Improved Plasma Induced Fuming Furnace

Abstract

A single-chamber furnace for fuming vaporizable metals or metal compounds from a metallurgical charge is disclosed, comprising a bath furnace for receiving the molten charge up to a predetermined height, the furnace equipped with a non-transfer plasma torch for generating a plasma and a first submerged injector for injecting the plasma below the predetermined height, the furnace further comprising a post-combustion zone for forming an oxidized form of at least one vaporizable metal or metal compound and a recovery zone for recovering the oxidized form from gases formed in the post-combustion zone, the furnace further equipped with a second submerged injector for injecting additional gas into the furnace below the predetermined height. Use of the furnace and a method for fuming vaporizable metals or metal compounds from a metallurgical charge are also disclosed.

Description

Technical Field

[0001] The present invention relates to the field of pyrometallurgical (high-temperature metallurgy) recovery of non-ferrous metals such as copper, lead, tin, and zinc from primary and / or secondary feedstocks, also known as reusable materials, or combinations thereof. More particularly, the present invention relates to the recovery of volatile metals such as zinc and lead from molten slag and / or metal baths by a process step commonly referred to as fuming.

Background Art

[0002] Methods for producing non-ferrous metals such as copper, nickel, lead, tin, and zinc typically include at least one, usually multiple, pyrometallurgical process steps in which both the metal and the metal oxide are in a liquid molten state, where the metal oxide can be separated by gravity as a separated and low-density liquid slag phase from a higher-density molten metal phase. If the slag phase is poor in valuable metals, the slag phase is usually withdrawn from the process as a separate stream, and this separation can lead to the production of a by-product, also known as slag, "end slag" or "final slag" as a by-product from metal production.

[0003] Patent Documents 1 and 2 disclose a two-stage smelting reduction method for producing molten iron from raw materials containing iron oxide. The raw materials are first processed through a melting reactor and subsequently through a smelting reduction reactor. The atmospheres in the two reactors remain strictly separated, so that strong reduction conditions may be maintained in the smelting reduction reactor to increase the yield of reduction to the liquid iron melt, while more neutral conditions may be maintained in the melting reactor so that the combustion energy from the combustion of carbon-containing substances can be utilized better. The smelting reduction reactor is heated by an immersion type plasma generator, and the reducing atmosphere is obtained by the addition of a reducing agent such as coal or petroleum coke. This reaction produces a combustible gas mixture containing CO and / or H2, and typically low contents of CO2 and H2O. After washing the impurities, this gas mixture mainly contains CO and / or H2 and is partially reused to the plasma generator that heats the smelting reduction reactor. The remainder of the gas mixture is used for heating the melting reactor by further combustion, by another immersion type plasma generator, and / or by injecting a mixture of an oxygen-containing gas and a combustible gas into a tuyere below the surface of the melting furnace contents. Any sulfur in the iron-containing raw materials is typically removed either into the gas of the reactor or as part of the matte phase in the melting reactor. Copper present in the raw materials is typically removed as metal and / or matte copper at the bottom of the melting reactor. This method can have a much lower CO2 emission than the conventional blast furnace method. Patent Documents 1 and 2 do not describe any stripping (removal) or fuming of evaporable metals or metal compounds, and the described facilities are not provided for their recovery as separate products. Therefore, the described furnaces are not suitable for the fuming of evaporable metals or metal compounds from metallurgical charges.

[0004] Patent Document 3 discloses a simple method for producing ferrochrome from chromite ore for producing metals and / or for producing slag. The finely powdered oxide ore, optionally together with a slag former, is processed in a single-chamber reactor comprising three zones: an upper oxidation zone where the material is preheated and melted by the combustion of carbon monoxide and hydrogen gas that optionally rises from the lower intermediate zone by an oxygen-containing gas; an intermediate zone consisting of a slag bath where the heated and optionally melted oxide material is at least partially reduced by the simultaneous injection of a carbonaceous material and / or a material containing hydrocarbons and thermal energy mainly supplied through a plasma generator; and a lower zone at the bottom of the reactor where the metal formed during the reduction process sinks and from where the metal product and slag by-products can be removed. The oxygen-containing gas introduced into the intermediate zone is 99.5% by weight pure oxygen. The oxygen addition is controlled to generate sufficient energy to preheat and melt the ore and additives added into the chamber, which is carried out in a more oxidizing atmosphere that dominates the intermediate and upper zones of the chamber reactor. The energy supplied through the plasma generator is controlled to drive the endothermic reaction between the slag and carbon under the reducing atmosphere that dominates the lower part of the chamber reactor. Most of the exhaust gas from the furnace is processed for H2O and CO2 removal and returned to the furnace as feed gas for the plasma generator. The remainder of the exhaust gas is removed from this process for use as fuel. Patent Document 3 does not describe any stripping or fuming of evaporable metals or metal compounds, and the described equipment is not provided for its recovery as a separate product. The mass balance in Figure 2 demonstrates that no gases other than the plasma gas and oxygen gas are introduced into the furnace. This furnace is also not suitable for the fuming of evaporable metals or metal compounds from metallurgical charges.

[0005] Patent Document 4 describes a single bath furnace for smelting metallurgical charges and separating metals under flexible redox conditions. The furnace is equipped with a 3 MW plasma torch or burner, and in addition, a conventional so-called "oxy-gas" burner with a power of 1.5 MW is also provided. This device enables the execution of oxidation and reduction processes in the same furnace. This document proposes using the oxy-gas mode for smelting and / or operating under mild reduction or any oxidation conditions in the smelting furnace, and using the plasma mode for operation under high reduction conditions. When a very high energy input is required, the two heating technologies may be executed simultaneously.

[0006] The final slag taken from dry metallurgical processes for producing non-ferrous metals is typically cooled, granulated and sized, and may be used in concrete production as an alternative to rock and gravel or as an aggregate in road construction. When crushed, the slag can also be of interest for use as blast sand or blast grit.

[0007] Some of the substances that can be found in slag products known in the art are considered potentially harmful to the environment. Primarily lead, but to some extent zinc as well, are major examples of such undesirable substances. Both zinc and lead are metals that can be at least partially present in a leachable form from slag, and their presence at significant levels can prevent the use of many slag products, especially in more economically attractive applications, and can make the disposal of such slag in landfills much more complex and difficult, and typically, it needs to be considered as "hazardous waste". The allowability of use in specific applications is often determined by testing the leaching behavior of the slag. Typically, elements such as Pb and Zn tend to leach more, and certain slags can fail such acceptability tests.

[0008] In addition, the Applicants have found that zinc levels of approximately 5 wt% or more in the slag significantly retard the hardening of other construction compositions such as concrete and cement when the slag is used in such construction compositions. This effect on the hardening rate represents an impediment to the use of slag containing significant amounts of Zn as a cementitious material and / or as an aggregate in concrete or cement.

[0009] For at least some of the above reasons, non-ferrous metal producers have often attempted to reduce the level of zinc in the slag by-products and also, if present, the level of lead, often by means of a so-called "fuming" process.

[0010] Michael Borell described, during "Securing the Future" of the International Conference on Mining and the Environmental Metals and Energy Recovery, held in Skellefteå, Sweden in 2005 (pages 130 - 138 of the proceedings), in "Slag - a resource in the sustainable society", a batch process step that can reduce the zinc content in copper smelting slag (and additional zinc recycling materials) to up to 1.2% by weight by treating the liquid slag from an electric smelting furnace that produces copper matte with reducing gas in a slag fuming furnace also known as a "box fumer". The fumed slag is further washed in a settling furnace where the remaining droplets of copper alloy and copper sulfide are separated into a heavier liquid phase given some residence time before the slag can be granulated, dewatered, and sold for road construction purposes and blasting. The reducing gas for the fumer is obtained by carefully mixing pulverized coal with primary air injected into the furnace. The problem with this type of fuming is that the reaction between coal and air must remain mainly limited to producing carbon monoxide in order to maintain reducing conditions, and thus most of the heat of reaction, i.e., the part produced by the continuous reaction of oxidizing carbon monoxide to carbon dioxide, remains unavailable in the furnace core to drive endothermic reactions such as the reduction of metal oxides like zinc oxide to elemental metals that can be removed from the liquid bath. Another drawback of the box fumer is the large amount of furnace exhaust gas that is produced and needs to be cooled, filtered, and treated for the recovery of fumed metals and purification before release to the atmosphere.

[0011] Patent Document 5 discloses a method for recovering metals from a batch of liquid slag in metallic or sulfide form by reduction with a carbonaceous reducing agent, maintaining the temperature, and the thermal energy required to carry out the reduction and sulfidation is provided by blowing preheated gas in a plasma generator below the surface of the slag bath. The vapor of the volatile metal is condensed in a condenser and recovered as liquid metal. The non-volatile metals and sulfides formed are collected in the form of molten droplets that settle out of the slag. In order to enable the condensation of the volatile metal in the condenser as the liquid metal product, it is necessary to always maintain the reduction conditions throughout the process as described up to the downstream of the condenser. Fumes from the furnace containing volatile metals also represent a significant safety risk. These are highly reactive and at high temperature. If air were to enter, even slightly, the fumes would self-ignite and in some cases even explode.

[0012] At the "ScanArc's Development of Plasma Based Processes for Recovery of Metals and Heat Energy from Waste and Hazardous Waste Materials" presented at the International Workshop on Plasma Technologies for Hazardous Waste Destruction (Como, Italy, September 12 - 15, 1992), ScanArc Plasma Technologies AB proposed a non - transferred submerged plasma generator to reduce slag from the metallurgical industry by fuming, which could reduce the heavy metal content, recover metals, and produce vitrified non - leaching slag. The plasma generator operates on most gases at any selected oxygen potential, can generate a very high available enthalpy while keeping the gas flow relatively low even with dilute gas mixtures, thus offering a great flexibility advantage. S.O. Santen was at the 21st McMaster Symposium on Iron and Steel, held at McMaster University in Hamilton, Ontario, Canada from May 11 - 13, 1993, the 21 stAt the "Pretreatment and Reclamation of Dusts, Sludges and Scales" in the McMaster Symposium on Iron and Steelmaking, a very similar presentation was made. This technology was commercially applied by Energy Recycling AS (ERAS) at the site of Hoyanger Sink Gjenvinning AS in Norway, especially as evidenced by the environmental permit requirements of "Recovering of Metal Values from EAF Dust by the Arcflashfuming Process", which was filed on October 10, 2002 and published approximately two weeks before the public hearing held on October 31, 2002 for the subject. This requirement is also very detailed about the method itself, the flux components, the composition of raw materials and products including the so-called slag formers, the operating parameters, and the equipment design.

[0013] Patent Document 6 also describes such a fuming reactor for treating Zn-containing residues using an immersion-type plasma firing tuyere attached to a plasma torch as its heat and gas source. Patent Document 7 describes a method for Zn fuming using an immersion-type plasma torch that generates an oxidizing gas mixture, where a solid reducing agent is supplied to the melt.

[0014] Patent Document 8 describes the smelting and fuming of metallurgical charges using a jet of hot gas from an immersion-type plasma torch, whereby the generated hot gas (more precisely, "plasma") has an enthalpy of at least 200 MJ / kmol. Patent Document 9 describes a method for fuming zinc from metallurgical slag using an immersion-type plasma torch, whereby the zinc content of the produced slag is at most 1.00 wt%, and the clean slag has the advantage of quickly hardening when used as an active binder in a 50 / 50 mixture with sodium silicate for making tiles after the slag is finely ground.

[0015] The furnaces for plasma fuming described in the above literature use only plasma generators as their heat sources, i.e., burners that generate extremely high temperatures by consuming energy sources that are quite expensive in many countries.

[0016] However, the present applicants have found that the gas flow that can be generated by an industrial-scale plasma generator remains limited in order to operate and maintain a stable electric arc and to keep the enthalpy amount of the hot gas from the plasma generator high enough to form the desired plasma. This will be explained in more detail herein. Therefore, there is a limit to the amount of stripping gas that can be made available by the plasma generator for stripping the evaporable substance from the liquid bath in the furnace. This also limits the agitation that the gas injected from the plasma generator can cause in the liquid bath contained in the furnace.

[0017] In slag fuming, strong reducing conditions are preferred since it may be necessary to reduce oxides of zinc and other evaporable metals to their respective elemental forms for the metals to become evaporable. The strong reducing conditions can be obtained by adding at least one reducing agent, preferably a solid reducing agent, preferably carbon, which may be a gas, liquid, solid, or a combination thereof, and this may be added to the hot plasma gas injected into the furnace. However, this method of introducing an additional reducing agent remains limited since the amount of plasma gas available per plasma generator is small. Then, additional reducing agent can be added to the furnace, preferably a solid reducing agent, by dripping it onto the bath surface through the furnace filling opening.

[0018] However, this additional method for introducing an additional reducing agent leaves something to be desired.

[0019] Gaseous reducing agents such as natural gas cannot be introduced through the furnace filling opening by this addition method because the gaseous reducing agent needs to move against the flow of the furnace exhaust gas and thus cannot reach the liquid bath that is considered to provide reduction activity. The injection of liquid reducing agents such as fuel oil is also not very preferable because its evaporation causes a high volume expansion, which causes foaming and scattering in the furnace, and a part of the reducing agent can be entrained in the exhaust gas before it can perform its intended function. Therefore, the choice of suitable reducing agents is very limited.

[0020] Conventionally, additional reducing agents added through the filling and outlet openings at the top of the furnace have to move downward through the gas space at the top of the furnace before they can reach the liquid surface. Just before the furnace gas enters the exhaust pipe, typically additional air is introduced to oxidize the evaporated elemental metals or metal compounds to their corresponding metal oxides. The oxides have much higher boiling and melting points than the corresponding metals. The formed oxides easily appear as entrained flue gas dust and can be recovered further downstream in the furnace exhaust gas system. Therefore, during its movement through the top of the furnace, the additional reducing agent is brought into contact with air, and at the high temperature in the furnace, at least a part of the reducing agent can be easily oxidized before the remaining part can reach the liquid bath surface. The heat generated by this oxidation also does not reach the liquid bath and remains with the exhaust gas. This heat is not beneficial and is an extra burden on the exhaust gas treatment system.

[0021] Additional reducing agents that can reach the liquid bath surface cannot perform their functions properly if they are not well mixed in the liquid bath. However, the gas flow available from the plasma generator does not cause very intense bath agitation.

[0022] The additional reducing agent must also be able to move downward through the furnace gas space against the rising flow of the stripping gas before it can reach the surface of the liquid bath. Therefore, the size of the particles or droplets of the solid or liquid reducing agent must be high enough so that the particles and / or droplets are not overly entrained into the exhaust gas treatment system with the stripping gas. However, large particles have a limited surface area per unit mass and are thus less reactive when mixed into the liquid bath. Most reducing agents, such as solid carbon, have a much lower density than the liquid bath in the furnace. Larger particles exhibit a higher buoyancy and thus have a greater tendency to float on top of the liquid bath, further reducing the contact surface between the solid reducing agent and the liquid bath.

[0023] Therefore, this additional method for adding an additional reducing agent suffers from a significant lack of efficiency and effectiveness.

[0024] Therefore, the plasma generation fuming methods and furnaces well-known in the art leave something to be desired. In particular, there is still a need for improved plasma-driven fuming methods and apparatuses that provide increased fuming rates with more bath agitation and / or more fuming gas, as well as the possibility of introducing additional reducing agents in a more efficient and effective manner.

Prior Art Documents

Patent Documents

[0025]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Patent Document 9

SUMMARY OF THE INVENTION

[0026] The object of the present invention is to avoid or at least mitigate the above problems and / or generally provide an improvement.

[0027] According to the present invention, there is provided an apparatus and a method as defined in any of the appended claims.

[0028] In one embodiment, the present invention provides a single-chamber furnace or apparatus for fuming at least one evaporable metal or metal compound from a metallurgical charge comprising a bath furnace capable of containing a molten charge up to a determined height, the furnace comprising at least one non-transfer type plasma torch for generating a first hot gas which is plasma quality, and at least one first submerged injector for injecting the first hot gas from the plasma torch below a determined height, the furnace further comprising a post-combustion zone for oxidizing at least one evaporable metal or metal compound in the fuming gas to form an oxidized form of the at least one evaporable metal or metal compound, and a recovery zone for recovering the oxidized form of the at least one evaporable metal or metal compound from the gas formed in the post-combustion zone, the furnace further comprising at least one second submerged injector different from the first submerged injector for injecting additional gas into the furnace below a determined height.

[0029] In another embodiment, the present invention provides a method for fuming at least one evaporable metal or metal compound from a metallurgical charge using a furnace or apparatus according to the present invention, the method comprising the following steps: · Introducing a metallurgical charge containing at least one evaporable metal or metal compound into a furnace to form a bath of the molten charge up to a determined height; · Using plasma quality hot gas from at least one plasma torch and at least one reducing agent to fume a quantity of at least one evaporable metal or metal compound from the bath, thereby producing a fuming gas containing the evaporable metal or metal compound; · Post-combusting the fuming gas in a post-combustion zone to oxidize at least one evaporable metal or metal compound to its oxidized form; · Extracting the gas formed in the furnace from the furnace and recovering the oxidized form of at least one evaporable metal or metal compound from the gas formed in the post-combustion step; comprising; During at least part of the fuming step, additional gas is injected below a determined height in the bath by at least one second injector, thereby increasing the amount of fume containing the evaporable metal or metal compound.

[0030] The term metallurgical charge in the context of the present invention represents a wide family of compositions that can occur at any time as the furnace contents or furnace charge, or as part thereof, during the dry metallurgical process stage, preferably as part of a non-ferrous metal production method.

[0031] Preferably, the metallurgical charge is a first slag, and the product obtained from the method according to the present invention is a second slag having a reduced content of at least one evaporable metal or metal compound compared to the content of the same evaporable metal or metal compound in the first slag.

[0032] In another embodiment, the present invention provides the use of a furnace according to the present invention for fuming at least one evaporable metal or metal compound from a metallurgical charge.

[0033] The present applicants have found that the fuming of evaporable metals or metal compounds from metallurgical charges, using a first hot gas of plasma quality from a plasma torch where the fuming process is injected into the melt bath by a first immersion type injector, can be significantly improved by injecting additional gas into the melt bath via at least one second immersion type injector.

[0034] The present applicants have found that the additional gas introduced through the additional immersion type injector provides an additional injection point and additional gas volume for stripping evaporable metals or metal compounds from the molten metallurgical charge. The present applicants have found that with only the volume of plasma or hot gas from a plasma torch available for stripping zinc from copper smelter slag, the zinc concentration in the bubbles rising through the molten slag bath can reach a high value of up to 40 mol%. In the best case, the equilibrium can reach the zinc fuming reaction (I), so ZnO + C → Zn(g) + CO(g) (I) Despite the favorable equilibrium constant enjoyed by the process at the very high temperature of the plasma quality hot gas from the plasma torch, the high Zn level in the bubbles results in a significant amount of zinc oxide still remaining in the liquid bath. The present applicants have found that this concentration in the gas phase can be significantly reduced by the present invention, due to the additional gas made available for stripping via the additional injector and furthermore due to the increased presence of a reducing agent throughout the liquid bath that enables the achievement. Since the amount of hot gas that can be generated by the plasma torch is limited, the present applicants have found that it is advantageous to inject additional gas into the melt bath, and particularly advantageous for the reason of injection via at least one second immersion type injector different from the first immersion type injector.

[0035] Accordingly, another advantage of the present invention is also that the present invention provides at least one further immersion-type gas injection point into the melt bath. This improves the mixing within the bath, resulting in a more uniform distribution of temperature and any reducing agent that can be introduced into the furnace, thus promoting the ongoing chemical reactions and obtaining a more uniform distribution of the reduced metal or metal compound formed by the reaction with the reducing agent, and the advantage of additional agitation of the melt bath inside the furnace is obtained. Accordingly, the additional immersion-type gas injection points also result in an improvement in the fuming operation through these actions.

[0036] Yet another advantage of the present invention is to provide at least one additional means for further introducing a reducing agent into the melt bath inside the furnace. Since at least one second injector is also an immersion-type injector, this additional means also provides a wider selection of suitable reducing agents compared to adding large-particle solids and / or liquid reducing agents through the charge and outlet openings at the top of the furnace. With conventional means, any coke particles falling into the furnace through the charge opening should preferably have an average particle size in the range of at least 6 mm, such that most of the particles fall into the furnace and the entrainment of particles with the exhaust gas exiting the furnace through the same opening remains limited. The second immersion-type injector provides a much wider selection of suitable reducing agents. The reducing agent introduced through the second immersion-type injector may be a gas, liquid, solid, or a combination thereof. If it is a solid, the reducing agent may have a much finer particle size analysis, thereby obtaining the additional advantages of a high surface / volume ratio and a higher contact area, and thus a higher reactivity when the reducing agent contacts the melt bath inside the furnace. The immersion introduction of the reducing agent also provides the advantage of closer contact between the reducing agent and the bath. This advantage applies to all physical states of the reducing agent, but is particularly noticeable when the reducing agent is a solid, especially a finely divided solid.

[0037] Accordingly, the present invention achieves more than providing more stripping gas for stripping volatile metals or metal compounds from metallurgical chargers. A further effect is the additional bath stirring which results in a further uniformity of the bath inside the furnace, and another additional advantage is the possibility of injecting more and optionally also different and more effective reducing agents in a more efficient way. These additional effects contribute to a further improvement of the fuming due to the improved conditions favorable for the intended chemical reactions.

Embodiments for Carrying Out the Invention

[0038] The present invention will be described hereinafter in specific embodiments with reference to specific drawings, but the present invention is not limited thereto and is limited only by the claims. All the drawings described are only schematic and non-limiting. In the drawings, the sizes of some elements are exaggerated and may not be drawn to scale for illustrative purposes. The dimensions and relative dimensions in the drawings do not necessarily correspond to the actual implementation of the present invention.

[0039] Furthermore, terms such as first, second, and third in this specification and the claims are used to distinguish similar elements and are not necessarily for describing a sequential or chronological order. These terms are interchangeable under appropriate circumstances, and the embodiments of the present invention can operate in an order other than those described and / or illustrated in this specification.

[0040] Furthermore, terms such as upper, lower, above, and below in this specification and the claims are used for illustrative purposes and are not necessarily for describing relative positions. Such terms are interchangeable under appropriate circumstances, and the embodiments of the present invention described in this specification may operate in an orientation other than those described or illustrated in this specification.

[0041] The term "comprising" as used in the claims should not be construed as being limited to the elements recited in connection therewith. It does not exclude the presence of other elements or steps. These features, integers, steps, or components should be considered as provided if necessary, but do not exclude the presence or addition of one or more other features, integers, steps, or components, or groups thereof. Thus, the volume of an "article comprising means A and B" need not be limited to an object consisting only of agents A and B. This means that A and B are the only elements of interest for the subject matter related to the present invention. According to this, the terms "comprise" or "embed" also encompass the more restrictive terms "consisting essentially of" and "consist of". Thus, by replacing "comprise" or "include" with "consist of", these terms represent the criteria for preferred but limited embodiments, which are also provided as part of the content of this specification regarding the present invention.

[0042] Unless otherwise specified, all ranges provided in this specification include the given endpoints, and the values of the components or constituents of a composition are expressed as weight percentages or % by weight of each component in the composition.

[0043] As used herein, "weight percent", "wt-%", "percent by weight", "% by weight", "ppm wt", "ppm by weight", "weight ppm", or "ppm", and variations thereof, refer to the concentration of a substance, unless otherwise specified, obtained by dividing the weight of the substance by the total weight of the composition and multiplying by 100 or 1,000,000 as appropriate. It is understood that as used herein, "percent" and "%" are intended to be synonymous with "weight percent", "wt-%", etc.

[0044] It should be noted that as used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, a reference to "a composition" containing "a compound" includes compositions having two or more compounds. Also, it should be noted that the term "or" is generally used in the sense of "and / or" unless the context clearly dictates otherwise.

[0045] Moreover, each compound used herein may be discussed interchangeably with respect to its chemical formula, chemical name, abbreviation, etc.

[0046] Plasma is regarded as the fourth state of matter following solids, liquids, and gases, by a special category on the high-energy side. As the temperature of a gas increases, at least some of the atoms separate into ions and electrons, forming an ionized gas. This is "plasma", which may be referred to as "hot plasma gas" or simply "hot gas" by other sources. The ionization of the atoms may be partial or complete, and thus the transition from gas to plasma is rather gradual. One distinct characteristic of plasma is that ionization needs to be sustained, which implies high temperature.

[0047] In a non-transfer type plasma arc torch, the plasma arc is generated between two electrodes within the torch body through which a gas that is converted into plasma by the energy dissipated by an electric arc flows. The non-transfer type plasma torch is placed within a metal container where the material to be processed is electrically grounded and acts as the anode. Thus, the reaction material is in contrast to the transfer type plasma which must be a conductive material. In the transfer type plasma, the anode may be made of carbon. However, the carbon electrode has the drawback of significantly reducing the versatility of the equipment regarding the fuming method by fixing the reduction conditions.

[0048] To obtain plasma, the enthalpy amount of the plasma gas generated by a plasma generator should be at least 1 kWh / Nm 3 or more. Thus, the plasma quality hot gas has an enthalpy amount of at least 1 kWh / Nm 3 or more. Plasma torches known in the art may have an output of up to 5 MW or even 7 MW. A more typical plasma torch generates about 3 MW, which means it may not be able to generate plasma quality hot gas exceeding 3000 Nm 3 / h. A more typical operating regime generates plasma with an enthalpy amount in the range of 3.5 - 5.5 kWh / Nm 3 which means a 3 MW plasma torch typically generates plasma quality hot gas in the range of 600 - 800 Nm 3 / h. Thus, a plasma torch with a specific power cannot generate plasma quality hot gas exceeding the corresponding volume.

[0049] In the context of a plasma torch, the specified gas volume occupies only the volume of the gas supplied to the plasma torch and at standard / normal conditions. The volume specified in the context of the present invention for the volume of the plasma quality hot gas generated by a plasma generator (PG) includes only the gas that has passed through the PG itself, i.e., what is referred to as the "primary gas" or "primary volume of gas". Thus, these do not consider any additional gas that may be further directly supplied to the downstream tuyere, which is called the "secondary volume of gas" in the context of the present invention, and which is usually mixed with the plasma quality hot gas coming from the plasma generator and sprayed together into the bath. After this mixing, the amount of enthalpy per unit volume may no longer conform to the lower limit specified elsewhere in this specification for such a gas, so there is a sufficient possibility that the mixed gas no longer conforms to the modifier "plasma quality". All these gas volume numbers are expressed in the "standard" state. Thus, these also do not consider any volume changes that may occur due to temperature changes, pressure, chemical reactions, or phase changes that may occur at the plasma generator or its downstream tuyere.

[0050] An immersion injector means a connecting pipe or tuyere between a gas source and an injection point located below the bath level in the furnace or a determined liquid level, and thus is in an immersed position or a position intended to be immersed during operation. This ensures a more direct and concentrated contact between the gas and the molten mass.

[0051] The tuyere or injector is preferably made short to minimize wear and breakage. This also ensures low heat loss. The tuyere may be cooled to reduce wear and breakage under severe temperature conditions. The tuyere may be mounted horizontally through the furnace wall below the bath surface. Then, the torch or burner that can be supplied to the tuyere, whether it is plasma combustion or oxy-gas combustion, is arranged outside the furnace at an immersible (also known as "immersion type") position. Preferably, when there is a liquid bath of metallurgical charge in the furnace, these are constantly supplied with gas to avoid backflow of the molten mass to the tuyere. Otherwise, it may cause immersion of the tuyere, and in some cases, serious damage may also be caused to the tuyere and, in some cases, the torch or burner that can be supplied to the tuyere. Alternatively, the tuyere may still be at an angle of blowing into the bath, but mounted at an angle that allows the burner or torch to be above the bath surface and outside the furnace. This layout results in a slightly longer tuyere, but can also be arranged to ensure that no molten material can flow back to the burner or torch. This may not be very recommended in large furnaces, but the tuyere can also be arranged vertically. The tuyere for injecting additional gas may be arranged in the same way, that is, immersed vertically with respect to the furnace wall or at an angle different from the furnace wall and penetrate the furnace wall.

[0052] A non-transfer type plasma torch means a hot gas generator using a plasma torch, in which an electric arc is maintained between the electrodes inside the torch unit. The gas enters the vented ionization box through the input port, where the electric arc is maintained. The gas is heated to an extreme temperature and discharged as a plasma-quality hot gas that is at least partially plasma through the output port.

[0053] Between the plasma torch and the injection point into the furnace, additional substances such as sheath gas or dilution gas can be added to the flow from the torch to the injection point. In the context of the present invention, the amount of hot gas generated by the plasma torch includes only the primary gas passing through the plasma generator, and does not include secondary gas addition such as any additional gas or other substances that can be added between the plasma torch itself and the injection point or tuyere where the first hot gas of the plasma quality from the plasma torch is injected into the furnace.

[0054] An oxy-gas burner means a hot gas generator that mixes and burns a carbon-containing fuel and an oxygen-containing gas. In order to easily reach the high temperature required for the proper functioning of the oxy-gas burner, the oxygen-containing gas is preferably substantially pure oxygen rich in oxygen and more preferably having a low level of inert components. This not only results in a higher flame temperature but also reduces the amount of inert gas that needs to be carried and processed by the furnace exhaust gas system. The mixing zone of the oxy-gas burner is inside the burner unit, while the combustion zone of the oxy-gas burner may be inside or outside the burner unit.

[0055] The metallurgical charge in the context of the present invention can be any composition that can occur in a liquid molten state in the dry metallurgical process steps for producing non-ferrous metals. Thus, the metallurgical charge may be, by way of example, a molten metal composition containing at least one non-ferrous metal, but may also be a molten slag phase that occurs in such process steps. The metallurgical charge may be in the form of a molten liquid, but alternatively may have any kind of solid form. For example, the charge may be in the form of an aggregate obtained by cooling or granulating the liquid molten phase from the furnace in which the dry metallurgical process steps are being carried out.

[0056] Metallurgical slag is usually not a pure substance but a mixture of many different components. As a result, metallurgical slag does not have a distinct melting temperature. In the art, it has become common to use the term "liquidus temperature", which is the temperature at which the slag is completely liquid.

[0057] As described in the Background section, "fuming" is an operation that has been commercially used in the field of pyrometallurgy since around 1960. Those skilled in the art are well aware that specific metals or metal compounds can be evaporated from a metallurgical charge by stripping with a gas, also called "fuming", which is at a pressure close to atmospheric pressure and thus does not require the deep vacuum needed to distill lead from tin. This ability is due to the vapor pressure of the evaporable metal or metal compound being much higher than that of most of the other compounds in the charge. Thus, such compounds are considered "evaporable" from a metallurgical charge in the art and are referred to as "evaporable".

[0058] A well-known example is the fuming of zinc from other pyrometallurgical compositions. This fuming of zinc can also be carried out as part of another pyrometallurgical process, such as the removal of zinc (usually a portion thereof) via the exhaust vapors generated during the copper smelting or copper refining process. Although less frequently, fuming may be carried out as a separate process step, such as in a "Box fumer" as described by, for example, Michael Borell or the author of ScanArc mentioned above. Also, as described above, when the metallurgical charge is slag, zinc may be present in the charge mainly as its non-volatile oxide ZnO, and as a result, it is necessary to enable fuming by first reducing the oxide to an elemental metal or a compound that can be stripped by fuming. Another example is the recovery of lead and tin as their oxides by the volatilization of lead and tin during the recovery of copper from copper-containing scrap, as discussed in the Background section of U.S. Patent No. 3,682,623. Also, elements such as bismuth, indium, and / or germanium are known to have metal compounds that are either evaporable metals or are evaporable in the context of the present invention. Evaporable metal compounds can be the corresponding oxides, chlorides, and / or sulfides.

[0059] Unless otherwise specified in this specification, the amounts of metals and oxides are expressed according to typical practices in pyrometallurgy (dry smelting). The presence of each metal is typically represented by its total presence, regardless of whether the metal exists in its elemental form (oxidation state = 0) or in any chemically bonded form, typically an oxidized form (oxidation state > 0). For metals that can be relatively easily reduced to their elemental forms and often occur as molten metals in pyrometallurgical processes, it is very common to represent their presence in their elemental metal forms even when the composition of the slag is given, where most of such metals may actually exist in oxidized forms. Therefore, the composition of slags such as the slag according to the present invention specifies the contents of Fe, Zn, Pb, Cu, Sb, and Bi as elemental metals. Base metals are more difficult to reduce under non-ferrous pyrometallurgical conditions and mainly occur in oxidized forms. These metals are typically represented by their most common oxide forms. Therefore, the slag composition typically gives the contents of Si, Ca, Al, and Na, represented as SiO2, CaO, Al2O3, and Na2O, respectively.

[0060] Since the oxygen in the slag bound to the more noble metals is not reflected in the composition that provides only the content of elemental metals, the slag compositions reported according to this method often do not approach 100% by weight in total.

[0061] In one embodiment of the apparatus or furnace according to the present invention, the apparatus has a plasma torch that has at least 3.5 kWh / Nm expressed in volume units under standard conditions 3When supplying (generating) a plasma having an enthalpy amount, the total amount of additional gas that is at least 10%, preferably at least 15%, more preferably at least 20%, 25%, 30%, 35%, 40%, 45%, 50%, or 55%, more preferably at least 60%, preferably at least 70%, more preferably at least 75%, 80%, 90%, 100%, 110%, 120%, 125%, 130%, 140%, 150%, 175%, 200%, 225%, and even more preferably at least 230% of the amount of hot gas of plasma quality that can be generated by a single element of at least one plasma torch having a maximum power rating is equipped to be injected through at least one second injector. Optionally, the apparatus has a plasma torch that is at least 3.5 kWh / Nm expressed in volume units under standard conditions 3When supplying a plasma having an enthalpy amount, the total amount of additional gas is equipped to be injected through at least one second injector, which is up to 500%, preferably up to 450%, more preferably up to 400%, 350%, 325%, 300%, 290%, 280%, 275%, 270%, 265%, 260%, 250%, 240%, 230%, 220%, 210%, 200%, 180%, 165%, 150%, 135%, 120%, 110%, 100%, 90%, 80%, 70%, 60%, 50%, 40%, 30%, and even more preferably up to 20% of the amount of plasma that can be generated by a single element of at least one plasma torch having a maximum power rating. The Applicants have found that, particularly when the additional gas stream is used as a carrier for an additional reducing agent, especially when fine powders such as coal powder or petroleum coke dust are used as the additional reducing agent, the main advantages of the present invention can already be achieved by injecting an amount of additional gas stream close to the specified lower limit through the second injector. The Applicants have found that the advantages of the present invention generally described in the above summary section can be further improved when the amount of additional gas further increases. However, the Applicants also preferably consider complying with the specified upper limit in order to reduce the risk of the liquid bath splashing and foaming, to reduce vibrations and other types of dynamic stresses on the tuyere and the rest of the furnace structure, and to reduce the amount of gas that needs to be processed through the downstream of the furnace top, such as the post-combustion zone and the recovery zone.

[0062] In the post-combustion zone of the furnace or apparatus according to the present invention, at least one evaporable metal or metal compound in the fuming gas is oxidized to form an oxidized form of at least one evaporable metal or metal compound. The purpose of this step is to reduce the safety hazard presented by the fuming gas and to enable easier recovery of metals from the fuming gas.

[0063] The fuming gas formed at the top of the furnace poses a safety hazard. This gas is very hot. The evaporated metal or metal compound contained in the gas typically exhibits a reduced form of the metal and is therefore highly reactive even when exposed to oxidation conditions such as contact with oxygen. Thus, the fuming gas formed at the top of the furnace presents a significant safety risk. Any oxygen that enters the facility in an uncontrolled manner and comes into contact with the fuming gas from the furnace, for example, oxygen as part of the ambient air that can be drawn into the exhaust treatment section of the apparatus at the top of the furnace or downstream of the furnace, readily reacts with and oxidizes the evaporated metal or metal compound, and this reaction is highly exothermic. For example, under conditions of insufficient control such as in zones with low mixing and / or particularly relatively stagnant zones, such a combination of hot gas and oxygen can cause uncontrolled combustion and in some cases even a gas cloud explosion.

[0064] In a stable and relatively fast flow of the gas and with good mixing, such a combination of the gas with air or another oxygen gas source by known entry can produce a stable and well-controlled flame front. Thus, as part of the present invention, the Applicants provide a post-combustion zone in which the hot gas from the top of the fuming furnace is drawn in, forms a stable and relatively fast flow, and is intensively mixed with oxygen such that the state of the gas mixture changes from reduction to oxidation. As a result of good mixing and high temperature, a flame front is generated, the flame front is established in the gas flow drawn from the top of the furnace, and this flame front can be easily maintained in a steady state. The Applicants consider it preferable to provide this flame front in the space above the fuming furnace, thereby providing the advantage that the radiation from the stable flame front still reaches the liquid bath inside the furnace and part of the heat from the flame front can be returned to the liquid bath.

[0065] Another result of the post-combustion process or post-combustion zone is that the safety hazard presented by the hot and highly reactive gas at the top of the furnace remains limited to the gas volume upstream of the flame front.

[0066] The oxidized form of at least one evaporable metal or metal compound is most typically a metal oxide. The oxide form of the metal or metal compound is typically non-volatile and usually forms dust of fine particles incorporated into the gas stream, making them more easily recoverable therefrom.

[0067] The furnace according to the present invention further comprises a recovery zone for recovering the oxidized form of at least one evaporable metal or metal compound from the gas formed in the post-combustion zone. The method according to the present invention also includes a corresponding step of recovering the oxidized form of at least one evaporable metal or metal compound from the gas formed in the furnace and subjected to the post-combustion process.

[0068] In one embodiment of the apparatus or furnace according to the present invention, the apparatus comprises a plurality of second injectors, each injector injecting, through each second injector, an additional gas amount that is at least 10%, preferably at least 15%, more preferably at least 20%, 25%, 30%, 35%, 40%, 45%, or 50%, more preferably at least 55%, preferably at least 60%, more preferably at least 65%, even more preferably at least 70%, still more preferably at least 75%, preferably at least 80% of the amount of the first hot gas of plasma quality that can be generated by a single element of at least one plasma torch having a maximum power rating when the plasma torch supplies the first hot gas having an enthalpy amount of at least 3.5 kWh / Nm in volume units under standard conditions. Optionally, each second injector injects, through each second injector, an additional gas amount that is at least 10%, preferably at least 15%, more preferably at least 20%, 25%, 30%, 35%, 40%, 45%, or 50%, more preferably at least 55%, preferably at least 60%, more preferably at least 65%, even more preferably at least 70%, still more preferably at least 75%, preferably at least 80% of the amount of the first hot gas of plasma quality that can be generated by a single element of at least one plasma torch having a maximum power rating when the plasma torch supplies the first hot gas having an enthalpy amount of at least 3.5 kWh / Nm in volume units under standard conditions. 3 of the amount of the first hot gas of plasma quality that can be generated by a single element of at least one plasma torch having a maximum power rating when the plasma torch supplies the first hot gas having an enthalpy amount of at least 3.5 kWh / Nm in volume units under standard conditions. Optionally, each second injector injects, through each second injector, an additional gas amount that is at least 10%, preferably at least 15%, more preferably at least 20%, 25%, 30%, 35%, 40%, 45%, or 50%, more preferably at least 55%, preferably at least 60%, more preferably at least 65%, even more preferably at least 70%, still more preferably at least 75%, preferably at least 80% of the amount of the first hot gas of plasma quality that can be generated by a single element of at least one plasma torch having a maximum power rating when the plasma torch supplies the first hot gas having an enthalpy amount of at least 3.5 kWh / Nm in volume units under standard conditions. 3When supplying a plasma having an enthalpy amount, the amount of additional gas is 200% at most, preferably 190% at most, more preferably 180%, 170%, 160%, 150%, 140%, 130%, 125%, 120%, 115%, 110%, 105%, 100%, 95%, and even more preferably 90% at most of the amount of plasma quality hot gas that can be generated by a single element of at least one plasma torch having a maximum power rating. It is equipped to inject through at least one second injector.

[0069] In one embodiment of the furnace or apparatus according to the present invention, the apparatus is connected to at least one source of compressed gas and / or includes a compressor for supplying compressed gas to at least one second injector. The present applicants have found that this provides a very convenient way to supply additional gas to the furnace. The term "compressor" can be interpreted in its very broad sense and can include, for example, a gas combustion turbine that can make combustion gas available at a pressure higher than atmospheric pressure.

[0070] In one embodiment of the furnace or apparatus according to the present invention, the source of additional gas to the apparatus comprises a gas source selected from the group consisting of hydrogen, nitrogen, air, carbon dioxide, argon, neon, helium, methane, ethane, propane, butane, and combinations thereof, preferably a nitrogen or air source, more preferably an air source, and even more preferably a compressed air source. The present applicants have found that nitrogen and air, preferably compressed air, are very convenient gases as the main components of the additional gas injected into the furnace.

[0071] In one embodiment of the furnace or apparatus according to the present invention, the apparatus comprises means for heat-treating the additional gas upstream of at least one second injector in order to vary the enthalpy amount of the additional gas, preferably comprising means for heat-treating the additional gas including at least one heat exchanger. During operation, when the supply of gas to the furnace is at a temperature lower than the temperature of the liquid bath inside the furnace, the present applicants preferably consider heating the gas before it is injected by at least one second injector. Thereby, the cooling effect that the injection of the additional gas can exert on the furnace is reduced, and it becomes easier to maintain the heat balance of the entire furnace. Preferably, such heating at least partially utilizes the heat available in a system that treats the exhaust gas from the furnace.

[0072] In one embodiment of the furnace or apparatus according to the present invention, the apparatus further comprises means for introducing a reducing agent into the additional gas upstream of at least one second injector. As described in the item of the above summary, the injection of the additional gas into the furnace through at least one second injector represents an additional inlet point for adding a reducing agent into the furnace. In addition, since at least one second injector is immersed, the choice of suitable reducing agent is very wide.

[0073] In one embodiment of the furnace or apparatus according to the present invention, the reducing agent to be introduced can be selected from gases, liquids, solids, and combinations thereof. The present applicants have found that the injection of the additional gas according to the present invention is a suitable carrier for a wide range of reducing agents with respect to the volume or weight of the reducing agent that can be suitably introduced not only when the reducing agent is a gas or a liquid but also when the reducing agent is a solid. In addition, since the solid reducing agent can have a very fine particle size distribution, as a result, it provides a high surface / weight ratio and thus a high reactivity for participating in the target chemical reaction.

[0074] In one embodiment of the furnace or apparatus according to the present invention, the apparatus comprises means for controlling the lambda of the additional gas injected into the bath by the second injector. Lambda (λ) means a very convenient parameter commonly used in relation to burners and combustible fuels, particularly in internal combustion engines, and this parameter represents the ratio of the actual air-fuel ratio in the numerator to the air-fuel ratio of the same fuel in stoichiometry in the denominator. When the air / fuel mixture is stoichiometric for complete combustion, thus its lambda is 1.0. The present applicants apply this lambda parameter to all gaseous mixtures in which oxygen is present, and to other substances that can readily react with oxygen such as combustible substances, where the other substances can be gases, liquids or solids, or combinations thereof. The present applicants have found that the control of the lambda of the additional gas injected via at least one second injector is a very convenient means for controlling the atmosphere inside the furnace, whereby the atmosphere is neutral, oxidizing or reducing, and the degree of oxidation or reduction is set. The present applicants have found that the additional addition points of the reducing agent in the apparatus according to the present invention are very versatile, and the control of the lambda in the additional gas injected provides a very convenient way for controlling the oxidation-reduction conditions in the furnace and thus for manipulating the chemical reactions occurring inside the furnace. The present applicants have found that the combination of the injection of the additional gas and the injection of the hot gas from the plasma generator enables a wide range of oxidation-reduction conditions, whereby the oxidation-reduction conditions can be set substantially independently of the heat input to the furnace, unlike more conventional heating means such as using a natural gas burner.

[0075] In one embodiment of a furnace or apparatus according to the present invention, the apparatus is equipped to inject as part of the oxygen of the additional gas and the gaseous or liquid fuel, and to make the velocity of the additional gas in at least one second injector or the velocity of the additional gas at another location upstream of at least one second injector faster than the flame propagation velocity of the fuel as part of the additional gas. The Applicants have found that additional heat input to the furnace can be provided by injecting gaseous or liquid fuel as part of the additional gas, even when the additional gas is not heated or ignited and thus the fuel and oxygen have not reacted before reaching the liquid bath, and preferably when the additional gas further contains oxygen. Typically, the temperature of the liquid bath in the furnace is significantly higher than the temperature at which the fuel and oxygen in the additional gas begin to react even without an ignition source and can readily react when injected into the liquid bath. The Applicants preferably consider this embodiment because they have found that otherwise such a reaction can move upstream with respect to the direction of flow of the additional gas in the conduit upstream of at least one second injector and within the second injector itself. Such a "backfire" phenomenon can lead to the release of heat, and thus an increase in temperature, and thus wear and breakage in that conduit or injector, or an explosion of the additional gas upstream and / or inside the injector. The Applicants have found that the risk of equipment damage as a result of such heating inside or upstream of the injector can be reduced when the apparatus is equipped to enable the additional gas to reach a velocity faster than the flame propagation velocity in the additional gas at the second injector or another location upstream thereof. A further advantage is that the additional gas is injected at a lower temperature, which further reduces wear and breakage of the second injector.

[0076] In one embodiment of the furnace or apparatus according to the present invention, the apparatus is equipped to limit the amount of fuel injected such that the combustion of the fuel injected under the intended operating conditions of the furnace results in an enthalpy increase of the additional gas, whereby the temperature of the additional gas at the injection point into the bath is at most the temperature of the molten charge intended to be present in the furnace during operation. This also contributes to reducing wear and breakage of the second injector.

[0077] In one embodiment of the furnace or apparatus according to the present invention, at least one second injector directs its additional gas towards a second volume that is part of the internal space of the furnace below a predetermined height that is different from the first volume towards which at least one first injector directs a first hot gas. The Applicants have found that this feature is relevant to the present invention and improves the advantages described in the above summary section, a.o., improved bath stirring, a more homogeneous liquid bath composition, improved chemical reactions, and most certainly, improved stripping of evaporable metals or metal compounds from the liquid bath.

[0078] In one embodiment of the furnace or apparatus according to the present invention, at least one first injector is arranged on the side wall of the furnace and at least one second injector is arranged on the furnace wall opposite to at least one first injector, preferably along the horizontal outer periphery of the furnace extending at substantially the same height as at least one first injector. The Applicants have found that this configuration is very convenient and effective for obtaining the desired effects of the present invention, as described in the above summary section. At least one first injector can inject its additional gas in a direction substantially perpendicular to the side wall of the furnace. However, the Applicants preferably consider injecting the additional gas at an angle to either a lower or upper horizontal plane, as the additional gas provides additional drive for vertical circulation in the liquid bath, which improves bath stirring and also draws more reducing agent that may float at the top of the liquid bath into the majority of the liquid bath. The Applicants preferably consider the upward direction to be better as it may create a doughnut-shaped circulation path in the liquid bath.

[0079] In one embodiment of the furnace or apparatus according to the present invention, the apparatus includes at least two, preferably at least three, first injectors distributed along the horizontal outer periphery of the furnace sidewall, whereby at least one second submerged injector directs its additional gas towards a volume that is part of the internal space of the furnace below a predetermined height that is approximately close to the vertical axis of the furnace, and / or at least one second submerged injector is arranged along the furnace sidewall at approximately equal distances between the two closest positions among the at least two first injectors. In the embodiment where at least one second submerged injector is arranged along the furnace sidewall, the at least one second injector preferably directs its injected additional gas towards a volume that is part of the internal space of the furnace below a predetermined height, which is different from the volume towards which the first injector directs the first hot gas. The applicants have found that this enhances the advantageous effects obtained by the present invention, which are widely described in the summary section above.

[0080] In one embodiment of the furnace or apparatus according to the present invention, the apparatus is further equipped to introduce a reducing agent into the first hot gas upstream of at least one first injector. This provides the advantage that more reducing agent can be introduced into the furnace, for example, in excess of the amount that can be introduced by other means, such as together with additional gas and / or added via a supply port. The amount of additional reducing agent that can be introduced via at least one first injector is independent of the enthalpy input to the furnace. Thus, this method of introducing the reducing agent is extremely convenient for controlling the redox characteristics of the furnace atmosphere. An additional advantage is that the reducing agent introduced via the first injector is introduced together with the enthalpy input at the highest temperature to the furnace. At higher temperatures, the equilibrium constant of the desired zinc fuming reaction (I) is favorable for the formation of zinc metal, which is an evaporable substance. Thus, the effectiveness of the reducing agent introduced together with the first hot gas is higher, and since this injection is carried out via an immersion-type injector, it is very efficient due to the very close contact between the first hot gas and the liquid in the liquid bath, meaning that there is almost no reducing agent that can reach the liquid bath surface without contacting the liquid from the bath.

[0081] In one embodiment of the furnace or apparatus according to the present invention, the reducing agent introduced upstream of at least one first injector can be selected from gases, liquids, solids, and combinations thereof. The Applicants have found that the introduction of the first hot gas from a plasma torch via the first injector is very tolerant with respect to the selection of the reducing agent, not only with respect to the state of the substance, but also with respect to the amount that can be introduced, thus providing a very wide variety of options for introducing an additional reducing agent.

[0082] In one embodiment of the furnace or apparatus according to the present invention, the apparatus further comprises at least one oxy-gas burner for generating additional first hot gas in an amount exceeding the amount of first hot gas of plasma quality from at least one plasma torch. This provides the advantage that the additional enthalpy input into the furnace can be provided in excess of the enthalpy input provided by the plasma generator. This can facilitate the maintenance of an advantageous heat balance throughout the furnace, apparatus, and / or method.

[0083] In one embodiment of the furnace or apparatus according to the present invention, the apparatus further comprises at least one submerged third injector for injecting additional first hot gas below a determined height. This provides the advantage of very close contact between the additional first hot gas and the liquid bath, which is advantageous for heat transfer from the additional first hot gas to the liquid bath inside the furnace. This increases the effect of heat transfer.

[0084] In one embodiment of the furnace or apparatus according to the present invention comprising at least one oxy-gas burner, the at least one oxy-gas burner is arranged below a determined height.

[0085] In one embodiment of the apparatus according to the present invention, the plasma torch is arranged below a determined height.

[0086] The feature of arranging the generator of hot gas and / or plasma below a determined height enables a very short connecting pipe, and the generator of hot gas or plasma can be arranged at the height of the injection point outside the furnace. However, measures are necessary to avoid flooding of the generator by the molten mass inside the furnace. Therefore, a continuous protective gas flow through the injector may be used.

[0087] In one embodiment of the furnace or apparatus according to the present invention, the post-combustion zone is provided above a height determined as part of a single-chamber furnace. Preferably, the post-combustion zone is provided above the liquid bath for radiant heat that can return from the post-combustion zone to the liquid bath within the furnace. As described elsewhere in this specification, in the post-combustion zone, the oxidation conditions are defined for the purpose of oxidizing evaporable metals or metal compounds to their corresponding oxidized forms. One of the main effects obtained by the complete conversion of the oxidation of the reduced form generated in the fuming process is that the gas containing the oxidized form is no longer highly flammable, and thus the safety hazards presented by the gas from the fuming process are removed downstream of the post-combustion zone or process. A second purpose of the post-combustion process is to oxidize most of the carbon monoxide that may be generated in the fuming process by the reaction of the carbon in the reducing agent with the oxygen available in the slag, for example as a metal oxide, to carbon dioxide, and / or to oxidize hydrogen to water. This further reduces the safety hazards, and also makes any further treatment of the furnace exhaust gas, including any final emissions to the atmosphere, easier, safer, and more environmentally acceptable.

[0088] Preferably, the Applicants carry out post-combustion by introducing an oxidizing agent into the fuming gas, and preferably this oxidizing agent is oxygen.

[0089] In one embodiment of the furnace or apparatus according to the present invention, the post-combustion zone preferably comprises a connection to a source of oxygen-containing gas selected from air, oxygen-enriched air, and purified oxygen gas. The Applicants consider it preferable to use air as it is readily available. Preferably, the Applicants introduce oxygen by injecting the oxygen-containing gas into the flow of fuming gas exiting the top of the furnace. Typically, the fuming gas exiting the top of the furnace is at a pressure lower than atmospheric pressure for the ventilation typically generated by at least the chimney of the furnace and optionally an induced draft fan upstream of the chimney for downstream exhaust gas treatment. Thus, the oxygen-containing gas can be available at atmospheric pressure. The Applicants thereby consider it preferable to provide the oxygen-containing gas at a pressure higher than atmospheric pressure, as a higher pressure difference is obtained between the source of the oxygen-containing gas and the fuming gas being ventilated into the furnace exhaust gas treatment facility by the natural or induced draft generated as described. The greater the pressure difference, the more advantageously the flow of the oxygen-containing gas into the fuming gas can be more accurately controlled.

[0090] In a simpler embodiment, the Applicants provide at least one opening to the atmosphere in the duct connecting the furnace and the downstream exhaust gas treatment facility, through which ambient air can be drawn in. Preferably, the size of the opening in the duct is controllable. A plurality of openings can be provided, with the advantage of more rapid and intimate mixing of the oxygen-containing gas and the fuming gas.

[0091] The Applicants have found that in the post-combustion zone, a stable flame front can be formed in which the oxidation reaction is occurring. The Applicants have found that as the fuming gas is moved faster and as the mixing with the oxygen-containing gas becomes faster and / or stronger, the flame front becomes more stable.

[0092] The present applicants preferably consider providing a considerably excessive oxidizing agent to a post-combustion zone or process so that the oxidation reaction in the post-combustion zone is substantially completed. This ensures that safety hazards are completely contained within the post-combustion zone or process and upstream of the post-combustion zone or process. It also ensures that the finally emitted exhaust gas is substantially free of the toxic gases carbon monoxide and hydrogen.

[0093] In one embodiment of the furnace or apparatus according to the present invention, the apparatus further comprises a cooling zone upstream of the recovery zone for cooling the gas being formed or the formed gas in the post-combustion zone. Cooling can be performed in various suitable ways.

[0094] One suitable method is to provide a so-called waste heat boiler, i.e., a heat exchanger in which the heat of the gas from the post-combustion process is used to generate steam. The advantages are that the heat is used to generate steam and that the steam can be used elsewhere to supply power or heat. Thus, the high investment cost of the waste heat boiler can be compensated by the usefulness of the generated steam. However, a steam-consuming device of appropriate size is not always available near the furnace according to the present invention.

[0095] Another preferred method of cooling is to utilize a radiating water cooler, in which the water on the coolant side circulates fast enough to avoid steam generation so that only hot water is produced. Preferably, the water is reused in the radiating water cooler after most of the heat has been removed. This warm water can also preferably be used for economically valuable purposes such as heating a plurality of houses, and more preferably, the water is reused after being used in the heating service. Additionally and / or alternatively, the hot water can be cooled in a conventional cooling tower. The amount of water evaporated in the cooling tower needs to be replenished before returning the remaining water to the radiating water cooler. Since salts accumulate in such a water cycle, the cycle typically also needs to provide a bleed stream (discharge stream) and replenish the amount of bleed water. The radiating water cooler also has the advantage of not changing the amount of gas that needs to be processed downstream of the gas side of the cooling process. Yet another advantage of the radiating water cooler is that this cooling process can be combined with a post-combustion zone, which means that the post-combustion process can be carried out within the radiating water cooler. This embodiment results in further simplification of the equipment and thus a reduction in investment costs.

[0096] Yet another method of cooling is spray cooling or "evaporative cooling". This method involves injecting water into the hot gas stream, and the injected water extracts its latent heat of vaporization from the gas stream. This method is very effective and rapid, requires little equipment, and thus has low investment costs. The drawback is that this method increases the amount of gas that needs to be processed downstream of the cooling process.

[0097] Another preferred method is to use the gas from the post-combustion process on one side of a heat exchanger and, for example, ambient air on the other side of the heat exchanger, together with a gas / gas heat exchanger. This results in the advantage of a compact volume and does not increase the gas flow that needs to be processed downstream of the cooling process.

[0098] The preferred cooling process may include several similar or different cooling methods selected from those listed above. A suitable combination is, for example, first providing a radiant water cooler at the high-temperature inlet side to lower the temperature of the gas from the afterburning process from, for example, about 1500 °C to, for example, about 1000 °C, and then providing a spray cooler to further lower the gas temperature to about 200 °C, which is low enough for the equipment used in the subsequent recovery zone.

[0099] In one embodiment of the furnace or apparatus according to the present invention, the recovery zone comprises a gas filtration zone, preferably the gas filtration zone comprises at least one gas filtration cloth. The Applicants preferably consider using a filter sleeve made of a cloth of polytetrafluoroethylene (PTFE) because it can withstand a processing temperature of up to about 260 °C.

[0100] Typically, the last equipment in the gas treatment sequence is a blower or ventilator for pushing the gas from the recovery zone into the exhaust stack and for improving the upstream ventilation by sucking the gas through the sequence of the afterburning zone, optionally the cooling zone, and the recovery zone. The use of a blower or ventilator has the advantage that the natural ventilation requirement of the exhaust stack is reduced and the stack does not have to be built very high.

[0101] In one embodiment of the furnace or apparatus according to the present invention, the furnace generally has a cylindrical shape, and preferably the furnace also has a conical lower part that tapers towards a smaller circular bottom, whereby the cylindrical shape of the furnace has a maximum inner diameter d, the furnace has an overall inner height h from the bottom to the top, and the ratio of h to d is at least 0.75, preferably at least 0.80, more preferably at least 0.85, even more preferably at least 0.90, also more preferably at least 0.95, preferably at least 1.00, more preferably at least 1.05, even more preferably at least 1.10, also more preferably at least 1.15, preferably at least 1.20, more preferably at least 1.25, even more preferably at least 1.30. In the context of the present invention, the inner diameter of the furnace is the distance between two opposing surfaces of the furnace wall, and in the case where there is a refractory lining, it is the distance between the surfaces of the refractory lining inside the furnace during construction. The inner diameter is considered excluding any possible accumulation on the surface of the freeze slag, which is a layer that may be referred to as the "freeze lining". The applicants have found that this feature provides the advantage of less scattering of the melt in the furnace bath during operation. Such scattered melt may solidify on any solid surface and cooler surface such as the furnace feed port and / or the furnace exhaust pipe, which may cause problems due to its high temperature, and the growth of such materials may cause other operational problems such as impairing the gas flow and / or the feed introduction ability.

[0102] In one embodiment of the furnace or apparatus according to the present invention, the furnace comprises a conical lower part, and the determined height is approximately the height at which the cylindrical shape changes to the conical lower part. The Applicants have found that the conical lower part provides a very convenient configuration. In this configuration, most immersion injectors, preferably the corresponding supply devices for these immersion injectors, can also be arranged to be very effectively injected into the liquid bath in the furnace with a minimum of connecting piping, while the amount of plot space that the device can occupy can also be limited. This configuration provides the advantage of bringing the first injector closer to the central vertical axis of the furnace, which is beneficial for bath stirring. This configuration also provides higher stirring at the bottom where the first hot gas is injected, and in embodiments where the device has tuyeres in the furnace wall of the smaller bottom, additional gas is injected, while at the upper part, since the diameter is larger, there is less splashing. A further advantage is that in the upper section, a doughnut-shaped liquid flow can be formed, which is beneficial for drawing in any particles of the solid reducing agent that may float on top of the liquid level in the bath.

[0103] In one embodiment of the furnace or apparatus according to the present invention, the furnace is provided with an inner refractory lining that can come into contact, in particular, with molten metal and / or matte. This has the advantage that metallurgical charges having a high melting temperature and / or a high liquidus temperature can be processed or treated. The refractory lining is preferably provided at the bottom, where the free molten metal and / or matte phase may occur, so that the benefit of increased resistance to chemical and / or mechanical attack from these liquids can be obtained.

[0104] In one embodiment of the furnace or apparatus according to the present invention, the outer peripheral wall of the furnace is water-cooled. The Applicants have found that this is beneficial for the longer life resistance of the equipment against the very high temperatures that can occur inside the furnace during operation. A further advantage is that a freeze lining can be formed on the inner surface of the furnace relative to the side wall of the furnace. Such a freeze lining can provide additional insulation against the sometimes very high temperatures inside the furnace during operation and can provide further protection for the refractory material provided against the furnace wall.

[0105] In one embodiment of the method according to the present invention, the amount of additional gas injected via at least one second injector is at least 10%, preferably at least 15%, more preferably at least 20%, 25%, 30%, 35%, 40%, 45%, 50%, or 55% of the amount of the first hot gas having an enthalpy amount of at least 3.5 kWh / Nm in volume units in the standard state, generated by a single element of at least one plasma torch having a maximum power rating, more preferably at least 60%, preferably at least 70%, more preferably at least 75%, 80%, 90%, 100%, 110%, 120%, 125%, 130%, 140%, 150%, 175%, 200%, 225%, and even more preferably at least 230%. Optionally, the amount of additional gas injected via at least one second injector is at least 3.5 kWh / Nm in volume units in the standard state, generated by a single element of at least one plasma torch having a maximum power rating, more preferably at least 60%, preferably at least 70%, more preferably at least 75%, 80%, 90%, 100%, 110%, 120%, 125%, 130%, 140%, 150%, 175%, 200%, 225%, and even more preferably at least 230%. 3 of the amount of the first hot gas of the plasma quality generated by a single element of at least one plasma torch having a maximum power rating, more preferably at least 60%, preferably at least 70%, more preferably at least 75%, 80%, 90%, 100%, 110%, 120%, 125%, 130%, 140%, 150%, 175%, 200%, 225%, and even more preferably at least 230%. Optionally, the amount of additional gas injected via at least one second injector is at least 3.5 kWh / Nm in volume units in the standard state, generated by a single element of at least one plasma torch having a maximum power rating, more preferably at least 60%, preferably at least 70%, more preferably at least 75%, 80%, 90%, 100%, 110%, 120%, 125%, 130%, 140%, 150%, 175%, 200%, 225%, and even more preferably at least 230%. 3When supplying a plasma having an enthalpy amount, it is up to 500%, preferably up to 450%, more preferably up to 400%, 350%, 325%, 300%, 290%, 280%, 275%, 270%, 265%, 260%, 250%, 240%, 230%, 220%, 210%, 200%, 180%, 165%, 150%, 135%, 120%, 110%, 100%, 90%, 80%, 70%, 60%, 50%, 40%, 30%, and even more preferably up to 20% of the amount of plasma that can be generated by a single element of at least one plasma torch having a maximum power rating. The applicants have found that, in particular, when an additional gas stream is used as a carrier for an additional reducing agent, especially when fine powders such as coal powder or petroleum coke dust are used as an additional reducing agent, the main advantages of the present invention can already be achieved by injecting an amount of additional gas stream close to the specified lower limit through a second injector.

[0106] In one embodiment of the method according to the present invention, the apparatus comprises a plurality of second injectors, and the amount of additional gas injected through each injector is at least 3.5 kWh / Nm in terms of volume per unit when the plasma torch is in the standard state 3 When supplying a first hot gas having an enthalpy amount, it is at least 10%, preferably at least 15%, more preferably at least 20%, 25%, 30%, 35%, 40%, 45%, or 50%, more preferably at least 55%, preferably at least 60%, more preferably at least 65%, even more preferably at least 70%, also more preferably at least 75%, preferably at least 80% of the amount of the first hot gas of the plasma quality that can be generated by a single element of at least one plasma torch having a maximum power rating. Optionally, each second injector is at least 3.5 kWh / Nm in terms of volume per unit when the plasma torch is in the standard state 3When supplying a plasma having an enthalpy amount, the amount of additional gas is injected at up to 200%, preferably up to 190%, more preferably up to 180%, 170%, 160%, 150%, 140%, 130%, 125%, 120%, 115%, 110%, 105%, 100%, 95%, and even more preferably up to 90% of the amount of the first hot gas of the plasma quality that can be generated by a single element of at least one plasma torch having a maximum power rating.

[0107] In one embodiment of the method according to the present invention, the additional gas injected via at least one second injector comprises at least one gas selected from the group consisting of hydrogen, nitrogen, air, carbon dioxide, argon, neon, helium, methane, ethane, propane, butane, and combinations thereof, preferably nitrogen or air, more preferably air, and even more preferably compressed air. The applicants have found that nitrogen and air, preferably compressed air, are very convenient gases as the main components of the additional gas injected into the furnace.

[0108] In one embodiment of the method according to the present invention, the additional gas injected via at least one second injector is heat-treated upstream of the at least one second injector to change its enthalpy amount, preferably, the heat treatment of the additional gas is carried out by using at least one heat exchanger. When the gas is supplied to the furnace at a temperature lower than the temperature of the liquid bath in the furnace, the applicants preferably consider heating the gas before it is injected by at least one second injector. This reduces the cooling effect that the injection of the additional gas can have on the furnace and makes it easier to maintain the heat balance of the entire furnace. Preferably, such heating at least partially utilizes the heat available in a system that treats the exhaust gas from the furnace.

[0109] In one embodiment of the method according to the invention, the temperature of the additional gas entering at least one second injector is at most equal to the temperature of the bath in the furnace, preferably at least 20 degrees Celsius lower than the temperature of the bath in the furnace, more preferably at least 50 degrees Celsius, even more preferably at least 100 degrees Celsius, and still more preferably less than at least 200 degrees Celsius lower than the temperature of the bath. This results in the advantage of less wear and fracture of the injection point or tuyere. Optionally, the temperature of the additional gas entering at least one second injector is at most 400 degrees Celsius lower than the temperature of the bath in the furnace, preferably at most 350, more preferably at most 300 degrees Celsius, even more preferably at most 250 degrees Celsius, preferably at most 200 degrees Celsius, more preferably at most 150 degrees Celsius, even more preferably at most 100 degrees Celsius, preferably at most 75 degrees Celsius, more preferably at most 50 degrees Celsius, and even more preferably at most 25 degrees Celsius lower than the temperature of the bath in the furnace. This results in the advantage of a low risk of accumulation of solidified slag on the orifice of the injection point or tuyere, which can be caused by the cooling effect of the additional gas entering the furnace through the injection point or tuyere.

[0110] In one embodiment of the method according to the invention, the additional gas injected via at least one second injector contains at least one first reducing agent, preferably, the at least one reducing agent contains elements other than oxygen and noble gases, and is selected from the group consisting of any substances that can react with oxygen under the conditions in the furnace, preferably selected from the group consisting of any substances containing carbon and / or hydrogen in a chemically bonded form that is susceptible to oxidation, more preferably, the reducing agent is selected from the group consisting of natural gas, gaseous and / or liquid hydrocarbons, fuel oil, rubber, plastic, preferably plastic made of at least one polyolefin, more preferably waste rubber and / or plastic, charcoal or coke, and combinations thereof, even more preferably, coke, and still more preferably petroleum coke, which is a highly carbon-rich by-product from crude oil processing. As described in the items of the above summary, the injection of additional gas into the furnace via at least one second injector represents an additional inlet point for adding a reducing agent into the furnace. In addition, since at least one second injector is immersed, the choice of suitable reducing agents is very wide.

[0111] In one embodiment of the method according to the invention using a first reducing agent, the first reducing agent is in solid, preferably particulate form, more preferably with a maximum size of 6 mm, even more preferably a maximum of 5, 4, 3, 2 or 1 mm, preferably a maximum of 500 μm, more preferably a maximum of 250, 200, 150, 100, or even 50 μm average particle diameter. The Applicants have found that suitable solid reducing agents are diverse and of high quality and are available from various sources. In addition, some of these suitable solid reducing agents have little or no alternative properties that can require any significant economic value. Thus, these solid reducing agents represent very interesting sources for use in accordance with the present invention. As described elsewhere in this specification, the smaller the particle size, the higher the surface-to-weight ratio and the lower the buoyancy, and thus the advantage of more efficient and effective use of the reducing agent is provided.

[0112] In one embodiment of the method according to the present invention, the additional gas injected via at least one second injector further comprises oxygen and fuel, and the fuel is such that when the additional gas is at a temperature lower than the temperature of the molten charge in the furnace at the injection point, it provides an enthalpy input that compensates for at least 50% of the cooling effect that the additional gas can bring into the furnace. The Applicants preferably consider adding an amount of fuel that compensates for at least 75%, preferably at least 100% of the described cooling effect. The Applicants preferably find that when the additional gas also further comprises oxygen, and more preferably when it further comprises at least sufficient oxygen to reach the desired lambda in the additional gas, additional heat input to the furnace can be obtained by injecting gaseous or liquid fuel as part of the additional gas. Typically, the temperature of the liquid bath in the furnace is higher than the temperature at which the fuel and oxygen in the additional gas start to react even without an ignition source. Thus, if sufficient oxygen is present in the additional gas, the additional fuel will easily burn if the additional gas comes into contact with the molten furnace charge. The Applicants have found that the gas flow can be easily set high enough so that the combustion reaction does not proceed upstream with respect to the direction of flow of the additional gas in the second injector and / or the conduit leading to at least one second injector. Thus, the risk of such a "backfire" phenomenon is very low. The Applicants have found that if the additional gas reaches a speed higher than the flame propagation speed in the additional gas at the second injector or at another location upstream of the second injector, the risk of equipment damage as a result of such heating inside or upstream of the injector can be easily eliminated. The Applicants have found that this condition can be very easily met.

[0113] In one embodiment of the method according to the present invention, the additional gas injected via at least one second injector has a first lambda that occupies only gaseous and liquid combustibles and is less than 1.0, preferably at most 0.9, more preferably at most 0.8, even more preferably at most 0.7, and still more preferably at most 0.6. Lambda (λ) means a very convenient parameter commonly used in relation to burners and combustible fuels, especially internal combustion engines. This parameter represents a ratio having the actual air-fuel ratio in the numerator and the air-fuel ratio of the same fuel in stoichiometry in the denominator. When the air / fuel mixture is stoichiometric, its lambda is thus 1.0. The Applicants apply this first lambda parameter to all gaseous mixtures in which oxygen is present and to other substances that can readily react with oxygen, such as combustible substances, where the other substances are gases, or liquids, or combinations thereof. The Applicants have found that when no solid reducing agent is used in the process, control of the first lambda of the additional gas injected via at least one second injector is a very convenient means for controlling the atmosphere inside the furnace, whereby it is set whether the atmosphere is neutral, oxidizing, or reducing, and the degree of oxidation or reduction. The Applicants have found that the additional addition points of the reducing agent in the apparatus according to the present invention are very versatile, and control of the first lambda and / or a second lambda, which will be further described below, in the additional gas injected provides a very convenient method for controlling the redox conditions in the furnace and thus for manipulating the chemical reactions occurring inside the furnace. The Applicants have found that the combination of the injection of the additional gas and the injection of the first hot gas from the plasma generator enables a wide range of redox conditions, whereby the redox conditions can be set substantially independently of the heat input to the furnace, unlike more conventional heating means such as using a natural gas burner.

[0114] The present applicants are also considering a second lambda, which is used in this method and takes into account all combustibles added to the additional gas, i.e., any solid combustibility such as most of the reducing agents described above herein. In one embodiment of the method according to the invention, the additional gas injected via at least one second injector has a second lambda of less than 0.6, preferably at most 0.5, more preferably at most 0.4, even more preferably at most 0.3, and still more preferably less than 0.2. The present applicants have found that such low second lambda values are very beneficial for the fuming of metals from metallurgical slags such as zinc.

[0115] In one embodiment of the method according to the invention, the additional gas injected via at least one second injector is combustible and the additional gas reaches a speed faster than the flame propagation speed of the additional gas within at least one second injector. The present applicants have found that, preferably when the additional gas also further contains oxygen, additional heat input to the furnace can be obtained by injecting a gaseous fuel or a liquid fuel as part of the additional gas. Typically, the temperature of the liquid bath in the furnace is higher than the temperature at which the fuel and oxygen in the additional gas start to react even without an ignition source. The present applicants have found that such a reaction can move upstream with respect to the direction of the flow of the additional gas in the conduit leading to at least one second injector and within the second injector itself. Such a "backfire" phenomenon can lead to the release of heat in the conduit of the injector and thus an increase in the temperature of the additional gas upstream and / or inside the injector. The present applicants have found that the risk of equipment damage as a result of such heating inside or upstream of the injector can be readily reduced or eliminated if the additional gas reaches a speed faster than the flame propagation speed in the additional gas at another location inside or upstream of the injector.

[0116] In one embodiment of the method according to the present invention, at least one evaporable metal or metal compound is the metal in its elemental form or an evaporable metal-containing compound, preferably the metal is selected from the group consisting of zinc, lead, tin, bismuth, cadmium, indium, germanium, and combinations thereof, whereby the evaporable compound can be, for example, an oxide, a sulfide, a chloride, and combinations thereof. The Applicants have found that the method according to the present invention is highly suitable for removing a metal or metal-containing compound selected from a given list by evaporation. The Applicants have found that this method provides a very competitive alternative for recovering one of the specified metals from the metallurgical charge.

[0117] In one embodiment of the method according to the present invention, a metal less noble than the metal in the evaporable metal or metal compound, preferably iron and / or aluminum, is added to the furnace, preferably the base metal is added in the form of fine particles, more preferably the fine particles have an average particle diameter of at most 5, 4, 3, 2, or 1 mm, preferably at most 500 μm, more preferably at most 250, 200, 150, 100, or even 50 μm, whereby the concentration of the base metal in the slag is preferably maintained below its solubility (dissolution limit) in the slag under the process conditions. The Applicants have found that this results in the advantage of improving the fluidity of the slag phase that may be present inside the furnace as part of the liquid bath. However, the Applicants have found that it is preferable to maintain the concentration of these compounds below the solubility of the compounds in the liquid bath, as exceeding the solubility may result in the formation of a separate phase in the furnace for certain compounds. Such a separate phase risks impairing the contact between the other liquid phases in the liquid bath and the injected additional gas and / or the first hot gas generated by the plasma torch, and / or, if present, the additional first hot gas generated by the oxy-gas burner, and thus may impair the desired chemical reactions in the furnace, and as a result, may particularly impair the evaporation of the evaporable metal or metal compound.

[0118] In one embodiment of the method according to the present invention, the second reducing agent is added to the first hot gas of the plasma quality upstream of at least one first injector. This brings the advantage that more reducing agent is introduced into the furnace than the amount that can be introduced together with the additional gas. The amount of additional reducing agent that can be introduced via at least one first injector is independent of the enthalpy input to the furnace. Therefore, this method of introducing the reducing agent is extremely convenient for controlling the redox characteristics of the furnace atmosphere. An additional advantage is that the reducing agent introduced via the first injector is introduced into the furnace together with the enthalpy input at the highest temperature. At higher temperatures, the equilibrium constant of the desired zinc fuming reaction (I) is favorable for the formation of zinc metal, which is an evaporable metal or metal compound. Therefore, the effectiveness of the reducing agent introduced together with the first hot gas from the plasma torch is higher, and since this injection is performed via an immersion-type injector, it is very efficient due to the very close contact between the first hot gas and the liquid in the liquid bath, meaning that there is almost no such reducing agent that can reach the liquid bath surface from the bath without contacting the liquid.

[0119] In one embodiment of the method according to the present invention using a second reducing agent, the second reducing agent is selected from gases, liquids, and solids, and combinations thereof, and preferably, the second reducing agent is selected from the group consisting of natural gas, gaseous and / or liquid hydrocarbons, fuel oil, charcoal or coke, and combinations thereof, even more preferably coke, still more preferably petroleum coke, preferably in the form of solid fine particles, and more preferably, the fine particles have an average particle diameter of at most 6 mm, even more preferably at most 5, 4, 3, 2, or 1 mm, still more preferably at most 500 μm, preferably at most 250, 200, 150, 100, or even 50 μm. The present applicants have found that the introduction of plasma via the first injector is extremely tolerant with respect to the selection of the reducing agent, not only with respect to the state of the substance but also with respect to the amount that can be introduced, thus providing a very wide variety of options for introducing an additional reducing agent.

[0120] In one embodiment of the method according to the present invention, a step of adjusting the oxygen potential in the slag within a range of 10 to 10 -9 Pa (i.e., 10 -4 to 10 -14 atm) is included. Preferably, the oxygen potential in the slag is adjusted by the addition of the first and / or second reducing agent. Thanks to the use of a plasma torch, substantially any oxygen potential can be combined with any calorific value. In combination with the recovery of one or more evaporable metals or metal compounds, other metals can also be extracted from the materials introduced into the furnace. In one embodiment, the oxygen potential in the slag may be suitable for selectively reducing metal compounds in the slag to the molten metal phase. Examples of such typical metals that can be reduced from the slag are Cu, Ni, Sn, Pb, Ag, Au, Pt, and Pd. Then, the molten metal phase can be collected at the bottom of the furnace. Then, the molten metal phase can be removed continuously or intermittently through an outlet port. The furnace may be provided with a refractory lining at the bottom for this purpose. In another embodiment, materials are introduced into the furnace, whereby the slag also contains sulfur or a sulfur compound, and a matte phase can be obtained. Then, the oxygen potential in the slag may be made suitable for preventing sulfur from being oxidized. Then, the metal can be recovered in the molten matte phase. Examples of metals that can be recovered from the matte phase slag are Fe, Cu, Ni, Sn, Pb, Ag, Au, Pt, and Pd. Then, the molten matte phase can also be collected at the bottom of the furnace. The molten matte phase can be removed continuously or intermittently through an outlet port. In yet another embodiment, both the metal phase and the matte phase can be obtained by appropriate adjustment of the oxygen potential and sulfur content. As a non-limiting example, Au, Pt, and Pd may be reduced to the metal phase, and Cu and Ni may be made to form the matte phase. The matte phase typically has a lower density than the metal phase and, since the two phases remain more or less insoluble in each other, typically appears on top of the metal phase. The matte phase and the metal phase may be extracted from the furnace through separate outlets or a common outlet.

[0121] In one embodiment of the method according to the present invention, afterburning is carried out inside a single-chamber furnace. This brings the advantage that the equipment design becomes much more compact and thus the investment cost is reduced.

[0122] In one embodiment of the method according to the present invention, afterburning preferably includes the introduction of an oxygen-containing gas selected from air, oxygen-enriched air, and purified oxygen gas into the afterburning zone. The applicants have found that this option represents a relatively simple and low-investment-cost option for performing the function of the afterburning zone. The applicants preferably consider using just air as described above.

[0123] In one embodiment of the method according to the present invention, the oxidized form of at least one evaporable metal or metal compound is recovered from the gas as dust. The applicants have found that this option is much safer compared to alternatives where the metal condenses to form a liquid metal phase, for example, as described in U.S. Patent No. 4,588,436, since the risk of spontaneous ignition and / or explosion of the exhaust gas from the furnace substantially ends at the outlet of the afterburning zone. The applicants have also found that this option also has a relatively low investment cost compared to alternatives described, for example, in U.S. Patent No. 4,588,436.

[0124] In one embodiment of the method according to the present invention, the recovery of the oxidized form of at least one evaporable metal or metal compound from the gas includes filtering the gas containing the oxidized form of at least one evaporable metal or metal compound using a filter, preferably a filter cloth. As explained above, the applicants preferably consider using filter sleeves made of polytetrafluoroethylene (PTFE) cloth. In such a gas filter, the gas velocity can be extremely low locally. However, oxygen is expected to be present. Therefore, in the method according to the present invention, it is important that substantially all of the reduced forms of the metal or metal compound have been oxidized to the oxidized form and the risk of spontaneous ignition and / or explosion is acceptably low.

[0125] In one embodiment of the method according to the present invention, the method further comprises a cooling step upstream of the recovery of the oxidized form of at least one evaporable metal or metal compound from the gas. As described above, various suitable cooling methods can be applied.

[0126] Typically, the last step of the gas treatment sequence is a blower or ventilator that pushes the gas from the recovery zone into the exhaust stack and also improves the upstream ventilation by drawing the gas through the sequence of the afterburning zone, optionally the cooling zone, and the recovery zone.

[0127] In one embodiment of the method according to the present invention, the method includes the formation of a molten metal phase, and the method further includes the step of removing the molten metal phase from the furnace. The Applicants have found that the method according to the present invention may probably result in the formation of a separate molten liquid phase caused by the reduction to the elemental form of a metal with low volatility. This may be a pure metal phase or a molten alloy. In such a situation, it is extremely convenient to remove the separate molten metal phase from the furnace as a separate by-product. In the case of an alloy, it may be preferable to further process the alloy so that at least one of the metals in the alloy is recovered separately from a part of the other metals in the alloy. This further treatment can include a pyrometallurgical process and / or an electrolytic process.

[0128] In one embodiment of the method according to the present invention, the metal charge includes slag, the slag includes sulfur and / or sulfur compounds, and the method further includes the step of forming a molten matte phase and a further step of removing the molten matte phase from the furnace. This is an optional option added to the recovery of the liquid molten metal or alloy from the method.

[0129] In one embodiment of the method according to the present invention, the metallurgical charge is introduced into the furnace as a liquid. This provides the advantage that the metallurgical charge does not need to be melted and / or smelted as part of the process operated in the apparatus and / or furnace, which is beneficial for the heat balance of the furnace and thus the productivity of the method and its equipment, i.e., the furnace itself.

[0130] In one embodiment of the method according to the present invention, the metallurgical charge is metallurgical slag, preferably the metallurgical slag is selected from copper smelting slag, copper refining slag, and combinations thereof, and the method produces a second slag. The Applicants have found that the method (and apparatus) according to the present invention is very suitable for processing the specified feedstock.

[0131] In one embodiment of the method according to the present invention, the molten slag has an average temperature less than 50 degrees Celsius higher than the liquidus temperature of the slag. This provides the advantage that the freeze lining of solid slag formed on the inner surface of the furnace wall and providing protection for the refractory lining is easily maintained at a thickness sufficient to provide adequate protection and insulation. Such a freeze lining acts as insulation between the high-temperature liquid slag in the furnace and the furnace wall, which is preferably cooled to protect its mechanical integrity, and is thus very beneficial in terms of the heat balance of the furnace. Therefore, the freeze lining reduces the heat loss from the furnace to the cooling wall.

[0132] In one embodiment of the method according to the present invention, oxides selected from CaO, Al2O3, and combinations thereof are preferably added to the slag in a fumer furnace at a temperature of at least 1000 °C, preferably at least 1050 °C, more preferably about 1150 °C. This feature can further optimize and stabilize the final composition of the second slag after the fuming process, and in some cases also affect the mineral properties to make the slag more suitable for a specific end use. The Applicants have found that addition at high temperatures and in a molten state as specified is more effective in obtaining the desired effect.

[0133] In one embodiment of the method according to the present invention, the temperature of the slag in the furnace is at least the temperature specified in the previous paragraph, more preferably even higher, at least 1200 or 1250 or 1300 °C, more preferably about 1350 °C, etc. This results in the advantage of a more favorable equilibrium constant between the evaporable metal or metal compound and its precursor in the liquid slag. A further advantage of the higher temperature is that it facilitates the removal of the fumed slag from the furnace, so-called "tapping", whether this is done by overflow or bottom tapping from a properly positioned bottom tapping opening in the furnace wall.

[0134] In one embodiment of the method according to the present invention, the method further comprises the step of cooling the second slag to a solid, preferably the second slag is first removed from the furnace as a liquid. The advantage is that the fumarole can be opened for further slag treatment while the second slag is being cooled. The slag can be cooled and / or solidified by bringing it into contact with a cooling medium such as air and / or water, and in some cases ambient air.

[0135] In one embodiment of the method according to the present invention, the second slag is cooled, and this cooling is effected by bringing the liquid second slag into contact with water. The Applicants have found that cooling with water is extremely effective and can be applied in various ways to provide a relatively well-controlled cooling rate.

[0136] In one embodiment of the method according to the present invention in which the second slag is cooled, the second slag is cooled at a rate of at least 30 degrees Celsius per second, preferably at least 40 degrees Celsius per second, more preferably at least 50 or 60 degrees Celsius per second. The Applicants have found that, as specified, at higher cooling rates, slags with a higher amorphous content can be obtained, which is of interest for certain end uses, such as when the slag is intended for use as a binder in the construction industry.

[0137] In one embodiment of the method according to the present invention, the second slag is cooled, and the method further includes a step of grinding the solid second slag, preferably a step of grinding the second slag into powder.

[0138] In one embodiment of the method according to the present invention in which the second slag is cooled, the second slag is cooled at a rate of at least less than 40 degrees Celsius per second, preferably at least less than 30 degrees Celsius per second, more preferably at least less than 20 degrees Celsius per second. The present applicants have found that, as specified, at a lower cooling rate, a slag with a lower amorphous content can be obtained, and thus a higher crystallinity can be obtained, which is important for certain end uses, such as when the slag is intended for use as an aggregate or for decorative purposes.

[0139] In one embodiment of the method according to the present invention, the second slag is formed by the method, and the method further includes a step of adding the second slag as a binder or aggregate during the manufacture of an object for the construction industry. The present applicants have found that the second slag can be used as a binder for aggregates, preferably as an active binder, preferably as a binder having pozzolanic activity. The present applicants have found that the slag can act as a binder in the replacement of cement, such as when partially replacing a cement such as Portland cement, but can also act as a binder for producing a geopolymer composition.

[0140] In one embodiment of the method according to the present invention, the slag is used as a binder during the manufacture of an object for the construction industry, and this object further includes aggregates, where the aggregates preferably include sand and / or a second slag.

[0141] In one embodiment of the method according to the present invention, the slag is used as a binder during the manufacture of an object for the construction industry, the object further comprising aggregates, and the method further comprises the step of adding an activator during the manufacture of the object. The Applicants have found that a second slag can act as an active binder and can react with a suitable activator, thereby exhibiting strong binding properties to the aggregates. Thus, the second slag can be used as an alternative to Portland cement or as the sole binder of the object, in which case the second slag is considered a "geopolymer" and provides fire resistance and heat resistance, for example, to coatings, adhesives, composites, etc.

[0142] In one embodiment of the method according to the present invention using an activator, the activator is selected from the group consisting of sodium hydroxide, NaOH, potassium hydroxide, KOH, sodium silicate, Na2SiO3, potassium silicate, K2SiO3, and combinations thereof, and preferably, the activator is NaOH.

[0143] In one embodiment of the method according to the present invention in which an object for the construction industry is formed, the object for the construction industry is a building element.

[0144] In one embodiment of the method according to the present invention, the building element is selected from the list consisting of tiles, pavers, blocks, concrete blocks, and combinations thereof.

[0145] In one embodiment of the method according to the present invention in which an object for the construction industry is formed, the object for the construction industry has a foamed structure.

[0146] In one embodiment of the use according to the present invention, the metallurgical charge is selected from copper smelting slag and copper refining slag and combinations thereof.

[0147] In one embodiment of the use according to the present invention, the evaporable metal or metal compound is selected from zinc, lead, tin, bismuth, cadmium, indium, germanium, and combinations thereof.

[0148] In one embodiment of the method according to the invention, at least part of the method is preferably electronically monitored and / or controlled by a computer program. The Applicants have found that electronically controlling the steps from the method according to the invention, preferably by a computer program, offers far better processing advantages, the results are much more predictable and closer to the process target. As an example, based on temperature measurements, if desired also based on pressure and / or level measurements, and / or in combination with the results of chemical analysis of samples taken from the process stream and / or analysis results obtained online, the control program can control the supply or removal of electrical energy, the supply of heat or cooling media, and equipment related to flow and / or pressure control. The Applicants have found that such monitoring or control is particularly advantageous in processes operating in continuous mode, but can also be advantageous in processes operating in batch or semi-batch mode. In addition, preferably, the monitoring results obtained during or after the execution of the steps in the method according to the invention are also used, as part of the overall method of which the method according to the invention is only a part, for the monitoring and / or control of other steps as part of the method according to the invention, and / or of methods applied upstream or downstream of the method according to the invention. Preferably, the entire method is electronically monitored, more preferably by at least one computer program. Preferably, the entire method is electronically controlled as much as possible.

[0149] The Applicants also preferably consider that data and instructions are passed from one computer or computer program to at least one other computer, or computer program or module of the same computer program, for the monitoring and / or control of other methods including but not limited to the method described herein.

[0150] Example 1 In this Example 1, a furnace equipped with three plasma generators was provided.

[0151] The furnace, also referred to as the "device", "reactor", or "fumer", had an overall height of the supply port from bottom to top of approximately 7.34 m. The furnace top was formed by a dome equipped with a top supply port and an off-gas discharge duct. Below the top dome having a height of 1.09 m, the furnace had a cylindrical top section with an outer diameter of 5.50 m and a height of approximately 3.00 m around a vertical axis. Below this top section, the furnace tapered over a height distance of approximately 1.66 m and ended with a bottom cylindrical portion having a diameter of approximately 3.19 m and a height of 1.00 m. The height of the bottom dome was 0.60 m. The height of the bottom cylindrical portion was 1.00 m and the height of the tapered portion was 1.66 m.

[0152] During operation, the furnace was assumed to contain a molten bath up to above the highest opening of the inlet points of at least the first hot gas of plasma quality and additional hot gas. For that purpose, the Applicants preferably consider maintaining the liquid level in the furnace at least at the same height as the bottom of the tapered portion. More preferably, the liquid level is maintained somewhat higher somewhere within the height of the tapered portion. If necessary, the height may be raised up to above the tapered portion, but should be kept below the height at which the hydrostatic head becomes too great a burden for introducing the first hot gas and / or additional gas and bath agitation is impaired.

[0153] The furnace shell is provided as a double-wall water-cooled alloy steel structure, except for the part well protected by the refractory lining. In the space inside the double wall during operation, cooling water flowing as part of the pump around the circuit is provided. This cooling is provided to protect the structural integrity, especially the mechanical strength, of the reactor wall. Due to the cooling, a part of the liquid slag in the furnace solidifies against the wall with a so-called "freeze lining" although it is below the liquid level, but also due to the scattering of the liquid slag against most of the furnace wall above the liquid level. This solid freeze lining protects the wall from many forms of chemical and mechanical wear. It also provides insulation and thus reduces the heat that may be lost from the contents of the furnace to the cooling water. Also, since some molten metal phase may be formed during the process, the bottom cylindrical part and the bottom dome are lined with a suitable combination of refractory materials, in this case insulating bricks, wear lining, and refractory concrete. Most of these parts were not part of the water-cooling system.

[0154] Three plasma generators (PGs) for injecting hot gas into the furnace through tuyeres in a direction perpendicular to the furnace wall are provided at the same height along the outer circumference at approximately equal distances below the wall of the bottom cylindrical part and thus below the liquid level during operation.

[0155] A plasma generator is a device that generates a very high-temperature gas that is at least partially converted into plasma. The typical gas temperature is 3500 - 5000 °C. This gas is heated by electrical energy. A high voltage difference between two electrodes creates an electric arc between the electrodes. In this reactor during operation, air is blown through the arc and heated by the energy from the arc. As the current increases, more air is heated and more power can be transferred to the air. The PG power (expressed in W: watts) is defined as voltage (V: volts) × current (A: amperes). In the operation of this type of plasma, there is a relationship between the PG nominal power and the amount of air that can be blown through the PG.

[0156] The three plasma generators of the reactor of the example have a nominal power of 3 MW, and during the operation of the furnace, each was supplied with a quantity of compressed air in the range of 300 - 900 Nm 3 / h. At a reference enthalpy of the generated gas of 3.5 kWh / Nm 3 , the plasma generators were each able to generate 857 Nm 3 of plasma quality hot gas as the "primary gas".

[0157] The PG was not directly attached to the reactor wall. The PG was blowing the first hot (plasma generating and plasma quality) gas into the furnace through tuyeres. A tuyere is a nozzle that forms an opening in the reactor, through which hot gas can be supplied to the reactor. This tuyere can be further used to mix a secondary volume of natural gas and / or additional air with the hot gas from the PG, if necessary. Preferably, the Applicants always maintain a substantial volume of secondary gas through the tuyeres when there is a high-temperature liquid bath in the furnace. The purpose is to keep sufficient gas flowing through the tuyeres to prevent hot liquid from entering the tuyeres even when the PG needs to be shut down and / or removed, and to avoid the risk that some liquid flows upstream to the tuyeres and is cooled and solidified at the tuyeres, which is to avoid the risk of showing a significant burden required for its removal until the tuyere returns to a state fully suitable for its intended use.

[0158] During operation, an additional 90 - 200 Nm 3 / h of natural gas was added to the first hot gas from each PG through the corresponding tuyere holes. Also, additional air at a rate in the range of 100 - 250 Nm 3 / h was typically added through each of these tuyeres. Therefore, these volumes are recognized as secondary gas volumes.

[0159] The natural gas used in this example contained 84.206% by volume of methane, 3.646% by volume of ethane, 0.572% by volume of propane, and 9.966% by volume of nitrogen. The remaining volume of less than 1% was composed of higher alkanes, mainly butane and pentane.

[0160] On the opposite side of each combination of plasma generator and tuyere, additional tuyeres for injecting additional gas into the furnace were provided, so there were three in total in the whole furnace. These additional tuyeres or injectors represent the second submerged injector according to the present invention. They were also configured to inject their additional gas in a direction perpendicular to the furnace wall, but a change to a preferred option of injecting upward at an angle into the bath is planned.

[0161] The second submerged injector was constructed using the same type of tuyere as used downstream of the plasma generator. These tuyeres, and thus the tuyeres downstream of the PG, were also water-cooled. They were cylindrical in shape with a double wall and protruded into the furnace space through the furnace wall below the height of the liquid bath expected to be in the furnace during operation. The tuyere is provided for injecting secondary gas into the double wall of the tuyere. A plurality of holes for introducing secondary gas into the central volume of the tuyere through which the primary gas passes are provided in the inner cylinder of the tuyere. In the case of the upstream PG, it was the plasma quality hot gas generated by the PG itself. The holes are preferably provided as nozzles for imparting additional velocity to the gas in order to promote mixing of the secondary gas and the primary gas passing through the tuyere. Using the second submerged injector, the PG was replaced with a simple tube that protruded in the direction of the liquid bath through the tuyere and preferably protruded substantially as long as the tuyere extended into the furnace. Through this tube, primary gas such as compressed air could be pushed in and optionally supplemented with a certain amount of natural gas. A certain amount of additional reducing agent such as pulverized coal could be mixed into the primary gas or one of its components.

[0162] To each of the three additional injectors, a total amount of primary gas and secondary gas of 300 - 600 Nm 3 / h was supplied during operation, and 30 - 60 Nm 3The amount of natural gas of / h and, where appropriate, about 150 - 200 kg / h of pulverized coal as an additional reducing agent were mixed. The average particle size of the pulverized coal was 120 μm. The gas pressure upstream of the further tuyere was 6 bar gauge. The gas velocity at the further tuyere was typically higher than 330 m / s during operation.

[0163] A double - pressurized vessel system was used to inject the pulverized coal. The top vessel acted as a pressure lock: the pressure remained at atmospheric pressure when typically filled from a hopper located at the top of the pressure vessel through a discharge valve. The hopper was typically filled by mechanical transport using a supply belt or screw, but optionally by big bag unloading. After filling, this vessel was pressurized to the injection pressure. Then, by discharging the contents from the top vessel into the bottom vessel, the lower vessel maintained at the injection pressure could be filled. A weight - regulated supply system was provided to supply the pulverized coal from the bottom vessel into the injection air. Then, the air and the pulverized coal were transferred by pressure to a further injector and then to the liquid slag. The advantage of the double - vessel system is that the inflow of the reducing agent into the reactor can be maintained without interruption.

[0164] The tuyere, plasma generator, and injector were all water - cooled.

[0165] At the top of the furnace, a radiation water - cooler was provided, which was provided as a double - walled metal cylinder through which the furnace exhaust gas passed through the center of the cylinder and the cooling water was extruded through the wall of the cylinder.

[0166] Between the furnace top and the radiant water cooler, ambient air can enter and mix with the furnace exhaust gas. The evaporated zinc and CO present in the gas contact the oxygen in the air in the high-temperature gas, and these substances autoignite to form a post-combustion zone. Thanks to the substantial ventilation inside the furnace and the water cooler, the exhaust gas flows at high speed. Ambient air can enter through openings that are appropriately designed so that the air mixes rapidly and intensively with the exhaust gas. As a result, a stable flame front is established inside the radiant water cooler, and a portion of its radiant heat is radiated downward from the post-combustion zone onto the liquid bath inside the furnace. The furnace top and the radiant water cooler are also provided with a plurality of injection points through which air can be injected into the furnace exhaust gas under pressure. This capability can be used while allowing ambient air to enter through the openings. However, preferably, the openings for allowing ambient air to enter are substantially closed, and substantially all the required oxygen is introduced through the injection points. This mode of operation is preferred because the entry of oxygen is more stable and better controllable than alternative forms through which ventilation air can enter.

[0167] In the post-combustion zone, the gas reaches a temperature of up to 1500 °C.

[0168] The gas exiting the post-combustion zone was at a temperature of about 1200 °C. Downstream of the radiant water cooler, about 6 - 7000 liters / h of water was injected into the gas stream. This spray cooling process reduces the gas temperature to about 220 °C.

[0169] The wet gas from the spray cooling process is sent to a gas filter, where a porous PTFE sleeve is provided over a cylindrical stub, and this sleeve holds the dust represented by the oxidized form of the evaporable metal or metal compound formed in the post-combustion zone.

[0170] Downstream of the gas filter, a ventilator provides the suction force from the furnace and blows the filtered gas into the exhaust stack.

[0171] The fumigation method and furnace were operated in a batch mode. The operating batches reported below consisted of a clearly defined series of distinguishable process steps. Between different process steps, more or less, depending on the desired effect, electric power, pulverized coal, air, and natural gas were supplied to the reactor. The operation of the PG, tuyeres, and further injectors (or tuyeres) changed according to the process steps. Here, different processes will be described in detail.

[0172] First process step: Liquid filling of the furnace: At the start of the batch, 76900 kg of liquid slag from the upstream copper smelter was supplied to four slag pots and weighed by the weighing device of the bridge crane that transfers the slag pots between different furnaces to obtain a net weight of approximately 19 tons each.

[0173] At the upstream copper smelter, the slag is well mixed before being poured from the smelting furnace. Therefore, the slag composition can be considered homogeneous. The composition of most metals in the slag was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES), also known as inductively coupled optical emission spectrometry (ICP-OES) and sometimes simply called ICP, and for SiO2 by X-ray diffraction (XRF). The XRD technique used was quantitative X-ray diffraction analysis using Topas Academic Software V5 with Al2O3 as the internal standard.

[0174] TIFF0007698638000001.tif103170

[0175] In this process step, the PG was set at a power level of 1400 kW each and an average air flow of approximately 437 Nm 3 / h per PG as the primary gas. In addition, the following secondary gases were used. The natural gas flow through the tuyere was 125 Nm 3It was controlled at / h. The airflow passing through the tuyere was 100 Nm 3 It was controlled at a level of / h.

[0176] The total flow rate of the primary gas and the secondary gas passing through the additional injector as the second immersion type injector was 380 Nm of air per injector 3 It was set at / h, and natural gas was added at a rate of 44 Nm 3 / h. Pulverized coal injection was not yet operating at this process stage.

[0177] Second process stage: Fuming process After filling the liquid slag, the fuming process was started. In this process, the input of energy and reducing agent was increased to promote the volatilization of zinc as vapor.

[0178] The PG was set to a power level of 2500 kW each, and the average primary air flow per PG was 714 Nm 3 / h. In addition, the following secondary gas was used. Natural gas was added to each tuyere downstream of the PG at a rate of 148 Nm 3 / h. The additional airflow passing through the tuyere was set at 100 Nm 3 / h.

[0179] Air was supplied to the total flow rate of the primary gas and the secondary gas passing through the additional injector at 380 Nm 3 / h per injector. Natural gas was added to each injector at 44 Nm 3 / h. The pulverized coal injection to each injector was set at 180 kg / h.

[0180] The input of energy and reducing agent caused the fuming of volatile compounds from the liquid slag. The most volatile element was Zn. Zn existed in the slag as zinc oxide (ZnO). The temperature in the reactor was maintained in the range of 1180 - 1250 °C to ensure that the slag remained fluid. Thanks to the various inputs of different reducing agents, namely powdered coal and various inputs of natural gas, ZnO was reduced to metallic zinc (Zn). At atmospheric pressure, Zn can evaporate at temperatures above 906 °C. Therefore, Zn evaporated from the slag bath and was transported as part of the process gas from the furnace to the flue gas treatment facility.

[0181] In the off-gas discharge duct of the reactor, a large amount of air was mixed with the process gas, causing complete afterburning of the process gas. Any remaining CO, Zn, and H2 were completely oxidized in that process. Zinc in vapor form oxidized to ZnO and formed solid particles. Therefore, this ZnO formed dust in the combustion-treated off-gas stream. A cooling process followed this post-combustion or after-burning process. At the outlet of the cooling process, the temperature of the process gas was less than 220 °C. Then, the process gas was filtered through a bag filter equipped with a PTFE cloth. After filtration, the process gas was discharged into the atmosphere through a chimney. The ZnO dust particles were collected by the filter, cooled, and stored in a dust silo. The Zn-rich dust product could be taken out from the silo to a sales silo truck.

[0182] Samples were taken during fuming and analyzed by XRF, a fast but slightly less accurate method. When the Zn level in the slag in the furnace reached the desired level, fuming was stopped and the trimming process was started.

[0183] The Third Process Step: Trimming The purpose of this process was to oxidize the last remaining powdered coal in the furnace charge and heat the slag to a more suitable tapping temperature. The target temperature was 1220 - 1250 °C.

[0184] The PGs were operated continuously at an output level of 2500 kW each with an average primary air flow of 714 Nm per PG per hour. In addition, the following secondary gases were used. The natural gas flow through the tuyere was set at 102 Nm per hour. The air flow through the tuyere was set at 100 Nm per hour. 3 As the total flow rate of the primary gas and the secondary gas through the additional injector, 380 Nm per hour of air and 44 Nm per hour of natural gas were each supplied to these second submerged injectors. The injection of pulverized coal was stopped during this trimming process. 3 No slag samples were taken after completion of the trimming process. Tapping was immediately started. 3 Fourth process step: Slag tapping and granulation

[0185] The purpose of this process is to extract liquid slag from the reactor. A taphole located on the side of the reactor was drilled and the liquid slag was allowed to flow out of the reactor into a launder. From that launder, the slag product was granulated by a water granulation system in which a large amount of water was sprayed onto the falling slag stream, thereby solidifying the liquid slag and breaking the formed solid into particles of ±1 mm. 3 The PGs continued to operate during this tapping and granulation process at a power level of 2000 kW each with an average primary air flow of 606 Nm per PG per hour. As the secondary gas, a natural gas flow of 128 Nm per hour to the tuyere was set, and then the direct air flow to the tuyere was set at 100 Nm per hour. 3 The additional injectors also continued to operate with air at a rate of 380 Nm per hour and a total of 44 Nm per hour of natural gas for the primary and secondary gases. The injection of pulverized coal was stopped.

[0186] No slag samples were taken after completion of the trimming process. Tapping was immediately started.

[0187] Fourth process step: Slag tapping and granulation The purpose of this process is to extract liquid slag from the reactor. A taphole located on the side of the reactor was drilled and the liquid slag was allowed to flow out of the reactor into a launder. From that launder, the slag product was granulated by a water granulation system in which a large amount of water was sprayed onto the falling slag stream, thereby solidifying the liquid slag and breaking the formed solid into particles of ±1 mm.

[0188] The PGs continued to operate during this tapping and granulation process at a power level of 2000 kW each with an average primary air flow of 606 Nm per PG per hour. As the secondary gas, a natural gas flow of 128 Nm per hour to the tuyere was set, and then the direct air flow to the tuyere was set at 100 Nm per hour. 3 As the secondary gas, a natural gas flow of 128 Nm per hour to the tuyere was set, and then the direct air flow to the tuyere was set at 100 Nm per hour. 3 / h of natural gas flow to the tuyere was set, and then the direct air flow to the tuyere was set at 100 Nm 3 / h.

[0189] The additional injectors also continued to operate with air at a rate of 380 Nm per hour and a total of 44 Nm per hour of natural gas for the primary and secondary gases. The injection of pulverized coal was stopped. 3 / h of air and a total of 44 Nm 3 / h of natural gas. The injection of pulverized coal was stopped.

[0190] Samples of the final product after granulation were taken. The composition is thought to be close to that of the slag immediately after the fuming process.

[0191] Further operating parameters of the PG at each process stage are shown in Table II, where "enthalpy" is calculated from the input power to the PG and the air flow supplied to the PG.

[0192] TIFF0007698638000002.tif48170

[0193] The progress of the slag composition during the batch is shown in Table III, showing the analysis results of the slag samples taken after each process:

[0194] TIFF0007698638000003.tif76170

[0195] Output material composition This batch produced approximately 10500 kg of filter dust with the composition shown in Table IV, and the results of ICP analysis of representative samples were as follows:

[0196] TIFF0007698638000004.tif106170

[0197] A second batch was carried out for comparison purposes, during which no further tuyeres had been installed yet. To provide the same amount of reducing agent during the fuming process, the same amount of carbon was introduced by introducing coarse petroleum coke with a particle size in the range of 6 - 10 mm through the supply port.

[0198] The amount and composition of the liquid slag feed were very similar to those of the first batch, such as the supply time, trimming time, and tapping time. The main difference was the fuming time.

[0199] The amount and composition of the product after granulation and the amount and composition of the filter dust were equivalent.

[0200] The time required for the fuming process to obtain a very similar Zn content in the final slag was significantly higher in this comparative batch compared to the batch according to the present invention described above. This means that the comparative batch had a significantly lower zinc fuming rate compared to the example, and thus the present invention significantly increased the zinc fuming rate during the fuming process.

[0201] Example 2 In this Example 2, the same furnace as in Example 1 was used, but the configuration regarding the second immersion type gas injection was different. The natural gas supply amount and its quality were the same.

[0202] Only a combination of one additional injector and tuyere was provided as a single second immersion type injector for injecting additional gas and fine coke into the furnace at the same level or height as the combination of the three plasma generators and tuyere. The tuyere was water-cooled, and air at a constant rate of 350 - 400 Nm 3 / h was injected through the tuyere and then through the holes in the inner wall of the tuyere. Natural gas supply was not used in this example.

[0203] The injector arranged inside the combination of the additional injector and tuyere supplied additional gas in the liquid slag bath in a direction perpendicular to the furnace wall. During operation, compressed air in an amount of 100 - 400 Nm 3 / h was supplied to the additional injector as primary gas, and powdered coal in an amount of about 100 - 700 kg / h was mixed as an additional reducing agent when appropriate. The average particle size of the powdered coal was 120 μm. The pressure of the compressed gas upstream of the second immersion type injector assembly was 6 bar gauge.

[0204] The gas velocity in the combination of the additional injector and tuyere was typically higher than 150 m / s during operation.

[0205] First process stage: Liquid filling of the furnace: Except for the following exceptions, the same procedure, quality, and amount were used for this process as part of Example 1.

[0206] The flow of secondary gas through a single additional tuyere as part of the combination of a single additional injector and the tuyere was set to air at 350 Nm 3 / h, and no natural gas was added. The flow of primary gas through an additional injector as part of the combination of a single additional injector and the tuyere was set to air at 200 Nm 3 / h. At this process stage, the fine coke injection was not yet activated.

[0207] Second process stage: Fuming process The same procedure as in Example 1 was applied.

[0208] The PG was set again to a power level of 2500 kW each, and the average primary air flow per PG was set to 714 Nm 3 / h. In addition, the following secondary gases were used. Natural gas was added to each of the tuyeres downstream of the PG at a rate of 148 Nm 3 / h. The additional air flow through the tuyere was set to 100 Nm 3 / h.

[0209] The secondary gas flow through an additional tuyere as part of the combination of a single additional injector and the tuyere was air at 350 Nm 3 / h, and no natural gas was added. As the primary gas, the flow through an additional injector as part of the combination of an additional injector and the tuyere was set to air at 200 Nm 3 / h. At this process stage, the fine coke injection was set to 700 kg / h.

[0210] The temperature inside the reactor was maintained in the range of 1180 - 1250 °C to ensure that the slag remained fluid. Thanks to the various reductants, namely powdered coal, and the various inputs of natural gas, ZnO was reduced to metallic zinc (Zn). Thus, Zn evaporated from the slag bath and was transported from the furnace to the flue gas treatment facility as part of the process gas.

[0211] Samples were taken during fuming and analyzed by XRF, a method that is fast but slightly less accurate. When the desired Zn level was reached in the slag in the furnace, fuming was stopped and the trimming process was started.

[0212] Third process step: Trimming The target temperature was again 1220 - 1250 °C.

[0213] The PGs were operated continuously at an average air flow of 714 Nm 3 / h per PG at an output level of 2500 kW each. In addition, the following secondary gases were used. The natural gas flow through the tuyere was set to 102 Nm 3 / h. The air flow through the tuyere was set to 100 Nm 3 / h.

[0214] The secondary gas flow through an additional tuyere, which was part of a combination of a single additional injector and the tuyere, was set to 350 Nm 3 / h of air and no natural gas was added. The primary gas flow through an additional injector, which was part of a combination of a single additional injector and the tuyere, was set to 200 Nm 3 / h of air. At this process step, fine coke injection was not yet operating.

[0215] No slag samples were taken after the completion of the trimming process. Tapping was started immediately.

[0216] Fourth process step: Slag tapping and granulation The same procedure as in Example 1 was applied.

[0217] The PGs were again operated continuously at an average primary air flow of 606 Nm 3 / h per PG at a power level of 2000 kW each during this tapping and granulation process. As secondary gases, a natural gas flow of 128 Nm 3 / h to the tuyere and a direct air flow of 100 Nm 3 / h to the tuyere were used.

[0218] The flow of secondary gas through a single additional tuyere as part of a further injector and tuyere combination was 350 Nm 3 / h of air and no natural gas was added. The primary gas flow through the additional injector as part of a single additional injector and tuyere combination was set to 200 Nm 3 / h of air. At this process stage, fine coke injection was not yet operating.

[0219] Samples of the final product after granulation were taken. The composition is thought to be close to that of the slag immediately after the fuming process.

[0220] The further operating parameters of PG at each process stage were the same as those shown in Table II as part of Example 1.

[0221] The final result of this example was very similar to the result of Example 1 but was obtained again in a shorter time than the batch carried out for comparison as part of Example 1.

[0222] The Applicants have found that using the embodiments according to the present invention and also using Example 2, a significant increase in production rate can be established. The Applicants believe that this effect is due to a combination of (i) higher bath stirring, (ii) more stripping gas, (iii) more reducing agent, and perhaps most importantly, (iv) the use of a solid reducing agent with a much smaller particle size such that the reducing agent is much more reactive. This effect enables reaching the target fuming operating conditions much faster compared to coarse petroleum coke. By combining beneficial effects, the fuming process becomes much faster in full operation, as indicated by a much faster increase in heat that needs to be removed from the post-combustion zone, and the time required could be shortened from about a quarter of an hour to about 2 - 3 minutes, so that the time of the trimming process could be extremely significantly shortened by almost an order of magnitude. The fuming furnace equipped with the second immersion type injector could be operated more stably, at a higher throughput, and closer to the maximum of its capacity.

[0223] Although the present invention has been fully described so far, it will be understood by those skilled in the art that the present invention can be implemented within a wide range of parameters within the scope of the present invention defined by the claims without departing from the scope of the present invention. (Disclosure of the Invention) (Item 1) A single-chamber furnace for fuming at least one evaporable metal or metal compound from a metallurgical charge, comprising a bath furnace capable of accommodating a molten charge up to a determined height, the furnace comprising at least one non-transfer type plasma torch for generating a first hot gas of plasma quality, and at least one first immersion type injector for injecting the first hot gas from the plasma torch below the determined height, the furnace further comprising a post-combustion zone for oxidizing the at least one evaporable metal or metal compound in the fuming gas to form an oxidized form of the at least one evaporable metal or metal compound, and a recovery zone for recovering the oxidized form of the at least one evaporable metal or metal compound from the gas formed in the post-combustion zone, the furnace further comprising at least one second immersion type injector, different from the first immersion type injector, for injecting additional gas into the furnace below the determined height. (Item 2) The apparatus is equipped to inject, through the at least one second injector, a total amount of additional gas that is at least 10% of the amount of the first hot gas that can be generated by the single element of the at least one plasma torch having a maximum power rating when the plasma torch supplies a first hot gas having an enthalpy amount of at least 3.5 kWh / Nm in volume units under standard conditions. 3 The furnace according to item 1. (Item 3) Equipped with a plurality of second injectors, each injector being equipped to inject, through each second injector, an amount of additional gas that is at least 10% of the amount of the first hot gas that can be generated by the single element of the at least one plasma torch having a maximum power rating when the plasma torch supplies a first hot gas having an enthalpy amount of at least 3.5 kWh / Nm in volume units under standard conditions. 3 The furnace according to item 1 or 2. (Item 4) The furnace according to any one of items 1 to 3, connected to at least one source of compressed gas and / or equipped with a compressor for supplying compressed gas to the at least one second injector. (Item 5) The source of the additional gas to the apparatus is a gas source selected from the group consisting of hydrogen, nitrogen, air, carbon dioxide, argon, neon, helium, methane, ethane, propane, butane, and combinations thereof, preferably a nitrogen or air source, more preferably an air source, and even more preferably a compressed air source, the furnace according to any one of items 1 to 4. (Item 6) Means for heat-treating the additional gas to change its enthalpy amount upstream of the at least one second injector, preferably means for heat-treating the additional gas including at least one heat exchanger, the furnace according to any one of items 1 to 5. (Item 7) The furnace according to any one of items 1 to 6, further equipped with means for introducing a reducing agent into the additional gas upstream of the at least one second injector. (Item 8) The furnace according to item 7, wherein the reducing agent to be introduced can be selected from gases, liquids, solids, and combinations thereof. (Item 9) The furnace according to any one of items 1 to 8, comprising means for controlling the lambda of the additional gas injected into the bath by the second injector. (Item 10) For injecting as part of the oxygen and gaseous or liquid fuel of the additional gas, and for making the velocity of the additional gas at another position in or upstream of the at least one second injector faster than the flame propagation velocity of the fuel as part of the additional gas, the furnace according to any one of items 1 to 9. (Item 11) The combustion of the injected fuel under the intended operating conditions of the furnace results in an increase in the enthalpy of the additional gas, whereby the temperature of the additional gas at the injection point into the bath is at most the temperature of the molten charge intended to be in the furnace during operation, the furnace according to item 10, further equipped with means for limiting the amount of the injected fuel. (Item 12) The at least one second injector directs its additional gas to a second volume that is part of the internal space of the furnace below the predetermined height, which is different from the first volume towards which the at least one first injector directs the first hot gas of the plasma quality, the furnace according to any one of items 1 to 11. (Item 13) The at least one first injector is arranged on the side wall of the furnace, and the at least one second injector is arranged on the furnace wall opposite to the at least one first injector, preferably along the horizontal outer periphery of the furnace extending at substantially the same height as the at least one first injector. The furnace according to any one of items 1 to 12. (Item 14) Comprising at least two, preferably at least three, first injectors distributed along the horizontal outer periphery of the furnace side wall, and the at least one second immersion type injector directs its additional gas towards a volume as part of the internal space of the furnace below the predetermined height substantially close to the vertical axis of the furnace, and / or the at least one second immersion type injector is arranged along the furnace side wall at substantially equal distances between the two closest positions among the at least two first injectors. The furnace according to any one of items 1 to 13. (Item 15) The furnace according to any one of items 1 to 14, further equipped for introducing a reducing agent into the first hot gas upstream of the at least one first injector. (Item 16) The furnace according to item 15, wherein the reducing agent introduced upstream of the at least one first injector can be selected from gases, liquids, solids, and combinations thereof. (Item 17) The furnace according to any one of items 1 to 16, further equipped with at least one oxy-gas burner for generating additional first hot gas exceeding the amount of the first hot gas of the plasma quality from the at least one plasma torch. (Item 18) The furnace according to item 17, further equipped with at least one immersion type third injector for injecting the additional first hot gas below the determined height. (Item 19) The furnace according to item 18, wherein the at least one oxy-gas burner is arranged below the determined height. (Item 20) The furnace according to any one of items 1 to 19, wherein the plasma torch is arranged below the determined height. (Item 21) The furnace according to any one of items 1 to 20, wherein the afterburning zone is provided above the determined height as part of the single-chamber furnace. (Item 22) The furnace according to any one of items 1 to 21, wherein the post-combustion zone preferably comprises a connection portion with a source of an oxygen-containing gas selected from air, oxygen-enriched air, and purified oxygen gas. (Item 23) The furnace according to any one of items 1 to 22, further comprising a cooling zone upstream of the recovery zone for cooling the gas formed in the post-combustion zone. (Item 24) The furnace according to any one of items 1 to 23, wherein the recovery zone comprises a gas filtration zone, and preferably the gas filtration zone comprises at least one gas filtration cloth. (Item 25) The furnace according to any one of items 1 to 24, wherein the furnace has a substantially cylindrical shape, preferably the furnace also has a conical lower part that tapers towards a small-diameter cylindrical bottom, the cylindrical shape of the furnace has a maximum inner diameter d, the furnace has an overall inner height h from the bottom to the top, and the ratio of h to d is at least 0.75. (Item 26) The furnace according to item 25, wherein the furnace comprises the conical lower part, and the determined height is approximately the height at which the cylindrical shape changes to the conical lower part. (Item 27) The furnace according to any one of items 1 to 26, wherein the furnace is provided with an inner refractory lining. (Item 28) The furnace according to any one of items 1 to 27, wherein the outer peripheral wall of the furnace is water-cooled. (Item 29) A method of fuming at least one evaporable metal or metal compound from a metallurgical charge using the furnace according to any one of items 1 to 28, comprising the following steps: · Introducing the metallurgical charge containing the at least one evaporable metal or metal compound into the furnace to form a bath of molten charge up to the determined height; · Fuming a certain amount of at least one evaporable metal or metal compound from the bath using a hot gas of plasma quality from at least one plasma torch and at least one reducing agent, thereby generating a fuming gas containing the evaporable metal or metal compound; · Post-combusting the fuming gas in the post-combustion zone to oxidize the at least one evaporable metal or metal compound to its oxidized form; · Extracting the gas formed in the furnace from the furnace and recovering the oxidized form of the at least one evaporable metal or metal compound from the gas formed in the post-combustion step; comprising, during at least a part of said fuming step, additional gas is injected into said bath below said determined height by said at least one second injector, thereby increasing the amount of fumes containing said evaporable metal or metal compound, a method characterized thereby. (Item 30) the amount of additional gas injected through said at least one second injector is at least 10% of the amount of the first hot gas that can be generated by said single element of said at least one plasma torch having the highest power rating when the plasma torch is supplying a first hot gas having an enthalpy amount of at least 3.5 kWh / Nm 3 in terms of volume under standard conditions, the method according to item 29. (Item 31) said furnace comprises a plurality of second injectors, and the amount of additional gas injected through each second injector is at least 10% of the amount of the first hot gas that can be generated by said single element of said at least one plasma torch having the highest power rating when the plasma torch is supplying a first hot gas having an enthalpy amount of at least 3.5 kWh / Nm 3 in terms of volume under standard conditions, the method according to any one of items 29 to 30. (Item 32) said additional gas injected through said at least one second injector comprises at least one gas selected from the group consisting of hydrogen, nitrogen, air, carbon dioxide, argon, neon, helium, methane, ethane, propane, butane, and combinations thereof, preferably nitrogen or air, more preferably air, even more preferably compressed air, the method according to any one of items 29 to 31. (Item 33) said additional gas injected through said at least one second injector is heat-treated upstream of said at least one second injector to change its enthalpy amount, preferably, said heat treatment of said additional gas is carried out by using at least one heat exchanger, the method according to any one of items 29 to 32. (Item 34) the temperature of said additional gas entering said at least one second injector is at most equal to the temperature of said bath in said furnace, preferably at least 100 degrees Celsius lower than the temperature of said bath, the method according to any one of items 29 to 33. (Item 35) The method according to any one of items 29 to 34, wherein the additional gas injected through the at least one second injector contains at least one first reducing agent. (Item 36) The method according to item 35, wherein the first reducing agent is solid. (Item 37) The method according to any one of items 29 to 36, wherein the additional gas injected through the at least one second injector further contains oxygen and fuel, and the amount of the fuel is such that, by its combustion under the operating conditions in the furnace, it provides an enthalpy input to the furnace that compensates for at least 50% of the cooling effect that the additional gas can bring to the furnace when the additional gas is at the injection point at a temperature lower than the temperature of the molten charge in the furnace. (Item 38) The method according to any one of items 29 to 38, wherein the additional gas injected through the at least one second injector has a lambda of less than 1.0. (Item 39) The method according to any one of items 29 to 38, wherein the additional gas injected through the at least one second injector is combustible and reaches a speed higher than the flame propagation speed of the additional gas within the at least one second injector. (Item 40) The method according to any one of items 29 to 39, wherein the at least one evaporable metal or metal compound is a metal in its elemental form or an evaporable metal-containing compound, preferably the metal is selected from the group consisting of zinc, lead, tin, bismuth, cadmium, indium, germanium, and combinations thereof, and more preferably the metal-containing compound is selected from chlorides, oxides, sulfides, and combinations thereof. (Item 41) The method according to item 40, wherein a metal less noble than the metal in the evaporable metal or metal compound, preferably iron and / or aluminum, is added to the furnace. (Item 42) The method according to any one of items 29 to 41, wherein the second reducing agent is added to the first hot gas of the plasma quality upstream of the at least one first injector. (Item 43) The method according to item 42, wherein the second reducing agent is selected from gases, liquids, and solids, and combinations thereof. (Item 44) The oxygen potential in the slag is 10 to 10 -9 The method according to any one of items 29 to 43, including a step of adjusting within the range of Pa. (Item 45) The method according to any one of items 29 to 44, wherein the afterburning is carried out inside the single-chamber furnace. (Item 46) The method according to any one of items 29 to 45, wherein the afterburning preferably includes introducing an oxygen-containing gas selected from air, oxygen-enriched air, and purified oxygen gas into the afterburning zone. (Item 47) The method according to any one of items 29 to 45, wherein the oxidized form of the at least one evaporable metal or metal compound is recovered from the gas as dust. (Item 48) The method according to any one of items 29 to 47, wherein the recovery of the oxidized form of the at least one evaporable metal or metal compound from the gas includes filtering the gas containing the oxidized form of the at least one evaporable metal or metal compound using a filter, preferably a filter cloth. (Item 49) The method according to any one of items 29 to 48, further including a cooling step upstream of the recovery of the oxidized form of the at least one evaporable metal or metal compound from the gas. (Item 50) The method according to any one of items 29 to 49, including the formation of a molten metal phase, and further including a step of removing the molten metal phase from the furnace. (Item 51) The method according to any one of items 29 to 50, wherein the metal charge includes slag, the slag includes sulfur and / or sulfur compounds, and the method further includes a step of forming a molten matte phase and a further step of removing the molten matte phase from the furnace. (Item 52) The method according to any one of items 29 to 51, wherein the metallurgical charge is introduced into the furnace as a liquid. (Item 53) The method according to any one of items 29 to 52, wherein the metallurgical charge is metallurgical slag and the method produces a second slag. (Item 54) The method according to item 53, wherein the molten slag has an average temperature less than 50 degrees Celsius higher than the liquidus temperature of the slag. (Item 55) CaO, Al 2 O 3 , and oxides selected from combinations thereof are added to the bath in the furnace, preferably to the bath at a temperature of at least 1000°C, preferably about 1150°C. The method according to any one of items 53 to 54. (Item 56) The method according to any one of items 53 to 55, further comprising the step of cooling the second slag to a solid, preferably the second slag being first removed from the furnace as a liquid. (Item 57) The method according to item 56, wherein the cooling is performed by bringing the liquid second slag into contact with water. (Item 58) The method according to any one of items 56 to 57, wherein the second slag is cooled at a rate of at least 30 degrees Celsius per second. (Item 59) The method according to any one of items 56 to 58, further comprising the step of pulverizing the solid second slag, preferably the step of pulverizing the second slag into powder. (Item 60) The method according to any one of items 56 to 59, wherein the second slag is cooled at a rate of less than 40 degrees Celsius per second. (Item 61) The method according to any one of items 56 to 60, further comprising the step of adding the second slag as a binder or aggregate during the manufacture of an object for the construction industry. (Item 62) The method according to item 61, wherein the slag is used as a binder, the object further comprises an aggregate, and the aggregate preferably comprises sand and / or the second slag. (Item 63) The method according to item 62, further comprising adding an activator during the manufacture of the object. (Item 64) The activator is selected from the group consisting of sodium hydroxide, NaOH, potassium hydroxide, KOH, sodium silicate, Na 2 SiO 3 , potassium silicate, K 2 SiO 3 , and combinations thereof, according to the method of item 63. (Item 65) The method according to any one of items 61 to 64, wherein the object for the construction industry is a building element. (Item 66) The method according to item 65, wherein the building element is selected from the list of tiles, pavers, blocks, concrete blocks, and combinations thereof. (Item 67) The method according to any one of items 61 to 66, wherein the object for the construction industry has a foamed structure. (Item 68) Use of the furnace according to any one of items 1 to 28 for fuming at least one evaporable metal or metal compound from a metallurgical charge. (Item 69) The use of the furnace according to item 68, wherein the metallurgical charge is selected from copper smelting slag and copper refining slag and combinations thereof. (Item 70) Use according to any one of items 68 to 69, wherein the evaporable metal or metal compound is selected from zinc, lead, tin, bismuth, cadmium, indium, germanium, and combinations thereof. (Item 71) The method according to any one of items 29 to 67, wherein at least part of the method is preferably electronically monitored and / or controlled by a computer program.

Claims

1. A single-chamber furnace for fuming at least one evaporable metal or metal compound from a metallurgical charge, comprising a bath furnace capable of accommodating a molten charge up to a determined height, wherein the furnace, comprises at least one non-transfer type plasma torch for generating a first hot gas of plasma quality, and at least one first immersion type injector located below the determined height, the at least one first immersion type injector for injecting the first hot gas from the at least one plasma torch, wherein the furnace, further comprises a post-combustion zone for oxidizing the at least one evaporable metal or metal compound in the fuming gas to form an oxidized form of the at least one evaporable metal or metal compound, a cooling zone for cooling the gas formed in the post-combustion zone, and a recovery zone downstream of the cooling zone for recovering the oxidized form of the at least one evaporable metal or metal compound from the gas formed in the post-combustion zone and cooled in the cooling zone, wherein the furnace, further comprises at least one second immersion type injector located below the determined height, different from the at least one first immersion type injector, for injecting additional gas into the furnace in addition to the amount of the first hot gas of plasma quality generated during operation by the at least one non-transfer type plasma torch and injected from the at least one first immersion type injector. The single-chamber furnace is characterized by this.

2. The furnace according to claim 1, wherein the at least one second injector directs the additional gas to a second volume which is part of the internal space of the furnace below the determined height and different from the first volume towards which the at least one first injector directs the first hot gas of plasma quality.

3. The furnace comprises at least two first injectors distributed along the horizontal outer periphery of the furnace sidewall, and the furnace has a vertical axis extending in the height direction through the center of the horizontal outer periphery of the furnace sidewall. The at least one second submerged injector directs its additional gas towards a volume that is part of the interior space of the furnace below the determined height close to the vertical axis of the furnace, and / or the at least one second submerged injector is arranged along the furnace sidewall at approximately equal distances between the two closest positions of the at least two first injectors. The furnace according to claim 1 or 2.

4. The cooling zone includes a radiant water cooler and a spray cooler following it. The furnace according to any one of claims 1 to 3.

5. The recovery zone comprises a gas filtration zone. The furnace according to any one of claims 1 to 4.

6. A method of fuming at least one evaporable metal or metal compound from a metallurgical charge using the furnace according to any one of claims 1 to 5, comprising the following steps: - Introducing the metallurgical charge containing the at least one evaporable metal or metal compound into the furnace to form a bath of molten charge up to the determined height; - Fuming a quantity of at least one evaporable metal or metal compound from the bath using hot gas of plasma quality from at least one plasma torch and at least one reducing agent, thereby generating a fuming gas containing the evaporable metal or metal compound; - Afterburning the fuming gas in the afterburning zone to oxidize the at least one evaporable metal or metal compound to its oxidized form; - Extracting the gas formed in the furnace from the furnace and recovering the oxidized form of the at least one evaporable metal or metal compound from the gas formed in the afterburning step in the recovery zone; including During at least part of the fuming step, additional gas is injected into the bath below the determined height by the at least one second injector, thereby increasing the amount of fume containing the evaporable metal or metal compound. A method characterized by this.

7. The furnace includes a plurality of second injectors, and the amount of additional gas injected through each second injector is at least 3.5 kWh / Nm ３ of the enthalpy amount of the first hot gas having a first hot gas supplied by a single element of the at least one plasma torch having a maximum power rating, at least 10% of the amount of the first hot gas that can be generated, according to claim 6 of the method described.

8. The additional gas injected through the at least one second injector is heat-treated upstream of the at least one second injector to change its enthalpy amount. The method according to claim 6 or 7. Claim 9 The method according to any one of claims 6 to 8, wherein the additional gas injected via the at least one second injector contains at least one first reducing agent. Claim 10 The method according to any one of claims 6 to 9, wherein the at least one evaporable metal or metal compound is a metal in its elemental form or an evaporable metal-containing compound. Claim 11 The method according to any one of claims 6 to 10, wherein the oxidized form of the at least one evaporable metal or metal compound is recovered from the gas as dust. Claim 12 The method according to any one of claims 6 to 11, wherein the metallurgical charge is a metallurgical slag as a first slag, and the method produces a second slag as a product of a process for fuming the first slag. Claim 13 The method according to claim 12, further comprising a step of cooling the second slag to make it solid. Claim 14 The method according to claim 13, further comprising a step of adding the second slag as a binder or aggregate during the manufacture of an object for the construction industry. Claim 15 Use of a furnace according to any one of claims 1 to 5 for fuming at least one evaporable metal or metal compound from a metallurgical charge.

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