High-temperature harmless treatment method for overhaul slag

Abstract

The invention discloses a high-temperature innocent treatment method for overhaul slag, which belongs to the technical field of resource recycling and reutilization, and comprises the following steps: (1) carrying out iron removal, crushing and vibratory sedimentation on the overhaul slag to obtain overhaul slag particles; (2) uniformly mixing the overhaul slag with a drying agent, and uniformly stacking to obtain a mixture; (3) uniformly mixing the mixture, a calcium-containing raw material, a silicon-containing raw material and an aluminum-containing raw material to obtain a sintered raw material; and (4) sintering, crushing and cooling the sintered raw material to obtain the harmless sintered material. Soluble fluorine is efficiently fixed and stable fluoride is formed through the mineral solidification effect formed by calcium, silicon and aluminum, the content of the soluble fluorine is smaller than 100 mg / kg, migration pollution is prevented, meanwhile, sinter can be reutilized, harmless full circulation is achieved, and the problem of industrial utilization of electrolytic aluminum overhaul slag hazardous waste is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of resource recycling and reuse, and particularly relates to a method for high-temperature harmless treatment of overhaul slag. Background Art

[0002] Overhaul slag has become one of the main solid waste pollution sources in the electrolytic aluminum industry. Overhaul slag mainly includes carbon materials (such as cathode and side carbon blocks), impermeable materials, refractory bricks, cold ramming paste, insulating bricks, insulating boards, etc. Its composition is complex, containing highly toxic soluble fluorides and cyanides, and has been included in the "National List of Hazardous Wastes" (2021 Edition). Due to its diverse composition and difficult separation and extraction, the treatment and disposal of overhaul slag pose a threat to the environment and human health, restricting the sustainable development of the electrolytic aluminum industry.

[0003] The treatment problem of electrolytic aluminum overhaul slag plagues the electrolytic aluminum industry. The main harmful substances include soluble fluorides and cyanides, and the leachate of long-term piled overhaul slag may pollute surface water and groundwater. Due to the lack of hazardous waste landfill treatment facilities in most enterprises, electrolytic aluminum overhaul slag faces the dilemma of having no reasonable disposal way. Therefore, it is urgent to find a final disposal solution for hazardous wastes such as electrolytic aluminum overhaul slag, promote the green and healthy development of the aluminum industry, and provide necessary support and guarantee for the sustainable revitalization of the industry, which has important practical significance.

[0004] Currently, the treatment methods of overhaul slag mainly include physical separation, wet leaching, pyromelting, etc. Among them, the pyromelting technology can effectively destroy the harmful components in the overhaul slag and transform it from hazardous waste into general solid waste, achieving an essential transformation of its properties. However, due to the problems such as complex composition and uneven mineral composition still existing in the general solid waste generated after pyromelting disposal, its large-scale and full-quantification resource utilization still faces great challenges. The existing landfill treatment method not only has high costs but also may cause secondary pollution, restricting the environmental friendliness and economic feasibility of pyromelting disposal. Therefore, how to improve the resource utilization rate of the solid waste after pyromelting disposal and promote its high-value application has become one of the problems to be solved urgently. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for high-temperature harmless treatment of overhaul slag.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A method for high-temperature harmless treatment of overhaul slag, comprising the following steps:

[0008] (1) Subject the overhaul slag to iron removal, crushing, and vibration sedimentation to obtain overhaul slag particles;

[0009] (2) Mix the overhaul slag and the desiccant evenly and stack them evenly to obtain a mixed material;

[0010] (3) Mix the mixed material, the calcium-containing raw material, the silicon-containing raw material, and the aluminum-containing raw material evenly to obtain a sintering raw material;

[0011] (4) Sinter, crush, and cool the sintering raw material to obtain a harmless sintered material.

[0012] As a preferred embodiment of the present invention, the power of the vibration settlement is 30-50 Hz, and the amplitude is 6-10 mm.

[0013] As a preferred embodiment of the present invention, the mass ratio of the overhaul slag to the desiccant is 1:(0.02-0.05).

[0014] As a preferred embodiment of the present invention, the desiccant includes at least one of calcium oxide, silica gel, activated carbon, bentonite, and montmorillonite.

[0015] As a preferred embodiment of the present invention, the calcium-containing raw material includes at least one of limestone, dolomite, sepiolite, perlite, steel slag, desulfurized gypsum, fly ash, slag, paper sludge, and lime slag from the chlor-alkali industry.

[0016] As a preferred embodiment of the present invention, the silicon-containing raw material includes at least one of quartz, quartz sand, high-silica sandstone, opal, recycled glass, feldspar, kaolin, bentonite, nepheline, and pyrophyllite.

[0017] As a preferred embodiment of the present invention, the aluminum-containing raw material includes at least one of bauxite, gibbsite, diaspore, clay, feldspar, kaolin, bentonite, nepheline, pyrophyllite, red mud, electrolytic aluminum waste residue, aluminum ash, and aluminum slag.

[0018] As a preferred embodiment of the present invention, the mass percentage content of the main element components of the sintering raw material is: calcium oxide 5-75%, silicon dioxide 20-70%, aluminum oxide 8-35%, and iron oxide 5-20%.

[0019] As a preferred embodiment of the present invention, the mass ratio of the mixed material, the calcium-containing raw material, the silicon-containing raw material, and the aluminum-containing raw material is (5-30):(8-60):(12-35):(10-27).

[0020] As a preferred embodiment of the present invention, the sintering temperature is 800-1400 °C, and the sintering time is 2-6 h.

[0021] The beneficial effects of the present invention are as follows: (1) By utilizing the mineral solidification effect formed by calcium, silicon, and aluminum, the present invention efficiently fixes soluble fluorine and forms stable fluorides (such as fluorides or combinations of several forms in the form of vitreous, calcium-magnesium-based, silicate-based, aluminate-based, sulfoaluminate, ferroaluminate, and aluminosilicate-based fluorides or fluorine-containing solid solutions, etc.), making the soluble fluorine content less than 100 mg / kg, preventing migration and pollution. At the same time, the sintered product can be recycled, realizing harmless full-cycle utilization and breaking through the industrial utilization problem of hazardous waste from the overhaul slag of electrolytic aluminum. (2) The present invention mixes a desiccant with the mixture to prevent cyanide from hydrolyzing to form highly toxic hydrocyanic acid (HCN) during storage, ensuring its storage stability. At the same time, in the high-temperature treatment stage, by controlling the temperature (≥800 °C), the cyanide undergoes a decomposition reaction in an oxidative atmosphere to generate substances such as nitrogen (N2) and carbon dioxide (CO2), achieving harmless disposal and avoiding secondary pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 XRD pattern of the sintered material in Example 1.

[0023] Figure 2 XRD pattern of the sintered material in Example 2. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0025] In the present application, among the technical features described in an open-ended manner, there are included closed technical solutions composed of the listed features, as well as open technical solutions including the listed features.

[0026] In the present application, regarding numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0027] In the present application, there are no particular restrictions on the specific dispersion and stirring treatment methods.

[0028] Unless otherwise specified, the component raw materials or instruments used in the embodiments and comparative examples of the present invention are all commercially available raw materials or instruments, and the component raw materials used in each parallel experiment are of the same kind.

[0029] The following examples are provided to facilitate the understanding of the present invention. These examples are not provided to limit the scope of the claims.

[0030] Example 1

[0031] A method for high-temperature harmless treatment of overhaul slag includes the following steps:

[0032] (1) Use a magnetic separator to perform magnetic separation of the overhaul slag to remove iron at a magnetic field intensity of 1000 GS. After iron removal, place it in a crusher and crush it to a particle size within 5 cm, and then place it in a vibration sedimentation device for vibration sedimentation to remove aluminum impurities to obtain overhaul slag particles; wherein, the frequency of vibration sedimentation is 40 Hz and the amplitude is 8 mm;

[0033] (2) Mix the overhaul slag and calcium oxide evenly according to a mass ratio of 1:0.05, and stack them evenly up and down to obtain a mixed material;

[0034] (3) Mix the mixed material and other raw materials evenly according to the ratio in Table 1, and grind them with a mill to a residue on a 80-micron sieve of less than 15% to obtain sintering raw meal.

[0035] (4) Sinter the sintering raw meal at 1000 °C for 4 h, crush it, and cool it to obtain harmless sintered material. This implementation mainly utilizes the solid solution mechanism of glass to fluoride to achieve the purpose of solidifying fluorine. The harmless sintered material is detected for cyanide and leached fluorine content in the sintered material according to GB5085.3-2007 "Identification Standard for Toxicity of Leaching of Hazardous Wastes" as shown in Table 1, and the XRD pattern of the sintered material in this example is as Figure 1 shown.

[0036] Table 1

[0037]

[0038] Example 2

[0039] A method for high-temperature harmless treatment of overhaul slag includes the following steps:

[0040] (1) Use a magnetic separator to perform magnetic separation of the overhaul slag to remove iron at a magnetic field intensity of 1000 GS. After iron removal, place it in a crusher and crush it to a particle size within 5 cm, and then place it in a vibration sedimentation device for vibration sedimentation to remove aluminum impurities to obtain overhaul slag particles; wherein, the frequency of vibration sedimentation is 40 Hz and the amplitude is 8 mm;

[0041] (2) Mix the overhaul slag and activated carbon evenly according to a mass ratio of 1:0.05, and stack them evenly up and down to obtain a mixed material.

[0042] (3) Mix the mixed material with other raw materials evenly according to the ratio in Table 2, and grind them with a mill until the residue on a 80-micron sieve is less than 15% to obtain the sintering raw meal.

[0043] (4) Sinter the sintering raw meal at 1380 °C for 4 h, crush and cool it to obtain the harmless sintered material. This implementation mainly utilizes high-temperature calcination to make calcium, silicon, aluminum react with fluorine to generate calcium fluosilicate, thereby achieving the purpose of solidifying fluorine. The harmless sintered material is detected for the content of cyanide and leached fluorine in the sintered material according to GB5085.3-2007 "Identification Standard for Toxicity of Leaching of Hazardous Wastes", as shown in Table 2. The XRD pattern of the sintered material in this example is as Figure 2 shown.

[0044] Table 2

[0045]

[0046] 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 the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for high-temperature harmless treatment of overhaul slag, characterized in that, It includes the following steps: (1) Subject the overhaul slag to iron removal, crushing, and vibration sedimentation to obtain overhaul slag particles; (2) Mix the overhaul slag and the desiccant evenly and stack them evenly to obtain a mixture; (3) Mix the mixture, calcium-containing raw material, silicon-containing raw material, and aluminum-containing raw material evenly to obtain a sintering raw material; (4) Sinter, crush, and cool the sintering raw material to obtain a harmless sintered material.

2. The high-temperature harmless treatment method for overhaul slag according to claim 1, wherein The power of the vibration sedimentation is 30 - 50 Hz, and the amplitude is 6 - 10 mm.

3. The high-temperature harmless treatment method for overhaul slag according to claim 1, wherein The mass ratio of the overhaul slag to the desiccant is 1:(0.02 - 0.05).

4. The high-temperature harmless treatment method for overhaul slag according to claim 1, characterized in that The desiccant includes at least one of calcium oxide, silica gel, activated carbon, bentonite, and montmorillonite; The calcium-containing raw material includes at least one of limestone, dolomite, sepiolite, perlite, steel slag, desulfurized gypsum, fly ash, slag, paper sludge, and lime slag from the chlor-alkali industry; The silicon-containing raw material includes at least one of quartz, quartz sand, high-silica sandstone, opal, recycled glass, feldspar, kaolin, bentonite, nepheline, and pyrophyllite; The aluminum-containing raw material includes at least one of bauxite, gibbsite, diaspore, clay, feldspar, kaolin, bentonite, nepheline, pyrophyllite, red mud, electrolytic aluminum waste residue, aluminum ash, and aluminum slag; 5. The high-temperature harmless treatment method for overhaul slag according to claim 1, characterized in that, The mass percentage content of the main elemental components of the sintering raw material is: calcium oxide 5 - 75%, silicon dioxide 20 - 70%, aluminum oxide 8 - 35%, and iron oxide 5 - 20%.

6. The high-temperature harmless treatment method for overhaul slag according to claim 1, characterized in that, The sintering temperature is 800 - 1400 °C, and the sintering time is 2 - 6 h.

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