High-stability paste filling slurry preparation and long-distance delivery method

Abstract

The application discloses a high-stability paste filling slurry preparation and long-distance conveying method and belongs to the technical field of mine filling engineering. The coarse and fine particle classification screening and activation pretreatment are carried out on the full tailings and coal gangue solid waste, the gelling material and the composite flow stabilizing and retarding modifier are accurately proportioned, the high-stability, low-bleeding, high-flow and plastic-type paste slurry is prepared through a three-stage process of initial mixing, precise mixing and homogenization curing, and meanwhile, the long-distance segmented pressure stabilization, pipeline self-adaptive lubrication and pressure-flow closed-loop regulation and control conveying process are matched, so that the problems in the long-distance conveying process of the slurry, such as segregation, layering, pipe blockage, pump blockage and early initial setting, are effectively solved. The paste slurry has zero bleeding, does not segregate, has strong structural stability, can realize more than 1000m long-distance, high-fall continuous and stable conveying, the conveying resistance is reduced by more than 20%, the filling and consolidation strength is uniform and controllable, the solid waste utilization rate is high, the energy consumption is low, the safety is high, and the paste filling operation is suitable for various metal mines and underground goaf areas of coal mines.

Description

Technical Field

[0001] This invention relates to the fields of mine backfilling, solid waste resource utilization and fluid transportation technology, specifically to an integrated method for preparing and transporting a highly stable paste-like backfill slurry over long distances. Background Technology

[0002] Cemented backfilling in mines is a core green mining technology for solving problems such as underground goaf collapse, surface subsidence, tailings pollution, and coal gangue solid waste accumulation. Compared with traditional hydraulic backfilling and dry backfilling, it has the advantages of high consolidation strength, good filling density, and excellent environmental protection, and has been widely used in metal mine and coal mine mining projects.

[0003] Currently, existing paste-filled slurry preparation and transportation technologies still face several industry bottlenecks: First, traditional slurry raw materials are not graded and activated, resulting in a mixture of coarse and fine particles from tailings and coal gangue, poor gradation continuity, and uneven internal structure of the prepared slurry. During settling and transportation, aggregate settling, slurry bleeding, and segregation are highly likely to occur, leading to extremely poor slurry stability. Second, conventional single admixtures can only achieve a single function of retarding or water reduction, failing to simultaneously address slurry fluidity, plasticity retention, and structural stability. They are prone to losing fluidity within a short period. First, it cannot meet the time requirements of long-distance transportation; second, traditional mixing processes are mostly simple single mixing, resulting in low material mixing uniformity and the presence of air bubbles and loose pores in the slurry, further reducing the overall stability of the slurry; third, during long-distance transportation, pipeline pressure fluctuates greatly and resistance loss along the route is uneven. High-drop sections are prone to rapid slurry solidification, pipe blockage, and pipe bursts, while flat sections are prone to siltation and blockage. Moreover, the lack of a dynamic control mechanism leads to poor continuity and high failure rate in ultra-long-distance transportation, which seriously restricts the filling efficiency of deep and ultra-deep mines.

[0004] In existing technologies, most solutions focus only on optimizing slurry formulations or improving single conveying equipment, failing to achieve integrated adaptation between stable slurry preparation and long-distance stable conveying. This fails to fundamentally solve core problems such as pipe blockage, segregation, and uneven strength in paste filling under ultra-long distances and complex working conditions. Therefore, there is an urgent need to develop a highly stable paste filling slurry preparation and long-distance conveying method to achieve homogeneous and stable slurry, continuous long-distance low-resistance conveying, and adaptability to large-scale filling operations in deep mines. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide a method for preparing and transporting high-stability paste filling slurry over long distances. This method solves the technical problems of poor stability, easy segregation and bleeding, short flow retention period, high resistance during long-distance transport, frequent pipe blockage, and poor transport stability of existing paste filling slurries. It achieves high homogeneity, high stability, long plastic retention, low resistance, and continuous transport over ultra-long distances, thereby improving the efficiency and quality of mine filling operations.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing and transporting a highly stable paste-like filling slurry over long distances, comprising four core steps: raw material classification and pretreatment, precise proportioning and batching, three-stage gradient stirring and maturation, and long-distance dynamic pressure-stabilized transportation. The specific process is as follows:

[0007] S1. Raw material classification and activation pretreatment

[0008] The raw materials include mine tailings, coal gangue solid waste, silicate cement, fly ash, modified composite admixtures, and mixing water. The solid waste raw materials are pre-treated by classification: the coal gangue is crushed and screened to obtain coarse aggregate of 3-8mm, fine aggregate of 0.075-3mm, and micro powder of less than 0.075mm; the tailings are thickened, dewatered, and screened to remove impurities, and the moisture content is controlled to ≤18%; the fly ash and coal gangue micro powder are mechanically activated by ball milling for 15-20 minutes to improve the activity and filling density of the materials and optimize the continuity of particle size distribution.

[0009] S2, Precise ingredient ratio

[0010] The raw materials are precisely proportioned by weight as follows: 45-55 parts coarse aggregate, 15-20 parts fine aggregate, 8-12 parts activated micro-powder, 8-12 parts silicate cement, 5-10 parts activated fly ash, 0.3-0.8 parts composite modified admixture, and 25-32 parts mixing water. The composite modified admixture is composed of microencapsulated retarder, polycarboxylate superplasticizer, nano-silica flow stabilizer, and polypropylene short fiber in a ratio of 3:4:2:1. This proportion forms a continuous graded packing structure, significantly improving the slurry's density and structural stability.

[0011] S3. Three-stage gradient stirring and maturation to prepare highly stable slurry.

[0012] A segmented gradient mixing process is adopted to avoid material agglomeration and uneven mixing.

[0013] (1) Initial mixing stage: Coarse aggregate, fine aggregate and activated micro powder are put into the mixing equipment and dry-mixed for 60-90 seconds to achieve uniform mixing of solid aggregate;

[0014] (2) Fine mixing stage: Add cement, activated fly ash and 70% mixing water, stir for 120-180s to form a uniform slurry base, then add composite modified admixture and the remaining 30% mixing water, and continue stirring for 90-120s to achieve uniform dispersion of admixture;

[0015] (3) Homogenization and maturation stage: low-speed constant temperature stirring and maturation for 3-5 minutes, stirring speed controlled at 30-40 r / min, to eliminate air bubbles inside the slurry, optimize the rheological properties of the slurry, and prepare a paste-filled slurry with no bleeding, no segregation, and high plasticity. The slump of the slurry is controlled at 220-260 mm, and the initial setting time is ≥6 h to meet the time requirements for long-distance transportation.

[0016] S4, Long-distance dynamic pressure-stabilized closed-loop conveying

[0017] The prepared high-stability paste slurry is transported over long distances through a dedicated pipeline, employing a segmented dynamic pressure stabilization, adaptive lubrication, and closed-loop pressure and flow control process.

[0018] (1) Pipeline pretreatment: Before transportation, use clean water + a small amount of lubricating slurry to lubricate the pipe, reduce the initial resistance of the pipeline and avoid dry friction blockage;

[0019] (2) Segmented pressure-stabilized transportation: According to the transportation distance and pipeline drop, the long-distance pipeline is divided into flat section, steep slope section and vertical drop section, and the corresponding transportation pressure is set respectively. The basic transportation pressure is controlled at 4 to 8 MPa. A pressure-stabilizing buffer device is added to the high drop section to suppress sudden pressure changes.

[0020] (3) Dynamic closed-loop control: Real-time monitoring of pipeline flow rate, pressure, and slurry flow rate data, and linkage with frequency conversion control of the conveying pump. When the pressure fluctuation exceeds ±0.5MPa, the pump speed and conveying flow rate are automatically adjusted to maintain uniform and steady-state conveying of slurry.

[0021] (4) End pressure stabilization and unloading: A buffer flow stabilization device is set at the end of the conveying to avoid high-speed impact of slurry causing aggregate separation and to ensure that the filling slurry is evenly fed into the mold.

[0022] Preferably, the activated fly ash and coal gangue powder are screened through a 300-mesh sieve, with a particle size uniformity error of ≤5%; the polypropylene short fibers are 3-6 mm in length, which effectively improves the slurry's crack resistance and segregation resistance.

[0023] Preferably, the slurry has a bleeding rate of 0 after maturation and a fluidity loss of ≤5% after 2 hours, which can meet the requirements for continuous conveying over an ultra-long distance of 1500m.

[0024] Preferably, during long-distance transportation, the pipeline friction resistance is reduced by 20% to 25% compared to conventional paste slurry, with no pipe blockage or siltation, and the transportation stability is greatly improved.

[0025] Beneficial effects

[0026] 1. This invention adopts a solid waste graded activation pretreatment + continuous stage distribution ratio design to optimize the internal stacking structure of the slurry, and solve the problems of segregation, bleeding and aggregate sedimentation of paste slurry from the root. The static and dynamic stability of the slurry is greatly improved, with zero bleeding and low fluidity loss, and the plastic retention time meets the needs of ultra-long distance transportation.

[0027] 2. The three-stage gradient mixing and maturation process achieves precise mixing of materials and uniform dispersion of additives, eliminates internal defects in the slurry, significantly improves the homogeneity and rheological properties of the slurry, and effectively reduces conveying resistance.

[0028] 3. Composite modified admixtures have multiple functions such as water reduction, retardation, flow stabilization and crack resistance, breaking through the performance limitations of traditional single admixtures and adapting to the aging and stability requirements of long-distance transportation.

[0029] 4. The long-distance segmented dynamic pressure stabilization + pressure and flow frequency conversion closed-loop control process is an integrated control method that is not disclosed in existing technologies. It can adapt to complex pipelines, high drop, and ultra-long distance working conditions, effectively suppress pressure fluctuations, pipeline siltation, and pipe blockage and bursting problems, significantly improve the continuity and safety of transportation, and the transportation distance exceeds 1500m, making it suitable for deep and ultra-deep mine filling.

[0030] 5. This invention makes extensive use of coal gangue and tailings, resulting in high solid waste utilization, environmental friendliness, and low cost. The filling body exhibits uniform consolidation strength, high density, and excellent filling quality, making it suitable for large-scale mine filling operations and possessing extremely high promotional value. Attached Figure Description

[0031] Figure 1 is a flow chart of the preparation and long-distance transportation process of the paste filling slurry of the present invention;

[0032] Figure 2 is a schematic diagram of the structure of the long-distance stable closed-loop conveying system of the present invention. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to specific embodiments, so that those skilled in the art can understand it.

[0034] Example 1

[0035] A method for preparing and transporting a highly stable paste-like filling slurry over long distances, comprising the following specific steps:

[0036] S1. Raw material pretreatment: Select coal gangue from coal mines, crush and screen to obtain 5-8mm coarse aggregate, 0.1-3mm fine aggregate, and micro powder below 0.075mm; thicken and dewater the tailings to a moisture content of 16%; ball mill and activate fly ash and coal gangue micro powder for 18 minutes, and screen with 300 mesh for later use.

[0037] S2. Raw material proportions (parts by weight): 50 parts coarse aggregate, 18 parts fine aggregate, 10 parts activated micro powder, 10 parts silicate cement, 8 parts activated fly ash, 0.5 parts composite modified admixture, and 29 parts mixing water.

[0038] S3, Three-stage mixing: Dry mixing for 80s → Add 70% water, cement, and fly ash and mix for 150s → Add admixtures and remaining water and mix for 100s → Low-speed maturation for 4min to obtain a paste slurry with a slump of 240mm, an initial setting time of 6.5h, zero bleeding, and no segregation.

[0039] S4. Long-distance transportation: The transportation distance is 1200m, the pipeline is segmented and pressure is stabilized, the basic transportation pressure is 6MPa, the pressure and flow are controlled in real time with closed loop, the transportation is continuous throughout the process without pipe blockage or siltation, the transportation efficiency is stable, the strength of the filling and consolidation after 28 days can reach 4.2MPa, and the filling density meets the standards.

[0040] Example 2

[0041] S1. Raw material pretreatment is the same as in Example 1.

[0042] S2. Raw material proportions (parts by weight): 48 parts coarse aggregate, 16 parts fine aggregate, 9 parts activated micro powder, 11 parts silicate cement, 9 parts activated fly ash, 0.6 parts composite modified admixture, and 28 parts mixing water.

[0043] S3, the three-stage mixing process parameters are the same as in Example 1, the prepared slurry slump is 235mm, the fluidity loss is ≤3% after 2h, and the initial setting time is 7h.

[0044] S4, with a conveying distance of 1500m, is designed for complex pipeline conditions with high drops. It adopts dynamic pressure regulation and control, ensuring stable conveying throughout the entire process without sudden pressure changes or pipe blockage. It also features low resistance along the pipeline and excellent uniformity of filling strength.

[0045] Comparative example (traditional process)

[0046] Using traditional single-mixing, conventional admixtures, and pressure-stabilized conveying processes, under the same raw material ratio and conveying conditions, the slurry bleeding rate is 4.2%, aggregate settling and pipeline siltation occur after conveying 1000m, pressure fluctuations are large, the pipe blockage failure rate is high, the slurry fluidity is lost quickly, it is impossible to achieve stable conveying over ultra-long distances, and the filling body has uneven strength and poor compaction.

Claims

1. A method for preparing a highly stable paste-like filling slurry, characterized in that, Includes the following steps: S1. Raw material classification and activation pretreatment: Classification, screening, dehydration and impurity removal and mechanical activation treatment of mine solid waste aggregates and cementitious powder raw materials are carried out to optimize the particle size distribution and surface activity of raw materials, remove impurities and excessive moisture, and ensure uniform particle size and stable performance of raw materials. S2. Precise compounding: According to the preset weight ratio, the graded and activated coarse aggregate, fine aggregate, powder, cementitious material, active admixture, composite modifier and mixing water are precisely mixed to form a continuous graded stacking system; the composite modifier is a multi-component compound system with functions of water reduction, retardation, flow stabilization, anti-segregation and anti-cracking. S3. Segmented gradient homogenization and maturation preparation: A three-stage mixing process is adopted, which includes dry initial mixing, wet graded fine mixing, and low-speed constant temperature maturation. Raw materials and additives are added step by step to avoid material agglomeration, local enrichment of additives, and gas defects in the slurry. This process produces a highly stable paste filling slurry with zero bleeding, low fluidity loss, and long plasticity retention.

2. The method for preparing a high-stability paste-like filling slurry according to claim 1, characterized in that, The solid waste from mining and processing mentioned in S1 (one or more of tailings, coal gangue, waste rock, and crushed stone) and the cementitious powder raw materials include any one or more of silicate cement, fly ash, mineral powder, and coal gangue powder. The grading standard for solid waste aggregates is as follows: coarse aggregate with a particle size of 3-8mm, fine aggregate with a particle size of 0.075-3mm, and powder with a particle size of ≤0.075mm; the moisture content of the whole tailings raw material after dewatering is controlled to ≤18%, and the powder raw material is homogenized by passing it through a 280-320 mesh sieve after being activated by ball milling for 15-20 minutes.

3. The method for preparing a high-stability paste-like filling slurry according to claim 1, characterized in that, The raw materials in S2 are proportioned by weight as follows: 45-55 parts coarse aggregate, 15-20 parts fine aggregate, 8-12 parts activated micro powder, 8-12 parts cementitious material, 5-10 parts active admixture, 0.3-0.8 parts composite modified additive, and 25-32 parts mixing water. The composite modified admixture is composed of microcapsule retarder, polycarboxylate superplasticizer, nano silica flow stabilizer, and polypropylene short fiber in a mass ratio of 2.5-3.5: 3.5-4.5: 1.5-2.5: 0.5-1.5, preferably 3:4:2:

1.

4. The method for preparing a high-stability paste filling slurry according to claim 3, characterized in that, The polypropylene short fibers are 3-6 mm in length and 15-25 μm in diameter, which can effectively improve the anti-settling, anti-segregation, and anti-cracking properties of the paste slurry.

5. The method for preparing a high-stability paste-like filling slurry according to claim 1, characterized in that, S3 specifically includes: (1) Initial mixing stage of dry materials: Dry mixing of coarse aggregate, fine aggregate and activated micro powder for 60-90s to achieve uniform mixing of solid aggregate without segregation; (2) Wet mixing stage: First, add 70% mixing water, cementitious materials and active admixtures and stir for 120-180s to form a homogeneous slurry base. Then add composite modified admixtures and the remaining 30% mixing water and continue stirring for 90-120s to ensure that the admixtures are evenly dispersed. (3) Low-speed maturation stage: Stir and mature at a low speed of 30-40 r / min and at room temperature for 3-5 min to eliminate air bubbles and structural defects inside the slurry and optimize the rheological properties of the slurry.

6. The method for preparing a high-stability paste-like filling slurry according to claim 1, characterized in that, The performance parameters of the paste filling slurry prepared by S3 meet the following requirements: slump 220~260mm, initial setting time ≥6h, fluidity loss ≤5% after 2h, static bleeding rate 0, and consolidation strength ≥4.0MPa after 28d, which is suitable for ultra-long distance transportation and aging requirements.

7. A method for long-distance transport of high-stability paste filling slurry according to any one of claims 1-6, characterized in that, Includes the following steps: Long-distance adaptive pressure-stabilized closed-loop conveying: The conveying pipeline is pre-treated and lubricated. The pipeline is segmented and zoned for pressure control according to the conveying distance, pipeline slope, and vertical drop. The pipeline conveying parameters are collected in real time and dynamically adjusted by frequency conversion closed loop. The conveying is adaptive to the pipeline conditions. Combined with the end flow stabilization buffer unloading, it realizes long-distance continuous and stable conveying of paste slurry without segregation, siltation, or pipe blockage.

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