FI122447B - A process for utilizing the sulfur-containing effluent from the leaching of sulfide concentrates - Google Patents

Description

METHOD FOR UTILIZING THE SULFUR-RELATED REMOVAL FROM SOLUTION OF SULPHIDE CONCENTRATES

FIELD OF THE INVENTION

The invention relates to a process for treating iron and sulfur-containing effluents, i.e. leaching wastes, from the leaching of sulfidic non-ferrous metal concentrates. The sulfur-containing leaching residue or part thereof is sent to a fluidized bed treatment, in which the sulfur contained in the leaching waste is burned to sulfur dioxide and the precious metals contained in the leaching waste are mainly recovered as oxides and recycled to the metal recovery process.

BACKGROUND OF THE INVENTION

Hydrometallurgical treatment processes of sulfide concentrates containing non-ferrous metals in which at least one desired precious metal is leached directly from the rich tea yields elemental sulfur-containing effluents which still contain some of the precious metals. In addition to one or more precious metals, the sulphide ores and concentrates generally contain iron. Sulfur-containing effluents are formed, for example, in the direct leaching of zinc sulphide concentrate, when the sulphide in the concentrate forms elemental sulfur in the leaching. The elemental sulfur is separated from the iron precipitate of the solution-20 residue by flotation and the resulting sulfur concentrate contains 60-80% elemental sulfur. In addition to sulfur, the concentrate contains sulfides of various metals (including Fe, Zn, Pb and Cu), smaller amounts of sulfates (Fe, Pb, Ca) and also quartz and / or silicates. Depending on the sulfide concentrate to be solubilized, the sulfur concentrate may contain more valuable metals, such as silver.

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Sulphide concentrates of non-ferrous metals are also processed pyrometallurgically by tritium bed technology: copper sulphide concentrates are partially roasted at a temperature of about 600 ° C, Co, Ni, Cu and Fe-rich concentrates by selective sulphate desired roasting at about 680 ° C and passed er 30 roasting at 900-950 ° C. During roasting, sulfides are oxidized to either sulfates or oxides depending on the roasting method used. When oxides are formed in the roasting process, the sulfur 2 contained in the sulfide is oxidized to sulfur dioxide and is generally led to the production of sulfuric acid, provided that its concentration in the gas is sufficient for economic production.

When the 5 roasters used in particular for roasting a sulphidic non-ferrous metal concentrate are driven up after stoppages, heating takes place in several stages. The first step is usually performed with oil burners to about 400 ° C and then to about 800 ° C with either oil or coal. This produces fossil fuels that produce CCV-containing gases that also contain impurities from the bed. The carbon dioxide produced by heating cannot be led to an acid plant because its SO 2 content is too low.

The fluidized bed technology used in roasting is also utilized in the processing of various types of waste, whereby the incineration of the waste material is generally carried out using carbonaceous material.

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It is also known in the art to produce iron sulfide ore to produce sulfuric acid, which is crushed, milled and enriched into pyrite, FeS2 and / or pyrrhotite, FeS, which is burned in a fluidized bed at 800 to 850 ° C to produce sulfuric acid gas. Sanctum 20 and pyrrhotite mainly contain iron (26-46% Fe) and sulfur (30-52% S). Burning produces purple ore, which is mainly eliminated because it contains impurities that prevent its recovery.

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The methods described above are not fully environmentally friendly, because direct leaching of sulfide concentrate produces sulfur-containing leaching waste, which is a demanding disposal in its own storage area. When incineration is performed

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carbonaceous materials, in turn, produce S carbon dioxide that is released into the environment. The production of sulfuric acid from pyrite requires its own costs.

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g takes care of it and the purple ore is stored.

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PURPOSE OF THE INVENTION

The purpose of the process according to the invention is to utilize in various ways the sulfur-containing effluent obtained by dissolving sulphide concentrates by burning and oxidizing it in a fluidized bed. First, when the sulfur-containing effluent from leaching of the sulfide non-ferrous metals 5 is incinerated in a fluidized bed, the valuable metals contained in the effluent are recovered in addition to the SO 2 -containing gas. Second, the sulfur-containing effluent can be used as a fuel for heating the fluidized bed furnace, whereby the sulfur dioxide content of the gases produced can be sufficiently increased to lead the gases to sulfuric acid production. In addition, the energy generated by the combustion of sulfur is recovered in a 10 heat recovery boiler. Post-treatment of the sulfur-containing effluent in a fluidized bed is environmentally friendly because it reduces the need for storage and does not produce carbon dioxide. Because the sulfur dioxide produced is diverted to sulfuric acid production, less virgin ore is needed to produce sulfuric acid, which consequently reduces the cost of mining and processing.

SUMMARY OF THE INVENTION

The essential features of the invention will be apparent from the appended claims.

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The invention relates to a process for treating leaching waste containing iron and sulfur produced by leaching sulfidic non-ferrous metal concentrates. According to the method, the sulfur-containing leaching waste is led to a fluidized bed treatment in which the sulfur contained in the leaching waste is burned to sulfur dioxide and the precious metals contained in the leaching waste are oxidized to oxide or sulfate and

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is led to a metal recovery process.

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S) According to one embodiment of the process, iron and sulfur-containing g leaching residue is treated to separate iron and sulfur and to form sulfur concentrate containing elemental sulfur c3 30.

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According to one embodiment of the invention, the sulfur concentrate is filtered and dried and the fine concentrate is passed to a sand bed fluidized bed furnace, where the sulfur of the concentrate is oxidized to sulfur dioxide and precious metals to oxide or sulfate recovered from gas scrubbing and vacuum boiler.

When the sulfur concentrate is filtered and dried and introduced into a fluidized bed furnace equipped with a sand bed, during the roasting process, the contaminated sand bed sand is fed to a non-ferrous metal smelting agent.

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According to a second and third mode of operation of the invention, the sulfur concentrate is either only partially dried or introduced as a water slurry into a fluidized bed furnace, whereby the roast of the concentrate oxidation

One typical leaching process for a sulphidic non-ferrous metal concentrate is a direct zinc leaching process in which precious metals, in addition to zinc, are silver, copper and 20 lead.

In the process of the invention, the iron in the leaching residue is in the form of sulfide or g of jarosite.

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According to one embodiment of the invention, the sulfur concentrate is separated

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from the leaching residue by flotation.

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In the process according to the invention, the temperature of the fluidized bed furnace is adjusted to be in the range of 750 to 870 ° C and the oxygen coefficient in the range of 1.1 to 1.5.

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According to an embodiment of the process according to the invention, the heat generated by the incineration of the leaching waste is used to maintain the temperature of the fluidized bed furnace and to generate energy.

According to yet another embodiment of the invention, the heat generated in the oxidation of the sulfur concentrate is used to maintain the temperature of the fluidized bed furnace and to generate energy.

LIST OF FIGURES

Figure 1 is a flow chart of an embodiment of the method of the invention, Figure 2 is a flow diagram of another embodiment of the method of the invention, and Figure 3 is a flow diagram of a third embodiment of the invention. 15

DETAILED DESCRIPTION OF THE INVENTION

The process according to the invention is based on utilizing the sulfur-containing effluent from the hydrometallurgical treatment of the sulphidic non-ferrous metal concentrate by burning it in a fluidized bed to form a sulfur dioxide-containing gas suitable for the production of sulfuric acid or pure elemental sulfur. At the same time, the precious metals remaining in the effluent are separated and formed into a form where they can be recycled to a suitable g recovery process. The amount of effluent to be stored in fluidized bed treatment is substantially reduced. Oxidation and / or combustion of the sulfur-containing effluent in a dj T 25 fluidised bed avoids the formation of climate-damaging carbon dioxide while

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^ energy is produced, for example, for drying and heating. When SCV content-

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The gas for sulfuric acid production is produced from the effluent, correspondingly reducing the need for sulfuric acid production from iron sulfide ore.

sj-o σ> o g 30 When the invention refers to effluent or sulfur-containing effluent, it refers to leaching waste containing iron, sulfur and other impurities from the hydrometallurgical preparation of sulphidic non-ferrous metal concentrates, which must be stored. Sulfur concentrate means a sulfur-containing material which has been separated from the above removal by suitable means, such as flotation. Final removal refers to the material to be removed from the fluidized bed treatment from which the sulfur and precious metals have been removed. The final 5 effluent consists mainly of iron oxides, quartz and silicates. For example, in the treatment of zinc leaching, precious metal means not only zinc but also silver, copper and lead in zinc concentrates.

As stated above, sulfur concentrate contains 60-80% elemental sulfur. It has been found in laboratory tests that fine sulfur concentrate (dso 10-18 pm) containing elemental sulfur, sulphides, sulphates, silicate and quartz is not suitable as such for processing in normal zinc or iron sulphide processing. When sulfur concentrate is treated with fluidized bed technology, it requires its own process of determining impurities such as Cu and Pb to determine the temperature and oxygen factor range to be used. Here are a few alternatives for treating the effluent by the process of the invention.

An alternative to the process of the invention is described in Flow Flow 1. The zinc production process produces sulfur and iron-containing leaching residues, from which the elemental sulfur and the precious metal sulfur concentrate are separated by any suitable means, such as flotation. The separated sulfur concentrate o is subjected to filtration 1 and drying 2 prior to fluidized bed treatment. When sulfur-rich

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^ is completely dried, finely divided and cannot be fluidized

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^ 25 furnace bed, but sand is preferred as the bed material. The sulfur contained in the sulfur concentrate is burned in the fluidized bed of the fluidized bed furnace 3 to sulfur dioxide,

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£ which is removed from the top of the furnace with the fluidizing gas. Most of the impurities contained in the sulfur o) concentrate leave the furnace with the gas stream 8 and are recovered as dust from the waste heat boiler 4 and the electric filter ESP 5.

Refined sulfur dioxide gas is fed to a sulfuric acid plant 6.

The dust from the waste heat boiler and electric filter mainly contains zinc in the sulfur concentrate as zinc oxide or zinc sulphate, which can be derived either from the 7 leaching steps of the zinc process or from its own leaching process. The drying of the sulfur concentrate is preferably carried out with steam from a waste heat boiler.

A small part of the impurities remains in the sand bed. When the fluidized bed is adjusted within a low operating temperature range of operating soil, such as 750 to 870 ° C, the bed temperature is adjusted to control the amount of material remaining in the sand bed. For example, at a bed temperature of about 850 ° C, the zinc content of the bed can be increased to about 15% by weight of the bed and maintained at this value by removing contaminated sand from the bed and replacing it with clean sand. The produced contaminant-10 witch sand is recycled to a non-ferrous metal smelter, such as a copper smelter, to form slag forming material, whereby the silver and copper bonded to the sand are recovered along with the copper in the smelter feed. The amount of sand to be recycled to the smelter is small in relation to the total amount of slag forming material and the zinc content of the recycled sand 15 does not significantly increase the zinc content of the feed. Combustion in a fluidized bed takes place with the help of air as in the roasting of zinc sulphide and pyrite, but due to the impurities the oxygen coefficient is adjusted higher than in the case of zinc sulphide roasting, ie to be of the order of 1.1-1.5. However, the temperature in the fluidized bed is significantly lower than, for example, the normal roasting of zinc sulphide concentrate.

Another variation of the process according to the invention is illustrated in flow diagram 2. The sulfur concentrate formed in the zinc production process is subjected to filtration 7 as in the alternative of Fig. 1, but dried i

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V 25 8 is only partially executed. In this case, too, the drying is carried out with the help of steam from a waste heat boiler. For the purpose of partial drying

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£ it is to leave part of the moisture, for example 10-18%, in the sulfur concentrate, thus utilizing the agglomeration mechanism of the moist finely divided material. Laboratory experiments have found that burning the moist sulfur concentrate at the correct temperature and with the right oxygen factor produces a micro-agglomerated bed. Thus, when the partially dried material is fed to the fluidized bed of the fluidized bed furnace 9, it forms micropellets which also serve as bedding material. Thus, no separate sand bed is required. As a result, the material to be removed from the bed is mainly zinc pellet, ZnO, which also contains hematite, Fe 2 CO 3, and quartz, SiO 2. The roast may be fed directly into the leaching steps of the zinc process or in its own leaching process. It has been found that the amount of roasting produced is 20-40% of the amount of sulfur concentrate, and when the roasting is fed to some stage of the zinc leaching process, in addition to zinc, lead and silver are also recovered. The gas to be removed from the fluidized bed is led, as described above, through the waste heat boiler 10 and the electric filter 11 to the sulfuric acid plant 12. The dust from the waste heat boiler and the electric filter 10 is also conducted to the leaching steps of the zinc process.

A third embodiment of the method of the invention is illustrated by flow diagram 3. Because of the high calorific value of the sulfur concentrate generated in the zinc production process, it is not necessary to filter and dry the concentrate in separate steps, but feed the slurry as an aqueous slurry into the fluidized bed 13, thereby saving on the costs of filtration and drying. The moisture of the concentrate is evaporated by the energy produced by oxidation and the solid forms micropellets during roasting when operated under correct temperature and oxygen pressure conditions. The amount of zinc pellet produced in the fluidized bed is 20 to 40% of the sulfur concentrate and can be led to some of the leaching steps of the zinc process. Also in this method, other valuable metals such as lead and silver are recovered in addition to zinc. The resulting sulfur dioxide-containing gas is fed through a waste heat boiler 14 and an electric filter 15 to a sulfuric acid plant 25. The dust from the waste heat boiler and the electric filter is recycled to the zinc process leaching steps.

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S The above-described alternatives to the process of the invention are based on an operating model in which the sulfur concentrate is separated from the iron precipitate before

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«M 30 incineration of concentrate in fluidized bed. According to another embodiment of the invention, the effluent from the zinc process containing both the iron precipitate and the element is not separated into two fractions, but the entire amount of effluent 9 is fed to the fluidized bed, whereupon the sulfur is burned to sulfur dioxide and metals oxidized to oxide or sulfate. This option also saves the costs of flotation. The feed can be carried out as shown in Figures 1 to 3, either wholly or partially in the form of a dry slurry or as an aqueous slurry. If the iron precipitate is zinc-containing sulfide or Jaro silicon, MFe3 (SO4) 2 (OH) 6, where M is, for example, an ammonium or alkali metal ion, the amount of sulfur dioxide gas produced by fluidized bed treatment is significantly higher than when sulfur concentrate alone is fed. Fluid bed treatment results in a roasting product containing zinc flake (ZnO), 10 hematite and quartz, and this product is subjected to its own leaching process.

According to a further embodiment of the invention, the dried leaching residue or sulfur concentrate is used to replace the oil or carbon used for the heating of the zinc free, whereby the resulting sulfur dioxide-containing gas can be introduced earlier to the acid plant. This approach reduces both the amount of final disposal stored and the amount of organic fuel otherwise used for heating.

The temperature used in the above-described treatment of sulfur concentrate or sulfur concentrate and iron slurry fluid bed 20 is determined by the low temperature melt phase forming products and intermediates. At the temperatures of the fluidized bed furnace, the metals contained in the zinc concentrate form complex systems comprising g and oxides and sulfides together and separately and melting at low temperatures. Especially when using a sand bed,

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v The number of metal compounds adhered to the sand bed determines how

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^ much of the bed needs to be removed as a function of time. Different elements and different

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Roasting of material containing grain sizes always requires its own temperature range and oxygen factor.

sj- o O) o ° 30 CM ou 10 EXAMPLES Example 1

Hydrometallurgical zinc production produces 100,000 t / year of finely divided (d50 10-18 pm) sulfur concentrate with a moisture content of 35% 5 H2O. The zinc content of the dry sulfur concentrate is in the order of 5%, which means 5000 t of zinc per year. The sulfur content of the sulfur concentrate is in the order of 70%. 100,000 t / a sulfur concentrate means about 12, 5 t / h. The theoretical oxygen demand for the combustion of sulfur concentrate is about 500 Nm3 per ton of sulfur concentrate, which still represents 2380 Nm3 air / t concentrate. Assuming 10 an oxygen factor of λ = 1.5, the air requirement for combustion is approximately 45,000 Nm3 / h.

When proceeding as in Figure 1, the sulfur concentrate is dried by steam generated in a waste heat boiler and oxidized in a fluidized bed furnace with a 15-bed sand bed. Only a small percentage of the metals contained in the sulfur concentrate remain in the sand bed and most are recovered from the waste heat boiler and the electric filter. The temperature of the bed largely determines how much zinc, for example, remains in the sand bed. For example, at 850 ° C, the zinc content of the sand bed can be increased to 15%. Assuming that 60% of the zinc 20 will remain in the sand bed, this would mean that 20 000 t of zinc-containing sand will be produced per year. For example, the copper smelter uses sand as a slag generating agent, and the resulting sand can be fed to the smelter, whereby the copper and silver contained in it, typically about 0.03%, are recovered as well as zinc.

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Proceeding as in Figure 2 and drying the sulfur concentrate to 15% moisture

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H 2 O, according to the results of studies, under fluidized bed conditions S at about 800 ° C, forms micropellets, as in normal zinc concentrate g roasting, and no separate sand bed is required. Sulfur concentrate oxidation

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30 zinc pellets (ZnO) are formed, which also contains hematite and quartz. The amount of zinc roast is about 30% of the sulfur concentrate and can be fed into the leaching step of the zinc recovery process. Thus, the zinc contained in the sulfur concentrate and also the silver are recovered.

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Claims (12)

A process for treating solution residue which arises in the solution of sulfidic non-ferrous metal concentrate and containing iron and sulfur, characterized in that the sulfur-containing solution residue is led to fluidized bed treatment, in which the sulfur contained in the solution residue is burnt to the sulfur dioxide. None of the value metals are oxidized to oxide or sulfate and is led to a process for metal recovery. 10 Process according to claim 1, characterized in that the solution residue containing iron and sulfur is treated for separation of iron and sulfur and for the formation of sulfur concentrate containing elemental sulfur. 15 3. A process according to claim 2, characterized in that the sulfur concentrate is filtered and dried and the finely divided concentrate is passed to a sand-bed vortex furnace, in which the sulfur of the concentrate is oxidized to sulfur dioxide and the heating metals to oxide or sulfate collected in connection with gas. the waste heat boiler and the electric filter dust and from the sand bed. 4. A process according to claim 2, characterized in that the sulfur concentrate is filtered and dried and conducted to a fluidized bed with a sand-bed, and the sand-bed contaminated in connection with the roasting is measured as the slag-forming substance of the non-ferrous metal smelter. 30 5. A process according to claim 2, characterized in that the sulfur concentrate is only partially dried or passed as a water suspension to a fluidized bed furnace, wherein the rusting material formed in the furnace upon the oxidation of the concentrate forms a fluidized bed in which the sulfur of the concentrate is oxidized to sulfur dioxide and the oxidized stainless steel and in connection with the gas purification from the waste heat boiler and the electric filter dust. 5 Process according to Claim 1, characterized in that the solution process of the sulphidic non-ferrous metal concentrate is a process for the direct dissolution of zinc. 10 Process according to claims 1 and 6, characterized in that the value metals besides zinc are silver, copper and lead. 8. A process according to claim 1, characterized in that the iron of the solution residue is in the form of sulphide or jarosite. 9. A process according to claim 2, characterized in that the sulfur concentrate is separated from the solution residue by flotation. 20 10. A process according to claim 1, characterized in that the temperature of the fluidized bed furnace is controlled to a range between 750 and 870 ° C and the oxygen coefficient to a range between 1.1 and 1.5. 11. A method according to claim 1, characterized in that heat which arises in connection with the combustion of the solution residue is used for maintaining the temperature of the fluidized bed furnace and for the production of energy. 12. A process according to claim 3, characterized in that heat generated in connection with the oxidation of the sulfur concentrate is used for maintaining the temperature of the fluidized bed furnace and for the production of energy.