Potassium salt ore old brine-tail salt full-recycling cemented filling process based on magnesium-calcium synergistic conversion

Abstract

The invention provides a potassic salt ore old brine-tail salt full-recycling cemented filling process based on magnesium-calcium synergistic conversion, and belongs to the field of potassic salt ore goaf filling, CaO is added into old brine for reaction to obtain Mg (OH) 2 / Ca (OH) 2 mixed precipitate, then a dispersing agent is added, and solid-liquid separation is performed to obtain a solid mixture and a post-reaction mother solution; dividing the tail salt into particle sizes gt according to particle sizes; the method comprises the following steps: mechanically grinding coarse tail salt with the particle size of 75 microns and fine tail salt with the particle size of less than or equal to 75 microns until the particle size lt is reached; filtering to obtain activated crude tail salt; mixing the fine tail salt with an exciting agent, and activating through ball milling to obtain activated fine tail salt; and mixing the activated crude tail salt, the activated fine tail salt, the solid mixture and the reacted mother liquor, adding a retarder and a water reducing agent, stirring to obtain filling slurry, and pumping the filling slurry into a well for filling in multiple layers. According to the method, Mg < 2 + > in old brine is directionally converted through calcium oxide to generate a Mg (OH) 2 / Ca (OH) 2 gelling phase, and a low-cost and high-strength filling system is formed by combining a tail salt grading activation technology.

Description

Technical Field

[0001] The 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 magnesium-calcium synergistic conversion. Background Art

[0002] Potash mines are an important source of potash fertilizer raw materials, mainly including potash salt mines and carnallite mines. The mass fraction of potassium chloride in potash salt mines is usually 25%~35%, while the mass fraction of potassium chloride in carnallite mines is 15%~22%. In the beneficiation process of potash mines, tailing salts and old brine will be produced, among which the tailing salts are mainly granular sodium chloride crystals, and the content of MgCl2 in the old brine is relatively high. If the tailing salts and old brine are not effectively treated, they will cause serious pollution to the environment. In addition, if the goaf of potash mines is not backfilled, it may cause surface collapse, which will cause safety hazards. In order to prevent surface collapse and maintain ecological balance, the backfill mining method is applied. By filling the tailing salts and old brine into the goaf, the pressure on the surface environment can be effectively reduced and surface subsidence can be prevented.

[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 seepage, which makes transportation difficult and easily causes pipeline blockage, increasing the difficulty of management. Although the use of MgO powder as a cementing material and the addition of 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 leads to waste of resources. Therefore, the field of potash mine filling still faces many key technical challenges, especially in the effective treatment of tailing salts (such as NaCl, 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 the full resource utilization of old brine and tailings of potash mines 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 high cementation cost, insufficient filling strength, complex process, low resource utilization and poor slurry performance in the prior art.

[0006] The present application provides a full resource cementation filling process of potash mine old brine-tail salt based on magnesium-calcium synergistic conversion, comprising the following steps: S1. 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 to obtain a solid mixture and a mother liquor after the reaction by solid-liquid separation; 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 the 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; 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 for stirring 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 downhole and fill in multiple layers.

[0007] 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.

[0008] 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.

[0009] As a further improvement of the present application, the water content of the solid mixture is less than 30%.

[0010] 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.

[0011] As a further improvement of the present application, the ball milling activation time is 20 to 40 minutes.

[0012] 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.

[0013] 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.

[0014] 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%.

[0015] The beneficial effects of this application are: The present application 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. CaO is added to the old brine for reaction to obtain a mixed precipitate of Mg(OH)2 / Ca(OH)2, and then a dispersant is added to obtain a solid mixture and a mother liquor after reaction through solid-liquid separation; the tailing salt is divided into coarse tailing salt with a particle size of >75μm and fine tailing salt with a particle size of ≤75μm according to the particle size, and the coarse tailing salt is mechanically ground to a particle size of <50μm to obtain an activated coarse tailing salt; the fine tailing salt is mixed with an activator and activated by ball milling to obtain an activated fine tailing salt; the activated coarse tailing salt, the activated fine tailing salt, the solid mixture, and the mother liquor after reaction are mixed, and a retarder and a water reducer are added for stirring to obtain a filling slurry, which is then pumped underground for filling. The present application 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. The process comprises the following steps: 2+ The Mg(OH)2 / Ca(OH)2 gel phase is generated, and combined with the 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 at 28 days, reducing the overall cost by 45%.

[0016] 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 directional conversion of 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%.

[0017] 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

[0018] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 The present application provides a process flow chart for the full resource-based cementation filling of old brine and tailings from potash mines based on the synergistic conversion of magnesium and calcium. DETAILED DESCRIPTION

[0020] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field 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" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0022] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0023] The existing potash mine 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 a 28-day strength decay rate of more than 30%. In addition, due to the inability to completely absorb the Mg in the old brine, 2+ The slurry is prone to early coagulation (initial coagulation time < 1h), which makes the pipe blockage rate exceed 15% during pipeline transportation. This situation requires frequent pipeline cleaning, which increases the difficulty of operation and maintenance costs. Tailing salt is usually used only as aggregate, and its potential gelling activity is not fully tapped. At the same time, Mg in the old brine 2+ The tail salt crystal filling process mainly focuses on the treatment of tail salt, but it cannot effectively solve the problem of old brine disposal, especially in the recovery of valuable elements in the old brine (such as Mg 2+ ). Traditional cementitious materials have poor applicability. For example, ordinary Portland cement, although widely used in many traditional construction fields, has poor compatibility in potash mine filling, especially in terms of compatibility with old brine. Moreover, the high cost of traditional cementitious materials further limits their application in potash mine tailings filling.

[0024] 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 directional converted by calcium oxide. 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.

[0025] Please refer to Figure 1 The present application embodiment provides a full resource cementation filling process of potash mine old brine-tail salt based on magnesium-calcium synergistic conversion, comprising the following steps: S1. 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 to obtain a solid mixture and a mother liquor after the reaction by solid-liquid separation; 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 the particle size, 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; S3. The activated coarse tail salt, activated fine tail salt, solid mixture, the mother liquor after the reaction was mixed, a retarder and a water reducer were added and stirred to obtain a filling slurry; S4. Pump the filling slurry into the well and fill it in multiple layers.

[0026] 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 the resource utilization of waste liquid. At the same time, the tail salt is activated to improve the utilization rate of the tail salt. The coarse tail salt is mechanically ground to a particle size of <50μm to increase its specific surface area, which helps to increase the speed and degree of chemical reaction between the tail salt and other materials, thereby enhancing the strength of the filling body; the fine tail salt is mixed with the activator for ball milling, which can stimulate the potential active components in the fine tail salt, thereby enhancing the gelling properties and durability of the filling body. By adding retarders and water reducers, the fluidity and stability of the filling slurry are improved, the density and strength of the underground filling are guaranteed, and the safety of the mine is improved. This process effectively reduces the pollution of the waste liquid and tail salt generated in the process of potassium salt mining to the environment, which is beneficial to the protection of the ecological environment. By utilizing the waste in the process of potassium salt mining, the dependence on external raw materials is reduced and the production cost is reduced. This process is simple to operate and easy to implement on the existing mine production line. It is suitable for the treatment of old brine-tail salt in various types of potassium salt mines and has good promotion and application value.

[0027] 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.

[0028] In the technical solution of the embodiment of the present application, the molar ratio of CaO to MgCl2 in the old brine is controlled within an appropriate range to 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.

[0029] 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 that the reaction is fully carried out and to avoid the reduction of production efficiency due to too long a time. The appropriate reaction time is conducive to the formation of 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 conducive to the subsequent solid-liquid separation process, can improve the separation efficiency, and ensure the activity of the precipitate, which is conducive to its application in subsequent processes.

[0030] 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.

[0031] In the technical solution of the embodiment of the present application, sodium hexametaphosphate can effectively reduce the surface tension of the solution and prevent agglomeration between solid particles, thereby improving the dispersibility of the mixed precipitate. The addition amount of sodium hexametaphosphate is controlled at 0.05-0.2% of the mass of the old brine, which can ensure sufficient dispersion effect while avoiding excessive use, reducing costs and possible environmental impacts. The right amount of dispersant can optimize the solid-liquid separation efficiency and improve the purity and quality of the solid product.

[0032] Furthermore, in some embodiments, the water content of the solid mixture is <30%.

[0033] 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 with a moisture content of <30%, which is beneficial for better controlling the rheology and coagulation time of the slurry when preparing the filling slurry, thereby improving the strength and stability of the filling body.

[0034] Furthermore, in some embodiments, in step S2, the stimulant is sodium sulfate, and the added amount is 3-6% of the mass of the fine tail salt.

[0035] In the technical solution of the embodiment of the present application, the stimulator can enhance the activity of the fine tail salt and promote its reaction performance in the subsequent process, thereby improving the coagulation and hardening and mechanical properties of the filling slurry. Controlling the addition amount of sodium sulfate to 3-6% of the mass of the fine tail salt can ensure the stimulating effect while avoiding the cost increase or adverse reactions caused by excessive use.

[0036] Furthermore, in some embodiments, the ball milling activation time is 20 to 40 minutes.

[0037] In the technical solution of the embodiment of the present application, the ball milling time can ensure 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 reaction performance in the filling slurry. At the same time, the appropriate ball milling time helps to improve the particle size distribution of the fine tail salt, making its particles more fine and uniform, which is beneficial to improving the fluidity of the filling slurry and the density of the final filling body.

[0038] Furthermore, in some embodiments, in step S3, the mass ratio of activated coarse tail salt, activated fine tail salt, solid mixture, and mother liquor after reaction is 40~50%: 20~30%: 15~20%: 10~15%.

[0039] In the technical solution of the embodiment of the present application, by accurately 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 and form a more solid structure. The addition of the solid mixture and the mother liquor after the reaction makes the original waste material effectively utilized, reduces environmental pollution, and reduces production costs. Reasonable ratios can ensure that the filling slurry has good working performance during pumping and filling, and reduce problems such as pipeline blockage and uneven filling.

[0040] 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.

[0041] In the technical solution of the embodiment of the present application, the mixture of boric acid and sodium gluconate can effectively prolong the setting time of the filling slurry, so that it maintains good fluidity during pumping and filling, and is easy to operate. By adjusting the ratio of boric acid to sodium gluconate, the setting time of the filling slurry can be accurately controlled to meet the construction requirements under different working conditions. The polycarboxylic acid-based water reducer can significantly improve the fluidity of the filling slurry, reduce the amount of water used, and thus improve the strength and durability of the filling body.

[0042] Furthermore, in some embodiments, 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.

[0043] In the technical solution of the embodiment of the present application, the slurry has good fluidity, which helps the slurry to be smoothly pumped through the pipeline during the filling process, and can be well filled into the gaps and cracks of the mine, improving the filling efficiency and quality. By adding a retarder to extend the setting time, the slurry has enough time to operate after pumping and filling, but can start to solidify quickly to support the early stability of the ore body. The final setting time of 6~8h indicates that the slurry can be completely hardened within a reasonable time after filling, thereby providing sufficient support to ensure the long-term stability of the mine.

[0044] 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%.

[0045] In the technical solution of the embodiment of the present application, the slurry with a high proportion of coarse tailings used for bottom filling can 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 slurry with a high proportion of fine tailings used for surface filling can better fill the gaps between 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. The coarse tailings and fine tailings are effectively utilized to realize the resource utilization of tailings. At the same time, it reduces the discharge of mine waste and promotes the construction of green mines. By optimizing the slurry ratio and construction technology, 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 belongs to the protection scope of this application.

[0046] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used without specifying the manufacturer are all conventional products that can be obtained commercially.

[0047] Example 1 This embodiment provides a full resource cementation filling process of potash mine old brine-tail salt based on magnesium-calcium synergistic conversion, comprising the following steps: S1. Add CaO to the old brine at a molar ratio of CaO:MgCl2 of 1.05:1, react at 70°C for 2h to obtain a mixed precipitate of Mg(OH)2 / Ca(OH)2, with a magnesium-calcium conversion rate of 98.7%. Then, add 0.1% sodium hexametaphosphate dispersant to inhibit particle agglomeration, and use a plate and frame filter press to dehydrate to a moisture content of <30%, with a plate and frame filter press pressure of 0.85MPa to obtain a solid mixture and a mother liquor after reaction; S2. The tail salt is divided into coarse tail salt with a particle size of >75 μm and fine tail salt with a particle size of ≤75 μm according to the particle size, the coarse tail salt is mechanically ground to a particle size of <50 μm to increase the specific surface area to obtain activated coarse tail salt; the fine tail salt is mixed with 5% sodium sulfate and activated by ball milling for 35 minutes to obtain activated fine tail salt; S3. The activated coarse tail salt, activated fine tail salt, solid mixture, the mother liquor after the reaction was mixed in proportion, a retarder and a water reducer were added, and stirred using a special mixer to obtain a filling slurry; S4. The filling slurry is pumped into the well for filling 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.

[0048] Example 2 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.

[0049] Example 3 Example 3 provides a full resource-based cementation filling process for old brine and tailings 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. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be repeated here.

[0050] Comparative Example 1 Comparative Example 1 provides a full resource-based 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 in step S2, neither the coarse tailing salt nor the fine tailing salt is activated. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be repeated here.

[0051] Comparative Example 2 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.

[0052] Comparative Example 3 Comparative Example 3 provides a full resource cementation filling process of potash mine brine-tailing salt based on magnesium-calcium synergistic conversion, which is processed by traditional process and includes the following steps: S1. Raw material pretreatment: Mix the potash mine brine with tailing salt in a mass ratio of 1:1.2, remove impurities and adjust the moisture content to 20%; S2. Addition of cementitious materials: Add magnesium-calcium-based composite gelling agent, and control the addition amount to 10% of the total mass; S3. Homogenization: Mix the raw materials using a biaxial forced mixer at a speed of 30r / min for 20min; S4. Molding and curing: inject the mixed slurry into the mold, let it stand at room temperature for initial setting, and then steam cure (60~80℃, humidity ≥90%) until final setting; S5. Performance test: Test compressive strength, shrinkage rate, permeability coefficient and other indicators according to standard methods.

[0053] The specific test results are shown in Table 1: As can be seen from Table 1, the filling process provided by this application can achieve a filling body 28d strength ≥ 4MPa, a shrinkage rate <1.0%, an initial setting time ≥ 2.5h, a slurry slump ≥ 18cm, and a permeability coefficient ≤ 1×10 -6 cm / s. The strength decay rate of the filling body in this application is relatively low, only 8.5% (28 days), and it has high durability and stability. In contrast, the strength decay rate of the traditional process is 32.0% (28 days), indicating that the performance of the filling body of the traditional process is poor.

[0054] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining 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 of 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 mixed precipitate of Mg(OH)2 / Ca(OH)2, and then a dispersant is added to obtain a solid mixture and a mother liquor after the reaction by solid-liquid separation; 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 the 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-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 for stirring 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 downhole and fill in multiple layers.

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

4. The process for cementing and filling potash mine 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 mine 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 mine 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 mine 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 mine 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 mine 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 bottom layer activated coarse tail salt accounting for 50% and the surface layer activated fine tail salt accounting for 30%.

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