Method and apparatus for processing material

Abstract

The present invention provides a method and apparatus for treating a material that is an upper layer from a metal smelting process, the material comprising one or more salts, the material comprising one or more metals. The method includes feeding the material into a size reduction step; feeding the material from the size reduction step to a density-based separation step; the material is passed from a density-based separation step to a leaching step. Wherein the size reduction stage is optimized to provide material exposure for the separation of ferrous metals and non-ferrous metals, the separation of ferrous metals being preferably provided by a vortex separator and the separation of non-ferrous metals being preferably provided by a cyclone separator.

Description

This application is a divisional application of the invention application with the application date of November 27, 2017, application number 201780072400.5, and name “Processing method and processing device and related improvements”.

[0001] The present invention relates to treatment methods and apparatus and improvements relating thereto, and in particular to treatment methods and apparatus for treating slag to recover one or more useful components thereof.

[0002] For example, a furnace that processes molten aluminum is provided with a salt barrier on top of the molten metal to reduce oxidation and / or facilitate removal of contaminants from the molten metal. Due to this process, the salt barrier effectively becomes part of the slag, after which it is often referred to as salt slag. Once removed from the furnace, the handling of this material is advantageous. Advantages include recovery and reuse of one or more components and / or reduction of hazards presented by the slag.

[0003] Existing methods tend to use centralized processing plants to capture cold slag and reprocess it. This creates transportation issues in terms of cost and transportation footprint, and has a negative impact on subsequent processing and products.

[0004] One of the possible objects of the invention is to facilitate the processing of slag, economically carried out at the same place where it is produced. One of the possible objects of the invention is to reduce the costs involved in the processing. One of the potential objects of the invention is to provide a product that may be improved in its value and / or usefulness.

[0005] According to a first aspect, there is provided a method of processing a material, the method comprising: a) sending the material to a leaching step; b) obtaining a leachate from the leaching step; c) sending the leachate to a drying step or a spray drying step; d) A solid will be obtained from the drying step or the spray drying step.

[0006] The method may comprise the further step of compressing and / or moulding the solid into pellets.

[0007] The method may comprise 1) providing material on a surface of molten metal in a furnace, the furnace being at a first location; 2) removing the material from the furnace; 3) treating the material removed from the furnace at a second location, the second location being 5 km or closer to the first location, and the treatment comprising one or more of steps a), b), c) or d). The method may comprise applying one or more of the steps at the second location before the temperature of the material removed from the furnace has been reduced to below 100°C, preferably below 350°C, more preferably below 525°C, and even more preferably below 760°C.

[0008] According to a second aspect, there is provided an apparatus for processing a material, the apparatus comprising: a) Leaching device; b) a feeder for providing material to the leaching device; c) the outlet of the leachate from the leaching device; d) dryer or spray dryer; e) the outlet is fluidly connected to a spray dryer; f) The outlet of the dryer or spray dryer for solids.

[0009] The device may comprise a compression and / or moulding device for producing pellets and / or a feeder for supplying the compression and / or moulding device with solids obtained from the leachate.

[0010] The apparatus may include: 1) a furnace at a first location; 2) a feeder for introducing material to the surface of the molten metal in the furnace; 3) one or more processors for the material removed from the furnace, the one or more processors being provided at a second location that is 5 km or closer to the first location, and the one or more processors including one or more processors having one or more of features a), b), c), d), e) or f).

[0011] According to a third aspect, there is provided a method for processing a material, the method comprising: a) sending the material to a leaching step; b) obtaining a leachate from the leaching step; c) obtaining solids from the leachate; d) Compressing and / or molding the solid into pellets.

[0012] The method may comprise sending the percolate to a drying step or a spray drying step, preferably to obtain a solid for a compression and / or moulding step.

[0013] The method may comprise 1) providing material on a surface of molten metal in a furnace, the furnace being at a first location; 2) removing the material from the furnace; 3) treating the material removed from the furnace at a second location, the second location being 5 km or closer to the first location, and the treating comprising one or more of steps a), b), c) or d). The method may comprise applying one or more of the steps at the second location before the temperature of the material removed from the furnace has been reduced to below 100°C, preferably below 350°C, more preferably below 525°C, and even more preferably below 760°C.

[0014] According to a fourth aspect, there is provided an apparatus for processing a material, the apparatus comprising: a) Leaching device; b) a feeder for providing material to the leaching device; c) the outlet of the leachate from the leaching device; d) solid compression and / or molding devices for forming pellets; e) A feeder for supplying the compression and / or moulding device with solids obtained from the leachate.

[0015] The apparatus may comprise a dryer or a spray dryer, and / or the outlet may be fluidly connected to the dryer or the spray dryer, and / or an outlet for solids of the dryer or the spray dryer.

[0016] The apparatus may include: 1) a furnace at a first location; 2) a feeder for introducing material to the surface of the molten metal in the furnace; 3) one or more processors for the material removed from the furnace, the one or more processors being provided at a second location that is 5 km or closer to the first location, and the one or more processors including one or more processors having one or more of features a), b), c), d) or e).

[0017] According to a fifth aspect, there is provided a method for processing a material, the method comprising: a) providing a material on a surface of molten metal in a furnace, the furnace being in a first position; b) removing the material from the furnace; c) processing the material removed from the furnace at a second location that is 5 km or less from the first location and the processing comprises one or more steps selected from: 1) Reduce the size of a large amount of the material; 2) leaching the material to provide a leachate; 3) drying or spray drying one or more components, such as the leachate, to provide a solid; 4) Compressing or moulding solids, such as those obtained from the leachate, to provide pellets.

[0018] The method may comprise applying one or more of the steps at a second location before the temperature of the material being removed from the furnace has dropped below 100°C, preferably below 350°C, more preferably below 525°C, even more preferably below 760°C.

[0019] The method may comprise sending the percolate to a drying step or a spray drying step, preferably to obtain a solid for the compression and / or moulding step.

[0020] The method may comprise the further step of compressing and / or moulding the solid into pellets.

[0021] According to a sixth aspect, there is provided an apparatus for processing a material, the apparatus comprising: a) a furnace, the furnace being in a first position; b) a feeder for introducing material to the surface of the molten metal in the furnace; c) one or more processors for the material removed from the furnace, the one or more processors being provided at a second location, the second location being 5 km or less from the first location, and the one or more processors comprising one or more processors selected from: 1) a crusher for reducing the size of large quantities of the material; 2) Leaching device; 3) Drying or spray drying step device; 4) Devices for compression or moulding of solids, for example obtained from the leachate from a leaching device, to provide pellets.

[0022] According to a seventh aspect, there is provided a method for processing a material, the method comprising: a) sending the material to a leaching step; b) obtaining material from the leaching step; c) passing the material from the leaching step to a filtration step; d) sending the solid material from the filtration step to a drying step.

[0023] The method may comprise the further step of compressing and / or moulding the solid into pellets.

[0024] The method may comprise 1) providing material on a surface of molten metal in a furnace, the furnace being at a first location; 2) removing the material from the furnace; 3) treating the material removed from the furnace at a second location, the second location being 5 km or closer to the first location, and the treatment comprising one or more of steps a), b), c) or d). The method may comprise applying one or more of the processes at the second location before the temperature of the material removed from the furnace has been reduced to below 100°C, preferably below 350°C, more preferably below 525°C, and even more preferably below 760°C.

[0025] According to an eighth aspect, there is provided an apparatus for processing a material, the apparatus comprising: a) a feeder providing material to the leaching device; b) Leaching device; c) the outlet of the material from the leaching device to the filtration device; d) Filtering device; e) Feeder from the filter unit to the dryer; f) Dryer.

[0026] The device may comprise a compression and / or moulding device for producing pellets and / or a feeder for supplying the compression and / or moulding device with solids obtained from the leachate.

[0027] The apparatus may include: 1) a furnace at a first location; 2) a feeder for introducing material to the surface of the molten metal in the furnace; 3) one or more processors for the material removed from the furnace, the one or more processors being provided at a second location that is 5 km or closer to the first location, and the one or more processors including one or more processors having one or more of features a), b), c), d), e) or f).

[0028] According to a ninth aspect, there is provided a method for processing a material, the method comprising: a) feeding the material to a size reduction step; b) feeding the material from the size reduction step to a density-based separation step; c) Feeding material from the density based separation step to a leaching step.

[0029] The method may comprise the further step of compressing and / or moulding the solid into pellets.

[0030] The method may comprise 1) providing material on a surface of molten metal in a furnace, the furnace being at a first location; 2) removing the material from the furnace; 3) treating the material removed from the furnace at a second location, the second location being 5 km or closer to the first location, and the treatment comprising one or more of steps a), b), c) or d). The method may comprise applying one or more of the steps at the second location before the temperature of the material removed from the furnace has been reduced to below 100°C, preferably below 350°C, more preferably below 525°C, and even more preferably below 760°C.

[0031] According to a tenth aspect, there is provided an apparatus for processing a material, the apparatus comprising: a) a feeder providing material to the size reduction device; b) size reduction devices; c) a feeder providing material to a density-based separation device; d) Density-based separation devices; e) a feeder for providing material to the leaching device; f) Leaching device.

[0032] The device may comprise a compression and / or moulding device for producing pellets and / or a feeder for supplying the compression and / or moulding device with solids obtained from the leachate.

[0033] The apparatus may include: 1) a furnace at a first location; 2) a feeder for introducing material to the surface of the molten metal in the furnace; 3) one or more processors for the material removed from the furnace, the one or more processors being provided at a second location that is 5 km or closer to the first location, and the one or more processors including one or more processors having one or more of features a), b), c), d), e) or f).

[0034] The first and / or second and / or third and / or fourth and / or fifth and / or sixth and / or seventh and / or eighth and / or ninth and / or tenth aspect of the present invention may include any feature, option or possibility listed elsewhere herein, including the features, options or possibilities below.

[0035] The treatment process may be a treatment to separate one or more salts from one or more metals. For example, sodium chloride and / or sodium chlorate and / or potassium chloride and / or potassium chlorate may be separated, in particular from aluminum and / or ferrous metals.

[0036] The treatment process may be a treatment to separate one or more salts from one or more non-metals. For example, sodium chloride and / or sodium chlorate and / or potassium chloride and / or potassium chlorate may be separated, in particular from aluminum oxide and / or other insoluble non-metal compounds.

[0037] The method may provide for the recovery of one or more metals (e.g., aluminum).The method may provide for the recovery of one or more salts (e.g., sodium chloride and / or potassium chloride).

[0038] The material may be slag. The material may be an upper layer from a metal melting process. The material may be a layer involving the recovery of aluminum. The material may include one or more salts, such as sodium chloride and / or sodium chlorate and / or potassium chloride and / or potassium chlorate. The material may include one or more metals, such as aluminum, and / or metal oxides, such as aluminum oxide. The material may include 10-35% aluminum oxide, 25-60% sodium chloride, 10-35% potassium chloride, 2-10% metallic aluminum and impurities, the combination totaling 100%, such as 15-30% aluminum oxide, 30-55% sodium chloride, 15-30% potassium chloride, 5-7% metallic aluminum and impurities, the combination totaling 100%. Impurities may include carbides, nitrides, sulfides and / or phosphides.

[0039] The method of providing material on the surface of molten metal in a furnace may comprise feeding material onto the surface of the molten metal, preferably from above the molten metal. The material may be fed in batches. The material may be fed in continuously.

[0040] The molten metal is preferably aluminium.

[0041] The furnace may be a rotary furnace or other furnace type.

[0042] The first location may be a location where the furnace is provided, and / or a location where the material is stored after being taken out of the furnace and / or after being compressed.

[0043] The material may be slag. The material may be compressed slag produced by compressing slag. The slag may be compressed in a slag press. The slag may be compressed to remove molten aluminum from the slag. The material may include one or more salts, such as sodium chloride and / or sodium chlorate and / or potassium chloride and / or potassium chlorate. The material may include one or more metals, such as aluminum, and / or metal oxides, such as aluminum oxide, ideally at a lower content than that in the slag.

[0044] The compressed slag may have a lower temperature than the slag. The temperature of the compressed slag after compression may be below 500°C.

[0045] The compressed slag may be allowed to cool. Preferably, the compressed slag is not allowed to cool below 100°C, preferably below 350°C, more preferably below 525°C, even more preferably below 760°C.

[0046] The compressed slag may be allowed to cool in the first location.

[0047] The second location may process less than 20,000 tons of material per year, possibly less than 15,000 tons of material per year, or even less than 10,000 tons of material per year.

[0048] The processing of the material removed from the furnace provided at the second location may include one or more steps after the material is removed from the furnace, and more preferably includes after compression of the material, such as forming compressed slag.

[0049] The second location is 5km or closer to the first location, and preferably less than 2km from the first location, more preferably less than 1km from the first location and ideally less than 500m from the first location. The first location and the second location are preferably owned and / or operated by the same legal entity. The furnace is preferably supplied to recover aluminium.

[0050] Preferably, the compressed slag is not allowed to cool below 100°C, preferably below 350°C, more preferably below 525°C, even more preferably below 760°C before one or more process steps are performed at the second location.

[0051] The method may include a size reduction step. The size reduction step may reduce one or more dimensions of the material and / or increase the number of discrete portions in which the material exists. The size reduction step may include multiple size reduction steps. The size reduction step may include a crushing step. The size reduction step may include a jaw crusher. The size reduction step may include a grinding step. The size reduction step may include a rolling step. The size reduction step may include one or more sizing steps, for example to separate the material into one or more portions according to size. The size reduction step may generate a flat bed of material, for example to separate or expose ferrous metals for separation. The size reduction step may generate a flat bed of material that can be easily suspended in an air stream, for example for feeding into a cyclone separator.

[0052] The method may include a ferrous and non-ferrous metal separation step. The separation may be performed by an eddy current separator. The method may include a metal and non-metal separation step. The separation may be performed by an eddy current separator and / or a vibrating table and / or a compressed air separator. The aluminum extracted by one or both of these separations may be returned to the furnace.

[0053] The method may include a density-based separation step. The density-based separation step may use a cyclone separator, particularly an air-based cyclone separator. The density-based separation step may remove one or more gas generating components from the material fed to the leaching step. The density separation step may separate aluminum and / or aluminum-containing components from other components, particularly salt components.

[0054] The method may comprise feeding the material to a leaching step by introducing the material into a leaching tank. The leaching step may be provided with one or more other feeds, such as water. The leaching step may be provided with hydrogen peroxide. Hydrogen peroxide may be used to increase the oxide content and / or reduce or remove the nitride content and / or calcides content.

[0055] The method may include obtaining a leachate from one or more leaching steps.

[0056] The leaching step may be a multi-pass leaching process, which provides multiple passes through one leaching tank, and / or a multi-stage leaching process, which provides passes through several leaching tanks.

[0057] The residence time in the leaching stage may be less than 10 min, preferably less than 8 min, and ideally less than 5 min or less.The residence time may be controlled to control the volume of gas produced by the leaching step.

[0058] The method may comprise obtaining leachate from one or more leaching steps by extracting the leachate from a leaching tank, preferably from the bottom thereof.The leaching steps may be provided with one or more other outlet streams, such as a waste gas stream and / or an undissolved solids stream.

[0059] The exhaust gas stream may be further processed, for example by combustion, with the heat and / or power generated desirably being used in one or more of the process steps, desirably in a drying step or a spray drying step.

[0060] The undissolved solids and dissolved solids may be fed to a solid-liquid separator, such as a filter. All materials leaving the leaching step, except the exhaust gases, may be fed to a solid-liquid separator. Before being fed to the solid-liquid separator, the undissolved solids and dissolved solids may be fed to a mixer, such as a ribbon blender. Before being fed to the solid-liquid separator, all materials leaving the leaching step, except the exhaust gases, may be fed to a mixer, such as a ribbon blender. The mixer may allow the undissolved solids to be evenly distributed among the dissolved solids, possibly along with additional water, before being fed to the solid-liquid separator.

[0061] The solid-liquid separator may be a filter, particularly a belt filter, more preferably a vacuum belt filter. A dissolved solids stream may be drawn through the bed as the bed and material move forward. Additional wash water may be added to the undissolved solids in the filter.

[0062] The filtered solids may be fed to a conveyor belt and / or a storage location. The filtered solid material may be fed to a drying stage. The drying stage may be a rotary dryer. The filtered solids may be fed to the drying stage via a screw feeder. The dried solids may be fed from the dryer to a storage location.

[0063] The separated solids may form a by-product, which ideally has a market value.The separated liquid may be returned to the leaching step and / or may be sent to a spray drying step.

[0064] The method may comprise feeding the leachate to a drying step or a spray drying step, for example via one or more buffer vessels or storage vessels.The leachate may be pumped to the drying step or the spray drying step, in particular one or more nozzles therein.

[0065] In particular with regard to spray drying, one or more gases (e.g. air) may be pumped to the drying step, in particular to the nozzle / nozzles therein. The nozzle may co-inject the gas and the percolate. The nozzle may act as an atomizer for the fluid percolate.

[0066] The drying step may use, and / or the dryer may be a falling film evaporator. The leachate may flow downwardly over one or more surfaces provided in the dryer, such as the surface of one or more tubes. The leachate may flow over the surfaces as a thin film. One or more or all of the surfaces may be heated. One or more or all of the surfaces may be heated in whole or in part. A gas, such as air, may pass through the leachate, preferably moving in a direction different from the direction of movement of the leachate, such as in the opposite direction.

[0067] The method may comprise feeding hot gas, preferably hot air, into the drying step or the spray drying step.The hot gas may be provided in parallel or counter-current direction to the introduction of the leachate.

[0068] The gas may be hot gas from the treatment of the exhaust gas stream and / or may have energy resulting from the treatment of the exhaust gas stream, in particular in terms of its temperature.

[0069] One or more additional components (e.g., water or steam) may be added to the drying step, e.g., co-injected with the gas. One or more additional components may be added to control the pressure and / or temperature and / or chemical composition of the feed entering the drying step. The hot gas may be generated by a heating step, e.g., by electrical heating and / or a heat exchanger system.

[0070] The atomized leachate is preferably dried by contact with hot gases. The atomized leachate is preferably solidified by hot gases.

[0071] The method may include obtaining solids from a drying step or a spray drying step, for example by separating solids and gases in a drying step or a spray drying step. Solids may be collected at the bottom of a drying step or a spray drying step. Solids may be removed in batches or continuously. One or more subsequent separations of solids and gases may be provided for the gas outlet stream, for example using a bag filter and / or a cyclone separator to provide. Preferably after solid separation, the gas outlet stream may be used to stir and / or heat in one or more steps, particularly in a drying step or a spray drying step.

[0072] The method may comprise obtaining solids from the leachate by using a drying step or a spray drying step.

[0073] The method may include compressing and / or molding the solid into pellets in one or more additional steps. The one or more additional steps may include a pelletizing step. Compression and / or molding may be provided without adding any additional components to the solid. In particular, no binder or moisture may be added.

[0074] The compressed and / or molded solids, such as pellets, may be collected and / or stored, such as for later use. The compressed and / or molded solids, such as pellets, may be fed into a furnace, ideally in a first location. The compressed and / or molded solids, such as pellets, may be fed into a furnace, ideally in a first location, to provide material on a surface of molten metal in the furnace.

[0075] Compressed and / or molded solids, such as pellets, may be produced to controlled sizes.

[0076] Compressed and / or moulded solids, such as pellets, may be produced to a controlled size distribution, for example such that less than 5%, more preferably less than 2%, by weight of the pelletised material has a diameter less than 149 microns, for example considered to be the largest linear dimension.

[0077] Compressed and / or moulded solids, such as pellets, may be produced to a controlled moisture content, for example less than 0.5 wt% or preferably less than 0.2 wt%.

[0078] Compressed and / or molded solids, such as pellets, can be produced with a controlled ratio of sodium chloride to potassium chloride, such as a predetermined ratio of + / - 5%. The ratio can be between 4:1 and 1:1 sodium chloride to potassium chloride.

[0079] One or more batches of compressed and / or molded solids, such as pellets, having a first set of characteristics may be mixed with one or more batches of compressed and / or molded solids, such as pellets, having one or more different characteristics.

[0080] Various embodiments of the present invention will now be described, by way of example only, and with reference to the accompanying drawings, in which: Figure 1 is a flow chart of a method for recovering salts from an aluminum recovery process, including improvements according to the present invention; Figure 2 is a flow chart of a process according to an embodiment of the present invention; Figure 3 is a schematic diagram of a spray dryer used in the present invention.

[0081] There are various problems with large-scale centralized processes. These include: The cost of transporting the compressed slag 9 to a suitable centralized plant for processing; The significant regulatory issues surrounding such transport (especially if it crosses national borders); safety risks such as accidents involving such transport; Centralized process plants must be used, outside the control of the salt producer; Increased energy requirements and difficulty in achieving cold compressed slag size reduction; The variable nature of the feed slag as it contains different salt content, different lath ratios, different contaminants etc. as it comes from various different aluminium recyclers, presents process control problems; The variable nature of the raw slag affects the dry salt produced (in terms of chemical composition, moisture content and particle size distribution), which means that the product is not well controlled or defined, thereby compromising its use as a good salt feed to the furnace.

[0082] exist Figure 1 In the invention, a rotary furnace 1 is used for recovering aluminum, for example waste material contaminated by paint, coatings, etc. The furnace 1 produces a flow of aluminum products (not shown) and a flow of waste gas 3 and a flow of slag 5.

[0083] The waste gas stream 3 is appropriately treated to recover / reuse or render the gases it contains safe.

[0084] To prevent oxidation of the aluminum and provide other benefits, salt is added to the top of the melt in the furnace 1 to form a barrier. The salt, along with some of the aluminum, forms a slag and thus a slag stream 5. The salt is primarily sodium chloride, but also potassium chloride and other materials. A typical salt slag (aka aluminum salt cake) produced by the secondary aluminum industry may contain 15-30% alumina, 30-55% sodium chloride, 15-30% potassium chloride, 5-7% other materials (e.g., aluminum and impurities including carbides, nitrides, sulfides, and phosphides, etc.).

[0085] After processing, the aluminum is tapped from the furnace 1, and slag is the main material remaining. The slag is mainly formed by salts, together with removed contaminants and other components obtained during the melting process.

[0086] When the slag stream 5 is removed from the furnace 1, it is typically emptied into a bin (not shown) and then fed into a slag press 7 to allow mechanically assisted agglomeration of the aluminum from the slag. The aluminum is typically returned to the furnace 1 after separation. The compressed material from the slag press 7 is classified as compressed slag 9.

[0087] The compressed slag 9 is allowed to cool. The compressed slag 9 still contains a large amount of aluminum and a large amount of salt. In many countries, compressed slag is classified as a hazardous material in environmental and other legal aspects and therefore requires further consideration.

[0088] One option is to transport the compressed slag 9 to a suitable plant to recover the aluminium and process it to recover the salts. This involves transporting the compressed slag 9 by road from the location of the smelter 1 where the compressed slag 9 is produced to a remote processing plant. This involves significant transport costs, significant regulatory issues (particularly if crossing national borders) and safety risks of accidents etc.

[0089] A typical processing plant is a large facility that provides centralized processing of compressed slag 9 produced by various aluminum smelting plants.

[0090] The compressed slag 9 is cold at the beginning of the process and is fed into a salt crusher 11 to reduce the size of the compressed slag 9. The cold nature of the compressed slag 9 presents difficulties and increased energy requirements to the size reduction step. For example, a pneumatic crusher may be required to first break the compressed slag 9 into smaller pieces. The size reduction may include the salt crusher 11 shown, as well as a size-based separation step, such as a screen.

[0091] The size reduced salt stream 13 is then fed into an eddy current separator 15. This produces a recovered ferrous stream (not shown), an aluminium stream 17 which can be collected and sold and / or can be returned to the smelter 1, and a cleaned salt stream 19.

[0092] The cleaned salt stream 19 is fed to a leach tank 21 along with a water stream. The leaching process dissolves the salt content of the cleaned salt stream 19, ionizing the sodium chlorate, thereby providing a dissolved salt stream 23. The remaining solids, typically alumina and non-metallic particles, form a suspended solids stream 25. The leach waste gas stream 27 is fed to a combined heat and power unit 29 where it is burned to provide power and heat to the entire process, particularly the steam dryer 31. Typical gases include hydrogen, methane and ammonia. Phosphine and hydrogen sulfide may also be present.

[0093] The suspended solids stream 25 is sent to a filter 33 to separate the solids from the liquid. The solids are a useful product of the process that can be sold. The liquid is sent back (not shown) to the leach tank 21.

[0094] The dissolved salt stream 23 is passed to an evaporator 35 to produce a steam stream 37 , a gaseous hydrocarbon stream 39 (which also goes to the cogeneration unit 29 ), and a wet salt stream 41 .

[0095] The steam stream 37 is sent to the condenser 43 and the resulting water stream is sent back to the leaching tank 21 .

[0096] The wet salt stream 41 is taken to the superheated steam dryer 31. This produces a steam / vapour stream (not shown) which is returned to the leaching tank 21 and a product stream, namely a dry salt stream 43. The dry salt stream 43 can provide the salt feed 45 for the furnace 1.

[0097] The present invention seeks to solve these problems and / or provide improvements thereto through process approaches and changes made.

[0098] refer to Figure 2 , providing the whole process of the embodiment of the present invention. Again, the rotary furnace 51 is used to recover aluminum, and the melting furnace 51 produces an aluminum product flow (not shown) and an exhaust gas flow 53 and a slag flow 55.

[0099] and Figure 1 The same features are no longer repeated, but still apply to Figure 2 For example, the waste gas stream 53 is appropriately treated to recover / reuse or make the gases it contains safe.

[0100] The slag stream 55 is taken out of the furnace 51 and then sent to a slag press 57. The compressed material from the slag press 57 is also compressed slag 59.

[0101] In this embodiment of the invention, the compressed slag 59 is processed at the same location where it is generated. This is possible because lower capital costs and lower unit sizes are feasible for the overall process selected in this embodiment compared to existing methods. A typical local plant may be configured to process 1 ton of salt per hour or less, while a centralized plant may process 5 tons of salt per hour or more.

[0102] The first benefit resulting from this is that the compressed slag 59 is only allowed to cool to the extent required. This cooling still aids processing and reduces the risk of further reaction of the hot aluminum, but the compressed slag 59 is not allowed to cool to an extent that would have a negative impact in the subsequent size reduction stage.

[0103] The compressed slag 59 is fed to a slag crusher 61 to reduce the size of the compressed slag 59. However, since the compressed slag 59 is not cold and hard, size reduction is easier to achieve and the resulting size distribution is easier to control. This provides a better size distribution and / or reduction of fine material, such as material below 1 mm. This is important for improving the saleability of the solids recovered from the suspended solids stream 75.

[0104] In an optimized form, the size reduction stage 61 provides a jaw crusher to effect the primary reduction in size. However, the compressed slag 59 is then fed to rollers. The rollers are used to produce a more consistent product in a flat form suitable for presentation to the eddy current separator 65. The rollers also ensure that the size range of the compressed slag 59 is suitable for processing in the subsequent cyclone separation.

[0105] After size reduction, the size reduced slag stream 63 is then fed into an eddy current separator 65. This produces a ferrous metal stream (not shown) which is recovered.

[0106] In an optimized form, the remaining material, including salt, is fed from the current separator 65 to a further cyclone separator. The cyclone separator involves suspending the remaining material in air and then subjecting it to gravity-based separation due to the action of the cyclone separator. The cyclone separator effectively removes components that would otherwise adversely contribute to gas generation at a later stage. This produces an aluminum stream 67 that is returned to the furnace 1 and a cleaned salt stream 69.

[0107] The cleaned salt stream 69 is fed to the leach tank 71 along with the water stream 73. The same general leaching process is provided.

[0108] However, in an optimized form, the residence time of the leaching stage is reduced and a treatment chemical is also fed into the leaching stage. The preferred residence is about 5 minutes. This is possible because a controlled size distribution is fed into the leaching tank. The reduced residence time and / or treatment chemical facilitates a significant reduction in the volume of gas produced. The treatment chemical may include hydrogen peroxide. The hydrogen peroxide facilitates maximizing the oxide form and reducing or removing the nitride and carbide forms.

[0109] Since the aluminium recovery plant operator and the slag processing plant operator are the same, the known properties of the slag 59 means that the feed to the leaching tank 71 is better known and more consistent.

[0110] A dissolved salt stream 73, a suspended solids stream 75, and a leach waste gas stream 77 are produced as previously described. However, the leach waste gas stream 77 is now utilized to improve the energy efficiency of the overall system. The leach waste gas stream 77 is fed to a heat and power cogeneration unit 79 where it is burned to provide power and heat to the overall process. In particular, power can be generated in the overall process to drive one or more processes, and thermal energy can be used in the spray dryer 97. Typical gases present include hydrogen, methane, and ammonia. Phosphine and hydrogen sulfide may also be present.

[0111] In an optimized form, a dissolved salt stream 73 and a suspended solids stream 75 are withdrawn from the leaching tank 71 in a single process stream. This single stream is fed to a ribbon mixer. The ribbon mixer ensures that the suspended solids are evenly distributed in the dissolved salts before being fed to a filter 83, possibly with additional water.

[0112] The suspended solids and dissolved salt mixture is fed to filter 83 to separate the solids from the liquid. As mentioned above, the solids are a useful by-product of the process that can be sold and have improved properties and therefore increased value.

[0113] In an optimized form, the filter 83 is a vacuum belt filter, and as the material moves along it, the dissolved salt stream is drawn through the bed to leave the suspended solids behind. Additional wash water is added to clean the suspended solids from the filter separated from the dissolved salt stream, while the wash water is collected with the dissolved salt stream.

[0114] The dissolved salt stream 73 is then subjected to different processing steps than before, as described further below.

[0115] In an optimized form, the suspended solids stream 75 undergoes improved treatment. The solids stream is discharged from the vacuum belt filter onto a discharge conveyor and then into a storage hopper. From the storage hopper, the solids are drawn through a screw feeder into a rotary dryer. The rotary dryer is used to dry the solids stream to a desired level. The dried solids are discharged to a storage location.

[0116] The dissolved salt stream 73 is passed to a spray dryer 97, which will be described in more detail below. The spray dryer benefits from heat recovery from the furnace 51 and / or from the combined heat unit 59. The resulting salt stream 91 is Figure 1 The evaporator in the form is much drier.

[0117] In an embodiment not shown, dissolved salt stream 73 is passed to an evaporator to produce a steam stream, a gaseous hydrocarbon stream (which also goes to cogeneration unit 79 ), and a wet salt stream 97 which is passed to spray dryer 97 as described above.

[0118] The problem with the salt stream 91 is that the particle size is relatively small. However, the applicant has determined that this problem can be solved by feeding the salt stream 91 into a pelletizer 99, which is described in more detail below. In addition, the applicant has determined that the salt stream properties and size are ideally suited for pelletization without the need for further processing or additives, such as binders.

[0119] As a product stream, the dry salt stream 93 is now pelletized, which allows optimization of physical properties, such as the size of the pellets, for subsequent reuse of the dry salt stream 93 as salt feed 95 for the smelter 51 .

[0120] Furthermore, the pellets are known to have a standard content, for example in terms of the ratio of sodium chloride to potassium chloride present (which is used to control the sodium chloride melting temperature) and therefore provide a more controlled feed to the furnace 51. A mix of different pellets may also provide other variations in the feed to the furnace 51.

[0121] Finally, for example with Figure 1 Compared to dry salt products, pellets are also more suitable for storage without absorbing moisture.

[0122] like Figure 3 As shown, the spray dryer 97 receives the dissolved salt stream 73 via the balancing tank 200, and the flow rate into the tank is controlled by a valve 202 to maintain the solution water level. A level probe that opens low and closes high is used to operate the valve 202. An inlet 204 is also provided on the balancing water tank 200. An outlet 206 supplies the dissolved salt stream 73 to a peristaltic pump, which pumps the dissolved salt stream 73 to the atomizer 210.

[0123] The atomizer 210 also receives filtered air.

[0124] Atomizer 210 utilizes a two-fluid nozzle atomizer that provides a co-current flow pattern, but a fountain-mode rotary atomizer and a two-fluid atomizer are also possible. High-speed air encounters a low-speed fluid to break it into droplets.

[0125] The atomizer 210 is placed in the upper part of a drying chamber 214 formed by a cylindrical upper part 216 and a conical lower part 218. The bottom of the conical part 218 provides a powder outlet 220 and a wet air side outlet 222.

[0126] The atomized fluid directly encounters the hot air that has passed through the heating stage 212. The heating stage 212 includes an electric heat source and a baffle-type air distributor to control the flow pattern and heat transfer in the air.

[0127] The dissolved salt stream 73 is in close contact with the hot air when passing through the atomizer 210 and entering the drying chamber 214. This provides drying in the hot air stream. Away from the atomizer 210, the drying chamber 214 allows the dry powder to be separated from the hot air, both through their respective outlets.

[0128] The dry powder is conveyed away through a fluidizing ejector. Cooling and packaging of the powder can then be provided.

[0129] The separated hot air enters an air stream to atmosphere which is provided with a bag filter to remove any remaining powder, with a cyclone separator providing another form of filtration.

[0130] The following table defines some typical operating characteristics of a suitable spray dryer.

[0131] Table 1 Spray-dried products have tightly controlled particle size distribution, residual moisture content, bulk density and morphology.

[0132] Regarding the results obtained, the variation in moisture content achieved under different conditions is detailed in Table 2.

[0133] Table 2 When measured using SEM imaging, the particles produced were generally about 5 to 30 microns in diameter and had a blocky crystalline appearance. Optical microscopy imaging also confirmed that the particles tended to form agglomerates with diameters ranging from 120 to 2500 microns.

[0134] The pelletizer 99 is important for increasing the size of the product to a size where it cannot be easily transported out of the furnace by air.

[0135] A roller-based compactor is used to check the suitability of powders for pelletizing. The powder is fed through two counter-rotating rollers using gravity. The friction between the material and the roller surface causes the powder to enter the narrow space between the rollers and the high load present causes the powder to compact well. The powder is held together in a compacted form without the presence of any binder, water or other additives.

[0136] A roller based pelletizer wherein the roller has opposing halves of a recessed space which is used to successfully form pellets.

[0137] This technique readily achieves moisture levels below 0.2 wt% and allows less than 2% of the material to be below 149 microns in diameter (thus reducing the amount of fines present).

Claims

1. A method of treating a material, the material being an upper layer from a metal smelting process, the material comprising one or more salts, the material comprising one or more metals, the method comprising: a) sending the material to a size reduction step; b) passing the material from the size reduction step to a separation step; c) passing said material from said separation step to a leaching step, Wherein, the separation step comprises: A ferrous metal separation step in which the aluminum extracted during separation is returned to the furnace; a density-based separation step which separates the aluminium and / or aluminium-containing components from the salt components, the density-based separation step using a cyclone separator and the density-based separation step being used to remove one or more gas generating components from the material fed to the leaching step, The size reduction step creates a flat bed of material for separation or exposes the ferrous metal for separation, and, A flat bed of material is created which can be readily suspended in a gas stream for feeding into the cyclone separator.

2. The method of claim 1, wherein the size reduction step comprises a plurality of size reduction steps, the size reduction step comprising a jaw crushing step.

3. The method of claim 1, wherein the size reducing step comprises a rolling step.

4. The method of claim 1, wherein the size reduction step comprises one or more sizing steps to separate the material into one or more portions according to size.

5. The method of claim 1, wherein the leaching step is provided with hydrogen peroxide, which is used to increase the oxide content and / or reduce or remove the nitride content and / or calcify content.

6. The method of claim 1 wherein the size reduction step is followed by a ferrous metal separation step and then a non-ferrous metal separation step, the ferrous metal separation step being provided by an eddy current separator.

7. A method as claimed in claim 6, wherein the ferrous metal separation step is provided by a vibrating table and / or a compressed air separator.

8. The method of claim 4, wherein aluminum extracted by the one or more sizing steps is returned to the furnace.

9. The method of claim 6, wherein the density-based separation step is a non-ferrous metal separation step.

10. The method of claim 1, wherein the density-based separation step uses an air-based cyclone separator.

11. An apparatus for treating a material, the material being a supernatant from a metal smelting process, the material comprising one or more salts, the material comprising one or more metals, the apparatus comprising: a) a feeder providing material to the size reduction device; b) size reduction devices; c) a feeder providing material to a density-based separation device; d) a density-based separation device, the density-based separation device being subsequent to the size reduction device, the density-based separation device being configured to separate aluminum and / or aluminum-containing components from salt components; e) a feeder for providing material to the leaching device; f) Leaching device, The apparatus further comprises a ferrous metal separation device, the size reduction device being immediately followed by the ferrous metal separation device; wherein the density-based separation device comprises a cyclone separator and the density-based separation device is configured to remove one or more gas generating components from the material fed to the leaching step, The size reduction apparatus has an output device which is a flat bed of material for exposing ferrous metals for separation and which can be readily suspended in an air stream.

12. The apparatus of claim 11, wherein the size reduction device comprises a plurality of size reduction devices, the size reduction devices comprising a jaw crusher.

13. The apparatus of claim 11, wherein the size reduction means comprises a rolling means.

14. The apparatus of claim 11, wherein the size reduction device comprises one or more sizing devices to separate the material into one or more portions according to size.

15. Apparatus as claimed in claim 11 wherein the ferrous metal separation means is provided by an eddy current separator.

16. The apparatus of claim 11, wherein the ferrous metal separation means is provided by a vibrating table and / or a compressed air separator.

17. The apparatus of claim 14, wherein aluminum extracted by the one or more sizing devices is returned to the furnace.

18. The apparatus of claim 11, wherein the density-based separation apparatus is a non-ferrous metal separation apparatus.

19. The apparatus of claim 18, wherein the density-based separation device comprises an air-based cyclone separator.

20. A method of treating a material, the material being a top layer from a metal smelting process, the material comprising one or more salts, the material comprising one or more metals, the method comprising: a) sending the material to a leaching step; b) obtaining material from said leaching step; c) passing the material from the leaching step to a solid-liquid separator, such as a filtration step; d) sending the solid material from said filtering step to a drying step.

21. The method of claim 20, wherein undissolved solids and dissolved solids are fed to the solid-liquid separator.

22. A method as claimed in claim 20 or 21, wherein the undissolved solids and dissolved solids are fed to a mixer, such as a ribbon mixer, before being fed to the solid-liquid separator.

23. A method as claimed in any one of claims 20 to 22, wherein the mixer causes the undissolved solids to be evenly distributed in the dissolved solids before being fed to the solid-liquid separator.

24. The method according to any one of claims 20 to 23, wherein the solid-liquid separator is a filter, in particular a belt filter, more preferably a vacuum belt filter.

25. A method as claimed in any one of claims 20 to 24 wherein the dissolved solids stream is drawn through the bed as the bed and material move forward.

26. A method as claimed in any one of claims 20 to 25 wherein additional wash water is added to the undissolved solids in the filter.

27. A method as claimed in any one of claims 20 to 26, wherein the filtered solids are fed to a conveyor belt and / or a storage location.

28. A method as claimed in any one of claims 20 to 27, wherein the filtered solid material is sent to a drying stage, such as a rotary dryer.

29. A process as claimed in any one of claims 20 to 28 wherein the filtered solids are fed to the drying stage by means of a screw feeder.

30. A method as claimed in any one of claims 20 to 29, wherein the leaching step is provided with hydrogen peroxide.

31. A method as claimed in any one of claims 20 to 30, wherein the hydrogen peroxide is used to increase the oxide content and / or to reduce or remove the nitride content and / or the calcification content.

32. A method as claimed in any one of claims 20 to 31 wherein the residence time in the leaching stage is less than 10 minutes, preferably less than 8 minutes and ideally less than 5 minutes or less.

33. A method as claimed in any one of claims 20 to 33 wherein residence time is controlled to control the volume of gas produced by the leaching step.

34. Apparatus for treating material, said material being a supernatant from a metal smelting process, said material comprising one or more salts, said material comprising one or more metals, said apparatus comprising: a) a feeder providing material to the leaching device; b) Leaching device; c) the outlet of the material from the leaching device to the filtering device; d) Filtering device; e) a feeder from the filtering device to the dryer; f) Dryer.

35. The apparatus of claim 34, wherein undissolved solids and dissolved solids are fed to the solid-liquid separator.

36. Apparatus as claimed in claim 34 or 35, wherein undissolved solids and dissolved solids are fed to a mixer, such as a ribbon mixer, before being fed to the solid-liquid separator.

37. Apparatus as claimed in any one of claims 34 to 36, wherein the mixer causes the undissolved solids to be evenly distributed in the dissolved solids before being fed to the solid-liquid separator.

38. The device according to any one of claims 34 to 37, wherein the solid-liquid separator is a filter, in particular a belt filter, more preferably a vacuum belt filter.

39. Apparatus as claimed in any one of claims 34 to 38 wherein the dissolved solids stream is drawn through the bed as the bed and material move forward.

40. Apparatus as claimed in any one of claims 34 to 39 wherein additional wash water is added to the dissolved solids in the filter.

41. Apparatus as claimed in any one of claims 34 to 40 wherein filtered solids are fed to a conveyor belt and / or a storage location.

42. Apparatus as claimed in any one of claims 34 to 41, wherein the filtered solid material is fed to a drying stage, such as a rotary dryer.

43. Apparatus as claimed in any one of claims 34 to 42, wherein the filtered solids are fed to the drying stage by a screw feeder.

44. Apparatus as claimed in any one of claims 34 to 43, wherein the leaching step is provided with hydrogen peroxide.

45. The apparatus of claim 44, wherein the hydrogen peroxide is used to increase the oxide content and / or to reduce or remove the nitride content and / or the calcification content.

46. ​​Apparatus as claimed in any one of claims 34 to 45, wherein the residence time in the leaching stage is less than 10 minutes, preferably less than 8 minutes and ideally less than 5 minutes or less.

47. The apparatus of claim 46, wherein residence time is controlled to control the volume of gas produced by the leaching step.

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