JP2023054389A - Cadmium production method - Google Patents

Abstract

To efficiently separate and recover cadmium from a "cadmium sulfide-containing material" by a simpler process than a conventionally known multi-stage wet process.SOLUTION: A cadmium production method is provided, comprising: a reduction roasting step S10 of roasting a cadmium sulfide-containing material together with other raw material containing zinc and chlorine in a reduction atmosphere; a wet step S20 of distributing cadmium chloride obtained in the reduction roasting step S10 into a liquid phase, and distributing a zinc oxide and a cadmium oxide into a solid phase, thereby separating both of them; a cementation step S30 of adding zinc powder to a cadmium solution obtained by distributing the cadmium chloride into the liquid phase in the wet step S20, thereby precipitating metal cadmium; and a dehydration step S40 of solid-liquid separating a slurry including the metal cadmium precipitated from the solution in the cementation step S30, thereby obtaining a metal cadmium-containing dehydrated cake.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a method for producing cadmium, which separates and recovers metallic cadmium from raw materials containing cadmium sulfide.

In many non-ferrous metal smelting processes, a dewatered cake containing cadmium sulfide is discharged as a smelting intermediate. As a method for recovering metallic cadmium as a valuable metal from the dehydrated cake containing cadmium sulfide, a production method has been proposed in which multistage wet treatment is performed while adding various chemicals (Patent Document 1).

However, in the process disclosed in Patent Document 1, the processing time and the labor of processing such as management of the amount of various kinds of chemicals added at each stage in the multi-stage wet processing, pH control at each stage, etc. Due to its bulkiness, the production cost of cadmium has been forced to rise. Therefore, a simpler process has been desired as a "manufacturing method for separating and recovering metallic cadmium from raw materials containing cadmium sulfide".

JP 2007-191782 A

As an example, the present invention separates and recovers "metal cadmium" from "cadmium sulfide-containing raw materials" such as "dehydrated cake containing cadmium sulfide" discharged as a smelting intermediate in a non-ferrous metal smelting process such as copper refining. It is an object of the present invention to provide a "method for producing cadmium" capable of efficiently separating and recovering cadmium as a valuable metal by a process that is simpler than conventionally known multistage wet processes.

The present inventors have found that a dehydrated cake containing cadmium sulfide, prior to its introduction into a wet process, undergoes pretreatment with other raw materials containing zinc and chlorine into a reduction roasting process, The present inventors have newly found that the above problems can be solved, and have completed the present invention. More specifically, the present invention provides the following.

(1) A method for producing cadmium by separating and recovering metallic cadmium from a cadmium sulfide-containing raw material, comprising a reduction roasting step of roasting the cadmium sulfide-containing raw material together with other raw materials containing zinc and chlorine in a reducing atmosphere. , Treated water is added to the dust containing cadmium chloride obtained in the reduction roasting step, and zinc oxide and cadmium oxide reoxidized after reduction to convert the cadmium chloride into a liquid phase, the zinc oxide and the cadmium oxide Cementation to precipitate metal cadmium by adding zinc powder to the cadmium solution in which the cadmium chloride is distributed in the liquid phase in the wet process in which the two are separated by distributing into the solid phase. and a dehydration step of solid-liquid separating a slurry containing metallic cadmium precipitated from the solution in the cementation step to obtain a dehydrated cake containing metallic cadmium.

According to the method for producing cadmium in (1), metallic cadmium is efficiently separated from a "raw material containing cadmium sulfide" such as a "dehydrated cake containing cadmium sulfide" by a simpler process than a conventionally known multistage wet process. can be recovered.

(2) a dry heating step of drying and heating the dehydrated cake containing cadmium oxide and chlorine distributed in the solid phase in the wet process; and an exhaust gas treatment step of treating the exhaust gas discharged from the dry heating step. The method for producing cadmium according to (1), further comprising repeating the exhaust gas-derived dust containing cadmium chloride recovered in the exhaust gas treatment step in the wet process.

According to the method for producing cadmium of (2), cadmium can be separated and recovered more efficiently with a higher separation and recovery rate than the method of producing cadmium described in (1).

(3) A method for producing metallic cadmium, wherein metallic cadmium is obtained by acid-leaching cadmium from the metallic cadmium-containing dehydrated cake obtained by the method for producing cadmium according to (1) or (2).

According to the method for producing metallic cadmium of (3), high-grade metallic cadmium can be obtained very easily from the dehydrated cake containing metallic cadmium that can be obtained by the method for producing cadmium according to (1) or (2). be able to.

According to the present invention, a process for separating and recovering "metallic cadmium" from a "raw material containing cadmium sulfide", which is simpler than the conventionally known multistage wet process, efficiently separates and recovers cadmium as a valuable metal. It is possible to provide a “method for producing cadmium” that can be used.

BRIEF DESCRIPTION OF THE DRAWINGS It is a flowchart which shows an example of the flow of "the manufacturing method of cadmium" of this invention.

<Overall composition>
As shown in FIG. 1, the "method for producing cadmium" of the present invention comprises a cadmium sulfide-containing raw material such as a "dehydrated cake containing cadmium sulfide", which is subjected to a reduction roasting step S10, a wet process S20, a cementation step S30, and a dehydration step S10. This is a process for separating and recovering "metallic cadmium" by putting it into a composite process having step S40 as an essential step.

Further, the "method for producing cadmium" of the present invention further includes a drying heating step S50 and an exhaust gas treatment step S60 in addition to the above four steps, and the exhaust gas-derived dust recovered in the exhaust gas treatment step S60 is more preferably repeated in the wet process S20. The drying and heating step S50 and the exhaust gas treatment step S60 are not necessarily essential constituent elements of the present invention, but hereinafter, the reduction roasting step S10, the wet process S20, the cementation step S30, the dehydration step S40, the drying and heating step S50, and the exhaust gas An embodiment comprising six steps of the treatment step S60 will be described in detail as a preferred embodiment of the "method for producing cadmium" of the present invention.

Further, according to the "method for producing cadmium" of the present invention, a dehydrated cake containing sufficiently high-grade metallic cadmium ("dehydrated cake containing metallic cadmium") can be obtained. High-purity metallic cadmium can be easily obtained from the "metallic cadmium-containing dehydrated cake" obtained by the method" by a simple acid leaching treatment.

In addition, the composite process consisting of the above-mentioned reduction roasting step S10, wet process S20, cementation step S30, dehydration step S40, drying heating step S50, and exhaust gas treatment step S60 is performed through the reduction roasting step of the Wertz process. It can be implemented in existing zinc oxide manufacturing facilities that have a process to recover zinc oxide from dust. However, in the above zinc oxide production facility, cadmium, which is inevitably mixed in iron and steel dust, etc., which is the main raw material of zinc oxide, should be mixed in the final product (ferrous clinker) obtained in the reduction roasting process. is strictly controlled so that its content does not exceed a certain percentage. Specifically, various efforts have been made to reduce the cadmium content of the iron-containing clinker to less than 0.1%. Therefore, for those skilled in the art who manufacture zinc oxide, it is clearly assumed that the above-described "cadmium sulfide-containing raw material" containing cadmium sulfide as a main component is introduced into the process of performing the reduction roasting step of the Welts process. It was an outside processing mode.

<Reduction roasting process>
The reduction roasting step S10 is a step of roasting the “cadmium sulfide-containing raw material” together with “other raw materials containing zinc and chlorine” in a reducing atmosphere. As used herein, the term "raw material containing cadmium sulfide" is mainly intended to mean "dehydrated cake containing cadmium sulfide" discharged as a smelting intermediate in the non-ferrous metal smelting process. However, the "cadmium sulfide-containing raw material" is not limited to the dehydrated cake described above, and may be any other powder or slurry containing cadmium sulfide as a main component. In addition, the above-mentioned "zinc and other raw materials containing chlorine" may be those containing zinc or zinc compounds and chlorine or chlorine compounds. Iron and steel dust, which is

The reduction roasting step S10 can be performed using a reduction roasting rotary kiln (RRK) known as an apparatus for performing the reduction roasting step of the Welts process described above. In this rotary kiln (RRK), the zinc oxide (ZnO) contained in each of the above raw materials is reduced and roasted, and the volatilized metallic zinc is then re-oxidized in the exhaust gas to form powdery zinc oxide (ZnO). becomes. Similarly, most of the cadmium contained in each of the raw materials described above becomes a cadmium compound containing cadmium chloride (CdCl ₂ ) as a main component. These zinc oxide (ZnO) and cadmium chloride (CdCl ₂ ) are captured by a dust collector together with the exhaust gas from the rotary kiln and recovered as "dust containing cadmium chloride (CdCl ₂ ) and zinc oxide (ZnO)".

<Wet process>
In the wet process S20, the “dust containing cadmium chloride (CdCl ₂ ) and zinc oxide (ZnO)” collected in the reduction roasting step S10 is subjected to a wet process, thereby removing chlorides such as cadmium chloride (CdCl ₂ ). It is a process that separates substances into a liquid phase and oxides such as zinc oxide (ZnO) and cadmium oxide (CdO) into a solid phase.

Specifically, the wet process S20 slurries the above-described "dust containing cadmium chloride ( _CdCl2 ) and zinc oxide (ZnO)" by repulping with treated water. By this repulping, water-soluble chlorides such as cadmium chloride (CdCl ₂ ) in the dust are distributed into the treatment liquid. Fresh water, process water used in the process, or the like can be used as the treated water used for this repulp.

Most of the cadmium components present as chlorides in the "dust containing cadmium chloride (CdCl ₂ ) and zinc oxide (ZnO)" are partitioned into the liquid phase by the repulping process described above. Then, by performing a solid-liquid separation process in this state, the liquid phase in which the cadmium component is distributed at a high concentration is separated and recovered. As a specific device for performing dehydration treatment for solid-liquid separation, a well-known dewatering device such as a gravity sedimentation type slurry concentration device such as a thickener or a vacuum dehydrator can be appropriately selected and used.

<Cementation process>
In the cementation step S30, zinc (Zn) powder is added to the cadmium solution obtained by distributing cadmium chloride (CdCl ₂ ) in the liquid phase in the wet step S20. It is a step of depositing metallic cadmium by cementation treatment that advances the reaction (precipitation of cadmium) that occurs. This cementation treatment can be performed using, for example, various known reaction tanks having a stirrer.
Cd ²⁺ +Zn→Cd+Zn ²⁺ (Formula 1)

<Dehydration process>
The dehydration step S40 is a step of subjecting the slurry containing metallic cadmium precipitated from the solution in the cementation step S30 to a solid-liquid separation treatment to obtain a dehydrated cake containing metallic cadmium (dehydrated cake containing metallic cadmium). The specific method of the solid-liquid separation treatment is not particularly limited, and various known methods can be selected. A method of passing liquid through a press can be mentioned.

<Drying and heating process>
In the drying and heating step S50, the dehydrated cake containing oxides distributed in the solid phase in the wet process S20 is put into a drying and heating device and baked to convert the cadmium component contained in the dehydrated cake into chloride. This is a step of removing by volatilization. A known dry heating rotary kiln (DRK) can be used as the drying heating device for performing the drying heating step S50. The calcined ore after calcination and recovery of cadmium components and the like is used as crude zinc oxide as a raw material for zinc smelters.

<Exhaust gas treatment process>
The exhaust gas treatment step S60 is a step of separating and recovering dust from the exhaust gas discharged from the drying and heating step S50. Here, in the dehydrated cake introduced in the drying and heating step S50, in addition to zinc oxide, part of the cadmium introduced in the reduction roasting step S10 is reduced and volatilized like zinc to become an oxide. In addition, it contains chlorine, etc., which is dropped along with the moisture contained in the dehydrated cake. Therefore, the exhaust gas discharged from the drying and heating step S50 contains cadmium chloride (CdCl ₂ ) volatilized in the drying and heating step S50. The exhaust gas-derived dust separated and recovered from the exhaust gas in the exhaust gas treatment step S60 contains recovered cadmium chloride (CdCl ₂ ). It is possible to further increase the recovery rate of metallic cadmium from raw materials containing cadmium as a main component. This exhaust gas treatment step S60 can be performed in a known exhaust gas treatment facility including a wet type electrostatic precipitator and the like.

<Method for producing metallic cadmium>
The "dehydrated cake containing metallic cadmium" obtained by the "method for producing cadmium" of the present invention described above is used as a raw material, and cadmium or a cadmium compound is acid-leached from this raw material to easily produce high-grade metallic cadmium. Obtainable.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

<Example>
As a test run of the example, a test run of obtaining metallic cadmium from a cadmium sulfide-containing raw material was carried out under the following conditions according to the "method for producing cadmium" of the present invention. In this test operation, the six steps of the reduction roasting step, the wet step, the cementation step, the dehydration step, the drying heating step, and the exhaust gas treatment step were performed in the above-described manner, and the dehydrated product containing metallic cadmium obtained in this composite process was used. Cadmium metal was finally recovered from the cake (dehydrated cake containing cadmium metal) by acid leaching.

A sulfide containing 20% by mass of cadmium and 20% by mass of zinc was used as the "raw material containing cadmium sulfide" to be put into the reduction roasting process. Steel dust was used as "another raw material containing zinc and chlorine". Then, these raw materials were mixed with 200 t/day of iron and steel dust and 2 t/day of "cadmium sulfide-containing raw material" and put into a reduction roasting rotary kiln. In the reduction roasting rotary kiln, as reducing agents, 25% by mass of coke breeze relative to steel dust and 14% by mass of fine limestone relative to steel dust were also added. The temperature inside the reduction roasting rotary kiln was 1400°C.

In the reduction roasting process performed under the above conditions, as shown in Table 1 below, 98% or more of the cadmium in the "cadmium sulfide-containing raw material" was recovered. The dust containing cadmium and zinc recovered in the reduction roasting process was then subjected to a wet process, a cementation process, and a dehydration process, and was recovered as a "metal cadmium-containing dehydrated cake" capable of being acid leached. Further, the dehydrated cake containing zinc oxide distributed to the solid phase side in the wet process is put into the drying heating process and subjected to drying heating treatment, and the exhaust gas discharged from this drying heating process is sent to the exhaust gas treatment process, The dust contained in the exhaust gas was separated and recovered as exhaust gas-derived dust by a wet electrostatic precipitator, and the wet process was repeated for treatment. From the "dehydrated cake containing metallic cadmium" thus obtained, metallic cadmium was recovered by an acid leaching treatment. The recovery rate of cadmium in the "cadmium sulfide-containing raw material" through the entire process described above was 97% or more, as shown in Table 1 below.

<Comparative example>
A test operation was performed as a comparative example under the same conditions as in the example except that no reducing agent (coke fine) was added. In the roasting process without a reducing atmosphere, the recovery rate of cadmium in the "raw material containing cadmium sulfide" was 10%, as shown in Table 1 below. In addition, the recovery rate of cadmium in the "cadmium sulfide-containing raw material" through the entire process described above was 9% as shown in Table 1 below.

From the results of each of the above test operations, the reduction roasting process of roasting the cadmium sulfide-containing raw material in a reducing atmosphere together with other raw materials containing zinc and chlorine is performed prior to the wet process. It was confirmed that the recovery rate of cadmium from the raw material is dramatically improved, and that the effect of improving the recovery rate of cadmium is hardly exhibited when the roasting is not performed in a reducing atmosphere.

S10 reduction roasting process S20 wet process S30 cementation process S40 dehydration process S50 drying and heating process S60 exhaust gas treatment process

Claims (3)

A method for producing cadmium by separating and recovering metallic cadmium from a raw material containing cadmium sulfide,
a reducing roasting step of roasting the cadmium sulfide-containing raw material together with other raw materials containing zinc and chlorine in a reducing atmosphere;
Treated water is added to the dust containing cadmium chloride obtained in the reduction roasting step, and zinc oxide and cadmium oxide reoxidized after reduction to convert the cadmium chloride into a liquid phase, and the zinc oxide and the cadmium oxide. a wet process in which the two are separated by partitioning on a solid phase;
a cementation step of precipitating metal cadmium by adding zinc powder to the cadmium solution in which the cadmium chloride is distributed in the liquid phase in the wet step;
a dehydration step of solid-liquid separation of the slurry containing metallic cadmium precipitated from the solution in the cementation step to obtain a dehydrated cake containing metallic cadmium;
A method for producing cadmium, comprising: Further comprising a dry heating step of drying and heating the dehydrated cake containing cadmium oxide and chlorine distributed in the solid phase in the wet process, and an exhaust gas treatment step of treating the exhaust gas discharged from the dry heating step,
Repeating the exhaust gas-derived dust containing cadmium chloride recovered in the exhaust gas treatment step to the wet process;
The method for producing cadmium according to claim 1. A method for producing metallic cadmium, wherein metallic cadmium is obtained by acid leaching cadmium from the dehydrated cake containing metallic cadmium obtained by the method for producing cadmium according to claim 1 or 2.

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