Preparation method and system of three-phase slurry of carbon dioxide mineralization and waste grading

Abstract

This invention discloses a method for preparing a three-phase slurry using carbon dioxide mineralization and solid waste grading, comprising: pretreatment and precise supply of coal-based solid waste raw materials; intelligent prediction of grading and batching; preparation of primary slurry; preparation of secondary slurry; pressurized CO2 three-phase mineralization reaction; and depressurization, stabilization, and storage of the mineralized slurry. The three-phase slurry preparation system using carbon dioxide mineralization and solid waste grading includes a raw material storage and supply unit, a primary slurry preparation unit, a secondary slurry preparation unit, and a CO2 mineralization reaction unit connected in sequence. The method and system for preparing a three-phase slurry using carbon dioxide mineralization and solid waste grading employs multi-solid waste grading, using a combination of coarse and fine particles in slurry preparation and coal slime as a rheology modifier to regulate the shear-thickening and swelling plasticity characteristics of pure coal gangue slurry into a shear-thinning pseudoplastic three-phase slurry, significantly increasing slurry density and reducing viscosity and transportation energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of solid waste comprehensive utilization technology, and relates to a method for preparing three-phase slurry with carbon dioxide mineralization and solid waste gradation, as well as a system for preparing three-phase slurry with carbon dioxide mineralization and solid waste gradation. Background Technology

[0002] Coal mining generates large amounts of coal gangue and coal slime, while coal combustion produces a significant amount of fly ash. The comprehensive utilization of coal-based solid waste has always been a major factor hindering the green and low-carbon transformation of the coal industry. Conventional landfill methods easily lead to land occupation and environmental pollution. Slurry backfilling, which mixes coal-based solid waste with water to create a fluid slurry, is pumped into the mine for backfilling. This method effectively disposes of large quantities of solid waste, controls goaf subsidence, and ensures safe mine production, making it an important pathway for green mine construction. However, existing backfill slurries often use single or simply compounded solid waste, relying on empirical proportions. The particle size distribution lacks rationality and is deficient in gradation design based on the closest packing theory, resulting in poor rheological properties, easy segregation and bleeding, and difficulty meeting the requirements for long-distance pipeline transportation and backfilling. Meanwhile, coal-based solid waste is alkaline and cannot be directly used for underground backfilling; it requires modification. CO2 emitted from industry and mining areas reacts with active substances like Ca and Mg in coal gangue and fly ash through mineralization to generate carbonate ions, thereby adjusting the pH of the coal-based solid waste to 6 to 9, meeting the "Standards for Pollution Control of General Industrial Solid Waste Storage and Landfilling." Therefore, developing a three-phase slurry preparation technology that integrates multi-solid waste synergistic gradation, online CO2 mineralization, and intelligent control, can improve density, enhance slurry rheology, reduce viscosity and transportation energy consumption compared to conventional backfilling slurries, while simultaneously achieving in-situ carbon fixation. This is of great significance for realizing the large-scale low-carbon utilization of solid waste. Summary of the Invention

[0003] The purpose of this invention is to provide a three-phase slurry preparation method for carbon dioxide mineralization and solid waste gradation, which solves the problem of difficult resource utilization of coal-based solid waste in the prior art.

[0004] Another objective of this invention is to provide a three-phase slurry preparation system for carbon dioxide mineralization and synergistic solid waste gradation.

[0005] The technical solution adopted in this invention is a method for preparing a three-phase slurry for carbon dioxide mineralization and synergistic solid waste gradation, comprising: Step 1: Pre-treatment and precise supply of coal-based solid waste raw materials; Step 2: Intelligent prediction of gradation and batching; Step 3: Prepare the primary slurry; Step 4: Prepare secondary slurry; Step 5: Pressurized CO2 three-phase mineralization reaction; Step 6: Depressurization, stabilization, and storage of the mineralized slurry.

[0006] The invention is further characterized by: Step 1 includes coal gangue pretreatment and feeding, fly ash pretreatment and feeding, and coal slime pretreatment and feeding; Step 2 includes: Step 2.1: Input raw material physical property parameters; The detection parameters of the pretreated raw materials are entered into the gradation and batching prediction software; Step 2.2: Solving for the closest packing ratio; With the goal of achieving the highest packing density of solid waste particles and the best rheological properties of slurry, the optimal dry basis mass ratio that minimizes the deviation between the measured particle size distribution and the theoretical curve was calculated. Step 2.3: Prediction of slurry properties and transport parameters; The software outputs the core parameters of the slurry under the optimal ratio, and completes the verification of coal-based solid waste ratio and equipment selection. Step 2.4: Issuance of hardware control commands; Based on the prediction results, the intelligent control system issues operating parameter commands to all hardware units.

[0007] Step 3 includes: Step 3.1: Add materials and process water; The coal gangue feeder and fly ash feeder deliver raw materials to the primary mixing tank according to the optimal ratio; the No. 1 process water pump sends water from the No. 1 process water tank into the primary mixing tank through the flow metering valve according to the preset water-solid ratio. Step 3.2: Mix using dual-shaft counter-rotating stirring; Step 3.3: Online monitoring and parameter feedback control; Real-time acquisition of slurry viscosity and density data; data transmission to intelligent control system for comparison with predicted parameters; if the deviation exceeds the allowable range, automatic adjustment of the flow rate of process water pump No. 1 and adjustment of process water dosage until the parameters meet the standard; Step 3.4: Determining the end point of stirring; If the preset stirring termination condition is met, one slurry preparation is completed; if the preset stirring termination condition is not met, stirring continues.

[0008] Step 4 includes: Step 4.1: Add slurry and coal slime in one step; The primary slurry is fed into the secondary mixing tank via a primary slurry conveyor; the coal slime feeder feeds coal slime into the secondary mixing tank as a rheology modifier according to a preset amount; Step 4.2: Dissolving and adding additives; Process water pump No. 3 sends water from process water tank No. 2 into additive dissolving tank; additives from additive storage tank are added to dissolving tank in proportion and stirred to dissolve; additive supply pump sends the prepared additive solution into secondary stirring tank 11. Step 4.3: Segmented high-shear mixing and homogenization; Start the high-shear mixer and mix in two stages: a high-shear dispersion stage and a low-speed homogenization stage. Step 4.4: Online monitoring and parameter feedback control; Real-time collection of slurry parameters and comparison with predicted values: If the viscosity is too high or the density is too high, the No. 2 process water pump is automatically started to add process water and reduce the slurry concentration. If the viscosity is too low or the density is too small, the flow rate of the slurry conveyor and additive supply pump will be automatically increased once to add slurry and additives. Step 4.5: Secondary slurry delivery; Once the slurry parameters meet the standards, the secondary slurry is transported to the three-phase reactor via a secondary slurry conveyor to enter the mineralization reaction stage.

[0009] Step 5 includes: Step 5.1, Reactor feeding; Choose between batch pressurized reactors or continuous pressurized reactors based on production scale; Step 5.2: Setting reaction conditions and introducing CO2; Start the heating jacket to raise the temperature inside the reactor to the set range; adjust the pressure reducing valve to introduce CO2 into the reactor and control the reaction pressure at the set value. Step 5.3: Real-time monitoring of the reaction process; Real-time acquisition of reaction parameters and transmission to the intelligent control system; Step 5.4: Joint determination of the reaction endpoint; If the rate of change of pH and conductivity meets the reaction termination condition, the mineralization reaction is complete; if the rate of change of pH and conductivity does not meet the reaction termination condition, the mineralization reaction continues. Step 5.5: Reaction cessation and material discharge preparation; Heating and CO2 intake are stopped, and the slurry after reaction is continuously discharged through a pressure reducing and regulating valve; Step 6 includes: Step 6.1: Depressurize and stabilize the buffer tank. The mineralized three-phase slurry is fed into a buffer tank and pressure stabilization is completed under normal pressure. Step 6.2, Three-phase slurry delivery; The three-phase slurry conveyor transports the pressure-stabilized slurry to the three-phase slurry storage tank; Step 6.3: Store in an insulated environment to prevent sedimentation; Maintain the temperature inside the tank within the set range, start the low-speed agitator, and monitor the pH value of the slurry in real time.

[0010] Another technical solution adopted in this invention is a three-phase slurry preparation system for carbon dioxide mineralization and solid waste gradation, comprising a raw material storage and supply unit, a primary slurry preparation unit, a secondary slurry preparation unit, and a CO2 mineralization reaction unit connected in sequence. The raw material storage and supply unit, the primary slurry preparation unit, the secondary slurry preparation unit, and the CO2 mineralization reaction unit are respectively connected to an intelligent control system, and the intelligent control system is connected to the gradation and batching unit.

[0011] Another feature of the technical solution of the present invention is that: The raw material storage and supply unit includes a coal gangue silo, a coal gangue feeder, and a coal gangue feeder connected in sequence. The bottom of the coal gangue silo is equipped with an anti-clogging device, and the coal gangue feeder is equipped with a weighing scale. The raw material storage and supply unit also includes a fly ash silo, a fly ash feeder, and a fly ash feeder connected in sequence. The top of the fly ash silo is equipped with a pulse bag dust collector. The raw material storage and supply unit also includes a coal slime silo, a coal slime feeder, and a coal slime feeder connected in sequence. The coal slime silo is equipped with an agitator. The coal gangue feeder and fly ash feeder are connected to the primary slurry preparation unit, and the coal slime feeder is connected to the secondary slurry preparation unit.

[0012] The primary slurry preparation unit includes a primary mixing tank, which is connected to a primary process water tank via a primary process water pump. The primary mixing tank is also connected to a coal gangue feeder and a fly ash feeder. An online viscometer and an online density meter are installed inside the primary mixing tank, and a flow metering valve is installed between the primary mixing tank and the primary process water pump.

[0013] The secondary slurry preparation unit includes a secondary mixing tank, which is connected to the primary mixing tank via a primary slurry conveyor, and is also connected to a coal slime feeder. The secondary mixing tank is connected to an additive dissolving tank via an additive feeding pump, and the additive dissolving tank is connected to an additive storage tank. The secondary mixing tank is connected to a second process water tank via a second process water pump, and the second process water tank is connected to the additive dissolving tank via a third process water pump.

[0014] The CO2 mineralization reaction unit includes a three-phase reactor, which is connected to a secondary mixing tank via a secondary slurry conveyor and a carbon dioxide storage tank via a pressure reducing valve. The three-phase reactor is also connected to a buffer tank via a pressure relief valve. The buffer tank is connected to a three-phase slurry storage tank via a three-phase slurry conveyor. The three-phase reactor is equipped with an online pH meter, an online conductivity meter, a temperature sensor, and a pressure sensor. The three-phase reactor can be configured as a batch pressurized reactor or a continuous pressurized reactor.

[0015] The beneficial effects of this invention are as follows: This invention employs a multi-solid waste synergistic gradation method, using a combination of coarse and fine particles for slurry preparation and coal slime as a rheology modifier to regulate the shear-thickening and swelling plasticity characteristics of pure coal gangue slurry into a shear-thinning pseudoplastic three-phase slurry, significantly increasing slurry density and reducing viscosity and transportation energy consumption. Coal slime, coal gangue, fly ash, and coal slime can be utilized locally, constructing a complete solid waste disposal system with strong engineering feasibility and a high solid waste resource utilization rate.

[0016] This invention develops embedded batching prediction software, with the Andreasen closest packing model as its core, to achieve intelligent control of pre-mixing ratio prediction, real-time feedback during the process, and post-optimization iteration. It links all hardware equipment in the process, gets rid of traditional experience-based operation, and combines big data machine learning optimization model to achieve intelligent upgrade of the pulping process.

[0017] This invention integrates a CO2 mineralization reaction unit, coupling CO2 in-situ mineralization with slurry preparation. It is suitable for high, medium, and low concentration industrial waste gases near mining areas, such as coal chemical tail gas and coal-fired boiler flue gas, to achieve on-site CO2 consumption and storage. At the same time, it adjusts the pH value of the slurry and strengthens the slurry structure to meet the requirements of underground filling. It achieves a synergistic effect of solid waste disposal, carbon sequestration and mine management, providing a path for low-carbon green transformation and sustainable development for coal mines. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the three-phase slurry preparation system for carbon dioxide mineralization and synergistic solid waste gradation of the present invention; Figure 2 This is a schematic diagram showing the comparison between the measured and predicted values ​​of the rotational viscosity of three-phase slurries with different mass concentrations in an embodiment of the present invention; Figure 3 This is a schematic diagram showing the relationship between the mass ratio of coal slime blending and the viscosity of the three-phase slurry in an embodiment of the present invention.

[0019] In the diagram, 1. Coal gangue silo; 2. Coal gangue feeder; 3. Coal gangue feeder; 4. Fly ash silo; 5. Fly ash feeder; 6. Fly ash feeder; 7. Primary mixing tank; 8. Process water tank No. 1; 9. Process water pump No. 1; 10. Primary slurry conveyor; 11. Secondary mixing tank; 12. Additive storage tank; 13. Additive dissolving tank; 14. Additive feed pump; 15. Coal slime silo; 16. Coal slime feeder; 17. Coal slime feeder; 18. Process water tank No. 2; 19. Process water pump No. 2; 20. Process water pump No. 3; 21. Secondary slurry conveyor; 22. Three-phase reactor; 23. Carbon dioxide storage tank; 24. Pressure reducing valve; 25. Pressure relief valve; 26. Buffer tank; 27. Three-phase slurry conveyor; 28. Three-phase slurry storage tank. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0021] Example 1 This embodiment proposes a three-phase slurry preparation method for carbon dioxide mineralization and synergistic solid waste gradation, including: Step 1: Pre-treatment and precise supply of coal-based solid waste raw materials; This step completes the classification, pretreatment, storage, and metering feeding of three core raw materials: coal gangue, fly ash, and coal slime, providing qualified raw materials for subsequent gradation and slurry preparation, including coal gangue pretreatment and feeding, fly ash pretreatment and feeding, and coal slime pretreatment and feeding. Step 2: Intelligent prediction of gradation and batching; This step is the core of the entire process, using mathematical modeling to solve for the optimal solid waste ratio, predict slurry performance, and issue control commands to the hardware system.

[0022] Step 3: Prepare a primary slurry (premix coarse and fine particles); This step involves initially mixing coarse coal gangue particles with fine fly ash particles, using the fine particles to fill the gaps between the coarse particles and increase the bulk density of the slurry.

[0023] Step 4: Prepare secondary slurry (homogenization of all components); This step involves incorporating coal slime and additives to transform the slurry from a shear-thickening dilatant fluid to a shear-thinning pseudoplastic fluid, thereby optimizing its rheological properties and stability.

[0024] Step 5: Pressurized CO2 three-phase mineralization reaction; This step achieves a three-phase reaction of solid (coal-based solid waste), liquid (process water), and gas (CO2), completing CO2 sequestration and slurry pH adjustment, while also strengthening the slurry structure.

[0025] Step 6: Depressurization, stabilization, and storage of the mineralized slurry.

[0026] Example 2 Based on Example 1, this example proposes a coal gangue pretreatment and feeding process, including: A1. Coal gangue is crushed to a preset particle size range by a jaw crusher and then graded and screened by a vibrating screen. A2. Coal gangue with unqualified particle size is returned to the jaw crusher for re-crushing until the particle size meets the standard; A3. The qualified coal gangue particles are sealed and transported to coal gangue silo 1 for storage. The anti-blocking device at the bottom of the silo is activated to prevent the particles from clumping. A4. The intelligent control system issues an instruction, and the coal gangue feeder 2 feeds the coal gangue to the coal gangue feeder 3 at a uniform speed. A5. The coal gangue feeder 3 adjusts the conveying speed precisely according to the preset ratio, and after being weighed by the weight weighing scale, it is sent into the primary mixing tank 7. Fly ash pretreatment and feeding, including: B1. After the fly ash raw material is sorted and decarbonized, and the average particle size meets the requirements, it is sealed and transported to fly ash silo 4. B2. A pulse bag filter at the top of the silo handles the dust from the feed material and maintains the air pressure balance inside the silo. B3. Maintain the temperature inside the silo at the set temperature. After the fly ash is accurately measured by the fly ash feeder 6 according to the proportion, it is sealed and sent into the primary mixing tank 7.

[0027] Coal slime pretreatment and feeding, including: C1. After being mechanically dewatered to the set moisture content, the coal slime is transported to the coal slime silo 15. C2. Maintain the temperature inside the 15 tanks of coal slime silo at the set temperature, and use a matching agitator to rotate to prevent the coal slime from freezing and thawing and clumping. C3. The coal slime feeder 16 transports the coal slime to the coal slime feeder 17. C4. The coal slime feeder 17 accurately feeds the coal slime into the secondary mixing tank 11 according to the preset ratio.

[0028] Example 3 Based on Example 1, this example proposes step 2.1, inputting raw material physical property parameters; The detection parameters of the pretreated raw materials are entered into the gradation and batching prediction software. The input parameters include: target mass concentration of slurry, mass ratio of coal gangue / average particle size, mass ratio of fly ash / average particle size, mass ratio of coal slime / moisture content, and additive dosage.

[0029] Step 2.2: Solving for the closest packing ratio; With the goal of achieving the highest packing density of solid waste particles and the best rheological properties of slurry, the optimal dry basis mass ratio that minimizes the deviation between the measured particle size distribution and the theoretical curve is calculated based on the Andreasen closest packing model. Step 2.3: Prediction of slurry properties and transport parameters; The software outputs the core parameters of the slurry under the optimal ratio: density, weighted average particle size, rotational viscosity, and yield stress; further input of pipeline diameter, length, and conveying speed is used to calculate flow rate, total pressure drop, and pumping power, thus completing the verification of coal-based solid waste ratio and equipment selection.

[0030] Step 2.4: Issuance of hardware control commands; Based on the prediction results, the intelligent control system issues operating parameter commands to all hardware units.

[0031] Example 4 Based on Example 1, this example proposes step 3.1, the addition of materials and process water; Coal gangue feeder 3 and fly ash feeder 6 simultaneously deliver raw materials to primary mixing tank 7 according to the optimal ratio; process water pump 9 sends water from process water tank 8 to primary mixing tank 7 through flow metering valve according to preset water-solid ratio.

[0032] Step 3.2: Mix using dual-shaft counter-rotating stirring; Start the twin-shaft mixer. The shearing and thrust generated by the counter-rotating twin shafts will fully mix the coal gangue, fly ash and process water, break up particle agglomeration and achieve initial dispersion. Step 3.3: Online monitoring and parameter feedback control; The online viscometer and online densitometer installed in the middle of the primary mixing tank 7 collect the rotational viscosity and density data of the slurry in real time. The data is transmitted to the intelligent control system and compared with the predicted parameters. If the deviation exceeds the allowable range, the flow rate of the No. 1 process water pump 9 is automatically adjusted, and the amount of process water added is adjusted until the parameters meet the standard.

[0033] Step 3.4: Determining the end point of stirring; Each stirring session lasts 3-8 minutes, with the stirring endpoint set to the preset termination condition, thus completing one slurry preparation.

[0034] Example 5 Based on Example 1, this example proposes step 4.1, the initial addition of slurry and coal slime; The primary slurry is fed into the secondary mixing tank 11 via the primary slurry conveyor 10; the coal slime feeder 17 feeds coal slime into the secondary mixing tank 11 as a rheology modifier according to a preset amount.

[0035] Step 4.2: Dissolving and adding additives; Process water pump 20 sends water from process water tank 18 to additive dissolving tank 13; additives from additive storage tank 12 are added to the dissolving tank in proportion and stirred to dissolve; additive supply pump 14 sends the prepared additive solution to secondary stirring tank 11 at a uniform speed.

[0036] Step 4.3: Segmented high-shear mixing and homogenization; Start the high-shear mixer and mix in two stages: High-shear dispersion section: Strong shear force breaks down coal slime flocs, allowing coal slime, additives, and primary slurry to fully blend; Low-speed homogenization section: Reduce stirring speed to achieve uniform mixing of all components and avoid excessive shearing that could damage the slurry structure.

[0037] Step 4.4: Online monitoring and parameter feedback control; The online viscometer and densitometer in the secondary mixing tank 11 collect slurry parameters in real time and compare them with the predicted values: If the viscosity or density is too high: automatically start process water pump 19 to add process water and reduce the slurry concentration; If the viscosity is too low or the density is too small: automatically increase the flow rate of the slurry conveyor 10 and the additive supply pump 14, and add slurry and additives once.

[0038] Step 4.5: Secondary slurry delivery; Once the slurry parameters meet the standards, the secondary slurry is transported to the three-phase reactor 22 via the secondary slurry conveyor 21 to enter the mineralization reaction stage.

[0039] Example 6 Based on Example 1, this example proposes step 5.1, reactor feeding; Choose between batch or continuous pressurized reactors based on production scale: Batch type: Secondary slurry is fed into one or two parallel pressurized reactors at once, and the feed valve is closed; Continuous: Secondary slurry is continuously fed into the primary inlet of a three-stage series tubular reactor.

[0040] Step 5.2: Setting reaction conditions and introducing CO2; Start the heating jacket to raise the temperature inside the reactor to the set range; adjust the pressure reducing valve 24 to introduce CO2 into the reactor and control the reaction pressure at the set value; start the mechanical stirrer in the batch reactor to fully mix CO2 with the slurry through the bottom gas distribution plate; the continuous reactor achieves gas-liquid-solid mixing through static mixers at each stage.

[0041] Step 5.3: Real-time monitoring of the reaction process; The reactor is equipped with an online pH meter, an online conductivity meter, a temperature sensor, and a pressure sensor to collect reaction parameters in real time and transmit them to the intelligent control system.

[0042] Step 5.4: Joint determination of the reaction endpoint; The reaction endpoint is determined by a combination of pH and conductivity change rate: when the pH of the slurry drops to 6.5-7.5 and remains stable for more than 30 minutes, and the conductivity change rate approaches 0, i.e. the conductivity becomes constant, the mineralization reaction is considered complete.

[0043] Step 5.5: Reaction cessation and material discharge preparation; Stop heating and CO2 intake. For batch reactors, open pressure relief valve 25 to slowly release pressure to atmospheric pressure. For continuous reactors, control the pressure at each stage through back pressure valve. After reaction, the slurry is continuously discharged through pressure reducing regulating valve.

[0044] Example 7 Based on Example 1, this example proposes step 6.1: depressurization and stabilization of the buffer tank; The mineralized three-phase slurry is fed into buffer tank 26, where it is stabilized at atmospheric pressure to prevent pressure fluctuations from affecting subsequent transportation.

[0045] Step 6.2, Three-phase slurry delivery; The three-phase slurry conveyor 27 transports the pressure-stabilized slurry to the three-phase slurry storage tank 28.

[0046] Step 6.3: Store in an insulated environment to prevent sedimentation; The temperature inside the tank is maintained within the set range, and a low-speed agitator is started to prevent the slurry from settling and clumping after mineralization. The storage tank is equipped with an online pH meter to monitor the pH value of the slurry in real time to ensure that it meets the underground filling standards.

[0047] The preparation method in this invention includes raw material supply, gradation and batching prediction, primary slurry preparation, secondary slurry preparation, and pressurized CO2 mineralization reaction. The slurry properties are adjusted through online rheological parameter feedback during the slurry preparation process. The reaction endpoint of the mineralization reaction is determined by the combined change rate of pH and conductivity. The operating data is continuously fed back to the system to continuously optimize the gradation and batching prediction software.

[0048] This invention uses gradation and batching prediction as its core command mechanism, linking various hardware systems to achieve precise control. Simultaneously, it continuously optimizes software performance through operational data feedback and big data machine learning. Specifically, it includes raw material supply, gradation and batching, primary mixing and slurry preparation, secondary mixing and slurry preparation, and pressurized CO2 mineralization reaction. The gradation and batching prediction system receives the physical property parameters of coal-based solid waste raw materials, solves for the optimal solid waste ratio, and predicts the slurry rheological parameters. It then issues instructions to various hardware systems, controlling the feeding equipment to precisely add raw materials, the slurry preparation equipment to adjust mixing parameters, and the process water and additive dosing equipment to control dosage. During the primary / secondary mixing and slurry preparation and mineralization reaction processes, online monitoring instruments collect slurry rheological and reaction parameters in real time, feeding them back to the software and intelligent control system. These parameters are compared with the predicted values, and the software synchronously adjusts the hardware control instructions to ensure that the slurry performance and mineralization effect meet the standards. Simultaneously, the system collects real-time operational data throughout the entire process, continuously correcting the software's model coefficients through big data machine learning algorithms, constantly optimizing the accuracy of ratio calculation and performance prediction, and significantly improving system adaptability.

[0049] Example 8 This embodiment proposes a three-phase slurry preparation system for carbon dioxide mineralization and synergistic solid waste gradation, such as... Figure 1 As shown, it includes a raw material storage and supply unit, a primary slurry preparation unit, a secondary slurry preparation unit, and a CO2 mineralization reaction unit connected in sequence. The raw material storage and supply unit, the primary slurry preparation unit, the secondary slurry preparation unit, and the CO2 mineralization reaction unit are respectively connected to the intelligent control system, and the intelligent control system is connected to the grading and batching unit.

[0050] Example 9 Based on Example 8, this example proposes a raw material storage and supply unit comprising a coal gangue silo 1, a coal gangue feeder 2, and a coal gangue feeder 3 connected in sequence. The bottom of the coal gangue silo 1 is equipped with an anti-clogging device, and the coal gangue feeder 3 is equipped with a weighing scale. The raw material storage and supply unit also includes a fly ash silo 4, a fly ash feeder 5, and a fly ash feeder 6 connected in sequence. The top of the fly ash silo 4 is equipped with a pulse bag filter. The raw material storage and supply unit also includes a coal slime silo 15, a coal slime feeder 16, and a coal slime feeder 17 connected in sequence. An agitator is installed inside the coal slime silo 15. The coal gangue feeder 3 and the fly ash feeder 6 are connected to the primary slurry preparation unit, and the coal slime feeder 17 is connected to the secondary slurry preparation unit. The primary slurry preparation unit includes a primary mixing tank 7, which is connected to a primary process water tank 8 via a primary process water pump 9. The primary mixing tank 7 is also connected to a coal gangue feeder 3 and a fly ash feeder 6. An online viscometer and an online density meter are installed inside the primary mixing tank 7, and a flow metering valve is installed between the primary mixing tank 7 and the primary process water pump 9. The secondary slurry preparation unit includes a secondary mixing tank 11, which is connected to the primary mixing tank 7 via a primary slurry conveyor 10. The secondary mixing tank 11 is also connected to a coal slime feeder 17. Furthermore, the secondary mixing tank 11 is connected to an additive dissolving tank 13 via an additive feeding pump 14. The additive dissolving tank 13 is connected to an additive storage tank 12. The secondary mixing tank 11 is also connected to a second process water tank 18 via a second process water pump 19. The second process water tank 18 is connected to the additive dissolving tank 13 via a third process water pump 20. The CO2 mineralization reaction unit includes a three-phase reactor 22, which is connected to a secondary mixing tank 11 via a secondary slurry conveyor 21. The three-phase reactor 22 is also connected to a carbon dioxide storage tank 23 via a pressure reducing valve 24. The three-phase reactor 22 is connected to a buffer tank 26 via a pressure relief valve 25. The buffer tank 26 is connected to a three-phase slurry storage tank 28 via a three-phase slurry conveyor 27. The three-phase reactor 22 is equipped with an online pH meter, an online conductivity meter, a temperature sensor, and a pressure sensor. The three-phase reactor 22 can be configured as a batch pressurized reactor or a continuous pressurized reactor.

[0051] The present invention includes a raw material storage and supply unit, a primary slurry preparation unit, a secondary slurry preparation unit, a CO2 mineralization reaction unit connected in sequence, and an intelligent control system that uniformly controls the operation of each unit; the grading and batching unit is embedded with grading and batching prediction software, and each unit is uniformly regulated and controlled by the control system.

[0052] The raw material storage and supply unit stores coal gangue, fly ash, and coal slime separately in coal gangue silo 1, fly ash silo 4, and coal slime silo 15. The coal gangue feeder 2 + coal gangue feeder 3, fly ash feeder 5 + fly ash feeder 6, and coal slime feeder 16 + coal slime feeder 17 are used for precise metering and feeding to provide raw materials for graded pulping.

[0053] The raw material supply unit is used for the classification, storage, metering and feeding of three types of solid waste raw materials: coal gangue, fly ash and coal slime, providing raw materials for primary slurry preparation and secondary slurry preparation.

[0054] The coal gangue storage and feeding equipment mainly includes a coal gangue silo 1, a coal gangue feeder 2, and a coal gangue feeder 3. When gangue is produced from coal washing, large pieces of coal gangue raw material are first crushed by a jaw crusher to break them into a preset particle size range. Then, they are graded and screened by a vibrating screen. Coal gangue with unqualified particle sizes is returned to the jaw crusher for re-crushing. The qualified coal gangue particles are transported to the coal gangue silo 1 for sealed storage. The bottom of the coal gangue silo 1 is equipped with an anti-clogging device to prevent particles from agglomerating and blocking the discharge port. During feeding, the coal gangue feeder 2 is activated according to the instructions of the intelligent control system, and the coal gangue in the silo 1 is uniformly transported to the coal gangue feeder 3. The feeder 3 adopts frequency conversion control to precisely adjust the conveying speed and transport the coal gangue to the weight weighing scale to complete the measurement. After the measurement is qualified, it is sent to the primary mixing tank 7 of the primary slurry preparation unit.

[0055] In one embodiment of the present invention, the coal gangue silo 1 is made of wear-resistant steel plate; the coal gangue feeder 2 adopts a star-shaped feeding structure with a rotation speed of 15-30 r / min and an air leakage rate of ≤0.5%; the coal gangue feeder 3 adopts a variable frequency screw feeder with a rotation speed of 0-60 r / min and a feeding accuracy of ±0.3%.

[0056] The main equipment for storing and feeding fly ash includes a fly ash silo 4, a fly ash feeder 5, and a fly ash feeder 6. The fly ash feeder 5 is installed at the bottom conical opening of the fly ash silo 4, and the fly ash feeder 6 is connected to the outlet of the fly ash feeder 5. A pulse bag filter is installed at the top of the fly ash silo 4 to prevent dust leakage. Fly ash raw materials are fed into fly ash silo 4 via external conveying equipment. The pulse bag dust collector at the top of fly ash silo 4 treats the dust generated during the feeding process. After dust removal, the gas is discharged in compliance with standards, while maintaining the air pressure balance inside the silo. Fly ash is stored in fly ash silo 4 by natural settling. The bottom conical structure, together with fly ash feeder 5, prevents fly ash from agglomerating and bridging. During feeding, fly ash feeder 5 feeds at a uniform speed, conveying the fly ash in fly ash silo 4 to fly ash feeder 6. Fly ash feeder 6 adopts a variable frequency quantitative structure. According to the proportion parameters output by the gradation and batching prediction software, the feeding speed is adjusted to quantitatively convey the fly ash to the primary mixing tank 7 in the primary slurry preparation unit. The entire process is sealed and there is no dust leakage.

[0057] In one embodiment of the present invention, the temperature inside the fly ash silo 4 is maintained at 20-35℃, and the silo body is treated with anti-corrosion; the fly ash feeder 5 adopts an impeller structure with a rotation speed of 20-40 r / min and a feeding accuracy of ±0.2%; the fly ash feeder 6 is a variable frequency quantitative feeder with a feeding accuracy of ±0.2%; and the matching pulse bag dust collector has a dust removal efficiency of ≥99.5% and a pulse frequency of 10-15 times / min.

[0058] The coal slime storage and feeding equipment mainly includes a coal slime silo 15, a coal slime feeder 16, and a coal slime feeder 17. The coal slime silo 15 adopts a double-layer insulation structure to prevent the coal slime from freezing and thawing and clumping, and is equipped with an agitator. The coal slime feeder 16 is installed at the bottom of the silo 15, and the coal slime feeder 17 is a metering type, connecting the coal slime feeder 16 to the secondary mixing tank 11 in the secondary slurry preparation unit.

[0059] In one embodiment of the present invention, the insulation layer of the coal slime silo 15 is 50-80mm thick, the internal temperature is maintained at 15-30℃, and the stirring speed of the silo is 10-20r / min; the coal slime feeder 16 adopts a spiral feeding structure with a speed of 10-20r / min; the coal slime feeder 17 is a metering feed pump with a metering accuracy of ±0.3% and an outlet pressure of 0.2-0.4MPa.

[0060] The primary slurry preparation unit uses a mixer as its core to mix coal gangue, fly ash, and process water. Coarse and fine particles are dispersed in the liquid phase, while fine fly ash particles fill the spaces between the coarse coal gangue particles, resulting in a higher bulk density (i.e., higher throughput) for the same volume. The secondary slurry preparation unit further incorporates coal slime and additives, using a mixer to mix the primary slurry, coal slime, additives, and process water. Homogenization of all components is achieved through stirring. Online viscometers and densitometers monitor the slurry state in real time, allowing for feedback adjustments to the water and additive dosages to ensure stable slurry rheological properties.

[0061] The primary slurry preparation unit includes a primary mixing tank 7, a primary process water tank 8, and a primary process water pump 9. It is equipped with flow metering valves, online viscometers, and online densitometers. The online viscometers and densitometers are installed on the middle side wall of the primary mixing tank 7, ensuring full contact with the slurry inside and collecting slurry parameters in real time. The inlet of the primary mixing tank 7 is connected to the outlets of the coal gangue feeder 3 and the fly ash feeder 6. The primary process water pump 9 connects the primary process water tank 8 to the primary mixing tank 7. A flow metering valve is connected in series between the primary process water pump 9 and the primary mixing tank 7 to control the process water supply.

[0062] The process principle is as follows: Coal gangue and fly ash meeting the particle size requirements are precisely fed into the primary mixing tank 7 by coal gangue feeder 3 and fly ash feeder 6 according to the optimal gradation ratio. At the same time, process water pump 9 delivers process water from process water tank 8 to primary mixing tank 7 through a flow metering valve according to the preset water-to-solid ratio. The twin-shaft mixer is started, and the shearing and thrust generated by the counter-rotating of the twin shafts fully mixes and stirs the coal gangue, fly ash and process water, so that the coarse particles of coal gangue and the fine particles of fly ash are initially dispersed to avoid particle agglomeration. During the stirring process, the online viscometer and online densitometer collect the rotational viscosity and density data of the slurry in real time, and transmit the data to the intelligent control system in real time. The data is compared with the predicted parameters output by the gradation and batching prediction software. If the parameter deviation exceeds the allowable range, the control system automatically adjusts the flow rate of process water pump 9 and increases or decreases the amount of process water added to make the primary slurry reach the preset preliminary homogeneous state.

[0063] In one embodiment of the present invention, the primary mixing tank 7 is made of Q235B carbon steel with corrosion resistance, a wall thickness of 12-14mm, and a 5-8mm corrosion and wear allowance is reserved; the mixing blades of the dual-shaft agitator are made of wear-resistant steel, with a rotation speed of 30-60rpm, the mixing direction is dual-shaft reverse, and the single mixing time is 3-8min, with the mixing endpoint being when the solid particles are completely wetted and there is no obvious dry powder agglomeration; the first process water tank 8 is made of carbon steel with corrosion resistance.

[0064] The equipment of the secondary slurry preparation unit includes a secondary mixing tank 11 (with a built-in high-shear agitator), and is equipped with an additive storage tank 12, an additive dissolving tank 13, an additive feed pump 14, a second process water tank 18, a second process water pump 19, and a third process water pump 20. An online viscometer and an online densitometer are installed on the middle side wall of the secondary mixing tank 11, which are in full contact with the slurry in the tank to collect slurry parameters in real time.

[0065] The secondary mixing tank 11 is connected to the discharge port of the primary slurry conveyor 10, the discharge port of the coal slime feeder 17, and the outlet of the additive feed pump 14. The second process water tank 18 is connected to the secondary mixing tank 11 through the second process water pump 19 and is used to add process water to adjust the slurry concentration. The third process water pump 20 is connected to the second process water tank 18 and the additive dissolving tank 13 to provide process water for additive dissolution. The discharge port of the secondary mixing tank 11 is connected to the secondary slurry conveyor 21 and is used to transport the prepared secondary slurry to the three-phase reactor 22.

[0066] The process and control principle are as follows: After the primary slurry preparation is completed, it is sent to the secondary mixing tank 11 via the primary slurry conveyor 10; simultaneously, the coal slime stored in the coal slime silo 15 is conveyed to the secondary mixing tank 11 according to the preset amount via the coal slime feeder 16 and the coal slime feeder 17; the No. 3 process water pump 20 sends the process water in the No. 2 process water tank 18 to the additive dissolving tank 13, where it is mixed and dissolved with the additives conveyed by the additive storage tank 12, and then the additives are uniformly fed into the secondary mixing tank 11 by the additive supply pump 14; the high-shear agitator is started, and the high-speed rotating blades generate strong shear force to break up the coal slime flocs, so that the coal slime, additives and primary slurry are fully integrated to achieve homogenization of all components; during the mixing process, online Viscometers and online densitometers collect slurry rheological parameters in real time and transmit them to the intelligent control system for comparison and analysis with predicted parameters. If the slurry viscosity is too high or the density is too large, it is determined that the concentration is too high. The control system automatically starts the second process water pump 19 to add process water from the second process water tank 18 to the secondary mixing tank 11. If the slurry viscosity is too low or the density is too small, it is determined that the concentration is too low. The system automatically increases the flow rate of the primary slurry conveyor 10 and the additive supply pump 14 to add primary slurry and additives respectively until the slurry parameters reach the preset range, thus completing the secondary slurry preparation. After preparation, the secondary slurry in the secondary mixing tank 11 is sent to the three-phase reactor 22 by the secondary slurry conveyor 21 to enter the subsequent CO2 mineralization reaction stage.

[0067] In one embodiment of the present invention, the secondary mixing tank 11 is made of Q235B carbon steel with corrosion resistance, a wall thickness of 12-14mm, and a 5-8mm corrosion and wear allowance is reserved; the high-shear agitator has a speed of 100-300rpm and a mixing time of 5-10min, and the mixing process is divided into a high-shear dispersion section (3-5min) and a low-speed homogenization section (2-5min); the second process water tank 18 is made of carbon steel with corrosion resistance.

[0068] The additives in the additive storage tank 12 have two functions: dispersion and stabilization. The dispersion function is used to promote the uniform dispersion of the solid phase in water, prevent agglomeration, and reduce the viscosity of the slurry. The stabilization function is to help the slurry maintain a uniform state of properties during storage, thereby improving the stability of the slurry.

[0069] In one embodiment of the present invention, the additives selected are industrial-grade sodium sulfate, water treatment miscellaneous salts, and desulfurized gypsum, with a dosage of 0.5-1.0% (based on the dry basis mass of the slurry). If it is necessary to further improve the dispersion effect to reduce the viscosity of the slurry, 0.1-0.3% of surfactants, such as calcium lignosulfonate, sodium methylene naphthalene sulfonate, naphthalene-based surfactants, and humates, can also be compounded into the additives.

[0070] In one embodiment of the present invention, the process water in the No. 1 process water tank 8 and the No. 2 process water tank 18 is mine water. Mine water is groundwater that gushes out during coal mining and mainly contains sodium sulfate, sodium chloride, suspended solids, ferrous ions and other components. Since the mine water itself comes from underground, its use in preparing backfill materials will not have a negative impact on the groundwater. Moreover, the sodium sulfate and sodium chloride ions in the water also have a certain stabilizing effect on the slurry. On the other hand, the ion concentration of mine water is higher than that of conventional process water. Therefore, the primary mixing tank 7 and the secondary mixing tank 11 are designed with a large wall thickness, with a 5-8mm corrosion and wear allowance.

[0071] The CO2 mineralization reaction unit uses a batch or continuous pressurized reactor. Under heating and pressurization conditions, the slurry reacts fully with CO2. After the reaction, the slurry is depressurized and stabilized in a buffer tank before being transported to a storage tank for storage. Three phases refer to the simultaneous introduction of solids (coal gangue, fly ash, coal slime), liquids (process water), and gas (CO2) into the reactor for reaction, meaning that there are three phases in the reactor.

[0072] The main equipment of the CO2 mineralization reaction unit includes a three-phase reactor 22, which is a batch or continuous pressurized reactor, equipped with an online pH meter, online conductivity meter, temperature sensor, and pressure sensor. The inlet of the three-phase reactor 22 is connected to the outlet of the secondary slurry conveyor 21 to receive secondary slurry. The carbon dioxide storage tank 23 is connected to the three-phase reactor 22 via a pressure reducing valve 24 to provide CO2 gas for the mineralization reaction. The outlet of the three-phase reactor 22 is connected to the inlet of the buffer tank 26 via a pressure relief valve 25. The outlet of the buffer tank 26 is connected to the three-phase slurry storage tank 28 via the three-phase slurry conveyor 27 to complete pressure relief, conveying, and storage. The online pH meter, online conductivity meter, temperature sensor, and pressure sensor are installed inside the three-phase reactor 22 to monitor key parameters in the reaction process in real time. All equipment is electrically connected to the intelligent control system to realize automated control of the reaction process.

[0073] The three-phase reactor 22 can be designed as either a batch or continuous pressurized reactor, allowing for flexible selection based on the actual production scale. Batch-type pressurized reactors are suitable for small and medium-scale production and scenarios with varied formulas: a single or two pressurized reactors are set up in parallel as a three-phase reactor 22. The reactor body is equipped with a heating jacket, a mechanical stirrer (with built-in double-layer blades) and a CO2 bottom gas distribution plate. During operation, the secondary slurry conveyor 21 first feeds the secondary slurry into the three-phase reactor 22 in one go, and then closes the feed valve. Subsequently, the heating jacket is started to raise the temperature inside the reactor to the preset value. At the same time, the CO2 inlet valve is opened, and CO2 from the carbon dioxide storage tank 23 is evenly introduced into the three-phase reactor 22 through the pressure reducing regulating valve 24 and the bottom gas distribution plate, so that CO2 and slurry can be fully contacted. The mechanical agitator is started to drive the slurry and CO2 to mix vigorously, promote the mineralization reaction between the active components of Ca and Mg in coal-based solid waste and CO2, and generate stable minerals such as calcium carbonate and magnesium carbonate. During the reaction, the online pH meter, online conductivity meter, temperature sensor and pressure sensor collect parameters in real time and transmit them to the intelligent control system. When the preset reaction endpoint is reached (monitored by the online pH meter and online conductivity meter), heating and CO2 supply are stopped, the pressure relief valve 25 is opened, and after the pressure is released to atmospheric pressure, the slurry in the reactor is slowly sent into the buffer tank 26.

[0074] The continuous pressurized reactor is suitable for large-scale production and stable formulation scenarios. It uses a three-stage series tubular reactor as the three-phase reactor 22. Each stage reactor is equipped with a static mixer or small stirring device and temperature and pressure regulation modules. During operation, the secondary slurry is continuously fed into the primary tubular reactor via the secondary slurry conveyor 21, while CO2 is continuously introduced into each stage reactor. Under the conditions of progressively increasing pressure and temperature control, the slurry and CO2 pass through the secondary and tertiary tubular reactors to complete the mineralization reaction. During the reaction, the pressure of each reactor is controlled by a back pressure valve to ensure that the pressure inside the reactor is constant. After the reaction is completed, the slurry is continuously discharged and enters the buffer tank 26 through a pressure reducing valve, completing the continuous mineralization production.

[0075] In one embodiment of the present invention, the operating parameters of the three-phase reactor 22 are as follows: the reaction temperature is controlled at 60-100℃, and segmented temperature control can be achieved through a heating jacket, with a temperature control accuracy of ±1℃; the reaction pressure is controlled at 0.5-3.0MPa, with a pressure fluctuation range of ±0.05MPa, and the CO2 gas pressure is 0.1-0.2MPa higher than the reaction pressure; the mechanical stirrer (batch type) rotates at 100-300rpm, and the ratio of the impeller diameter to the vessel diameter is 0.5-0.6; the residence time per stage of the continuous tubular reactor is 5-10min, and the total reaction time is 20-40min.

[0076] In one embodiment of the present invention, the CO2 supplied by the carbon dioxide storage tank 23 has a purity of ≥90%, and can be industrial-grade liquid CO2 or purified high-concentration CO2. As an alternative, CO2 can also be derived from flue gas from coal-fired boilers or tail gas from coal chemical plants. The clean flue gas obtained after desulfurization, denitrification, and dust removal from the coal-fired boiler (CO2 volume concentration of approximately 12%-15%, with the remainder mainly consisting of N2 and small amounts of O2 and water vapor) is introduced into the pressurized reactor via a booster fan. Since the partial pressure of CO2 in the flue gas from the coal-fired boiler is relatively low, it is necessary to appropriately increase the operating pressure of the three-phase reactor 22 (e.g., 0.5-1.5 MPa) and extend the reaction time to ensure mineralization efficiency. The CO2 tail gas obtained after desulfurization and decarbonization using the low-temperature methanol washing process in coal chemical plants can achieve a purity of over 80%, with the remaining components being H2, N2, and trace amounts of methanol. This gas source can be directly compressed and introduced into the reactor without further purification. When using the aforementioned low-concentration industrial flue gas, the aeration time can be controlled by online monitoring of the pH value or the CO2 concentration in the tail gas within the reactor. The reaction is considered to have ended when the pH of the slurry drops to neutral (6.5-7.5) and remains stable for more than 30 minutes.

[0077] In one embodiment of the present invention, the buffer tank 26 has an effective volume capable of storing 3 hours' worth of three-phase slurry production. The working pressure is atmospheric pressure, and a level sensor is installed inside the tank to prevent slurry overflow. The three-phase slurry conveyor 27 has a conveying speed of 1-2 m / s and uses a wear-resistant conveyor belt to prevent slurry abrasion of the equipment. The three-phase slurry storage tank 28 adopts a double-layer insulation structure, maintaining the internal temperature at 20-35℃. It is equipped with a low-speed agitator (10-20 rpm) to prevent sedimentation and agglomeration of the slurry after mineralization. It is equipped with an online pH meter with a measurement range of 5.0-14.0 and a measurement accuracy of ±0.1; and an online conductivity meter with a measurement range of 0-2000 μS / cm and a measurement accuracy of ±1%.

[0078] The intelligent control system links all equipment throughout the process, achieving automated closed-loop control of feeding, mixing, reaction, and pressure relief, ensuring continuous and stable system operation. The intelligent control system features overpressure, overtemperature, and mixing fault interlock protection, and can adaptively update the slurry calculation model coefficients based on measured production data, achieving closed-loop control of batching, mixing, reaction, and safety interlocks.

[0079] The intelligent control system adopts a DCS or PLC control system, and is equipped with a data acquisition module, a logic control module, an interlock protection module, and a model update module. These modules are electrically connected to all equipment in the raw material supply unit, the primary slurry preparation unit, the secondary slurry preparation unit, and the CO2 mineralization reaction unit, as well as online detection instruments (online viscometers, densitometers, pH meters, etc.) to ensure real-time data acquisition and accurate command issuance. A closed-loop control mode combining feedforward and feedback control is adopted, linking all unit equipment throughout the process. In the batching stage: given the particle size of coal gangue and fly ash, and the moisture content of coal slime, the feedforward control of the feeding speed of coal gangue feeder 3, fly ash feeder 6, and coal slime feeder 17 is based on the optimal proportion output by the batching prediction software, controlling the material addition amount. In the slurry preparation stage: online monitoring data from primary mixing tank 7 and secondary mixing tank 11 is received and compared with the software prediction parameters, and the operating status of process water pump 9, process water pump 19, and additive supply pump 14 is adjusted to ensure the slurry rheological properties meet the standards. In the mineralization reaction stage: the temperature, pressure, pH value, and conductivity of the three-phase reactor 22 are monitored in real time, and the heating jacket temperature, CO2 aeration rate, and stirring speed are automatically adjusted to determine the reaction endpoint. In the discharge stage: the operation of pressure relief valve 25 and three-phase slurry conveyor 27 is controlled to ensure stable transportation and safe storage of the three-phase slurry.

[0080] Interlocking protection function: Triple interlocking protection is set for the high pressure and high temperature conditions of the CO2 mineralization reaction unit to ensure system safety: Overpressure interlock: When the pressure inside the three-phase reactor 22 is >3.2MPa, CO2 gas intake is stopped, the emergency pressure relief valve of the reactor is automatically opened, and an alarm signal is issued at the same time; Overtemperature interlock: When the temperature inside the three-phase reactor 22 is >130℃, the heating jacket is automatically stopped, and the cooling water circulation is started until the temperature drops to the preset range; Stirring failure interlock: When the agitator of the primary stirring tank 7, the secondary stirring tank 11, and the three-phase reactor 22 has abnormal current (deviation >±10%) or zero speed, the feeding, water intake, and gas intake operations of the corresponding unit are automatically stopped, and an alarm signal is issued to avoid the stirring paddle jamming due to problems such as slurry agglomeration and foreign objects.

[0081] The gradation and batching unit incorporates calculation software based on the Andreasen closest packing model, which can quickly predict the slurry density (kg / m³) based on the particle size, moisture content, and other physical properties of solid wastes such as coal gangue, fly ash, and coal slime. 3The software calculates rheological parameters such as average particle size (mm), rotational viscosity (Pa·s), and yield stress (Pa), and further calculates pressure drop per unit length (Pa / m), total pipeline pressure drop (bar), and estimated pumping power (kW). The gradation and batching prediction software uses slurry concentration, solid waste proportions, and particle size as input parameters, outputting slurry density, viscosity, yield stress, and other rheological parameters, and solving for the optimal gradation. Embedded within the entire system, the gradation and batching prediction software is the core module for achieving the densest packing of solid waste particles and improving the rheological properties of three-phase slurry. Input parameters include: slurry mass concentration (%), coal gangue mass ratio (%), average coal gangue particle size (mm), fly ash mass ratio (%), average fly ash particle size (mm), coal slime mass ratio (%), coal slime moisture content (%), and additive dosage (% of dry basis). Output parameters include: slurry density (kg / m³). 3 ), weighted average particle size (mm), rotational viscosity (Pa·s), and yield stress (Pa); based on the above calculation results, further equipment selection is performed by inputting pipe diameter (m), pipe length (m), and three-phase conveying speed (m / s) to calculate the output flow rate (m³ / s). 3 The optimal gradation is determined by calculating the total pressure drop (bar) and pump power (kW) of the solid waste particles. With the goal of achieving the highest solid particle density and optimal slurry rheological properties, mathematical modeling is used to find the optimal mix proportion that minimizes the deviation between the measured particle size distribution and the theoretical curve. The outputs slurry density, average particle size, rotational viscosity, and yield stress under the optimal mix proportion. Using the output density and viscosity as inputs, combined with the pipe diameter, length, and conveying speed, the flow rate, total pressure drop, and pump power are calculated. The optimal gradation scheme is then determined by comparing the results.

[0082] In one embodiment of the present invention, coal gangue and coal slime from a coal mine and fly ash from a power plant are used as raw materials. The average particle size of the coal gangue is 1-10 mm, the average particle size of the fly ash is 0.01-0.1 mm, and the moisture content of the coal slime is 15-25%. The coal gangue is crushed and screened to 1-5 mm, the fly ash is sorted and decarbonized (particle size 0.03 mm), and the coal slime is mechanically dehydrated to a moisture content of 20%. The physical property parameters of the three raw materials are entered into the gradation and batching prediction software.

[0083] The batching prediction software, inputting solid waste properties, target slurry concentration of 75%, slurry conveying rate of 280 t / h, and conveying distance of 100 m, calculates the optimal dry basis mass ratio as coal gangue: fly ash: coal slime = 60:30:10, with 1.0% sodium sulfate stabilizer added by dry basis mass. The resulting slurry density is 1757 kg / m³. 3 The average particle size is 1.822 mm, the rotational viscosity is 2.428 Pa·s, and the yield stress is 36.49 Pa.

[0084] According to the above proportions, the coal gangue feeder 3, fly ash feeder 6, and coal slime feeder 17 are used for precise feeding. The mixture is then processed in a primary mixing tank 7 and a secondary mixing tank 11 to complete the slurry preparation. Subsequently, it is sent to a three-phase reactor 22, where CO2 is introduced at a temperature of 90℃ and a pressure of 1.2MPa to complete the mineralization reaction. The reaction ends when the pH stabilizes at 6-9.

[0085] In contrast, if we disregard gradation and mineralization and use conventional methods to prepare slurry using only coal gangue, the performance prediction values ​​of the two slurries are compared in Table 1.

[0086] Table 1 Performance Predictions

[0087] It is evident that, compared to conventional gangue slurry, the three-phase slurry has a higher density (5.7%), smaller average particle size, and a more compact slurry, allowing for the transport of more coal-based solid waste materials while maintaining the same flow rate. However, its rotational viscosity is also lower (18.2%), resulting in a 13.7% reduction in pressure drop per unit length. Ultimately, this reduces the pump power required to transport the slurry from 62.25kW to 53.73kW, minimizing power consumption due to overcoming viscous transport forces.

[0088] Figure 2 The comparison between measured and predicted values ​​of the rotational viscosity of three-phase slurries with different mass concentrations reveals an average absolute percentage error of 12.60% and a coefficient of determination R0. 2 =0.95, which proves the high accuracy of the gradation and batching prediction software.

[0089] Coal slime, acting as a rheology modifier, transforms the slurry from a dilatant to a pseudoplastic fluid. Without coal slime, pure coal gangue slurry exhibits obvious shear-thickening dilatant characteristics, easily segregating upon standing, with large viscosity fluctuations. Furthermore, the higher the transport speed, the higher the viscosity, leading to significant resistance during long-distance transport. When coal slime (containing 20% ​​water, accounting for 5%-15% of the slurry's dry basis mass) is added, the mixed slurry transforms into a shear-thinning pseudoplastic fluid. This means that upon standing, the viscosity is moderate and segregation is minimal (the viscosity of the coal slime binds the coal gangue and fly ash particles together). During transport, the viscosity decreases, and the higher the transport speed, the lower the viscosity. The slurry performance becomes more ideal, reducing energy consumption by 18%-22% under the same transport conditions. The resulting three-phase slurry is suitable for the transport requirements of underground filling. Figure 3 This relates to the mass ratio of coal slime blending with the viscosity of the three-phase slurry. As the coal slime blending rate increases, the slurry viscosity gradually decreases, and the corresponding pump delivery power also decreases.

Claims

1. A method for preparing a three-phase slurry for carbon dioxide mineralization and synergistic solid waste gradation, characterized in that, include: Step 1: Pre-treatment and precise supply of coal-based solid waste raw materials; Step 2: Intelligent prediction of gradation and batching; Step 3: Prepare the primary slurry; Step 4: Prepare secondary slurry; Step 5: Pressurized CO2 three-phase mineralization reaction; Step 6: Depressurization, stabilization, and storage of the mineralized slurry.

2. The method for preparing a three-phase slurry for carbon dioxide mineralization and synergistic solid waste gradation according to claim 1, characterized in that, Step 1 includes coal gangue pretreatment and feeding, fly ash pretreatment and feeding, and coal slime pretreatment and feeding. Step 2 includes: Step 2.1: Input raw material physical property parameters; The detection parameters of the pretreated raw materials are entered into the gradation and batching prediction software; Step 2.2: Solving for the closest packing ratio; With the goal of achieving the highest packing density of solid waste particles and the best rheological properties of slurry, the optimal dry basis mass ratio that minimizes the deviation between the measured particle size distribution and the theoretical curve was calculated. Step 2.3: Prediction of slurry properties and transport parameters; The software outputs the core parameters of the slurry under the optimal ratio, and completes the verification of coal-based solid waste ratio and equipment selection. Step 2.4: Issuance of hardware control commands; Based on the prediction results, the intelligent control system issues operating parameter commands to all hardware units.

3. The method for preparing a three-phase slurry for carbon dioxide mineralization and synergistic solid waste gradation according to claim 1, characterized in that, Step 3 includes: Step 3.1: Add materials and process water; The coal gangue feeder (3) and the fly ash feeder (6) deliver raw materials to the primary mixing tank (7) according to the optimal ratio; the No. 1 process water pump (9) sends the water in the No. 1 process water tank (8) into the primary mixing tank (7) through the flow metering valve according to the preset water-solid ratio. Step 3.2: Mix using dual-shaft counter-rotating stirring; Step 3.3: Online monitoring and parameter feedback control; Real-time acquisition of slurry rotational viscosity and density data; data transmission to intelligent control system and comparison with predicted parameters: if the deviation exceeds the allowable range, automatically adjust the flow rate of process water pump (9) and adjust the amount of process water added until the parameters meet the standard; Step 3.4: Determining the end point of stirring; If the preset stirring termination condition is met, one slurry preparation is completed; if the preset stirring termination condition is not met, stirring continues.

4. The method for preparing a three-phase slurry for carbon dioxide mineralization and synergistic solid waste gradation according to claim 1, characterized in that, Step 4 includes: Step 4.1: Add slurry and coal slime in one step; The primary slurry is fed into the secondary mixing tank (11) via the primary slurry conveyor (10); the coal slime feeder (17) feeds coal slime into the secondary mixing tank (11) as a rheology modifier according to a preset amount; Step 4.2: Dissolving and adding additives; Process water pump No. 3 (20) sends water from process water tank No. 2 (18) into additive dissolving tank (13); additives from additive storage tank (12) are added to dissolving tank in proportion and stirred to dissolve; additive supply pump (14) sends the prepared additive solution into secondary stirring tank 11. Step 4.3: Segmented high-shear mixing and homogenization; Start the high-shear mixer and mix in two stages: a high-shear dispersion stage and a low-speed homogenization stage. Step 4.4: Online monitoring and parameter feedback control; Real-time collection of slurry parameters and comparison with predicted values: If the viscosity is too high or the density is too high, the No. 2 process water pump (19) is automatically started to add process water and reduce the slurry concentration; If the viscosity is too low or the density is too small, the flow rate of the slurry conveyor (10) and the additive feed pump (14) will be automatically increased once to replenish the slurry and additives. Step 4.5: Secondary slurry delivery; After the slurry parameters meet the standards, the secondary slurry is transported to the three-phase reactor (22) via the secondary slurry conveyor (21) and enters the mineralization reaction stage.

5. The method for preparing a three-phase slurry for carbon dioxide mineralization and synergistic solid waste gradation according to claim 1, characterized in that, Step 5 includes: Step 5.1, Reactor feeding; Choose between batch pressurized reactors or continuous pressurized reactors based on production scale; Step 5.2: Setting reaction conditions and introducing CO2; Start the heating jacket to raise the temperature inside the reactor to the set range; adjust the pressure reducing valve (24) to introduce CO2 into the reactor and control the reaction pressure at the set value. Step 5.3: Real-time monitoring of the reaction process; Real-time acquisition of reaction parameters and transmission to the intelligent control system; Step 5.4: Joint determination of the reaction endpoint; If the rate of change of pH and conductivity meets the reaction termination condition, the mineralization reaction is complete; if the rate of change of pH and conductivity does not meet the reaction termination condition, the mineralization reaction continues. Step 5.5: Reaction cessation and material discharge preparation; Heating and CO2 intake are stopped, and the slurry after reaction is continuously discharged through a pressure reducing and regulating valve; Step 6 includes: Step 6.1: Depressurize and stabilize the buffer tank; The mineralized three-phase slurry is fed into a buffer tank (26) and pressure stabilization is completed under normal pressure. Step 6.2, Three-phase slurry delivery; The three-phase slurry conveyor (27) delivers the pressure-stabilized slurry to the three-phase slurry storage tank (28). Step 6.3: Store in an insulated environment to prevent sedimentation; Maintain the temperature inside the tank within the set range, start the low-speed agitator, and monitor the pH value of the slurry in real time.

6. A three-phase slurry preparation system for carbon dioxide mineralization and synergistic solid waste gradation, characterized in that, The three-phase slurry preparation method for carbon dioxide mineralization synergistic solid waste gradation according to any one of claims 1-5 includes a raw material storage and supply unit, a primary slurry preparation unit, a secondary slurry preparation unit, and a CO2 mineralization reaction unit connected in sequence. The raw material storage and supply unit, the primary slurry preparation unit, the secondary slurry preparation unit, and the CO2 mineralization reaction unit are respectively connected to an intelligent control system, and the intelligent control system is connected to a gradation and batching unit.

7. The three-phase slurry preparation system for carbon dioxide mineralization and synergistic solid waste gradation according to claim 6, characterized in that, The raw material storage and supply unit includes a coal gangue silo (1), a coal gangue feeder (2), and a coal gangue feeder (3) connected in sequence. The bottom of the coal gangue silo (1) is equipped with an anti-blocking device, and the coal gangue feeder (3) is equipped with a weight weighing scale. The raw material storage and supply unit also includes a fly ash silo (4), a fly ash feeder (5), and a fly ash feeder (6) connected in sequence. The top of the fly ash silo (4) is equipped with a pulse bag dust collector. The raw material storage and supply unit also includes a coal slime silo (15), a coal slime feeder (16), and a coal slime feeder (17) connected in sequence. The coal slime silo (15) is equipped with a stirrer. The coal gangue feeder (3) and the fly ash feeder (6) are connected to the primary slurry preparation unit, and the coal slime feeder (17) is connected to the secondary slurry preparation unit.

8. The three-phase slurry preparation system for carbon dioxide mineralization and synergistic solid waste gradation according to claim 6, characterized in that, The primary slurry preparation unit includes a primary mixing tank (7), which is connected to a primary process water tank (8) via a primary process water pump (9). The primary mixing tank (7) is also connected to a coal gangue feeder (3) and a fly ash feeder (6). An online viscometer and an online density meter are installed inside the primary mixing tank (7), and a flow metering valve is installed between the primary mixing tank (7) and the primary process water pump (9).

9. The three-phase slurry preparation system for carbon dioxide mineralization and synergistic solid waste gradation according to claim 6, characterized in that, The secondary slurry preparation unit includes a secondary mixing tank (11), which is connected to the primary mixing tank (7) via a primary slurry conveyor (10). The secondary mixing tank (11) is connected to a coal slime feeder (17). The secondary mixing tank (11) is connected to an additive dissolving tank (13) via an additive feeding pump (14). The additive dissolving tank (13) is connected to an additive storage tank (12). The secondary mixing tank (11) is connected to a second process water tank (18) via a second process water pump (19). The second process water tank (18) is connected to the additive dissolving tank (13) via a third process water pump (20).

10. The three-phase slurry preparation system for carbon dioxide mineralization and synergistic solid waste gradation according to claim 6, characterized in that, The CO2 mineralization reaction unit includes a three-phase reactor (22), which is connected to a secondary stirring tank (11) via a secondary slurry conveyor (21) and is connected to a carbon dioxide storage tank (23) via a pressure reducing valve (24); the three-phase reactor (22) is connected to a buffer tank (26) via a pressure relief valve (25); the buffer tank (26) is connected to a three-phase slurry storage tank (28) via a three-phase slurry conveyor (27); the three-phase reactor (22) is equipped with an online pH meter, an online conductivity meter, a temperature sensor, and a pressure sensor; the three-phase reactor (22) is configured as a batch pressurized reactor or a continuous pressurized reactor.

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