Method for removing volatile components from industrial dust and valuable product

Abstract

A method for producing a valuable product from industrial dust is described, the method comprising: i) providing industrial dust having at least one valuable and a first concentration of a volatile component to a heating device having an operating temperature of 600°C or more; ii) reprocessing the industrial dust by the heating device, wherein the reprocessing comprises: iia) heating the industrial dust at a rate of 20°C / min; iib) heat-treating the industrial dust by the heating device at a treatment temperature in the range of 900°C to 1200°C, particularly in the range of 1000°C to 1100°C, for 30 minutes or more; iic) controlling and / or adjusting oxidation conditions during the reprocessing; Reprocessing includes at least partially removing volatile components from the industrial dust, and iii) providing a value product. Further, a reprocessed value product is described.

Description

Technical Field

[0001] The present invention relates to a method for producing valuable product from industrial dust. Furthermore, the present invention relates to a valuable product obtained by reprocessing (preparation) of industrial dust.

[0002] Accordingly, the present invention can relate to the technical field of reprocessing industrial dust. In particular, the present invention can relate to the technical field of removing volatile components from industrial dust, thereby obtaining a valuable product. Background Art

[0003] For example, industrial dust from metal production or processing (e.g., in steelworks) often contains desirable and recoverable valuable materials, but also contains undesirable residues including undesirable metals (in the form of compounds and / or as elements) and volatile components (e.g., halogen compounds). However, it remains a technical problem to process industrial dust cost-effectively to obtain a reprocessed valuable product that can be reused as a raw material source. This will be described below with reference to an example of the prior art in which zinc oxide, which is a valuable material, is collected from halogen-contaminated steelworks dust.

[0004] The main product of reprocessing steel mill dust using appropriate processes is so-called secondary zinc oxide, which can be used almost 100% as a substitute or supplement to zinc concentrate extracted from ore. Due to the high proportion of zinc oxide, the lead content, and the concentrations of halogen contamination or other volatile components in this recycled product, conventional methods (primarily the so-called Wertz process) limit the replacement rate in the primary zinc industry to 10-15%. Wertz oxide (which is zinc oxide loaded with interfering substances) is generally washed, but charging into the zinc industry's roasting process is unavoidable to remove residual halogen content (fluorine, chlorine, bromine, or iodine) or halogen compounds, and other volatile compounds. This is because, in zinc electrolysis, chlorine results in increased electrode corrosion and the generation of chlorine gas, which can endanger health. The disadvantage of fluorine in the electrolyte lies in its attack and dissolution of the aluminum oxide layer on the cathode surface. This results in a high tendency for refined zinc to adhere to the cathode, associated downtime, and consequent zinc loss, as well as high cathode wear.

[0005] Nevertheless, it is desirable to replace primary concentrate with secondary zinc oxide. The large amount of iron carried into primary zinc production by concentrate increases the proportion of precipitated residue, for which there is currently no economical reprocessing method, and therefore it must be stored under high costs and environmental regulations. For every ton of zinc produced, 1 ton of iron residue, mainly jalosite, is generated. Therefore, it is advantageous to increase the proportion of secondary zinc oxide with an originally low iron content during zinc extraction. Instead of disposal, ideally, a zero-waste process should be aimed for, where iron alloys are supplied for use in steel mills, halogen-containing materials for use in the chemical industry, and materials for use in the building materials industry. This is a significant improvement compared to the more than 65% proportion of residual materials stored in the Wertz process.

[0006] In the case of electric arc furnace dust (EAFD), impurities come from molten steel scrap and, in part, from the slag former. Surface coatings, lacquers, and plastic fractions are common sources of halogens in steel mill dust. At the dominant process temperatures, chlorine and fluorine volatilize as compounds with lead, potassium, or sodium, and accumulate in the dust along with other volatile elements such as cadmium oxide, and especially zinc oxide. The main product when recycling EAFD is ZnO contained in the dust. This is usually converted to Zn by reduction with carbon and evaporates at process temperatures of 1000°C to 1100°C (the boiling point of Zn is 907°C). Due to the high oxygen affinity of gaseous zinc, immediate exothermic reoxidation occurs in the exhaust system from Zn to ZnO, which is also a product of the recycling process. Most halogen compounds present in steel mill dust have high vapor pressures, and some even have boiling points lower than the process temperature, so they also evaporate and accumulate in the product (ZnO), contaminating it. This product is used almost 100% in the primary zinc industry as a substitute for zinc concentrate extracted from ore. However, due to halogen loading and lead concentration, the substitution rate in primary zinc production is limited to 10-15%. On the one hand, the cooling effect of the oxide makes it desirable for use in roasting equipment, while on the other hand, the contained halogen compounds can result in undesirable caking.

[0007] Nevertheless, it is desirable to replace primary concentrate with secondary ZnO. To reduce the burden of the roasting process, contaminated secondary ZnO from common recycling processes such as Waelzrohr undergoes a laborious subsequent soda washing process. In this case, very low chlorine and alkali content can be achieved, but this method cannot remove lead and fluorine. Alternatively, there is a modified form of heat treatment of contaminated ZnO. However, these are disadvantageous in that they consume a great deal of energy and result in significant zinc loss, and require grinding after treatment to provide zinc oxide that can be efficiently leached for primary zinc production. [Overview of the project]

[0008] The object of the present invention is to provide a method that enables the efficient and robust removal of volatile components from industrial dust containing valuable substances.

[0009] The above problems are solved by the subject matter described in the independent claim. Preferred embodiments will become apparent from the dependent claims.

[0010] According to one aspect of the present invention, a method for producing a valuable product from industrial dust (in a heating device) (or a corresponding method for operating a heating device) is described. The method is: i) To provide industrial dust (as dust particles or as aggregated dust particles) having a first concentration of at least one valuable substance (e.g., metal oxide, particularly zinc oxide) and volatile components (e.g., halogens and metals that are not valuable substances) to a heating device having an operating temperature of 600°C or higher (particularly 700°C or higher, and even more particularly 800°C or higher), ii) Reprocessing industrial dust with a (preheated) heating device, and including, reprocessing, iia) Heating industrial dust (for example, by a heating device) at a rate of 20°C / min or more (especially 30°C or more, even more specifically 50°C or more, even more specifically 100°C or more, even more specifically 150°C or more) (or the highest possible rate of increase) (very rapidly), iib) Heat-treating industrial dust with a heating device at a processing temperature in the range of 900°C to 1200°C, especially in the range of 1000°C to 1100°C, for 30 minutes or more (especially 60 minutes or more, and even more especially 120 minutes or more) (appropriately), and (at the same time) iic) controlling and / or regulating the oxidation conditions during reprocessing (for example, by controlling / regulating the supply of air / oxygen). These reprocessing steps are performed so that the volatile components of the industrial dust are removed (at least partially). The method further comprises iii) providing a valuable product.

[0011] The valuable product obtained by the above reprocessing is obtained having, in particular, at least one valuable substance and a second concentration of volatile components that is (significantly) lower than the first concentration of volatile components (the volatile components are significantly reduced or (substantially) removed, while the valuable substances remain and may even be concentrated).

[0012] In this context, the term "provide" can refer to any addition of industrial dust to / into a heating device. In this context, the term "dust" can refer to any material in the form of solid particles. The particles can be of various sizes and can come from various sources. In one example, the particles may remain suspended in a gas, particularly in the air, for a period of time. In another example, the dust may consist of particles ranging in size from millimeters, particularly from micrometers.

[0013] Industrial dust is an extract that is the starting material of the method, and the product of the method is a valuable product. Within the scope of this specification, the term “industrial dust” may, in particular, refer to extracts that arise in the form of dust, substantially as waste, in manufacturing. For example, in metal manufacturing or metalworking, metal-containing dust may be generated or generated as waste. In an exemplary example, industrial dust may arise as so-called steelwork dust during processes in a steelworks (e.g., an electric arc furnace for melting scrap).

[0014] When the method is performed repeatedly, the industrial dust used may itself be a valuable product from a previous run of the method, or may be based on such a valuable product.

[0015] Industrial dust may contain, or consist of, several types of dust from one or more sources. Industrial dust may exist, for example, as a powder, as dust particles, or as aggregated dust particles, for example, as pellets.

[0016] Industrial dust contains at least one valuable substance (for example, a preferably desirable or economically relevant metal oxide, particularly zinc oxide) and an impurity of a first concentration.

[0017] Here, the contents of industrial dust should be understood as valuable materials, and the goal is to utilize them as raw materials. In addition to valuable materials, industrial dust also contains other contents referred to here as impurities. These impurities may, in some cases, make the utilization of valuable materials difficult. To enable economically and technically meaningful utilization, the goal is to enrich the valuable materials in industrial dust, or at least partially remove the impurities. Valuable material products contain at least one valuable material, and may also contain multiple different valuable materials.

[0018] The method according to the present invention removes impurities from industrial dust at least partially. This method makes it possible to provide a valuable product having at least one valuable substance. The valuable product has a second concentration of impurities (potentially volatile components) that is (potentially significantly) lower than a first concentration of impurities (potentially volatile components) in the industrial dust. The second concentration may be 0 or substantially 0. While impurities are significantly reduced or, in some cases, removed, valuable substances remain and are even concentrated.

[0019] According to the present invention, industrial dust is first supplied to a heating device having an operating temperature of 600°C or higher. The industrial dust may be supplied, for example, as dust or as aggregates after aggregation. The provision includes making the industrial dust available for use by the heating device, for example, by introducing the industrial dust into the heating device. That is, the heating device is already preheated to 600°C or higher when the industrial dust is supplied. The operating temperature is preferably 700°C or higher, and particularly preferably 800°C or higher.

[0020] Within the scope of this specification, the term “heating device” can be understood as any device suitable for heating materials, particularly industrial dust. For this purpose, the heating device may have a cavity into which material can be introduced and subsequently heat-treated. The temperature within the heating device is particularly controllable or adjustable. In addition, if heat is generated (e.g., by a burner) by an oxidation process, the supply of an oxidizing agent such as air and / or oxygen may be controllable. The heating device may already be heated when the material to be heated is introduced. In addition, particularly rapid heating, such as at least 150°C / min, can be achieved using the above-described heating device. In one example, the heating device may be a metallurgical processing unit. In an exemplary example, the heating device is a fire-resistant, rotatable vessel. Other embodiments include, for example, a top-blown rotary converter (TBRC) or short drum furnace (KTO) with the burner side and exhaust side combined, or a Wertz kiln that separates flame heating from exhaust gas outlets facing each other.

[0021] After supply, the industrial dust is reprocessed by a heating device, for example, within the heating device. Reprocessing involves heating the industrial dust by a heating device, for example, within the heating device. This is done at a rate of at least 20°C / min, preferably 30°C / min, particularly preferably at least 50°C / min, particularly preferably at least 100°C / min, or more preferably at least 150°C / min. This heating is extremely rapid, and the rate of rise during heating is selected to be as high as possible. According to the present invention, reprocessing involves treating the industrial dust by a heating device (for example, within the heating device) at a processing temperature in the temperature range of 900°C to 1200°C (preferably 1000°C to 1100°C) for at least 30 minutes (preferably at least 60 minutes, particularly preferably at least 120 minutes, or more preferably at least 150 minutes).

[0022] Oxidizing conditions are set during reprocessing. That is, industrial dust is exposed to oxidizing conditions during reprocessing. The setting of oxidizing conditions is preferably performed accurately. Oxidizing conditions can be controlled and / or adjusted. That is, the conditions are set such that reducing conditions do not exist, and in some cases, the manner in which oxidizing conditions develop in the heating device is adjusted and / or controlled. This can be achieved, for example, by controlling and / or adjusting the supply of an oxidizing agent (such as air and / or oxygen), or by controlling and / or adjusting the supply of air and / or oxygen to a burner used as a heat source (in addition or alternatively, an electric heating device can also be selected).

[0023] Within the scope of the present specification, the term "valuable product" refers to a product obtained from the above-mentioned industrial dust through application of the method steps according to the present invention. The valuable product can exist as dust, but preferably the valuable product can also exist as an aggregate of dust particles. The valuable product is characterized in that at least one valuable substance, which can be, for example, a metal oxide such as zinc oxide or copper oxide, is present therein. The valuable product is characterized in that the concentration of impurities therein is significantly reduced compared to industrial dust. In particular, the proportion of halogens and / or undesirable metals can be greatly reduced. In a preferred embodiment, the concentration of valuable substances in the valuable product can be increased compared to the supplied industrial dust.

[0024] Impurities may be volatile components of industrial dust. Within the scope of the present specification, the term "volatile component" can particularly refer to a component of industrial dust that transitions to the gas phase via evaporation when a specific temperature is present (optionally after one or more chemical reactions). In one example, the specific temperature can be defined as lower than the melting temperature of the industrial dust. In another example, the specific temperature can be, for example, lower than 1500°C. Volatile components can be, for example, halogen compounds of chlorine or fluorine; for example, lead fluoride volatilizes at 1293°C, or lead chloride volatilizes at 950°C.

[0025] According to an exemplary embodiment, the present invention provides, in a heating device, at least the following steps - introducing industrial dust at 600° C. or higher, - heating at a rate of (at least) 20° C. / min or more, and - heat treating in the range of 900° C. to 1200° C. for (at least) 30 minutes, wherein oxidation conditions are controlled and / or regulated, it can be based on the idea that when a specific reprocessing process including said steps is carried out, efficient and robust removal of (at least part of) volatile components from valuable material-containing industrial dust is enabled.

[0026] Numerous attempts have already been made in the prior art to selectively volatilize impurities from industrial dust, such as undesirable volatile components that significantly reduce the value of industrial dust or render them unusable. However, all these attempts have ended in failure. Currently, there is no known thermal process that enables efficient, robust, and economically viable removal of volatile components from industrial dust.

[0027] However, it has now surprisingly been found in the course of extensive and intensive research that the technical prejudice that volatile components cannot be removed efficiently and robustly from industrial dust can be overcome by the method according to the present invention.

[0028] For successful progress and the accompanying maximum achievable extraction rate of impurities, in particular volatile components, from industrial dust, temperature control in the first few minutes, but also the subsequent heat treatment, is critically important. This can ensure that impurities, in particular volatile components, are not given time to react with other compounds contained in the industrial dust to form non-volatile compounds. Formation of new compounds that do not volatilize at the described process temperatures is thereby efficiently prevented or inhibited.

[0029] While I don't intend to be bound by any particular theory, the current conventional temperature profile starts with the assumption that non-volatile components are always formed by chemical reactions between volatile components. For example, calcium fluoride, which has a high boiling point of 2533°C, can be formed. However, unlike this, the conditions according to the present invention inhibit the chemical reaction that results in non-volatile components and instead promote the chemical reaction that results in volatile components, such as the reaction between lead oxide and calcium fluoride, which results in lead fluoride with a boiling point of only 1293°C. Similarly, by precisely applying the conditions according to the present invention, it appears that volatile components will react to form other volatile components, and only a very small amount of non-volatile components will be formed, or not at all.

[0030] While the described method enables environmentally friendly recycling of industrial dust into valuable materials, traditionally, this industrial dust had to be reprocessed in a time-consuming and less environmentally friendly manner, or immediately disposed of at cost.

[0031] The extracted valuable material, such as zinc oxide, can be used as a substitute for primary concentrate, offering flexible applications. High-purity zinc oxide can be directly used in economically relevant markets such as the tire industry, ceramics manufacturing, and chemical industry.

[0032] In summary, the described method is more efficient, energy-optimized, and resource-saving than previous methods, and therefore could be a more environmentally friendly alternative.

[0033] According to one embodiment, the impurities include volatile components. In one embodiment, the volatile components include halogens, particularly fluorine and / or chlorine, mainly in the form of compounds rather than as elements. In addition to or instead of these, the volatile components include undesirable or economically irrelevant metals, particularly in the form of compounds, and non-elemental metals, and more particularly metals from the group consisting of lead, cadmium, sodium, potassium, and calcium. This has the advantage of effectively removing undesirable components that significantly reduce the value of industrial dust.

[0034] In another embodiment, the valuable materials include metal oxides (particularly zinc oxide and / or copper oxide). This has the advantage that industrial dust waste can serve as a raw material repository for industrial-related materials. Industrial dust, especially dust from metal manufacturing or metal processing, inherently contains numerous metals or metal compounds such as metal oxides, which can be valuable materials advantageous for producing, for example, secondary / high-purity metals or metal compounds such as metal oxides.

[0035] According to another embodiment, industrial dust exists, at least substantially, in the form of dust particles, particularly in the form of dust particles arising from metal manufacturing or metalworking.

[0036] According to another exemplary embodiment, the dust particles include steel mill dust ("Steel mill dust") or dust from the copper industry. In particular, it includes at least one dust from the group consisting of electric arc furnace dust ("electric arc furnace dust," EAFD), dust from foundries, dust from integrated steelmaking routes, and dust from sintering plants. This can offer the advantage of efficiently reprocessing dust particles from various industrially relevant production processes.

[0037] In another embodiment, providing industrial dust involves agglomerating the dust particles of the industrial dust. This can further enhance the efficiency of the method according to the present invention, as dust scattering (Verstaubung) can be significantly suppressed. In one example, agglomeration of dust particles can be carried out as pelletization (e.g., by a pelletizing dish). In another example, agglomeration can be enabled by using a forced mixer. Water may suffice as an additive for the required green strength of the agglomerate. For example, a pre-existing halogen can combine with water to provide the required binding force.

[0038] According to another embodiment, the method according to the present invention is carried out discontinuously or in batches (particularly by charging agglomerated industrial dust). This may have the advantage that the required heat treatment is carried out accurately and robustly.

[0039] Conventionally, the starting point has been that the method for producing valuable products must always be carried out continuously in order to achieve the desired economic efficiency. Surprisingly, however, in this case, it has been found that the exact opposite, namely a discontinuous process, can yield the desired results. In a preferred example, industrial dust is agglomerated, and the agglomerates can then be supplied to reprocessing as a charge. Furthermore, the method for producing valuable products according to the present invention can be carried out in batches to ensure that the desired necessary conditions are met in each batch.

[0040] In another embodiment, providing industrial dust involves drying, in particular, agglomerated industrial dust. This allows the method to be carried out more efficiently, as it avoids explosions caused by excessively rapid escape of water vapor. In one example, the drying temperature is in the range of 105 to 350°C, particularly 200 to 300°C. In one example, the required drying duration is 24 to 72 hours, particularly 40 to 60 hours.

[0041] According to another embodiment, the heat treatment includes controlling and / or regulating water vapor in a heated atmosphere such that a partial pressure of water vapor of at least 0.1 bar is present. The partial pressure can represent the partial pressure of a single component or fraction in an (ideal) gas mixture. In this case, the control and / or regulation is performed, for example, by the moisture content of industrial dust, or, if a burner is used, with respect to the type of substance supplied to the burner, such as fuel or oxidizer, or the ratio of their amounts. The control and / or regulation of water vapor in a heated atmosphere can also be performed by controlling and / or regulating the pressure and / or temperature and / or volume conditions within the heating vessel.

[0042] In another embodiment, the heat treatment includes mixing with industrial dust. This can be achieved, in particular, by rotating (at least temporarily) at least a portion of a heating device filled with industrial dust. This has the advantage of allowing continuous mixing and an increase in the active surface area of ​​the material, thereby ensuring uniform treatment. In one example, the rotation speed may be in the range of 1 to 10 rpm, particularly 2 to 3 rpm.

[0043] In another embodiment, setting the oxidation conditions involves controlling and / or adjusting the oxidation conditions, i.e., the combustion air ratio being hyperstoichiometric, particularly in the range of 1.1 to 1.5 (more particularly in the range of 1.3 to 1.4), and supplying the fuel with an oxidizer (particularly oxygen and / or air) such that the limit of the range is included. This can have the advantage of having efficient oxidation conditions that are precisely controllable or adjustable.

[0044] According to another embodiment, industrial dust has a first concentration of valuables, and reprocessing involves concentrating the valuables to a second concentration of valuables higher than the first concentration. This has the advantage that the valuables are concentrated in the valuables product, thereby making it a more valuable raw material.

[0045] According to another embodiment, the method according to the present invention (particularly during heating and / or heat treatment) includes preventing (at least partially) halogens and / or metals from chemically reacting to form non-volatile components (e.g., calcium fluoride). In addition to this, or instead, the chemical reaction of halogens and / or metals to form volatile components (e.g., lead fluoride) is promoted. This can offer the advantage that substantially only volatile components are present as impurities, or no new non-volatile substances are generated, thereby allowing the evaporation of these impurities or newly generated substances without non-volatile residues.

[0046] According to another embodiment, this method has the following features i) Remove at least 90%, particularly at least 95%, of the content of at least one element from the group consisting of chlorine, lead, and cadmium from industrial dust. II) Removing at least 80%, particularly at least 85%, of the content of at least one element from the group consisting of fluorine and / or potassium from industrial dust. iii) Remove 45% (especially 50%) or more of sodium from industrial dust. It includes at least one of the following.

[0047] These features, in one example, reflect the efficiency of removing impurities, particularly volatile components, demonstrating a way to significantly increase the value of industrial dust without incurring high costs.

[0048] According to another embodiment, heating of industrial dust is carried out at a rate of at least 30°C / min, preferably at least 50°C / min, particularly preferably at least 100°C, and most preferably at least 150°C. In the exemplary embodiment, these parameters were found to be particularly efficient.

[0049] According to another embodiment, the heat treatment of industrial dust in the heating device is carried out for at least 30 minutes, preferably at least 60 minutes, particularly preferably at least 120 minutes, and most preferably at least 180 minutes. In the exemplary embodiment, these parameters were found to be particularly efficient.

[0050] Another aspect of the present invention describes a method for providing metal oxides, particularly zinc oxide and / or copper oxide, the method comprising i) producing a valuable product according to the method of the present invention and / or using a valuable product produced in correspondence therewith, and ii) further reprocessing the valuable product to provide a high-purity metal oxide and / or secondary metal oxide.

[0051] According to another embodiment, further reprocessing of the valuable product is carried out without electrolysis. This may have the advantage of saving energy and costs.

[0052] According to another aspect of the present invention, a reprocessed valuable product is described which is produced from industrial dust and has i) zinc oxide (particularly at least 10 weight percent, more particularly at least 20 weight percent, more particularly at least 25 weight percent, and more particularly at least 30 weight percent) and at least one of the following features: a) a fluorine concentration of 0.2 weight percent or less, b) a halogen concentration of 2 weight percent or less, c) a lead concentration of 1 weight percent or less, d) a cadmium concentration of 0.05 weight percent or less, and e) a volatile component concentration of 5 weight percent or less.

[0053] In another embodiment, the reprocessed valuable product has dust particles that are (substantially) aggregated. This feature can reflect a manufacturing process in which the dust particles are aggregated (e.g., into pellets). This has the advantage that (excessive) dust scattering is favorably prevented. In addition, the transport of dust by airflow, for example, can be favorably prevented.

[0054] According to another embodiment, the valuable product has dust particles that are (substantially) aggregated. [Modes for carrying out the invention]

[0055] Several exemplary embodiments of the present invention will be described in detail below.

[0056] According to exemplary embodiments, a method for selectively removing halogens and other volatile components from steel mill dust by precise heat treatment under controlled oxidation conditions is described, and the use of steel mill dust obtained by such method, from which most of the harmful associated elements and compounds have been removed, as well as for producing high-purity secondary zinc oxide, is described.

[0057] According to exemplary embodiments, steel mill dust loaded with volatile components (halogen compounds, lead compounds, or lead) may need to be reprocessed so that most of the halogen compounds and other volatile components are removed, allowing zinc oxide to be extracted from the dust. With regard to substituting for primary concentrate, zinc oxide offers greater usability, or, if the resulting zinc oxide is of high purity, can be used directly in economically attractive markets for high-quality zinc oxide (such as the tire industry, ceramics, and chemical industry). This also leads to potential energy savings by eliminating zinc electrolysis (which is part of the primary process).

[0058] According to exemplary embodiments, the object of the present invention is to provide a method for removing halogen compounds and other volatile components from zinc oxide-containing steel mill dust generated, for example, when steel scrap is melted in an electric arc furnace. Thus, it is ensured that the steel mill dust thus treated becomes a starting point for producing high-purity secondary zinc oxide. Consequently, even if the amount of secondary zinc oxide used increases, the proportion of iron residue generated in primary zinc production compared to concentrate can be dramatically reduced, or, instead, the value creation from reprocessing steel mill dust is significantly improved. This results from the fact that the recycled product, zinc oxide, can be sold at a much higher price in the market for high-quality zinc oxide. If the quality of the product is improved by the novel method, the novel method is more efficient, energy-optimized, resource-saving, and therefore a more environmentally friendly alternative than conventional methods.

[0059] According to exemplary embodiments, this method comprises the following steps: i) agglomerating the industrial dust, ii) drying it, and iii) precisely heat-treating it under controlled oxidation conditions. At the end of the treatment, >90% of chlorine, lead, and cadmium are removed from the steelworks dust (or the provided industrial dust), >80% of fluorine is removed, and the potassium and sodium content is significantly reduced (e.g., by at least 50%). In this case, the central aspect is that, due to the oxidation conditions, the zinc oxide contained in the steelworks dust remains almost completely in the solid material, and consequently, the concentration of valuable metals increases by removing impurities. Therefore, steelworks dust from which most halogen compounds and other volatile compounds have been removed can be used as a starting product to produce qualitatively higher-value secondary zinc oxide in a normal recycling process, or to produce qualitatively very high-value zinc oxide in a subsequent reduction method step adjusted to match this heat-treating step as specifically described.

[0060] According to exemplary embodiments, the following advantages can be achieved: i) improved product quality of valuable materials (especially zinc oxide); ii) the applicability of the generated valuable materials extends beyond primary metallurgy to include high-quality metals; iii) the proportion of precipitated residue in primary metal production can be reduced; iv) process equipment can be protected from corrosion (due to high halogen loads) through precise exhaust gas induction and cooling; v) the separated and concentrated halogen residue can be reused as a raw material for corresponding (industrial) applications (further reprocessing in the chemical industry, e.g., extraction of lead compounds with lead chloride); vi) energy consumption can be kept low by charging at high temperatures to the immediate reduction step for metal oxide extraction; and vii) the above process can be implemented even in small-scale facilities (e.g., 10,000 tons / year production), whereas the use of a Wertz kiln from the prior art is only feasible at a minimum tonnage of approximately 100,000 tons / year.

[0061] Two exemplary embodiments of the invention are described in detail below.

[0062] Example 1 In the (first) method step, agglomeration is performed to prevent excessive dust scattering as a result. In this case, both pelletization using a pelletizing tray and agglomeration using a forced mixer are possible. Water is sufficient as an additive for the required green strength of the agglomerates. The halogen compounds contained in the steelworks dust combine with water to provide the necessary binding strength. The provided steelworks dust contains halogen compounds including chlorine and fluorine, and other volatile components including lead and cadmium. The dust is particularly electric arc furnace dust (EAFD), but is also similar residual material such as dust from foundries, dust from integrated steelmaking routes including secondary metallurgy, dust from sintering plants, and dust from the copper industry.

[0063] Table 1 below summarizes the typical composition of high-zinc steel mill dust from electric arc furnace routes. Table 1: Typical composition of steel mill dust with high zinc content [Table 1]

[0064] In the next step, the dust aggregates are thoroughly dried to avoid subsequent rupture due to excessively rapid escape of water vapor. The drying temperature is in the range of 105-350°C (especially 200-300°C). The required drying duration is 24-72 hours, usually 40-60 hours, until the weight constant is reached.

[0065] In the next step, the generated dust aggregates are charged into a heating device (e.g., a metallurgical treatment unit) and subjected to precise heat treatment under controlled oxidation conditions to selectively volatilize volatile components. A refractory-lined rotating vessel is used as the heating device. The position of the flame heating and exhaust gas induction play secondary roles. Similar to a Wertz kiln, which separates the flame heating and exhaust gas outlets, a top-blown rotary converter (TBRC) or short drum furnace (KTO) with a single burner and exhaust side is also possible. The process temperature is 900-1200°C (particularly 1000-1100°C). The processing duration required to remove most of the halogen compounds and other volatile components from the steelworks dust may be 2-3 hours (preferably 1.5 hours).

[0066] The rotational motion of the container ensures continuous mixing and an increase in the active surface area of ​​the material being introduced, thereby guaranteeing uniform processing of aggregates. In this case, the rotation speed can vary within the range of 1 to 10 rpm (especially 2 to 3 rpm).

[0067] Flame heating is carried out by a burner that utilizes pure oxygen or air to burn the gas. Controlled oxidation conditions are achieved by controlled and / or regulated supply of oxygen / air. In this case, the combustion air ratio λ is 1.1 to 1.5 (particularly 1.3 to 1.4), depending on the composition of the dust present.

[0068] During the heating phase, a heating rate of 150°C / min is preferably planned (at any point). This ensures that halogen compounds and other volatile components in the steelworks dust are not given time to react with other compounds in the feedstock (particularly to become non-volatile components). This effectively prevents the formation of compounds that may not volatilize at the specified process temperature. If the described temperature control (and in particular the described atmosphere composition) is not observed at this stage of the processing time, efficient removal of halogens and other volatile components will be impossible.

[0069] As an example, the possibility of calcium fluoride or calcium chloride formation can be cited, which occurs at heating rates different from those described (especially excessively slow). While fluorine tends to volatilize in combination with sodium, potassium, or lead under dominant conditions, calcium fluoride cannot be removed by evaporation. The fluorine content remaining in treated steel mill dust in such scenarios leads to a reduction in the achievable quality of the products generated at such process stages.

[0070] When the dominant temperature is 900-1200°C (especially 1000-1100°C), volatilization of volatile compounds contained in the dust, particularly not only halogen compounds but also other volatile compounds, from industrial dust begins immediately.

[0071] Therefore, in the first stage of the process, the concentrations of elements such as cadmium, lead, and chlorine are reduced, but the sodium, potassium, and fluorine content is also reduced, with little of the existing fluorine compounds being converted to non-volatile calcium fluoride.

[0072] In addition to cadmium oxide, lead partially evaporates as lead oxide, but gaseous lead oxide also evaporates as lead chloride and potentially formed lead fluoride through reactions with other fluorides.

[0073] With rapid heating rates, additional processes occur that can further increase fluorine extraction. Any calcium fluoride already present may react with gaseous lead oxide to form lead fluoride and calcium oxide again, thereby enabling efficient volatilization. However, this only occurs if the heating rate is high and the atmospheric conditions in the reaction vessel are set / controlled, thereby preventing premature evaporation of lead oxide. In other words, it is important to prevent the omission of critically important reactants in the thermal reaction window of the following equation. CaF 2(s) +PbO (g) =PbF 2(g) +CaO (s)

[0074] The decrease in sodium and potassium content, as well as chlorine and fluorine content, is mainly due to the further evaporation of halogen compounds, including lead, sodium, and potassium, present in the steel mill dust. In the second stage of treatment, compounds such as sodium and potassium, along with fluorine, volatilize steadily but slowly at low vapor pressure (e.g., in a filter house).

[0075] At the end of the process, compared to the original industrial dust, >90% of chlorine, lead, and cadmium in the steel mill dust are removed, >80% of fluorine is removed, and the potassium and sodium content is significantly reduced (e.g., by more than 50%).

[0076] In this process, it is essential that, based on the oxidation conditions, the zinc oxide contained in the steel mill dust remains almost completely in the solid material, and consequently, the concentration of valuable metals in this solid material increases.

[0077] Therefore, steel mill dust from which most of the halogens have been removed can be used as a starting product for producing secondary zinc oxide in a general recycling process, or for producing qualitatively high-value zinc oxide in a newly developed method step that has been adapted to a preceding step.

[0078] Example 2 As a starting point, steel mill dust from the operation of an electric arc furnace that produces construction steel using 100% scrap, and steel mill dust from the operation of an LD converter that uses approximately 20% scrap were used. Two tests were conducted according to the processing and measurement scheme described below. One test was conducted using only electric arc furnace dust, and the second test was conducted using a mixed dust (80% electric arc furnace dust + 20% LD dust). Tables 2 and 3 below show the composition of the dust used in the tests. Table 2: Composition of electric arc furnace dust used to remove halogens and other volatile components [Table 2] Table 3: Composition of mixed dust used to remove halogens and other volatile components [Table 3]

[0079] Dust was agglomerated using a pelletizing tray. Water was added and mixed as an additive to achieve the necessary green strength for agglomeration. The high halogen content combines with water to provide the required bonding strength and thus sufficient green strength. Hydration of calcium oxide plays a supporting role.

[0080] After pelletizing was complete, the aggregates were dried. Drying was carried out at 200°C for 48 hours.

[0081] After drying, the pellets were formed as TBRC and used in a rotating metallurgical vessel lined with refractory material. A controlled and / or regulated O2 supply provided controlled oxidation conditions during the process, and energy input for precise heat treatment was provided by a CH4 / O2 burner. The processing was carried out in 40 kg batches.

[0082] The process parameters selected during precise heat treatment under controlled oxidation conditions are listed in Table 4 below. Table 4: Selected Process Parameters [Table 4]

[0083] During processing, in addition to measuring the temperature of the permanently installed furnace atmosphere, the dominant temperature in the bulk material was also checked at regular intervals. At 10-minute sampling intervals, the progress of the process of removing halogens and other volatile components from steelmaking dust (e.g., by a filter house) was continuously monitored within the range of appropriate heat treatment under controlled oxidation conditions.

[0084] After the processing was complete, the processed dust aggregates were removed from the furnace and transferred to a steel mold to cool to room temperature. After complete cooling, samples were taken for final analysis. The measurement results can be read from Table 5 below. Table 5: Results of removing halogens and other volatile components from steel mill dust using appropriate heat treatment and controlled oxidation conditions. [Table 5]

[0085] The measurement results show a significant increase in zinc content in both cases. This is due to the removal of halogens and other volatile components.

[0086] In contrast, precise heat treatment under controlled oxidation conditions can significantly reduce chlorine and fluorine content. Furthermore, remarkable removal of elements such as lead, cadmium, potassium, and sodium is demonstrated.

[0087] Therefore, by using the method according to the present invention for removing halogens and other volatile components from steel mill dust by precise heat treatment under controlled oxidation conditions, it is possible to remove most impurities, particularly Cl, F, Cd, Pb, K, and Na, from steel mill dust and other metal-containing dust. These elements are the main cause of the low quality of zinc oxide in currently established steel mill dust recycling methods. Thus, it is possible to obtain high-purity zinc oxide from steel mill dust, thereby dramatically reducing the residual material load on the primary zinc industry, and gaining additional value through possible applications in the market for high-quality zinc oxide (tire industry, ceramics, chemical industry, etc.).

[0088] As a supplement, it should be noted that "possess" does not exclude other elements or stages, and the singular form does not exclude the plural. Furthermore, it should be noted that the features or stages described with reference to one of the above embodiments may be used in combination with other features or stages of the other embodiments described above.

Claims

1. A method for producing valuable products from industrial dust, The aforementioned method, Preheat the heating device to an operating temperature of 600°C or higher, Preheating the industrial dust having at least one valuable substance and a first concentration of volatile components to a temperature of 600°C or higher in the preheated heating device, The process involves reprocessing the preheated industrial dust in the heating device, wherein the reprocessing is performed The aforementioned industrial dust is heated at a rate of 20°C or more per minute, The aforementioned industrial dust is heat-treated at a processing temperature in the range of 900°C to 1200°C for 30 minutes or more. This includes controlling and / or adjusting the oxidation conditions during the reprocessing, The reprocessing method comprises at least partially removing the volatile components from the industrial dust and providing the valuable product.

2. The method according to claim 1, wherein the valuable product comprises at least one valuable substance and a second concentration of the volatile component that is lower than the first concentration of the volatile component.

3. The method according to claim 1 or 2, wherein the valuable material has a metal oxide.

4. The method according to claim 3, wherein the valuable material comprises zinc oxide and / or copper oxide.

5. The method according to any one of claims 1 to 4, wherein the industrial dust is substantially in the form of dust particles.

6. The method according to claim 5, wherein the dust particles include dust from a steel mill or dust from the copper industry.

7. The method according to claim 5 or 6, further comprising providing the industrial dust, wherein the dust particles of the industrial dust are aggregated.

8. The method according to claim 7, wherein the reprocessing is performed in a batch manner.

9. The method according to claim 7 or 8, further comprising drying the industrial dust.

10. The method according to any one of claims 1 to 9, wherein the heat treatment further comprises controlling and / or adjusting the water vapor in the heated atmosphere so that a water vapor partial pressure of 0.1 bar or more exists.

11. The method according to any one of claims 1 to 10, wherein the heat treatment further comprises mixing the industrial dust.

12. The method according to any one of claims 1 to 11, wherein controlling and / or adjusting the oxidation conditions includes supplying oxygen and / or air so that the combustion air ratio is in a hyperstoichiometric range of 1.1 to 1.

5.

13. The method according to any one of claims 1 to 12, wherein the industrial dust has a first concentration of the at least one valuable substance, and the reprocessing further comprises concentrating the valuable substance such that the reprocessed valuable substance product has a second concentration of the at least one valuable substance higher than the first concentration.

14. The aforementioned method has the following characteristics: To remove 90% or more of at least one of the group consisting of chlorine, lead, and cadmium from the aforementioned industrial dust. To remove 80% or more of fluorine and / or potassium from the aforementioned industrial dust, The method according to any one of claims 1 to 13, comprising at least one of removing 45% or more of sodium from the industrial dust.

15. The method according to any one of claims 1 to 14, wherein heating the industrial dust is carried out at a rate of 30°C per minute or more.

16. The method according to any one of claims 1 to 15, wherein the heat treatment of the industrial dust by the heating device is performed for 60 minutes or more.

17. A method for providing a metal oxide, Using a valuable product manufactured by the method described in any one of claims 1 to 16, A method comprising further reprocessing the valuable product in order to provide a high-purity metal oxide and / or secondary metal oxide.

18. The method according to claim 17, wherein the metal oxide is zinc oxide and / or copper oxide.

19. The method according to claim 17 or 18, wherein the further reprocessing of the valuable product is performed without electrolysis.

20. The method according to any one of claims 1 to 16, wherein the valuable product comprises zinc oxide and at least one of the following characteristics: a fluorine concentration of 0.2 weight percent or less, a halogen concentration of 2 weight percent or less, a lead concentration of 1 weight percent or less, a cadmium concentration of 0.05 weight percent or less, and a volatile component concentration of 5 weight percent or less.

21. The method according to claim 20, wherein the valuable product comprises dust particles that are substantially aggregated.

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