JP7565585B2 - Zinc carbonate manufacturing method - Google Patents

Description

The present invention relates to a method for producing zinc carbonate, and in particular to a method for producing zinc carbonate using so-called secondary dust as a raw material, such as electric furnace dust generated during the melting and smelting of scrap in the electric furnace process, which is one of the iron-making processes, secondary dust (crude zinc oxide) generated in a reduction furnace when part of the electric furnace dust is recycled as a zinc raw material, and secondary dust (crude zinc oxide) generated in the blast furnace process, which is one of the iron-making processes, and recovered as a zinc-containing oxide in a rotary hearth furnace.

In the electric furnace process, which is one of the steelmaking processes, electric furnace dust is generated as industrial waste containing zinc oxide and accounts for approximately 1.5% to 2.0% of the steel produced during the melting and smelting of scrap. It is said that 8 million tons of electric furnace dust are generated worldwide, and 400,000 tons are generated in Japan.

Most iron scrap comes from abandoned buildings, discarded home appliances, or scrapped automobiles. The paint base of abandoned buildings, discarded home appliances, or scrapped automobiles is zinc-plated. The scrap also contains paint, plastic, oil, etc. For this reason, electric furnace dust contains heavy metals such as zinc and lead, as well as harmful organic matter such as chlorides and dioxins. On the other hand, electric furnace dust contains about 20-30% iron and 20-30% zinc. Furthermore, crude zinc oxide contains about 10% iron and about 60% zinc. Therefore, electric furnace dust and secondary dust (crude zinc oxide) are very useful resources.

Under such circumstances, Patent Document 1 discloses a method for producing zinc bullion, which includes the steps of: producing a zinc-containing aqueous solution containing zinc components using electric furnace dust or secondary dust generated when electric furnace dust is reduced in a reduction furnace as a raw material; producing purified zinc chloride containing purified zinc chloride by converting the zinc components in the zinc-containing aqueous solution into zinc-containing compounds in at least one form of carbonate, hydroxide, and oxide, and chlorinating the zinc components of the zinc-containing compound; producing anhydrous molten purified zinc chloride containing anhydrous molten purified zinc chloride by anhydrousizing the purified zinc chloride; and producing zinc bullion as an electrolytic product by electrolyzing the anhydrous molten purified zinc chloride.

JP 2019-119895 A

However, according to the inventor's investigations, in the configuration disclosed in Patent Document 1, the filtrate obtained after separating zinc-containing compounds in at least one of the forms of carbonate, hydroxide, and oxide is repeatedly used as an alkaline agent for selectively extracting zinc components from electric furnace dust or secondary dust. However, since this only circulates the alkaline components remaining in the filtrate, there is room for improvement in terms of efficiently sending alkaline components in a more suitable form to the zinc extraction process.

In particular, according to the inventor's research, when electric furnace dust or secondary dust generated when electric furnace dust is reduced in a reduction furnace is used as the raw material, the zinc component in the raw material is selectively extracted using an aqueous alkali hydroxide solution as an extraction solvent, and the extracted zinc component is converted into a zinc-containing compound in the form of carbonate to produce zinc carbonate. In this case, alkali carbonate or alkali hydrogen carbonate components may be by-produced. However, if such by-products can be converted into alkali components that can extract the zinc component in the aqueous zinc-containing solution, it will be possible to efficiently use an alkali agent in a more appropriate form.

The present invention was made after the above-mentioned studies, and aims to provide a method for producing zinc carbonate in which, when zinc carbonate is produced by selectively extracting the zinc component in a zinc-containing aqueous solution produced using electric furnace dust or secondary dust generated when electric furnace dust is reduced in a reduction furnace as a raw material using an aqueous alkali hydroxide solution as an extraction solvent and converting the extracted zinc component into a zinc-containing compound in the form of carbonate, the by-produced alkali carbonate component or alkali hydrogen carbonate component can be converted into an alkali component that can extract the zinc component in the zinc-containing aqueous solution.

In order to achieve the above object, a method for producing zinc carbonate in a first aspect of the present invention is a method for producing zinc carbonate comprising: a zinc-containing aqueous solution producing step of selectively extracting a zinc component in electric furnace dust or secondary dust generated when the electric furnace dust is reduced in a reduction furnace as a raw material to produce a zinc-containing aqueous solution containing the zinc component; and a zinc carbonate separating step of separating the zinc component in the zinc-containing aqueous solution as zinc carbonate to obtain the zinc carbonate as a product, wherein an aqueous alkali hydroxide solution is used as an extraction solvent for selectively extracting the zinc component in the zinc-containing aqueous solution producing step, and a by-product alkali hydroxide component produced in the zinc carbonate separating step is converted into an alkali hydroxide component, and the alkali hydroxide component is converted into the zinc carbonate as a product. The method further includes an alkali regeneration step of sending the zinc-containing aqueous solution into the alkali hydroxide aqueous solution in the lead-containing aqueous solution production step, and in the zinc carbonate separation step, carbon dioxide is brought into contact with the zinc-containing aqueous solution to separate the zinc carbonate, and an alkali carbonate component or an alkali bicarbonate component is produced as the by-product alkali component. In the alkali regeneration step, calcium hydroxide is brought into contact with the alkali carbonate component or alkali bicarbonate component produced as the by-product in the zinc carbonate separation step to produce the alkali hydroxide component. The calcium hydroxide that is brought into contact with the alkali carbonate component or alkali bicarbonate component in the alkali regeneration step is obtained using the calcium component in the residue obtained in the zinc-containing aqueous solution production step .

In addition to the first aspect, the present invention further includes a substitution step of contacting the zinc-containing aqueous solution produced in the zinc-containing aqueous solution production step with metallic zinc to reduce and precipitate metal impurity components in the zinc-containing aqueous solution that are more noble than zinc, and the zinc carbonate separation step separates the zinc components in the zinc-containing aqueous solution that has been subjected to the substitution step as zinc carbonate, as a second aspect.

In addition to the first or second aspect, the present invention further comprises a deironization/demanganese step of contacting an oxidizing agent with the zinc-containing aqueous solution produced in the zinc-containing aqueous solution production step to separate iron and manganese components in the zinc-containing aqueous solution, and a substitution step of contacting metallic zinc with the zinc-containing aqueous solution that has been through the deironization/demanganese step to reduce and precipitate metal impurity components that are more noble than zinc in the zinc-containing aqueous solution, and the zinc carbonate separation step is a third aspect in which the zinc component in the zinc-containing aqueous solution that has been through the substitution step is separated as zinc carbonate.

According to the zinc carbonate manufacturing method of the first aspect of the present invention, an aqueous alkali hydroxide solution is used as an extraction solvent for selectively extracting the zinc component in the zinc-containing aqueous solution generating process, and an alkali regeneration process is further provided in which the by-product alkaline component generated in the zinc carbonate separation process is converted into an alkaline hydroxide component and the alkaline hydroxide component is sent to the aqueous alkali hydroxide solution in the zinc-containing aqueous solution generating process. Therefore, the by-product alkaline component can be converted into an alkaline component that can extract the zinc component in the zinc-containing aqueous solution, and zinc carbonate can be manufactured more efficiently by efficiently using an alkaline agent in a more suitable form.

In addition, according to the method for producing zinc carbonate in the first aspect of the present invention, in the zinc carbonate separation step, zinc carbonate is separated by contacting the zinc-containing aqueous solution with carbon dioxide, and an alkali carbonate or alkali hydrogen carbonate is produced as a by-product alkali component. In the alkali regeneration step, the alkali carbonate or alkali hydrogen carbonate produced as a by-product in the zinc carbonate separation step is brought into contact with calcium hydroxide to produce an alkali hydroxide. Therefore, the by-product alkali components such as sodium carbonate and sodium hydrogen carbonate are converted into an alkali component such as sodium hydroxide, and can be reused as an extraction solvent that can extract the zinc component in the zinc-containing aqueous solution. Therefore, the extraction solvent can be recycled without being discarded, and zinc carbonate can be produced more efficiently.

Furthermore, according to the method for producing zinc carbonate in the first aspect of the present invention, the calcium hydroxide that is brought into contact with the alkali carbonate or alkali hydrogencarbonate in the alkali regeneration step is obtained using the calcium component in the residue obtained in the zinc-containing aqueous solution production step, so that the calcium component in the raw material for the zinc-containing aqueous solution can be effectively utilized, and zinc carbonate can be produced more efficiently.

In addition, according to the second aspect of the present invention, the method for producing zinc carbonate further includes a substitution step of contacting the zinc-containing aqueous solution produced in the zinc-containing aqueous solution production step with metallic zinc to reduce and precipitate metal impurity components that are more noble than zinc in the zinc-containing aqueous solution, and a zinc carbonate separation step of separating the zinc components in the zinc-containing aqueous solution that has been subjected to the substitution step as zinc carbonate, thereby making it possible to stably mass-produce zinc carbonate with reduced metal impurity components with good yield.

In addition, according to the third aspect of the present invention, the method for producing zinc carbonate further includes a deironization/demanganization step of contacting an oxidizing agent with the zinc-containing aqueous solution produced in the zinc-containing aqueous solution production step to separate iron and manganese components in the zinc-containing aqueous solution, and a substitution step of contacting metallic zinc with the zinc-containing aqueous solution that has been subjected to the deironization/demanganization step to reduce and precipitate metal impurity components that are more noble than zinc in the zinc-containing aqueous solution. Since the zinc carbonate separation step separates the zinc components in the zinc-containing aqueous solution that has been subjected to the substitution step as zinc carbonate, zinc carbonate in which iron and manganese components are reduced can be mass-produced stably with good yield.

FIG. 1(a) is a process diagram of a method for producing zinc carbonate in a first embodiment of the present invention, and FIG. 1(b) is a process diagram for producing secondary dust that can be used as a raw material in the method for producing zinc carbonate in this embodiment. FIG. 2 is a process diagram of a method for producing zinc carbonate in a second embodiment of the present invention. FIG. 3 is a process diagram of a method for producing zinc carbonate according to a third embodiment of the present invention. FIG. 4 is Table 1 showing the results of an experimental example of the first embodiment of the present invention. FIG. 5 is Table 2 showing the results of an experimental example of the second embodiment of the present invention. FIG. 6 is Table 3 showing the results of an experimental example of the third embodiment of the present invention.

The zinc carbonate manufacturing method in each embodiment of the present invention will be described in detail below with appropriate reference to the drawings.

First Embodiment
First, a method for producing zinc carbonate according to a first embodiment of the present invention will be described in detail with reference to FIG.

Figure 1(a) is a diagram showing the steps of the method for producing zinc carbonate in this embodiment, and Figure 1(b) is a diagram showing the steps of producing secondary dust that can be used as a raw material in the method for producing zinc carbonate in this embodiment.

As shown in FIG. 1(a), in this embodiment, a zinc extraction process 101 and a zinc carbonate separation process 102 are carried out in sequence, and an alkali regeneration process 103 is also carried out. The zinc extraction process 101 corresponds to a zinc-containing aqueous solution production process. It is based on a manufacturing concept that prioritizes the production of an aqueous solution in which zinc components are extracted from electric furnace dust or secondary dust as a raw material, and produces zinc carbonate as a zinc-containing compound in the form of carbonate produced from the zinc components in the aqueous solution.

Specifically, first, in the zinc extraction process 101, electric furnace dust 1 as a raw material containing zinc-containing compounds such as zinc oxide and iron compounds such as iron oxide is directly contacted with an aqueous solution of an alkaline agent 3 as an extraction solvent for zinc, and the zinc component is selectively extracted from the zinc-containing compounds to produce a zinc extract solution containing the zinc component, a zinc-containing aqueous alkaline agent solution 5, and the solids that do not dissolve in the aqueous solution of the alkaline agent 3 are left as residue 4.

Typically, the chemical formula for obtaining a zinc-containing aqueous alkaline agent solution 5, which is a zinc-containing aqueous solution obtained by selectively extracting zinc components from zinc oxide in electric furnace dust 1 using sodium hydroxide as an alkaline agent 3, is shown in the following (Chemical Formula 1).

As the raw material used in the zinc extraction step 101, a secondary dust 2 obtained by reducing the electric furnace dust 1 in a reduction furnace may be used instead of the electric furnace dust 1. In addition, as the raw material used in the zinc extraction step 101, when the calcination step 104 shown in FIG. 1(b) is adopted,
Secondary dust 2 obtained by mixing and calcining electric furnace dust 1 with calcium carbonate 10 may also be used.
By such calcination, the zinc component contained in the zinc ferrite component of the electric furnace dust 1 can be converted into a zinc oxide component that is easily extracted with an alkaline agent. When the secondary dust 2 obtained by calcining the mixture of calcium carbonate 10 is used as a raw material, the calcium component in the residue 4 obtained in the zinc extraction step 101 can be increased. Furthermore, the carbon dioxide 6 obtained by such calcination can be used in the subsequent zinc carbonate separation step 102. Furthermore, secondary dust such as crude zinc hydroxide obtained from the electric furnace dust 1 may be used as the raw material used in the zinc extraction step 101.

Next, in the zinc carbonate separation process 102, the zinc-containing alkaline aqueous solution 5 containing the zinc component extracted in the zinc extraction process 101 is directly contacted with carbon dioxide (carbon dioxide gas) 6 to precipitate zinc carbonate 7 from the zinc-containing alkaline aqueous solution 5 containing the zinc component extracted in the zinc extraction process 101, which is then separated into solid and liquid and recovered as a solid, which is then used as the product as is.

Typically, carbon dioxide 6 is blown into the zinc component in a zinc-containing aqueous alkaline agent solution 5 shown in chemical formula (Chemical Formula 1) as shown in the following chemical formula (Chemical Formula 2) to precipitate zinc carbonate 7, and the precipitated zinc carbonate 7 is filtered to obtain zinc carbonate 7 as a solid content.

In the zinc carbonate separation step 102, a liquid containing carbonate ions may be used instead of the carbon dioxide 6 that is brought into contact with the zinc-containing alkaline agent aqueous solution 5. Also, as is clear from the chemical formula (chemical formula 2), in order for zinc hydroxide to dissolve in the alkaline aqueous solution, excess hydroxide ions are required. Therefore, in the zinc carbonate separation step 102, zinc hydroxide can be precipitated instead of the zinc carbonate 7 or together with the zinc carbonate. Since zinc carbonate and zinc hydroxide have the property of becoming zinc oxide when heated, a part of the zinc carbonate may be zinc oxide as well as zinc hydroxide. Also, by using techniques such as heating, cooling, and pH adjustment of the zinc-containing alkaline agent aqueous solution 5 containing the zinc component, the precipitation and re-dissolution of zinc carbonate and zinc hydroxide can be repeated, and a product of even higher purity can be obtained by actively utilizing the refining effect.

Here, in the alkali regeneration step 103, since the filtrate 8 after solid-liquid separation of the zinc carbonate 7 in the zinc carbonate separation step 102 contains by-product alkali carbonate components and alkali hydrogen carbonate components, these alkali carbonate components and alkali hydrogen carbonate components are converted into alkali hydroxide components, and the alkali agent 3 consisting of the converted alkali hydroxide components is returned to the aqueous solution of the alkali agent 3 in the zinc extraction step 101.

Typically, calcium hydroxide 9 is added to the filtrate 8 obtained after solid-liquid separation of zinc carbonate 7 in the zinc carbonate separation step 102 to convert sodium carbonate and sodium hydrogen carbonate into sodium hydroxide, and the sodium hydroxide thus converted is returned as the alkaline agent 3 to the aqueous solution of the alkaline agent 3 in the zinc extraction step 101. The chemical formula for obtaining sodium hydroxide from sodium carbonate and calcium hydroxide is shown in Chemical Formula 3 below.

In the alkali regeneration step 103, calcium hydroxide 9 containing a calcium component contained in the residue 4 obtained when the zinc-containing alkaline agent aqueous solution 5 is produced in the zinc extraction step 101 may be used as the calcium hydroxide 9 to be added to the filtrate 8 after solid-liquid separation of the zinc carbonate 7 in the zinc carbonate separation step 102. When the calcium component is contained in the electric furnace dust 1 or the secondary dust 2, it may be used as the calcium component in the residue 4. When the calcination step 104 in which calcium carbonate 10 is mixed with the electric furnace dust 1 and calcined is adopted, the calcium component derived from the calcium carbonate 10 may be used. In addition, not only calcium hydroxide derived from such a calcium component but also commercially available slaked lime may be used as the calcium hydroxide 9.

In the zinc carbonate manufacturing method of this embodiment described above, an aqueous alkali hydroxide solution is used as an extraction solvent for selectively extracting the zinc component in the zinc-containing aqueous solution generating step 101, and an alkali regeneration step 103 is further provided in which the by-product alkaline component generated in the zinc carbonate separation step 102 is converted into an alkaline hydroxide component and the alkaline hydroxide component is sent to the aqueous alkali hydroxide solution in the zinc-containing aqueous solution generating step. Therefore, the by-product alkaline component can be converted into an alkaline component that can extract the zinc component in the zinc-containing aqueous solution, and zinc carbonate can be manufactured more efficiently by efficiently using an alkaline agent in a more appropriate form.

In addition, in the zinc carbonate production method of this embodiment, zinc carbonate is separated by contacting the zinc-containing aqueous solution with carbon dioxide in the zinc carbonate separation step 102, and an alkali carbonate component or an alkali hydrogen carbonate component is produced as a by-product alkali component. The alkali hydroxide component is produced by contacting the alkali carbonate component or alkali hydrogen carbonate component produced by the zinc carbonate separation step 102 with calcium hydroxide in the alkali regeneration step 103. Therefore, the by-product alkali components such as sodium carbonate and sodium hydrogen carbonate are converted to alkali components such as sodium hydroxide and can be reused as an extraction solvent that can extract the zinc component in the zinc-containing aqueous solution. The extraction solvent can be recycled without being discarded, and zinc carbonate can be produced more efficiently.

In addition, in the zinc carbonate manufacturing method of this embodiment, the calcium hydroxide that is brought into contact with the alkali carbonate component or the alkali hydrogen carbonate component in the alkali regeneration step 103 is obtained using the calcium component in the residue obtained in the zinc-containing aqueous solution production step, so that the calcium in the raw material of the zinc-containing aqueous solution can be effectively utilized, and zinc carbonate can be produced more efficiently.

Second Embodiment
Next, a method for producing zinc carbonate according to a second embodiment of the present invention will be described in detail with reference to FIG.

Figure 2 shows the steps of the zinc carbonate manufacturing method in this embodiment.

As shown in FIG. 2, the zinc carbonate manufacturing method according to this embodiment differs from the zinc carbonate manufacturing method according to the first embodiment mainly in that it has a substitution process (cementation process) 105 between the zinc extraction process 101 and the zinc carbonate separation process 102. In this embodiment, the explanation will focus on this difference, and the same components are given the same reference numerals, and the explanation will be omitted or simplified.

Specifically, in the substitution process 105 following the zinc extraction process 101, the zinc-containing alkaline agent aqueous solution 5 serving as the zinc extract containing the zinc component extracted in the zinc extraction process 101 is directly contacted with metallic zinc 11 such as zinc fine particles, and metal impurity components 12 such as copper, lead, and cadmium, which are more noble than zinc in the zinc-containing alkaline agent aqueous solution 5, are reduced and precipitated, thereby reducing the concentration of impurity components in the zinc-containing alkaline agent aqueous solution 5.

Next, in the zinc carbonate separation process 102, the zinc-containing alkaline agent aqueous solution 13, the concentration of impurity components of which has been reduced in the substitution process 105, is contacted with carbon dioxide 6 to precipitate zinc carbonate 7 from the zinc-containing alkaline agent aqueous solution 13, which is then subjected to solid-liquid separation and recovered as a solid.

According to the method for producing zinc carbonate of this embodiment, in addition to the configuration of the first embodiment, the method further includes a substitution step 105 in which metallic zinc is brought into contact with the zinc-containing aqueous solution produced in the zinc-containing aqueous solution production step 101 to reduce and precipitate metal impurity components that are more noble than zinc in the zinc-containing aqueous solution, so that zinc carbonate with reduced metal impurity components can be mass-produced stably with good yield.

Third Embodiment
Next, a zinc carbonate manufacturing method according to a third embodiment of the present invention will be described in detail with reference to FIG.

Figure 3 shows the steps of the zinc carbonate manufacturing method in this embodiment.

As shown in FIG. 3, the main difference between the zinc carbonate manufacturing method according to this embodiment and the zinc carbonate manufacturing method according to the second embodiment is that the method has a deironization and demanganization step 106 between the zinc extraction step 101 and the replacement step 105. This embodiment will be described with a focus on this difference, and the same components will be given the same reference numerals and their description will be omitted or simplified.

In this embodiment, the provision of the de-ironization/de-manganese step 106 is particularly effective when the iron or manganese components contained in the electric furnace dust are alkali-soluble Fe(II) and Mn(II), and is also effective even when the iron or manganese components are alkali-insoluble, because when a zinc-containing aqueous solution in which alkali-insoluble Fe(III) and Mn(IV) are suspended is treated in the substitution step, they are reduced to alkali-soluble Fe(II) and dissolved in the zinc-containing aqueous solution. In addition, since alkali-soluble iron or manganese components may be generated in the substitution step 105, not only a substitution step may be provided after the de-ironization/de-manganese step, but also a substitution step may be provided before the de-ironization/de-manganese step. Specific methods for the de-ironization/de-manganese step 106 include aeration and oxidation by adding permanganate, and when the soluble manganese component is Mn(VII), a method of contacting with activated carbon may be used.

Specifically, in the de-ironization/de-manganeseization process 106 following the zinc extraction process 101, in order to remove the iron and soluble manganese contained in the zinc-containing alkaline agent aqueous solution 5 as the zinc extract containing the zinc component extracted in the zinc extraction process 101, the iron or soluble manganese contained in the zinc-containing alkaline agent aqueous solution 5 is oxidized, and the iron and manganese components in the zinc-containing alkaline agent aqueous solution 5 are separated and removed as insoluble precipitate sludge 17. Specifically, the zinc-containing alkaline agent aqueous solution 5 is oxidized to iron (II) components by blowing in oxygen-containing gas (e.g., air blowing, i.e., aeration), adding an oxidizing agent 15 such as permanganate, chlorate, or chlorine dioxide, etc., and the soluble manganese is oxidized and converted into an insoluble manganese compound, which is then separated and removed as sludge 17. In addition, the iron component in the zinc-containing alkaline agent aqueous solution 5 can be converted into a magnetic iron oxide such as maghemite, which contains both ferrous and ferric components, by controlling the temperature, alkali concentration, and oxidation-reduction potential (ORP) value.

When permanganate is used as the oxidizing agent 15, the end point of demanganization can be determined by supplying permanganate until excess permanganate remains in the zinc-containing alkaline agent aqueous solution 5, and the remaining permanganate is converted to insoluble manganese dioxide by direct contact with activated carbon and removed.

Next, in the substitution process 105, the zinc-containing alkaline agent aqueous solution 16, the concentration of which has been reduced in the iron removal/manganese removal process 106, is contacted with metallic zinc 11 such as zinc fine particles, and metallic impurity components 12, such as copper, lead, and cadmium, which are more noble than zinc in the zinc-containing alkaline agent aqueous solution 16, are reduced and precipitated, thereby further reducing the concentration of impurities in the zinc-containing alkaline agent aqueous solution 16.

Here, the order of carrying out the iron removal/demanganese process 106 and the replacement process 105 may be such that the replacement process 105 is followed by the iron removal/demanganese process 106. For example, when the raw material is a material that has been through an iron reduction process, such as secondary dust, the raw material may contain a large amount of divalent iron (Fe(II): ferrous component), and it is more reasonable to carry out the replacement process 105 first when processing such raw material. This is also true in an embodiment in which the iron removal/demanganese process 106 is separated into a deironization process and a demanganese process, each of which is carried out separately.

According to the zinc carbonate manufacturing method of this embodiment, in addition to the configuration of the second embodiment, it further includes a deironization/demanganese process 106 in which an oxidizing agent is brought into contact with the zinc-containing aqueous solution generated in the zinc-containing aqueous solution generation process 101 to separate the iron and manganese components in the zinc-containing aqueous solution, so that zinc carbonate with reduced iron and manganese components can be mass-produced stably with good yield.

Finally, in addition to the present embodiment described above, experimental examples that correspond to the first to third embodiments will be described in detail with reference to Figures 4 to 6.

Figure 4 is Table 1 showing the results of Experimental Example 1 of the first embodiment of the present invention, Figure 5 is Table 2 showing the results of Experimental Example 2 of the second embodiment of the present invention, and Figure 6 is Table 3 showing the results of Experimental Example 2 of the third embodiment of the present invention. Note that ND in the table indicates not detected. Also, blank spaces in the table indicate that electric furnace dust, secondary dust, and residue are below the detection limit or not detected, and that items other than electric furnace dust, secondary dust, and residue are not included in the analysis.

(Experimental Example 1)
This experimental example corresponds to the first embodiment of the present invention, and the results are shown in Table 1 of FIG.

First, in the zinc extraction step 101, 60.5 g of secondary dust 2 was taken from 870 g of secondary dust obtained by mixing and calcining 441 g of calcium carbonate and 762.8 g of electric furnace dust 1 in the calcination step 104, and the secondary dust 2 was contacted with a 16.5% NaOH aqueous solution as an aqueous solution of alkaline agent 3, and the solids that were not dissolved in the aqueous solution of alkaline agent 3 were separated by filtration to obtain a zinc extract (zinc-containing aqueous alkaline agent solution) 5 with a volume of 395 ml as the remaining liquid. In addition, the solids that were not dissolved in the aqueous solution of alkaline agent 3 were filtered, washed with pure water, and then dried to obtain a residue 4 with a weight of 43.3 g. The extraction conditions in the zinc extraction step 101 were a temperature of 95° C. and a pressure of normal pressure, and the contact time between the aqueous solution of alkaline agent 3 and the secondary dust 2 was 8 hours. The filtrate obtained by filtering off the residue 4 (the filtrate from which the extractable components were extracted from the insoluble solids) was repeatedly used as the alkaline agent 3 for dissolving the secondary dust 2, and the washing water obtained after washing the residue 4 with pure water was repeatedly used as dilution water in the purification process.

Next, in the zinc carbonate separation step 102, carbon dioxide 6 is blown into the zinc-containing alkaline agent aqueous solution 5 to precipitate zinc carbonate 7, and the zinc carbonate 7 is separated by suction and filtration using GF (glass fiber)/C filter paper, and this zinc carbonate 7 is used as the product. The carbon dioxide 6 used was generated by the decomposition of calcium carbonate 10 when the electric furnace dust 1 was calcined in the calcination step 104. The composition of the zinc carbonate 7 and other components is shown in Table 1, and for convenience, the value for zinc carbonate 7 is the analytical value of the zinc carbonate converted into zinc oxide during heating and drying.

In the alkali regeneration step 103, slaked lime 9 is brought into contact with the filtrate 8 from which the zinc carbonate 7 has been separated, and _Na2CO3 and _NaHCO3 , which are by-produced when carbon dioxide 6 is blown into the zinc-containing aqueous alkaline agent solution 5 in the zinc carbonate separation step 102, are converted to NaOH, and this NaOH is sent to the zinc extraction step 101 as the alkaline agent ₃ and repeatedly used for zinc extraction. The slaked lime 9 is a calcium component derived from the calcium carbonate 10 used when the electric furnace dust 1 is calcined in the calcination step 104, and is obtained by utilizing the calcium component contained in the residue 4 from the zinc extraction step 101.

(Experimental Example 2)
This experimental example corresponds to the second embodiment of the present invention, and the results are shown in Table 2 of FIG.

First, in the zinc extraction process 101, 100 g of secondary dust (crude zinc hydroxide sample) 2 derived from electric furnace dust 1 was contacted with a 16.5% NaOH aqueous solution as an aqueous solution of alkaline agent 3, and the entire amount was filtered after stirring. Next, the solids that did not dissolve in the aqueous solution of alkaline agent 3 were contacted with a new aqueous solution of NaOH as an aqueous solution of alkaline agent 3 with a concentration of 16.5%, and the entire amount was filtered after stirring. The solids that did not dissolve in the aqueous solution of each of these alkaline agents 3 were separated by filtration to obtain residue 4, and the remaining liquids from which residue 4 was separated were used to obtain zinc extraction solution (zinc-containing aqueous alkaline agent solution) 5 with a zinc concentration of 45,800 ppm. Note that the conditions such as temperature in the zinc extraction process 101 of this experimental example were the same as those of experimental example 1.

Next, in the substitution step 105, 5 g of powdered zinc particles 11 with an average particle size of about 6 μm was added to the zinc-containing alkaline agent aqueous solution 5, which was then heated and stirred. The stirred mixture was then aspirated and filtered through a membrane filter with a filtration accuracy of 0.1 μm, and the filtrate was obtained as the zinc-containing alkaline agent aqueous solution 13. The solid matter separated from the membrane filter was a mixture of metal powder 12 that had been reduced and precipitated as the zinc particles 11 dissolved, and the powdered zinc that remained undissolved.

Next, the zinc carbonate separation step 102 following the substitution step 105 was carried out in the same manner as in Experimental Example 1 using the zinc-containing alkaline agent aqueous solution 13, and the separated zinc carbonate 7 was used as the product as is. The composition of the zinc carbonate 7 obtained in this experimental example is as shown in Table 2, and compared to that in Experimental Example 1, it had reduced metal impurity components such as copper, lead, and cadmium. For convenience, the value for zinc carbonate 7 is the analytical value of the zinc carbonate converted to zinc oxide when heated and dried.

In the alkali regeneration step 103, calcium hydroxide 9 is brought into contact with the filtrate 8 remaining after separation of the _zinc carbonate _7, and Na2CO3 and _NaHCO3 produced as by-products when carbon dioxide 6 is blown into the zinc-containing aqueous alkaline agent solution 5 in the zinc carbonate separation step 102 are converted to NaOH, and this NaOH is sent to the zinc extraction step 101 as the alkaline agent 3 and repeatedly used for zinc extraction. The calcium hydroxide 9 used is a calcium component derived from the secondary dust 2 used in the zinc extraction step 101, and was obtained by utilizing the calcium component contained in the residue 4 of the zinc extraction step 101.

(Experimental Example 3)
This experimental example corresponds to the third embodiment of the present invention, and the results are shown in Table 3 of FIG.

First, in the zinc extraction process 101, the secondary dust (crude zinc hydroxide sample) 2 with a weight of 300 g derived from the electric furnace dust 1 was contacted with an aqueous NaOH solution with a concentration of 16.5% as an aqueous solution of the alkaline agent 3, stirred, and the entire amount was filtered to obtain a zinc extraction solution (zinc-containing aqueous alkaline agent solution) 5 with a volume of 1800 ml as the remaining liquid after separating the solid matter that does not dissolve in the aqueous solution of the alkaline agent 3. Next, the solid matter that did not dissolve in the aqueous solution of the alkaline agent 3 was contacted with an aqueous NaOH solution with a concentration of 16.5% as a new aqueous solution of the alkaline agent 3, stirred, and the entire amount was filtered to separate the solid matter that does not dissolve in the aqueous solution of the alkaline agent 3 by filtration to obtain a residue 2 with a weight of 161 g. The conditions in the zinc extraction process 101 in this experimental example were the same as those in experimental example 1.

Next, in the de-ironization and de-manganization process 106 following the zinc extraction process 101, air was blown into the zinc-containing alkaline agent aqueous solution 5 as an oxidizing agent 11 under heating to precipitate a brown precipitate, which was then aspirated and filtered through a membrane filter with a filtration accuracy of 0.1 μm to obtain a filtrate (de-ironized and de-manganized zinc-containing alkaline agent aqueous solution 16). As the solid content on the filter paper, de-ironized and de-manganized sludge 17 weighing 263 mg was obtained.

Next, the substitution process 103 following the iron removal/manganese removal process 106 was carried out using the zinc-containing alkaline agent aqueous solution 16 in the same manner as in Experimental Example 2, and the zinc carbonate separation process 102 and the alkali regeneration process 103 were carried out in the same manner as in Experimental Example 2, with the zinc carbonate 7 separated in the zinc carbonate separation process 102 being used as the product as is. The composition of the zinc carbonate 7 obtained in this experiment is as shown in Table 3, and compared to that in Experimental Example 2, the amount of metal impurities such as iron and manganese was reduced. For convenience, the value for zinc carbonate 7 is the analytical value of the zinc oxide converted during heating and drying.

The shape, arrangement, number, etc. of the components of the present invention are not limited to those of the above-mentioned embodiment, and such components can of course be appropriately modified without departing from the spirit of the invention, such as by appropriately replacing such components with components that provide equivalent effects.

As described above, the present invention provides a method for producing zinc carbonate in which the zinc component in a zinc-containing aqueous solution produced using electric furnace dust or secondary dust generated when electric furnace dust is reduced in a reduction furnace is selectively extracted using an aqueous alkali hydroxide solution as an extraction solvent, and the extracted zinc component is converted into a zinc-containing compound in the form of carbonate to produce zinc carbonate. Therefore, due to its versatile and universal nature, it is expected to be widely applicable to a method for producing zinc carbonate using electric furnace dust generated during the melting and smelting of scrap in the electric furnace process, which is one of the iron-making processes, or secondary dust generated in a reduction furnace when part of the electric furnace dust is recycled as an iron-making raw material.

Reference Signs List 1...Electric furnace dust 2...Secondary dust 3...Alkaline agent 4...Residue 5...Zinc-containing alkaline agent aqueous solution 6...Carbon dioxide 7...Zinc carbonate 8...Filtrate 9...Calcium hydroxide 10...Calcium carbonate 11...Zinc particles 12...Metal impurity components 13...Zinc-containing alkaline agent aqueous solution 15...Oxidizing agent 16...Zinc-containing alkaline agent aqueous solution 17...Sludge 101...Zinc-containing aqueous solution production process 101...Zinc extraction process 102...Zinc carbonate separation process 103...Alkaline regeneration process 104...Caking process 105...Substitution process 106...Iron removal and demanganese process

Claims (8)

a zinc-containing aqueous solution producing step of selectively extracting zinc components from electric furnace dust or secondary dust generated when the electric furnace dust is reduced in a reducing furnace as a raw material to produce a zinc-containing aqueous solution containing the zinc components;
a zinc carbonate separation step of separating the zinc component in the zinc-containing aqueous solution as zinc carbonate to obtain the zinc carbonate as a product;
A method for producing zinc carbonate comprising:
An aqueous solution of an alkali hydroxide is used as an extraction solvent for selectively extracting the zinc component in the zinc-containing aqueous solution producing step,
The method further includes an alkali regeneration step of converting the by-product alkali component generated in the zinc carbonate separation step into an alkali hydroxide component, and feeding the alkali hydroxide component into the alkali hydroxide aqueous solution in the zinc-containing aqueous solution generation step ,
In the zinc carbonate separation step, carbon dioxide is brought into contact with the zinc-containing aqueous solution to separate the zinc carbonate and generate an alkali carbonate component or an alkali hydrogen carbonate component as the by-product alkali component;
the alkali carbonate component or the alkali hydrogencarbonate component by-produced in the zinc carbonate separation step is contacted with calcium hydroxide in the alkali regeneration step to produce the alkali hydroxide component;
The calcium hydroxide to be contacted with the alkali carbonate or the alkali hydrogencarbonate in the alkali regeneration step is obtained using the calcium component in the residue obtained in the zinc-containing aqueous solution production step . The method further includes a substitution step of contacting the zinc-containing aqueous solution produced in the zinc-containing aqueous solution production step with metallic zinc to reduce and precipitate metal impurity components more noble than zinc in the zinc-containing aqueous solution,
2. The method for producing zinc carbonate according to claim 1 , wherein the zinc carbonate separation step separates the zinc component in the zinc-containing aqueous solution that has been subjected to the substitution step as the zinc carbonate. a deironization/demanganese process in which the zinc-containing aqueous solution produced in the zinc-containing aqueous solution production process is contacted with an oxidizing agent to separate iron components and manganese components in the zinc-containing aqueous solution;
a substitution step of contacting the zinc-containing aqueous solution that has been subjected to the iron and manganese removal step with metallic zinc to reduce and precipitate metal impurity components that are more noble than zinc in the zinc-containing aqueous solution;
and
3. The method for producing zinc carbonate according to claim 1, wherein the zinc carbonate separation step separates the zinc component in the zinc-containing aqueous solution that has been subjected to the substitution step as the zinc carbonate. 4. The method for producing zinc carbonate according to claim 1, wherein calcined dust obtained in a calcination step of mixing calcium carbonate with the electric furnace dust and calcining the mixture is used as the raw material in the zinc-containing aqueous solution production step. 5. The method for producing zinc carbonate according to claim 4, wherein in the zinc carbonate separation step, the zinc-containing aqueous solution is contacted with carbon dioxide obtained in the calcination step to separate the zinc carbonate. 6. The method for producing zinc carbonate according to claim 4 or 5, wherein the calcium hydroxide brought into contact with the alkali carbonate or the alkali hydrogencarbonate in the alkali regeneration step is obtained using a calcium component derived from the calcium carbonate used in the calcination step. 7. The method for producing zinc carbonate according to claim 1, wherein in the zinc-containing aqueous solution producing step, the raw material is contacted with the aqueous alkali hydroxide solution, followed by filtration, and a solid component that is not dissolved in the aqueous alkali hydroxide solution is separated from the aqueous alkali hydroxide solution to obtain the aqueous zinc-containing solution. 8. The method for producing zinc carbonate according to claim 1, wherein the filtrate obtained by contacting the raw material with the aqueous alkali hydroxide solution and filtering the mixture in the zinc-containing aqueous solution producing step is repeatedly used as the extraction solvent for selectively extracting the zinc component.

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