling can better fill the gaps between the coarse tailings, improve the density of the filling body, optimize the impermeability, and make the permeability coefficient ≤1×10 -6 cm / s, reducing water penetration and protecting the internal environment of the mine. Through this layered filling process, the structural stability can be increased, the high-strength slurry of the bottom layer provides solid support, and the low-permeability slurry of the surface layer reduces the risk of water damage, effectively utilizes coarse tailings and fine tailings, realizes the resource utilization of tailings, and at the same time reduces the discharge of mine waste and promotes the construction of green mines. By optimizing the slurry ratio and construction process, the filling cost is reduced and the economic benefit is improved. According to different construction environments and needs, the filling method can be carried out in multiple layers as long as the expected filling effect can be achieved, which all falls within the scope of protection of this application.

[0055] Some specific examples are listed below. It should be noted that the examples described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

[0056] Example 1

[0057] This embodiment provides a full resource-based cementation filling process for potash mine brine and tailing salt based on magnesium-calcium synergistic conversion, comprising the following steps:

[0058] S1. CaO was added to the old brine at a CaO:MgCl2 molar ratio of 1.05:1, and the mixture was reacted at 70°C for 2 h to obtain a Mg(OH)2 / Ca(OH)2 mixed precipitate with a magnesium-calcium conversion rate of 98.7%. Subsequently, 0.1% sodium hexametaphosphate dispersant was added to inhibit particle agglomeration. The particles were dehydrated using a plate and frame filter press at a pressure of 0.85 MPa to a moisture content of <30%, obtaining a solid mixture and a reaction mother liquor.

[0059] S2. The tail salt was divided into coarse tail salt with a particle size of >75μm and fine tail salt with a particle size of ≤75μm according to the particle size. The coarse tail salt was mechanically ground to a particle size of <50μm to increase the specific surface area to obtain activated coarse tail salt; the fine tail salt was mixed with 5% sodium sulfate and activated by ball milling for 35min to obtain activated fine tail salt;

[0060] S3. The activated coarse tail salt, activated fine tail salt, solid mixture, the reaction mother liquor was mixed in proportion, adding retarder and water reducer, using a dedicated mixer for stirring to obtain a filling slurry;

[0061] S4. The filling slurry is pumped into the well and filled in two layers. The composition and ratio of the bottom filling slurry are: 50% activated coarse tail salt, 20% activated fine tail salt, 15% solid mixture, 14.1% mother liquor after reaction, 0.3% boric acid and 0.1% sodium gluconate and 0.5% polycarboxylic acid water reducer; the composition and ratio of the surface filling slurry are: 40% activated coarse tail salt, 30% activated fine tail salt, 15% solid mixture, 14.1% mother liquor after reaction, 0.3% boric acid and 0.1% sodium gluconate and 0.5% polycarboxylic acid water reducer.

[0062] Example 2

[0063] Example 2 provides a full-resource cementation filling process for old brine and tailing salt of potash mine based on the synergistic conversion of magnesium and calcium. Compared with Example 1, the only difference is that the composition and proportion of the filling slurry are different. The bottom layer is: 50% activated coarse tailing salt, 22% activated fine tailing salt, 17% solid mixture, 10.1% mother liquor after reaction, 0.3% boric acid and 0.1% sodium gluconate and 0.5% polycarboxylic acid water reducer; the surface layer is: 42% activated coarse tailing salt, 30% activated fine tailing salt, 17% solid mixture, 10.1% mother liquor after reaction, 0.3% boric acid and 0.1% sodium gluconate and 0.5% polycarboxylic acid water reducer. The other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0064] Example 3

[0065] Example 3 provides a full resource-based cementation filling process for old brine and tailing salt of potash mines based on the synergistic conversion of magnesium and calcium. Compared with Example 1, the only difference is that the molar ratio of CaO to MgCl2 is 1.1:1. The other experimental parameters and conditions are basically the same as those in Example 1 and will not be repeated here.

[0066] Comparative Example 1

[0067] Comparative Example 1 provides a full resource-based cementation filling process for old brine and tailing salt of potash mines based on the synergistic conversion of magnesium and calcium. Compared with Example 1, the only difference is that in step S2, neither the coarse tailing salt nor the fine tailing salt is activated. The other experimental parameters and conditions are basically the same as those in Example 1 and will not be repeated here.

[0068] Comparative Example 2

[0069] Comparative Example 2 provides a full-resource cementation filling process for old brine and tailing salt of potash mine based on the synergistic conversion of magnesium and calcium. Compared with Example 1, the only difference is that the composition and proportion of the filling slurry are different. The bottom layer is: 35% activated coarse tailing salt, 35% activated fine tailing salt, 15% solid mixture, 14.1% mother liquor after reaction, 0.3% boric acid and 0.1% sodium gluconate and 0.5% polycarboxylic acid water reducer; the surface layer is: 55% activated coarse tailing salt, 15% activated fine tailing salt, 15% solid mixture, 14.1% mother liquor after reaction, 0.3% boric acid and 0.1% sodium gluconate and 0.5% polycarboxylic acid water reducer. The other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0070] Comparative Example 3

[0071] Comparative Example 3 provides a full resource-based cementation filling process for potash mine brine-tail salt based on magnesium-calcium synergistic conversion, which is processed using a traditional process and includes the following steps:

[0072] S1. Raw material pretreatment: Mix potash ore brine and tailings at a mass ratio of 1:1.2, remove impurities and adjust the moisture content to 20%;

[0073] S2. Addition of cementitious materials: Add magnesium-calcium composite cementitious agent, controlling the addition amount to 10% of the total mass;

[0074] S3 stirring and homogenizing: using a biaxial forced mixer to mix the raw materials at a speed of 30r / min for 20min;

[0075] S4. Molding and curing: The mixed slurry is injected into the mold and allowed to set at room temperature for initial setting. It is then steam cured (60-80°C, humidity ≥90%) until final setting.

[0076] S5. Performance test: Test compressive strength, shrinkage rate, permeability coefficient and other indicators according to standard methods.

[0077] The specific test results are shown in Table 1:

[0078]

[0079] As can be seen from Table 1, the filling process provided by this application can achieve a filling body strength of ≥4 MPa at 28 days, a shrinkage rate of <1.0%, an initial setting time of ≥2.5 h, a slurry slump of ≥18 cm, and a permeability coefficient of ≤1×10 -6 cm / s. The strength decay rate of the filling material used in this application is relatively low, only 8.5% (28 days), demonstrating high durability and stability. In comparison, the strength decay rate of the filling material using the traditional method is 32.0% (28 days), indicating that the performance of the filling material using the traditional method is inferior.

[0080] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A full resource cementation filling process for potash mine brine-tail salt based on magnesium-calcium synergistic conversion, characterized in that: The following steps are involved: S1. CaO is added to the old brine to react to obtain a Mg(OH)2 / Ca(OH)2 mixed precipitate, followed by addition of a dispersant and solid-liquid separation to obtain a solid mixture and a mother liquor after the reaction; S2. The tail salt is divided into coarse tail salt with a particle size of> 75μm and fine tail salt with a particle size of ≤75μm according to particle size, and the coarse tail salt is mechanically ground to a particle size of <50μm to obtain activated coarse tail salt; The fine-tailed salt is mixed with an activator and activated by ball milling to obtain an activated fine-tailed salt; S3. The activated coarse tail salt, the activated fine tail salt, the solid mixture, and the mother liquor after the reaction are mixed, and a retarder and a water reducer are added and stirred to obtain a filling slurry; the mass ratio of the activated coarse tail salt, the activated fine tail salt, the solid mixture, and the mother liquor after the reaction is 40~50%:20~30%:15~20%:10~15%; S4. Pump the filling slurry into the well and fill it in multiple layers.

2. The process for fully resource-based cementation and filling of potash ore brine and tailing salt based on magnesium-calcium synergistic conversion according to claim 1, characterized in that: In step S1, the molar ratio of the CaO to the MgCl2 in the old brine is (1.0~1.1):1; the reaction temperature is 60~80°C, and the reaction time is 1~3h; the particle size of the Mg(OH)2 / Ca(OH)2 mixed precipitate is 20~50μm.

3. The process for fully resource-based cementation and filling of potash ore brine and tailing salt based on magnesium-calcium synergistic conversion according to claim 2, characterized in that: The dispersant is sodium hexametaphosphate, and the addition amount is 0.05-0.2% of the mass of the old brine.

4. The process for cementing and filling potash ore brine and tailing salt based on magnesium-calcium synergistic conversion according to claim 3 is characterized in that: The water content of the solid mixture is less than 30%.

5. The process for cementing and filling potash ore brine and tailing salt based on magnesium-calcium synergistic conversion according to claim 1 is characterized in that: In step S2, the stimulant is sodium sulfate, and the added amount is 3-6% of the mass of the fine tail salt.

6. The process for cementing and filling potash ore brine and tailing salt based on magnesium-calcium synergistic conversion according to claim 5 is characterized in that: The ball milling activation time is 20 to 40 minutes.

7. The process for cementing and filling potash ore brine and tailing salt based on magnesium-calcium synergistic conversion according to claim 1 is characterized in that: In step S3, the retarder is a mixture of boric acid and sodium gluconate, and the total amount added is 0.3-0.5% of the total mass of the filling slurry; the mass ratio of the boric acid to the sodium gluconate is 3:1; the water reducer is a polycarboxylic acid-based water reducer, and the amount added is 0.4-0.6% of the total mass of the filling slurry.

8. The process for cementing and filling potash ore brine and tailing salt based on magnesium-calcium synergistic conversion according to claim 7 is characterized in that: The slump of the filling slurry is ≥18cm, the initial setting time is 2~3h, and the final setting time is 6~8h.

9. The process for cementing and filling potash ore brine and tailing salt based on magnesium-calcium synergistic conversion according to claim 1 is characterized in that: In step S4, the filling method is to fill in two layers, with the activated coarse tail salt in the bottom layer accounting for 50% and the activated fine tail salt in the surface layer accounting for 30%.

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