A red mud based backfill slurry preparation system and method

Abstract

The embodiment of the application discloses a red mud-based filling material slurry preparation system and a preparation method, relates to the technical field of mine filling, and is invented to improve the strength of filling body formed by filling material. The preparation system comprises the following: a red mud slurry inlet of a deep-cone thickening unit is connected with an outlet of a pre-homogenization and mixing unit; an inlet of a buffer control unit is connected with a bottom outlet of the deep-cone thickening unit through an underflow pump; a red mud slurry inlet of a stirring and filling unit is connected with an outlet of an online modification unit, and a cementing material inlet is used for feeding cementing material to form filling material slurry; a control unit is used for determining the discharge flow of the deep-cone thickening unit according to the red mud slurry concentration measured by a concentration meter A, the flow measured by a flow meter, the residence time and the target concentration of the red mud slurry in a bottom preset area of the deep-cone thickening unit; and the underflow pump B is used for inputting the red mud slurry in the deep-cone thickening unit into the buffer control unit according to the discharge flow. The application is suitable for filling mines.

Description

Technical Field

[0001] This application relates to the field of waste recycling technology, and in particular to a red mud-based filling slurry preparation system and preparation method. Background Technology

[0002] Red mud is a highly alkaline solid waste generated during alumina production, with a huge annual discharge and insufficient comprehensive utilization rate. Mine backfilling is an important way to dispose of red mud on a large scale, but it faces unresolved technical challenges in engineering practice: Existing technologies attempt to filter red mud slurry into filter cakes, then crush and transport them before preparing the slurry for backfilling. However, red mud filter cakes are highly viscous and plastic, making continuous and stable metering and transportation difficult. Furthermore, they are prone to hardening and caking during transportation and storage, failing to meet the stringent requirements of precise control over slurry flowability and concentration for mine backfilling. The mainstream approach to preparing backfill slurry using red mud in existing technologies involves concentrating the red mud slurry using a deep cone thickener and then mixing it with cementing materials for backfilling. However, red mud has extremely fine particles, high viscosity, and a very slow settling velocity. In conventional thickening processes, if the residence time is insufficient (<4h), the underflow concentration can only reach 50%-55%, far below the 65%±2% process requirement for mine backfilling. While extending the residence time can increase the concentration, this conflicts with the 24-hour continuous discharge capacity requirements of alumina plants. Existing technologies lack precise control over the residence time of red mud to address its ultrafine characteristics, forcing thickeners to compromise between throughput and underflow concentration. This results in high fluctuations in underflow concentration, and unstable red mud slurry directly leads to significant fluctuations in the strength of the backfill material, sometimes even failing to meet standards. Summary of the Invention

[0003] In view of this, embodiments of this application provide a red mud-based filling slurry preparation system and method, which facilitates the improvement of the strength of the filling body formed based on the filling material.

[0004] In a first aspect, embodiments of this application provide a red mud-based filling slurry preparation system, comprising: a pre-homogenization and conditioning unit, wherein the pre-homogenization and conditioning unit is used to stir the incoming red mud slurry; a uniform distributor is provided at the red mud slurry inlet of the pre-homogenization and conditioning unit, and a concentration meter A and a flow meter are provided at the outlet; the concentration meter A and the flow meter are respectively connected to a control unit; a deep cone thickening unit, wherein the red mud slurry inlet of the deep cone thickening unit is connected to the outlet of the pre-homogenization and conditioning unit, and a flocculant inlet is used to add flocculant; a buffer control unit, wherein the inlet of the buffer control unit is connected to the bottom outlet of the deep cone thickening unit via an underflow pump B; and an online modification unit, wherein the red mud slurry inlet of the online modification unit is connected to the outlet of the buffer control unit, and a modifier inlet is used to add modifier. The system comprises: a modifier for solidifying free alkali in the red mud slurry flowing into the online modification unit to obtain modified red mud slurry; a mixing and filling unit, the red mud slurry inlet of which is connected to the outlet of the online modification unit, and a cementitious material inlet for adding cementitious material to mix with the modified red mud slurry to form a filling slurry; a control unit for determining the discharge flow rate of the deep cone thickening unit based on the red mud slurry concentration measured by the concentration meter A, the flow rate measured by the flow meter, a preset residence time, and the target concentration of the red mud slurry in a preset area at the bottom of the deep cone thickening unit; and sending the discharge flow rate to the underflow pump B; the underflow pump B for inputting the red mud slurry in the deep cone thickening unit into the buffer control unit according to the discharge flow rate.

[0005] Optionally, the deep cone thickening unit includes a deep cone thickener; the housing of the deep cone thickener includes a conical bottom and a sidewall disposed on the conical bottom; a mud layer interface meter is provided on the sidewall, the mud layer interface meter is connected to the control unit, and is used to measure the mud layer height corresponding to the sidewall and send the mud layer height to the control unit; the control unit is specifically used to determine the discharge flow rate of the deep cone thickener based on the mud layer height, the radius of the conical bottom, the red mud slurry concentration measured by the concentration meter A, the flow rate measured by the flow meter, the preset residence time, and the target concentration of the red mud slurry in the preset area at the bottom of the deep cone thickener.

[0006] Optionally, the pre-homogenization and slurry conditioning unit is specifically used to input red mud slurry into the deep cone thickening unit at a flow rate Q1 within a preset residence time when the deep cone thickening unit is unloaded; and to continue inputting red mud slurry into the deep cone thickening unit at a flow rate Q1 after the preset residence time is reached; the control unit is also used to send a start signal to the underflow pump B, the start signal including the discharge flow rate; the underflow pump B is specifically used to start operation according to the start signal, so as to input the red mud slurry in the deep cone thickening unit into the buffer control unit according to the discharge flow rate.

[0007] Optionally, the pre-homogenization and slurry conditioning unit is further configured to stop feeding red mud slurry into the deep cone thickening unit when a preset residence time is reached; the control unit is further configured to determine the solid mass contained in the red mud slurry in the deep cone thickening unit based on the flow rate Q1, the preset residence time, and the concentration of the red mud slurry fed into the deep cone thickening unit; and to determine a new discharge flow rate based on the solid mass, the new residence time, and the target concentration.

[0008] Optionally, when the preset residence time is reached, the pre-homogenization and slurry conditioning unit is further configured to continue feeding red mud slurry into the deep cone thickening unit at a flow rate Q2. The control unit is further configured to determine the solid mass contained in the red mud slurry in the deep cone thickening unit based on the flow rate Q1, the preset residence time, and the concentration of the red mud slurry fed into the deep cone thickening unit; and to determine a new discharge flow rate based on the new residence time, the flow rate Q2, the concentration of the red mud slurry fed into the deep cone thickening unit, and the target concentration.

[0009] Optionally, the online modification unit includes: a reactor, the red mud slurry inlet of which is connected to the outlet of the buffer control unit, and the outlet of the reactor connected to the inlet of the stirring and filling unit; a modifier storage tank for storing modifiers; a feeder located between the outlet of the modifier storage tank and the feed port of the reactor; the feeder is connected to the control unit; the control unit is further configured to determine the mass of modifier to be added based on the dry weight of the red mud in the reactor; and the feeder is configured to add modifier to the reactor based on the mass of the modifier.

[0010] Secondly, embodiments of this application provide a method for preparing a filling slurry based on red mud, comprising: uniformly flowing red mud slurry into a pre-homogenization and conditioning unit and stirring the red mud slurry; inputting the red mud slurry in the pre-homogenization and conditioning unit into a deep cone thickening unit, and adding flocculant to the deep cone thickening unit; determining the discharge flow rate of the deep cone thickening unit based on the red mud slurry concentration measured by a concentration meter, the flow rate measured by a flow meter, a preset residence time, and the target concentration of the red mud slurry in a preset area at the bottom of the deep cone thickening unit; the concentration meter and the flow meter are installed in... At the outlet of the pre-homogenization and slurry conditioning unit, the discharge flow rate is sent to the underflow pump located at the outlet of the deep cone thickening unit, so that the underflow pump inputs the red mud slurry in the deep cone thickening unit into the buffer control unit according to the discharge flow rate; through the buffer control unit, the red mud slurry is input into the online modification unit; a modifier is added to the online modification unit to solidify the free alkali in the red mud slurry flowing into the online modification unit to obtain modified red mud slurry; and a cementing material is added to the mixing and filling unit to mix the cementing material and the modified red mud slurry to form a filling slurry.

[0011] The red mud-based filling slurry preparation system and method of this embodiment include a uniform distributor at the red mud slurry inlet of the pre-homogenization and conditioning unit, which ensures that the red mud slurry flows uniformly into the pre-homogenization and conditioning unit. The pre-homogenization and conditioning unit stirs the flowing red mud slurry. The control unit determines the discharge flow rate of the deep cone thickening unit based on the red mud slurry concentration measured by concentration meter A, the flow rate measured by flow meter, the preset residence time, and the target concentration of the red mud slurry in the preset area at the bottom of the deep cone thickening unit. The discharge flow rate is then sent to the underflow pump B. The underflow pump B inputs the red mud slurry in the deep cone thickening unit into the buffer control unit according to the discharge flow rate. In the online modification unit, the free alkali in the flowing red mud slurry is solidified to obtain modified red mud slurry. In the stirring and filling unit, the cementing material and the modified red mud slurry are mixed to form the filling slurry.

[0012] This application has at least the following beneficial effects: 1. It eliminates fluctuations in the concentration and flow rate of the red mud slurry itself, making the flow rate and concentration of the fluid flowing into the deep cone thickening unit more stable, which helps to input red mud slurry with stable concentration downstream; 2. It allows red mud particles to settle sufficiently in the deep cone thickening unit, thereby obtaining red mud slurry with stable concentration; 3. It facilitates obtaining filling slurry with stable concentration, and thus facilitates improving the strength of the filling body formed based on the filling material; 4. It solves the problem of low concentration caused by the excessively fine particles and short residence time in red mud in the prior art. Attached Figure Description

[0013] 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.

[0014] Figure 1 A schematic diagram of the structure of a red mud-based filling slurry preparation system provided in an embodiment of this application; Figure 2 A schematic flowchart of a method for preparing a filling slurry based on red mud according to an embodiment of this application; Figure 3 This is a process control logic diagram for a deep cone dense unit provided in a specific embodiment of this application.

[0015] Explanation of key figure labels: 10-Pre-homogenization and slurry conditioning unit, 20-Deep cone thickening unit, 30-Buffer control unit, 40-Online modification unit, 50-Mixing and filling unit, 60-Control unit, 101-Slurry conditioning tank, 102-Uniform distributor, 103-Double-layer paddle mixer, 104-Concentration meter A, 201-Underflow pump B, 202-Deep cone thickener, 203-Mud interface meter, 204-Flocculant preparation and dosing device, 20 5-Concentration meter C, 301-Underflow buffer tank, 302-Annular pneumatic slurry pipeline, 303-High-pressure gas nozzle, 304-Level gauge, 305-Underflow pump D, 401-Reactor, 402-Modifier storage tank, 403-Feeder, 404-pH meter, 501-First stage mixing tank, 502-Water replenishment tank, 503-Cementitious material storage tank, 504-Second stage mixing tank, 505-Concentration meter E. Detailed Implementation

[0016] The embodiments of this application will now be described in detail with reference to the accompanying drawings. It should be understood that the described embodiments are merely some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0017] To enable those skilled in the art to better understand the technical concept, implementation scheme and beneficial effects of the embodiments of this application, detailed descriptions are provided below through specific embodiments.

[0018] The embodiments of this application, through the four-in-one technical concept of "deep cone thickening time process optimization (based on the operation parameter control of standard deep cone thickening equipment), front-end buffer control (supply and demand matching of underflow buffer tank 301 + frequency converter pump), back-end output stability control (precise adjustment of concentration through two-stage stirring), and online in-situ chemical modification (desulfurized gypsum-fly ash composite activator)," combined with intelligent coordinated control based on multi-parameter online detection, realize the continuous and stable treatment of the entire process of red mud mine backfilling.

[0019] Example 1 Figure 1 This is a schematic diagram of the structure of a red mud-based filling slurry preparation system provided in an embodiment of this application, as shown below. Figure 1As shown, the red mud-based filling slurry preparation system of this embodiment may include: a pre-homogenization and slurry conditioning unit 10, a deep cone thickening unit 20, a buffer control unit 30, an online modification unit 40, a stirring and filling unit 50, and a control unit 60; wherein, the pre-homogenization and slurry conditioning unit 10 is used to stir the flowing red mud slurry; a uniform distributor 102 is provided at the red mud slurry inlet of the pre-homogenization and slurry conditioning unit 10, and a concentration meter A104 and a flow meter are provided at the outlet; the concentration meter A104 and the flow meter are respectively connected to the control unit 60; the red mud slurry inlet of the deep cone thickening unit 20 is connected to the outlet of the pre-homogenization and slurry conditioning unit 10, and the flocculant inlet is used to add flocculant; the inlet of the buffer control unit 30 is connected to the bottom outlet of the deep cone thickening unit 20 through a bottom flow pump B201; the red mud slurry inlet of the online modification unit 40 is connected to the outlet of the buffer control unit 30. The inlet of the online modification unit 40 is connected to the outlet of the online modification unit 40. The modifier inlet is used to add modifier, which is used to solidify the free alkali in the red mud slurry flowing into the online modification unit 40 to obtain modified red mud slurry. The red mud slurry inlet of the stirring and filling unit 50 is connected to the outlet of the online modification unit 40. The cementitious material inlet is used to add cementitious material to mix the cementitious material and the modified red mud slurry to form a filling slurry. The control unit 60 is used to determine the discharge flow rate of the deep cone thickening unit 20 based on the red mud slurry concentration measured by the concentration meter A104, the flow rate measured by the flow meter, the preset residence time, and the target concentration of the red mud slurry in the preset area at the bottom of the deep cone thickening unit 20. The discharge flow rate is sent to the underflow pump B201. The underflow pump B201 is used to input the red mud slurry in the deep cone thickening unit 20 into the buffer control unit 30 according to the discharge flow rate.

[0020] The main chemical components of red mud include SiO2 (10%-20%), Fe2O3 (30%-50%), Al2O3 (10%-25%), CaO (2%-10%), Na2O (2%-10%), and TiO2 (3%-8%), with a pH value typically between 10 and 13. It is usually discharged from alumina plants in the form of red mud slurry.

[0021] Red mud has a fine particle size (d 50 Due to its characteristics of being typically <20μm and having high viscosity, its sedimentation and concentration behavior is fundamentally different from that of conventional tailings.

[0022] The red mud slurry inlet of the pre-homogenization and slurry preparation unit 10 is used to input red mud slurry; the outlet of the pre-homogenization and slurry preparation unit 10 is connected to the red mud slurry inlet of the deep cone thickening unit 20. The uniform distributor 102 can distribute the input red mud slurry into the pre-homogenization and slurry preparation unit 10 relatively evenly. The uniform distributor 102 can be in the form of a comb-like structure, and the red mud will flow in from the gaps between the comb teeth.

[0023] The pre-homogenization and slurry preparation unit 10 includes a slurry preparation tank 101, which receives red mud slurry through a feed pipe. A uniform distributor 102 is provided at the end of the feed pipe to ensure that the red mud slurry is evenly distributed along the cross-section of the tank and to avoid local accumulation. A double-layer paddle agitator 103 is installed inside the tank, with a stirring linear velocity of 0.5-1.5 m / s to ensure uniform concentration of the red mud slurry.

[0024] The pre-homogenization and slurry conditioning unit 10 in this embodiment can eliminate the unevenness of concentration and flow rate fluctuations in the red mud slurry discharged from the alumina plant, providing homogenized raw materials for subsequent treatment and serving as a front-end guarantee for achieving stable operation throughout the entire process.

[0025] The concentration meter A104 at the outlet of the pre-homogenization and slurry conditioning unit 10 is used to measure the concentration of the red mud slurry flowing out of the pre-homogenization and slurry conditioning unit 10, and the flow meter at the outlet is used to measure the flow rate of the red mud slurry flowing out of the pre-homogenization and slurry conditioning unit 10.

[0026] The concentration meter A104 and the flow meter can transmit analog signals, such as 4-20mA analog signals, to the control unit 60.

[0027] The deep cone thickening unit 20 can deeply concentrate low-concentration red mud slurry and output a high-concentration underflow (red mud slurry in a preset area at the bottom) from the bottom of the deep cone thickening unit 20. In a specific example, the deep cone thickening unit 20 includes a deep cone thickener 202, which includes a shell and a rake frame. The shell can be a welded carbon steel structure lined with an epoxy anti-corrosion coating, with a diameter of 6-15m (preferably 10m), a straight section height of 6-12m (preferably 8m), and a cone angle of 55°-65° (preferably 60°). The shell forms a receiving cavity with a total volume of 300-1500m³ (preferably 800m³). The rake frame is driven by a hydraulic drive device at a speed of 0.02-0.1r / min (preferably 0.05r / min), and the rake frame torque is monitored in real time by a torque sensor.

[0028] The deep cone thickener 202 includes an automatic rake lifting protection system. When the rake frame torque exceeds 80% of the rated torque, the PLC controller sends a control signal to drive the hydraulic cylinder to lift the main rake. When the torque returns to below 50% of the rated torque, the rake frame slowly resets.

[0029] To improve the settling velocity of the red mud slurry, the deep cone thickening unit 20 is provided with a flocculant inlet for adding flocculant. Adding flocculant can cause the red mud slurry to form flocs and settle downwards at a certain speed, thereby increasing the concentration of red mud slurry (also known as underflow) in the deep cone thickening unit 20 near the bottom of the preset range. During use, the red mud slurry in the preset range of the bottom flows out from the outlet set at the bottom of the deep cone thickening unit 20 and is supplied to the downstream treatment unit for processing to prepare filling slurry.

[0030] like Figure 1 In the illustrated embodiment, the deep cone thickening unit 20, in addition to the deep cone thickener 202, may also include a flocculant preparation and dosing device 204. The feed pipe of the deep cone thickener 202 is equipped with a flocculant dosing port, connected to the flocculant preparation and dosing device 204, for adding flocculant. The flocculant is anionic polyacrylamide (APAM), with a molecular weight of 12-18 million Da, and a concentration of 0.1%-0.5%. The flocculant dosage is automatically adjusted according to the red mud slurry concentration and feed flow rate (typical dosing range 10-50 g / t dry red mud), and automatically adjusted according to the dry weight change (Qin×Cin). The flocculant is fully mixed with the red mud slurry in the feed pipe through multi-point injection.

[0031] In this embodiment, the coordinated control of flocculant addition and preset residence time ensures both concentration effect and processing efficiency.

[0032] It is understood that the preset dwell time in this application is the time spent in the deep cone dense unit 20.

[0033] The underflow pump B201 enables the red mud slurry within the preset bottom range of the deep cone thickening unit 20 to flow out of the outlet of the deep cone thickening unit 20 and into the buffer control unit 30. The underflow pump B201 is a variable frequency underflow pump.

[0034] The cache control unit 30 can be located below the bottom of the deep cone dense unit 20.

[0035] When the mine filling system operates intermittently or not at all, the deep cone thickening unit 20 needs to be frequently started and stopped. However, upstream plants, such as alumina plants, have a continuous need to supply red mud slurry (material) to the deep cone thickening unit 20. To resolve the supply and demand timing contradiction between continuous upstream supply and intermittent mine filling, the preparation system in this embodiment includes a buffer control unit 30. When the upstream supply is continuous and the mine filling system is operating continuously, the red mud slurry flowing out of the outlet of the deep cone thickening unit 20 flows downstream through the buffer control unit 30 to prepare filling slurry. When the upstream supply is continuous and the mine filling system operates intermittently or not at all, the buffer control unit 30 is used to temporarily store a certain amount of red mud slurry flowing out of the deep cone thickening unit 20, thereby not affecting the continuous upstream supply and avoiding frequent start and stop of the deep cone thickening unit 20.

[0036] like Figure 1 In the embodiment shown, the buffer control unit 30 may include an underflow buffer tank 301, which is a vertical cylindrical carbon steel storage tank lined with a wear-resistant and corrosion-resistant coating, with a volume of 100-800m³ (selected as 200m³), capable of storing 2-4 hours of underflow output, providing sufficient buffer space for supply and demand fluctuations.

[0037] In some examples, an annular pneumatic slurry-making pipeline 302 is installed at the bottom of the bottom buffer tank 301. Several high-pressure gas nozzles 303 are evenly arranged along the inner wall of the conical section at the bottom of the tank, with a nozzle spacing of 0.5-1.0m. Compressed air (pressure 0.4-0.8MPa, preferably 0.6MPa) is used to pneumatically stir and slurry the sediment in the tank, keeping the slurry uniform and preventing stratification, clumping, and blockage. The slurry-making gas source is connected to the existing compressed air pipeline network of the mine backfilling station, and the on / off state is controlled by a solenoid valve. Slurry making is started before backfilling operations to ensure that the concentration of the discharged slurry is uniform.

[0038] The buffer control unit 30 has an outlet at its bottom to discharge the red mud slurry (also known as underflow) with a certain concentration at the bottom of the buffer control unit 30. The buffer control unit 30 then transports the bottom red mud slurry to the online modification unit 40 through a DN150 wear-resistant pipe.

[0039] The online modification unit 40 can be a static tubular mixing reactor. The diameter of the tubular mixing reactor can be between DN200 and DN400, preferably DN300, and the length can be between 6 and 15m, preferably 10m. The tubular mixing reactor has built-in static mixing elements with a length-to-diameter ratio between 1.5 and 2.0. Multiple mixing elements, such as 8 to 12 mixing elements, are set inside the tubular mixing reactor.

[0040] In online modification unit 40, the modifier is mixed with the red mud slurry. The modifier can solidify the free alkali in the red mud slurry flowing into online modification unit 40, resulting in modified red mud slurry. This avoids the strong alkalinity of the red mud causing a later-stage efflorescence strength reduction in the filling body, i.e., free Na+. + During the hydration process of the filling material, Na2CO3 white crystals migrate to the surface and form, resulting in surface powdering and a loose internal structure.

[0041] In some examples, the modifier is a composite activator composed of desulfurized gypsum and fly ash mixed at a mass ratio of 1:1.5~2.5 (preferably 1:2.0), and the dosage is 8%-12% (preferably 10%) of the dry weight of the red mud. In the online modification unit 40, the free alkali in the red mud reacts with CaSO4·2H2O in the desulfurized gypsum in the following chemical reaction: Pathway 1: Erythrite formation reaction (NaOH fixed path): Ca² provided by desulfurized gypsum + and SO4² - The red mud reacts with Al2O3 and NaOH in the presence of free water to form insoluble ettringite (3CaO·Al2O3·3CaSO4·32H2O), releasing free Na... + Fixed within the ettringite crystal structure: 6Ca² + +2Al(OH)4- +3SO4² - +26H2O→Ca6Al2(SO4)3(OH) 12 ·26H2O Pathway: Sodium carbonate conversion reaction (Na2CO3 fixed path): Na2CO3 in red mud undergoes a double decomposition reaction with CaSO4·2H2O: Na2CO3+CaSO4·2H2O→CaCO3↓+Na2SO4+2H2O The generated sparingly soluble CaCO3 precipitate precipitates out of the solution, while Na2SO4 is either adsorbed and fixed by CSH gelation or solidified with the mineralization of the filling material during subsequent hydration reactions.

[0042] Pathway 3: Formation of hydrotalcite-like phase (MgO synergistic fixation pathway): Bayer process red mud typically contains 2%-5% MgO. Under alkaline conditions, Mg²⁺… + With CO3² - and OH - The reaction produces a hydrotalcite-like phase (Mg6Al2(OH)). 16 CO3·4H2O) further adsorbs and fixes carbonate ions.

[0043] The three reaction pathways described above work synergistically to transform the free alkalis (NaOH, Na2CO3) in red mud into insoluble or sparingly soluble mineral phases (ettringite, CaCO3, and hydrotalcite-like phases), achieving mineralogical solidification of the alkalis. Simultaneously, the generated ettringite, along with the active components (active SiO2, Al2O3) in desulfurized gypsum and fly ash, synergistically stimulate the latent pozzolanic activity of the red mud, promoting the formation of hydration products.

[0044] Alkali fixation rate (%) = (1 - soluble Na₂O content in modified red mud / soluble Na₂O content in unmodified red mud) × 100%, where the soluble Na₂O content is determined by flame photometry according to GB / T 176-2017 "Cement Chemical Analysis Methods". Based on this formula, the alkali fixation rate of the modified red mud slurry can be determined.

[0045] The online modification unit 40 in this embodiment can achieve in-situ chemical fixation and potential activation of free alkali in red mud. It uses all industrial solid waste as the modification raw material, realizing "waste treatment with waste". At the same time, it activates the red mud to reduce the amount of cementitious materials and lower the treatment cost. The series coupling of online modification and thickening-buffering process realizes continuous treatment from dewatering to modification.

[0046] In the mixing and filling unit 50, the cementitious material and red mud slurry are fully mixed to form a filling slurry, which is used to fill the mine and forms a filling body after solidification.

[0047] The mixing and filling unit 50 includes a mixing tank, which employs a twin-shaft forced mixer to ensure thorough and uniform mixing of the cementitious material and the red mud slurry. In a specific example, the mixing tank volume is 30-80 m³, preferably 50 m³, the mixer power is 11-30 kW, and the mixing time is 3-5 min.

[0048] Modified red mud slurry is mixed with a cementitious material to prepare a filling slurry that meets the requirements for strength and fluidity. The cementitious material can be an all-solid waste cementitious material or cement.

[0049] The longer the red mud slurry flowing into the deep cone thickening unit 20 stays in the deep cone thickening unit 20, the higher the concentration of the red mud slurry in the bottom preset area of ​​the deep cone thickening unit 20 (underflow concentration). The shorter the residence time, the lower the underflow concentration. In other words, in order to achieve the target underflow concentration, the red mud slurry flowing into the deep cone thickening unit 20 must stay in the deep cone thickening unit 20 for a certain period of time. The larger the discharge flow rate of the deep cone thickening unit 20, the shorter the time; the smaller the discharge flow rate of the deep cone thickening unit 20, the longer the time. Therefore, the discharge flow rate of the deep cone thickening unit 20 affects the time, and thus affects the concentration of the red mud slurry in the bottom preset area of ​​the deep cone thickening unit 20.

[0050] In this embodiment, the control unit 60 determines the discharge flow rate of the deep cone thickening unit 20. Thus, the deep cone thickening unit 20 discharges at a predetermined amount, which facilitates the concentration of red mud slurry in the preset area at the bottom of the deep cone thickening unit to reach the target concentration. This results in the output of red mud slurry with a stable concentration to the unit downstream of the deep cone thickening unit 20 in the preparation system, which helps to improve the strength of the filling body formed based on the filling material. In this embodiment, the deep cone thickening unit 20 is precisely controlled by time to ensure that the red mud particles settle sufficiently and the underflow concentration is stable and meets the standard.

[0051] In some cases, the preset residence time is less than or equal to the maximum time that the red mud is in the deep cone thickener 202. The maximum time can be determined based on the effective settling volume of the deep cone thickener 20, the volumetric flow rate of the red mud slurry feed, the concentration of the red mud slurry flowing into the deep cone thickener 20, and the target concentration flowing out of the deep cone thickener 20.

[0052] Specifically, the maximum time can be determined using the following formula: T max =V eff / (Q) in M1 / M2) Wherein, Veff is the effective settling volume (m³) of the deep cone thickening unit 20, Qin is the red mud slurry feed volumetric flow rate (m³ / h), M1 is the solids content per unit volume of the red mud slurry flowing into the deep cone thickening unit 20, which can be determined based on the concentration and true density of the red mud slurry flowing into the deep cone thickening unit 20; M2 is the solids content per unit volume of the red mud slurry flowing out of the deep cone thickening unit 20, which can be determined based on the target concentration and true density of the red mud slurry in the bottom preset area within the deep cone thickening unit 20. The maximum time can be the maximum residence time in the deep cone thickening unit 20.

[0053] In a specific example, with a feed concentration of 20% and a red mud true density of 2.8, the solids content per unit volume M1 is approximately 0.23t. When the underflow concentration target is 65%, the red mud true density is 2.8, and the solids content per unit volume M2 is approximately 1.12t. Assuming Qin = 200 m³ / h and the volume of the deep cone thickener 202 is 800 m³, the maximum time is 19.48 h.

[0054] The preset stay time can be any value less than or equal to 19.48 hours.

[0055] In some examples, the control unit 60 can dynamically adjust the time based on the concentration of red mud slurry flowing into the deep cone thickening unit 20. For instance, when the Al2O3 content in the red mud slurry increases (indicating increased aluminum mineral content and viscosity), the control unit 60 automatically shortens the time to ensure slurry fluidity; when the red mud particle size is coarser (d... 50 For samples >30μm, the processing time should be shortened appropriately to improve processing efficiency.

[0056] In this embodiment, a uniform distributor 102 is provided at the red mud slurry inlet of the pre-homogenization and conditioning unit 10, so that the red mud slurry flows into the pre-homogenization and conditioning unit 10 evenly. The pre-homogenization and conditioning unit 10 stirs the flowing red mud slurry. The control unit 60 determines the discharge flow rate of the deep cone thickening unit 20 based on the red mud slurry concentration measured by the concentration meter A104 at the outlet of the pre-homogenization and conditioning unit 10, the flow rate measured by the flow meter at the outlet of the pre-homogenization and conditioning unit 10, the preset residence time, and the target concentration of the red mud slurry in the preset area at the bottom of the deep cone thickening unit 20. The discharge flow rate is then sent to the underflow pump B201. The underflow pump B201 inputs the red mud slurry in the deep cone thickening unit 20 into the buffer control unit 30 according to the discharge flow rate. In the online modification unit 40, the free alkali in the flowing red mud slurry is solidified to obtain modified red mud slurry. In the stirring and filling unit 50, the cementitious material and the modified red mud slurry are mixed to form a filling slurry. Because the uniform distributor 102 installed at the inlet of the pre-homogenization and slurry conditioning unit 10 ensures that the red mud slurry flows evenly along the cross-section of the tank and is stirred, fluctuations in the concentration and flow rate of the red mud slurry can be eliminated, ensuring that the concentration of the red mud slurry entering the deep cone thickening unit 20 is uniform. On this basis, the concentration meter A104 and flow meter at the outlet of the pre-homogenization and slurry conditioning unit 10 can detect the concentration and flow rate of the outflowing red mud slurry, which can truly reflect the state of the red mud slurry flowing into the deep cone thickening unit. Based on this, the control unit 60 calculates and controls the underflow discharge flow rate of the deep cone thickening unit 20 in conjunction with the preset residence time and the underflow target concentration, so that the red mud particles can be fully settled in the deep cone thickening unit 20, thereby obtaining red mud slurry with stable concentration. Furthermore, the red mud slurry with relatively stable concentration can flow to downstream units such as the buffer control unit 30, ultimately facilitating the obtaining of filling slurry with stable concentration, and thus facilitating the improvement of the strength of the filling body formed based on the filling material.

[0057] When the filling slurry prepared using the filling slurry preparation system of this embodiment is used to fill the mine, the resulting filling body has a compressive strength of more than 2.5 MPa.

[0058] Example 2 like Figure 1 In the illustrated embodiment, the deep cone thickening unit 20 may include a deep cone thickener 202; the housing of the deep cone thickener 202 includes a conical bottom and a sidewall disposed on the conical bottom; a mud layer interface meter 203 is disposed on the sidewall, the mud layer interface meter 203 is connected to the control unit 60, and is used to measure the mud layer height corresponding to the sidewall and send the mud layer height to the control unit 60; the control unit 60 is specifically used to determine the discharge flow rate of the deep cone thickener 202 based on the mud layer height, the size of the deep cone thickening unit 20, the flow rate and concentration of the red mud slurry flowing into the deep cone thickening unit 20, the preset residence time, and the target concentration of the red mud slurry in the preset area at the bottom of the deep cone thickener 202.

[0059] The mud layer interface meter 203 can specifically be an ultrasonic mud layer interface meter 203; 3-5 ultrasonic mud layer interface meters 203 are installed on the side wall from top to bottom at intervals of 1.5-2.0m, with a measurement accuracy of ±10mm. In this embodiment, the side wall is circumferentially closed. In a specific embodiment, the side wall can be a cylinder with a through hole, the diameter of which is equal to the diameter of the corresponding bottom surface of the cone.

[0060] In a specific example, the underflow discharge of the deep cone thickener 202 is controlled by the underflow pump B201, and the discharge flow rate is determined according to the following formula: Q out =(V c / M1+Q in1 ×C in1 ×T) / T / M1 V c Let M1 be the volume of the settling fluid in the deep cone dense unit 20, and Q be the solids content per unit volume of the settling fluid (M1 is determined according to the target concentration). in1 C is the volumetric flow rate (feed volumetric flow rate) of the red mud slurry flowing into the deep cone thickener 202. in1 The concentration of the red mud slurry flowing into the deep cone thickener 202 is T, which is the preset residence time.

[0061] Among them, V c =(H slurry +r / 1.73 / 3)×πr 2 H slurry denoted as ρ, where ρ is the height of the mud layer corresponding to the sidewall, and r is the radius corresponding to the sidewall or the radius of the ground surface at the conical bottom.

[0062] The B201 underflow pump can be a variable frequency underflow pump, with the flow rate being steplessly adjustable within the range of 0-200 m³ / h.

[0063] This embodiment is adapted to the case where the deep cone thickener 202 is loaded (with red mud slurry already stored), but the volume of the red mud slurry is unknown.

[0064] A mud layer interface meter 203 is installed on the side wall of the deep cone thickener, which can accurately determine the mud layer height. This allows the control unit 60 to accurately calculate the discharge flow rate of the deep cone thickener 202 based on the mud layer height measured by the mud layer interface meter 203, thereby enabling the delivery of red mud slurry with a relatively stable concentration to the downstream unit.

[0065] Example 3 When the deep cone thickening unit 20 is unloaded, i.e., when there is no red mud slurry in the deep cone thickening unit 20, in order to ensure that the residence time of the red mud slurry in the deep cone thickening unit 20 is a preset time, red mud slurry can be injected into the deep cone thickening unit 20 at a certain flow rate for a preset residence time. During this process, the red mud slurry in the deep cone thickening unit 20 is not discharged. After continuously injecting red mud slurry for the preset residence time, red mud slurry is still injected into the deep cone thickening unit 20, and the red mud slurry is discharged from the deep cone thickening unit 20 at a calculated discharge flow rate. In this way, the time of the red mud slurry flowing into the deep cone thickening unit 20 can be maintained at the preset residence time, thereby stabilizing the underflow concentration of the deep cone thickening unit 20. Correspondingly, in some embodiments, the pre-homogenization and slurry conditioning unit 10 is specifically used to input red mud slurry into the deep cone thickening unit 20 at a flow rate Q1 within a preset residence time when the deep cone thickening unit 20 is unloaded; and to continue inputting red mud slurry into the deep cone thickening unit 20 at a flow rate Q1 when the preset residence time is reached; the control unit 60 is also used to send a start signal to the underflow pump B201, the start signal including the discharge flow rate; the underflow pump B201 is specifically used to start running according to the start signal, so as to input the red mud slurry in the deep cone thickening unit 20 into the buffer control unit 30 according to the discharge flow rate.

[0066] When the feed concentration is 20% and the true density of red mud is 2.8, the solids content per unit volume M1 is approximately 0.23t. Taking a target underflow concentration of 65% and a true density of red mud of 2.8, the solids content per unit volume M2 is approximately 1.12t as an example. Based on material balance, the theoretical optimal time is 8-12 hours. Taking a time of 10 hours as an example, assuming Qin = 200 m³ / h, and the volume of the deep cone thickener 202 is 800 m³, if the deep cone thickener 202 stores material for 10 hours, then the material's time is 10 hours. With Qin at 200 m³ / h, the solids content is 200 m³ / h. 0.23t = 46t. To meet the requirement of 10h, the discharge flow rate is 46t / 1.12t = 41.07m³ / h. Therefore, by discharging the underflow at a discharge flow rate of 41.07m³ / h, all materials can be maintained for 10h from feeding to discharging.

[0067] In this embodiment, under the scenario where the deep cone thickening unit 20 is unloaded, the deep cone thickening unit 20 can discharge red mud slurry with a stable concentration.

[0068] Example 4 If the preset residence time is reached and adjustment is required, the discharge flow rate needs to be increased or decreased. In some examples, the pre-homogenization and slurry conditioning unit 10 is also used to stop feeding red mud slurry into the deep cone thickening unit 20 when the preset residence time is reached. The control unit 60 is also used to determine the solid mass of the red mud slurry in the deep cone thickening unit 20 based on the flow rate Q1, the preset residence time, and the concentration of the red mud slurry fed into the deep cone thickening unit 20; and to determine a new discharge flow rate based on the solid mass, the new residence time, and the target concentration.

[0069] Taking the aforementioned specific example, if it is necessary to adjust the time from 10 hours to 8 hours, that is, to reduce the actual time of the red mud slurry, then the discharge flow rate needs to be increased, and the discharge flow rate Q... out =46t 10h / 8h / 1.12t.

[0070] When the preset residence time is reached, the pre-homogenization and slurry conditioning unit 10 continues to input red mud slurry into the deep cone thickening unit 20 at a flow rate, and the time needs to be adjusted, such as from 10h to 8h, which reduces the actual time of the red mud slurry. In response to this situation, in one embodiment of this application, when the preset residence time is reached, the pre-homogenization and slurry conditioning unit 10 is further configured to continue inputting red mud slurry into the deep cone thickening unit 20 at a flow rate Q2. The control unit 60 is further configured to determine the solid mass contained in the red mud slurry in the deep cone thickening unit 20 based on the flow rate Q1, the preset residence time, and the concentration of the red mud slurry input into the deep cone thickening unit 20; and to determine a new discharge flow rate based on the new residence time, the flow rate Q2, the concentration of the red mud slurry input into the deep cone thickening unit 20, and the target concentration.

[0071] If feeding continues during the discharge process, then Q out =(46t 10h+ (Q) in C in 8h)) / 8h / 1.12t。

[0072] In this embodiment, when the residence time needs to be adjusted, the deep cone thickening unit 20 can discharge red mud slurry with a stable concentration.

[0073] Example 5 To maintain a dynamic balance between supply and demand, in one embodiment of this application, the outlet of the buffer control unit 30 is connected to the red mud slurry inlet of the online modification unit 40 via an underflow pump D305; the underflow pump D305 is connected to the control unit 60; a level gauge 304 is installed on the side wall of the buffer control unit 30, which is used to measure the liquid level of the red mud slurry in the buffer control unit 30; the level gauge 304 is connected to the control unit 60; the filling slurry is used to supply the mine filling system; the control unit 60 is also used to determine the flow rate entering the deep cone thickening unit 20 and / or the frequency of the underflow pump D305 based on the operating status of the mine filling system and the value measured by the level gauge 304.

[0074] The D305 underflow pump is a hydraulic diaphragm pump or a hose pump, with a flow rate of 0-200 m³ / h (preferably 80 m³ / h) that is steplessly adjustable, and an outlet pressure of 0.3-1.0 MPa.

[0075] Three radio frequency admittance level gauges 304 are installed on the side wall of the buffer control unit 30 from top to bottom, with a measurement accuracy of ±5mm, corresponding to 90%, 50%, and 15% of the capacity of the buffer control unit 30, respectively.

[0076] When the mine filling system is operating normally, the buffer control unit 30 feeds red mud slurry to the downstream online modification unit 40 through the underflow pump D305. The deep cone thickening unit 20 simultaneously feeds red mud slurry to the buffer control unit 30. The buffer control unit 30 maintains the liquid level in the middle range of 50%±20%, thereby maintaining a dynamic balance between supply and demand.

[0077] When mine filling is interrupted (e.g., during maintenance or shift handover), the deep cone thickening unit 20 continues to supply material to the buffer control unit 30 without interruption. At this time, the buffer control unit 30 acts as an accumulator, and the liquid level gradually rises. When the high-level gauge 304 (90% liquid level) is triggered, the control unit 60 automatically reduces the frequency of the feed pump in the deep cone thickening unit 20 (reducing the feed flow rate to 50%-70% of the normal value), slowing the rise in the liquid level in the buffer control unit 30, while maintaining the time spent in the deep cone thickening unit 20 within the optimized range.

[0078] When the mine backfilling system resumes operation, the liquid level in the buffer control unit 30 is at a high level (e.g., 70%-90%). The control unit 60 initiates a rapid discharge procedure: increasing the frequency of the underflow pump D305 to 120% of its rated value (within the pump's allowable operating range), while simultaneously gradually increasing the feed flow rate of the deep cone thickening unit 20 to its normal value, restoring the system to normal feeding mode within 15-30 minutes. Before the backfilling operation, the pneumatic slurry mixing system in the buffer control unit 30 is started in advance to fully stir the slurry within the buffer control unit 30, ensuring uniform discharge concentration.

[0079] When the low-level level gauge 304 (e.g., 15% liquid level) is triggered, the frequency of the underflow pump D305 is reduced or the supply to the downstream online modification unit 40 is suspended. At the same time, the deep cone thickening unit 20 is kept in normal feeding and discharging, so that the liquid level of the buffer control unit 30 rises. This can prevent the buffer control unit 30 from running dry and causing the downstream online modification unit 40 to run out of material.

[0080] This embodiment resolves the timing conflict between continuous feeding in alumina plants and intermittent filling in mines. It combines supply and demand buffering with time optimization of the deep cone thickening unit 20. When the mine stops filling, the deep cone thickening unit 20 does not stop. Instead, it extends the time during the energy storage period of the buffer control unit 30 to improve the thickening effect, achieving the process effect of "trading time for quality". In addition, it uses nozzle pneumatic slurry making instead of traditional stirring power. Slurry making is carried out before filling, which is simple in structure, low in energy consumption, easy to maintain, and avoids the potential damage to the rheological properties of the slurry caused by stirring.

[0081] Example 6 In some embodiments, the online modification unit 40 includes: a reactor 401, a modifier storage tank 402, and a feeder 403; wherein the red mud slurry inlet of the reactor 401 is connected to the outlet of the buffer control unit 30, and the outlet of the reactor 401 is connected to the inlet of the stirring and filling unit 50; the modifier storage tank 402 is used to store the modifier; the feeder 403 is located between the outlet of the modifier storage tank 402 and the feed port of the reactor 401; the feeder 403 is connected to the control unit 60; the control unit 60 is also used to determine the mass of modifier to be added based on the dry red mud mass in the reactor 401; the feeder 403 is used to add the modifier to the reactor 401 based on the mass of the modifier.

[0082] The modifier storage silo 402 can be a cone-bottom vertical carbon steel storage tank. In a specific example, the volume is 10-30m³. The bottom outlet is connected to a screw metering feeder 403 with a feeding capacity of 0-20t / h (preferably 8t / h). Accurate metering is achieved through frequency conversion speed regulation.

[0083] The outlet of the online modification unit 40 is equipped with a variable frequency discharge pump, which can pump the red mud slurry in the online modification unit 40 into the mixing and filling unit 50.

[0084] Furthermore, a pH meter 404 is provided at the outlet of the online modification unit 40 to measure the concentration of the red mud slurry flowing out of the online modification unit 40; the pH meter 404 is connected to the control unit 60; the control unit 60 determines the quality of the new modifier based on the value measured by the pH meter 404.

[0085] The pH meter 404 has a range of 0-14 and an accuracy of ±0.02, and is used for real-time monitoring of the modification effect and feedback control of the modifier dosage. Specifically, when the pH of the red mud slurry flowing out of the online modification unit 40 is >10.5, the modifier dosage is automatically increased; when the pH of the red mud slurry flowing out of the outlet is <9.0, the dosage is automatically decreased, stabilizing the outlet pH within the range of 9.0-10.0. The amount of modifier added can be determined based on the actual pH value and the target pH value.

[0086] The online modification unit 40 in this embodiment can achieve in-situ chemical fixation and potential activation of free alkali in red mud. It uses all industrial solid waste as the modification raw material, realizing "waste treatment with waste". At the same time, it activates the red mud to reduce the amount of cementitious materials and lower the treatment cost. The series coupling of online modification and thickening-buffering process realizes continuous treatment from dewatering to modification.

[0087] The concentration of red mud slurry discharged from the outlet of the deep cone thickening unit 20 is relatively stable. After being processed by the buffer control unit 30 and the online modification unit 40, if the concentration changes significantly, it will lead to insufficient strength of the filling material. In the prior art, changes in flow rate will simultaneously cause changes in red mud slurry concentration, resulting in the two variables being coupled and causing a decline in quality control. To overcome this drawback, see [reference needed]. Figure 1 In one embodiment of this application, a flow meter is provided at the outlet of the buffer control unit 30, and a concentration meter C205 is provided at the outlet of the deep cone thickening unit 20; the flow meter and the concentration meter C205 are respectively connected to the control unit 60; the stirring and filling unit 50 includes: a first-stage stirring tank 501, the red mud slurry inlet of the first-stage stirring tank 501 is connected to the outlet of the online modification unit 40; a water replenishment tank 502, the water replenishment tank 502 is connected to the water replenishment port of the first-stage stirring tank 501 through a regulating valve; the regulating valve is connected to the control unit 60. 0 is connected; cementitious material storage silo 503 is used to store cementitious materials; second-stage mixing tank 504 is connected to the red mud slurry inlet of the first-stage mixing tank 501 and the outlet of the first-stage mixing tank 501, and the cementitious material inlet is connected to the outlet of the cementitious material storage silo 503; control unit 60 is also used to determine the amount of water replenishment based on the flow rate measured by the flow meter at the outlet of the buffer control unit 30 and the concentration measured by the concentration meter C205; regulating valve is used to inject water into the first-stage mixing tank 501 according to the amount of water replenishment.

[0088] The flow meter at the outlet of the buffer control unit 30 is used to measure the fluid flow rate of the red mud slurry flowing out of the buffer control unit 30.

[0089] The concentration meter C205, located at the outlet of the deep cone thickening unit 20, can be a nuclear concentration meter, used to measure the concentration of red mud slurry flowing out of the outlet of the deep cone thickening unit 20.

[0090] The first-stage mixing tank 501 receives the modified red mud slurry output from the online modification unit 40.

[0091] An electromagnetic flow meter can also be installed between the water replenishment tank 502 and the water replenishment port of the first-stage mixing tank 501 via a regulating valve to precisely control the amount of water replenished.

[0092] The control unit 60 determines the makeup water volume based on the flow rate measured by the flow meter and the concentration measured by the concentration meter C205. Specifically, the makeup water volume can be determined using the following formula: Q water =Q in2 ×(C in2 / C target -1)+K d ×dQ in2 / dt Among them, Q in2 C is the real-time flow rate of red mud slurry flowing out of the buffer control unit 30. in2 C represents the concentration of the red mud slurry flowing from the outlet of the deep cone thickening unit 20. target K is the concentration setpoint. d dQ is the decoupling coefficient for the rate of change of flow (calibrated through system identification, typical value 0.8-1.2). in2 / dt represents the rate of change of flow rate.

[0093] A concentration meter E505 can be installed at the outlet of the first-stage mixing tank 501 to monitor the real-time concentration of the output red mud slurry. Furthermore, PID control can be performed based on the real-time concentration detected by the concentration meter E505 to correct the water replenishment amount. If the actual concentration is greater than the expected concentration, the water replenishment amount is increased, thereby eliminating errors and disturbances. In this embodiment, the concentration control of the red mud slurry in the first-stage mixing tank 501 adopts a feedforward-feedback composite control strategy. When a change in the red mud slurry flow rate is detected, the regulating valve synchronously acts to compensate for the corresponding water volume change, effectively eliminating errors and disturbances and ensuring the consistency of slurry quality in downstream filling operations.

[0094] The filling slurry in the second-stage mixing tank 504 is pumped to the mined-out area underground through the filling pipeline for filling operations. The filling pipeline system is a well-known technology in the field of mine filling and will not be described in detail here.

[0095] The cementitious material storage silo 503 can be a red mud-based composite cementitious material storage silo, connected to the cementitious material inlet of the second mixing tank.

[0096] In one embodiment, the red mud-based composite cementitious material is composed of the following components by mass percentage: 40%-50% slag powder (S95 grade or above), 15%-20% red mud (dry basis), 10%-15% desulfurized gypsum, 5%-15% fly ash (F type), and 3%-5% alkaline activator (Na2SiO3 or water glass), with the sum of the percentages of the above components being 100%.

[0097] Example 7 Figure 2 This is a schematic flowchart of a method for preparing a red mud-based filling slurry according to an embodiment of this application, as shown below. Figure 2 As shown, the method for preparing red mud-based filling slurry in this embodiment may include: S101. Ensure that the red mud slurry flows evenly into the pre-homogenization and mixing unit and stir the red mud slurry.

[0098] S102. Input the red mud slurry in the pre-homogenization and slurry conditioning unit into the deep cone thickening unit, and add flocculant to the deep cone thickening unit.

[0099] The main chemical components of red mud include SiO2 (10%-20%), Fe2O3 (30%-50%), Al2O3 (10%-25%), CaO (2%-10%), Na2O (2%-10%), and TiO2 (3%-8%), with a pH value typically between 10 and 13. It is usually discharged from alumina plants in the form of red mud slurry.

[0100] Red mud has a fine particle size (d 50 Due to its characteristics of being typically <20μm and having high viscosity, its sedimentation and concentration behavior is fundamentally different from that of conventional tailings.

[0101] The deep cone thickening unit can deeply concentrate low-concentration red mud slurry and output high-concentration underflow from the bottom of the deep cone thickening unit.

[0102] Flocculants can cause red mud slurry to form flocs and settle downwards at a certain speed, thereby increasing the concentration of red mud slurry (also known as underflow) in the deep cone thickening unit within a preset range near the bottom.

[0103] S103. Determine the discharge flow rate of the deep cone thickening unit based on the red mud slurry concentration measured by the concentration meter, the flow rate measured by the flow meter, the preset residence time, and the target concentration of the red mud slurry in the preset area at the bottom of the deep cone thickening unit.

[0104] The concentration meter and flow meter are located at the outlet of the pre-homogenization and slurry conditioning unit.

[0105] In some cases, the preset residence time is less than or equal to the maximum residence time of red mud in the deep cone thickener. The maximum residence time can be determined based on the effective settling volume of the deep cone thickener unit, the volumetric flow rate of the red mud slurry feed, the concentration of the red mud slurry flowing into the deep cone thickener unit, and the target concentration flowing out of the deep cone thickener unit.

[0106] S104. Send the discharge flow rate to the underflow pump located at the outlet of the deep cone thickening unit so that the underflow pump inputs the red mud slurry in the deep cone thickening unit into the buffer control unit according to the discharge flow rate.

[0107] The underflow pump allows red mud slurry within a preset bottom range in the deep cone thickening unit to flow out of the unit's outlet and into the buffer control unit. The underflow pump is a variable frequency underflow pump.

[0108] To distinguish it from subsequent embodiments, the underflow pump in this embodiment may be underflow pump B1.

[0109] When the upstream continuous feeding system is in operation or not operating, the buffer control unit is used to temporarily store a certain amount of red mud slurry flowing out of the deep cone thickening unit, so as not to affect the upstream continuous feeding and avoid frequent start-up and shutdown of the deep cone thickening unit.

[0110] S105. The red mud slurry is input into the online modification unit through the buffer control unit.

[0111] S106. Add a modifier to the online modification unit to solidify the free alkali in the red mud slurry flowing into the online modification unit, thereby obtaining modified red mud slurry.

[0112] In the online modification unit, the modifier is mixed with the red mud slurry. The modifier can solidify the free alkali in the red mud slurry flowing into the online modification unit, resulting in modified red mud slurry. This avoids the strong alkalinity of the red mud causing a later-stage efflorescence strength reduction in the filling body, i.e., free Na+. + During the hydration process of the filling material, Na2CO3 white crystals migrate to the surface and form, resulting in surface powdering and a loose internal structure.

[0113] The modifier is a composite activator composed of desulfurized gypsum and fly ash mixed at a mass ratio of 1:1.5~2.5 (preferably 1:2.0), and the dosage is 8%-12% (preferably 10%) of the dry weight of the red mud. In the online modification unit, the free alkali in the red mud reacts with CaSO4·2H2O in the desulfurized gypsum in the following chemical reaction: Pathway 1: Erythrite formation reaction (NaOH fixed path): Ca² provided by desulfurized gypsum + and SO4² -The red mud reacts with Al2O3 and NaOH in the presence of free water to form insoluble ettringite (3CaO·Al2O3·3CaSO4·32H2O), releasing free Na... + Fixed within the ettringite crystal structure: 6Ca² + +2Al(OH)4 - +3SO4² - +26H2O→Ca6Al2(SO4)3(OH) 12 ·26H2O Pathway: Sodium carbonate conversion reaction (Na2CO3 fixed path): Na2CO3 in red mud undergoes a double decomposition reaction with CaSO4·2H2O: Na2CO3+CaSO4·2H2O→CaCO3↓+Na2SO4+2H2O The generated sparingly soluble CaCO3 precipitate precipitates out of the solution, while Na2SO4 is either adsorbed and fixed by CSH gelation or solidified with the mineralization of the filling material during subsequent hydration reactions.

[0114] Pathway 3: Formation of hydrotalcite-like phase (MgO synergistic fixation pathway): Bayer process red mud typically contains 2%-5% MgO. Under alkaline conditions, Mg²⁺… + With CO3² - and OH - The reaction produces a hydrotalcite-like phase (Mg6Al2(OH)). 16 CO3·4H2O) further adsorbs and fixes carbonate ions.

[0115] The three reaction pathways described above work synergistically to transform the free alkalis (NaOH, Na2CO3) in red mud into insoluble or sparingly soluble mineral phases (ettringite, CaCO3, and hydrotalcite-like phases), achieving mineralogical solidification of the alkalis. Simultaneously, the generated ettringite, along with the active components (active SiO2, Al2O3) in desulfurized gypsum and fly ash, synergistically stimulate the latent pozzolanic activity of the red mud, promoting the formation of hydration products.

[0116] The online modification unit in this embodiment can achieve in-situ chemical fixation of free alkali and activation of potential activity in red mud. It uses all industrial solid waste as the modification raw material, realizing "waste treatment with waste," while simultaneously activating the red mud to reduce the amount of cementitious materials used and lower treatment costs. The series coupling of online modification with the thickening-buffering process enables continuous treatment from dewatering to modification.

[0117] S107. Add cementitious material to the mixing and filling unit to mix the cementitious material and the modified red mud slurry to form a filling slurry.

[0118] In the mixing and filling unit, the cementitious material and red mud slurry are fully mixed to form a filling slurry, which is used to fill the mine. After solidification, it forms a filling body.

[0119] In this embodiment, a uniform distributor is installed at the red mud slurry inlet of the pre-homogenization and conditioning unit, ensuring that the red mud slurry flows evenly into the pre-homogenization and conditioning unit. The pre-homogenization and conditioning unit agitates the flowing red mud slurry. The control unit determines the discharge flow rate of the deep cone thickening unit based on the red mud slurry concentration measured by the concentration meter, the flow rate measured by the flow meter, the preset residence time, and the target concentration of the red mud slurry in the preset area at the bottom of the deep cone thickening unit. The discharge flow rate is then sent to the underflow pump. The underflow pump, based on the discharge flow rate, inputs the red mud slurry from the deep cone thickening unit into the buffer control unit. In the online modification unit, the free alkali in the flowing red mud slurry is solidified to obtain modified red mud slurry. In the mixing and filling unit, the cementitious material and the modified red mud slurry are mixed to form a filling slurry. Due to the uniform distributor installed at the inlet of the pre-homogenization and conditioning unit, the red mud slurry flows evenly into the pre-homogenization and conditioning unit. The slurry flows evenly along the cross-section of the tank and is stirred, which eliminates fluctuations in the concentration and flow rate of the red mud slurry itself, ensuring that the concentration of the red mud slurry entering the deep cone thickening unit is uniform. On this basis, the concentration meter and flow meter at the outlet of the pre-homogenization and slurry conditioning unit detect the concentration and flow rate of the outflowing red mud slurry, which can truly reflect the state of the red mud slurry flowing into the deep cone thickening unit. Based on this, the control unit calculates and controls the underflow discharge flow rate of the deep cone thickening unit in combination with the preset residence time and the underflow target concentration, so that the red mud particles can obtain sufficient settling time in the deep cone thickening unit, thereby obtaining red mud slurry with stable concentration. Furthermore, the red mud slurry with relatively stable concentration can flow to downstream units such as the buffer control unit, ultimately facilitating the obtaining of filling slurry with stable concentration, and thus facilitating the improvement of the strength of the filling body formed based on the filling material.

[0120] Figure 3 This is a logic diagram for controlling a deep cone thickening unit according to an embodiment of this application. By detecting parameters such as feed concentration, feed flow rate, mud layer height, output concentration, and rake torque of the deep cone thickening unit, the time, flocculant dosage, and underflow discharge velocity are determined. The flocculant dosage, rake lifting and lowering, and underflow pump frequency conversion control are then implemented to achieve stable underflow concentration, a small time error range, and minimal mud layer fluctuation.

[0121] As an optional implementation, determining the discharge flow rate of the deep cone thickening unit based on the red mud concentration measured by the concentration meter, the flow rate measured by the flow meter, the preset residence time, and the target concentration of the red mud in the preset area at the bottom of the deep cone thickening unit includes: obtaining the mud layer height corresponding to the sidewall of the deep cone thickening unit; and determining the discharge flow rate of the deep cone thickening unit based on the mud layer height, the radius of the cone bottom of the deep cone thickening unit, the red mud concentration measured by the concentration meter, the flow rate measured by the flow meter, the preset residence time, and the target concentration of the red mud in the preset area at the bottom of the deep cone thickening unit.

[0122] As an optional implementation, inputting red mud slurry from the pre-homogenization and conditioning unit into the deep cone thickening unit includes: when the deep cone thickening unit is unloaded, inputting the red mud slurry from the pre-homogenization and conditioning unit into the deep cone thickening unit at a flow rate Q1 within a preset residence time; and continuing to input the red mud slurry from the pre-homogenization and conditioning unit into the deep cone thickening unit at a flow rate Q1 after the preset residence time is reached; the step of sending the discharge flow rate to the underflow pump located at the outlet of the deep cone thickening unit, so that the underflow pump inputs the red mud slurry from the deep cone thickening unit into the buffer control unit according to the discharge flow rate, includes: when the preset residence time is reached, sending a start signal to the underflow pump, the start signal including the discharge flow rate, so that the underflow pump starts running according to the start signal and inputs the red mud slurry from the deep cone thickening unit into the buffer control unit according to the discharge flow rate.

[0123] As an optional implementation, after the red mud slurry in the pre-homogenization and conditioning unit is input into the deep cone thickening unit at a flow rate Q1, the method further includes: stopping the input of red mud slurry from the pre-homogenization and conditioning unit into the deep cone thickening unit when a preset residence time is reached; determining the solid mass contained in the red mud slurry in the deep cone thickening unit based on the flow rate Q1, the preset residence time, and the concentration of the red mud slurry input into the deep cone thickening unit; and determining a new discharge flow rate based on the solid mass, the new residence time, and the target concentration.

[0124] As an optional implementation, after the red mud slurry in the pre-homogenization and conditioning unit is input into the deep cone thickening unit at a flow rate Q1, the method further includes: when a preset residence time is reached, continuing to input the red mud slurry in the pre-homogenization and conditioning unit into the deep cone thickening unit at a flow rate Q2; determining the solid mass contained in the red mud slurry in the deep cone thickening unit based on the flow rate Q1, the preset residence time, and the concentration of the red mud slurry input into the deep cone thickening unit; and determining a new discharge flow rate based on the new residence time, the flow rate Q2, the concentration of the red mud slurry input into the deep cone thickening unit, and the target concentration.

[0125] As an optional implementation, the mass of the modifier to be added is determined based on the dry mass of the red mud slurry in the online modification unit; and the modifier is added to the online modification unit based on the mass of the modifier.

[0126] As an optional implementation, the liquid level of the red mud slurry in the buffer control unit is measured; based on the operating status of the mine filling system and the value measured by the level gauge, the flow rate entering the deep cone thickening unit and / or the frequency of the underflow pump are determined.

[0127] As an alternative implementation, the concentration of the red mud slurry flowing out of the online modification unit is measured; the mass of the new modifier is determined based on the value measured by the pH meter.

[0128] The above method embodiments are similar in principle to the aforementioned preparation system embodiments, and the specific processes can be referred to each other.

[0129] It should be noted that, in this document, relational terms such as "first" and "second" are used only 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.

[0130] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0131] The above description is merely a specific embodiment of this application, but the scope of protection 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 this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A red mud-based filling slurry preparation system, characterized in that, include: A pre-homogenization and slurry conditioning unit is used to stir the incoming red mud slurry; a uniform distributor is provided at the red mud slurry inlet of the pre-homogenization and slurry conditioning unit, and a concentration meter A and a flow meter are provided at the outlet; the concentration meter A and the flow meter are respectively connected to the control unit. The deep cone thickening unit has its red mud slurry inlet connected to the outlet of the pre-homogenization and slurry conditioning unit, and its flocculant inlet is used for adding flocculant. A buffer control unit, the inlet of which is connected to the bottom outlet of the deep cone thickening unit via an underflow pump B; An online modification unit is provided, wherein the red mud slurry inlet of the online modification unit is connected to the outlet of the buffer control unit, and the modifier inlet is used to add modifier, which is used to solidify the free alkali in the red mud slurry flowing into the online modification unit to obtain modified red mud slurry. The mixing and filling unit has a red mud slurry inlet connected to the outlet of the online modification unit, and a cementitious material inlet for adding cementitious material to mix with the modified red mud slurry to form a filling slurry. The control unit is used to determine the discharge flow rate of the deep cone thickening unit based on the red mud concentration measured by the concentration meter A, the flow rate measured by the flow meter, the preset residence time, and the target concentration of the red mud in the preset area at the bottom of the deep cone thickening unit; and to send the discharge flow rate to the underflow pump B. The underflow pump B is used to input the red mud slurry in the deep cone thickening unit into the buffer control unit according to the discharge flow rate.

2. The red mud-based filling slurry preparation system according to claim 1, characterized in that, The deep cone thickening unit includes a deep cone thickener; the housing of the deep cone thickener includes a conical bottom and sidewalls disposed on the conical bottom; A mud layer interface instrument is provided on the side wall. The mud layer interface instrument is connected to the control unit and is used to measure the mud layer height corresponding to the side wall and send the mud layer height to the control unit. The control unit is specifically used to determine the discharge flow rate of the deep cone thickener based on the mud layer height, the radius of the cone bottom, the red mud slurry concentration measured by the concentration meter A, the flow rate measured by the flow meter, the preset residence time, and the target concentration of the red mud slurry in the preset area at the bottom of the deep cone thickener.

3. The red mud-based filling slurry preparation system according to claim 1, characterized in that, The pre-homogenization and slurry conditioning unit is specifically used to input red mud slurry into the deep cone thickening unit at a flow rate Q1 within a preset residence time when the deep cone thickening unit is unloaded; and to continue inputting red mud slurry into the deep cone thickening unit at a flow rate Q1 when the preset residence time is reached. The control unit is also used to send a start signal to the underflow pump B, the start signal including the discharge flow rate; The underflow pump B is specifically used to start operation according to the start signal, so as to input the red mud slurry in the deep cone thickening unit into the buffer control unit according to the discharge flow rate.

4. The red mud-based filling slurry preparation system according to claim 1, characterized in that, The pre-homogenization and slurry conditioning unit is also used to stop feeding red mud slurry into the deep cone thickening unit when the preset residence time is reached; The control unit is also used to determine the solid mass of the red mud slurry in the deep cone thickening unit based on the flow rate Q1, the preset residence time, and the concentration of the red mud slurry input to the deep cone thickening unit; and to determine a new discharge flow rate based on the solid mass, the new residence time, and the target concentration.

5. The red mud-based filling slurry preparation system according to claim 1, characterized in that, When the preset residence time is reached, the pre-homogenization and slurry conditioning unit is further configured to continue feeding red mud slurry into the deep cone thickening unit at a flow rate Q2. The control unit is further configured to determine the solid mass of the red mud slurry in the deep cone thickening unit based on the flow rate Q1, the preset residence time, and the concentration of the red mud slurry fed into the deep cone thickening unit; and to determine a new discharge flow rate based on the new residence time, the flow rate Q2, the concentration of the red mud slurry fed into the deep cone thickening unit, and the target concentration.

6. The red mud-based filling slurry preparation system according to claim 1, characterized in that, The online modification unit includes: The reactor has its red mud slurry inlet connected to the outlet of the buffer control unit, and its outlet connected to the inlet of the stirring and filling unit. Modifier storage silo, used for storing modifiers; A feeder is located between the outlet of the modifier storage silo and the feed port of the reactor; the feeder is connected to the control unit. The control unit is also used to determine the mass of the modifier to be added based on the dry mass of the red mud in the reactor; The feeder is used to add the modifier into the reactor according to the mass of the modifier.

7. A method for preparing a filling slurry based on red mud, characterized in that, include: The red mud slurry is evenly fed into the pre-homogenization and mixing unit. The red mud slurry in the pre-homogenization and slurry conditioning unit is fed into the deep cone thickening unit, and flocculant is added to the deep cone thickening unit; The discharge flow rate of the deep cone thickening unit is determined based on the red mud slurry concentration measured by the concentration meter, the flow rate measured by the flow meter, the preset residence time, and the target concentration of the red mud slurry in the preset area at the bottom of the deep cone thickening unit; the concentration meter and the flow meter are located at the outlet of the pre-homogenization and conditioning unit. The discharge flow rate is sent to the underflow pump located at the outlet of the deep cone thickening unit, so that the underflow pump inputs the red mud slurry in the deep cone thickening unit into the buffer control unit according to the discharge flow rate; The red mud slurry is input into the online modification unit through the buffer control unit; A modifier is added to the online modification unit to solidify the free alkali in the red mud slurry flowing into the online modification unit, thereby obtaining modified red mud slurry; A cementitious material is added to the mixing and filling unit to mix the cementitious material with the modified red mud slurry to form a filling slurry.

8. The method for preparing red mud-based filling slurry according to claim 7, characterized in that, The determination of the discharge flow rate of the deep cone thickening unit based on the red mud concentration measured by the concentration meter, the flow rate measured by the flow meter, the preset residence time, and the target concentration of the red mud in the preset area at the bottom of the deep cone thickening unit includes: Obtain the mud layer height corresponding to the sidewall of the deep cone thickening unit; The discharge flow rate of the deep cone thickening unit is determined based on the mud layer height, the radius of the cone bottom of the deep cone thickening unit, the red mud concentration measured by the concentration meter, the flow rate measured by the flow meter, the preset residence time, and the target concentration of the red mud in the preset area at the bottom of the deep cone thickening unit.

9. The method for preparing red mud-based filling slurry according to claim 8, characterized in that, The process of feeding red mud slurry from the pre-homogenization and slurry conditioning unit into the deep cone thickening unit includes: When the deep cone thickening unit is unloaded, the red mud slurry in the pre-homogenization and conditioning unit is fed into the deep cone thickening unit at a flow rate of Q1 within a preset residence time; when the preset residence time is reached, the red mud slurry in the pre-homogenization and conditioning unit is continued to be fed into the deep cone thickening unit at a flow rate of Q1. The step of sending the discharge flow rate to the underflow pump located at the outlet of the deep cone thickening unit, so that the underflow pump inputs the red mud slurry in the deep cone thickening unit into the buffer control unit according to the discharge flow rate, includes: When the preset residence time is reached, a start signal is sent to the underflow pump located at the outlet of the deep cone thickening unit. The start signal includes the discharge flow rate, so that the underflow pump starts to run according to the start signal and inputs the red mud slurry in the deep cone thickening unit into the buffer control unit according to the discharge flow rate.

10. The method for preparing red mud-based filling slurry according to claim 9, characterized in that, After the red mud slurry in the pre-homogenization and conditioning unit is input into the deep cone thickening unit at a flow rate of Q1, the method further includes: When the preset residence time is reached, the input of red mud slurry from the pre-homogenization and slurry conditioning unit into the deep cone thickening unit is stopped; Based on the flow rate Q1, the preset residence time, and the concentration of red mud slurry input to the deep cone thickening unit, the mass of solids contained in the red mud slurry in the deep cone thickening unit is determined; The new emission flow rate is determined based on the solid mass, the new residence time, and the target concentration.

11. The method for preparing red mud-based filling slurry according to claim 9, characterized in that, After the red mud slurry in the pre-homogenization and conditioning unit is input into the deep cone thickening unit at a flow rate of Q1, the method further includes: When the preset residence time is reached, the red mud slurry in the pre-homogenization and conditioning unit is continued to be fed into the deep cone thickening unit at a flow rate of Q2; Based on the flow rate Q1, the preset residence time, and the concentration of red mud slurry input to the deep cone thickening unit, the mass of solids contained in the red mud slurry in the deep cone thickening unit is determined; A new discharge flow rate is determined based on the new residence time, flow rate Q2, the concentration of red mud slurry input to the deep cone thickening unit, and the target concentration.

12. The method for preparing red mud-based filling slurry according to claim 7, characterized in that, Also includes: The mass of the modifier to be added is determined based on the dry mass of the red mud slurry in the online modification unit. The modifier is added to the online modification unit according to the mass of the modifier.

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