Method for synergistically harmlessly treating waste incineration fly ash and steelmaking furnace dust and preparing sintering-grade calcium ferrite

Abstract

The invention relates to the technical field of hazardous waste harmless treatment and comprehensive utilization of resources, in particular to a method for synergistic harmlessness of waste incineration fly ash and steel-making furnace dust and preparation of sintered-grade calcium ferrite, which comprises the following steps: S100: carrying out raw material compatibility according to mineral phase composition of waste incineration fly ash and steel-making furnace dust to obtain a uniform mixture; s200, the obtained mixture is supplemented with inert gas flow, and the mixture is fed into a high-temperature area to be roasted; s300, after calcification-chlorination composite activation high-temperature roasting, activated zinc-lead-potassium-sodium-rich phase and stable-phase dicalcium ferrite are generated; s400, the activated phase sublimates to a low-temperature area along with inert gas flow to be desublimated and separated from tailings, and purification is achieved; according to the method, the waste incineration fly ash and the steelmaking furnace dust are subjected to synergistic harmlessness, and meanwhile, the alkaline oxide and the iron-containing oxide are combined and can serve as an iron-containing raw material and an alkaline flux in the sintering process. According to the method, the hazardous waste can be synergistically self-treated and converted into an iron-making process raw material-level resource, the environmental protection benefit is outstanding, and certain economic benefits are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of harmless disposal of hazardous waste and comprehensive utilization of resources, and specifically to a method for synergistically harmlessly treating waste incineration fly ash and steelmaking furnace dust and preparing sintering-grade calcium ferrite. Background Art

[0002] As we all know, steelmaking dust contains over 60% iron compounds. However, due to the presence of harmful elements like Zn and Pb, which can easily cause blast furnace nodules, it cannot be used in the ironmaking process, resulting in a significant waste of resources. Furthermore, due to the presence of heavy metal Zn, electric furnace dust is classified as a hazardous solid waste, requiring urgent disposal.

[0003] Waste incineration fly ash, whose production has continued to increase in recent years, also belongs to hazardous solid waste. With the development of industrialization and urbanization, the amount of urban garbage collected and transported has been increasing year by year, and its main treatment methods are landfill and incineration. In recent years, due to the use of waste incineration to generate electricity, the method of incineration to treat urban garbage has increased to more than 80% of the total amount. This has led to the further generation of large amounts of waste incineration fly ash, and the various heavy metals (such as lead, cadmium, and zinc) and dioxins, known as the "poison of the century", contained in it will cause great harm to the environment if not handled properly, and safe disposal is imminent. At the same time, a large amount of calcium oxide in the waste incineration fly ash is not utilized when it is landfilled, resulting in a waste of resources. A method suitable for properly treating steelmaking dust and waste incineration fly ash urgently needs to be discovered.

[0004] Currently, the main methods for treating zinc-containing steelmaking dust are carbon thermal reduction in pyrometallurgy and strong acid leaching in hydrometallurgy. The carbon thermal reduction method mainly adopts the method of adding a reducing agent carbon to reduce zinc oxide or zinc ferrite, so that the reduced product zinc volatilizes under high temperature conditions, thereby achieving the purpose of separation. Although this method is simple and efficient, it will produce greenhouse gas CO2, which is not conducive to environmental sustainability. For the strong acid leaching method, it adds an acidic solution to leach the target element, followed by neutralization, replacement and electrolytic deposition. Although this method reduces carbon emissions, it cannot efficiently separate zinc and iron, the process is lengthy, and the zinc recovery rate is low. In these methods, the iron element is not effectively recycled.

[0005] Patent CN202411467106.2 discloses a method for preparing composite calcium ferrite, the main steps of which are A1) mixing and grinding pretreated industrial green vitriol and pretreated titanium gypsum to obtain a mixture H1; A2) mixing the mixture H1 with water, pressing it into a block, and drying it to obtain a block mixture K1; A3) calcining the block mixture K1 to obtain composite calcium ferrite; or B1) drying industrial green vitriol and mixing it with pretreated titanium gypsum to obtain a mixture H2; B2) mixing the mixture H2 with water, pressing it into a block, and drying it to obtain a block mixture K2; B3) calcining the block mixture K2 to obtain composite calcium ferrite. Patent CN202410736217.2 discloses a method for preparing composite calcium ferrite from industrial green vitriol. The main steps are: S1) drying the industrial green vitriol, mixing it with a calcium source, Al2O3, and SiO2, and ball milling it to obtain a mixture; S2) forming the mixture into blocks, drying it, calcining the resulting blocks, and cooling them to obtain composite calcium ferrite; or S2') calcining the mixture and cooling it to obtain composite calcium ferrite. This method utilizes one or two solid wastes, mixing and roasting them to transform the mineral phase into the binder phase composite calcium ferrite required for the sintering process. This allows for the effective reuse of industrial solid waste and reduces sintering energy consumption. However, the roasting process of green vitriol and gypsum produces sulfur dioxide, an industrial byproduct that can be hazardous if improperly handled. Furthermore, current methods, due to limitations in the raw materials used, result in suboptimal impurity levels in the resulting composite calcium ferrite. Therefore, a method is urgently needed to harmlessly treat multiple hazardous wastes and produce composite calcium ferrite suitable for blast furnace sintering, effectively utilizing all elements.

[0006] Waste incineration fly ash contains significant amounts of calcium- and chlorine-containing mineral phases, reminiscent of the calcification and chlorination reactions in metallurgical processes. Leveraging the complementary nature of these two hazardous solid waste resources, comprehensive hazardous waste disposal can achieve the goal of low-cost, comprehensive element utilization. Specifically, by modifying zinc-iron compounds with the primary elements Ca and Cl in waste incineration fly ash, a calcification-chlorination complex activates a dense zinc ferrite structure, allowing blast furnace-harmful elements like K, Na, Pb, and Zn to separate into a volatile phase. This yields harmless composite calcium ferrite, which can be fed back into the blast furnace ironmaking process as alkaline iron-containing charge.

[0007] To address the difficulty of efficiently recycling these two hazardous wastes, we are now integrating waste incineration fly ash with zinc-containing steelmaking dust. This method uses a composite calcification-chlorination activation process to treat the inert zinc ferrite in the steelmaking dust, converting it into a composite calcium ferrite. This method meets the current needs of blast furnace production and can be returned to the ironmaking process, while also rendering the waste incineration fly ash harmless. This method synergistically treats the two hazardous wastes, achieving both harmless treatment and resource reuse. Summary of the Invention

[0008] To address the above-mentioned issues, the present invention provides a method for the synergistic detoxification of waste incineration fly ash and steelmaking dust to produce sintering-grade calcium ferrite. This method addresses the difficulty in recycling iron in zinc-containing steelmaking dust due to harmful elements such as Zn, Pb, K, and Na, as well as the increasing difficulty in treating waste incineration fly ash. Drawing on existing calcification and chlorination treatment methods in pyrometallurgy, the method proposes a one-step synergistic composite calcification-chlorination method utilizing calcium and chlorine in waste incineration fly ash to activate the inert zinc ferrite in zinc-containing steelmaking dust, converting it into alkaline iron-containing charge material for reintroduction into the ironmaking process.

[0009] A method for synergistically detoxifying waste incineration fly ash and steelmaking furnace dust to prepare sintering-grade calcium ferrite comprises the following steps:

[0010] S100: Raw materials are mixed according to the composition of waste incineration fly ash and steelmaking furnace dust to obtain a uniform mixture.

[0011] S200: The obtained mixture is fed into a high temperature zone for roasting with the aid of an inert gas flow;

[0012] S300: After calcification-chlorination composite activation and high-temperature roasting, an activated zinc-lead-potassium-sodium phase and a stable phase of dicalcium ferrite are produced. The stable phase of dicalcium ferrite is suitable for use as an alkaline flux and iron-containing charge in the sintering process.

[0013] S400: The activated phase sublimates and moves along with the inert gas flow to the low temperature zone to condense and separate from the tailings for purification.

[0014] The method provided by the present invention first mixes waste incineration fly ash with steelmaking dust (including converter ash and electric arc furnace ash) and granulates them. The waste incineration fly ash serves as a calcium source (providing CaO) and a chlorine source (providing Cl). Through a composite calcification-chlorination reaction, the lattice structure of inert zinc ferrite (ZnFe2O4) is destroyed, releasing Fe and combining with Ca to form dicalcium ferrite (Ca2Fe2O5). Simultaneously, harmful elements such as Zn, Pb, K, and Na react with Cl to form low-boiling-point chlorides (such as ZnCl2, with a boiling point of approximately 732°C), which are volatilized and separated. This process achieves the synergistic harmlessness of the two hazardous wastes, with a total volatilization rate of harmful elements of ≥98%. At the same time, the iron element is efficiently converted into an alkaline iron-containing charge that can be directly used for sintering, reducing the amount of alkaline flux added and energy consumption in traditional sintering processes, achieving both environmental and economic benefits.

[0015] Preferably, step S100 is specifically as follows: (1) mixing waste incineration fly ash and steelmaking furnace dust in a ratio of 1-4:1 to obtain a mixture; (2) granulating the mixture into particles with a radius of about 100 μm.

[0016] Preferably, the steelmaking dust in step (1) is a dust material obtained by mixing converter ash and electric arc furnace ash in a certain proportion.

[0017] Preferably, the granulation in step (2) can be carried out using a disc granulator, with water added as a binder;

[0018] Specifically, deionized water was added as a binder in a mass ratio of mixture to deionized water = 10:1.

[0019] Preferably, the particle diameter of the particles in step (2) should be less than 200 μm and the proportion of particles with a particle size in the range of 50-150 μm should be greater than 80%. Since the reaction is a solid-solid reaction, in order to improve its reaction efficiency, it is necessary to granulate it in advance. By controlling the particle size distribution, the solid-solid reaction contact area can be increased, the mass transfer efficiency can be improved, and the solid-solid reaction kinetics limitation can be alleviated.

[0020] Preferably, the granulator described in step (2) can be a disc granulator. When the disc diameter is 80 cm, the disc inclination angle is preferably 45-60°, and the rotation speed is preferably 10-30 r / min.

[0021] Preferably, step S200 is specifically as follows: (3) before the mixture is sent into the high temperature zone, the temperature of the high temperature zone needs to be controlled to 1000-1020°C; (4) under an inert atmosphere, after high temperature roasting, the zinc ferrite structure will be converted into dicalcium ferrite, wherein the blast furnace harmful elements will be converted into ZnCl2, PbCl2, KCl, and NaCl volatile phases.

[0022] Preferably, in step (3), a gradient temperature field is set in the roasting equipment, and the temperature from the material inlet to the outlet gradually increases from 1000-1020°C to 1260°C, with a gradient interval of 20°C, and an ultrasonic oscillation device is set in the high temperature zone, with an ultrasonic frequency of 20-40kHz and a power density of 0.8-1.5W / cm 2At the same time, a microwave radiation device is set in the high-temperature zone, the microwave frequency is 2450MHz, the power is between 10-15kW, and a rotatable material dispersion blade is installed in the roasting equipment, and the blade speed is 20-30r / min; under an inert atmosphere, the zinc ferrite structure is converted into dicalcium ferrite, and at the same time, harmful elements such as Zn, Pb, K, and Na are converted into volatile phases of ZnCl2, PbCl2, KCl, and NaCl. Among them, the role of setting a gradient temperature field is to enable the material to gradually complete the reaction at different temperature stages, more fully promote the conversion of zinc ferrite to dicalcium ferrite and the volatilization of harmful elements, and solve the problems of insufficient reaction and limited conversion rate in traditional single-temperature roasting; the ultrasonic oscillation device can destroy the material agglomeration structure through high-frequency vibration, increase the contact area between the material and the gas, accelerate the reaction rate and mass transfer process, and solve the problems of low reaction efficiency and incomplete volatilization of harmful elements caused by agglomeration of the material during the roasting process; among them, the microwave radiation device can utilize the selective heating characteristics of microwaves to make the polar molecules in the material vibrate rapidly to generate heat, accelerate the internal reaction process of the material, improve the conversion efficiency of zinc ferrite to dicalcium ferrite and the volatilization rate of harmful elements, and solve the problems of slow heat transfer and insufficient reaction in traditional heating methods; the rotatable material dispersion blades can continuously change the distribution state of the material in the roasting equipment, avoid material accumulation, further increase the contact area between the material and the inert airflow and high-temperature environment, promote uniform reaction, and solve the problems of uneven heating and inconsistent reaction of the material during the roasting process.

[0023] Preferably, the inert atmosphere in step (4) can effectively inhibit the dense phase produced by the waste incineration fly ash under high temperature roasting by promoting the decomposition of CaSO4: 10 The formation of (SiO4)3(SO4)3Cl2 effectively promotes the forward progress of the reaction and the volatilization of harmful elements.

[0024] Preferably, step S300 is specifically as follows: (5) the main component of the pyrometallurgical separation tailings is dicalcium ferrite, and a high alkalinity atmosphere needs to be created in the sintering process to produce calcium ferrite. Therefore, adding this tailings to the sintering process can replace part of the flux and iron-containing raw material usage in the sintering process, such as iron concentrate, thereby reducing the flux consumption and energy consumption of the sintering process.

[0025] Preferably, step S400 is specifically as follows: (6) utilizing the carrying effect of the inert gas flow to carry the volatile phase away from the high temperature zone to achieve separation from the tailings; (7) the volatile phase carried away can be condensed and collected in the low temperature zone; (8) the obtained tailings contain alkaline oxides and iron oxide, which is a raw material for blast furnace ironmaking, and can be used as a high-quality alkaline ironmaking raw material for blast furnaces; (9) various elements in the volatile phase can be further separated and processed in order to be used as chemical raw materials.

[0026] Preferably, the low-temperature desublimation collection method in step (7) can use a programmed cooling device to centrally collect the collected substances for subsequent processing.

[0027] Preferably, the tailings obtained in step (8) contain a large amount of CaO which can meet the requirements of making alkaline slag in blast furnaces, and the generated dicalcium ferrite can be used as an alkaline iron-containing sintering raw material.

[0028] Preferably, the method for further separating the volatile phase in step (9) utilizes the different precipitation degrees of K, Na, Pb, and Zn in the volatile phase under different alkaline conditions to achieve the purpose of separation.

[0029] The method provided by the present invention for calcification-chlorination composite activation of inert zinc ferrite in steelmaking dust to produce sintering-grade calcium ferrite has the following beneficial effects:

[0030] (1) Collaborative treatment of hazardous waste and resource conversion

[0031] The present invention is based on an in-depth analysis of the mineral composition of steelmaking dust (including converter ash and electric arc furnace ash) and waste incineration fly ash, accurately matching the mineral content of the two, and utilizing the synergistic effect of calcium and chlorine elements in fly ash and iron and zinc elements in dust to mix the two types of hazardous wastes in proportion to achieve synergistic composite harmless treatment. Through the optimization of solid-solid reaction granulation and the design of high-temperature roasting conditions, the particle size is controlled, and the directional conversion of zinc ferrite to dicalcium ferrite is achieved in a high-temperature inert atmosphere. The content of dicalcium ferrite in the obtained iron-containing tailings is more than 85%, and its alkaline characteristics and iron-containing properties can adapt to the alkaline environment requirements of the blast furnace sintering process, replacing 30% to 50% of traditional alkaline fluxes including limestone and iron-containing furnace charges including iron concentrate, thereby reducing the raw material cost and energy consumption of the sintering process.

[0032] (2) Whole-process harmlessness and environmental benefits

[0033] Efficient removal of harmful elements: Through the calcification-chlorination composite activation mechanism, K, Na, Pb, and Zn are converted into volatile phases including ZnCl2, PbCl2, KCl, and NaCl at high temperatures. They are then separated by inert gas flow and collected in the low-temperature zone for desublimation. The removal rate reaches over 95%, avoiding equipment corrosion and product quality risks.

[0034] Hazardous waste reduction and resource utilization: Simultaneous treatment of dioxin-containing waste incineration fly ash and heavy metal-containing steelmaking dust; the volatile phase can be treated through step-by-step alkaline precipitation to recover Zn and Pb metal elements, forming a closed loop for hazardous waste resource utilization.

[0035] Secondary pollution suppression: using nitrogen and other inert atmosphere to suppress CaSO4 to generate dense phase Ca 10 (SiO4)3(SO4)3Cl2 reduces the risk of high-temperature resynthesis of dioxins and meets environmental emission standards.

[0036] (3) Economic benefits and process compatibility

[0037] Cost advantage: Calcium and chlorine resources in fly ash can replace traditional activators including CaO and NaCl. The dicalcium ferrite tailings can be reused in the sintering process to significantly reduce the amount of iron ore purchased, saving a lot of costs.

[0038] Process adaptability: The tailings components CaO and Fe2O3 and physical properties including particle size and fluidity are compatible with existing sintering facilities and can be added to sintering ingredients in proportion to simplify the production process.

[0039] (4) Industry application and sustainable development

[0040] This invention provides a technology for the coordinated treatment of steelmaking dust and waste incineration fly ash, addressing the low iron utilization and high fly ash treatment costs associated with traditional processes. This technology can be expanded to treat zinc-containing solid wastes such as electric furnace dust and chlorine-calcium-containing wastes such as carbide slag. This technology can promote the steel industry's transition to a zero-waste recycling system and support the large-scale application of green metallurgical technologies.

[0041] Figures in the specification

[0042] Figure 1 is the XRD pattern of tailings under different conditions. DETAILED DESCRIPTION

[0043] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0044] The present invention provides a method for synergistically detoxifying waste incineration fly ash and steelmaking furnace dust to prepare sintering-grade calcium ferrite, comprising the following steps:

[0045] S100: waste incineration fly ash and steelmaking furnace dust are uniformly mixed in a mass ratio of 1-4:1 to obtain a mixture, deionized water is added to the mixture as a binder, and particles with a particle size of less than 200 μm are prepared in a disc granulator, wherein particles with a particle size of 50-150 μm account for more than 80%, to obtain a uniform mixture; the mixture is mixed with water in a mass ratio of 10-12:1.

[0046] In the present invention, the steelmaking dust is converter dust or electric arc furnace dust, containing zinc ferrite, metal oxides and particles with a particle size of ≤150 μm, and can be recovered by a method well known to those skilled in the art or purchased commercially.

[0047] The disc of the disc granulator has a diameter of 80 cm, an inclination angle of 45°-60°, and a rotation speed of 10-30 r / min.

[0048] S200: The mixture is assisted by an inert gas flow and sent to a high temperature zone preheated to 1000-1100°C for roasting. A gradient temperature field is set in the roasting equipment. The temperature from the material inlet to the outlet gradually increases from 1000-1020°C to 1260°C, with a gradient interval of 20°C. An ultrasonic oscillation device is set in the high temperature zone. The ultrasonic frequency is 20-40kHz and the power density is 0.8-1.5W / cm 2 At the same time, a microwave radiation device is set in the high-temperature zone, the microwave frequency is 2450MHz, the power is between 10-15kW, and a rotatable material dispersion blade is installed in the roasting equipment, and the blade speed is 20-30r / min; under an inert atmosphere, the zinc ferrite structure is converted into dicalcium ferrite, and harmful elements such as Zn, Pb, K, and Na are converted into ZnCl2 and PbCl2.

[0049] In the present invention, the inert atmosphere is nitrogen or argon, which promotes the decomposition of CaSO4 and inhibits the formation of Ca 10 A dense phase of (SiO4)3(SO4)3Cl2 is generated to promote the separation of the volatile phase and the formation of dicalcium ferrite.

[0050] The calcination time is 240-360 minutes, ensuring that the zinc ferrite conversion rate is ≥98%.

[0051] S300: After calcification-chlorination composite activation roasting, an activated zinc-lead-potassium-sodium phase and a stable phase of dicalcium ferrite are generated. The dicalcium ferrite is used as an alkaline flux and an iron-containing charge to enter the sintering process.

[0052] In the present invention, the tailings are mainly composed of dicalcium ferrite (Ca2Fe2O5), and contain CaO with a mass fraction of ≥15% and Fe2O3 with a mass fraction of ≥30%, which can replace 20%-30% of the alkaline flux and iron-containing raw materials in the sintering process; the mass fractions of K, Na, Zn and Pb in the tailings are all ≤0.2%, which meets the limit requirements of the sintering process for harmful elements.

[0053] S400: The activated phase sublimates along with the inert gas flow to a low temperature zone for condensation, and is separated from the tailings for purification.

[0054] In the present invention, the temperature of the low temperature zone is 100-300°C, and the volatile phase is condensed and enriched by a program temperature control device, wherein the recovery rate of ZnCl2 and PbCl2 is ≥95%; after the volatile phase is subjected to acid-base precipitation and multi-stage crystallization separation, ZnCl2 and PbCl2 can be recovered as chemical raw materials.

[0055] The method provided by the present invention realizes the synergistic reaction of CaO and Cl elements in waste incineration fly ash and zinc ferrite in steelmaking furnace dust through calcification-chlorination composite activation, with the total volatilization rate of harmful elements being ≥98%. It can efficiently realize the synergistic harmless treatment of waste incineration fly ash and steelmaking furnace dust, and simultaneously prepare dicalcium ferrite that can be used in sintering process, thereby having significant environmental and economic benefits.

[0056] To further illustrate the present invention, the following examples are provided for detailed description. The waste incineration fly ash used in the following examples was fly ash from a domestic waste incineration plant, the steelmaking dust was converter ash from a steel mill, the deionized water was commercially available, the disc diameter of the disc granulator was 80 cm, the inclination angle was 50°, the rotation speed was 20 rpm, and the inert atmosphere was nitrogen.

[0057] Example 1

[0058] Step S100

[0059] Waste incineration fly ash and steelmaking dust were mixed uniformly in a mass ratio of 2:1 to obtain a mixture. Deionized water was added to the mixture as a binder, and the mixture and water were mixed in a mass ratio of 10:1. The mixture was then pelletized in a disc granulator with a particle size of less than 200 μm, of which 85% were particles of 50-150 μm. This yielded a uniform mixture. The disc granulator had a diameter of 80 cm, an inclination angle of 45°, and a rotation speed of 15 rpm.

[0060] Step S200

[0061] The mixture is supplemented with nitrogen gas and sent to a high temperature zone preheated to 1000°C for calcination. A gradient temperature field is set in the calcination equipment, and the temperature from the material inlet to the outlet gradually increases from 1000°C to 1260°C with a gradient interval of 20°C. An ultrasonic oscillation device is set in the high temperature zone with an ultrasonic frequency of 20-40kHz and a power density of 0.8W / cm 2 At the same time, a microwave radiation device is set in the high-temperature zone, the microwave frequency is 2450MHz, the power is between 10kW, and a rotatable material dispersion blade is installed in the roasting equipment, and the blade speed is 20r / min; under an inert atmosphere, the zinc ferrite structure is converted into dicalcium ferrite, and harmful elements such as Zn, Pb, K, and Na are converted into ZnCl2 and PbCl2.

[0062] Step S300

[0063] After calcification and chlorination combined activation and roasting, an activated zinc-lead-potassium-sodium phase and a stable dicalcium ferrite phase are produced. This dicalcium ferrite serves as an alkaline flux and iron-containing charge in the sintering process. Testing of the tailings revealed that the primary components are dicalcium ferrite (Ca2Fe2O5), containing 16% by mass of CaO and 32% by mass of Fe2O3. The mass fractions of K, Na, Zn, and Pb are all ≤0.2%.

[0064] Step S400

[0065] The activated phase sublimates to a low temperature zone (100° C.) along with the nitrogen gas flow and condenses. The volatile phase is condensed and enriched by a program temperature control device and separated from the tailings to achieve purification.

[0066] Example 2

[0067] On the basis of Example 1, the difference from Example 1 is that the waste incineration fly ash and the steelmaking furnace dust are evenly mixed in a mass ratio of 4:1. The other steps of this example are the same as those of Example 1.

[0068] Example 3

[0069] Based on Example 1, the difference from Example 1 is that the temperature of the high temperature zone is pre-set to 1020° C. The other steps of this example are the same as those of Example 1.

[0070] Comparative Example 1

[0071] Differences from Example 1:

[0072] Step S100: The mass ratio of waste incineration fly ash to steelmaking furnace dust is changed to 1.2:1, and the mass ratio of the mixture to water is changed to 8:1. After granulation, the proportion of particles with a particle size of 50-150 μm is only 70% (does not meet the requirement of >80%).

[0073] Step S200: calcining at a constant temperature of 900° C. for a constant time without ultrasonic oscillation treatment.

[0074] Other steps: the same as in Example 1.

[0075] Comparative Example 2

[0076] Differences from Example 1:

[0077] Step S200: the inert atmosphere is changed to air, and no microwave radiation treatment is performed.

[0078] Step S300: No calcification-chlorination composite activation is performed (ie, Cl element in the waste incineration fly ash is not added, and only steelmaking dust is used).

[0079] Other steps: the same as in Example 1.

[0080] test

[0081] The experiments were conducted using the Example and the Comparative Example methods, respectively. Under the same experimental conditions, the volatilization of harmful elements during the treatment process of each method was compared. The results are shown in Table 1. The chemical composition of each group of preformed calcium ferrite is shown in Table 2.

[0082] Table 1 Volatility of harmful elements during treatment (%)

[0083]

[0084] Table 2 Chemical composition of prefabricated calcium ferrite (wt.%)

[0085]

[0086] Table 1 quantitatively analyzes the volatilization of various harmful elements. It can be seen that after being treated by the method of this embodiment, all the harmful elements in the blast furnace enter the volatilization phase and are separated from the tailings.

[0087] Table 2 quantitatively analyzes the composition of the produced calcium ferrite. It can be seen that the composite ferrite is primarily composed of dicalcium ferrite, fully meeting the requirements for harmful elements in the sintering process. It is suitable for use as a supplementary alkaline flux along with iron-containing charge material to be reintroduced into the blast furnace ironmaking process. This allows for the addition of high-purity preformed calcium ferrite to the sintering process, reducing combustion consumption and improving efficiency. Furthermore, it can be seen that the effect is even better at temperatures between 1000 and 1100°C, achieving efficient resource utilization with low energy consumption. This method effectively achieves the harmless treatment of two hazardous wastes and the resource recovery of solid waste.

[0088] Figure 1 is the XRD pattern of tailings under different conditions; Figure 1 It can be seen that after the calcification-chlorination composite activation of the waste incineration fly ash, the original inert phase zinc ferrite is completely reacted, and the phase contained in the tailings is mainly Ca2Fe2O5 phase, that is, composite calcium ferrite, among which harmful elements in the blast furnace such as K, Na, Pb, and Zn are almost completely activated and separated.

[0089] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. The preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification.

Claims

1. A method for synergistically detoxifying waste incineration fly ash and steelmaking dust to prepare sintering-grade calcium ferrite, characterized in that: The following steps are involved: S100: mixing waste incineration fly ash and steelmaking dust in a mass ratio of 1-4:1 to obtain a mixture, adding deionized water as a binder to the mixture, and forming particles with a particle size of less than 200 μm in a disc granulator, wherein particles with a particle size of 50-150 μm account for more than 80%, to obtain a uniform mixture; The mixture is mixed with water in a mass ratio of 10-12:1; S200: The mixture is assisted by an inert gas flow and sent to a high temperature zone preheated to 1000-1020°C for calcination. A gradient temperature field is set in the calcination equipment. The temperature from the material inlet to the outlet gradually increases from 1000-1020°C to 1260°C, with a gradient interval of 20°C. An ultrasonic oscillation device is set in the high temperature zone. The ultrasonic frequency is 20-40kHz and the power density is 0.8-1.5W / cm 2 At the same time, a microwave radiation device is set in the high temperature zone, the microwave frequency is 2450MHz, the power is between 10-15kW, and a rotatable material dispersion blade is installed in the roasting equipment, and the blade speed is 20-30r / min; under an inert atmosphere, the zinc ferrite structure is converted into dicalcium ferrite, and harmful elements such as Zn, Pb, K, and Na are converted into volatile phases of ZnCl2, PbCl2, KCl, and NaCl; S300: After calcification-chlorination composite activation roasting, an activated zinc-lead-potassium-sodium phase and a stable dicalcium ferrite phase are generated. The dicalcium ferrite is used as an alkaline flux and an iron-containing charge to enter the sintering process; S400: The activated phase sublimates along with the inert gas flow to a low temperature zone for condensation, and is separated from the tailings for purification.

2. The method according to claim 1, characterized in that The steelmaking dust in step S100 is converter dust or electric arc furnace dust, and contains zinc ferrite, metal oxides, and particles with a particle size of ≤150 μm.

3. The method according to claim 1, characterized in that The inert atmosphere in step S200 is nitrogen or argon, which promotes the decomposition of CaSO4 and inhibits the formation of Ca 10 A dense phase of (SiO4)3(SO4)3Cl2 is generated to promote the separation of the volatile phase and the formation of dicalcium ferrite.

4. The method according to claim 1, wherein The tailings in step S300 are mainly composed of dicalcium ferrite (Ca2Fe2O5), and contain CaO with a mass fraction of ≥15% and Fe2O3 with a mass fraction of ≥30%.

5. The method according to claim 4, characterized in that The mass fractions of K, Na, Zn and Pb in the tailings are all less than or equal to 0.2%, which meets the limit requirements of the sintering process on harmful elements.

6. The method according to claim 1, characterized in that The temperature of the low temperature zone in step S400 is 100-300° C., and the volatile phase is condensed and enriched by a program temperature control device, wherein the recovery rate of ZnCl 2 and PbCl 2 is ≥95%.

7. The method according to claim 6, characterized in that After the volatile phase is subjected to acid-base precipitation and multi-stage crystallization separation, ZnCl2 and PbCl2 can be recovered as chemical raw materials.

8. The method according to claim 1, characterized in that The disc of the disc granulator has a diameter of 80 cm, an inclination angle of 45-60 degrees, and a rotation speed of 10-30 r / min.

9. The method according to claim 1, characterized in that The calcination time in step S200 is 240-360 min to ensure that the zinc ferrite conversion rate is ≥98%.

10. The method according to any one of claims 1 to 9, characterized in that Through the calcification-chlorination composite activation, the synergistic reaction of CaO, CaCO3, Ca(OH)2 and CaClOH in the waste incineration fly ash and zinc ferrite ZnFe2O4 in the steelmaking furnace dust is achieved, and the total volatilization rate of harmful elements is ≥98%.

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