Coal gasification slag heavy metal oxidation leaching separation processing system and method

Abstract

The application discloses a coal gasification slag heavy metal oxidation leaching separation processing system and method in the technical field of mine solid waste treatment, which comprises a multi-radical pre-oxidation device, a primary slag slurry separation and recovery device, a three-stage leaching device and a secondary slag slurry separation and recovery device. The multi-radical pre-oxidation device adds an oxidizing agent solution to the coal gasification slag in three stages and simultaneously performs ozone oxidation and mixing and stirring to obtain coal gasification slag slurry. The primary slag slurry separation and recovery device separates the coal gasification slag slurry, recovers excess oxidizing agent solution and screens out the coal gasification slag. The three-stage leaching device adds mixed organic acid solution to the screened coal gasification slag in three stages, performs mixing and stirring, gradually transfers the heavy metals in the coal gasification slag from the solid phase to the liquid phase, and obtains tail slurry. The application has the advantages of simple operation, low cost, good separation effect and the purpose of effectively controlling the risk of coal gasification slag heavy metal leakage.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of coal gasification slag heavy metal oxidation leaching separation processing system and method, belong to mine solid waste processing technical field. BACKGROUND

[0002] With the acceleration of industrialization, coal as one of the main energy sources occupies an important position in global energy consumption. Coal gasification, as a technology for clean use of coal, produces synthesis gas through the reaction of coal and oxygen or steam at high temperature, and has been widely used in chemical raw materials and energy production. However, the byproduct coal gasification slag produced in the process of coal gasification contains a large amount of solid carbon, silicate and various heavy metals that are not completely reacted, and if it is not properly treated and directly stored or landfilled, it will cause serious pollution to the environment. The current storage method of enterprises has large space requirement and is not sustainable, has high environmental safety risk, and has low resource utilization degree, so it is urgent to develop a low-cost and high-efficiency coal gasification ash harmless and resource utilization method to reduce the production cost of enterprises and reduce the environmental impact caused by the storage of coal gasification ash.

[0003] Due to the complex composition, uneven heavy metal content and variable physical and chemical properties of coal gasification slag, its treatment method needs to consider economic efficiency, efficiency and environmental friendliness and other factors. The common treatment methods at present include physical method, chemical method and biological method, etc. The physical method mainly includes mechanical separation and gravity separation, which is simple in operation and low in cost, but only part of the large particle residues and carbon can be separated, and the removal effect of heavy metals is limited, which cannot meet the environmental protection requirements. Chemical methods include solidification / stabilization treatment, chemical precipitation, etc. These methods can effectively reduce the mobility and bioavailability of heavy metals, but the use of this method alone often requires the addition of a large amount of chemical reagents, which is high in treatment cost and low in treatment efficiency, and may produce new pollutants. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a coal gasification slag heavy metal oxidation leaching separation processing system and method. In view of the environmental risk problem of heavy metals in coal gasification slag polluting soil and groundwater, the present application uses chemical oxidizing agent to pre-oxidize and change the heavy metal combination form in solid, such as oxide, chloride, carbonate or complex compound, to improve the migration performance of heavy metals, and then uses acid leaching agent to wash and separate the easily migratory state heavy metals from solid by proton exchange and organic chelation, so as to realize the separation and reduction of heavy metals in solid, effectively reduce the threat of leaching toxicity of coal gasification slag heavy metals, and reduce the environmental risk in the process of storage and grouting.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] In a first aspect, the present application provides a coal gasification slag heavy metal oxidation leaching separation processing system, comprising: a multi-radical pre-oxidation device, a primary slag slurry separation and recovery device, a three-stage leaching device, and a secondary slag slurry separation and recovery device, the multi-radical pre-oxidation device adding an oxidizing agent solution to the coal gasification slag in three stages and simultaneously performing ozone oxidation and mixing and stirring to obtain coal gasification slag slurry; the primary slag slurry separation and recovery device separates the coal gasification slag slurry, recovers excess oxidizing agent solution, and screens out coal gasification slag; the three-stage leaching device adds mixed organic acid solution to the screened coal gasification slag in three stages for mixing and stirring, and gradually transfers the heavy metals in the coal gasification slag from the solid phase to the liquid phase, to obtain tail slurry; and the secondary slag slurry separation and recovery device separates the tail slurry to obtain excess mixed organic acid leaching agent and coal gasification slag.

[0007] Further, the multi-radical pre-oxidation device comprises multi-radical catalytic oxidation pools connected in three stages, which are provided with a feeding inlet, a dosing inlet, a gas collection port, and a water outlet, wherein the feeding inlet is connected with a slag slurry pump, the dosing inlet is connected with an ozone generator and a hydrogen peroxide storage tank with a hydrogen peroxide dosing pump through pipelines, the gas collection port is connected with an ozone destroyer, and the water outlet is connected with the primary slag slurry separation and recovery device.

[0008] Further, the primary slag slurry separation and recovery device comprises a first slag water separator with a sand discharge port and an overflow port, wherein the overflow port is connected with the multi-radical catalytic oxidation pool through a pipeline, and the pipeline is provided with a valve and a first reflux pump, and the sand discharge port is connected with the three-stage leaching device.

[0009] Further, the three-stage leaching device comprises leaching pools connected in three stages, which are provided with a feeding inlet, a dosing inlet, and a water outlet, wherein the feeding inlet is connected with the sand discharge port of the first slag water separator, the dosing inlet is connected with oxalic acid and citric acid leaching agent storage tanks with a leaching agent dosing pump through a pipeline, and the water outlet is connected with the secondary slag slurry separation and recovery device.

[0010] Further, the secondary slag slurry separation and recovery device comprises a second slag water separator with a sand discharge port and an overflow port, wherein the overflow port is connected with the leaching pool through a pipeline, and the pipeline is provided with a valve and a second reflux pump, and the sand discharge port is connected with an intermediate storage tank.

[0011] Further, the multi-radical catalytic oxidation pool and the leaching pool are both provided with annular reflux structures inside, and the annular reflux structures are provided with stirrers.

[0012] Further, the multi-radical catalytic oxidation pool and the leaching pool are both provided with aeration devices at the bottom, and the aeration devices are connected with a blower through a pipeline.

[0013] Furthermore, both the first and second slag-water separators are equipped with 70-80 mesh vibrating screens, and the particle size of the separated coal gasification slag is not less than 0.2 mm.

[0014] Furthermore, the concentration of hydrogen peroxide solution in the hydrogen peroxide storage tank is 0.50 mol / L, and the concentration of organic acid solution in the oxalic acid and citric acid rinsing agent storage tank is 0.05 mol / L.

[0015] Secondly, the present invention provides a method for oxidative leaching and separation of heavy metals in coal gasification slag, comprising:

[0016] A multi-component free radical pre-oxidation device is used to add oxidant solution to coal gasification slag in three stages while simultaneously performing ozone oxidation and mixing to obtain coal gasification slag slurry.

[0017] The coal gasification slurry is separated using a primary slurry separation and recovery device, which recovers excess oxidant solution and screens out the coal gasification slurry.

[0018] The screened coal gasification slag is mixed with a mixed organic acid solution in three stages using a three-stage washing device. The heavy metals in the coal gasification slag are transferred from the solid phase to the liquid phase in stages to obtain tailings slurry.

[0019] The tailings slurry is separated using a secondary slurry separation and recovery device to obtain excess mixed organic acid leaching agent and coal gasification slag.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0021] I. Structural Advantages: The multi-component free radical pre-oxidation device adopts a three-stage dosing method, gradually introducing oxidant and ozone oxidant. This three-stage dosing avoids the risk of instantaneous overdose of oxidant, maximizing the migration of heavy metals. Secondly, the three-stage rinsing device in this design, through the phased addition of organic acids, makes the elution process more gradual and flexible. The concentration and type of organic acid in each stage can be adjusted according to the properties of the coal gasification slag and the types of heavy metals, optimizing the elution effect. In each dosing stage, the concentration of organic acid and the elution time can be precisely controlled, ensuring that heavy metals are fully removed in each stage.

[0022] II. High Efficiency: Multi-component free radical oxidation includes hydrogen peroxide oxidation and ozone oxidation. Hydrogen peroxide oxidation has the ability to change the binding form of heavy metals in solids, which exist in strong stable binding states such as oxides, chlorides, carbonates, or complex compounds, thereby improving the migration performance of heavy metals. It can promote the transformation of heavy metals that are not easily migrated or that are stable in the aluminosilicate lattice into easily migrated heavy metals, and reduce the binding ability of heavy metals in residual carbon and aluminosilicate lattices, which helps to improve the elution effect of subsequent leaching agents on heavy metals. The synergistic effect of ozone oxidation and hydrogen peroxide shows significant advantages in the treatment of heavy metal pollution. Hydrogen peroxide provides a mild oxidation effect by generating hydroxyl radicals (·OH), while ozone, as a strong oxidant, can directly attack the stable binding state of heavy metals, especially those bound to compounds such as aluminosilicate lattices, oxides, chlorides, and carbonates. The combined effect of the two not only enhances the oxidation intensity but also promotes the release of heavy metals from the solid matrix, transforming them from a difficult-to-migrate state to an easily migrated state, thereby improving the migration of heavy metals.

[0023] Third, the mechanical stirring device not only plays a role in the oxidation reaction, ensuring full contact between the oxidant and the coal gasification slag to improve the uniformity and efficiency of the oxidation reaction, but it is also important in the rinsing process, ensuring thorough mixing of the organic acid and the coal gasification slag. This design improves the contact efficiency of the substances, shortens the reaction and rinsing time, and avoids precipitation or stratification, making the treatment process more stable and efficient.

[0024] IV. Environmentally Friendly: The mixed organic acid leaching agent is a biodegradable organic acid, which has a smaller impact on the environment compared to traditional inorganic acid treatments (such as hydrochloric acid and sulfuric acid).

[0025] V. Economic Efficiency: By optimizing the processing conditions, this invention reduces the amount of oxidant and mixed organic acid rinsing agent used. At the same time, the separated and recovered oxidant and rinsing agent can be reused, which greatly reduces the amount of chemical reagents used and the processing cost. Attached Figure Description

[0026] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0027] Figure 1 This is a schematic flowchart of an oxidation leaching separation treatment system and method for heavy metals in coal gasification slag provided in Embodiment 1 of the present invention.

[0028] Figure 2 This is a schematic diagram of the structure of an oxidation leaching separation treatment system and method for heavy metals in coal gasification slag provided in Embodiment 1 of the present invention.

[0029] The components include: 1. Slurry pump; 2. Hydrogen peroxide storage tank; 3. Hydrogen peroxide dosing pump; 4. Ozone generator; 5. First sludge-water separator; 6. First reflux pump; 7. First blower; 8. Multi-component free radical catalytic oxidation tank; 9. Oxalic acid and citric acid leaching agent storage tank; 10. Leaching agent dosing pump; 11. Second sludge-water separator; 12. Second reflux pump; 13. Leaching tank; 14. Second blower; 15. Intermediate storage tank. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0031] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this invention is for describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0032] Chemical oxidation combined with leaching technology has attracted widespread attention in the field of soil heavy metal pollution control and remediation due to its high efficiency and low risk of secondary pollution. This technology uses chemical oxidants to alter the binding form of heavy metals in solids, transforming them from poorly migrating heavy metals to more easily migrating ones. Then, acidic leaching agents are used to elute and separate the more easily migrating heavy metals from the solid through proton exchange and organic chelation, thus achieving the separation and reduction of heavy metals in the solid. Although chemical oxidation combined with leaching technology has demonstrated good treatment effects in laboratory studies and soil remediation, significant differences exist between coal gasification slag and soil composition. Coal gasification slag has a high residual carbon content, diverse heavy metal composition and types, varying affinity of heavy metals for chelating agents, and some metal oxides may be stably solidified within high-temperature molten aluminosilicate lattices, making them difficult to dissolve during remediation. Therefore, the selection of oxidants and leaching agents is crucial for the leaching efficiency of specific heavy metals, and the leaching efficiency is also significantly affected by the combination and ratio of leaching agent types. There are no relevant research results on the application of chemical oxidation combined with rinsing technology in the harmless treatment of coal gasification slag. Research on this technology will help to achieve the separation and reduction of heavy metals in coal gasification slag, and provide a prerequisite for the subsequent resource-based treatment of coal gasification slag.

[0033] This scheme proposes an oxidative leaching separation system for heavy metals in coal gasification slag. It utilizes hydrogen peroxide and ozone oxidation to alter the binding form of heavy metals in the solid, which exist in strongly stable bound states such as oxides, chlorides, carbonates, or complex compounds. This enhances the migration capacity of heavy metals, promoting the transformation of poorly migratable heavy metals and those stable within the aluminosilicate lattice into more easily migratable states. It also reduces the binding capacity of heavy metals within residual carbon and the aluminosilicate lattice, improving the elution effect of subsequent leaching agents. A mixed organic acid leaching agent is used to elute and separate the more easily migratable heavy metals from the solid through proton exchange and organic chelation, achieving the migration of heavy metals from the solid phase to the liquid phase, ultimately reducing and rendering harmless the heavy metals in the coal gasification slag. To further understand the content, features, and effectiveness of this scheme, the following examples are provided with accompanying drawings:

[0034] Example 1:

[0035] Refer to the appendix to this application Figure 1 The specific implementation of this solution includes the following key equipment:

[0036] (1) Multi-component free radical pre-oxidation device: Oxidant solution is added to the multi-component free radical pre-oxidation device in three stages, and ozone oxidation is carried out simultaneously. Multi-component free radical pre-oxidation treatment is carried out under aeration and mechanical stirring to improve the oxidation state and migration ability of heavy metals in coal gasification slag. Here, the multi-component free radical pre-oxidation device combining oxidant solution and ozone treats coal gasification slag. The specific parameters are selected according to the properties of coal gasification slag, the types and contents of heavy metals contained therein, and the final treatment compliance requirements. In addition, the mixing and stirring adopts mechanical stirring or aeration stirring. The stirring paddle or aeration head is placed in the middle guide tube. The slag slurry mixture overflows from the upper part of the guide tube to the outside of the guide tube to achieve full mixing of the slag slurry.

[0037] (2) Primary slurry separation and recovery device: The coal gasification slurry after multi-component free radical pre-oxidation is separated by a 70-80 mesh vibrating screen to recover excess oxidant. The particle size of the separated coal gasification slurry is not less than 0.2 mm.

[0038] (3) Three-stage rinsing device: Mixed organic acid solution is added to the coal gasification slag in the slurry separation and recovery device in three stages for mixing and stirring, and the heavy metals are transferred from the solid phase to the liquid phase step by step. The specific parameters for the three-stage rinsing of coal gasification slag using mixed organic acid rinsing agent are selected according to the properties of coal gasification slag, the types and contents of heavy metals contained therein, and the final treatment standards.

[0039] (4) Secondary slurry separation and recovery device: The tail slurry is separated by a 70-80 mesh vibrating screen to obtain excess mixed organic acid leaching agent and coal gasification slag. The mixed leaching agent is recycled and reused. Most of the heavy metals in the material enter the liquid phase after leaching and organic chelation, thus realizing the separation of heavy metal components.

[0040] Refer to the appendix to this application Figure 2 This embodiment 1 provides an oxidation leaching and separation treatment system for heavy metals in coal gasification slag, including a slurry pump 1, a hydrogen peroxide storage tank 2, a hydrogen peroxide dosing pump 3, an ozone generator 4, a first slag-water separator 5, a first reflux pump 6, a first blower 7, a multi-element free radical catalytic oxidation tank 8, an oxalic acid-citric acid leaching agent storage tank 9, a leaching agent dosing pump 10, a second slag-water separator 11, a second reflux pump 12, a leaching tank 13, a second blower 14, and an intermediate storage tank 15; the slurry pump 1 is connected to the inlet of the multi-element free radical catalytic oxidation tank 8, and the outlet of the multi-element free radical catalytic oxidation tank 8 is connected to the first slag-water separator 5, which includes a sand discharge mechanism. The system includes an inlet and an overflow outlet; the sand discharge outlet is connected to the inlet 13 of the scrubbing tank, and the overflow outlet is connected to the inlet of the multi-component free radical catalytic oxidation tank 8. Specifically, the overflow outlet is connected to the first return pump 6 via a valve, which controls the connection and closure of the outlet of the first slag-water separator 5 and the inlet of the multi-component free radical catalytic oxidation tank 8. Initially, the valve connects the outlet of the first slag-water separator 5 to the inlet of the multi-component free radical catalytic oxidation tank 8, allowing the flushing water to enter the wastewater treatment device. Based on the effective circulation number or effective removal time of the reagent in the multi-component free radical catalytic oxidation tank 8, the valve is manually or automatically switched, ultimately allowing the coal gasification slag to enter the scrubbing tank for scrubbing treatment. The first blower 7 is connected to the multi-component free radical catalytic oxidation tank 8, and the connection and closure of the aeration pipeline are controlled by a valve. The hydrogen peroxide storage tank 2 is connected to the multi-component free radical catalytic oxidation tank 8, and the dosing flow rate is controlled by the hydrogen peroxide dosing pump 3, with the connection and closure of the dosing pipeline controlled by a valve. Ozone generator 4 is connected to multi-element free radical catalytic oxidation tank 8, and the ozone pipeline is opened and closed via valves. Both multi-element free radical catalytic oxidation tank 8 and scrubbing tank 13 have annular reflux structures, and agitators are installed within these structures. The top of multi-element free radical catalytic oxidation tank 8 has a gas collection port connected to a residual gas collection pipe, which in turn connects to an ozone destroyer. Scrubbing tank 13 is connected to a second slag-water separator 11, with the connection method being the same as the first slag-water separator. Its sand discharge port is connected to an intermediate storage tank 15, where the treated gasified slag is stored for further processing. Organic acid scrubbing agent storage tank 9 is connected to scrubbing tank 13, with the scrubbing agent flow rate controlled by a scrubbing agent dosing pump 10, and the scrubbing agent pipeline is opened and closed via valves. A second blower 14 is connected to scrubbing tank 13, with the connection method being the same as the first blower 7.

[0041] During operation, the slag-water mixture enters the multi-component free radical catalytic oxidation tank 8 through the slurry pump 1 for pre-oxidation. After pre-oxidation, the gasification slag with a high exchangeability of heavy metals is washed and dehydrated by the first slag-water separator 5. The dehydrated gasification slag flows out from the sand discharge port and enters the rinsing tank 13 for rinsing to remove heavy metals from the gasification slag, thereby obtaining gasification slag that meets the requirements of delamination grouting. It is then washed and dehydrated by the second slag-water separator 11, where the rinsing water can be recycled and reused. The treated gasification slag is stored in the intermediate storage tank 15.

[0042] Example 2:

[0043] The total amount of heavy metals, the distribution of heavy metal speciation, and the results of toxic leaching of the coarse coal gasification slag produced by a coal chemical plant according to the solid waste toxicity leaching method - sulfuric acid-nitric acid method (HJ / T299-2007) are shown in Table 1-3. 10g of coarse coal gasification slag was mixed with a 0.50mol / L hydrogen peroxide solution and stirred for 2 hours at a liquid-to-solid ratio of 10:1. The slurry was separated using an 80-mesh vibrating screen. A 0.05mol / L organic acid solution was then added to the separated coarse coal gasification slag, and the oxidation time was 1 hour at a liquid-to-solid ratio of 10:1. The slurry was then separated again using an 80-mesh vibrating screen, yielding harmlessly treated coarse coal gasification slag and organic acid waste liquid.

[0044]

[0045]

[0046] Table 1. Heavy metal content and heavy metal speciation in coarse coal gasification slag from Example 2.

[0047]

[0048] Table 2. Heavy metal content and heavy metal speciation in the coal gasification coarse slag after harmless treatment in Example 2.

[0049]

[0050] Table 3. Leaching toxicity of coal gasification coarse slag after harmless treatment in Example 2.

[0051] The total amount, heavy metal speciation, and leaching toxicity of heavy metals in coal gasification slag treated by oxidation leaching separation were analyzed, and the results are shown in Tables 1-3. The total amount of different heavy metals in the coarse coal gasification slag was reduced to a certain extent. The total amounts of Cu, Pb, Cr, Co, As, Sb, and Ni were reduced by 30.0%, 12.0%, 34.0%, 24.1%, 26.9%, 10.6%, and 50.9%, respectively, indicating a significant harmless treatment effect. The leaching toxicity was lower than the concentration limits for heavy metal pollutants in the "Integrated Wastewater Discharge Standard" (GB8978-1996), meeting the standards for Class I solid waste. The above data prove that the coarse coal gasification slag treated by oxidation leaching separation can be used for landfill and underground backfilling.

[0052] Example 3:

[0053] The total amount of heavy metals, the distribution of heavy metal speciation, and the results of toxic leaching of the coal gasification slag fine residue produced by a coal chemical plant according to the solid waste toxicity leaching method - sulfuric acid-nitric acid method (HJ / T299-2007) are shown in Table 4-6. 10g of coal gasification slag fine residue was mixed with a 0.50mol / L hydrogen peroxide solution and stirred for 2 hours at a liquid-to-solid ratio of 10:1. The residue was separated using an 80-mesh vibrating screen. A 0.05mol / L organic acid solution was then added to the separated coal gasification slag coarse residue, and the oxidation time was 1 hour at a liquid-to-solid ratio of 10:1. The residue was then separated again using an 80-mesh vibrating screen, yielding harmlessly treated coal gasification slag fine residue and organic acid waste liquid.

[0054]

[0055] Table 4. Heavy metal content and heavy metal speciation in the fine slag of coal gasification slag in Example 3.

[0056]

[0057]

[0058] Table 6. Leaching toxicity of coal gasification slag after harmless treatment in Example 3.

[0059] The total amount, heavy metal speciation, and leaching toxicity of the coal gasification slag after oxidation leaching separation treatment were analyzed, and the results are shown in Tables 4-6. The total amount of different heavy metals in the fine coal gasification slag was reduced to a certain extent. The total amounts of Cu, Pb, Cr, Co, As, Sb, and Ni were reduced by 13.1%, 76.2%, 33.0%, 47.3%, 59.0%, 77.2%, and 58.1%, respectively, indicating a significant harmless treatment effect. The leaching toxicity was lower than the concentration limits for heavy metal pollutants in the "Integrated Wastewater Discharge Standard" (GB8978-1996), meeting the standards for Class I solid waste. The above data prove that the fine coal gasification slag treated by oxidation leaching separation treatment can be used for landfill and underground backfilling.

[0060] This solution discloses an oxidation leaching separation treatment system and method for heavy metals in coal gasification slag. The leaching concentration of heavy metals in the treated coal gasification slag meets the concentration limits for heavy metal pollutants in the "Integrated Wastewater Discharge Standard" GB 8978-1996, and complies with the standards for Class I solid waste. This method is simple to operate, low in cost, and has good separation effect, effectively controlling the risk of heavy metal leakage from coal gasification slag.

[0061] As is known from common technical knowledge, this invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative and not exhaustive. All modifications within the scope of this invention or its equivalents are included in this invention.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A system for the oxidation, leaching, and separation of heavy metals in coal gasification slag, characterized in that it comprises: The system comprises a multi-component free radical pre-oxidation device, a primary slurry separation and recovery device, a tertiary rinsing device, and a secondary slurry separation and recovery device. The multi-component free radical pre-oxidation device adds an oxidant solution to the coal gasification slag in three stages while simultaneously performing ozone oxidation and mixing to obtain a coal gasification slag slurry. The primary slurry separation and recovery device separates the slurry, recovers excess oxidant solution, and screens out the coal gasification slag. The tertiary rinsing device adds a mixed organic acid solution to the screened coal gasification slag in three stages for mixing and stirring, transferring heavy metals from the solid phase to the liquid phase step by step to obtain a tailings slurry. The secondary slurry separation and recovery device separates the tailings slurry, obtaining excess mixed organic acid rinsing agent and coal gasification slag. The multi-radical pre-oxidation device includes a three-stage interconnected multi-radical catalytic oxidation tank (8). The multi-radical catalytic oxidation tank (8) is provided with an inlet, a dosing port, a gas collection port and a water outlet. The inlet is connected to a slurry pump (1). The dosing port is connected to an ozone generator (4) and a hydrogen peroxide storage tank (2) with a hydrogen peroxide dosing pump (3) through pipelines. The gas collection port is connected to an ozone destroyer. The water outlet is connected to the primary slurry separation and recovery device. The three-stage rinsing device includes three interconnected rinsing tanks (13). The rinsing tank (13) is provided with an inlet, a dosing port and a water outlet. The inlet is connected to the sand discharge port of the first slag-water separator (5). The dosing port is connected to the oxalic acid and citric acid rinsing agent storage tank (9) with a rinsing agent dosing pump (10) via a pipeline. The water outlet is connected to the secondary slurry separation and recovery device. The concentration of hydrogen peroxide solution in the hydrogen peroxide storage tank (2) is 0.50 mol / L, and the concentration of organic acid solution in the oxalic acid and citric acid rinsing agent storage tank (9) is 0.05 mol / L.

2. The oxidation leaching and separation system for heavy metals in coal gasification slag according to claim 1, characterized in that, The primary slurry separation and recovery device includes a first slurry-water separator (5) with a sand discharge port and an overflow port, wherein the overflow port is connected to a multi-element free radical catalytic oxidation tank (8) through a pipeline, and the pipeline is equipped with a valve and a first reflux pump (6), and the sand discharge port is connected to the three-stage scrubbing device.

3. The oxidation leaching and separation system for heavy metals in coal gasification slag according to claim 1, characterized in that, The secondary slurry separation and recovery device includes a second slurry-water separator (11) with a sand discharge port and an overflow port, wherein the overflow port is connected to a scrubbing tank (13) via a pipeline, and the pipeline is equipped with a valve and a second reflux pump (12), and the sand discharge port is connected to an intermediate storage tank (15).

4. The oxidation leaching and separation system for heavy metals in coal gasification slag according to claim 1, characterized in that, Both the multi-radical catalytic oxidation tank (8) and the rinsing tank (13) are equipped with an annular reflux structure, and a stirrer is installed inside the annular reflux structure.

5. The oxidation leaching and separation system for heavy metals in coal gasification slag according to claim 1, characterized in that, Both the multi-radical catalytic oxidation tank (8) and the rinsing tank (13) are equipped with aeration devices at the bottom, and the aeration devices are connected to blowers through pipes.

6. The oxidation leaching and separation system for heavy metals in coal gasification slag according to claim 3, characterized in that, Both the first slag-water separator (5) and the second slag-water separator (11) are equipped with a 70-80 mesh vibrating screen, and the particle size of the separated coal gasification slag is not less than 0.2 mm.

7. A method for oxidative leaching and separation of heavy metals in coal gasification slag, characterized in that, Based on the oxidation leaching separation treatment system for heavy metals in coal gasification slag as described in any one of claims 1-6, including: A multi-component free radical pre-oxidation device is used to add oxidant solution to coal gasification slag in three stages while simultaneously performing ozone oxidation and mixing to obtain coal gasification slag slurry. The coal gasification slurry is separated using a primary slurry separation and recovery device, which recovers excess oxidant solution and screens out the coal gasification slurry. The screened coal gasification slag is mixed with a mixed organic acid solution in three stages using a three-stage washing device. The heavy metals in the coal gasification slag are transferred from the solid phase to the liquid phase in stages to obtain tailings slurry. The tailings slurry is separated using a secondary slurry separation and recovery device to obtain excess mixed organic acid leaching agent and coal gasification slag.

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