Harmless treatment system and method for coal gasification slag

Abstract

The invention discloses a coal gasification slag harmless treatment system and method in the technical field of solid waste treatment, and the system comprises a screening device for screening coal gasification slag to obtain oversize materials and undersize materials; the grinding device is used for grinding the oversize materials to obtain ground oversize materials; the separation device is used for carrying out residual carbon separation treatment on the undersize material to obtain concentrate and gasified tailings, the concentrate is dehydrated to serve as a residual carbon product, and the gasified tailings after dehydration and the ground oversize material serve as a mixed material to enter the compound leaching device; the compound leaching device is used for carrying out compound leaching and dehydration treatment on the mixed material; the chemical oxidation device is used for carrying out chemical oxidation and dehydration treatment on the mixed material subjected to compound leaching and dehydration treatment; and the washing adjustment device is used for carrying out washing adjustment and dehydration treatment on the mixed material subjected to chemical oxidation and dehydration treatment. The coal gasification slag produced in the coal chemical industry is subjected to systematic harmless treatment, and the effect of turning waste into wealth is achieved.

Description

Technical Field

[0001] The invention relates to a system and method for harmless disposal of coal gasification slag, belonging to the technical field of solid waste treatment. Background Art

[0002] As a technology for clean utilization of coal, coal gasification produces synthesis gas through the reaction of coal with oxygen or steam at high temperature. However, solid wastes such as coal gasification slag will be produced during the coal gasification process. At present, the national output of coal gasification slag exceeds 60 million tons, and it is increasing year by year. There is no effective comprehensive utilization method for coal gasification slag, and the main disposal method is: slag yard storage. Coal gasification slag contains a large amount of unreacted solid residues, a variety of heavy metals such as copper (Cu), lead (Pb) and chromium (Cr), COD, etc. A large amount of coal gasification slag is stored on land, causing serious water-soil-air complex pollution, and it is urgently needed to be disposed of on a large scale.

[0003] The results of elemental analysis of coal gasification slag show that it contains a lot of SiO2 (45-55%), Al2O3 (about 20%), Fe2O3 (about 10%) and unburned carbon (about 15-25%). Due to the formation of glassy state, some inorganic metal elements may be encapsulated in the aluminosilicate lattice structure, and some metals may exist in the coal gasification slag in the form of exchangeable state, carbonate-bound state, iron-manganese-bound state, organic matter and sulfide-bound state and residual state, which poses a risk of heavy metal leaching; some organic matter may seep into the medium from unburned carbon, causing an increase in COD in the water body, so it also needs attention; the proportion of unburned carbon in coal gasification slag is relatively high, so research on residual carbon recovery and high-value utilization can save resources and create greater economic value.

[0004] The physical and chemical properties of coal gasification slag vary depending on the type of coal and the gasification process. It has the characteristics of complex composition, uneven heavy metal content, and variable physical and chemical properties. So far, the harmless disposal and resource utilization rate of coal gasification slag is low. In recent years, researchers have tried to develop more effective and environmentally friendly technologies to solve the problem of reaching the standards for residual carbon, heavy metals, COD and other indicators in coal gasification slag. Common treatment methods mainly include physical methods, chemical methods and biological methods. Among them, physical methods mainly include mechanical sorting and gravity sorting, which can separate some large-particle residues and carbon, but have limited removal effects on heavy metals and cannot meet environmental protection requirements; chemical methods include solidification / stabilization treatment, chemical precipitation, etc., which can effectively reduce the mobility and bioavailability of heavy metals, but may produce new pollutants. The above methods are often limited to extracting valuable elements or removing individual harmful elements, and cannot systematically achieve the harmless disposal of coal gasification slag. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a system and method for harmless disposal of coal gasification slag, which performs a series of treatments on the coal gasification slag produced in the coal chemical industry, systematically realizes the harmless disposal of the coal gasification slag, and realizes the effect of turning waste into treasure.

[0006] To achieve the above object, the present invention is implemented by adopting the following technical solutions: In a first aspect, the present invention provides a system for harmless disposal of coal gasification slag, comprising: Screening device: Screening the coal gasification slag to obtain the oversize material and undersize material; Grinding device: grinding the material on the screen to obtain the ground material on the screen; Sorting device: The material under the screen is subjected to residual carbon sorting to obtain concentrate and gasification tailings, wherein the concentrate is dehydrated as the residual carbon product, and the gasification tailings are dehydrated and mixed with the ground material on the screen as a mixed material and enter the compounding and leaching device; Compounding and leaching device: compounding, leaching and dehydrating the mixed materials; Chemical oxidation device: chemical oxidation and dehydration treatment of the mixed material after compound leaching and dehydration treatment; Water washing and regulating device: for water washing, regulating and dehydrating the mixed material after chemical oxidation and dehydration treatment; Heavy metal solidification device: heavy metal solidification treatment is carried out on the mixed material after water washing, adjustment and dehydration treatment.

[0007] Furthermore, it also includes a wastewater treatment and reuse device, which recycles the wastewater dehydrated by each device in the coal gasification slag harmless disposal system, removes organic matter and heavy metals, and then flows it back to each device in the coal gasification slag harmless disposal system.

[0008] Furthermore, the screening device includes a screening machine, and the sieve mesh used by the screening machine has an aperture of 0.5 mm-3.0 mm.

[0009] Furthermore, the sorting device includes a sorting machine, and the sorting machine is a spiral sorting machine, TBS, flotation machine or flotation column.

[0010] Furthermore, the grinding device includes a ball mill, and the output particle size of the ball mill is ≤2.0 mm.

[0011] Furthermore, the compound elution device includes an elution tank and an elution agent adding device, and the elution agent adding device adds elution agent to the elution tank through a dosing pump, the elution tank is provided with a pH detection port, and the elution agent includes at least one of an organic acid, an inorganic acid, an organic chelating agent and a surfactant.

[0012] Furthermore, the chemical oxidation device includes a chemical oxidation tank and an oxidant adding device, and the oxidant adding device adds oxidant to the chemical oxidation tank through a dosing pump, and the oxidant is selected from hydrogen peroxide (H2O2), ozone or persulfate.

[0013] Furthermore, the water washing adjustment device includes a water washing tank and a regulator adding device, and the regulator adding device adds a pH regulator or water into the water washing tank through a dosing pump.

[0014] Furthermore, the heavy metal solidification device includes a solidification tank and a solidifying agent adding device, the solidifying agent adding device adds the solidifying agent to the solidification tank through a dosing pump, the solidification tank adopts bioleaching technology and / or a multi-stage passivation method, wherein the bioleaching uses a composite strain, and the solidifying agent uses cement, quicklime, Ca(OH)2, Na2S or Na2S2O3.

[0015] In a second aspect, the present invention provides a method for harmless disposal of coal gasification slag, comprising the following steps: Screening the coal gasification slag to obtain oversize material and undersize material; Grinding the material on the screen to obtain ground material on the screen; The undersize material is subjected to residual carbon separation to obtain concentrate and gasification tailings, wherein the concentrate is dehydrated as the residual carbon product, and the gasification tailings are dehydrated and mixed with the ground oversize material to enter the compounding and leaching device as a mixed material; Compounding, leaching and dehydrating the mixed materials; Chemically oxidizing and dehydrating the mixed material after the compound leaching and dehydration treatment; Carry out water washing, adjustment and dehydration treatment on the mixed material after chemical oxidation and dehydration treatment; The mixed material after washing, adjustment and dehydration is subjected to heavy metal solidification treatment.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention provides a method for harmlessly treating coal gasification slag produced in the coal chemical industry, systematically realizing the harmless treatment of coal gasification slag and realizing the effect of turning waste into treasure, which can not only solve the solid waste treatment problem in the coal chemical industry, but also bring certain economic benefits to the enterprise, and completely solve the problem that coal gasification slag in the coal chemical industry cannot be treated except for storage in the slag field; 2. The raw materials treated by the present invention are suitable for gasification coarse slag and gasification fine slag. The coal gasification slag after harmless disposal can meet the parameter standards of general industrial solid waste, and can be used as raw materials for underground filling, cement, building materials and other raw materials and raw materials for high value-added products, thereby realizing the harmless disposal and resource utilization of coal gasification slag; 3. In the present invention, the eluent is preferably selected from organic acids, inorganic acids, organic chelating agents, surfactants, etc., and heavy metals are eluted from the coal gasification slag by acidic, alkaline or compound eluents. When oxalic acid and citric acid are used as eluents, the eluents are biodegradable, reducing environmental impact. Compared with traditional methods, they have more environmental advantages and are environmentally friendly. In addition, by optimizing the treatment conditions, the use of chemical reagents and treatment costs are reduced. At the same time, the coal gasification slag after harmless treatment can be recycled as a resource, increasing economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] 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: Figure 1 A schematic diagram of a treatment process of a coal gasification slag harmless disposal system provided in Embodiment 1 of the present invention; Figure 2 A schematic diagram of a treatment process of performing residual carbon separation, leaching and oxidation to remove heavy metals from coal gasification slag in a coal gasification slag harmless disposal system provided in Embodiment 1 of the present invention; In the figure: 1. Screening device; 2. Sorting device; 3. Grinding device; 4. Compound elution device; 5. Chemical oxidation device; 6. Water washing and regulating device; 7. Heavy metal solidification device; 8. Wastewater treatment and reuse device; 9. Eluent adding device; 10. Oxidant adding device; 11. Regulator adding device; 12. Curing agent adding device. DETAILED DESCRIPTION

[0018] 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.

[0019] 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.

[0020] Embodiment 1: This embodiment provides a harmless disposal system for coal gasification slag. The core of the solution is the removal of residual carbon, COD and heavy metals, and their removal and stabilization. Figure 1It is understood that it includes: screening device 1, sorting device 2, grinding device 3, compound leaching device 4, chemical oxidation device 5, water washing and regulating device 6, heavy metal solidification device 7, and wastewater treatment and reuse device 8. The gasification slag is first classified by the screening device 1, and the under-screen material enters the sorting device 2, and the over-screen material enters the grinding device 3; the gasification tailings after sorting and the ground under-screen material are mixed and successively enter the compound leaching device 4, chemical oxidation device 5, water washing and regulating device 6 and heavy metal solidification device 7 to remove the residual carbon, heavy metal elements, COD in the gasification slag and ensure that the pH value meets the standard. The raw materials treated by this scheme are suitable for gasification coarse slag and gasification fine slag. The gasification slag after harmless disposal can meet the parameter standards of general industrial solid waste, and can be used as raw materials for underground filling, cement, building materials and other raw materials and raw materials for high value-added products, so as to realize the harmless disposal and resource utilization of gasification slag. Specifically: The screening device 1 includes a screening machine with a coal gasification slag inlet, an outlet for screened material and an outlet for screened material. The coal gasification slag is screened by screening to separate the material into large-particle material on the screen and small-particle material under the screen. When the organic matter content in the large-particle material on the screen is ≤2.0%, pre-screening is beneficial to reduce the load entering the next stage sorting unit. The mesh aperture of the screening machine in this embodiment is 0.5mm-3.0mm.

[0021] The sorting device 2 includes a pre-slurry mixer with a water inlet and a sorting machine. The inlet of the pre-slurry mixer is connected to the outlet of the undersize material of the screening machine, and the outlet of the pre-slurry mixer is connected to the feed inlet of the sorting machine. The sorting machine sorts out two or more products including light products and heavy products, wherein the light product (residual carbon) is discharged from the light product outlet of the sorting machine, and other products are collectively referred to as heavy products (gasification tailings) and are discharged from the heavy product outlet of the sorting machine. The sorting machine is preferably a spiral sorting machine, TBS, flotation machine or flotation column, which can achieve an organic matter content in the gasification tailings of less than 2.0%. In this embodiment, the dry basis residual carbon content in the gasification tailings is ≤2.0%.

[0022] The grinding device 3 includes a ball mill with a feed port, a discharge port and a water inlet, wherein the feed port of the ball mill is connected to the outlet of the material on the screen of the screening machine; the ball mill grinds the material on the screen, and its function is to expose the encapsulated heavy metals and residual carbon and other elements by grinding the coal gasification slag particles, which is beneficial to improve the effect of harmless disposal. In this embodiment, the discharge particle size of the ball mill is ≤2.0mm.

[0023] The compound elution device 4 includes an elution tank with a feed port, a discharge port and a water replenishment port, an eluent adding device 9 and a dehydration device, wherein the feed port of the elution tank is connected to the discharge port of the ball mill of the grinding device 3 and the heavy product outlet of the sorting machine of the sorting device 2, and the discharge port of the elution tank is connected to the inlet of the matching dehydration equipment. The eluent adding device 9 adds eluent to the elution tank through a dosing pump, wherein the elution tank is provided with a pH detection port, and the eluent of the elution tank contains one or two or more eluents. The eluent is preferably selected from: organic acid, inorganic acid, organic chelating agent, surfactant, etc. Heavy metals are eluted from the gasification slag by acidic, alkaline or compound eluents. This embodiment uses oxalic acid and citric acid as eluents. The eluent is biodegradable and reduces environmental impact. Compared with traditional methods, it has more environmental advantages and is environmentally friendly. By optimizing the treatment conditions, the use of chemical reagents and the treatment cost are reduced. At the same time, the gasification slag after harmless treatment can be recycled as a resource, which increases economic benefits. The leaching tank is equipped with a pH detection port, and the type of leaching agent added is adjusted by detecting the pH value of the leaching liquid; the dehydration equipment of the composite leaching device 4 preferably uses a linear vibrating screen, a slag-water separator or a dehydration chute, etc., to remove moisture and leaching agent from the gasification slag after leaching.

[0024] The chemical oxidation device 5 includes a chemical oxidation tank with a feed port, a discharge port and a water replenishment port, an oxidant adding device 10 and a dehydration device, wherein the feed port of the chemical oxidation tank is connected to the outlet of the dehydration device of the compound elution device 4, the discharge port of the chemical oxidation tank is connected to the inlet of the matching dehydration device, and the oxidant adding device 10 adds an oxidant to the chemical oxidation tank through a dosing pump. The oxidant is preferably selected from: hydrogen peroxide (H2O2), ozone, persulfate, etc. The advanced oxidation process of the chemical oxidation device 5 can remove soluble organic matter, volatile organic matter, and semi-volatile organic matter leached from the gasification slag. The oxidant can also convert the heavy metals in the gasification slag from a low-valent state to a high-valent state, and convert it into a form that is easier to remove by water washing; the dehydration equipment of the chemical oxidation device 5 preferably uses a linear vibrating screen, a slag-water separator or a dehydration chute, etc., to remove moisture and oxidants from the gasification slag after chemical oxidation.

[0025] The water washing regulating device 6 includes a water washing tank with a feed port, a discharge port and a water replenishment port, a regulator adding device 11 and a dehydration device, wherein the feed port of the water washing tank is connected to the dehydration equipment outlet of the compound elution device 5, the discharge port of the water washing tank is connected to the dehydration equipment inlet of the water washing regulating device 6, and the regulator adding device 11 adds pH regulator or water to the water washing tank through a dosing pump. The functions of the water washing regulating device 6 are to remove residual oxidants and eluents in the gasification slag and to adjust the pH value of the material by adding a pH regulator; the dehydration equipment of the water washing regulating device 6 preferably uses a linear vibrating screen, a slag-water separator or a dehydration chute, etc., to remove moisture, residual oxidants and eluents in the gasification slag.

[0026] The heavy metal solidification device 7 comprises a solidification tank with a feed port, a discharge port and a water replenishment port, a solidification agent adding device 12 and a dehydration device, wherein the feed port of the solidification tank is connected to the outlet of the dehydration device of the water washing and regulating device 6, the discharge port of the solidification tank is connected to the inlet of the dehydration device of the heavy metal solidification device 7, and the solidification agent adding device 12 adds the solidification agent to the solidification tank through a dosing pump. The solidification tank adopts biological leaching technology and / or multi-stage passivation mode, wherein the biological leaching preferably uses composite strains such as iron-thiobacillus and thiooxidans, and the solidification agent preferably uses cement, quicklime, Ca(OH)2, Na2S, Na2S2O3, etc. The heavy metal solidification device 7 can be used to perform heavy metal solidification treatment on the coal gasification slag after chemical oxidation-chemical leaching to ensure that the heavy metals in the coal gasification slag will not enter the groundwater under long-term leaching. The dehydration equipment of the heavy metal solidification device 7 is preferably a linear vibrating screen, a slag-water separator or a dehydration chute, etc., to remove moisture and solidifying agent from the solidified coal gasification slag.

[0027] The wastewater treatment and reuse device 8 includes a water inlet, a drain outlet, a water replenishment port and an overflow port. The water inlet of the wastewater reuse device 8 is respectively connected to the drain outlets of the dehydration equipment of the compound leaching device 4, the chemical oxidation device 5, the water washing adjustment device 6 and the heavy metal solidification device 7. The drain outlet of the wastewater reuse device 8 is respectively connected to the water inlet of the pre-slurry mixer, the water inlet of the ball mill, the water replenishment port of the chemical oxidation tank, the water replenishment port of the compound leaching tank, the water replenishment port of the water washing tank and the water replenishment port of the solidification tank. The wastewater treatment and reuse device 8 is a matching washing, chemical oxidation, leaching wastewater treatment and circulating water reuse device, which removes organic matter and heavy metals from the leaching wastewater generated in the process of harmless treatment of coal gasification slag, and the final effluent water quality meets the reuse water standard.

[0028] It should be noted that the chemical oxidation tank, leaching tank, water washing tank, and solidification tank (collectively referred to as reaction tanks) are all equipped with a reflux pump. The inlet of the reflux pump is connected to the outlet of the corresponding dehydration equipment, and the outlet of the reflux pump is connected to the water inlet of each reaction tank.

[0029] Since the physical and chemical properties of coal gasification slag vary depending on the type of coal and gasification process, any general processing technology must be sufficiently flexible and adaptable. Therefore, some embodiments of the present invention have the following flexibility, for example: (i) Without prior screening, the coal gasification slag directly enters the residual carbon separation - chemical oxidation - composite leaching - heavy metal solidification to obtain the coal gasification slag after harmless disposal; (ii) When the pre-screened material meets the heavy metal and other indicators and has other uses, it can be directly used as a product without being mixed with the screened gasification tailings after sorting and entering the subsequent harmless treatment unit; (iii) Based on the test results of heavy metal content and existence form, gasification tailings and oversize materials can be directly sent to the subsequent harmless treatment unit without going through the grinding unit; (iv) The material after water washing and adjustment can be directly converted into harmless coal gasification slag without passing through a heavy metal solidification unit.

[0030] In this embodiment, after the coal gasification slag is screened and graded with Φ2.0mm, the material on the screen enters the ball mill through the chute and is ground to less than 2.0mm, and the material under the screen less than 2.0mm enters the slurry preparation device for slurry adjustment (the slurry-liquid ratio is between 5-30% according to the actual sorting requirements); the mixed slurry is pumped into the sorting machine for residual carbon sorting, and after sorting by the sorting machine, two materials are selected: concentrate and gasification tailings. The above materials enter the concentrate barrel and the tailings barrel respectively. The concentrate slurry is pumped to the concentrate linear vibrating screen for dehydration, and is used as a residual carbon product. The gasification tailings are dehydrated by a slag-water separator; the dehydrated tailings and the ground materials are mixed and entered into the compound leaching tank for elution. The compound leaching tank is provided with a pH detection port. According to the feedback pH value, the eluent is selectively added to the leaching tank by a dosing pump to keep the eluent concentration always maintained at the optimal condition; the slag-water mixture in the compound leaching tank is dehydrated by the slag-water separator; it enters the chemical oxidation tank, and an oxidant is added to the oxidation tank through a dosing device to achieve the reaction degradation of organic matter in the coal gasification slag and promote the release of organically bound heavy metals; the slag-water mixture in the chemical oxidation tank is dehydrated by the slag-water separator, and then enters the water washing regulating tank to remove residual oxidants and eluents; the slag-water mixture in the water washing regulating tank is dehydrated by the slag-water separator, and then enters the solidification tank, and the heavy metals remaining in the coal gasification slag are solidified and stabilized by adding a solidifying agent to the solidification tank. The process technology route of the wastewater treatment and reuse device 8 is: adjusting pH, coagulation and precipitation, catalytic oxidation treatment, and finally reaching the recycling water index after biological treatment. After being treated by the above-mentioned harmless disposal device, the residual carbon product can be used as a boiler blending raw material, and the various parameter indicators of the gasification tailings can meet the general industrial solid waste type I parameter standards. It should be noted that there is no restriction on the order of application of the screening device, grinding device, sorting device, compound elution device, and chemical oxidation device, and the addition and deletion of some device units are permitted in the present invention.

[0031] Embodiment 2: According to the system for harmless disposal of coal gasification slag of the present invention, reference is made to Figure 2 It is understood that the harmless disposal method of combined treatment of sorting pretreatment, chemical oxidation and leaching in the laboratory can effectively remove residual carbon organic matter, COD and heavy metals in the gasification slag, and finally achieve the harmlessness and resource utilization of the gasification slag, effectively improving the treatment efficiency and economic benefits. The specific implementation steps are as follows: Pretreatment of residual carbon separation: Pre-separation of residual carbon is performed to reduce the amount of gasification slag to be processed and improve the processing efficiency. It is suitable for gasification slag with high carbon content. 2 The solution sorts the gasification slag, recovers the residual carbon, reduces the amount of gasification slag to be processed in the subsequent units, and improves the efficiency of subsequent processing. See Table 1 for the results of the small floating and sinking test of gasification slag. After the residual carbon is recovered, the gasification tailings with a density of ≥2.0g / cm3 enter the next oxidation treatment unit.

[0032] Chemical oxidation treatment: Under the reaction conditions of oxidation time 2h, solid-liquid ratio 1:5, and oxidant concentration 0.5 M, the COD of the gasification tailings leachate can be reduced from 40 mg / L to 10 mg / L (groundwater category IV standard).

[0033] Compound leaching: hydrochloric acid, citric acid and oxalic acid all have good leaching and removal effects on excessive metals (mercury, arsenic, antimony) in the gasification slag leachate. Among them, citric acid has a higher removal effect on antimony (97.8%), and oxalic acid has a higher removal effect on arsenic (80.9%). The compound leaching experiment shows that after leaching with a specific compound ratio and number of times, the concentration of heavy metals in the gasification tailings leachate can be reduced to below the fourth category groundwater standard.

[0034] In this embodiment, through the combined action of chemical oxidation and elution, the heavy metal removal rate is high, especially the removal effect of Cu, Pb and Cr is remarkable, reaching the standards of resource utilization and harmlessness.

[0035] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0036] 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.

[0037] 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 harmless disposal of coal gasification slag, characterized in that: include: Screening device: Screening the coal gasification slag to obtain the oversize material and undersize material; Grinding device: grinding the material on the screen to obtain the ground material on the screen; Sorting device: The material under the screen is subjected to residual carbon sorting to obtain concentrate and gasification tailings, wherein the concentrate is dehydrated as the residual carbon product, and the gasification tailings are dehydrated and mixed with the ground material on the screen as a mixed material and enter the compounding and leaching device; Compounding and leaching device: compounding, leaching and dehydrating the mixed materials; Chemical oxidation device: chemical oxidation and dehydration treatment of the mixed material after compound leaching and dehydration treatment; Water washing and regulating device: for water washing, regulating and dehydrating the mixed material after chemical oxidation and dehydration treatment; Heavy metal solidification device: heavy metal solidification treatment is carried out on the mixed material after water washing, adjustment and dehydration treatment.

2. The coal gasification slag harmless disposal system according to claim 1 is characterized in that: It also includes a wastewater treatment and reuse device, which recycles the wastewater dehydrated by each device in the coal gasification slag harmless disposal system, removes organic matter and heavy metals, and then flows it back to each device in the coal gasification slag harmless disposal system.

3. The coal gasification slag harmless disposal system according to claim 1 is characterized in that: The screening device comprises a screening machine, and the sieve mesh aperture used by the screening machine is 0.5mm-3.0mm.

4. The coal gasification slag harmless disposal system according to claim 1 is characterized in that: The sorting device comprises a sorting machine, and the sorting machine is selected from a spiral sorting machine, a TBS, a flotation machine or a flotation column.

5. The coal gasification slag harmless disposal system according to claim 1 is characterized in that: The grinding device comprises a ball mill, and the discharge particle size of the ball mill is ≤2.0 mm.

6. The coal gasification slag harmless disposal system according to claim 1 is characterized in that: The compound elution device comprises an elution tank and an elution agent adding device, and the elution agent adding device adds elution agent to the elution tank through a dosing pump. The elution tank is provided with a pH detection port, and the elution agent comprises at least one of an organic acid, an inorganic acid, an organic chelating agent and a surfactant.

7. The harmless disposal system for coal gasification slag according to claim 1 is characterized in that: The chemical oxidation device comprises a chemical oxidation pool and an oxidant adding device, and the oxidant adding device adds oxidant to the chemical oxidation pool through a dosing pump, and the oxidant is selected from hydrogen peroxide (H2O2), ozone or persulfate.

8. The coal gasification slag harmless disposal system according to claim 1 is characterized in that: The water washing adjustment device comprises a water washing tank and a regulator adding device, and the regulator adding device adds a pH regulator or water into the water washing tank through a dosing pump.

9. The coal gasification slag harmless disposal system according to claim 1 is characterized in that: The heavy metal solidification device comprises a solidification tank and a solidification agent adding device, wherein the solidification agent adding device adds the solidification agent to the solidification tank through a dosing pump, and the solidification tank adopts bioleaching technology and / or a multi-stage passivation method, wherein the bioleaching uses a composite strain, and the solidification agent uses cement, quicklime, Ca(OH)2, Na2S or Na2S2O3.

10. A method for harmless disposal of coal gasification slag, characterized in that: The steps include: Screening the coal gasification slag to obtain oversize material and undersize material; Grinding the material on the screen to obtain ground material on the screen; The undersize material is subjected to residual carbon separation to obtain concentrate and gasification tailings, wherein the concentrate is dehydrated as the residual carbon product, and the gasification tailings are dehydrated and mixed with the ground oversize material to enter the compounding and leaching device as a mixed material; Compounding, leaching and dehydrating the mixed materials; Chemically oxidizing and dehydrating the mixed material after the compound leaching and dehydration treatment; Carry out water washing, adjustment and dehydration treatment on the mixed material after chemical oxidation and dehydration treatment; The mixed material after washing, adjustment and dehydration is subjected to heavy metal solidification treatment.

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