Method for treating zinc-containing fly ash from steel mills by chlorination smelting process

Abstract

The invention discloses a method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process, and belongs to the technical field of zinc-containing fly ash treatment. The method first pre-treats the zinc-containing fly ash, refines the particle size of the zinc-containing fly ash, increases the specific surface area of ​​the zinc-containing fly ash, and facilitates the reaction between zinc, lead and a chlorinating agent; secondly, the chlorinating agent used in the present invention includes a chlorinated hydrocarbon compound, and the chlorinating agent is loaded on a porous silicon carbide carrier, and the chlorinated hydrocarbon compound is gradually released during the chlorination treatment process, and can fully react with zinc and lead contained in the zinc-containing fly ash. The porous silicon carbide as a carrier can improve the overall strength and stability of the chlorinating agent, has good thermal conductivity, can effectively transfer reaction heat, improve the reaction selectivity of the chlorination treatment, and significantly improve the zinc removal rate of the zinc-containing fly ash treated by the chlorination method. And by loading on the porous silicon carbide carrier, the corrosion problem of the chlorinating agent on the equipment can be effectively avoided, and the application of the chlorination method in industry can be promoted.

Description

Technical Field

[0001] The invention belongs to the technical field of zinc-containing fly ash treatment, and in particular relates to a method for treating zinc-containing fly ash from a steel plant through a chlorination smelting process. Background Art

[0002] During the sintering, blast furnace and steelmaking processes, steel mills use a large amount of iron-zinc co-existing ores, zinc-containing sintered ores and galvanized scrap steel as raw materials, which will produce a large amount of zinc-containing ash. The zinc-containing ash is rich in alkali metals and will circulate and accumulate in the blast furnace production, which will not only corrode the inner wall of the blast furnace, but also seriously disrupt the normal movement of the charge, causing dangers such as hanging material and collapse, affecting the normal operation of the blast furnace. In addition, zinc is easily deposited in the gaps of the coke column skeleton, destroying the coke strength.

[0003] In order to solve the above problems, the zinc-containing ash produced needs to be treated. The common treatment methods are currently divided into wet process and pyrometallurgical process. The wet process mainly uses different leaching solutions for treatment, but the leaching rate of zinc and lead is low; the pyrometallurgical process mainly reduces the zinc in the ash into elemental zinc under high temperature conditions and then volatilizes and separates it. It is the most commonly used treatment method at present, but the pyrometallurgical process has a high treatment temperature and its energy loss is large.

[0004] Chlorination treatment of zinc-containing fly ash has been a new research focus in recent years. It mainly uses the characteristics of zinc and lead chlorides, which have high vapor pressure and are easy to volatilize at low temperatures, to volatilize and remove them from zinc-containing fly ash, while iron remains in the dust, achieving the purpose of metal element separation. Compared with the pyrometallurgical process, chlorination can greatly save energy and has a good development prospect. However, chlorination is seriously corrosive to equipment and is difficult to achieve industrial application. Summary of the invention

[0005] The object of the present invention is to provide a method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process, so as to solve the problem of serious equipment corrosion in the chlorination treatment and to improve the dezincification rate of the zinc-containing fly ash.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] The present invention provides a method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process, comprising the following process steps:

[0008] S1. Pretreatment of zinc-containing fly ash: collecting zinc-containing fly ash produced by steel mills, crushing, screening and drying to obtain pretreated zinc-containing fly ash;

[0009] S2. Chlorination treatment: The pretreated zinc-containing fly ash is mixed with a chlorinating agent and chlorinated at 900 to 1000°C for 2 to 4 hours to obtain chlorinated flue gas and slag;

[0010] S3. Condensation: After cooling and dust removal, the chlorinated flue gas is subjected to graded condensation to obtain zinc chloride and lead chloride, respectively. During the process, the tail gas is neutralized by a scrubber;

[0011] S4. Post-processing recovery: recovering metallic zinc from the condensed zinc chloride by electrolysis and / or chemical reduction;

[0012] The chlorinating agent comprises a chlorinated hydrocarbon compound; the chlorinating agent is supported on a porous silicon carbide carrier.

[0013] Preferably, the amount of the chlorinating agent added is 8-12% of the mass of the pretreated zinc-containing fly ash.

[0014] Preferably, the chlorinated hydrocarbon compound includes one or more combinations of carbon tetrachloride, ethylene monochloride, ethylene dichloride, ethylene trichloride, tetrachloroethylene, propylene chloride and butyl chloride.

[0015] Preferably, the particle size of the pretreated zinc-containing fly ash is 0.05 to 0.1 mm.

[0016] By adopting the above technical scheme, the present invention pre-treats the zinc-containing fly ash before chlorination treatment, refines the zinc-containing fly ash by crushing and screening, and controls the particle size of the zinc-containing fly ash within a certain range, thereby increasing the specific surface area of ​​the zinc-containing fly ash, exposing the zinc and lead contained in it on the surface, which is more conducive to the reaction between zinc and lead and the chlorinating agent during the chlorination treatment process, and helps to achieve metal separation.

[0017] The chlorinating agent used in the present invention includes chlorinated hydrocarbon compounds, and is loaded on a porous silicon carbide carrier. The chlorinated hydrocarbon compounds can significantly reduce the corrosion of the equipment compared to chlorine as the chlorinating agent, and after being loaded on the porous silicon carbide carrier, the direct contact between the chlorinating agent itself and the equipment can be reduced, thereby reducing the corrosion of the equipment. Under high temperature conditions, the chlorinating agent gradually decomposes, and the generated chlorine or hydrogen chloride can directly react with the mixed zinc-containing ash to generate zinc chloride and lead chloride, thereby achieving the purpose of metal separation. In addition, in this process, the chlorinating agent gradually decomposes and releases, and can fully react with the zinc and lead contained in the zinc-containing ash, significantly improving the dezincification rate of the zinc-containing ash treated by the chlorination method.

[0018] At the same time, the present invention selects porous silicon carbide as the carrier of the chlorinating agent. On the one hand, the porous silicon carbide has very good chemical stability and mechanical strength, excellent heat resistance, and can still maintain structural stability under the high temperature environment of chlorination treatment, thereby increasing the strength and wear resistance of the chlorinating agent. The porous structure also increases the specific surface area of ​​the carrier, providing more loadable space for the chlorinating agent, facilitating the circulation and storage of chlorine gas generated by decomposition, and improving the reaction activity with zinc and lead in zinc-containing ash;

[0019] On the other hand, porous silicon carbide also has good thermal conductivity, which can effectively transfer reaction heat. The chlorinated hydrocarbon compounds loaded on the surface of silicon carbide can gradually decompose under heat during the chlorination process, which helps to accurately release and react chlorine, improve the reaction selectivity of chlorination, thereby increasing the dezincification rate and effectively avoiding the corrosion of the chlorination agent to the equipment. Moreover, the carrier itself will not react with the decomposition products or zinc-containing soot, avoiding side reactions and the introduction of impurities, which is conducive to subsequent separation and post-processing.

[0020] Preferably, the raw materials of the chlorinating agent include porous silicon carbide and chlorinated hydrocarbon compounds in a molar ratio of 1:(2-4).

[0021] Preferably, the chlorinating agent is prepared according to the following method:

[0022] Preparation of porous silicon carbide: adding silicon carbide powder, sintering aid and molding aid to a solvent, mixing well, ball milling, drying and grinding, and then raising the temperature to 1300-1400°C in a nitrogen atmosphere and keeping the temperature for 2-3 hours to obtain porous silicon carbide;

[0023] Preparation of chlorinating agent: Place porous silicon carbide in a reactor, raise the temperature to 60-80°C, introduce a mixed gas of nitrogen and chlorinated hydrocarbon compound vapor, and react for 3-5 hours to obtain the chlorinating agent.

[0024] Preferably, the added amount of the sintering aid is 12-15% of the mass of the silicon carbide powder; and the added amount of the molding aid is 8-13% of the mass of the silicon carbide powder.

[0025] Preferably, the particle size of the silicon carbide powder is 5 to 20 μm.

[0026] Preferably, the sintering aid includes a combination of one or more of alumina, yttria, silica, cerium oxide and polyvinyl alcohol.

[0027] Preferably, the molding aid includes a combination of one or more of graphene, starch, carbon black and cellulose.

[0028] Preferably, the solvent includes a combination of one or more of ethanol, methanol, isopropanol, n-butanol and ethylene glycol.

[0029] By adopting the above technical solution, silicon carbide micropowder forms a porous structure with the help of sintering aids and molding aids, which increases the specific surface area of ​​silicon carbide, and the internal cavities increase the storage and flow space of the gas, thereby improving the reactivity of the chlorinating agent. Further, with nitrogen as a carrier gas, porous silicon carbide is placed in a vapor environment of chlorinated hydrocarbon compounds, and the chlorinated hydrocarbon compounds are deposited on the surface of silicon carbide. Since the chlorinated hydrocarbon compounds exist in the form of gas during the reaction, the chlorinated hydrocarbon compounds are deposited more evenly on the surface of porous silicon carbide. The chlorinating agent formed can improve the reaction selectivity in the chlorination treatment, increase the zinc removal rate of zinc-containing soot, and effectively avoid the corrosion of the chlorinating agent to the equipment, thereby being able to efficiently and safely achieve metal separation and recycling of zinc-containing soot.

[0030] Preferably, the porous silicon carbide is compounded with a metal oxide; the metal oxide includes one or a combination of iron oxide and aluminum oxide.

[0031] Preferably, the content of the composite metal oxide is 5-8%.

[0032] Preferably, the porous silicon carbide composite metal oxide is prepared according to the following method: adding a soluble metal salt to water, stirring and dissolving to obtain an impregnation solution; dispersing the porous silicon carbide in the impregnation solution, wetting and standing for 12 to 15 hours, and then drying and calcining to obtain the porous silicon carbide composite metal oxide.

[0033] Preferably, the soluble metal salt includes one or more combinations of ferric nitrate, ferric sulfate, ferric chloride, ferrous chloride, aluminum chloride, aluminum sulfate, aluminum nitrate and aluminum acetate.

[0034] By adopting the above technical scheme, the chlorinating agent of the present invention is deposited on the porous silicon carbide carrier, and then in the chlorination process, chlorine or hydrogen chloride gas is generated by thermal decomposition to participate in the chlorination reaction to achieve the separation of zinc and lead. However, in the thermal decomposition process, the reaction progress is slow, which will extend the process cycle, so the porous silicon carbide carrier is post-treated and composited with metal oxides. The composite of metal oxides can catalyze the thermal decomposition reaction of chlorinated hydrocarbon compounds, increase the reaction rate of thermal decomposition, and promote the full decomposition of chlorinated hydrocarbon compounds, thereby enhancing the chlorination reaction between the chlorinating agent and zinc-containing ash.

[0035] On the other hand, the composite of metal oxides also increases the active sites on the surface of porous silicon carbide. Since porous silicon carbide is a non-polar compound with an inert surface and almost no polar groups, the chlorinated hydrocarbon compounds deposited on the surface of porous silicon carbide have weak bonding force and will fall off and be lost during use, which will not only affect the zinc removal rate of chlorination treatment but also aggravate the corrosion of the chlorinating agent to the equipment. In the process of composite metal oxides, wetting and sintering can promote the diffusion and reaction between the metal oxide and porous silicon carbide, thereby improving the bonding force between the two, and then improving the active centers on the surface of porous silicon carbide. In the process of deposition of chlorinated hydrocarbon compounds, the bonding force between the porous silicon carbide and the porous silicon carbide can be improved, which does not affect the thermal decomposition and can also improve the structural stability of the chlorinating agent.

[0036] Beneficial effects of the present invention:

[0037] 1. In the method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process of the present invention, the collected zinc-containing fly ash is first pretreated to refine the particle size of the zinc-containing fly ash and increase the specific surface area to promote the chlorination treatment reaction; and the chlorinating agent used in the chlorination treatment includes a chlorinated hydrocarbon compound and is also loaded on a porous silicon carbide carrier, thereby avoiding direct contact between the chloride itself and the equipment and greatly reducing corrosion to the equipment. The porous silicon carbide as a carrier is conducive to improving the structural stability and strength of the chlorinating agent, can adapt to the high temperature environment of the chlorination treatment, and increase the reaction activity of the chlorinating agent, thereby improving the zinc removal rate of the zinc-containing fly ash, and can efficiently and safely achieve metal separation and recycling of the zinc-containing fly ash.

[0038] 2. The chlorinating agent carrier of the present invention is also treated with a metal oxide composite. In addition to being able to catalyze the thermal decomposition reaction of chlorinated hydrocarbon compounds and improve the reaction activity, it can also increase the surface active sites of porous silicon carbide, thereby improving the bonding force between the chlorinated hydrocarbon compounds and the porous silicon carbide during the deposition process, and can also improve the structural stability of the chlorinating agent without affecting the thermal decomposition. DETAILED DESCRIPTION

[0039] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] Preparation example:

[0041] Preparation Example 1, a chlorinating agent, prepared according to the following method:

[0042] 20 g of silicon carbide powder (average particle size of 15 μm), 2.8 g of sintering aid (a mixture of aluminum oxide and yttrium oxide in a mass ratio of 2:1) and 2 g of graphene were added to 25 mL of ethanol, mixed evenly, ball milled, dried and ground, and then the temperature was raised to 1350 ° C in a nitrogen atmosphere and kept for 2 h to obtain porous silicon carbide;

[0043] The porous silicon carbide obtained above was placed in a reactor, the temperature was raised to 70° C., a mixed gas of nitrogen and carbon tetrachloride vapor was introduced, wherein the molar ratio of porous silicon carbide to carbon tetrachloride was 1:3, and the chlorinating agent was obtained after reacting for 4 hours.

[0044] Preparation Example 2, a chlorinating agent, is different from Preparation Example 1 only in that the added amount of sintering aid is 2.4 g, the added amount of graphene is 1.6 g; and the molar ratio of porous silicon carbide to carbon tetrachloride is 1:2.

[0045] Preparation Example 3, a chlorinating agent, is different from Preparation Example 1 only in that the added amount of sintering aid is 3 g, the added amount of graphene is 2.6 g; and the molar ratio of porous silicon carbide to carbon tetrachloride is 1:4.

[0046] Preparation Example 4, a chlorinating agent, is different from Preparation Example 1 only in that the molar ratio of porous silicon carbide to carbon tetrachloride is 1:1.

[0047] Preparation Example 5, a chlorinating agent, is different from Preparation Example 1 only in that the molar ratio of porous silicon carbide to carbon tetrachloride is 1:5.

[0048] Preparation Example 6, a chlorinating agent is prepared according to the following method: silicon carbide micropowder (average particle size of 15 μm) is placed in a reactor, the temperature is raised to 70°C, a mixed gas of nitrogen and carbon tetrachloride vapor is introduced, wherein the molar ratio of silicon carbide micropowder to carbon tetrachloride is 1:3, and the chlorinating agent is obtained after reacting for 4 hours.

[0049] Preparation Example 7, a chlorinating agent, prepared according to the following method:

[0050] 20 g of silicon carbide powder (average particle size of 15 μm), 2.8 g of sintering aid (a mixture of aluminum oxide and yttrium oxide in a mass ratio of 2:1) and 2 g of graphene were added to 25 mL of ethanol, mixed evenly, ball milled, dried and ground, and then the temperature was raised to 1350 ° C in a nitrogen atmosphere and kept for 2 h to obtain porous silicon carbide;

[0051] Add ferric nitrate to water, stir and dissolve to obtain an impregnation solution with a mass fraction of 10%; take 20g of the porous silicon carbide obtained above and disperse it in the impregnation solution, wet and stand for 12 hours, and then dry and calcine to obtain a porous silicon carbide composite metal oxide, wherein the content of the metal oxide is 6%;

[0052] The porous silicon carbide composited with metal oxides obtained above was placed in a reactor, the temperature was raised to 70° C., a mixed gas of nitrogen and carbon tetrachloride vapor was introduced, wherein the molar ratio of porous silicon carbide to carbon tetrachloride was 1:3, and the chlorinating agent was obtained after reacting for 4 hours.

[0053] Preparation Example 8, a chlorinating agent, differs from Preparation Example 7 only in that an equal amount of aluminum nitrate is used to replace iron nitrate.

[0054] Preparation Example 9, a chlorinating agent, differs from Preparation Example 7 only in that the content of the metal oxide is 5%.

[0055] Preparation Example 10, a chlorinating agent, differs from Preparation Example 7 only in that the content of the metal oxide is 8%.

[0056] Preparation Example 11, a chlorinating agent, differs from Preparation Example 7 only in that the content of the metal oxide is 3%.

[0057] Preparation Example 12, a chlorinating agent, differs from Preparation Example 7 only in that the content of the metal oxide is 10%.

[0058] Example:

[0059] Example 1, a method for treating zinc-containing fly ash from a steel plant by a chloride smelting process, comprising the following process steps:

[0060] S1. Pretreatment of zinc-containing fly ash: collecting zinc-containing fly ash produced by steel mills, crushing, screening and drying to obtain pretreated zinc-containing fly ash, and controlling the average particle size of the pretreated zinc-containing fly ash to be 0.07 mm;

[0061] S2. Chlorination treatment: The pretreated zinc-containing fly ash was uniformly mixed with the chlorinating agent prepared in Preparation Example 1, wherein the amount of the chlorinating agent added was 10% of the mass of the pretreated zinc-containing fly ash; chlorination was performed at 950°C for 3h to obtain chlorinated flue gas and slag;

[0062] S3. Condensation: After cooling and dust removal, the chlorinated flue gas is subjected to graded condensation to obtain zinc chloride and lead chloride, respectively. During the process, the tail gas is neutralized by a scrubber;

[0063] S4. Post-processing recovery: The zinc chloride obtained by condensation is electrolyzed to recover metallic zinc.

[0064] Example 2, a method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process, is different from Example 1 only in that the amount of chlorinating agent added is 8% of the mass of the pre-treated zinc-containing fly ash.

[0065] Example 3, a method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process, is different from Example 1 only in that the amount of chlorinating agent added is 12% of the mass of the pre-treated zinc-containing fly ash.

[0066] Example 4, a method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process, is different from Example 1 only in that the chlorinating agent prepared in Preparation Example 1 is replaced by an equal amount of the chlorinating agent prepared in Preparation Example 2.

[0067] Example 5, a method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process, is different from Example 1 only in that the chlorinating agent prepared in Preparation Example 1 is replaced by an equal amount of the chlorinating agent prepared in Preparation Example 3.

[0068] Example 6, a method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process, is different from Example 1 only in that the chlorinating agent prepared in Preparation Example 1 is replaced by an equal amount of the chlorinating agent prepared in Preparation Example 4.

[0069] Example 7, a method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process, is different from Example 1 only in that the chlorinating agent prepared in Preparation Example 1 is replaced by an equal amount of the chlorinating agent prepared in Preparation Example 5.

[0070] Example 8, a method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process, is different from Example 1 only in that the chlorinating agent prepared in Preparation Example 1 is replaced by an equal amount of the chlorinating agent prepared in Preparation Example 7.

[0071] Example 9, a method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process, is different from Example 1 only in that the chlorinating agent prepared in Preparation Example 1 is replaced by an equal amount of the chlorinating agent prepared in Preparation Example 8.

[0072] Example 10, a method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process, is different from Example 1 only in that the chlorinating agent prepared in Preparation Example 1 is replaced by an equal amount of the chlorinating agent prepared in Preparation Example 9.

[0073] Example 11, a method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process, is different from Example 1 only in that the chlorinating agent prepared in Preparation Example 1 is replaced by an equal amount of the chlorinating agent prepared in Preparation Example 10.

[0074] Example 12, a method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process, is different from Example 1 only in that the chlorinating agent prepared in Preparation Example 1 is replaced by an equal amount of the chlorinating agent prepared in Preparation Example 11.

[0075] Example 13, a method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process, is different from Example 1 only in that the chlorinating agent prepared in Preparation Example 1 is replaced by an equal amount of the chlorinating agent prepared in Preparation Example 12.

[0076] Example 14, a method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process, is different from Example 1 only in that the amount of chlorinating agent added is 5% of the mass of the pre-treated zinc-containing fly ash.

[0077] Example 15, a method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process, differs from Example 1 only in that the amount of chlorinating agent added is 15% of the mass of the pre-treated zinc-containing fly ash.

[0078] Comparative Example:

[0079] Comparative Example 1, a method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process, differs from Example 1 only in that the chlorinating agent prepared in Preparation Example 1 is replaced by an equal amount of the chlorinating agent prepared in Preparation Example 6.

[0080] Comparative Example 2, a method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process, differs from Example 1 only in that an equal amount of carbon tetrachloride is used to replace the chlorinating agent prepared in Preparation Example 1.

[0081] Comparative Example 3, a method for treating zinc-containing fly ash from a steel plant by a chloride smelting process, differs from Example 1 only in that, in step S1, the zinc-containing fly ash produced by the steel plant is collected without being crushed or screened, and the pretreated zinc-containing fly ash is obtained after drying.

[0082] Comparative Example 4, a method for treating zinc-containing fly ash from a steel plant by a chlorination smelting process, differs from Example 1 only in that, in step S2, the chlorinating agent prepared in Preparation Example 1 is not added, and the pretreated zinc-containing fly ash is placed in a chlorine atmosphere and chlorinated at 950°C for 3 hours.

[0083] Performance testing:

[0084] The zinc-containing fly ash was treated by the chlorination method in the above embodiment and comparative example, and the zinc recovery rate and lead recovery rate of the zinc-containing fly ash after chlorination treatment were tested and calculated. The details are shown in Table 1.

[0085] .

[0086] Combining Example 1 and Example 2 to Example 5, it can be seen that there is no significant difference in the recovery rate of zinc and lead in Example 2 to Example 5 compared with Example 1. The reason is that the difference between Example 2 to Example 5 and Example 1 is only that the addition amount of the chlorinating agent and the content of the chlorinated hydrocarbon compound in the chlorinating agent are adjusted within the required range, which has little effect on the dezincification rate of the final zinc-containing fly ash and can effectively avoid the corrosion problem of equipment in the chlorination treatment.

[0087] Combining Example 1, Example 6 and Example 7, it can be seen that the recovery rate of zinc and lead in Example 6 is lower than that in Example 1. The reason is that the content of chlorinated hydrocarbon compounds in the chlorinating agent is reduced in Example 6, resulting in a decrease in the content of chlorine or hydrogen chloride gas by thermal decomposition, and a decrease in the content of zinc chloride and lead chloride formed by combining with zinc and lead, thereby affecting the zinc removal rate of zinc-containing ash. Compared with Example 1, Example 7 has a smaller change. In Example 7, the content of chlorinated hydrocarbon compounds in the chlorinating agent is increased. In the chlorination process, there is enough chlorinating agent to participate in the reaction, but excessive chlorinating agent will cause equipment corrosion, which will affect the reaction process of the chlorination treatment.

[0088] In combination with Example 1 and Example 8 to Example 13, it can be seen that the recovery rate of zinc and lead in Example 8 is increased compared with that in Example 1. The reason is that the porous silicon carbide carrier in Example 8 is compounded with metal oxides, which, on the one hand, improves the thermal decomposition efficiency of chlorinated hydrocarbon compounds and increases the reaction activity of the chlorinating agent, thereby increasing the zinc removal rate of zinc-containing ash. On the other hand, it increases the binding force between the chlorinated hydrocarbon compounds and the carrier, reduces the loss and increases the protection of the equipment; the recovery rate of Example 9 to Example 11 does not change much compared with Example 8, because, compared with Example 8, Examples 9 to Example 11 only change the type and content of metal oxides within the required range, which has little effect on the activity of the chlorinating agent; the recovery rates of zinc and lead in Examples 12 and 13 are reduced compared with Example 8, because the content of metal oxides in Example 12 is reduced, and the active sites on the surface of porous silicon carbide are reduced accordingly, which affects the activity and stability of the chlorinating agent, resulting in a decrease in the zinc removal rate of zinc-containing ash. In Example 13, the content of metal oxide is increased. Excessive metal oxide will block some pores of porous silicon carbide, thereby affecting the release of thermal decomposition products and affecting the chlorination treatment process.

[0089] Combining Example 1, Example 14 and Example 15, it can be seen that the recovery rate of zinc and lead in Example 14 is lower than that in Example 1. The reason is that the amount of chlorinating agent added is reduced in Example 14, which will cause the zinc and lead in the zinc-containing fly ash to fail to fully react, forming chloride vapor separation, and ultimately leading to a decrease in the dezincification rate of the zinc-containing fly ash; the amount of chlorinating agent added is increased in Example 15, and the recovery rate does not change significantly compared with Example 1, but excessive addition of chlorinating agent will produce excessive thermal decomposition products, thereby increasing the problem of equipment corrosion.

[0090] Combining Example 1 and Comparative Examples 1 to 4, it can be seen that the recovery rates of zinc and lead in Comparative Examples 1 to 4 are significantly lower than those in Example 1. The reason is that in Comparative Example 1, non-porous silicon carbide is used as a carrier. In addition to the greatly reduced load, the reaction activity of the thermal decomposition process of chlorinated hydrocarbon compounds and the number of thermal decomposition products are reduced, thereby affecting the chlorination reaction; the chlorinated hydrocarbon compounds in Comparative Example 2 are not loaded on porous silicon carbide, and direct decomposition during the chlorination treatment process is likely to cause incomplete reaction of zinc and lead in zinc-containing ash, and dezincification. The rate is reduced, and the chlorinating agent is in direct contact with the equipment, which will increase the corrosion of the equipment; in Comparative Example 3, the zinc-containing fly ash is not pretreated before the chlorination treatment, the zinc-containing fly ash particle sizes are different, and the particles are agglomerated together, which is not conducive to the chlorination reaction process and will affect the chlorination reaction of the chlorinating agent on zinc and lead; in Comparative Example 4, conventional chlorinating agent chlorine is used for chlorination treatment, which cannot act evenly on the zinc-containing fly ash, and the chlorination reaction is incomplete, resulting in a decrease in the dezincification rate compared with Example 1. More importantly, the use of chlorine as a chlorinating agent causes serious corrosion to the equipment and is not suitable for long-term industrial production.

[0091] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0092] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for treating zinc-containing fly ash from a steel plant by a chloride smelting process, characterized in that: The process steps include: S1. Pretreatment of zinc-containing fly ash: collecting zinc-containing fly ash produced by steel mills, crushing, screening and drying to obtain pretreated zinc-containing fly ash; S2. Chlorination treatment: The pretreated zinc-containing fly ash is mixed with a chlorinating agent and chlorinated at 900 to 1000°C for 2 to 4 hours to obtain chlorinated flue gas and slag; S3. Condensation: After cooling and dust removal, the chlorinated flue gas is subjected to graded condensation to obtain zinc chloride and lead chloride, respectively. During the process, the tail gas is neutralized by a scrubber; S4. Post-processing recovery: recovering metallic zinc by electrolysis or chemical reduction of the condensed zinc chloride; The chlorinating agent comprises a chlorinated hydrocarbon compound; the chlorinated hydrocarbon compound comprises a combination of one or more of carbon tetrachloride, ethylene monochloride, ethylene dichloride, ethylene trichloride, tetrachloroethylene, chloropropane and chlorobutane; the chlorinating agent is supported on a porous silicon carbide carrier; The raw materials of the chlorinating agent include porous silicon carbide and chlorinated hydrocarbon compounds in a molar ratio of 1:(2-4); The chlorinating agent is prepared according to the following method: Preparation of porous silicon carbide: adding silicon carbide powder, sintering aid and molding aid to a solvent, mixing well, ball milling, drying and grinding, and then raising the temperature to 1300-1400°C in a nitrogen atmosphere and keeping the temperature for 2-3 hours to obtain porous silicon carbide; Preparation of chlorinating agent: Place porous silicon carbide in a reactor, raise the temperature to 60-80°C, introduce a mixed gas of nitrogen and chlorinated hydrocarbon compound vapor, and react for 3-5 hours to obtain the chlorinating agent.

2. The method for treating zinc-containing fly ash from a steel plant by a chloride smelting process according to claim 1, characterized in that: The added amount of the chlorinating agent is 8-12% of the mass of the pre-treated zinc-containing fly ash.

3. The method for treating zinc-containing fly ash from a steel plant by a chlorination process smelting process according to claim 1, characterized in that: The added amount of the sintering aid is 12-15% of the mass of the silicon carbide micropowder; the added amount of the molding aid is 8-13% of the mass of the silicon carbide micropowder.

4. The method for treating zinc-containing fly ash from a steel plant by a chlorination process smelting process according to claim 1, characterized in that: The porous silicon carbide is compounded with metal oxides; the metal oxides include one or a combination of iron oxide and aluminum oxide.

5. The method for treating zinc-containing fly ash from a steel plant by a chlorination process according to claim 4, characterized in that: The content of the composite metal oxide is 5-8%.

6. The method for treating zinc-containing fly ash from a steel plant by a chlorination process according to claim 4, characterized in that: The porous silicon carbide composite metal oxide is prepared according to the following method: adding a soluble metal salt into water, stirring and dissolving it to obtain an impregnation solution; dispersing the porous silicon carbide in the impregnation solution, wetting and standing it for 12 to 15 hours, and then drying and calcining to obtain the porous silicon carbide composite metal oxide.

7. The method for treating zinc-containing fly ash from a steel plant by a chloride smelting process according to claim 1, characterized in that: The particle size of the pretreated zinc-containing fly ash is 0.05-0.1 mm.