Patent Application
20190256947
The present invention relates to field of nonferrous metallurgy, and particularly a method for processing clinker to produce isolated desired metals.
The present invention relates to the field of processing the cake reduction of products, which result after zinc-lead concentrate leaching—clinker and agglomerate. After the processing of zinc concentrate according to the technological scheme “Oxidizing roasting and leaching,” a non-tradable intermediate ferrous product—referred to as “cake”—containing non-ferrous metals such as copper, lead, antimony, and zinc is formed. For additional recovery of zinc from the cake, the cake may be subject to reduction roasting in rotating furnaces or on sintering machines; however, iron, copper, lead, antimony, and carbon, remain in the non-tradable product—within the clinker or agglomerate.
It is known how to process metallized materials containing iron, using the mine melt with oxygen-air blowing in the form of a mixture of sulphidizers (copper ore) with the additive of fluxes and iron slag in the mass ratio of metallic irons to sulphur, equal to (1.2-1.5):1. The smelting is carried out at the mass fraction of the iron slag in a solid charges within 28-34 mass percent (Author Cert. the USSR No. 1498804, 07.09.88. B.I. No. 29). The main disadvantages of this method are the following: obtaining a low-metal matte with low content of non-ferrous metals that includes noble ones, the need to add sulphidizer, the conversion of iron into the waste—i.e., slag, and the emission of gas with a low sulphur gas content.
Another method for processing zinc plant clinker also exists, which provides for the use of the dust from the melting of copper concentrate as sulphidizer in the mass ratio of the clinker to dust in the agglomerated mixture of the clinker with sulphidizer (4-2:1) and the share of iron slag in charges, equal to 38-42% (Author Cert. the USSR No. 1622413, 23.01.91. B.I. No. 3). The main disadvantages of this method are the same as discussed above—obtaining matte with a low content of non-ferrous metals including noble ones, the need to add sulphidizer, the conversion of iron to waste, i.e., slag, and emission of gas with low content of sulphur gas.
The closest prior art to the present method for processing zinc plant clinker (Patent RU 2278174/Scopov G. V., Kharitidi G. P., Krivonosov Yu. S., Scherbakov V. V., Rybnikov A. P.) comprises briquetting with a sulphidic additive and melting with fluxes and ferruterous slag. For carbon oxidation acceleration (in clinker from 5 to 33% hesitate) beforehand input three valence iron in the amount of 3-13 mass % percent into ferruterous slag, the melt is carried out with oxygen consumption of 500-1100 nm3/t of clinker. As a result, zinc transfers into the sublimates, copper, silver, gold, lead, and antimony transfer into matte, and iron transfers into slag (during conversion of the matte—the balance amount). The main disadvantages of this method are: burning out of carbon, transfer of additional amount of iron into slag, and the complication of selective oxidation of carbon, since sulphur content in clinkers is 2-3 times smaller than carbon content, and sulphur in the matte will also oxidize and some of the non-ferrous metals will transfer into slag.
The present invention comprises methods and systems for the extraction of ferrous and non-ferrous metals from zinc production clinker and agglomerate. The methods and systems comprise the following summarized process:
The dissolution of the fine-grained clinker in a solution of mineral acids (preferably in a solution of sulfuric acid), resulting in a pulp and a foam phase comprising carbon floating on top of the pulp, and the simultaneous flotation extraction of carbon in the foam phase (i.e., foamy part). The pulp is then filtered, resulting in a filtrate and a cake. The cake is then dried (for reduction of the material flow entering the melting stage). The foam phase is directed to processing for the extraction of non-ferrous metals from the foamy part. Processing can be carried out by means of combustion of carbon or use of a foamy phase as a reducer when receiving matte or draft metal. The filtrate is processed to allow for sedimentation of the dissolved copper by means of adding hydrogen sulfide, and after separation of the copper sediment in the form of cupric sulfide, a process of salting-out the iron sulfate by means of a strong solution of sulfuric acid (96% H2SO4) is initiated. The received iron sulfate solution is subjected to filtrations and washing out, resulting in separation of iron sulfate from the filtrate. Then, the filtrate is returned to the earlier clinker solution for further processing.
The melting of the cake is carried out without air delivery (i.e., in the absence of any air), with calcium oxide CaO at a mass ratio to the restored iron of CaO:Fe=1:1 (i.e., masses are identical), at a carbon consumption for iron restitution, in particular, in an induction furnace at a temperature between 1250-1350° C., resulting in products of fluid slag, matte, and spongy iron. The absence of air delivery during melting is due to the formation of slag along the surface of the melt at the furnace surface. As the slag settles down on the surface of the melt, the slag blocks the access of air to the other phases formed during melting (matte and metal).
Additional recovery of iron from the fluid slag, if necessary, is carried out by the well-known principle of draining to another melting unit, with the addition of an amount of reducing agent (carbon) required for the restitution of 80-90% of iron in the slag. Restitution is carried out in the temperature range of 1250-1520° C., depending on the need to receive spongy iron or melted iron.
Matte and metal products are then dissolved in a dilute solution of sulfuric acid (1:1). The hydrogen sulfide emitted at dissolution of matte and metal is directed to the copper sedimentation process from the filtrate. The received solution is filtered, resulting in a filtrate and non-ferrous metals. The filtrate is then exposed to a strong solution of sulfuric acid (96% by weight) in order to cause a salting-out of iron sulfate, after which filtering and washing out is performed, resulting in a filtrate and iron sulfate.
The drawings described herein are for illustrative purposes only and are of selected embodiments not including all possible implementations. The drawings are not intended to limit the scope of the present disclosure, and the figures may not show all elements of particular embodiments, even if operation would be possible without such elements.
The average chemical composition of the clinker of Kazzinc JSC is presented in Table 1. The content of gold in the clinker is 4.0-6.1 g/t. The content of silver in the clinker is 200-410 g/t.
The present invention describes a technology for complete separation of non-ferrous metals from iron, thus turning a former waste product into a processable intermediate byproduct.
The purpose of the proposed invention is ensuring the completeness of processing the zinc plant clinker, with the extraction of all target components, including iron, into end products, a reduction of the material flow, and the simplification of the technology.
The objective of the invention, unlike the prior art, is achieved through the prior removal of excess carbon and the conversion of non-ferrous metals into the metal phase as a result of the following sequential processes (and as shown in
1) The dissolution of the fine-grained clinker 1 in a solution of mineral acids 2 (preferably in a solution of sulfuric acid), resulting in a pulp and a foam phase comprising carbon and floating on top of the pulp, and the simultaneous flotation extraction of carbon in the foam phase (i.e., foamy part) 3. The pulp is then filtered 4, resulting in a filtrate 7 and a cake 5. The cake is then dried (for reduction of the material flow entering the melting stage). The foam phase is directed to processing 6 for the extraction of non-ferrous metals from the foamy part. Processing 6 can be carried out by means of combustion of carbon or use of a foamy phase as a reducer when receiving matte or draft metal, for example, when melting in a fluid bathtub. The filtrate 7 is processed to allow for sedimentation of the dissolved copper 8 by means of adding hydrogen sulfide, and after separation of the copper sediment in the form of cupric sulfide 9, a process of salting-out 10 the iron sulfate by means of a strong solution of sulfuric acid (96% H2SO4) is initiated. The received iron sulfate solution 11 is subjected to filtrations and washing out 12, resulting in separation of iron sulfate from the filtrate 13. Then, the filtrate 13 is returned to the clinker dissolution 14 for further processing 2.
2) The melting 18 of the cake 5, without air delivery (i.e., in the absence of any air), with calcium oxide CaO at a mass ratio to the restored iron of CaO:Fe=1:1 (i.e., masses are identical), at a carbon consumption for iron restitution, in particular, in an induction furnace at a temperature between 1250-1350° C., results in products of fluid slag 17, matte 16, and spongy iron 19. The absence of air delivery during melting is due to the formation of slag along the surface of the melt at the furnace surface. As the slag settles down on the surface of the melt, the slag blocks the access of air to the other phases formed during melting (matte and metal).
3) Additional recovery of iron 20 from the fluid slag 17, if necessary, is carried out by the well-known principle of draining to another melting unit, with the addition of an amount of reducing agent (carbon) required for the restitution of 80-90% of iron in the slag 17. Restitution is carried out in the temperature range of 1250-1520° C., depending on the need to receive spongy iron or melted iron;
4) Matte 16 and metal 19 products are dissolved in a dilute solution of sulfuric acid (1:1) 21. The hydrogen sulfide emitted at dissolution of matte and metal is directed to the copper sedimentation process 8 from the filtrate 7. The received solution 22 is filtered 23, resulting in a filtrate 24 and non-ferrous metals 28. The filtrate 24 is then exposed to a strong solution of sulfuric acid (96% by weight) in order to cause a salting-out 25 of iron sulfate, after which filtering and washing out 12 is performed, resulting in a filtrate 13 and iron sulfate 27.
A significant and distinguishing feature of the present invention is the reduction melt of the cake 18 with limited carbon consumption after a pretreatment comprising preliminary dissolution of the clinker in an inorganic acid in conditions comprising selection and removal of a majority part of carbon via a foamy phase/part containing that majority of carbon 3, and further extraction of non-ferrous metals 28 from a matte-metal phase formed during melting by additional dissolution in an inorganic acid. Preferably, the inorganic acid is sulfuric acid, and the dissolution during pretreatment 2 and dissolution of the metal-matte phase after melting 21 occurs in a dilute solution of sulfuric acid (1:1).
Examples of Concrete Exercise of the Invention.
For each of the below experiments, agglomerate and clinker of Kazzinc JSC were used. The content of silver in this agglomerate was 416 g/t. The chemical composition of the agglomerate taken for the experiments is presented in Table 2. The content of silver in the clinker was 375 g/t. The chemical composition of the clinker taken for the experiments is presented in Table 3.
The results of experiments on processing of agglomerate and clinker are given below.
Agglomerate is subjected to screening with selection of a particle fineness between 3 mm and 6 mm (2.40% Cu; 45.47% Fe; 11.59% C; 384 g/t Ag). Then, the allocated size was subjected to melting according to the present invention. The following results (product output and its chemical composition) are received:
The degree of copper extraction into matte was 97.8%, into metal—1.04%, into slag—1.16%. The degree of iron extraction into matte was 10.58%, into metal—78.60%, into slag—10.82% (i.e., the balance). The degree of silver extraction into matte was 86.22%, into metal—1.2%, into slag—12.58% (i.e., the balance).
Agglomerate is subjected to screening with selection of a particle fineness of greater than 6 mm (2.46% Cu; 52.32% Fe; 5.09% C; 536.7 g/t Ag). Then, the allocated size was subjected to melting according to the present invention. The following results of experience (product output and its chemical composition) are received:
The degree of copper extraction into matte was 1.35%, into metal—97.0%, into slag—1.65%. The degree of iron extraction into matte was 7.02%, into metal—72.18%, into slag—20.80% (i.e., the balance). The degree of silver extraction into matte was 11.61%, into metal—88.389%, into slag—0.001% (i.e., the balance).
Agglomerate is subjected to screening with selection of a particle fineness of less than 3 mm (1.94% Cu; 50.0% Fe; 38.22% C; 327.66 g/t Ag). Then, the allocated agglomerate was subjected to melting according to the present invention. The following results (product output and its chemical composition) were received:
The degree of copper extraction into matte was 96.92%, into metal—1.48%, into slag—1.60%. The degree of iron extraction into matte was 11.46%, into metal—76.61%, into slag—11.93% (i.e., the balance). The degree of silver extraction into matte was 94.0%, into metal—1.76%, into slag—4.24% (i.e., the balance).
Crushed clinker (74.3% of a particle size less than 0.071 mm) was subjected to melting according to the present invention. The mass of clinker was 100 g. The following results (product output and its chemical composition) were received:
The degree of copper extraction into matte was 27.41%, into metal—71.78%, into slag—0.81%. The degree of iron extraction into matte was 8.33%, into metal—82.05%, into slag—9.62% (the balance). The degree of silver extraction into matte was 16%, into metal—83.96%, into slag—0.04% (the balance).
From the results of Examples 1-4, it follows that distribution of non-ferrous metals (copper, silver, etc.) between matte and metal depends on carbon content within the melt material. A carbon content above 10% within the melt material leads to a more complete transition of copper (and other non-ferrous metals) to the matte phase. In turn, a carbon content below 10% leads to a more complete transition of copper (and other non-ferrous metals) to the metal phase. At the same time, a carbon content above 10% leads to an increase in silver losses to slag. During melting, a part of the iron which is contained in the clinker is oxidized. When the clinker melts, carbon restores oxidized iron and binds it to Fe3C carbide (cast iron). For such a result comprising a concentration of cast iron (i.e., a majority of cast iron over sponge iron, or more cast iron than sponge iron) within the metal phase, the mass ratio of iron to carbon in the furnace must be no more than 14:1. That is, for example, for formation of cast iron, the content of carbon in the initial clinker from Example 4, containing 48.0% Fe, must be no less than about 3.43%. If the carbon content in the clinker is less than about 3.43%, then additional carbon should be added during the smelting.
In the metal phase, in addition to cast iron, sponge iron may also form, which has a higher melting point than cast iron. The carbon content in the agglomerate and clinker (Examples 1-4) exceeds the amount required for melting. An excess of carbon does not make it possible to completely prevent the distribution of copper between matte and metal. Therefore, preliminary processing of clinker, which provides for dissolution in solution of sulfuric acid, is also preferred. Preliminary processing allows not only for extracting additional iron and carbon, but also for a reduction of the lump and size of materials arriving on melting. During preliminary processing, up to 80% of the carbon contained in the clinker is removed in a foamy phase. When the clinker dissolves, up to 20% of iron passes into the solution. Accordingly, up to 20% of carbon and up to 80% of iron remain in the cake from the content in the initial clinker.
A sample of clinker (74.3% of a particle size less than 0.071 mm) weighing 300 g was processed in a dilute solution of sulfuric acid (1:1) at ambient temperature in a floatation machine at a mass phase ratio of L:S=1:1. The cake output was 48.7% (1.62% Cu; 22.2% Fe; 1.7% C; 788.5 g/t Ag). The foamy part output was 16.6% (42% C).
A fusion mixture sample comprising dried-up cake, weighing 100 g, and calcium oxide, CaO, weighing 22 g, mixed with an additive of the dried-up foamy phase resulting from Example 5 was melted in an induction furnace. The mass of the foamy phase was 7.5 g (i.e., 3.15 g of carbon). Melting was carried out by raising the temperature to 1350° C. The following results (product output and its chemical composition) were received:
The degree of copper extraction into matte-metal phase was 98.1%, and the degree of silver extraction was about 98%. The temperature of melting depends on carbon content, and in the shortage of carbon, the temperature for formation of molten metal approaches the melting point of pure iron. In this case, the temperature of melting can increase to 1500° C.
The melting temperature depends on what material is formed in the metallic phase. If the mass ratio of iron to carbon in the furnace is more than 14:1, then within the metal phase, sponge iron forms in addition to cast iron, which requires a melting temperature of 1500° C. A sufficient amount of carbon, however, leads to formation of only cast iron (or at least significantly less sponge iron, which decreases the melting temperature; cast iron has a melting temperature of 1200° C.). Thus, the amount of carbon in the furnace impacts the required melting temperature, which fluctuates between 1200 and 1500° C. The optimal melting temperature with a sufficient amount of carbon in the furnace is 1350° C. At this temperature the metal phase is in a melted state.
A sample of the matte-metal phase, weighing 15 g, resulting from Example 6 was dissolved in a dilute solution of sulfuric acid (1:1). At the same time as iron completely dissolved into the solution, the insoluble residue contained sulfides of non-ferrous metals and noble metals. The undissolved deposit output was 12.8% of the mass of the sample (1.92 g from 15 g). For a deposition of iron from the solution, the most expedient method was used—salting-out in the form of iron sulfate by addition of sulfuric acid.
From the results of the experiments discussed in the Examples, it is shown that the greatest extraction of non-ferrous metals from clinker and agglomerate in separate products is achieved by application of the flow diagram (see
In summary, the present invention comprises various embodiments for methods and systems for processing zinc production clinker (i.e. clinker, along with agglomerate, resulting from a zinc production plant). The methods and systems described herein, among others, may be described as follows:
A method for processing zinc production clinker, comprising: (1) providing a clinker from zinc production, said clinker comprising sulfur, carbon, iron, and non-ferrous metals, (2) pretreating said clinker in a solution, said solution comprising one or more inorganic acids, said pretreating resulting in a pulp having a floating foamy part, wherein said floating foamy part is removed from said pulp, (3) filtering said pulp, said filtering resulting in a first product comprising a cake and a second product comprising a first filtrate, wherein said second product is separated from said first product, wherein said first product is dried, and (4) melting said first product within a furnace, said melting resulting in a formation of a slag phase, a matte phase, a metal phase, and a gas phase, wherein the melting of said matte and metal phases occurs in an absence of any air delivery and in a presence of carbon, wherein said matte phase and said metal phase share a distribution of iron and non-ferrous metals.
In some aspects, the melting is performed while maintaining a mass ratio of iron to carbon of not greater than 14:1 within the furnace, such that said metal phase comprises more cast iron than sponge iron.
In some aspects, up to 80 percent of the carbon in the clinker is removed during said pretreating via removal of said floating foamy part from said pulp.
In some aspects, the method further comprises: dissolving said matte phase and said metal phase together in a solution, said solution comprising sulfuric acid, forming a metal-matte solution, and filtering said metal-matte solution to separate non-ferrous metals from said metal-matte solution, thus forming a second filtrate.
In some aspects, the method further comprises: salting out of iron sulphate from the second filtrate, said salting out comprising adding a solution of 96% sulfuric acid by weight to said second filtrate.
In some aspects, the absence of any air delivery is caused by a formation of a slag layer on a furnace surface, said slag layer blocking any access of air to said metal and matte phases located beneath said slag layer.
In some aspects, the solution comprising one or more inorganic acids comprises 49% sulfuric acid by weight.
In some aspects, the second product comprising a first filtrate is further processed with hydrogen sulfide to form a deposition of copper in a sulphidic form and a third filtrate, and the method further comprises salting out of iron sulphate from the third filtrate, said salting out comprising adding a solution of 96% sulfuric acid by weight to said third filtrate.
In some aspects, the hydrogen sulfide is a byproduct produced from a dissolving of said matte phase and said metal phase together in a solution, said solution comprising sulfuric acid.
In some aspects, calcium oxide (CaO) is added to said first product comprising a cake during melting, said calcium oxide having a mass ratio to iron, Ca:Fe, of 1:1 within the furnace.
In some aspects, the non-ferrous metals are copper, lead, silver, and gold.
In another embodiment, the method for processing zinc production clinker, comprises: (1) providing a clinker from zinc production, said clinker comprising sulfur, iron, carbon, and non-ferrous metals, (2) melting said clinker in a furnace, said melting resulting in a formation of a slag phase, a matte phase, a metal phase, and a gas phase, wherein the melting of said matte and metal phases occurs in an absence of any air delivery and in a presence of carbon, (3) wherein said melting is performed while maintaining a mass ratio of iron to carbon of not greater than 14:1, wherein said matte phase comprises a majority of said non-ferrous metals and said metal phase comprises a majority of said iron.
In some aspects, the method in the above paragraph further comprises dissolving said matte phase and said metal phase together in a solution, said solution comprising sulfuric acid, forming a metal-matte solution, and filtering said metal-matte solution to separate non-ferrous metals from said metal-matte solution, thus forming a filtrate, said filtrate comprising iron.
In some aspects, the method in the above paragraph even further comprises salting out of iron sulphate from the filtrate, said salting out comprising adding a solution of 96% sulfuric acid by weight to said filtrate.
In some aspects, the melting occurs at 1250-1350 degrees Celsius.
In some aspects, the metal phase comprises cast iron. In some aspects, the metal phase comprises more cast iron than sponge iron. In some aspects, the metal phase contains substantially no sponge iron.
Also disclosed is a system for processing zinc production clinker, the system comprising: (1) a supply unit for providing a clinker from zinc production, said clinker comprising sulfur, carbon, iron, and non-ferrous metals, (2) a pretreatment unit for pretreating said clinker in a solution, said solution comprising one or more inorganic acids, said pretreating resulting in a pulp having a floating foamy part, wherein said floating foamy part is removed from said pulp, (3) a pulp filtration unit for filtering said pulp, said filtering resulting in a first product comprising a cake and a second product comprising a first filtrate, wherein said second product is separated from said first product, wherein said first product is dried, and (4) a furnace (or other melting unit, e.g., a tub) for melting said first product within the furnace, said melting resulting in a formation of a slag phase, a matte phase, a metal phase, and a gas phase, wherein the melting of said matte and metal phases occurs in an absence of any air delivery and in a presence of carbon, wherein said matte phase and said metal phase share a distribution of iron and non-ferrous metals.
In some aspects, the melting is performed while maintaining a mass ratio of iron to carbon of not greater than 14:1 within the furnace (or other melting unit), such that said metal phase comprises more cast iron than sponge iron.
The advantage of the proposed method of processing polymetallic ferriferous metallurgical raw materials, in particular the agglomerate and clinker of zinc production, is a significant increase of the degree of extraction of copper and other non-ferrous metals, including but not limited to silver, gold, and lead.
The description of a preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in this art. It is intended that the scope of the invention be defined by the following claims and their equivalents.
Moreover, the words “example” or “exemplary” are used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, use of the words “example” or “exemplary” is intended to present concepts in a concrete fashion. As used in this application, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or”. That is, unless specified otherwise, or clear from context, “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, if X employs A; X employs B; or X employs both A and B, then “X employs A or B” is satisfied under any of the foregoing instances. In addition, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from context to be directed to a singular form.
