Method for mining soluble potassium from polyhalite ore under temperature and pressure co-control condition

Abstract

The invention discloses a method for mining soluble potassium from polyhalite ore under the temperature and pressure co-control condition. The method comprises the following steps that the actual formation temperature and pressure of an ore bed are obtained through calculation according to the burial depth and the formation condition; preparing leaching solutions with different concentrations according to a chemical reaction equilibrium principle, and screening out an optimal leaching agent type; the method comprises the following steps: carrying out a simulation experiment on an unbroken whole rock core sample by using a temperature and pressure co-control device under a closed condition, and determining the optimal leaching agent concentration and reaction duration; selected leaching liquid is injected into the ore bed, standing is conducted for a period of time under the stratum temperature and pressure condition, and the leaching agent and the ore are made to make full contact and react; and extracting the potassium-containing solution after the reaction, and evaporating and crystallizing to obtain the high-purity potassium salt. The partial neutral salt leaching agent is used, corrosive damage of strong acid and strong alkali to the environment and equipment is avoided, the dosage and cost of the leaching agent are reduced, the ecological environment is protected to the maximum extent, and efficient, economical and environment-friendly mining of the polyhalite ore can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of mining soluble potassium salt in polyhalite, and in particular to a method for mining soluble potassium from polyhalite ore under temperature and pressure co-controlled conditions. Background Art

[0002] Polyhalite It is a poorly soluble sulfate mineral with a high potassium content. As an important nutrient for plant growth, it is of strategic significance and is called the "food" of food. Potassium is widely present in the earth's crust, mainly in the form of potash ores associated with sulfate minerals. The world is rich in potash resources, of which Canada has the largest potash reserves, accounting for about 50% of the world's reserves. In contrast, China's potash reserves account for only 2.2%, and its demand for potash fertilizers ranks first in the world. Therefore, the exploration and mining of potash mineral resources is particularly important. At present, the international potash mining technology is not yet mature and is limited to shallow open-pit mining. The economical and efficient mining of deep potash resources has not yet been realized. The existing technology mainly extracts soluble potash from polyhalite in two ways: one is to dissolve it with deionized water after calcination, and the other is to react with specific acids or salts to prepare potash. For example, U.S. Patents 1981125 and 1956930 use polyhalite to react with lime to prepare potassium sulfate, and Russian Patent 2276123 and Chinese Patent CN102869609A use nitric acid to dissolve polyhalite to extract potassium. However, these methods usually require deep ore to be mined and processed on the ground, which makes it difficult to achieve in-situ extraction. In recent years, domestic research has made progress. Chinese patent 200510021637.X proposes the use of The solution dissolves deep polyhalite, but the solution concentration and leaching conditions are not clear, and the ore needs to be crushed, which increases the difficulty and cost; Chinese patent 201310310354.1 uses acid and alkali solutions for leaching, but the use of strong acids and alkalis is highly corrosive to the well wall pipes, and the potassium salt dissolution rate of different solutions is not quantified, and the influence of temperature and pressure conditions on the dissolution effect is not considered; the current technology still lacks an effective in-situ solution mining method under real formation temperature and pressure conditions.

[0003] Based on this, a method for mining soluble potassium from polyhalite ore under temperature and pressure co-controlled conditions is needed. Summary of the invention

[0004] To achieve the above object, the present invention provides the following scheme: a method for mining soluble potassium from polyhalite ore under temperature and pressure co-controlled conditions, comprising the following steps: Step 1: Calculate and obtain the true formation pressure and formation temperature of the ore layer according to the burial depth and historical burial conditions of the polyhalite ore layer to be mined, wherein the formation pressure ranges from 10 to 50 MPa, and the formation temperature ranges from 50 to 150°C; Step 2: Prepare the leaching solution: According to the principle of chemical reaction equilibrium, prepare the leaching solution that affects the dynamic equilibrium of the leaching reaction. The leaching solution includes , , , , NaCl, Aqueous solution with a concentration of 5% to 10% mass concentration, and mixed with different leaching solutions in a 1:1 volume ratio, the optimal leaching solution concentration is C%, the pH range is 7 to 9, and the solution type with the best reaction efficiency is selected; Step 3: Sample preparation and potassium content analysis: Use the whole core sample to maintain the original geological body void structure, use X-ray fluorescence spectrometer to determine the mineral composition of the sample, calculate the theoretical potassium content, and the determination accuracy is ±5%; Step 4: Temperature and pressure co-control simulation experiment: The blocky polyhalite ore sample was placed in a temperature and pressure co-control device, and different types of leaching solutions were added. Five parallel experiments were set for each leaching solution, corresponding to different leaching times of 24 hours, 48 ​​hours, 72 hours, 96 hours, 120 hours, 192 hours and 240 hours. The experiment was carried out at a temperature of 80°C and a pressure of 30 MPa. The reaction solution was taken out and filtered to determine the content, calculate the dissolution rate, and determine the best leaching solution and optimal leaching time; Step 5, injecting the leaching solution: select the optimal leaching solution type and concentration in step 4, inject the leaching solution into the target formation, control the injection pressure to 30 MPa, and the injection temperature to 90°C during injection, install interlayer devices at the top and bottom of the ore layer at the drilling hole position, ensure that the leaching solution is consistent with the pressure and temperature of the ore layer under the condition of temperature and pressure co-control, and let it stand after closing the well to allow the formation pressure and ground temperature to accelerate the fluidity of the leaching solution, increase the contact and reaction rate between the leaching agent and the ore, and after reaching the optimal leaching time, open the interlayer device to extract the potassium-containing solution in which potassium is dissolved; Step 6: Extracting potassium-containing solution: After the potassium-containing solution is extracted from the formation, it is evaporated and crystallized to obtain potassium salt. The potassium content of the potassium-containing solution reaches 5%, and the purity of the final potassium salt is 95%. The evaporation and crystallization process is carried out under temperature control and pressure conditions to maximize the potassium recovery rate and crystallization efficiency.

[0005] Further preferably, the formation pressure in step 1 is the hydrostatic formation pressure of the polyhalite ore layer, and the formation pressure is determined by a hydrostatic pressure calculation formula or an overlying formation pressure calculation formula; The calculation formula for hydrostatic pressure is: ,in, is the hydrostatic pressure, is the density of water, is the height of the still water column, is the acceleration due to gravity; The calculation formula of overlying formation pressure is: ,in, is the overburden pressure, is the total average density of the overlying rock layer, is the density of the fluid in the void, is the density of the rock skeleton, is the vertical height of the overlying rock layer, is the average porosity of the rock formation, is the acceleration due to gravity.

[0006] Further preferably, in step 2, the dissolution of the polyhalite ore follows the following chemical reaction equilibrium principle:

[0007] The hydrolysis reaction of the polyhalite under roasting conditions is: .

[0008] Further preferably, in step 2, the dissolution reaction of the polyhalite in different solutions is as follows: exist In solution: ; exist In solution: ; In carbonate solutions: ; exist In solution: .

[0009] Further preferably, the configuration of the polyhalite dissolving reactant in step 2 includes 5% and 10% by mass concentration respectively. , , , , NaCl, Solution, wherein the purity of the dissolved reactant is at least analytically pure> 99%.

[0010] Further preferably, the polyhalite sample selection and potassium content analysis in step 3 include the following steps: extracting a complete core sample from the polyhalite ore layer, maintaining its natural void structure to restore the original state of the geological body to the greatest extent, and using an X-ray fluorescence spectrometer The mineral composition of the core samples was analyzed at multiple locations. The theoretical content of potassium in polyhalite is calculated based on the analysis results, and the analysis accuracy is guaranteed to reach ±5%.

[0011] Further preferably, in step 3, the preparation of the polyhalite sample for the temperature-pressure co-control simulation experiment includes the following operations: The selected polyhalite sample is placed in the sample chamber of the autoclave to ensure the integrity and structural uniformity of the sample. Equal amounts of polyhalite raw material samples are accurately weighed and placed in the autoclave respectively. Different types of leaching agents described in step five are added to the samples respectively, and the solid-liquid ratio is adjusted to 1:4. The amount of solution is strictly controlled to simulate the leaching conditions in the ore layer. The autoclave has temperature and pressure adjustment functions to create and maintain temperature and pressure co-controlled experimental conditions.

[0012] Further preferably, the temperature-pressure co-control simulation experiment in step 4 includes the following operating steps: placing a blocky polyhalite sample and a pre-selected leaching agent solution into a temperature-pressure co-control device, and sealing it to simulate the closed dissolution environment in the ore layer, setting the temperature and pressure of the device to match the formation conditions obtained in step 1, wherein the temperature is set to 80°C, the pressure is set to 30 MPa, and different leaching reaction times are set for each type of leaching agent, including 24 hours, 48 ​​hours, 72 hours, 96 hours, 120 hours, 192 hours and 240 hours, and performing multiple groups of parallel experiments respectively, and after each experiment reaches the set reaction time, taking out the reaction solution and filtering it immediately, cooling it to room temperature and measuring the content of the reaction solution. content, and according to the measured The dissolution rate is calculated based on the content and is used to determine the best leaching solution type and optimal leaching time.

[0013] Further preferably, in step 4, The content determination method comprises the following steps: filtering the reaction solution through a 0.45 μm aqueous filter head to remove impurity particles in the solution, diluting the filtered solution to an appropriate concentration, and using an inductively coupled plasma optical emission spectrometer ICP-OES to quantitatively analyze the diluted solution sample to accurately measure the content of the solution. Content; Based on the measured Content data, calculate the dissolution rate of soluble potassium in polyhalite ore.

[0014] Further preferably, after the experiment in step 4 is completed, the comparative experiment of different leaching agents includes: after the temperature-pressure co-control experiment of one leaching agent at seven different reaction time points is completed, another leaching agent is replaced, and the same experimental steps are repeated to ensure the consistency of the experimental conditions of all leaching agents, and the temperature-pressure co-control experiment of each leaching agent at different reaction times and temperature-pressure conditions is carried out. The dissolution rate is systematically measured, and the dissolution effect of each group of data is recorded and analyzed. The potassium dissolution rates of all leaching agents at different reaction times under temperature and pressure co-controlled conditions are compared to determine the optimal leaching agent type, optimal concentration and most appropriate reaction time.

[0015] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: 1. The present invention simulates the temperature and pressure conditions in the real formation environment through the temperature and pressure co-control experiment, thereby truly reproducing the reaction process of polyhalite ore and leaching agent under geological conditions. Different from the prior art, the present invention fully considers the influence of formation temperature and pressure on dissolution equilibrium and dissolution effect. The selected leaching agent and operating conditions have perfect theoretical support, which effectively improves the extraction efficiency of soluble potassium salt and can realize large-scale in-situ mining of deep polyhalite ore.

[0016] 2. The present invention uses a preferred partially neutral salt leaching agent to reduce the amount of leaching agent used while ensuring efficient potassium extraction, reducing the discharge of leaching agent in the formation, reducing the project scale and mining intensity. Compared with the method of using strong acid or strong alkali leaching agents, the present invention has no corrosion risk to the well wall and pipeline, avoids pollution of the groundwater system, protects the ecological environment to the greatest extent, and complies with the green, environmentally friendly sustainable development concept.

[0017] 3. The present invention achieves the effect of sufficient diffusion of the leachate in the pores of the polyhalite ore layer by optimizing the type of leachate and the injection method. Compared with the high-cost operation of the traditional circulating injection of leachate, the present invention adopts a closed static mode to allow the leachate to react with the ore for a long time under the action of formation pressure and temperature, thereby maximizing the dissolution rate of potassium salt and greatly reducing the demand for leachate and operating costs.

[0018] 4. The temperature and pressure co-controlled in-situ mining method provided by the present invention is suitable for polyhalite ores of different burial depths and formation environments. By adjusting the concentration of the solvent and the reaction time, it can flexibly adapt to the geological conditions of different ore layers and successfully extract soluble potassium salts from polyhalite ores at different depths. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a flow chart of the steps of the present invention; Figure 2 This is a schematic diagram of the temperature and pressure co-control experiment of the present invention; Figure 3 It is a process flow chart of on-site operation of the present invention. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Example 1 like Figure 1-3 As shown, in this embodiment, a gypsum-type polyhalite ore layer with a large burial depth is used to simulate the extraction of soluble potassium under the temperature and pressure co-control conditions during the mining process. The experiment uses a new type of underground polyhalite ore layer with a burial depth of 3795 meters, the formation temperature is about 87°C, and the formation pressure is about 48 MPa. The experimental materials and steps are as follows: Experimental materials and equipment,The experiment selected a new type of polyhalite mine located in Huangjin Town, Xuanhan County, Sichuan Province as the experimental object. The natural content of polyhalite is 7.54%. During the sample preparation process, it is ensured that the natural pore structure of polyhalite is not destroyed. The main equipment used in the experiment includes a high-temperature and high-pressure reactor to ensure that the actual temperature and pressure conditions of the ore layer can be simulated; Preparation of leaching solution: In this experiment, the polyhalite ore samples were not crushed in any way, and the whole sample was used directly to ensure the true reducibility of the experimental conditions. The preparation of the leaching solution was based on the principle of chemical reaction equilibrium, and a leaching solution that could maintain stability under high temperature and high pressure conditions was selected. Based on the previous leaching agent type selection experiment, the optimal leaching agent type and concentration for this experiment were determined.

[0024] Experimental steps: The samples were placed in a high-temperature and high-pressure reactor, and the reactor temperature was set to 87°C and the pressure to 48 MPa to ensure that they were consistent with the actual formation temperature and pressure conditions of the polyhalite layer. After the reactor was opened, the samples were left to stand for 8 days to allow the leachate to fully contact the polyhalite ore. During the experiment, the sealing of the reactor and the stability of the temperature and pressure conditions were regularly checked to ensure that the temperature and pressure conditions remained constant throughout the experiment.

[0025] The experimental results show that after the reaction time reaches 8 days, the leaching liquid in the kettle is taken out and the obtained solution is filtered to remove impurities and measured. The concentration of the leaching solution was calculated and the dissolution rate was calculated. The experimental results showed that The concentration reached 17.34 g / L. The total leaching rate is about 90.35%. The results show that under the conditions of high temperature and high pressure in this embodiment, the gypsum-type polyhalite ore The extraction effect is remarkable and it is suitable for deep mining under the conditions of temperature and pressure co-control.

[0026] Embodiment 2: This example selects a shallow rock salt type polyhalite ore layer. The experimental object is an underground rock salt type polyhalite ore layer with a burial depth of 3661 meters. The formation temperature is 85°C and the formation pressure is about 47 MPa. The specific experimental steps and conditions are as follows: Experimental materials and equipment. The ore samples in this experiment were taken from Huangjin Town, Xuanhan County, Sichuan Province. The content is 10.47%, which is a high-potassium content rock salt type polyhalite ore. The experimental equipment is also a high-temperature and high-pressure reactor to accurately simulate the temperature and pressure conditions of the ore layer.

[0027] Preparation of leaching solution: the concentration of 10% was selected for the experiment. The solution is used as the leaching liquid, the solution volume is 2000mL, and the solid-liquid ratio is ensured to be 1:10. As a leaching agent, it is beneficial to the release of potassium in rock salt type polyhalite ore, especially under high temperature and high pressure conditions, which helps to improve Dissolution efficiency; Experimental procedures 200 g of unbroken rock salt type polyhalite sample was directly placed in a high temperature and high pressure reactor to ensure that the pore structure of the sample was not destroyed. The temperature of the reactor was set at 85 °C and the pressure was set at 47 MPa to ensure the simulation of the real temperature and pressure conditions of the ore layer. The temperature and pressure conditions were kept stable throughout the experiment. The reaction time was set to 5 days to allow the leachate to fully contact and react with the rock salt type polyhalite ore under sealed high pressure conditions. Experimental results: After the experiment was completed, the leaching liquid in the kettle was taken out and filtered to obtain 1850 mL of leaching liquid. After testing, the leaching liquid contained The concentration is 9.41 g / L, The dissolution rate is 83.14%. This result shows that under the temperature and pressure co-control conditions of shallow rock salt type polyhalite ore, The leaching agent is able to effectively extract potassium.

[0028] Embodiment 3: This example is based on formation conditions similar to those of Example 2, but different leaching agents are used to further verify the potassium extraction efficiency. The experimental object is a rock salt type polyhalite ore layer with a burial depth of 3662 meters, a formation temperature of 85°C, and a formation pressure of 47 MPa. The solution was used as a leaching agent for leaching experiments; Experimental materials and equipment: The experimental materials are rock salt type polyhalite samples located in Huangjin Town, Xuanhan County, Sichuan Province. The content is 10.88%. The experimental equipment is a high-temperature and high-pressure reactor, which can provide the temperature and pressure co-control conditions required for the experiment; Preparation of leaching solution. This experiment uses 10% concentration of The solution volume is 2000 mL, and the volume of the leaching agent ensures that the solid-liquid ratio with 200 g of rock salt type polyhalite ore sample is 1:10. As a leaching agent, its effect on potassium dissolution efficiency under high temperature and high pressure conditions was evaluated; The experimental steps are as follows: the unbroken rock salt type polyhalite sample is placed in a high temperature and high pressure reactor, and the temperature of the reactor is set to 85℃ and the pressure is set to 47 MPa to simulate the actual geothermal and geopressure conditions of the ore layer, and the reaction conditions are kept stable to ensure that the temperature and pressure remain unchanged during the 5-day reaction time; under closed conditions, The leaching agent fully contacts and reacts with the ore sample.

[0029] Experimental results: After the experiment, the leaching solution was taken out from the reactor and filtered to obtain 1800 mL of leaching solution. The concentration is 9.32 g / L, The dissolution rate was about 77.10%. The results showed that The leaching agent can also effectively extract potassium under this temperature and pressure condition, but the extraction efficiency is lower than that of Slightly lower.

[0030] Through these Examples 1, 2 and 3, the effect of the present invention on extracting potassium under different ore depths and formation conditions is verified. Whether it is a deep gypsum-type polyhalite ore or a shallow rock salt-type polyhalite ore, the method of the present invention can effectively achieve the extraction of potassium. Different leaching agents show good dissolution efficiency under the conditions of temperature and pressure co-control, providing flexible leaching agent selection for different types of polyhalite ores.

[0031] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0032] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for mining soluble potassium from polyhalite ore under temperature and pressure co-controlled conditions, characterized in that: The following steps are involved: Step 1: Calculate and obtain the true formation pressure and formation temperature of the ore layer according to the burial depth and historical burial conditions of the polyhalite ore layer to be mined, wherein the formation pressure ranges from 10 to 50 MPa, and the formation temperature ranges from 50 to 150°C; Step 2: Prepare the leaching solution: According to the principle of chemical reaction equilibrium, prepare the leaching solution that affects the dynamic equilibrium of the leaching reaction. The leaching solution includes , , , , , Aqueous solution with a concentration of 5% to 10% mass concentration, and mixed with different leaching solutions in a 1:1 volume ratio, the optimal leaching solution concentration is C%, the pH range is 7 to 9, and the solution type with the best reaction efficiency is selected; Step 3: Sample preparation and potassium content analysis: Use the whole core sample to maintain the original geological body void structure, use X-ray fluorescence spectrometer to determine the mineral composition of the sample, calculate the theoretical potassium content, and the determination accuracy is ±5%; Step 4: Temperature and pressure co-control simulation experiment: The blocky polyhalite ore sample was placed in a temperature and pressure co-control device, and different types of leaching solutions were added. Five parallel experiments were set for each leaching solution, corresponding to different leaching times of 24 hours, 48 ​​hours, 72 hours, 96 hours, 120 hours, 192 hours and 240 hours. The experiment was carried out at a temperature of 80°C and a pressure of 30 MPa. The reaction solution was taken out and filtered to determine the content, calculate the dissolution rate, and determine the best leaching solution and optimal leaching time; Step 5, injecting the leaching solution: select the optimal leaching solution type and concentration in step 4, inject the leaching solution into the target formation, control the injection pressure to 30 MPa, and the injection temperature to 90°C during injection, install interlayer devices at the top and bottom of the ore layer at the drilling hole position, ensure that the leaching solution is consistent with the pressure and temperature of the ore layer under the condition of temperature and pressure co-control, and let it stand after closing the well to allow the formation pressure and ground temperature to accelerate the fluidity of the leaching solution, increase the contact and reaction rate between the leaching agent and the ore, and after reaching the optimal leaching time, open the interlayer device to extract the potassium-containing solution in which potassium is dissolved; Step 6: Extracting potassium-containing solution: After the potassium-containing solution is extracted from the formation, it is evaporated and crystallized to obtain potassium salt. The potassium content of the potassium-containing solution reaches 5%, and the purity of the final potassium salt is 95%. The evaporation and crystallization process is carried out under temperature control and pressure conditions to maximize the potassium recovery rate and crystallization efficiency.

2. The method for mining soluble potassium from polyhalite ore under temperature and pressure co-controlled conditions according to claim 1, characterized in that: The formation pressure in step 1 is the hydrostatic formation pressure of the polyhalite ore layer, and the formation pressure is determined by a hydrostatic pressure calculation formula or an overlying formation pressure calculation formula; The calculation formula for hydrostatic pressure is: ,in, is the hydrostatic pressure, is the density of water, is the height of the still water column, is the acceleration due to gravity; The calculation formula of overlying formation pressure is: ,in, is the overburden pressure, is the total average density of the overlying rock layer, is the density of the fluid in the void, is the density of the rock skeleton, is the vertical height of the overlying rock layer, is the average porosity of the rock formation, is the acceleration due to gravity.

3. The method for mining soluble potassium from polyhalite ore under temperature and pressure co-controlled conditions according to claim 1, characterized in that: In step 2, the dissolution of the polyhalite ore follows the following chemical reaction equilibrium principle: ; The hydrolysis reaction of the polyhalite under roasting conditions is: .

4. The method for mining soluble potassium from polyhalite ore under temperature and pressure co-controlled conditions according to claim 1, characterized in that: In step 2, the dissolution reaction of the polyhalite in different solutions is as follows: exist In solution: ; exist In solution: ; In carbonate solutions: ; exist In solution: .

5. The method for mining soluble potassium from polyhalite ore under temperature and pressure co-controlled conditions according to claim 4, characterized in that: The configuration of the polyhalite dissolving reagent in step 2 includes 5% and 10% by mass concentration respectively. , , , , , Solution, wherein the purity of the dissolved reactant is at least analytically pure> 99%.

6. The method for mining soluble potassium from polyhalite ore under temperature and pressure co-controlled conditions according to claim 1, characterized in that: The polyhalite sample selection and potassium content analysis described in step 3 include the following steps: Complete core samples were extracted from the polyhalite ore layer, maintaining its natural void structure to restore the original state of the geological body to the greatest extent possible. The mineral composition of the core samples was analyzed at multiple locations. The theoretical content of potassium in polyhalite is calculated based on the analysis results, and the analysis accuracy is guaranteed to reach ±5%.

7. The method for mining soluble potassium from polyhalite ore under temperature and pressure co-controlled conditions according to claim 6, characterized in that: In step 3, the preparation of the polyhalite sample for the temperature and pressure co-control simulation experiment includes the following operations: The selected polyhalite sample is placed in the sample chamber of the autoclave to ensure the integrity and structural uniformity of the sample. Equal amounts of polyhalite raw material samples are accurately weighed and placed in the autoclave respectively. Different types of leaching agents described in step five are added to the samples respectively, and the solid-liquid ratio is adjusted to 1:

4. The amount of solution is strictly controlled to simulate the leaching conditions in the ore layer. The autoclave has temperature and pressure adjustment functions to create and maintain temperature and pressure co-controlled experimental conditions.

8. The method for mining soluble potassium from polyhalite ore under temperature and pressure co-controlled conditions according to claim 1, characterized in that: The temperature and pressure co-control simulation experiment in step 4 includes the following steps: The blocky polyhalite sample and the pre-selected leaching agent solution are placed in a temperature and pressure co-control device and sealed to simulate the closed dissolution environment in the ore layer. The temperature and pressure of the device are set to match the formation conditions obtained in the step 1, wherein the temperature is set to 80°C and the pressure is set to 30 MPa. Different leaching reaction times are set for each type of leaching agent, including 24 hours, 48 ​​hours, 72 hours, 96 hours, 120 hours, 192 hours and 240 hours. Multiple groups of parallel experiments are performed respectively. After each experiment reaches the set reaction time, the reaction solution is taken out and immediately filtered. After cooling to room temperature, the content of the reaction solution is determined. content, and according to the measured The dissolution rate is calculated based on the content and is used to determine the best leaching solution type and optimal leaching time.

9. The method for mining soluble potassium from polyhalite ore under temperature and pressure co-controlled conditions according to claim 8, characterized in that: In step 4, The method for determining the content includes the following steps: The reaction solution was filtered through a 0.45 μm aqueous filter to remove impurity particles in the solution. The filtered solution was diluted to an appropriate concentration and the diluted solution sample was quantitatively analyzed using an inductively coupled plasma emission spectrometer ICP-OES to accurately measure the concentration of Content; Based on the measured Content data, calculate the dissolution rate of soluble potassium in polyhalite ore.

10. The method for mining soluble potassium from polyhalite ore under temperature and pressure co-controlled conditions according to claim 9, characterized in that: After the experiment in step 4 is completed, the comparative experiments of different leaching agents include: After the temperature-pressure co-control experiment of one leaching agent at seven different reaction time points was completed, another leaching agent was replaced and the same experimental steps were repeated to ensure the consistency of the experimental conditions of all leaching agents. The dissolution rate is systematically measured, and the dissolution effect of each group of data is recorded and analyzed. The potassium dissolution rates of all leaching agents at different reaction times under temperature and pressure co-controlled conditions are compared to determine the optimal leaching agent type, optimal concentration and most appropriate reaction time.

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