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

Abstract

The utility model discloses an oxidation leaching separation treatment system for heavy metals in coal gasification slag, which belongs to the technical field of mine solid waste treatment and 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 device is simple to operate, low in cost and good in separation effect, and achieves the purpose of effectively controlling the heavy metal leakage risk of the coal gasification slag.

Description

Technical Field

[0001] This utility model relates to an oxidation leaching and separation treatment system for heavy metals in coal gasification slag, belonging to the field of mine solid waste treatment technology. Background Technology

[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 the clean utilization of coal, produces syngas through the reaction of coal with oxygen or steam at high temperatures, and has been widely used in chemical raw material and energy production. However, the by-product of coal gasification, coal gasification ash, contains a large amount of unreacted solid carbon residue, aluminosilicates, and various heavy metals. If it is directly stockpiled or landfilled without proper treatment, it will cause serious environmental pollution. Current stockpiling methods used by enterprises require large amounts of space and are unsustainable, pose high environmental safety risks, and have low resource utilization rates. Therefore, there is an urgent need to develop low-cost, high-efficiency methods for the harmless and resource-based utilization of coal gasification ash, thereby reducing enterprise production costs and mitigating the environmental impact of coal gasification ash stockpiling.

[0003] Due to the complex composition, uneven heavy metal content, and variable physicochemical properties of coal gasification slag, its treatment methods must consider factors such as economy, efficiency, and environmental friendliness. Currently, common treatment methods include physical, chemical, and biological methods. Physical methods mainly include mechanical separation and gravity separation. Although simple to operate and low in cost, they can only separate some large particles and carbon, with limited effectiveness in removing heavy metals, failing to meet environmental protection requirements. Chemical methods include solidification / stabilization treatment and chemical precipitation. These methods can effectively reduce the migration and bioavailability of heavy metals, but using these methods alone often requires the addition of large amounts of chemical reagents, resulting in high treatment costs, low efficiency, and the potential generation of new pollutants. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an oxidation leaching separation system for heavy metals in coal gasification slag. Addressing the environmental risks posed by heavy metals in coal gasification slag to soil and groundwater pollution, this solution utilizes chemical oxidants for pre-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, thereby improving their migration performance. Then, an acidic leaching agent is used to elute and separate 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. This effectively reduces the threat of heavy metal leaching toxicity from coal gasification slag and minimizes its environmental risks during storage and grouting processes.

[0005] To achieve the above objectives, this utility model employs the following technical solution:

[0006] This utility model provides an oxidation leaching and separation system for heavy metals in coal gasification slag, comprising: a three-stage interconnected multi-element free radical catalytic oxidation tank, wherein the multi-element free radical catalytic oxidation tank is provided with an inlet, a dosing inlet, a gas collecting inlet, and a water outlet, wherein the inlet is connected to a slurry pump, the dosing inlet is connected via pipeline to an ozone generator and a hydrogen peroxide storage tank equipped with a hydrogen peroxide dosing pump, the gas collecting inlet is connected to an ozone destroyer, and the water outlet is connected to a first slag-water separator with a sand discharge port and an overflow port, wherein the overflow port is connected via... The pipeline connects to a multi-radical catalytic oxidation tank equipped with valves and a first reflux pump. The sand discharge port connects to a three-stage interconnected scrubbing tank. The scrubbing tank is equipped with an inlet, a dosing port, and a water outlet. The inlet connects to the sand discharge port of the first slag-water separator. The dosing port connects to an oxalic acid and citric acid scrubbing agent storage tank equipped with a scrubbing agent dosing pump via a pipeline. The water outlet connects to a second slag-water separator equipped with a sand discharge port and an overflow port. The overflow port connects to the scrubbing tank equipped with valves and a second reflux pump via a pipeline. The sand discharge port connects to an intermediate storage tank.

[0007] Furthermore, both the multi-radical catalytic oxidation tank and the rinsing tank are equipped with an annular reflux structure, and a stirrer is installed inside the annular reflux structure.

[0008] Furthermore, both the bottom of the multi-radical catalytic oxidation tank and the rinsing tank are equipped with aeration devices, and the aeration devices are connected to blowers via pipes.

[0009] 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.

[0010] 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.

[0011] Compared with the prior art, the beneficial effects achieved by this utility model are as follows:

[0012] I. Structural Advantages: The multi-component free radical catalytic oxidation tank adopts a three-stage interconnected design, facilitating the gradual introduction of oxidant and ozone oxidant through a three-stage dosing method. This three-stage dosing avoids the risk of instantaneous over-dosing of oxidant, maximizing the migration of heavy metals. Secondly, the three-stage rinsing tank 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 at 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 at each stage.

[0013] 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 oxidizing 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.

[0014] 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.

[0015] 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);

[0016] V. Economic Efficiency: This solution reduces the amount of oxidant and mixed organic acid rinsing agent used by optimizing the treatment conditions. 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 treatment cost. Attached Figure Description

[0017] The accompanying drawings, which form part of this specification, are used to provide a further understanding of this utility model. The illustrative embodiments and descriptions of this utility model are used to explain this utility model and do not constitute an undue limitation thereof. In the drawings:

[0018] Figure 1 This is a schematic diagram of a process for an oxidation leaching and separation treatment system for heavy metals in coal gasification slag, provided in Embodiment 1 of this utility model.

[0019] Figure 2 This is a schematic diagram of the structure of a coal gasification slag heavy metal oxidation leaching separation treatment system provided in Embodiment 1 of this utility model.

[0020] 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

[0021] 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.

[0022] The following detailed description is exemplary and intended to provide further detailed explanation of the present 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 to which this invention pertains. The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this invention.

[0023] 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.

[0024] 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:

[0025] Example 1:

[0026] Refer to the appendix to this application Figure 1 The specific implementation of this solution includes the following key equipment:

[0027] (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 at the same time. 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 slag slurry.

[0028] (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.

[0029] (3) Three-stage rinsing device: Mixed organic acid solution is added to the coal gasification slag in the slag 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. Here, mixed organic acid rinsing agent is used for three-stage rinsing of 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 standards.

[0030] (4) Secondary slurry separation and recovery device: The tail slurry is separated by a 70-80 mesh vibrating screen to obtain an excess of 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.

[0031] 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.

[0032] 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.

[0033] Example 2:

[0034] 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. 10 g of coarse coal gasification slag was mixed with a 0.50 mol / 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 0.05 mol / 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.

[0035] Types of heavy metals Cu Pb Cr Co As Sb Ni Metal exchangeable state F1 0.30 5.88 0.66 1.43 7.50 0.01 13.31 carbonate-bound F2 1.46 2.95 1.06 2.88 1.13 0.03 14.86 Iron / manganese oxide F3 0.10 9.17 204.27 8.75 2.49 0.04 27.84 Organic F4 18.01 7.93 39.31 8.92 1.99 0.06 23.41 Residual state F5 203.08 24.75 1695.15 43.71 32.40 2.13 855.28 <![CDATA[Total heavy metals (mg·kg -1 )]]> 222.95 50.68 1940.45 65.69 45.51 2.27 934.70 <![CDATA[Heavy metal content (mg·kg -1 )]]> 188.93 58.55 1883.55 78.58 50.55 2.75 793.48 Heavy metal recovery rate (%) 118.01% 86.56% 103.02% 83.60% 90.03% 82.55% 117.80%

[0036] Table 1. Heavy metal content and heavy metal speciation in the coarse slag of coal gasification in Example 2

[0037] Types of heavy metals Cu Pb Cr Co As Sb Ni <![CDATA[Exchangeable metal F1 (mg·kg -1 )]]> 1.33 6.42 7.96 1.53 7.21 0.01 5.08 <![CDATA[Carbonate-bound F2 (mg·kg -1 )]] 11.34 2.59 12.89 1.82 0.27 0.01 15.57 <![CDATA[Iron / manganese oxide state F3 (mg·kg -1 )]]> 0.83 15.50 495.30 4.11 1.66 0.07 11.52 <![CDATA[Organic F4 (mg·kg -1 )]]> 45.81 6.75 45.71 5.01 2.80 0.09 16.93 <![CDATA[Residual态F5 (mg·kg -1 )]]> 96.67 13.36 719.11 37.42 21.31 1.85 409.95 <![CDATA[Total heavy metals (mg·kg -1 )]]> 155.98 44.62 1280.97 49.89 33.25 2.03 459.05 <![CDATA[Heavy metal content (mg·kg -1 )]]> 185.56 52.77 1308.54 59.23 30.14 2.44 435.89 Heavy metal recovery rate (%) 84.06% 84.56% 97.89% 84.23% 110.32% 83.20% 105.31%

[0038] Table 2. Heavy metal content and heavy metal speciation in the coal gasification coarse slag after harmless treatment in Example 2

[0039] Types of heavy metals Cu Pb Cr Co As Sb Ni <![CDATA[Leaching concentration (mg·L -1 )]]> 0.001 ND 0.508 0.008 0.002 ND 0.082 Integrated Wastewater Discharge Standard GB 8978-1996 0.5 1.0 1.5 - 0.5 - 1.0

[0040] Table 3. Leaching toxicity of coal gasification coarse slag after harmless treatment in Example 2

[0041] The total amount, heavy metal speciation, and leaching toxicity of coal gasification slag after oxidation leaching separation treatment 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" (GB 8978-1996), meeting the standards for Class I solid waste. The above data prove that the coarse coal gasification slag treated by oxidation leaching separation treatment can be used for landfill and underground backfilling.

[0042] Example 3:

[0043] The total amount of heavy metals, the distribution of heavy metal speciation, and the results of toxicity 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. 10 g of coal gasification slag fine residue was mixed with a 0.50 mol / 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 0.05 mol / 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.

[0044] Types of heavy metals Cu Pb Cr Co As Sb Ni Metal exchangeable state F1 0.15 4.99 0.54 2.06 5.61 0.15 3.47 carbonate-bound F2 1.54 4.85 0.96 3.58 2.04 0.16 9.40 Iron / manganese oxide F3 0.40 341.38 28.69 11.00 57.51 0.32 10.61 Organic F4 23.03 63.42 11.37 8.74 26.18 0.33 15.04 Residual state F5 33.61 73.78 102.41 61.24 32.04 37.91 62.78 <![CDATA[Total heavy metals (mg·kg -1 )]]> 58.73 488.42 143.97 86.62 123.38 38.87 101.30 <![CDATA[Heavy metal content (mg·kg -1 ).]]> 71.55 469.56 178.54 107.88 115.36 45.38 123.96 Heavy metal recovery rate (%) 82.08% 104.02% 80.64% 80.29% 106.95% 85.65% 81.72%

[0045] Table 4. Heavy metal content and heavy metal speciation in the fine slag of coal gasification slag in Example 3

[0046] Types of heavy metals Cu Pb Cr Co As Sb Ni <![CDATA[Exchangeable metal F1 (mg·kg -1 )]]> 0.22 23.21 5.32 2.44 6.14 0.09 13.51 <![CDATA[Carbonate-bound F2 (mg·kg -1 ).]]> 1.40 6.14 7.81 2.26 4.53 0.06 14.40 <![CDATA[Iron / manganese oxide state F3 (mg·kg -1 )]]> 0.03 28.50 19.32 2.16 4.78 0.06 4.61 <![CDATA[Organic F4 (mg·kg -1 )]] 23.63 33.81 7.98 7.09 8.73 0.65 6.76 <![CDATA[Residual态F5 (mg·kg -1 )]]> 25.77 24.75 55.99 31.72 26.42 7.99 3.19 <![CDATA[Total heavy metals (mg·kg -1 )]]> 51.05 116.41 96.42 45.67 50.60 8.85 42.47 <![CDATA[Heavy metal content (mg·kg -1 ).]]> 62.18 130.43 117.86 48.86 58.75 7.53 41.98 Heavy metal recovery rate (%) 82.10% 89.25% 81.81% 93.47% 86.13% 117.53% 101.17%

[0047] Table 5. Heavy metal content and heavy metal speciation in the coal gasification slag after harmless treatment in Example 3

[0048] Types of heavy metals Cu Pb Cr Co As Sb Ni <![CDATA[Leaching concentration (mg·L -1 ).]]> 0.001 0.033 0.433 0.055 0.032 ND 0.063 Integrated Wastewater Discharge Standard GB 8978-1996 0.5 1.0 1.5 - 0.5 - 1.0

[0049] Table 6. Leaching toxicity of coal gasification fine slag after harmless treatment in Example 3

[0050] 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" (GB 8978-1996), 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.

[0051] This solution discloses an oxidation leaching separation system 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.

[0052] As is known from common technical knowledge, this utility model 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 in all respects and are not the only ones. All modifications within the scope of this utility model or its equivalents are included in this utility model.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and not to limit it. Although the utility model 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 this utility model. Any modifications or equivalent substitutions that do not depart from the spirit and scope of this utility model should be covered within the protection scope of the claims of this utility model.

Claims

1. A system for the oxidative leaching separation treatment of heavy metals from coal gasification slag, characterized in that, The application relates to a three-stage connection setting multi-element radical catalytic oxidation pool (8), which is provided with a feeding port, a dosing port, a gas collecting port and a water outlet, wherein the feeding port is connected with a slurry pump (1), the dosing port is connected with an ozone generator (4) and a hydrogen peroxide storage tank (2) with a hydrogen peroxide dosing pump (3) through pipelines, the gas collecting port is connected with an ozone destroyer, the water outlet is connected with a first slurry-water separator (5) with a sand discharging port and an overflow port, wherein the overflow port is connected with the multi-element radical catalytic oxidation pool (8) with a valve and a first backflow pump (6) through a pipeline, the sand discharging port is connected with a leaching pool (13) set in three stages, the leaching pool (13) is provided with a feeding port, a dosing port and a water outlet, wherein the feeding port is connected with the sand discharging port of the first slurry-water separator (5), the dosing port is connected with an oxalic acid and citric acid leaching agent storage tank (9) with a leaching agent dosing pump (10) through a pipeline, the water outlet is connected with a second slurry-water separator (11) with a sand discharging port and an overflow port, wherein the overflow port is connected with the leaching pool (13) with a valve and a second backflow pump (12) through a pipeline, and the sand discharging port is connected with an intermediate storage tank (15). The multi-element radical catalytic oxidation pool (8) and the leaching pool (13) are both internally provided with annular backflow structures, and the annular backflow structures are provided with stirrers.

2. The system for the oxidative leaching separation treatment of heavy metals from coal gasification slag according to claim 1, characterized in that, The multi-element radical catalytic oxidation pool (8) and the leaching pool (13) are both provided with aeration devices at the bottom, and the aeration devices are connected with air blowers through pipelines.

3. The system for the oxidative leaching separation treatment of heavy metals from coal gasification slag according to claim 1, characterized in that, The first slurry-water separator (5) and the second slurry-water separator (11) are both internally provided with 70-80 mesh vibration screens, and the particle size of the separated coal gasification residues is not less than 0.2 mm.

4. The process for the oxidative leaching separation of heavy metals from coal gasification slag according to claim 1, characterized in that, ​

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