A method and system for underfilling of a red mud filter press

Abstract

The embodiment of the application discloses a red mud pressure filtration underground cooperative filling method and system, and relates to the technical field of red mud filling. In order to reduce the energy consumption of the filling process, the red mud pressure filtration underground cooperative filling method comprises the following steps: performing pressure filtration treatment on red mud slurry on the ground to obtain filter cake and pressure filtration liquid; wherein the filter cake has a predetermined water content, and the predetermined water content is greater than the water content of the filter cake required for preparing filling material slurry; the filter cake is put into a wellbore, and the filter cake falls to the bottom of the wellbore under the action of gravity; the pressure filtration liquid is transported to a downhole water sump as preparation water, and a cementing material is transported to the downhole; at least the geothermal energy is used to dry the filter cake and heat the preparation water in the downhole water sump; the filter cake, the cementing material and the preparation water are transported to a stirring mechanism to be stirred to obtain filling material slurry; and the filling material slurry is transported to a downhole filling area to be filled. The embodiment of the application is suitable for the red mud filling scene.

Description

Technical Field

[0001] This application relates to the field of red mud backfilling technology, and in particular to a method and system for red mud pressure filtration and downhole co-backfilling. Background Technology

[0002] my country's alumina industry generates over 100 million tons of red mud annually, primarily stored on the surface. This not only occupies vast amounts of land resources but also poses a significant risk of soil and groundwater pollution due to the leakage of its highly alkaline substances. Mixing red mud with cementitious materials to prepare backfill slurry and transporting it to underground goaf areas is the mainstream technical approach to achieving "treating two hazards from one waste." However, with the continuous increase in mining depth, backfilling operations in ultra-deep wells exceeding 800 meters in depth face new technical challenges.

[0003] In ultra-deep wells, if traditional high-pressure pumping methods are used to transport filling slurry from the surface to the well, the pipelines must withstand extremely high pressures, typically at least 10 MPa. This results in high equipment costs and enormous energy consumption. The filter cake required for preparing the filling slurry generally has a moisture content of 5-10%. While direct surface filtration to a moisture content of 5-10% for deep dewatering of the red mud slurry can reduce the burden of downhole drying, the deep dewatering process itself requires significant energy, and the investment cost of dewatering equipment is high. Conversely, directly transporting high-moisture-content red mud slurry downhole for treatment faces constraints such as limited downhole space and complex construction conditions. Summary of the Invention

[0004] In view of this, embodiments of this application provide a method and system for co-filling red mud filter press wells, which can reduce the energy consumption of the filling process.

[0005] In a first aspect, embodiments of this application provide a method for co-filling red mud filtration in wells, comprising: filtration treatment of red mud slurry at the surface to obtain filter cake and filtrate; wherein the filter cake has a predetermined moisture content, the predetermined moisture content being greater than the moisture content of the filter cake required for preparing the filling slurry; placing the filter cake into a wellbore, the filter cake falling to the bottom of the wellbore under gravity; conveying the filtrate to a downhole water tank as preparation water; conveying a cementing material downhole; at least using geothermal energy to dry the filter cake and heating the preparation water in the downhole water tank; conveying the filter cake, cementing material, and preparation water downhole to a stirring mechanism for stirring to obtain a filling slurry; and conveying the filling slurry to the downhole area to be filled for filling.

[0006] Optionally, the process of pressing and filtering the red mud slurry to obtain a filter cake includes: a predetermined moisture content of 10-15%; a filter cake particle size of 10-100 mm; and a filter cake thickness of 5-40 mm.

[0007] Optionally, the red mud filter press well co-filling method further includes: during the fall of the filter cake in the wellbore, the filter cake moves relative to the air in the wellbore, the air in the wellbore forms an airflow on the surface of the filter cake, the particles on the surface of the filter cake are peeled off by the airflow, exposing a new surface, and at the same time, a local low-pressure zone is formed at the peeling location, which promotes the diffusion of moisture inside the filter cake to the surface.

[0008] Optionally, the red mud filter press downhole co-filling method further includes: during the falling process of the filter cake in the wellbore, the return airflow in the wellbore forms an upward resistance on the filter cake to prolong the falling time of the filter cake.

[0009] Optionally, the step of using the return airflow in the well shaft to create upward resistance on the filter cake and prolong the falling time of the filter cake includes: the connection position between the return air shaft and the well shaft is located in the upper middle part of the well shaft, and the section of the well shaft from the bottom of the well shaft to the connection position between the return air shaft and the well shaft is a return air action zone; an upward return airflow is formed in the return air action zone; the return airflow comes into countercurrent contact with the filter cake to create upward resistance, and the resistance of the return airflow on the filter cake is used to prolong the falling time of the filter cake.

[0010] Optionally, the step of conveying the filter cake, cementing material, and preparation water to the mixing mechanism downhole includes: measuring the filter cake using a metering conveyor scale, measuring the cementing material using a metering scale, and measuring the preparation water using a flow meter, so as to control the ratio of the filter cake, cementing material, and preparation water input into the mixing mechanism.

[0011] Optionally, before conveying the filter cake to the stirring mechanism for stirring, the method further includes: detecting the real-time moisture content of the filter cake; and when the moisture content data of the filter cake fluctuates, adjusting the amount of filter cake, cementing material, and / or preparation water input to the stirring mechanism according to a preset material balance model.

[0012] Optionally, adjusting the amounts of filter cake, cementing material, and / or preparation water input to the stirring mechanism according to a preset material balance model includes ensuring that the mass of filter cake, cementing material, and preparation water required to prepare a unit mass of filling slurry satisfies the following formula relationship: M filter ×(1-W1) / (M filter +M cement +M water )=C0; M cement / (M filter +M cement +M water =R; M water =M filter ×W1+△W; where M filter For filter cake quality, M cement For the quality of cementitious materials, M water To determine the water quality, C0 is the target mass concentration of the filling slurry, R is the preset cementitious material ratio, W1 is the real-time moisture content of the filter cake, and ΔW is the mass of water that needs to be added, calculated based on the target mass concentration of the filling slurry and the measured moisture content of the filter cake.

[0013] Secondly, embodiments of this application provide a red mud filter press downhole co-filling system for implementing the red mud filter press downhole co-filling method described in any of the first aspects, comprising: a filter press, the filter press being provided with a red mud slurry inlet, a filter cake outlet, and a filter liquid outlet, the filter press being used to filter the red mud slurry to produce a filter cake with a predetermined moisture content; a wellbore, the filter cake outlet being connected to the top inlet of the wellbore for allowing the filter cake to fall to the bottom of the wellbore under gravity; and a downhole filter cake storage bin at the bottom of the wellbore. The filter press is connected to the feed inlet of the downhole filter cake storage silo; a downhole water silo is connected to the filter press outlet; a stirring mechanism is used to mix and stir the red mud material, cementing material and preparation water input into the stirring mechanism to prepare filling slurry; a filling pump is connected to the filling slurry outlet B of the stirring mechanism, and the filling pump is used to transport the prepared filling slurry to the downhole filling area; wherein, the filter press is located on the surface, and the stirring mechanism and the filling pump are located downhole.

[0014] Optionally, the red mud filter press well co-filling system further includes a return air well; the return air well is connected to the well casing, the return air well extends obliquely upward, and the angle between the return air well and the well casing is 30~60°.

[0015] The red mud filter press and downhole co-filling method and system provided in this application have the following beneficial effects: 1. Filter cake is obtained by pressing red mud slurry on the ground. The filter cake has a predetermined moisture content, which is greater than the moisture content of the filter cake required to prepare the filling slurry. This eliminates the need to use industrial energy to press the filter cake to a lower moisture content required to prepare the filling slurry, thereby reducing the energy consumption of the filter cake drying process. 2. The filter cake is placed into the well shaft, where it falls to the bottom under gravity, reducing the energy consumption for conveying the filter cake. 3. Using the filtrate as preparation water reduces the amount of wastewater discharged during the filling process and lowers the energy consumption for treating the discharged wastewater; 4. Utilize geothermal energy from the mine to dry the filter cake and heat the preparation water, thereby reducing the energy consumption of using industrial energy for drying the filter cake and heating the preparation water; 5. The filter cake, preparation water, and cementing material are transported downhole, where the raw materials are stirred to prepare the filling slurry. This slurry is then transported downhole to the area to be filled, which reduces the pumping pressure and thus the energy consumption required to pump the filling slurry. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a red mud filter press and downhole co-filling method according to an embodiment of this application; Figure 2 This is a schematic diagram of a red mud filter press downhole co-filling system according to an embodiment of this application; In the diagram, 10 is a filter press; 20 is a well shaft; 30 is an underground filter cake storage bin; 40 is a mixing mechanism; 401 is a mixer A; 402 is a mixer B; 50 is a filling pump; 60 is a return air shaft; 70 is a metering conveyor scale; 80 is a screening machine; 90 is a crusher; 100 is a conveyor A; 110 is a surface water storage tank; 120 is an underground water tank; 130 is a water supply pump; 140 is an underground cementitious material storage bin; 150 is a metering scale; 160 is a conveyor B; 170 is a flow meter; and 180 is a regulating valve. Detailed Implementation

[0018] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0019] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0020] Example 1 See Figure 1 This application provides a method for co-filling red mud filter press wells, comprising: S100. Red mud slurry is subjected to pressure filtration on the ground to obtain filter cake and filtrate; wherein the filter cake has a predetermined moisture content, which is greater than the moisture content of the filter cake required for preparing the filling slurry; S101. The filter cake is placed into the wellbore, and the filter cake falls to the bottom of the wellbore under the action of gravity. The filtrate is transported to the well water tank as preparation water, and the cementing material is transported to the well. S102. The filter cake is dried using geothermal energy at least underground, and the preparation water in the underground water tank is heated using geothermal energy. S103. The filter cake, cementitious material and preparation water are transported to the stirring mechanism in the well for stirring to obtain filling slurry; S104. The filling slurry is transported to the downhole area to be filled for filling.

[0021] The required moisture content of the filter cake for preparing filling slurry is generally 5-10%, which requires the use of industrial electricity or chemical energy and other industrial energy sources to press the filter cake to a moisture content of 5-10%, which consumes a lot of energy. In this embodiment, the red mud slurry is press-filtered on the ground to obtain the filter cake and filtrate. The filter cake is pressed to a predetermined moisture content that is higher than that required for the conventional preparation of filling slurry, without the need to use industrial energy to press the filter cake to a lower moisture content than that required for the conventional preparation of filling slurry, thus reducing the energy consumption of the filter cake drying process.

[0022] The filter cake is placed into the wellbore and falls to the bottom of the wellbore under the action of gravity. This reduces the need to lay filter cake conveying pipelines in the wellbore, thus reducing the cost of filter cake conveying. At the same time, the filter cake's own weight is used to fall to the bottom of the well, which solves the power problem of filter cake conveying. No additional power conveying device is required, realizing zero-energy underground material conveying and reducing the energy consumption of conveying filter cake.

[0023] Transporting the filtrate to the underground water tank for preparation water reduces the amount of filtrate discharged as wastewater, thus lowering environmental pollution. On the other hand, wastewater generally requires certain treatment before discharge, while using filtrate as preparation water can improve resource utilization, reduce the consumption of clean water, and reduce the energy consumption required for treating wastewater.

[0024] When processing red mud slurry into filter cake on the surface, it is not necessary to reduce the moisture content of the filter cake to an extremely low level. Instead, a predetermined moisture content margin is maintained, and the filter cake is dried using geothermal energy in the mine. This reduces the moisture content of the filter cake and lowers the energy consumption for surface filtration using industrial energy. When preparing filling slurry, heating the preparation water is beneficial for both the uniformity of the filling slurry and the hydration reaction between the filtrate components and the cementitious materials in the preparation water, thus improving the quality of the filling slurry. Surface filling slurry preparation generally requires heating the preparation water using industrial energy. However, by transporting the filtrate to an underground water tank and using geothermal energy to heat the preparation water in the underground water tank to prepare the filling slurry, the energy consumption for heating the preparation water in the industrial water tank can be reduced, thereby lowering energy costs.

[0025] The mixing mechanism and other equipment required for preparing the filling slurry are located underground. The filter cake, cementing material, and preparation water are all transported underground. The filter cake, cementing material, and preparation water are mixed and thoroughly stirred underground to prepare the filling slurry. After the filling slurry is prepared underground, it is directly transported to the area to be filled underground for filling. In this way, filter cake with a predetermined moisture content is prepared by pressure filtration at the surface, and the raw materials such as filter cake, cementing material, and preparation water are transported to the underground. The raw materials prepared at the surface in a certain state work together with the filling slurry prepared underground, reducing the energy consumption of the filling process.

[0026] Because the filter cake is transported from the wellbore to the downhole using its own gravity, and the filling slurry is prepared downhole, there is no need to lay a high-pressure pumping pipeline capable of withstanding at least 10MPa pressure from the surface to the downhole, nor is there a need to configure high-pressure pumping equipment. This fundamentally solves the equipment cost and energy consumption problems caused by long-distance high-pressure pumping in ultra-deep wells. Only the pipeline for the filling slurry needs to be laid downhole to the area to be filled. This can reduce the pipelines required to transport the filter cake in the wellbore, and also avoid the need to lay high-compressive-strength filling slurry transport pipelines in the wellbore when preparing the filling slurry on the surface and transporting it downhole for filling. Only the filling slurry pipeline needs to be arranged downhole, which can save the laying cost of the transport pipeline. Furthermore, the filling slurry prepared downhole can be transported to the filling area using low-power pumping equipment, eliminating the need for high-power pumping equipment. This reduces pumping pressure, thereby lowering the energy consumption required for pumping the filling slurry, reducing energy consumption and equipment costs in the filling process. It also reduces the risk of segregation and pipe blockage during long-distance transportation of the filling slurry, as well as the energy wasted due to the drop in pumping pressure during long-distance transportation. This allows for rapid transportation of the filling slurry to the filling area, improving filling process efficiency, stability, and reliability.

[0027] In some embodiments, the process of pressure filtration of red mud slurry to obtain filter cake includes: a predetermined moisture content of 10-15%; a filter cake particle size of 10-100 mm; and a filter cake thickness of 5-40 mm.

[0028] When performing filter cake pressure filtration, controlling the predetermined moisture content of the filter cake within the range of 10-15% reduces the power consumption of the filter cake preparation equipment, eliminating the need for high-power equipment and lowering the cost of selecting such equipment. Controlling the particle size of the prepared filter cake within 10-100mm ensures sufficient structural strength, preventing breakage due to airflow resistance during its descent within the wellbore, while also providing a larger surface area for evaporation, thus improving drying efficiency. The thickness of the filter cake directly affects the path length for moisture to diffuse from its interior to its surface. A thinner filter cake shortens this diffusion path, improving drying efficiency and reducing drying time. A filter cake thickness of 5-40mm effectively reduces internal moisture migration and diffusion resistance, allowing air in the wellbore to more easily carry away moisture, reducing energy consumption, while simultaneously ensuring sufficient structural strength to prevent breakage during descent.

[0029] In some embodiments, the red mud slurry is press-filtered to form a circular filter cake with a diameter ranging from 10 to 100 mm. However, the shape of the filter cake is not required to be a regular circle. The radial dimension of the filter cake is guaranteed to be within the range of 10 to 100 mm. When the red mud slurry is press-filtered to form a square filter cake, the diameter of the outer circle of the square filter cake is in the range of 10 to 100 mm.

[0030] In some embodiments, the closer the filter cake formed by pressing red mud slurry is to a circle, the more stable its posture is during the falling process, enabling it to contact the air in the wellbore in a stable manner. This facilitates stable drying of the filter cake, improves the stability of the moisture content treatment, and enhances the stability of the quality of the filling slurry. Before placing the filter cake into the wellbore, the roundness of the filter cake is set to 0.8–1, and the aspect ratio of the circumscribed rectangle is set to 1–1.4. The roundness of the filter cake is calculated using the formula: Roundness = 4π × Area / Perimeter^2, where the area and perimeter are the area and perimeter of the near-circular top or bottom surface of the filter cake, and the aspect ratio of the circumscribed rectangle is the ratio of the length and width of the smallest circumscribed rectangle. The closer the roundness of the filter cake is to 1, the closer its shape is to a circle; the closer the aspect ratio is to 1, the closer the shape is to a constant diameter; the more regular the shape, the more conducive it is to the stability of the drying process.

[0031] In some embodiments, the red mud filter press co-filling method further includes: during the fall of the filter cake in the shaft, the filter cake is dried using the ground temperature; based on the average geothermal gradient of 3℃ / 100m, there is a temperature difference between the surface and the bottom of the shaft for mines of different depths. The deeper the mine, the greater the temperature difference between the surface and the bottom of the shaft. There is also a corresponding geothermal gradient in the shaft. If the filter cake is dried using independent drying equipment, a large amount of energy is required. When the filter cake is dried using the ground temperature during the fall of the filter cake in the shaft, the energy consumption for drying the filter cake in the filling process can be reduced.

[0032] In some embodiments, under conditions such as specified filter cake particle size, predetermined filter cake moisture content, average temperature in the shaft, average relative humidity, and shaft depth, the gravity acting on the filter cake is essentially the same. The relative convection velocity between the filter cake and the return airflow in the shaft is related to the return airflow velocity, and the return airflow velocity can be adjusted. The temperature gradient in the mine is limited by natural conditions. The two work together to dry the filter cake, thereby reducing energy consumption. Generally, the return air velocity is based on the actual needs in the mine, avoiding the need to increase additional energy consumption for controlling the return air velocity to achieve filter cake drying. Under normal circumstances, convection is the dominant factor in drying, and temperature is an auxiliary enhancing factor. However, when the mine depth is large and the temperature at the bottom of the shaft is high, geothermal energy at the bottom of the shaft can be used to improve the drying efficiency of the filter cake to a certain extent.

[0033] In some embodiments, the red mud filter press well co-filling method further includes: during the falling of the filter cake in the wellbore, the filter cake moves relative to the air in the wellbore, the air in the wellbore forms an airflow on the surface of the filter cake, the particles on the surface of the filter cake are peeled off by the airflow, exposing a new surface, and at the same time, a local low-pressure zone is formed at the peeling location, which promotes the diffusion of moisture inside the filter cake to the surface.

[0034] During the descent of the filter cake in the well shaft, the air moving relative to the filter cake creates an airflow on its surface. As particles on the boundary layer of the filter cake surface are stripped and renewed by the airflow, these particles detach from the filter cake, exposing new surfaces. Simultaneously, the areas where particles are stripped create localized low-pressure zones, generating a suction negative pressure effect on the interior of the filter cake. Combined with the capillary diffusion effect of the internal capillary micropore structure of the filter cake, this promotes the diffusion of moisture from the interior of the filter cake to its surface. Furthermore, the detachment of particles from the filter cake surface increases the contact area between the filter cake and the airflow, thereby increasing the rate of moisture evaporation from the filter cake surface and improving the efficiency of the filter cake drying process.

[0035] Furthermore, the filter cake conveying and drying processes are combined into the same process flow. When the filter cake falls to the bottom of the well, it already has a suitable moisture content and can be directly mixed with cementing materials and preparation water to prepare filling slurry. Drying is completed at the same time as the filter cake is conveyed, which simplifies the process flow, has a high degree of process integration, and helps to reduce the overall energy consumption of the filling process and improve the filling process efficiency.

[0036] In some embodiments, the red mud filter press downhole co-filling method further includes: during the fall of the filter cake in the wellbore, the filter cake compresses the air in the wellbore, causing the air temperature to rise, thereby drying the filter cake; the filter cake compresses the air in the wellbore, especially the air on the windward side of the filter cake is compressed and heated during the fall of the filter cake, and the compressed and heated air can promote the evaporation of moisture in the filter cake, thereby drying the filter cake and reducing the moisture content in the filter cake; furthermore, after the moisture on the surface of the filter cake evaporates, the relative humidity in the air near the surface of the filter cake decreases, and there is a concentration gradient of moisture between the interior and surface of the filter cake. This concentration gradient drives the moisture inside the filter cake to diffuse to the surface of the filter cake, and then diffuses into the airflow, thereby achieving the drying treatment of the filter cake.

[0037] In some embodiments, the red mud filter press downhole co-filling method further includes: during the falling of the filter cake in the wellbore, the filter cake moves relative to the air in the wellbore, and the air in the wellbore forms an airflow on the surface of the filter cake. The airflow continuously removes moisture from the surface of the filter cake, so that a certain moisture concentration gradient is maintained between the interior of the filter cake and its surface. The moisture concentration gradient between the interior of the filter cake and its surface drives the moisture inside the filter cake to diffuse to the surface of the filter cake, thereby reducing the moisture content in the filter cake and achieving the drying treatment of the filter cake, thereby reducing the energy consumption of the filling process for drying the filter cake.

[0038] In some embodiments, the red mud filter press downhole co-filling method further includes: during the falling of the filter cake in the wellbore, the airflow formed on the surface of the filter cake by the air moving relative to the filter cake can penetrate the gaps between the filter cake particles, increase the gas-solid contact area on the surface of the filter cake, promote the evaporation of moisture on the surface of the filter cake, thereby reducing the moisture content in the filter cake, achieving the drying treatment of the filter cake, and improving the drying rate of the filter cake.

[0039] In some embodiments, the red mud filter press well co-filling method further includes: during the falling process of the filter cake in the wellbore, the return airflow in the wellbore forms an upward resistance to the filter cake, prolonging the falling time of the filter cake; the wellbore is connected to the return air shaft, and after the filter cake falls to the position where the wellbore and the return air shaft are connected, the return airflow flowing from bottom to top in the wellbore generates an upward resistance to the free fall of the filter cake. The resistance generated by the return airflow on the filter cake helps to slow down the speed at which the filter cake falls freely under its own gravity, thereby prolonging the falling and drying time of the filter cake in the wellbore, allowing the filter cake to undergo a longer drying process in the wellbore, and using the return airflow to fully dry the filter cake, reducing the moisture content in the filter cake.

[0040] In some embodiments, the method of using the return airflow in the shaft to create upward resistance on the filter cake and prolong the falling time of the filter cake includes: the connection position between the return air shaft and the shaft is located in the upper middle part of the shaft, and the shaft section from the bottom of the shaft to the connection position between the return air shaft and the shaft is a return air action section; an upward return airflow is formed in the return air action section; the return airflow comes into countercurrent contact with the filter cake to create upward resistance, and the resistance of the return airflow on the filter cake is used to prolong the falling time of the filter cake.

[0041] The connection position between the return air shaft and the shaft determines the specific section affected by the return airflow. The connection position between the return air shaft and the shaft is located in the upper part of the shaft. In the return air action section, the upward return airflow forms a countercurrent contact with the downward filter cake. The resistance generated by the return airflow on the filter cake prolongs the falling time of the filter cake in the shaft, allowing the filter cake to be fully dried. This reduces the energy consumption required for the equipment in the filling system to dry the filter cake, further enhances evaporative drying, and achieves efficient evaporative drying of the filter cake in the shaft, thereby improving the efficiency of the filling process.

[0042] In some embodiments, the well shaft is a vertical shaft with a depth greater than 800m, and a geothermal gradient increasing along the depth direction is formed in the well shaft; the filter cake is dried using air in the well shaft during its descent, and the method further includes: drying the filter cake using the increasing geothermal temperature during its descent.

[0043] Based on the average geothermal gradient of 3℃ / 100m, the geothermal temperature varies at different depths within the wellbore, and the actual geothermal gradient in mines at different latitudes may be greater than the average. In wellbores deeper than 800m, the geothermal temperature promotes the evaporation of moisture in the filter cake during its descent, thus drying the filter cake and reducing its moisture content. The geothermal temperature in the wellbore increases along the depth direction, i.e., from the wellhead to the bottom. Correspondingly, under the heating of this gradient geothermal temperature, the air at different heights within the wellbore is also heated to varying degrees, forming an increasing air temperature gradient along the depth direction. During the descent of the filter cake, it comes into contact with the air whose temperature increases along the depth direction, driving the moisture inside the filter cake to migrate and diffuse to the surface. This utilizes the geothermal gradient to dry the filter cake, reducing the energy consumed by the equipment required for drying the filter cake during the filling process.

[0044] In some embodiments, the step of conveying the filter cake, cementing material, and preparation water to the mixing mechanism downhole includes: measuring the filter cake using a metering conveyor scale, measuring the cementing material using a metering scale, and measuring the preparation water using a flow meter, so as to control the ratio of the filter cake, cementing material, and preparation water input to the mixing mechanism.

[0045] As the main solid components of the filling slurry, filter cake and cementitious materials have stable solid content, which means that the filling slurry has stable rheological properties and the quality stability of the filling body formed by the filling slurry, ensuring the early strength, setting time and long-term stability of the filling body. Filter cake is generally not guaranteed to be completely dry. When the filter cake has a certain moisture content, problems such as sticking to the wall, arching and unstable feeding may occur during transportation. Using a metering conveyor scale can complete the metering simultaneously during transportation, avoiding fluctuations in the amount of filter cake transported and improving the metering accuracy of the filter cake. Cementitious materials are generally free-flowing powdery materials. They can be metered using an integrated metering and conveying device or metered separately using a metering scale and transported by another conveying device. This allows for the combination of different metering scales and conveying devices, reducing the cost of metering and conveying devices and ensuring the metering accuracy of cementitious materials. The amount of preparation water is metered using a flow meter to control the ratio of filter cake, cementitious materials and preparation water input to the stirring mechanism. Preparing the filling slurry according to the specified ratio can improve the quality and quality stability of the filling slurry, thereby improving the quality and quality stability of the filling body formed by the filling slurry.

[0046] In some embodiments, before the filter cake is conveyed to the stirring mechanism for stirring, the method further includes: detecting the real-time moisture content of the filter cake; and when the moisture content data of the filter cake fluctuates, adjusting the amount of filter cake, cementing material and / or preparation water input to the stirring mechanism according to a preset material balance model.

[0047] The moisture content of the filter cake is a key parameter determining the rheological properties of the subsequent filling slurry. If the moisture content fluctuation is not monitored, the concentration of the filling slurry after mixing will deviate from the design value, thus affecting the pumpability and quality stability of the filling slurry. Although excessively high moisture content in the filter cake can reduce the viscosity of the filling slurry, it will increase the volume of ineffective water, increase the pumping flow rate requirement and water treatment costs. Conversely, excessively low moisture content will result in an overly thick filling slurry, significantly increasing pumping pressure and energy consumption. By monitoring the moisture content of the filter cake in real time before it is conveyed to the mixing mechanism, a data basis is provided for dynamically controlling the concentration of the filling slurry. Based on the fluctuation of the filter cake moisture content data and according to the preset material balance model, the amount of filter cake, cementing material and / or preparation water input to the mixing mechanism can be adjusted to avoid energy waste or blockage risks caused by empirical proportions, thereby improving the quality stability of the prepared filling slurry.

[0048] Even if the amount of raw materials used to prepare the filling slurry is adjusted according to the real-time moisture content of the filter cake and the preset material balance model, the actual output filling slurry concentration may not reach the target concentration due to various other reasons. In some embodiments, the concentration of the filling slurry output from the stirring mechanism is detected. Based on the feedforward change of the online monitoring signal of the filter cake moisture content detected before the filter cake enters the stirring mechanism and the preset material balance model, if the filling slurry concentration deviates from the preset target value, the amount of filter cake, cementing material and / or preparation water input into the stirring mechanism is adjusted.

[0049] By detecting the actual concentration of the filling slurry output from the mixing mechanism, it is confirmed whether the concentration of the prepared filling slurry has indeed reached the target concentration. If the concentration of the filling slurry has not reached the target concentration, the concentration of the prepared filling slurry is corrected by adjusting the amount of filter cake, cementing material and / or preparation water input to the mixing mechanism. Based on the feedforward change of the online monitoring signal of filter cake moisture content obtained before the filter cake enters the mixing mechanism, the deviation signal of the filling slurry concentration output from the mixing mechanism from the preset target value, and the preset material balance model, the input amount of materials for preparing the filling slurry is dually detected and adjusted. Compared with relying on a single detection link or passive adjustment, this method can more effectively ensure that the prepared filling slurry has the expected and stable properties, and improve the quality stability of the prepared filling slurry.

[0050] In some embodiments, adjusting the amounts of filter cake, cementing material, and / or preparation water input to the stirring mechanism according to a preset material balance model includes: the mass of filter cake, cementing material, and preparation water required to prepare a unit mass of filling slurry must satisfy the following formula relationship: M filter ×(1-W1) / (M filter +M cement +Mwater )=C0; M cement / (M filter +M cement +M water =R; M water =M filter ×W1+△W; where M filter For filter cake quality, M cement For the quality of cementitious materials, M water For the preparation of water quality, C0 is the target mass concentration of the filling slurry, R is the preset cementitious material ratio, W1 is the real-time moisture content of the filter cake, and ΔW is the mass of water to be added calculated based on the target mass concentration of the filling slurry and the measured moisture content of the filter cake. The amount of each raw material required for preparing the filling slurry is calculated according to the preset material balance model and input into the stirring mechanism for filling slurry preparation. When factors such as the concentration of the filling slurry and the moisture content of the filter cake change, the amount of each raw material input into the stirring mechanism is recalculated according to the above formula and controlled. The ratio of filter cake, cementitious material and preparation water is dynamically adjusted to improve the quality stability of the prepared filling slurry, avoid rework and raw material waste caused by non-compliance of filling slurry quality, and reduce the complexity of the filling process, thereby reducing the energy consumption of the filling process and the cost of preparing the filling slurry.

[0051] It should be noted that the moisture dissipation characteristics of red mud filter cake depend on its inherent physical properties such as pore structure, particle size distribution, and bound water state. Different batches of red mud may have different moisture dissipation characteristics due to differences in source and process. Here, the inherent physical properties of red mud are taken as the standard, and the differences between different batches are compensated by a preset material balance model. That is, the real-time moisture content of the filter cake is detected before entering the mixing mechanism, and the ratio of cementitious material and preparation water is dynamically adjusted according to the actual moisture content to ensure that the moisture content of the final filling slurry meets the filling requirements.

[0052] In some embodiments, before conveying the filter cake to the stirring mechanism for stirring, the process further includes: screening the filter cake to form undersize and oversize materials; conveying the undersize to the stirring mechanism for preparing filling slurry, and crushing the oversize material before conveying it to the stirring mechanism for preparing filling slurry; performing preliminary screening of the filter cake, crushing the oversize material, and then conveying it to the stirring mechanism for preparing filling slurry ensures the uniformity of the red mud material particle size entering the stirring mechanism, while avoiding excessive crushing of all filter cake material by a crusher, which would lead to energy waste, thereby reducing the energy consumption of the filling process and improving the efficiency of the filling process.

[0053] In some embodiments, the red mud filter press downhole co-filling method further includes: utilizing the elevation difference between the surface and the bottom of the well to transport the filter fluid to the bottom of the well by gravity, thereby reducing the energy consumption of pumping the filter fluid to the bottom of the well; and using the geothermal temperature at the bottom of the well to heat the filter fluid, thereby reducing the energy consumption of separately setting up a heating device to heat the filter fluid, which not only reduces the energy consumption of artificial heating, but also improves the fluidity of the filling slurry, reduces the energy consumption of the filling process, and improves the efficiency of the filling process.

[0054] In some embodiments, the step of conveying the filter cake, cementitious material, and preparation water to a stirring mechanism for stirring downhole includes: setting up a mixer A and a mixer B for two-stage stirring; stirring in mixer A for a time A to allow the materials to be initially mixed evenly; conveying the materials in mixer A to mixer B for a time B to form a filling slurry with the required concentration and slump; wherein, during the stirring time B in mixer B, the alkaline components in the filter press penetrate into the surface of the red mud particles and couple with the hydration of the cementitious material to generate hydrated calcium aluminosilicate gel.

[0055] In mixer A, the materials are initially mixed uniformly for a mixing time A. After this initial mixing, the materials in mixer A are transferred to mixer B for a further mixing time B, ultimately forming a filling slurry with the target concentration and slump. During the mixing time B in mixer B, the alkaline components such as sodium hydroxide and sodium carbonate in the filtrate can penetrate into the surface of the red mud particles and undergo a coupling reaction with the hydration of the cementitious material, generating hydrated calcium aluminosilicate gel. This in-situ activates the potential cementitious activity of the red mud material, partially replacing the amount of expensive cementitious material used, thereby reducing the cost of the filling process to some extent. It should be noted that the above coupling reaction can occur both during the initial mixing stage in mixer A and during the mixing time B in mixer B. However, during the mixing time B in mixer B, the materials used to prepare the filling slurry are mixed more thoroughly, resulting in a larger contact area and a significantly increased coupling reaction rate and a more complete reaction. In some embodiments, the red mud filter press co-filling method further includes: maintaining the average relative humidity of the air in the shaft within the range of 60-90%; in order to utilize convection and temperature gradient for drying the filter cake, adjusting the ventilation conditions in the mine shaft to maintain the average relative humidity of the air in the shaft within the range of 60-90%.

[0056] Relative humidity has a significant impact on drying efficiency. When the relative humidity is between 60% and 70%, the air has a strong capacity to hold water vapor, the surface moisture of the filter cake evaporates quickly, and the drying efficiency is high. When the relative humidity is between 70% and 85%, drying can still be carried out effectively, but the efficiency decreases. When the relative humidity exceeds 85%, the air is close to saturation, and moisture evaporation is significantly hindered. The relative humidity of the air is naturally maintained by the mine ventilation system without the need for additional dehumidification or humidification equipment. However, it should be noted that when the filter cake falls to the depths of the shaft, the air temperature rises to 35-55°C due to the geothermal gradient, and the saturated vapor pressure of the air increases accordingly. The relative humidity will automatically decrease, thus maintaining effective drying efficiency even in a high humidity environment.

[0057] In some embodiments, the red mud filter press downhole co-filling method further includes: determining the specific surface area of ​​the filter cake by the discharge parameters of the filter cake outlet of the filter press; the specific surface area of ​​the filter cake directly affects the size of the gas-solid contact area and the moisture evaporation interface; indirectly fixing the specific surface area of ​​the filter cake by controlling the discharge parameters of the filter cake outlet, specifically, the particle size range of the filter cake is controlled within 10~100mm, and the thickness range is controlled within 5~40mm; in addition, the particles on the surface of the filter cake fall off, exposing new surfaces, further increasing the specific surface area. This process is naturally determined by the material's own characteristics and the falling height, without the need for additional equipment to intervene.

[0058] It should be noted that the upward resistance of the return airflow on the free fall of the filter cake includes the superposition effect of the filter cake's falling velocity and the return airflow velocity in the shaft. As the filter cake falls freely in the shaft, it quickly reaches its terminal velocity due to air resistance. The terminal velocity varies depending on the particle size of the filter cake: approximately 21 m / s for 20 mm, approximately 30 m / s for 50 mm, approximately 31 m / s for 80 mm, and approximately 35 m / s for 100 mm. Simultaneously, there is usually an upward return airflow in the shaft, with a velocity generally in the range of 1-5 m / s. The relative velocity between the filter cake's falling velocity and the return airflow velocity in the shaft determines the convective drying intensity of the filter cake surface. The airflow velocity is jointly determined by the terminal velocity of the filter cake's free fall and the return air velocity in the shaft, without the need for additional ventilation equipment for forced regulation.

[0059] After the filter cake is discharged from the filter press, it is in the form of irregular blocks or flakes, and its shape will affect the aerodynamic characteristics during the falling process. Here, no additional granulation or shaping treatment is performed on the filter cake. The filter cake is directly put into the well shaft in its original form after filtration, avoiding the need for additional filling process and reducing the energy consumption of the filling process.

[0060] Example 2 See Figure 2This application provides a red mud filter press downhole co-filling system for implementing the method described in any one of the embodiments, including: a filter press 10, a wellbore 20, a downhole filter cake storage bin 30, a downhole water bin 120, a stirring mechanism 40, and a filling pump 50. The filter press 10 is provided with a red mud slurry inlet, a filter cake outlet and a filtrate outlet. The filter press 10 is used to filter red mud slurry to produce a filter cake with a predetermined moisture content. The filter cake outlet is connected to the top inlet of the well shaft 20, so that the filter cake falls to the bottom of the well shaft 20 under the action of gravity; The bottom of the well shaft 20 is connected to the feed inlet of the downhole filter cake storage bin 30; The downhole water tank 120 is connected to the filter fluid outlet; The stirring mechanism 40 is used to mix and stir the red mud material, cementing material and preparation water input into the stirring mechanism 40 to prepare filling slurry; The inlet of the filling pump 50 is connected to the filling slurry outlet B of the stirring mechanism 40. The filling pump 50 is used to transport the prepared filling slurry to the underground filling area. The filter press 10 is located on the surface, while the stirring mechanism 40 and the filling pump 50 are located underground.

[0061] In this embodiment, red mud slurry is fed into filter press 10 for filter dewatering to produce filter cake. The filter cake outlet of filter press 10 is connected to the top inlet of well shaft 20. The filter cake produced by filter press 10 is fed into well shaft 20 from the top inlet. The filter liquid produced by filter press 10 is transported to the underground water tank 120 through the filter liquid outlet.

[0062] The filter cake falls through the wellbore 20 under gravity into the downhole filter cake storage chamber 30 for storage, which reduces the need to lay filter cake conveying pipelines in the wellbore, thereby reducing filter cake conveying costs and energy consumption. The filter cake is dried in the downhole filter cake storage chamber 30 using geothermal energy, which reduces the moisture content of the filter cake without consuming additional industrial energy, thus reducing the energy consumption required for the drying process.

[0063] When using a filter press 10 to filter red mud slurry on the surface, a predetermined moisture content is reserved for the filter cake. This eliminates the need to use the filter press 10 to filter the filter cake to an extremely low moisture content. This reduces the energy consumption of the filter press 10 and the energy required to transport the filling slurry downhole. It also shortens the working time of the filter press 10, reducing the energy consumption in the process of preparing red mud into filling slurry. Furthermore, it provides a buffer space for the moisture content of the filter cake in the wellbore 20 to offset the humidity fluctuations of the red mud slurry raw material itself, ensuring the quality of the filling slurry. It also shortens the working time of the filter press 10, thereby solving the high energy consumption problem caused by the active dispersing, drying, or secondary slurry preparation of the filter cake in the existing technology, and improving the efficiency of the filling process.

[0064] The filling slurry is a relatively viscous fluid. In the existing technology, the filling slurry is transported to the wellbore 20 for filling. In order to ensure the safe delivery of the filling slurry to the wellbore, a filling slurry transportation pipeline with high compressive strength is required, which means high cost. By setting the mixing mechanism 40 and the filling pump 50 downhole, the filter cake, cementing material and preparation water in the downhole filter cake storage bin 30 are fed into the mixing mechanism 40 through the red mud material inlet, cementing material inlet and preparation water inlet, respectively. The mixing mechanism 40 mixes and stirs the red mud material, cementing material and preparation water to prepare the filling slurry. This can avoid the pressure of the filling slurry on the transportation pipeline during the preparation of the filling slurry on the surface and the transportation of the filling slurry to the wellbore 20, thus reducing the risk of pipe burst.

[0065] Transporting the filter cake to the downhole via the shaft 20 saves the cost of laying filter cake delivery pipelines and filling slurry delivery pipelines within the shaft 20. The filling slurry is prepared downhole, and after being pressurized by the filling pump 50 in the mixing mechanism 40, it is transported to the downhole filling area through the filling slurry pipeline. This eliminates the need for a high-power filling pump 50, and only requires the laying of a filling slurry pipeline between the outlet of the filling pump 50 and the area to be filled. This saves costs, reduces the energy consumption of the filling pump 50, and shortens the filling slurry pumping time, thereby reducing energy consumption and improving efficiency in the filling process.

[0066] In some embodiments, the red mud filter press downhole co-filling system further includes a return air well 60; the return air well 60 is connected to the wellbore 20, the return air well 60 extends obliquely upward, and the angle between the return air well 60 and the wellbore 20 is 30~60°.

[0067] Shaft 20 is connected to return air shaft 60, expelling polluted or harmful air from underground to the surface. Return air shaft 60 extends obliquely upwards to prevent filter cake from falling into it during its descent within shaft 20. The angle between return air shaft 60 and shaft 20 is 30-60°. During return air flow in return air shaft 60, the optimized airflow distribution from bottom to top within shaft 20 facilitates the entry of return air into return air shaft 60 and maintains airflow velocity, establishing a stable airflow between shaft 20 and return air shaft 60. The bottom-up return airflow in shaft 20 is conducive to the stable drying of the filter cake. When the angle between return air shaft 60 and shaft 20 is less than 30°, it is not conducive to the construction of return air shaft 60. When the angle between return air shaft 60 and shaft 20 is greater than 60°, when the airflow below the connection point between shaft 20 and return air shaft 60 reaches the connection point, it will pass the connection point between shaft 20 and return air shaft 60 under its inertia, making it difficult to establish a stable airflow between shaft 20 and return air shaft 60, which is not conducive to the drying of the filter cake.

[0068] On the one hand, the resistance generated by the airflow on the filter cake extends the falling time of the filter cake in the wellbore 20, allowing the filter cake to be fully dried and reducing the energy consumption required for the equipment in the filling system to dry the filter cake. On the other hand, it ensures that the airflow can stably dry the filter cake, avoiding uneven drying caused by unstable airflow, which would reduce the drying quality of the filter cake.

[0069] In some embodiments, the wellbore 20 is a vertical shaft with a depth greater than 800m, and a geothermal gradient increasing along the depth direction is formed within the wellbore 20. The vertical shaft allows for full utilization of the filter cake's transport to the wellbore under gravity. The increasing geothermal gradient along the depth direction within the wellbore 20 provides gradient heating of the filter cake, promoting a decrease in its moisture content. In a deep well with a depth greater than 800m, the terminal velocity achievable is greater than in a wellbore 20 with a depth less than 800m. This allows for the convection of air and filter cake within the wellbore 20 to promote evaporation of moisture from the filter cake, thereby accelerating the drying process.

[0070] In some embodiments, in deep wells deeper than 800m, under the influence of a geothermal temperature gradient of 25~30℃ / km, the wellbore 20 at a depth less than 800m can provide air with a higher temperature and greater thermal potential energy, thereby driving the internal moisture of the filter cake to migrate and diffuse to the surface of the filter cake more quickly, resulting in better drying effect and higher drying rate, and improving the efficiency of the filling process. For deep wells deeper than 800m, transporting the filling slurry from the surface to the well requires the pumping pipeline to withstand a high pressure of more than 10MPa, and long-distance filling slurry pumping pipelines need to be laid, which poses the risk of pipe bursting and high investment costs. However, by placing the stirring mechanism 40 and the filling pump 50 underground, the material is processed and stirred to prepare the filling slurry at a depth of 800m, avoiding the high cost caused by laying the filling pump 50 pipeline from the surface to the well, significantly reducing equipment investment and operation and maintenance costs, and eliminating the risk of pipe bursting in long-distance high-pressure pumping.

[0071] It should be noted that the falling time of the filter cake in the wellbore 20 is related to the depth of the wellbore 20, the size of the filter cake, and air resistance. Taking an 800m deep well as an example, when the return airflow velocity is 5m / s, under the resistance of the return airflow on the filter cake, the terminal velocity of the filter cake is approximately 15~25m / s, corresponding to a falling time of approximately 32~53 seconds. Taking a 1000m deep well as an example, the falling time is approximately 40~67 seconds. Within the above falling time, the filter cake is in full contact with the air inside the wellbore 20. By utilizing convection and geothermal gradient to dry the filter cake, the moisture content of the filter cake can be reduced from 10~15% to 5~10%.

[0072] In some embodiments, the drying process of the filter cake in the wellbore 20 is further divided into the following coordinating sections according to the depth from the wellhead: 0~200m is the wellhead section, 200~600m is the intermediate section, and above 600m is the deep section. In the wellhead section, the surface temperature of the filter cake is close to the surface temperature of about 15~20°C, and the temperature difference with the air in the wellbore 20 is small. The surface moisture evaporates mainly by gravity-driven airflow generated on the surface of the filter cake, and the moisture content of the filter cake slowly decreases from 10~15%. In the intermediate section, the ground temperature gradually rises to about 20~35°C, and the geothermal temperature in the wellbore 20 rises accordingly. The temperature difference between the geothermal temperature and the filter cake drives moisture to migrate to the surface of the filter cake, and the drying rate accelerates. In the deep section, the ground temperature of about 35~55°C is significantly higher than that of the surface. The thermal potential energy further drives the moisture inside the filter cake to migrate and diffuse to the low-temperature region. At the same time, the compression of the air by the filter cake raises the air temperature, and the drying efficiency reaches its peak. The filter cake is dried in the above multiple coordinating sections to improve the drying efficiency and drying quality of the filter cake.

[0073] In some embodiments, the shaft 20 is a feeding shaft or an existing mine shaft 20. The drying process utilizes gravity conveying within the shaft 20 to replace mechanical pumping, and involves drying the filter cake using airflow generated on the filter cake surface within the shaft 20, drying the filter cake using the temperature rise generated by air compression, drying the filter cake using the geothermal gradient within the shaft 20, and drying the filter cake using bottom-up return air within the shaft 20. The drying process also utilizes the convection between the filter cake and the air within the shaft 20, as well as the temperature gradient within the shaft 20. With the dual energy-saving effect of using gradient drying to dry the filter cake instead of traditional thermal drying, the energy consumption for drying the filter cake can be reduced by more than 80% compared with traditional thermal drying. The filter cake is transported by gravity through the wellbore 20 to prepare filling slurry. Only the filling slurry pumping pipeline and the filling pump 50 are installed underground. The filling pump 50 only needs to overcome the friction of the filling slurry pumping pipeline, and the pumping pressure is significantly reduced. The overall maximum pumping pressure of the filling pump 50 and the filling slurry pumping pipeline can be controlled within 5MPa.

[0074] In some embodiments, the filter cake produced by the filter press 10 from the red mud slurry has a predetermined moisture content range of 10~15%; the filter cake produced by the filter press 10 from the red mud slurry has a particle size range of 10~100mm; and the filter cake has a thickness range of 5~40mm.

[0075] When selecting the filter press 10, it is not necessary to choose a high-power filter press 10, thus reducing equipment costs. At the same time, the filter press 10 does not need to consume high energy to filter the red mud slurry to a low level. In terms of pressure, by controlling the filtration pressure and time, the predetermined moisture content of the filter cake is controlled between 10 and 15%. It is not necessary to process the filter cake to the 5 to 10% moisture content required for direct preparation of the filling slurry. The filter cake is dried by utilizing the convection between the filter cake and the air in the well 20 and the geothermal gradient in the well 20. This not only reduces the energy consumption required to press the filter cake to a moisture content of 5 to 10% by the filter press 10, but also provides a buffer space for subsequent moisture content adjustment to offset the humidity fluctuations of the raw material itself, improve the quality stability of the dried filter cake, and thus improve the quality stability of the prepared filling slurry, thereby reducing the energy consumption of the filter press 10 and the energy consumption required for drying the filter cake.

[0076] Regarding the size of the filter cake, the larger the particle size and the thinner the filter cake, the higher the energy consumption of the filter press 10. By controlling the particle size range of the filter cake to 10~100mm and the thickness range to 5~40mm, the air in the well cylinder 20 is fully utilized to dry the filter cake, thereby reducing the energy consumption requirements of the filter press 10. This reduces the energy consumption required for the filling process and lowers the equipment cost.

[0077] In some embodiments, after the red mud slurry is pressed into filter cake by the filter press 10, the filter cake is transported to the wellhead of the wellbore 20 by a belt conveyor or other conveying equipment for delivery, so that the filter cake falls into the filter cake storage bin 30 in the wellbore 20 by gravity.

[0078] In some embodiments, the red mud filter press downhole co-filling system further includes a metering conveyor scale 70, a screening machine 80, a crusher 90, and a conveyor A100; the bottom outlet of the downhole filter cake storage bin 30 is equipped with a gate, the outlet end of which corresponds to the inlet end of the metering conveyor scale 70, the outlet end of which is connected to the inlet of the screening machine 80, and the undersize material of the screening machine 80 is connected to the red mud material inlet of the stirring mechanism 40 through the conveyor A100; the oversize material outlet of the screening machine 80 is connected to the inlet of the crusher 90, and the outlet of the crusher 90 is connected to the red mud material inlet of the stirring mechanism 40 through the conveyor A100; the bottom outlet of the downhole filter cake storage bin 30 is equipped with a gate to control the filter cake discharge amount, and the outlet end of the gate is correspondingly equipped with the inlet end of the metering conveyor scale 70, through which the filter cake is accurately weighed. The metering conveyor 70 is connected to the inlet of the screening machine 80 to perform preliminary screening of the filter cake material. The undersize material is conveyed to the red mud material inlet of the mixing mechanism 40 via the conveyor A100 for the preparation of the filling slurry. The oversize material outlet of the screening machine 80 is connected to the inlet of the crusher 90. The filter cake is crushed by the crusher 90 and then fed into the conveyor A100 via the crusher 90 outlet. It is then conveyed to the mixing mechanism 40 via the red mud material inlet for the preparation of the filling slurry. The synergistic processing mode of screening first and then crushing the oversize material ensures the uniformity of the red mud material entering the mixing mechanism 40. At the same time, it avoids the energy waste caused by over-crushing all the filter cake material by the crusher 90, which can reduce the energy consumption of the filling process and improve the filling process efficiency.

[0079] In some embodiments, the red mud filter press downhole co-filling system further includes a surface water storage tank 110, a downhole water tank 120, and a water supply pump 130; the filter press 10 is provided with a filter fluid outlet, which is connected to the inlet of the surface water storage tank 110; the outlet of the surface water storage tank 110 is connected to the inlet of the downhole water tank 120 via a filter fluid delivery pipe A; the outlet of the downhole water tank 120 is connected to the inlet of the water supply pump 130; and the outlet of the water supply pump 130 is connected to the preparation water inlet of the stirring mechanism 40 via a filter fluid delivery pipe B; wherein, the filter fluid in the downhole water tank 120 is heated by the ground temperature; and the filter fluid is press-filtered... The filtrate produced by the filter press 10 is collected and temporarily stored in a surface water storage tank 110. Then, the filtrate in the surface water storage tank 110 is pumped to the underground water tank 120 for the preparation of filling slurry. This solves the problem of water waste and waste of alkaline components in the filtrate during the harmless treatment of the filtrate, and realizes the underground recycling and reuse of the filtrate. In the well, the filtrate in the underground water tank 120 is pumped to the stirring mechanism 40 by the water supply pump 130 for the preparation of filling slurry. The filtrate is heated by geothermal energy in the underground water tank 120, which reduces the energy consumption of artificial heating, improves the fluidity of the filling slurry, reduces the energy consumption of the filling process, and improves the efficiency of the filling process.

[0080] In some embodiments, the filtrate is transported to a surface water storage tank 110 for storage and later use, or directly transported to a downhole water tank 120 via gravity flow or low-pressure pipeline. In the downhole water tank 120, the filtrate is heated to about 30°C using the ground temperature. When preparing the filling slurry, the filtrate in the downhole water tank 120 is pumped to the stirring mechanism 40 by a water pump 130 as preparation water for stirring the filling slurry. This reduces the energy consumption of artificial heating, improves the fluidity of the filling slurry, and retains the active components in the filtrate, providing the temperature conditions for the alkaline components in the filtrate to undergo an alkaline activation reaction when the filling slurry is prepared in the stirring mechanism 40.

[0081] In some embodiments, the stirring mechanism 40 includes a mixer A401 and a mixer B402; the red mud material inlet, the cementitious material inlet, and the preparation water inlet of the stirring mechanism 40 are located on the mixer A401; the discharge port of the mixer A401 is connected to the inlet of the mixer B402; the filling slurry discharge port of the stirring mechanism 40 is located on the mixer B402 and is connected to the inlet of the filling pump 50; in the process of preparing the filling slurry, the staged stirring mode of initial mixing followed by thorough mixing can make the filling slurry preparation more efficient. The prepared filling slurry is fully uniform to ensure its quality. The red mud material inlet, cementitious material inlet, and preparation water inlet of the mixing mechanism 40 are set in mixer A401. The metered filter cake red mud material, metered filtrate, and metered cementitious material are transported to mixer A401 for mixing time A to achieve preliminary uniform mixing. After preliminary uniform mixing, the material in mixer A401 is transported to mixer B402 for further mixing time B to finally form a filling slurry with the target concentration and slump.

[0082] In some embodiments, the time A for stirring the metered filter cake red mud material, metered filtrate, and metered cementitious material in mixer A401 is 1 minute; after initial uniform mixing, the time B for stirring the materials in mixer B402 is 2-4 minutes; the total stirring time in mixer A401 and mixer B402 is controlled at 3-5 minutes, ultimately forming a filling slurry with a mass concentration of 65-70% and a slump of 250-270 mm; the mixers A401 and B402 are twin-shaft horizontal forced mixers.

[0083] In some embodiments, the red mud filter press downhole co-filling system further includes a controller, a downhole cementitious material storage bin 140, a weighing scale 150, and a conveyor B160. The outlet of the downhole cementitious material storage bin 140 is connected to the inlet of the weighing scale 150, the outlet of the weighing scale 150 is connected to the inlet of the conveyor B160, and the outlet of the conveyor B160 is connected to the cementitious material feed port of the stirring mechanism 40. The outlet of the downhole cementitious material storage bin 140 is connected to the inlet of the weighing scale 150, which accurately measures the cementitious material required for preparing the filling slurry, ensuring the proportion of cementitious material for preparing the filling slurry. The outlet of the weighing scale 150 is connected to the inlet of the conveyor B160, and the cementitious material accurately measured by the weighing scale 150 is conveyed to the cementitious material feed port of the stirring mechanism 40 via the conveyor B160 for preparing the filling slurry.

[0084] The controller is electrically connected to the metering scale 150. The controller controls the metering scale 150 based on the data from the metering scale 150. The metering scale 150 measures the cementitious material output from the outlet of the underground cementitious material storage bin 140 and transmits the data to the controller. The controller determines whether the cementitious material measured by the metering scale 150 meets the requirements for preparing the filling slurry. If the amount of cementitious material output from the metering scale 150 is insufficient to prepare the filling slurry, the controller controls the metering scale 150 to increase or decrease the output of cementitious material. When the cementitious material output from the metering scale 150 is insufficient to prepare the filling slurry, the output of cementitious material is increased; when the amount of cementitious material output from the screw metering scale is greater than the amount required to prepare the filling slurry, the output of cementitious material is decreased.

[0085] A moisture content meter is installed at the outlet of the downhole filter cake storage bin 30. The moisture content meter is electrically connected to the controller. The moisture content meter detects the moisture content of the filter cake output from the outlet of the downhole filter cake storage bin 30 in real time and transmits the data to the controller. A concentration meter is installed at the filling slurry outlet of the mixing mechanism 40 to detect the concentration of the finished filling slurry in real time. The concentration meter is electrically connected to the controller. The controller runs a proportional-integral-derivative control algorithm. Based on the data from the moisture content meter, the data from the metering conveyor scale 70, the data from the flow meter 170, and the data from the metering scale 150, as well as the preset filling slurry mass target value, for example, setting the preset filling slurry mass concentration to 70%, it determines whether the amount of material delivered to the mixing mechanism 40 meets the requirements for preparing the filling slurry.

[0086] When the moisture content detector detects fluctuations in the filter cake moisture content, the controller immediately calculates the amount of filter cake, cementing material, or preparation water that needs to be compensated based on the preset material balance model, and adjusts the gate opening, the frequency converter of the metering scale 150, and / or the opening of the regulating valve 180 accordingly. The response time of this process is shortened to less than 5 seconds. The concentration meter at the discharge port of the filling slurry of the stirring mechanism 40 detects the concentration of the finished filling slurry in real time. If it deviates from the target value, the controller calculates the amount of filter cake, cementing material, or preparation water that needs to be compensated, and adjusts the gate opening, the frequency converter of the metering scale 150, and / or the opening of the regulating valve 180 accordingly, forming a closed-loop control. This solves the problem of unstable filling body quality caused by large fluctuations in the moisture content of the red mud slurry raw material, ensuring accurate control of the concentration of the final filling slurry prepared by the stirring mechanism 40, and reducing the energy consumption of the filling process and the cost of preparing the filling slurry due to inaccurate filling slurry concentration.

[0087] In some embodiments, the moisture content detector is a microwave online moisture content detector; the concentration meter is a nuclear concentration meter.

[0088] In some embodiments, a cementitious material silo is provided on the surface, and cement, slag powder and other cementitious materials are transported from the surface cementitious material silo to the underground cementitious material storage silo 140 for temporary storage via a surface pneumatic conveying device. Compared with the traditional high-pressure pumping method, the pneumatic conveying method has lower energy consumption, but still requires the configuration of pneumatic conveying equipment and pipelines. In contrast, the filter cake is conveyed by gravity, directly using gravity to put the filter cake into the well, without any power conveying equipment, which has more obvious advantages in energy saving and economy.

[0089] When preparing filling slurry, the material is weighed and measured by a weighing scale 150 and conveyed to a mixing mechanism 40 by a conveyor B160. The weighing scale 150 is a screw weighing scale, which can uniformly and continuously convey powdered or granular materials such as cement and slag powder through the rotation of the screw blades and perform dynamic measurement by a weighing device. It is suitable for conveying cementitious materials that require continuous and stable feeding and accurate measurement. The conveyor B160 is a double screw conveyor, which achieves a larger conveying capacity through two parallel screws. During the screw conveying of cementitious materials, the screws tumble and break up some of the clumps of cementitious materials, improving the uniformity of the cementitious materials and preventing material blockage.

[0090] In some embodiments, the red mud filter press downhole co-filling system further includes a controller; the controller is electrically connected to the metering conveyor scale 70 and the gate, and the controller controls the opening degree of the gate according to the data of the metering conveyor scale 70; the controller determines whether the amount of filter cake output from the discharge end of the gate meets the amount of filter cake required to prepare the filling slurry according to the data of the metering conveyor scale 70; if the amount of filter cake output from the discharge end of the gate is insufficient, the controller increases the opening degree of the gate; if the amount of filter cake output from the discharge end of the gate is excessive, the controller decreases the opening degree of the gate, so that the amount of filter cake output from the output end of the gate matches the amount of filter cake required to prepare the filling slurry.

[0091] In some embodiments, the metering conveyor scale 70 is a metering belt scale, which weighs the filter cake on the conveyor belt while continuously conveying the filter cake. At the same time, it measures the running speed of the conveyor belt through a speed measuring device, thereby calculating the flow rate and cumulative total amount of filter cake conveyed per unit time. It has a simple structure, is easy to install, has low maintenance costs, high metering accuracy, and is easy to combine with a controller to measure and statistically analyze the amount of filter cake conveyed. The conveyor A100 is a conveyor belt, which can continuously convey materials. It has a simple structure, stable operation, low noise, and large conveying capacity, and can realize long-distance conveying, making it suitable for continuous production. The gate is an electro-hydraulic flat gate, which is controlled by electro-hydraulic drive to open and close the gate. It has a large driving force and flexible and reliable opening and closing. It has good sealing performance and can effectively control material leakage. It can be combined with a controller for automated control and frequent operation.

[0092] In some embodiments, the red mud filter press downhole co-filling system further includes a controller, a flow meter 170, and a regulating valve 180; the flow meter 170 and the regulating valve 180 are installed on the filter press delivery pipeline B; the controller is electrically connected to the flow meter 170, the regulating valve 180, and the feed pump 130. The controller controls the pumping power of the feed pump 130 according to the data from the flow meter 170, and simultaneously controls the opening of the regulating valve 180. The two work together to regulate the flow rate of the filter press required for preparing the filling slurry; the flow meter 170 is used to detect the flow rate of the filter press output from the downhole water tank 120. The controller determines whether the flow rate of the filter press output from the downhole water tank 120 meets the requirements for preparing the filling slurry according to the data from the flow meter 170. The controller adjusts the valve opening of the regulating valve 180 to match the amount of filter press required for preparing the filling slurry with the amount of filter press delivered from the downhole water tank 120 to the stirring mechanism 40.

[0093] In some embodiments, the flow meter 170 is an electromagnetic flow meter. The electromagnetic flow meter works based on Faraday's law of electromagnetic induction and is not affected by changes in parameters such as fluid density, viscosity and temperature. It is suitable for various working conditions, has a simple structure, low pressure loss, is suitable for large flow measurement, and can reflect flow changes in real time. This is beneficial for the automated control of filling slurry preparation and filling in conjunction with a controller. The regulating valve 180 is an electric regulating valve. The actuator of the electric regulating valve has high control accuracy, fast response speed and smooth adjustment action. This is beneficial for achieving precise control and frequent adjustment of filling slurry preparation and filling in conjunction with the electromagnetic flow meter and the controller.

[0094] In some embodiments, a pressure transmitter is also provided on the filtrate delivery pipeline B. The pressure transmitter is electrically connected to the controller. The pressure transmitter is used to wet-monitor the pressure value of the filtrate in the filtrate delivery pipeline B to determine whether the pressure in the delivery pipeline is within the safe operating range, preventing abnormal pressure caused by blockage or leakage in the delivery pipeline. The controller judges the operating status of the feed water pump 130 based on the pressure change in the delivery pipeline detected by the pressure transmitter. When the pressure rises abnormally, it indicates that there may be a blockage in the delivery pipeline, and the controller automatically reduces the pumping power of the feed water pump 130 or stops the pump for protection. The controller also combines the data from the flow meter 170 to judge the characteristic changes of the delivery pipeline through the pressure-flow relationship, providing a reference for adjusting the opening of the regulating valve 180, thereby ensuring the stability of the filtrate delivery, ensuring the stable supply of water for filling slurry preparation, and the safe operation of the filtrate delivery pipeline B and the feed water pump 130.

[0095] In some embodiments, the controller adjusts the motor speed of the water pump 130 by controlling the frequency of the inverter of the water pump 130, thereby controlling the pumping power of the water pump 130. This control of the pumping power enables coarse adjustment of the filtrate flow rate, while controlling the opening of the regulating valve 180 enables fine adjustment. The controller operates a proportional-integral-derivative control algorithm, based on the mass fraction of filter cake moisture content detected by the moisture content meter, the filter cake conveying capacity measured by the metering conveying scale 70 (in tons / hour), and the flow meter 170 (in cubic meters). The flow rate of the filtrate (m³ / h) and the amount of cementitious material conveyed (tons / h) measured by the metering scale 150 are used to calculate the theoretical proportions of each material based on a preset material balance model. These proportions are then compared with actual test values ​​to determine whether the amount of each material conveyed to the stirring mechanism 40 meets the requirements for preparing the filling slurry. The controller, through a proportional-integral-derivative control algorithm, a moisture content meter, other detection sensors, and metering control devices such as the metering conveying scale 70, coordinates the adjustment of the proportions of each material to improve the concentration control accuracy of the filling slurry to ±2%, ensuring the dynamic stability of the filling slurry quality.

[0096] In some embodiments, for ease of calculation, the calculation is based on the mass of filter cake, cementitious material, and preparation water required to prepare a unit mass of filling slurry. The mass of the dry filter cake after removing moisture and the mass of moisture in the filter cake can be calculated based on the real-time moisture content of the filter cake detected by the moisture content meter and the mass of the filter cake measured by the metering conveyor scale 70. It is understood that the moisture content in the cementitious material is approximately 0, therefore the mass of the cementitious material measured by the metering scale 150 can be substituted into the above formula for calculation. The controller calculates the target conveying volume of each material required to prepare the filling slurry in real time according to the preset material balance model, and compares it with the detection data from the metering conveyor scale 70, the metering scale 150, and the flow meter 170. Through a proportional-integral-derivative control algorithm, the controller outputs control signals to adjust the gate opening, the frequency converter frequency of the metering scale 150, and / or the opening of the regulating valve 180, thereby achieving the desired mass concentration of the prepared filling slurry.

[0097] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. The terms “center,” “longitudinal,” “lateral,” “length,” “width,” “thickness,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0098] The above description is merely a specific implementation of the embodiments of this application, but the protection scope of the embodiments of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of this application should be included within the protection scope of the embodiments of this application. Therefore, the protection scope of the embodiments of this application should be determined by the protection scope of the claims.

Claims

1. A method for co-filling red mud filter press wells, characterized in that, include: Red mud slurry is subjected to pressure filtration on the surface to obtain filter cake and filtrate; wherein the filter cake has a predetermined moisture content, which is greater than the moisture content of the filter cake required for preparing the filling slurry; The filter cake is placed into the wellbore, where it falls to the bottom of the wellbore under the influence of gravity. The filtrate is then transported to the well water tank as preparation water, and the cementing material is transported downhole. The filter cake is dried using geothermal energy at least underground, and the preparation water in the underground water tank is heated using geothermal energy. The filter cake, cementitious material, and preparation water are transported to a stirring mechanism in the well for stirring to obtain a filling slurry. The filling slurry is transported to the downhole area to be filled for filling.

2. The red mud pressure filtration and downhole co-filling method according to claim 1, characterized in that, The process of pressing and filtering red mud slurry to obtain filter cake includes: a predetermined moisture content of 10-15%; a filter cake particle size of 10-100 mm; and a filter cake thickness of 5-40 mm.

3. The red mud pressure filtration and downhole co-filling method according to claim 1, characterized in that, Also includes: During the fall of the filter cake in the well shaft, the filter cake moves relative to the air in the well shaft. The air in the well shaft forms an airflow on the surface of the filter cake, and the particles on the surface of the filter cake are peeled off by the airflow, exposing a new surface. At the same time, a local low-pressure zone is formed at the peeling location, which promotes the diffusion of moisture from the inside of the filter cake to the surface.

4. The method for co-filling red mud filter press wells according to claim 1, characterized in that, Also includes: During the descent of the filter cake in the well shaft, the return airflow in the well shaft creates upward resistance on the filter cake, extending the descent time.

5. The red mud pressure filtration and downhole co-filling method according to claim 4, characterized in that, The method of utilizing the return airflow in the well shaft to create upward resistance on the filter cake and prolong the falling time of the filter cake includes: The connection between the return air shaft and the shaft is located in the upper middle part of the shaft, and the section of the shaft from the bottom of the shaft to the connection between the return air shaft and the shaft is the return air function zone. An upward return airflow is formed within the return air zone; The return airflow comes into countercurrent contact with the filter cake, creating upward resistance. This resistance of the return airflow on the filter cake prolongs the falling time of the filter cake.

6. The method for co-filling red mud filter press wells according to claim 1, characterized in that, The step of conveying the filter cake, cementitious material, and preparation water to the stirring mechanism downhole includes: The filter cake is measured using a metering conveyor scale, the cementitious material is measured using a metering scale, and the preparation water is measured using a flow meter, so as to control the ratio of the filter cake, cementitious material, and preparation water input into the stirring mechanism.

7. The method for co-filling red mud filter press wells according to claim 1, characterized in that, Before the filter cake is conveyed to the stirring mechanism for stirring, the following steps are also included: The real-time moisture content of the filter cake was detected; When the moisture content of the filter cake fluctuates, the amount of filter cake, cementing material and / or preparation water input into the stirring mechanism is adjusted according to the preset material balance model.

8. The method for co-filling red mud filter press wells according to claim 7, characterized in that, The step of adjusting the amounts of filter cake, gelling material, and / or preparation water input into the stirring mechanism according to a preset material balance model includes: The mass of filter cake, cementitious material, and preparation water required to prepare a unit mass of filling slurry must satisfy the following formula relationship: M filter ×(1-W1) / (M filter +M cement +M water )=C0; M cement / (M filter +M cement +M water )=R; M water =M filter ×W1+△W; where M filter For filter cake quality, M cement For the quality of cementitious materials, M water To determine the water quality, C0 is the target mass concentration of the filling slurry, R is the preset cementitious material ratio, W1 is the real-time moisture content of the filter cake, and ΔW is the mass of water that needs to be added, calculated based on the target mass concentration of the filling slurry and the measured moisture content of the filter cake.

9. A red mud filter press downhole co-filling system, used to implement the red mud filter press downhole co-filling method according to any one of claims 1 to 8, characterized in that, include: A filter press, wherein the filter press is provided with a red mud slurry inlet, a filter cake outlet and a filtrate outlet, and the filter press is used to filter red mud slurry to produce a filter cake with a predetermined moisture content; The filter cake outlet is connected to the top inlet of the well shaft, which is used to allow the filter cake to fall to the bottom of the well shaft under the action of gravity; The wellbore has a filter cake storage bin, and the bottom of the wellbore is connected to the feed inlet of the filter cake storage bin. A downhole water tank, which is connected to the filter press outlet; A stirring mechanism is used to mix and stir the red mud material, cementing material and preparation water input into the stirring mechanism to prepare filling slurry; A filling pump, the inlet of which is connected to the filling slurry outlet B of the stirring mechanism, is used to transport the prepared filling slurry to the downhole filling area; The filter press is located on the surface, while the mixing mechanism and the filling pump are located underground.

10. The red mud pressure filtration downhole co-filling system according to claim 9, characterized in that, It also includes a return air shaft; the return air shaft is connected to the shaft, the return air shaft extends obliquely upward, and the angle between the return air shaft and the shaft is 30~60°.

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