Oxidation leaching separation treatment system and method for heavy metal in coal gasification slag

Abstract

The invention discloses an oxidation leaching separation treatment system and method for heavy metal in coal gasification slag in the technical field of mine solid waste treatment, and the oxidation leaching separation treatment system comprises a multi-element free 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-element free radical pre-oxidation device is used for adding an oxidant solution into the coal gasification slag in three stages and simultaneously carrying out ozone oxidation and mixing stirring to obtain coal gasification slag slurry; the primary slag-slurry separation and recovery device is used for carrying out slag-slurry separation on coal gasification slag slurry, recovering an excessive oxidant solution and screening out coal gasification slag; the three-stage leaching device is used for adding a mixed organic acid solution into the screened coal gasification slag in three stages for mixing and stirring, and transferring heavy metals in the coal gasification slag from a solid phase to a liquid phase step by step to obtain tail slurry. The method has the advantages of simple operation, low cost and good separation effect, and achieves the purpose of effectively controlling the leakage risk of heavy metals in the coal gasification slag.

Description

Technical Field

[0001] The invention relates to an oxidation, leaching, separation and treatment system and method for heavy metals in coal gasification slag, belonging to the technical field of mine solid waste treatment. Background Art

[0002] With the acceleration of industrialization, coal, as one of the main energy sources, occupies an important position in global energy consumption. As a technology for clean utilization of coal, coal gasification produces synthesis gas by reacting coal with oxygen or steam at high temperature, and has been widely used in chemical raw materials and energy production. However, the byproduct gasification slag produced in the coal gasification process contains a large amount of unreacted solid residual carbon, aluminosilicates and various heavy metals. If it is directly stored or landfilled without proper treatment, it will cause serious pollution to the environment. The current storage method of enterprises requires a large amount of space and is unsustainable, with high environmental safety risks and low resource utilization. Therefore, it is urgent to develop low-cost and high-efficiency methods for harmless and resource-based utilization of coal gasification ash, so as to reduce the production costs of enterprises and reduce the environmental impact caused by the storage of coal gasification ash.

[0003] Since coal gasification slag has the characteristics of complex composition, uneven heavy metal content, and variable physical and chemical properties, its treatment method needs to take into account multiple factors such as economy, efficiency, and environmental friendliness. At present, common treatment methods include physical, chemical, and biological methods. Physical methods mainly include mechanical sorting and gravity sorting. Although the operation is simple and the cost is low, they can only separate some large particles of residue and carbon, and the removal effect of heavy metals is limited, which cannot meet 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 using this method alone often requires the addition of a large amount of chemical reagents, with high treatment costs, low treatment efficiency, and the possibility of generating new pollutants. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a system and method for oxidative leaching and separation of heavy metals in coal gasification slag. In view of the environmental risk of heavy metals in coal gasification slag polluting soil and groundwater, this scheme uses chemical oxidants for pre-oxidation to change the binding form of heavy metals in the solid in the form of oxides, chlorides, carbonates or composite compounds with stronger and more stable binding, thereby improving the migration performance of heavy metals, and then uses acidic eluents to elute and separate easily mobile heavy metals from the solid through proton exchange and organic chelation, thereby achieving the separation and reduction of heavy metals in the solid, effectively reducing the threat of toxic leaching of heavy metals in coal gasification slag, and reducing its environmental risks during storage and grouting.

[0005] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0006] In a first aspect, the present invention provides an oxidation, leaching, separation and treatment system for heavy metals in coal gasification slag, comprising: a multi-radical pre-oxidation device, a primary slurry separation and recovery device, a three-stage leaching device and a secondary slurry separation and recovery device, wherein the multi-radical pre-oxidation device adds an oxidant solution to the coal gasification slag in three stages and simultaneously performs ozone oxidation and mixed stirring to obtain a coal gasification slag slurry; the primary slurry separation and recovery device performs slurry separation on the coal gasification slag slurry, recovers excess oxidant solution and screens out the coal gasification slag; the three-stage leaching device adds a mixed organic acid solution to the screened coal gasification slag in three stages for mixed stirring, and transfers the heavy metals in the coal gasification slag from the solid phase to the liquid phase step by step to obtain a tail slurry; the secondary slurry separation and recovery device performs slurry separation on the tail slurry to obtain excess mixed organic acid leaching agent and coal gasification slag.

[0007] Furthermore, the multi-radical pre-oxidation device includes a multi-radical catalytic oxidation pool with a three-stage interconnected arrangement, and the multi-radical catalytic oxidation pool is provided with a feed inlet, a dosing port, a gas collection port and a water outlet, wherein the feed inlet is connected to a slurry pump, the dosing port is connected to an ozone generator and a hydrogen peroxide storage tank with a hydrogen peroxide dosing pump through pipelines, the gas collection port is connected to an ozone destructor, and the water outlet is connected to the primary slurry separation and recovery device.

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

[0009] Furthermore, the three-stage elution device includes a three-stage interconnected elution pool, which is provided with an inlet, a dosing port and a water outlet, wherein the inlet is connected to the sand discharge port of the first slag-water separator, the dosing port is connected to the oxalic acid and citric acid eluent storage tank with an eluent dosing pump through a pipeline, and the water outlet is connected to the secondary slurry separation and recovery device.

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

[0011] Furthermore, both the multi-radical catalytic oxidation tank and the elution tank are provided with an annular reflux structure, and an agitator is provided in the annular reflux structure.

[0012] Furthermore, an aeration device is provided at the bottom of the multi-radical catalytic oxidation tank and the leaching tank, and the aeration device is connected to a blower through a pipeline.

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

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

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

[0016] Using a multi-radical pre-oxidation device, an oxidant solution is added to the coal gasification slag in three stages and ozone oxidation and mixing are performed simultaneously to obtain a coal gasification slag slurry;

[0017] The coal gasification slag slurry is separated by a primary slurry separation and recovery device, excess oxidant solution is recovered and the coal gasification slag is screened out;

[0018] The screened coal gasification slag is added with a mixed organic acid solution in three stages by a three-stage leaching device for mixing and stirring, so that the heavy metals in the coal gasification slag are gradually transferred from the solid phase to the liquid phase to obtain tail slurry;

[0019] The tailing slurry is separated by a secondary slurry separation and recovery device to obtain excess mixed organic acid eluent and coal gasification slag.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. Structural advantages: The multi-radical pre-oxidation device adopts a three-stage dosing method to gradually introduce oxidants and ozone oxidants. The three-stage dosing of oxidants avoids the risk of instantaneous excessive oxidants and maximizes the mobility of heavy metals. Secondly, the three-stage elution device in this design adds organic acids in stages to make 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 gasification slag and the type of heavy metals to optimize the elution effect. In each dosing stage, the concentration and elution time of the organic acid can be finely controlled to ensure that heavy metals can be fully removed at each stage;

[0022] 2. High efficiency: Multi-radical oxidation includes hydrogen peroxide oxidation agent and ozone oxidation. Hydrogen peroxide oxidation agent has the ability to change the binding form of heavy metals in the form of oxides, chlorides, carbonates or complex compounds in the solid, improve the migration performance of heavy metals, and promote the transformation of heavy metals that are not easy to migrate and heavy metals that are stable in the aluminosilicate lattice into easy to migrate heavy metals, reduce the binding ability of heavy metals in residual carbon and aluminosilicate lattices, and help improve the elution effect of subsequent eluents 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 the combination with compounds such as aluminosilicate lattices, oxides, chlorides and carbonates. The combined action 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 easy to migrate state, thereby improving the mobility of heavy metals;

[0023] 3. The mechanical stirring device not only plays a role in the oxidation reaction, ensuring that the oxidant and the coal gasification slag are fully in contact, improving the uniformity and efficiency of the oxidation reaction, but is also equally important in the elution process, ensuring that the organic acid and the coal gasification slag are fully mixed. This design improves the contact efficiency of the substances, shortens the reaction and elution time, and avoids precipitation or stratification, making the treatment process more stable and efficient;

[0024] 4. Environmentally friendly: The mixed organic acid eluent is a biodegradable organic acid, which has less impact on the environment than traditional inorganic acid (such as hydrochloric acid and sulfuric acid) treatment;

[0025] V. Economical: The present invention reduces the usage of hydrogen peroxide oxidizing agent and mixed organic acid eluent by optimizing the processing conditions. Meanwhile, the separated and recovered oxidizing agent and eluent can be reused, which greatly reduces the usage of chemical reagents and processing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0027] Figure 1 A schematic flow chart of a system and method for oxidative leaching and separation of heavy metals from coal gasification slag provided in Example 1 of the present invention;

[0028] Figure 2 This is a structural schematic diagram of a system and method for oxidative leaching and separation of heavy metals in coal gasification slag provided in Example 1 of the present invention.

[0029] Among them: 1. Slurry pump; 2. Hydrogen peroxide storage tank; 3. Hydrogen peroxide dosing pump; 4. Ozone generator; 5. First slag-water separator; 6. First reflux pump; 7. First blower; 8. Multi-radical catalytic oxidation tank; 9. Oxalic acid and citric acid eluent storage tank; 10. Eluent dosing pump; 11. Second slag-water separator; 12. Second reflux pump; 13. Eluent tank; 14. Second blower; 15. Intermediate storage tank. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0031] The following detailed description is an exemplary description, which is intended to provide further detailed description of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the present invention belongs. The terms used in the present invention are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present invention.

[0032] Chemical oxidation combined with leaching technology has attracted wide attention in the field of soil heavy metal pollution prevention, control and remediation due to its high efficiency and low risk of secondary pollution. This technology uses chemical oxidants to change the binding form of heavy metals in the solid in the form of oxides, chlorides, carbonates or complex compounds, converting the difficult-to-migrate heavy metals in the solid into easy-to-migrate heavy metals, and then uses acidic eluents to elute and separate the easy-to-migrate heavy metals from the solid through proton exchange and organic chelation, thereby achieving the separation and reduction of heavy metals in the solid. Although chemical oxidation combined with leaching technology has shown good treatment effects in laboratory studies and soil remediation, due to the large differences in the composition of coal gasification slag and soil, its residual carbon content is high, the composition and types of heavy metals are many, the affinity of heavy metals to chelating agents is different, and some metal oxides are stably solidified in the high-temperature molten aluminosilicate lattices, which may be difficult to dissolve during the remediation process. Therefore, the selection of the types of oxidants and eluents is crucial to the leaching and separation efficiency of specific heavy metals, and the leaching efficiency is also significantly affected by the type and proportion of eluents. There are no relevant research results on the application of chemical oxidation combined with leaching technology in the harmless treatment of coal gasification slag. Research on this technology will help to separate and reduce heavy metals in coal gasification slag and provide a prerequisite for the subsequent resource utilization of coal gasification slag.

[0033] This scheme proposes an oxidation leaching and separation treatment system for heavy metals in coal gasification slag, which uses hydrogen peroxide oxidation agent and ozone oxidation to change the binding form of heavy metals in the solid in the form of oxides, chlorides, carbonates or composite compounds with stronger stable binding, improve the ability of heavy metal migration performance, promote the transformation of heavy metals that are not easy to migrate and heavy metals stable in the aluminosilicate lattice into easy to migrate heavy metals, reduce the binding ability of heavy metals in residual carbon and aluminosilicate lattices, and improve the elution effect of subsequent eluents on heavy metals. A mixed organic acid eluent is used to elute and separate the easy to migrate heavy metals from the solid through proton exchange and organic chelation, realize the migration of heavy metals from the solid phase to the liquid phase, and finally complete the reduction and harmless treatment of heavy metals in coal gasification slag. In order to further understand the content, characteristics and efficacy of this scheme, the following examples are given and illustrated as follows:

[0034] Embodiment 1:

[0035] Refer to the attached Figure 1 The specific implementation of this solution includes the following key devices:

[0036] (1) Multi-component free radical pre-oxidation device: an oxidant solution is added to the multi-component free radical pre-oxidation device in three stages, and ozone oxidation is performed simultaneously. Multi-component free radical pre-oxidation treatment is performed under aeration stirring and mechanical stirring to improve the oxidation state and migration capacity of heavy metals in coal gasification slag. Here, the multi-component free radical pre-oxidation device combined with the oxidant solution and ozone treats the coal gasification slag. The specific parameters are selected according to the properties of the coal gasification slag, the types and contents of heavy metals contained therein, and the requirements for final treatment compliance. 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, and 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) A primary slurry separation and recovery device: the coal gasification slurry after multi-radical pre-oxidation is separated by passing through a 70-80 mesh vibrating screen to recover excess oxidant, and the particle size of the separated coal gasification slag is not less than 0.2 mm;

[0038] (3) Three-stage leaching device: A 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, so as to transfer the heavy metals from the solid phase to the liquid phase step by step. In this process, the mixed organic acid leaching agent is used for the three-stage leaching of the coal gasification slag. The specific parameters are selected according to the properties of the coal gasification slag, the types and contents of the heavy metals contained therein, and the requirements for the final treatment to meet the standards;

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

[0040] Refer to the attached Figure 2 In this embodiment 1, a system for oxidizing, leaching and separating heavy metals in coal gasification slag is provided, comprising 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-radical catalytic oxidation tank 8, an oxalic acid-citric acid eluent storage tank 9, an eluent 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 feed inlet of the multi-radical catalytic oxidation tank 8, the outlet of the multi-radical catalytic oxidation tank 8 is connected to the first slag-water separator 5, and the first slag-water separator 5 includes a sand discharger. The sand discharge port is connected to the inlet 13 of the leaching tank, and the overflow port is connected to the inlet of the multi-radical catalytic oxidation tank 8. The specific connection method can be: the overflow port is connected to the first reflux pump 6 through a valve, and the valve is used to control the connection and closing of the outlet of the first slag-water separator 5 and the inlet of the multi-radical catalytic oxidation tank 8. Specifically, the outlet of the first slag-water separator 5 can be controlled by a valve to connect to the inlet of the multi-radical catalytic oxidation tank 8, and the flushing water enters the wastewater treatment device. According to the effective cycle number or effective removal time of the reagent in the multi-radical catalytic oxidation tank 8, the valve is manually or automatically switched, and finally the gasified slag enters the leaching tank for leaching treatment. The first blower 7 is connected to the multi-radical catalytic oxidation tank 8, and the connection and closing of the aeration pipeline are controlled by a valve. The hydrogen peroxide storage tank 2 is connected to the multi-radical catalytic oxidation tank 8, and the dosing flow is controlled by the hydrogen peroxide dosing pump 3, and the connection and closing of the dosing pipeline are controlled by a valve. The ozone generator 4 is connected to the multi-radical catalytic oxidation tank 8, and the connection and closing of the ozone pipeline are controlled by a valve. The multi-radical catalytic oxidation tank 8 and the leaching tank 13 are both provided with an annular reflux structure, and an agitator is provided in the annular reflux structure. The top of the multi-radical catalytic oxidation tank 8 is provided with a gas collecting port connected to the residual gas collection pipe, and the residual gas collection pipe is connected to the ozone destroyer. The leaching tank 13 is connected to the second slag-water separator 11, and the connection method of the second slag-water separator 11 is the same as that of the first slag-water separator. The sand discharge port is connected to the intermediate storage tank 15, and the treated gasified slag is stored in the intermediate storage tank 15 for subsequent treatment. The organic acid eluent storage tank 9 is connected to the leaching tank 13, and the eluent flow rate is controlled by the eluent dosing pump 10, and the connection and closing of the eluent pipeline are controlled by a valve. The second blower 14 is connected to the leaching tank 13, and the specific connection method is the same as that of the first blower 7.

[0041] During operation, the slag-water mixture enters the multi-radical catalytic oxidation tank 8 through the slurry pump 1 for pre-oxidation. After the pre-oxidation, the gasified slag with a higher exchangeable state of heavy metals is rinsed and dehydrated by the first slag-water separator 5. The dehydrated gasified slag flows out from the sand discharge port and enters the leaching tank 13 for leaching to remove the heavy metals in the gasified slag, thereby obtaining the gasified slag that meets the requirements of delamination grouting. It is rinsed and dehydrated by the second slag-water separator 11, wherein the rinsing water can be refluxed for reuse, and the treated gasified slag enters the intermediate storage tank 15 for storage.

[0042] Embodiment 2:

[0043] The total amount of heavy metals in the crude coal gasification slag produced by a coal chemical plant, the distribution of heavy metal forms, and the toxic leaching of the coal gasification slag according to the solid waste toxicity leaching method-sulfuric acid and nitric acid method (HJ / T299-2007) are shown in Table 1-3. 10g of crude coal gasification slag and a 0.50mol / L hydrogen peroxide solution were mixed and stirred, the oxidation time was 2 hours, the liquid-solid ratio was 10:1, and the slurry was separated by an 80-mesh vibrating screen. The organic acid solution with a concentration of 0.05mol / L was continued to be added to the separated crude coal gasification slag, the oxidation time was 1 hour, the liquid-solid ratio was 10:1, and the slurry was separated by an 80-mesh vibrating screen to obtain the harmless crude coal gasification slag and organic acid waste liquid.

[0044]

[0045]

[0046] Table 1 Heavy metal content and heavy metal form distribution in crude slag from coal gasification in Example 2

[0047]

[0048] Table 2 Heavy metal content and heavy metal form distribution in the gasification crude slag after harmless treatment in Example 2

[0049]

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

[0051] The total amount of heavy metals, heavy metal forms and leaching toxicity in the gasification slag treated by the oxidation, leaching and separation treatment method were analyzed, and the results are shown in Table 1-3. The total amount of different heavy metals in the crude gasification slag has been reduced to a certain extent, and the total amount of heavy metals of Cu, Pb, Cr, Co, As, Sb, and Ni has been reduced by 30.0%, 12.0%, 34.0%, 24.1%, 26.9%, 10.6% and 50.9% respectively, with obvious harmless effect; the leaching toxicity is lower than the concentration limit of heavy metal pollutants in the "Comprehensive Sewage Discharge Standard" (GB8978-1996), and meets the standard of Class I solid waste. The above data prove that the crude gasification slag treated by the oxidation, leaching and separation treatment method can be landfilled and filled underground.

[0052] Embodiment three:

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

[0054]

[0055] Table 4 Heavy metal content and heavy metal form distribution in coal gasification slag fine slag in Example 3

[0056]

[0057]

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

[0059] The total amount of heavy metals, heavy metal forms and leaching toxicity in the coal gasification slag treated by the oxidation, leaching and separation treatment method were analyzed, and the results are shown in Table 4-6. The total amount of different heavy metals in the coal gasification fine slag has been reduced to a certain extent, and the total amount of heavy metals of Cu, Pb, Cr, Co, As, Sb and Ni has been reduced by 13.1%, 76.2%, 33.0%, 47.3%, 59.0%, 77.2% and 58.1% respectively, with obvious harmless effect; the leaching toxicity is lower than the concentration limit of heavy metal pollutants in the "Comprehensive Sewage Discharge Standard" (GB8978-1996), and meets the standard of Class I solid waste. The above data prove that the coal gasification slag fine slag treated by the oxidation, leaching and separation treatment method can be landfilled and filled underground.

[0060] This proposal discloses a system and method for oxidation, leaching and separation of heavy metals in coal gasification slag. The heavy metal leaching concentration of the treated coal gasification slag reaches the concentration limit of heavy metal pollutants in the "Comprehensive Wastewater Discharge Standard" GB 8978-1996, and meets the standard of Class I solid waste. This method has the advantages of simple operation, low cost and good separation effect, and achieves the purpose of effectively controlling the risk of heavy metal leakage in coal gasification slag.

[0061] It is known from common technical knowledge that the present invention can be implemented by other embodiments that do not deviate from its spirit or essential features. Therefore, the above disclosed embodiments are only illustrative in all respects and are not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are included in the present invention.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A system for oxidation, leaching and separation of heavy metals in coal gasification slag, characterized in that it comprises: A multi-radical pre-oxidation device, a primary slurry separation and recovery device, a three-stage leaching device and a secondary slurry separation and recovery device, wherein the multi-radical pre-oxidation device adds an oxidant solution to the gasification slag in three stages and simultaneously performs ozone oxidation and mixed stirring to obtain a gasification slag slurry; the primary slurry separation and recovery device performs slurry separation on the gasification slag slurry, recovers excess oxidant solution and screens out the gasification slag; the three-stage leaching device adds a mixed organic acid solution to the screened gasification slag in three stages for mixed stirring, and transfers the heavy metals in the gasification slag from the solid phase to the liquid phase step by step to obtain a tail slurry; the secondary slurry separation and recovery device performs slurry separation on the tail slurry to obtain an excess of mixed organic acid leaching agent and gasification slag.

2. The oxidation, leaching, separation and treatment system for heavy metals in coal gasification slag according to claim 1 is characterized in that: The multi-radical pre-oxidation device comprises a multi-radical catalytic oxidation pool (8) arranged in three stages, wherein the multi-radical catalytic oxidation pool (8) is provided with a feed inlet, a dosing port, a gas collection port and a water outlet, wherein the feed 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 destructor, and the water outlet is connected to the primary slurry separation and recovery device.

3. The oxidation, leaching, separation and treatment system for heavy metals in coal gasification slag according to claim 2 is characterized in that: The primary slurry separation and recovery device comprises a first slag-water separator (5) with a sand discharge port and an overflow port, wherein the overflow port is connected to a multi-radical catalytic oxidation tank (8) via a pipeline, and the pipeline is provided with a valve and a first reflux pump (6), and the sand discharge port is connected to the three-stage elution device.

4. The oxidation, leaching, separation and treatment system for heavy metals in coal gasification slag according to claim 3 is characterized in that: The three-stage elution device comprises a three-stage interconnected elution pool (13), wherein the elution pool (13) is provided with a feed inlet, a dosing port and a water outlet, wherein the feed inlet is connected to the sand discharge port of the first slag-water separator (5), the dosing port is connected to an oxalic acid or citric acid eluent storage tank (9) with an eluent dosing pump (10) via a pipeline, and the water outlet is connected to the secondary slag slurry separation and recovery device.

5. The oxidation, leaching, separation and treatment system for heavy metals in coal gasification slag according to claim 4 is characterized in that: The secondary slurry separation and recovery device comprises a second slag-water separator (11) with a sand discharge port and an overflow port, wherein the overflow port is connected to a leaching tank (13) via a pipeline, and the pipeline is provided with a valve and a second reflux pump (12), and the sand discharge port is connected to an intermediate storage tank (15).

6. The oxidation, leaching, separation and treatment system for heavy metals in coal gasification slag according to claim 4 is characterized in that: The multi-radical catalytic oxidation pool (8) and the elution pool (13) are both provided with an annular reflux structure, and an agitator is provided in the annular reflux structure.

7. The oxidation, leaching, separation and treatment system for heavy metals in coal gasification slag according to claim 4 is characterized in that: The bottoms of the multi-radical catalytic oxidation tank (8) and the leaching tank (13) are both provided with an aeration device, and the aeration device is connected to a blower via a pipeline.

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

9. The oxidation, leaching, separation and treatment system for heavy metals in coal gasification slag according to claim 5, characterized in that: The concentration of the hydrogen peroxide solution in the hydrogen peroxide storage tank (2) is 0.50 mol / L, and the concentration of the organic acid solution in the oxalic acid and citric acid eluent storage tank (9) is 0.05 mol / L.

10. A method for oxidation, leaching and separation of heavy metals in coal gasification slag, characterized in that: include: Using a multi-radical pre-oxidation device, an oxidant solution is added to the coal gasification slag in three stages and ozone oxidation and mixing are performed simultaneously to obtain a coal gasification slag slurry; The coal gasification slag slurry is separated by a primary slurry separation and recovery device, excess oxidant solution is recovered and the coal gasification slag is screened out; The screened coal gasification slag is added with a mixed organic acid solution in three stages by a three-stage leaching device for mixing and stirring, so that the heavy metals in the coal gasification slag are gradually transferred from the solid phase to the liquid phase to obtain tail slurry; The tailing slurry is separated by a secondary slurry separation and recovery device to obtain excess mixed organic acid eluent and coal gasification slag.

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