A high-chlorine coal jigging separation and high-quality gradient step water cycle combined system

Abstract

The application relates to the technical field of coal washing and coal chemical water treatment, and discloses a high-chlorine coal jigging separation and clean coal leaching and dechlorination multi-quality cascade water circulation combined system which comprises a raw coal pretreatment unit, a jigging separation unit, a clean coal leaching and dechlorination unit, a coal slime dewatering and recovery unit and a high-chlorine wastewater treatment workshop. When the system is running, the raw coal pretreatment and jigging separation unit receives mine area domestic sewage to perform raw coal conditioning and layered separation, low-chlorine wastewater is closed-loop circulated in the jigging separation unit after sedimentation, the clean coal leaching and dechlorination unit receives a high-clean water source mixed by urban reclaimed water and regenerated fresh water, performs multi-stage countercurrent leaching on clean coal, high-chlorine leaching wastewater is subjected to solid-liquid separation through the coal slime dewatering and recovery unit, and then is subjected to membrane separation desalination and evaporation crystallization in the high-chlorine wastewater treatment workshop. The application realizes physical isolation of low-chlorine water and high-chlorine water circulation networks, avoids cross contamination of wastewater, reduces end desalination load, realizes multi-quality cascade utilization of system water and zero liquid discharge.

Description

Technical Field

[0001] This application relates to the field of coal washing and coal chemical water treatment technology, specifically a combined system for high-chlorine coal jigging and fine coal leaching dechlorination and graded water circulation. Background Technology

[0002] In some coal mining areas in my country, there is high-chloride thermal coal containing water-soluble chloride salts. This type of coal easily releases corrosive gases when burned directly. Therefore, it usually needs to be treated with a combination of sorting and leaching to reduce ash and dechlorinate before industrial application. In the existing combined production process of high-chloride coal sorting and dechlorination, the water circulation system generally has the following process defects: Coal sorting and leaching dechlorination processes require a large amount of water. Currently, conventional processes heavily rely on fresh clean water as the system's water source, resulting in a high consumption of fresh water in industrial production. At the same time, unconventional water resources such as domestic sewage and urban wastewater generated in and around the mining area have not been matched to the water quality requirements of each stage of the process, resulting in a low comprehensive utilization rate of water resources.

[0003] Conventional washing and sorting processes often use a centralized collection mode for water pipelines, where a large volume of low-chlorine wastewater generated in the jigging and sorting stage mixes with high-chlorine wastewater generated in the leaching and dechlorination stage in the physical pipelines. This mixing causes cross-contamination of the originally low-salt washing and sorting wastewater, resulting in a significant increase in the total amount of fluid entering the terminal desalination treatment system, which directly increases the operating load of the equipment inside the high-chlorine wastewater treatment workshop.

[0004] After desalination of high-chlorine wastewater, the system will separate high-salt concentrate. Existing water treatment processes lack end-point conversion methods for this high-salt concentrate, and most of them use simple natural evaporation or centralized temporary storage. This fails to completely convert the water-soluble chloride salts enriched in the water into solid salts, and thus cannot achieve true zero discharge of wastewater and resource conversion of pollutants. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides a combined system for high-chlorine coal jigging and fine coal leaching dechlorination with a tiered water circulation system. This system solves the problems of high fresh water consumption, high desalination load due to mixed flow of high and low chlorine wastewater, and the inability to achieve resource conversion of high-salt concentrated water in existing high-chlorine coal dechlorination processes.

[0006] To achieve the above objectives, this application provides the following technical solution: a combined system for high-chlorine coal jigging and clean coal leaching and dechlorination, comprising: a raw coal pretreatment unit, a jigging unit, a clean coal leaching and dechlorination unit, a coal slime dewatering and recovery unit, and a high-chlorine wastewater treatment workshop. The raw coal pretreatment unit receives high-chlorine raw coal for screening and crushing, and receives domestic sewage from the mining area to pre-wet and condition the high-chlorine raw coal. The jigging separation unit receives the high-chlorine raw coal after conditioning, and uses the domestic sewage from the mining area as the separation makeup water for stratified separation to produce qualified clean coal and generate low-chlorine wastewater; the jigging separation unit treats the low-chlorine wastewater by sedimentation and then recycles it in a closed loop within the jigging separation unit. The coal leaching and dechlorination unit receives the qualified coal and the reclaimed fresh water produced by the urban wastewater treatment workshop. The high-cleanliness water source formed by the mixture of urban wastewater and reclaimed fresh water is used as the leaching medium to perform multi-stage countercurrent leaching and solid-liquid separation on the qualified coal, producing the final coal and high-chlorine leaching wastewater. The coal slime dewatering and recovery unit receives the high-chlorine leaching wastewater and performs physical classification and sedimentation dewatering to separate coarse coal slime and high-solids sludge. The coarse coal slime is then transported back to the raw coal pretreatment unit for rewashing, while the remaining liquid is collected. The high-chlorine wastewater treatment workshop receives the remaining liquid and performs membrane separation desalination treatment to separate the regenerated fresh water and high-salt concentrated water. The regenerated fresh water is then recycled to the clean coal leaching dechlorination unit, while the high-salt concentrated water is subjected to evaporation and crystallization treatment.

[0007] Preferably, the raw coal pretreatment unit includes a raw coal buffer silo; the raw coal buffer silo receives the high-chlorine raw coal of the target particle size screened by the raw coal pretreatment unit for homogenization and pressure stabilization feeding, and receives the domestic sewage from the mining area to pre-wet and condition the high-chlorine raw coal in the raw coal buffer silo; The jigging sorting unit includes a jig, a dewatering screen, and a sorting circulating water tank. The jig receives the conditioned high-chlorine raw coal, performs gravity stratification sorting, and discharges overflow water. The dewatering screen dewaters the gangue produced by the jig and discharges dewatered screen water. The overflow water, the dewatered screen water, and the ground flushing water generated by the jigging sorting unit are collected to form low-chlorine wastewater, which is discharged into the sorting circulating water tank. The sorting circulating water tank allows the low-chlorine wastewater to settle naturally and produces sorting supernatant, which is then transported back to the jigging sorting unit for recycling.

[0008] Preferably, the clean coal leaching and dechlorination unit includes a clear water tank, a multi-stage countercurrent leaching device, and a dechlorination vibrating dewatering screen; The clear water tank receives and mixes the urban wastewater with the recycled freshwater to form the high-cleanliness water source; The multi-stage countercurrent leaching equipment receives the high-purity water source pumped from the clear water tank and the qualified clean coal, and performs multi-stage countercurrent leaching. The dechlorination vibrating dewatering screen receives materials that have undergone multi-stage countercurrent leaching and performs solid-liquid separation, separating the final clean coal as the oversize material and the high-chlorine leaching wastewater as the undersize liquid.

[0009] Preferably, the coal slime dewatering and recycling unit includes a high-frequency dewatering screen, a centrifugal dewatering machine, a thickening tank, a filter press, and a wastewater collection tank; The high-frequency dewatering screen receives the high-chlorine leaching wastewater and performs physical classification to separate the coarse coal slime as the oversize material and the high-chlorine wastewater as the undersize material. The centrifugal dewatering machine receives the coarse coal slime for mechanical dewatering and returns the dewatered coarse coal slime to the raw coal pretreatment unit. The thickening tank receives the screened high-chlorine wastewater and allows it to settle naturally, producing high-solids sludge at the bottom and separating the concentrated supernatant at the top. The filter press receives the high-solids sludge, presses and dewaters it, and discharges the filtrate. The wastewater collection tank receives the concentrated supernatant separated from the thickening tank and the filtrate discharged from the filter press, collects them centrally, and transports them as the remaining liquid to the high-chlorine wastewater treatment workshop.

[0010] Preferably, the high-chlorine wastewater treatment workshop includes a pretreatment unit, a desalination unit, a concentrated wastewater zero-discharge unit, and a desalination tank; The pretreatment unit receives the remaining liquid and performs hardening and turbidity removal treatment, and produces pretreated effluent; The desalination unit receives the pretreated effluent and performs membrane separation desalination to separate the regenerated freshwater and the high-salt concentrated water. The freshwater tank receives and stores the regenerated freshwater, and then recirculates the regenerated freshwater back to the clean coal leaching and dechlorination unit. The zero-discharge unit for concentrated water receives the high-salt concentrated water and performs evaporation and crystallization treatment to produce solid salts.

[0011] A high-chlorine coal separation, dechlorination, and grading cascade water circulation process includes the following steps: Step 1: The high-chlorine raw coal is screened and crushed through the raw coal pretreatment unit, and the high-chlorine raw coal is pre-wetted and conditioned by the domestic sewage from the mining area. Step 2: The high-chlorine raw coal that has been conditioned is fed into the jigging separation unit. The domestic sewage from the mining area is used as the separation makeup water for gravity stratification separation to produce qualified clean coal and generate low-chlorine wastewater. The low-chlorine wastewater is collected and the separation supernatant is separated by sedimentation. The separation supernatant is then recycled in a closed loop within the jigging separation unit. Step 3: The qualified clean coal is transported to the clean coal leaching and dechlorination unit. Urban wastewater and recycled fresh water are mixed to form a high-clean water source. The high-clean water source is used as the leaching medium to perform multi-stage countercurrent leaching and solid-liquid separation on the qualified clean coal, producing the final clean coal and high-chlorine leaching wastewater. Step 4: The high-chlorine leaching wastewater is discharged into the coal slime dewatering and recovery unit for physical classification and natural sedimentation to separate coarse coal slime and high-solids sludge. The dewatered coarse coal slime is then returned to the raw coal pretreatment unit for rewashing, while the remaining liquid separated is collected. Step 5: The remaining liquid is transported to the high-salinity wastewater treatment workshop as a source of high-chlorine water to be treated for deep desalination treatment, separating the regenerated fresh water and high-salinity concentrated water. The regenerated fresh water is then recycled to the clean coal leaching dechlorination unit for circulation. At the same time, the high-salinity concentrated water is concentrated and crystallized to produce solid salts.

[0012] Preferably, in step one, the raw coal pretreatment unit screens out the high-chlorine raw coal with a target particle size in the range of 0 mm to 10 mm; in step two, the jigging separation unit controls the separation yield of the qualified clean coal to be no less than 65%, and the suspended solids concentration of the separation supernatant to be no more than 200 mg / L.

[0013] Preferably, in step three, the initial dry basis total chlorine mass fraction of the qualified clean coal entering the clean coal leaching and dechlorination unit is between 0.7% and 1.3%; during multi-stage countercurrent leaching, the leaching solid-liquid ratio is controlled between 1:2 and 1:3, and the countercurrent leaching residence time is set to 25 min to 40 min, so that the final dry basis total chlorine mass fraction of the clean coal does not exceed 0.3%.

[0014] Preferably, in step five, the high-chlorine wastewater treatment workshop performs organic matter removal, softening and hardening removal, coagulation and turbidity removal, and deep filtration operations on the high-salinity source to be treated, controlling the hardness of the pretreated effluent to not exceed 3 mmol / L, the chemical oxygen demand to not exceed 50 mg / L, the turbidity to not exceed 1 NTU, and the sludge density index to not exceed 5.

[0015] Preferably, in step five, the high-chlorine wastewater treatment workshop uses reverse osmosis, nanofiltration, electrodialysis, or forward osmosis processes to desalinate the high-salinity source to be treated. During the desalination process, the overall water recovery rate of the desalination treatment is controlled to be no less than 75%, so that the chloride ion concentration of the regenerated freshwater does not exceed 200 mg / L, and the total salt content of the regenerated freshwater does not exceed 500 mg / L.

[0016] This application provides a combined system for high-chlorine coal jigging and clean coal leaching dechlorination and graded water circulation, which has the following advantages: 1. In this application, the raw coal pretreatment unit and the jigging separation unit receive domestic sewage from the mining area, and the clean coal leaching and dechlorination unit receives urban wastewater. This ensures that low-chlorine wastewater and high-chlorine leaching wastewater are completely isolated in the physical pipeline. This pipeline configuration avoids the mixing and contamination of low-chlorine wastewater by high-chlorine leaching wastewater, effectively prevents low-chlorine wastewater from increasing the total fluid handling volume of the equipment inside the high-chlorine wastewater treatment workshop, and directly reduces the operating load of the terminal desalination water treatment system.

[0017] 2. This application uses a freshwater tank to pump reclaimed freshwater back to the clear water tank configured in the coal leaching and dechlorination unit, so that the reclaimed freshwater and municipal wastewater are mixed in the clear water tank to continuously form a high-clean water source, completing the closed-loop process of water use in the coal leaching and dechlorination unit. The process uses municipal wastewater and reclaimed freshwater after deep treatment as dechlorination medium, replacing the dependence on fresh water and improving the utilization rate of unconventional water resources.

[0018] 3. This application addresses the high-salt concentrated water generated during desalination treatment. A concentrated water zero-discharge unit utilizes water vaporization and phase transformation operations to produce solid salts, completing the resource-based treatment of salts in the high-salt concentrated water. This achieves the final zero-liquid discharge of high-chlorine leaching wastewater, avoiding the external discharge of high-salt industrial wastewater. At the same time, it converts soluble chloride salts in the wastewater into solid salts, completing the harmless and resource-based transformation of pollutants. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the combined system of high-chlorine coal jigging and fine coal leaching dechlorination and graded water circulation in this application. Detailed Implementation

[0020] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0021] Example: Please see the appendix Figure 1 This application provides a combined system for high-chlorine coal jigging and clean coal leaching dechlorination, comprising: a raw coal pretreatment unit, a jigging unit, a clean coal leaching dechlorination unit, a coal slime dewatering and recovery unit, and a high-chlorine wastewater treatment workshop. In operation, the high-chlorine coal jigging and separation combined system with the clean coal leaching dechlorination and graded water circulation system involves screening and crushing the high-chlorine raw coal in the raw coal pretreatment unit to select the target particle size of the high-chlorine raw coal, which is then transported to the raw coal buffer silo included in the raw coal pretreatment unit for homogenization and pressure stabilization feeding. Domestic sewage from the mining area is connected to the raw coal buffer silo and pre-wetted and conditioned the high-chlorine raw coal in the raw coal buffer silo. After conditioned, the high-chlorine raw coal enters the jigging separation unit and is separated into layers by a jigging machine, thereby producing qualified clean coal, middlings, and gangue.

[0022] The overflow water discharged from the jig, the dewatering screen water discharged from the dewatering screen in the jig sorting unit, and the ground washing water generated in the jig sorting unit are collected to form low-chlorine wastewater, which is discharged into the sorting circulation water tank in the jig sorting unit. The low-chlorine wastewater undergoes natural sedimentation in the sorting circulation water tank and removes particulate coal slime. The sorting supernatant produced by the sorting circulation water tank is transported back to the jig and recycled in the jig sorting unit. At the same time, the water loss during the operation of the jig sorting unit is balanced by continuously replenishing the mine's domestic sewage.

[0023] The qualified clean coal produced by the jigging and sorting unit is transported to the clean coal leaching and dechlorination unit. Urban wastewater and reclaimed fresh water are injected into the clear water tank of the clean coal leaching and dechlorination unit for mixing to form a high-clean water source. The high-clean water source is pumped from the clear water tank to the multi-stage countercurrent leaching equipment set in the clean coal leaching and dechlorination unit. It is used as the leaching medium and is leached with the qualified clean coal in the multi-stage countercurrent leaching equipment to dissolve the water-soluble chloride salts contained in the qualified clean coal into the liquid phase. The material that has completed the multi-stage countercurrent leaching is discharged into the dechlorination vibrating dewatering screen set in the clean coal leaching and dechlorination unit for solid-liquid separation, thereby separating the final clean coal as the oversize and the high-chlorine leaching wastewater as the undersize liquid.

[0024] The high-chlorine leaching wastewater is discharged into the high-frequency dewatering screen configured in the coal slime dewatering and recovery unit for classification treatment. The coarse coal slime intercepted by the high-frequency dewatering screen enters the centrifugal dewatering machine configured in the coal slime dewatering and recovery unit for mechanical dewatering. Subsequently, the coarse coal slime processed by the centrifugal dewatering machine is transported to the raw coal buffer silo and washed again. The high-chlorine wastewater separated by the high-frequency dewatering screen is discharged into the thickening tank configured in the coal slime dewatering and recovery unit for sedimentation. High solids sludge is generated at the bottom of the thickening tank. The high solids sludge is transported to the filter press configured in the coal slime dewatering and recovery unit for pressing and dewatering. The concentrated supernatant separated from the thickening tank and the filtrate generated by the filter press are discharged into the wastewater collection tank configured in the coal slime dewatering and recovery unit.

[0025] The high-chlorine leaching wastewater collected in the wastewater collection pond is transported to the high-chlorine wastewater treatment workshop, and flows sequentially into the pretreatment unit, desalination unit, and concentrated water zero discharge unit contained in the high-chlorine wastewater treatment workshop. The high-chlorine leaching wastewater undergoes hardening and turbidity removal treatment in the pretreatment unit. After pretreatment, the high-chlorine leaching wastewater enters the desalination unit for membrane separation and desalination to separate regenerated freshwater and high-salt concentrated water. The regenerated freshwater is stored in the freshwater tank in the high-chlorine wastewater treatment workshop and then returned to the clear water tank. The high-salt concentrated water enters the concentrated water zero discharge unit for evaporation and crystallization treatment to produce solid salts.

[0026] In the specific process flow, the high-chlorine coal separation, dechlorination, and grading cascade water circulation process includes the following steps: Step 1: High-chlorine raw coal enters the raw coal pretreatment unit for screening and two-stage crushing to screen out the target particle size of high-chlorine raw coal with a particle size range of 0mm to 10mm, and then the target particle size high-chlorine raw coal is transported to the raw coal buffer silo included in the raw coal pretreatment unit. The raw coal buffer silo receives high-chlorine raw coal of the target particle size for homogenization and pressure stabilization feeding. At the same time, domestic sewage from the mining area is connected to the raw coal buffer silo as a secondary medium-quality water source to pre-wet and condition the high-chlorine raw coal in the raw coal buffer silo, so as to form high-chlorine raw coal with uniform moisture and particle size.

[0027] Step 2: The pre-wetted and conditioned high-chlorine raw coal is discharged into the jigging separation unit in the raw coal buffer silo. The jigging machine uses domestic sewage from the mining area as the separation makeup water to perform gravity stratification separation of the high-chlorine raw coal, thereby producing qualified clean coal, middlings, and gangue. The jigging separation unit controls the separation yield of qualified clean coal to be no less than 65%. The jig discharges overflow water during the sorting process. The dewatering screen installed in the jig sorting unit dewaters the gangue and discharges the dewatering screen water. The jig sorting unit also generates ground washing water during operation. The overflow water, dewatering screen water and ground washing water are collected together to form low-chlorine wastewater, which is discharged into the sorting circulating water pool installed in the jig sorting unit through an independent pipeline. The sorting circulating water tank receives low-chlorine wastewater for natural sedimentation to remove coarse coal slime impurities, and controls the suspended solids concentration of the sorting supernatant to not exceed 200 mg / L. The sorting supernatant produced from the sorting circulating water tank is then transported back to the jigging sorting unit. The supernatant produced by the sorting circulating water tank is used as sorting makeup water for the jig, rinsing water for middlings and gangue in the jig sorting unit, and pipeline flushing water. It is recycled in a closed loop within the jig sorting unit, making the jig sorting unit and the sorting circulating water tank an independent low-chlorine wastewater closed-loop circulation system. To address the water evaporation loss and material water loss generated during the operation of the jig sorting unit, the water volume is balanced by continuously adding domestic sewage from the mining area, and no water body containing high-chlorine leaching wastewater is connected throughout the process.

[0028] Step 3: The jigging and sorting unit produces qualified clean coal with an initial dry basis total chlorine mass fraction between 0.7% and 1.3%, and the qualified clean coal is then transported in a closed system to the multi-stage countercurrent leaching equipment set up in the clean coal leaching and dechlorination unit. At the same time, urban reclaimed water and regenerated fresh water produced by the high chlorine wastewater treatment workshop are simultaneously input into the clear water tank configured in the clean coal leaching and dechlorination unit for mixing, so as to form a high-clean water source for the primary water use of the clean coal leaching and dechlorination unit. High-purity water is pumped from the clear water tank to the multi-stage countercurrent leaching equipment and undergoes multi-stage countercurrent leaching reaction with qualified clean coal under normal temperature conditions. During the multi-stage countercurrent leaching reaction, the clean coal leaching and dechlorination unit controls the leaching solid-liquid ratio in the multi-stage countercurrent leaching equipment to be between 1:2 and 1:3 (the leaching solid-liquid ratio is the mass ratio of qualified clean coal to high-purity water), and sets the countercurrent leaching residence time of qualified clean coal in the multi-stage countercurrent leaching equipment to be between 25 min and 40 min. The multi-stage countercurrent leaching equipment dissolves the water-soluble chloride salts contained in qualified clean coal into the liquid phase through multi-stage countercurrent leaching operation. Then, the material that has completed countercurrent leaching is discharged from the multi-stage countercurrent leaching equipment and discharged into the dechlorination vibrating dewatering screen configured in the clean coal leaching dechlorination unit for solid-liquid separation, thereby separating the final clean coal as the oversize and the high-chlorine leaching wastewater as the undersize liquid. The clean coal leaching and dechlorination unit controls the dry basis total chlorine mass fraction of the final clean coal to not exceed 0.3%, and discharges the final clean coal from the clean coal leaching and dechlorination unit. At the same time, the high-chlorine leaching wastewater rich in chloride ions is transported to the coal slime dewatering and recovery unit through a separate pipeline, so that the clean coal leaching and dechlorination unit and the jigging separation unit are physically isolated in the water system to prevent the high-chlorine leaching wastewater from mixing with the low-chlorine wastewater.

[0029] Step 4: The high-chlorine leaching wastewater discharged from the clean coal leaching and dechlorination unit is transported through an independent pipeline to the high-frequency dewatering screen configured in the coal slime dewatering and recovery unit for physical classification, thereby separating the coarse coal slime as the oversize material and the high-chlorine wastewater as the undersize material. The coarse coal slime is discharged into the centrifugal dewatering machine configured in the coal slime dewatering and recovery unit for mechanical dewatering, and the dewatered coarse coal slime is returned to the raw coal buffer silo included in the raw coal pretreatment unit, so that the coarse coal slime is mixed with the high-chlorine raw coal in the raw coal buffer silo and re-enters the jigging and sorting unit for washing, thereby realizing the recycling of solid materials. The high-chlorine wastewater separated by the high-frequency dewatering screen flows into the thickening tank configured in the coal slime dewatering and recovery unit through the pipeline for natural sedimentation. This allows the high-chlorine wastewater to undergo gravity stratification in the thickening tank and settle at the bottom of the thickening tank to produce high-solids sludge. At the same time, the concentrated supernatant of the thickening tank is separated from the upper part of the thickening tank. The high-solids sludge generated at the bottom of the thickening tank is pumped to the filter press configured in the coal slime dewatering and recovery unit for pressing and dewatering and discharge of filtrate. Subsequently, the concentrated supernatant separated from the upper part of the thickening tank and the filtrate discharged from the filter press converge in the pipeline flow direction and are uniformly discharged into the wastewater collection tank configured in the coal slime dewatering and recovery unit. The wastewater collection tank centrally collects the input concentrated supernatant and filtrate, and transports the high-chlorine leaching wastewater collected in the wastewater collection tank as a source of high-salinity water to be treated to the high-chlorine wastewater treatment workshop. At this point, the coal slime dewatering and recovery unit removes the solid particles contained in the high-chlorine leaching wastewater through the coordinated physical separation operation of the centrifugal dewatering machine and the filter press, so as to meet the influent water quality requirements of the desalination equipment inside the high-chlorine wastewater treatment workshop.

[0030] Step 5: The wastewater collection tank in the coal slime dewatering and recovery unit pumps the collected high-chlorine leaching wastewater to the high-chlorine wastewater treatment workshop. The high-chlorine leaching wastewater then flows into the pretreatment unit within the high-chlorine wastewater treatment workshop for organic matter removal, softening and hardening removal, coagulation and turbidity removal, and deep filtration operations. This removes organic matter, hardness ions, colloids, and suspended solids from the high-chlorine leaching wastewater. At the same time, the hardness of the pretreated effluent produced by the pretreatment unit is controlled to be no more than 3 mmol / L, the chemical oxygen demand to be no more than 50 mg / L, the turbidity to be no more than 1 NTU, and the sludge density index to be no more than 5. Subsequently, the pretreated effluent is transported to the desalination unit within the high-chlorine wastewater treatment workshop. The desalination unit uses reverse osmosis, nanofiltration, electrodialysis, or forward osmosis processes for deep desalination, thereby separating the pretreated effluent into regenerated freshwater and high-salt concentrated water. During the desalination process, the desalination unit controls the overall water recovery rate to be no less than 75%, so that the chloride ion concentration of the regenerated freshwater does not exceed 200 mg / L, and the total salt content of the regenerated freshwater does not exceed 500 mg / L. The regenerated freshwater is discharged from the desalination unit into the freshwater tank in the high-chlorine wastewater treatment workshop for storage. The freshwater tank then pumps the regenerated freshwater back to the clear water pool in the coal leaching and dechlorination unit, so that the regenerated freshwater and urban wastewater are mixed in the clear water pool to continuously form a high-clean water source, thus completing the closed loop of the entire process of water use in the coal leaching and dechlorination unit. Meanwhile, the high-salt concentrated water separated from the desalination unit is discharged into the concentrated water zero-discharge unit included in the high-chlorine wastewater treatment workshop. The concentrated water zero-discharge unit uses evaporation crystallization to produce salt, electrolysis to produce chlorine, or bipolar membrane electrodialysis processes to concentrate and reduce the volume of high-salt concentrated water and crystallize salt. The concentrated water zero-discharge unit uses water vaporization and phase transformation operations to produce solid salt, completing the resource-based treatment of salt in high-salt concentrated water, thereby achieving the final zero liquid discharge of high-chlorine leaching wastewater.

[0031] From the perspective of the overall water system configuration, the high-chlorine coal jigging and separation and clean coal leaching dechlorination graded water circulation combined system has constructed two independent fluid transport networks in the overall water system architecture. This forms a low-chlorine water circulation network between the raw coal pretreatment unit and the jigging and separation unit, and a high-chlorine water circulation network between the clean coal leaching dechlorination unit, the coal slime dewatering and recovery unit, and the high-chlorine wastewater treatment workshop.

[0032] The low-chlorine water circulation network uses domestic sewage from the mining area as an independent water supply source. The domestic sewage from the mining area is used to supply water to the physical stratification process links with lower water quality requirements in the raw coal pretreatment unit and the jigging separation unit. At the same time, the low-chlorine wastewater generated by the jigging separation unit completes internal closed-loop circulation in the separation circulation water pool set up in the jigging separation unit. The high-chlorine coal jigging separation and clean coal leaching dechlorination graded water circulation joint system is configured with independent pipelines to physically prevent low-chlorine wastewater from flowing into the clean coal leaching dechlorination unit and the coal slime dewatering and recovery unit.

[0033] The high-chlorine water circulation network uses urban reclaimed water as the initial input water source and mixes it with the regenerated freshwater produced by the high-chlorine wastewater treatment workshop to create a high-cleanliness water source. This high-cleanliness water source is used to provide targeted water supply for the mass transfer process of removing water-soluble chloride salts in the coal leaching and dechlorination unit. Subsequently, the high-chlorine leaching wastewater produced by the coal leaching and dechlorination unit flows through independent pipelines into the coal slime dewatering and recovery unit and the high-chlorine wastewater treatment workshop for desalination and purification. Finally, the regenerated freshwater generated is returned to the coal leaching and dechlorination unit for cyclic leaching operations.

[0034] The combined high-chlorine coal jigging and clean coal leaching dechlorination system implements differentiated water supply and tiered allocation operations based on the different water quality requirements of each material processing stage. Specifically, the raw coal pretreatment unit and jigging unit receive domestic sewage from the mining area, while the clean coal leaching dechlorination unit receives urban wastewater. This ensures that low-chlorine wastewater and high-chlorine leaching wastewater are completely isolated in the physical pipelines, thereby preventing high-chlorine leaching wastewater from mixing with and polluting low-chlorine wastewater, and also preventing low-chlorine wastewater from increasing the total fluid handling capacity of the equipment inside the high-chlorine wastewater treatment workshop.

[0035] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-chlorine coal separation, dechlorination, and grading cascade water circulation system, characterized in that, include: The unit consists of a raw coal pretreatment unit, a jigging and sorting unit, a clean coal leaching and dechlorination unit, a coal slime dewatering and recovery unit, and a high-chlorine wastewater treatment workshop. The raw coal pretreatment unit receives high-chlorine raw coal for screening and crushing, and receives domestic sewage from the mining area to pre-wet and condition the high-chlorine raw coal. The jigging separation unit receives the high-chlorine raw coal after conditioning, and uses the domestic sewage from the mining area as the separation makeup water for stratified separation to produce qualified clean coal and generate low-chlorine wastewater. The jigging separation unit treats the low-chlorine wastewater by sedimentation and then recycles it in a closed loop within the jigging separation unit. The coal leaching and dechlorination unit receives the qualified coal and the reclaimed fresh water produced by the urban wastewater treatment workshop. The high-cleanliness water source formed by the mixture of urban wastewater and reclaimed fresh water is used as the leaching medium to perform multi-stage countercurrent leaching and solid-liquid separation on the qualified coal, producing the final coal and high-chlorine leaching wastewater. The coal slime dewatering and recovery unit receives the high-chlorine leaching wastewater and performs physical classification and sedimentation dewatering to separate coarse coal slime and high-solids sludge. The coarse coal slime is then transported back to the raw coal pretreatment unit for rewashing, while the remaining liquid is collected. The high-chlorine wastewater treatment workshop receives the remaining liquid and performs membrane separation desalination treatment to separate the regenerated fresh water and high-salt concentrated water. The regenerated fresh water is then recycled to the clean coal leaching dechlorination unit, while the high-salt concentrated water is subjected to evaporation and crystallization treatment.

2. The high-chlorine coal separation, dechlorination, and cascade water circulation system according to claim 1, characterized in that, The raw coal pretreatment unit includes a raw coal buffer silo. The raw coal buffer silo receives the high-chlorine raw coal of the target particle size screened by the raw coal pretreatment unit for homogenization and pressure stabilization feeding, and receives the domestic sewage from the mining area to pre-wet and condition the high-chlorine raw coal in the raw coal buffer silo. The jigging sorting unit includes a jig, a dewatering screen, and a sorting circulating water tank. The jig receives the conditioned high-chlorine raw coal, performs gravity stratification sorting, and discharges overflow water. The dewatering screen dewaters the gangue produced by the jig and discharges dewatering screen water. The overflow water, the dewatering screen water, and the ground flushing water generated by the jigging sorting unit are collected to form low-chlorine wastewater, which is discharged into the sorting circulating water tank. The sorting circulating water tank allows the low-chlorine wastewater to settle naturally and produces sorting supernatant, which is then transported back to the jigging sorting unit for recycling.

3. The high-chlorine coal separation, dechlorination, and cascade water circulation system according to claim 1, characterized in that, The clean coal leaching and dechlorination unit includes a clear water tank, a multi-stage countercurrent leaching device, and a dechlorination vibrating dewatering screen; The clear water tank receives and mixes the urban wastewater with the recycled freshwater to form the high-cleanliness water source; The multi-stage countercurrent leaching equipment receives the high-purity water source pumped from the clear water tank and the qualified clean coal, and performs multi-stage countercurrent leaching. The dechlorination vibrating dewatering screen receives materials that have undergone multi-stage countercurrent leaching and performs solid-liquid separation, separating the final clean coal as the oversize material and the high-chlorine leaching wastewater as the undersize liquid.

4. The high-chlorine coal separation, dechlorination, and cascade water circulation system according to claim 1, characterized in that, The coal slime dewatering and recovery unit includes a high-frequency dewatering screen, a centrifugal dewatering machine, a thickening tank, a filter press, and a wastewater collection tank. The high-frequency dewatering screen receives the high-chlorine leaching wastewater and performs physical classification to separate the coarse coal slime as the oversize material and the high-chlorine wastewater as the undersize material. The centrifugal dewatering machine receives the coarse coal slime for mechanical dewatering and returns the dewatered coarse coal slime to the raw coal pretreatment unit. The thickening tank receives the screened high-chlorine wastewater and allows it to settle naturally, producing high-solids sludge at the bottom and separating the concentrated supernatant at the top. The filter press receives the high-solids sludge, presses and dewaters it, and discharges the filtrate. The wastewater collection tank receives the concentrated supernatant separated from the thickening tank and the filtrate discharged from the filter press, collects them, and transports them as the remaining liquid to the high-chlorine wastewater treatment workshop.

5. The high-chlorine coal separation, dechlorination, and cascade water circulation system according to claim 1, characterized in that, The high-chlorine wastewater treatment workshop includes a pretreatment unit, a desalination unit, a concentrated wastewater zero-discharge unit, and a desalination tank. The pretreatment unit receives the remaining liquid and performs hardening and turbidity removal treatment, and produces pretreated effluent; The desalination unit receives the pretreated effluent and performs membrane separation desalination to separate the regenerated freshwater and the high-salt concentrated water. The freshwater tank receives and stores the regenerated freshwater, and then recirculates the regenerated freshwater back to the clean coal leaching and dechlorination unit. The zero-discharge unit for concentrated water receives the high-salt concentrated water and performs evaporation and crystallization treatment to produce solid salts.

6. A high-chlorine coal separation, dechlorination, and grading cascade water circulation process, characterized in that, Includes the following steps: Step 1: The high-chlorine raw coal is screened and crushed through the raw coal pretreatment unit, and the high-chlorine raw coal is pre-wetted and conditioned by the domestic sewage from the mining area. Step 2: The high-chlorine raw coal that has been conditioned is fed into the jigging separation unit. The domestic sewage from the mining area is used as the separation makeup water for gravity stratification separation to produce qualified clean coal and generate low-chlorine wastewater. The low-chlorine wastewater is collected and the separation supernatant is separated by sedimentation. The separation supernatant is then recycled in a closed loop within the jigging separation unit. Step 3: The qualified clean coal is transported to the clean coal leaching and dechlorination unit. Urban wastewater and recycled fresh water are mixed to form a high-clean water source. The high-clean water source is used as the leaching medium to perform multi-stage countercurrent leaching and solid-liquid separation on the qualified clean coal, producing the final clean coal and high-chlorine leaching wastewater. Step 4: The high-chlorine leaching wastewater is discharged into the coal slime dewatering and recovery unit for physical classification and natural sedimentation to separate coarse coal slime and high-solids sludge. The dewatered coarse coal slime is then returned to the raw coal pretreatment unit for rewashing, while the remaining liquid separated is collected. Step 5: The remaining liquid is transported to the high-salinity wastewater treatment workshop as a source of high-chlorine water to be treated for deep desalination treatment, separating the regenerated fresh water and high-salinity concentrated water. The regenerated fresh water is then recycled to the clean coal leaching dechlorination unit for circulation. At the same time, the high-salinity concentrated water is concentrated and crystallized to produce solid salts.

7. The high-chlorine coal separation, dechlorination, and tiered water circulation process according to claim 6, characterized in that, In step one, the raw coal pretreatment unit screens out the high-chlorine raw coal with a target particle size in the range of 0 mm to 10 mm. In step two, the jigging separation unit controls the separation yield of the qualified clean coal to be no less than 65%, and the suspended solids concentration of the separation supernatant to be no more than 200 mg / L.

8. The high-chlorine coal separation, dechlorination, and tiered water circulation process according to claim 6, characterized in that, In step three, the initial dry basis total chlorine mass fraction of the qualified clean coal entering the clean coal leaching and dechlorination unit is between 0.7% and 1.3%. During multi-stage countercurrent leaching, the leaching solid-liquid ratio is controlled between 1:2 and 1:3, and the countercurrent leaching residence time is set to 25 min to 40 min. Finally, the dry basis total chlorine mass fraction of the final clean coal is controlled to not exceed 0.3%.

9. The high-chlorine coal separation, dechlorination, and tiered water circulation process according to claim 6, characterized in that, In step five, the high-chlorine wastewater treatment workshop performs organic matter removal, softening and hardening removal, coagulation and turbidity removal, and deep filtration operations on the high-salinity source to be treated, controlling the hardness of the pretreated effluent to not exceed 3 mmol / L, the chemical oxygen demand to not exceed 50 mg / L, the turbidity to not exceed 1 NTU, and the sludge density index to not exceed 5.

10. The high-chlorine coal separation, dechlorination, and tiered water circulation process according to claim 6, characterized in that, In step five, the high-chlorine wastewater treatment workshop uses reverse osmosis, nanofiltration, electrodialysis, or forward osmosis processes to desalinate the high-salinity water source to be treated. During the desalination process, the overall water recovery rate of the desalination treatment is controlled to be no less than 75%, so that the chloride ion concentration of the regenerated freshwater does not exceed 200 mg / L, and the total salt content of the regenerated freshwater does not exceed 500 mg / L.

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