JP7151404B2 - Method for producing zinc oxide ore - Google Patents

Description

The present invention relates to a method for producing zinc oxide ore. More particularly, it relates to a method for producing zinc oxide ore, which includes a process of volatilizing and separating and recovering zinc components by a reduction roasting process, and capable of maintaining a high zinc recovery rate.

Conventionally, zinc oxide ore obtained by separating and removing impurities from zinc-containing ore such as crude zinc oxide has been widely used as a raw material for zinc ingots in zinc smelters.

Crude zinc oxide dust, which is a raw material for zinc oxide ore, can be obtained, for example, by subjecting zinc-containing ores such as steel dust generated from blast furnaces, electric furnaces, etc. in the steel industry to reduction roasting treatment. The reduction roasting treatment of steel dust or the like is generally carried out by reduction roasting treatment using a rotary kiln.

When reduction roasting is performed by a rotary kiln, steel dust used as a raw material is put into the rotary kiln together with a carbonaceous reducing agent such as carbon and limestone as a composition adjusting agent. In addition, in order to further improve the recovery rate of zinc, it is also widely practiced to mix the steel dust to be introduced into the rotary kiln with a carbonaceous reducing agent in advance and form pellets of the reducing agent-containing type with a size of about 5 to 10 mm. This is being done (see Patent Document 1).

In the rotary kiln that performs the reduction roasting process (hereinafter also referred to as “reduction roasting rotary kiln (RRK)” in this specification), the maximum temperature is about 1050 to 1200 ° C. due to the combustion of fuel heavy oil and the above carbonaceous reducing agent. controlled. In this reduction roasting rotary kiln (RRK), the steel dust is reduction roasted, and the volatilized metallic zinc is re-oxidized and solidified in the kiln, and then collected as particulate coarse zinc oxide dust by an electric dust collector or the like. be collected. The recovered crude zinc oxide dust is subjected to a subsequent wet process and a dry heating process to further separate impurities and raise the quality of zinc to a required level to obtain zinc oxide ore, which is used as a raw material for zinc ingots. Become.

The zinc grade of zinc oxide ore, which is the final product, is required to be higher than a certain level. Specifically, for example, when zinc oxide ore is used as a raw material for zinc smelting by the ISP smelting method or the like, it is necessary to raise the zinc grade of the zinc oxide ore to a value allowed in each smelting process. be.

However, in order to further improve the zinc recovery rate during the reduction roasting treatment, when the above materials are pelletized, the types of steel dust and carbon pelletized are constant, and they are homogeneous. It has been empirically known that the recovery rate of zinc may not always be stably maintained at a desired level in the reduction roasting process even if it is mixed in.

Limestone, which is a composition adjustment agent, has the effect of suppressing the growth of _vegetation in the kiln by adjusting the melting point of the remaining matter in the kiln, that is, the volatile residue. There is an effect of promoting the reduction of zinc by the CO gas generated at . However, an increase in the amount of limestone added is advantageous in that the recovery rate of zinc can be further increased, but it increases the elution value of heavy metals from ferruginous clinker, which is a volatile residue produced from the kiln. It is not preferable in terms of point and limestone cost increase.

Therefore, a method for producing zinc oxide ore that can further stably improve the recovery rate of zinc in the reduction roasting process at the production site of zinc oxide ore using pellets made of materials such as iron and steel dust and carbon as raw materials. was sought.

JP 2015-120948 A

In the production of zinc oxide ore using pellets made of materials such as iron and steel dust and carbon as raw materials, the present invention provides an oxidation method that can stably maintain the zinc recovery rate in the reduction roasting process at a desired level. An object of the present invention is to provide a method for producing zinc ore.

In the process of producing zinc oxide ore from zinc-containing ore such as crude zinc oxide, pellets, which are a kneaded product of steel dust and a carbonaceous reducing agent such as carbon, are preferably used as raw materials to be input to the reduction roasting process. It is The present inventors have found that the zinc recovery rate in the reduction roasting process can be stably improved by kneading limestone at the same time when preparing pellets to be put into the reduction roasting process. I have perfected my invention. More specifically, the present invention provides the following.

(1) A pre-mixing step of obtaining pellets for reduction roasting by mixing and granulating raw ore containing zinc oxide and other additive materials, and subjecting the pellets for reduction roasting to reduction roasting treatment. and a reduction roasting step of obtaining crude zinc oxide dust, wherein the pellets for reduction roasting are pellets obtained by mixing and granulating iron and steel dust, a carbonaceous reducing agent, and limestone. A method for producing zinc oxide ore, characterized by:

(2) The method for producing zinc oxide ore according to (1), wherein the raw material ore is steel dust.

(3) The oxidation according to (1) or (2), wherein the content of limestone in the pellets for reduction roasting is 2.0 parts by weight or more and 10.0 parts by weight or less per 100 parts by weight of the raw material ore. Method for producing zinc ore.

(4) a wet process of subjecting the crude zinc oxide dust to a wet process to remove water-soluble impurities to obtain a crude zinc oxide cake; and a dry heat process of subjecting the crude zinc oxide cake to a dry heat process. The method for producing zinc oxide ore according to any one of (1) to (3), comprising:

(5) Pellets for reduction roasting to be fed into the reduction roasting process as a raw material for zinc oxide ore, the pellets containing raw ore containing zinc oxide, a carbonaceous reducing agent, and limestone.

According to the present invention, in the production of zinc oxide ore using pellets made of materials such as iron and steel dust and carbon as raw materials, it is possible to further stably maintain the recovery rate of zinc in the reduction roasting process at a desirable level. It is possible to provide a method for producing zinc oxide ore.

BRIEF DESCRIPTION OF THE DRAWINGS It is a flowchart which shows an example of the manufacturing method of zinc oxide ore of this invention.

An embodiment of the present invention will be described below with reference to the drawings.

<Overall process>
The method for producing zinc oxide ore of the present invention includes a preliminary mixing step S10 for obtaining "pellets for reduction roasting" having a composition unique to the present invention, and reduction roasting of the "pellets for reduction roasting" to produce crude zinc oxide. It is a production method comprising at least the reduction roasting step S20 to obtain.

Further, as shown in FIG. 1, in the method for producing zinc oxide ore of the present invention, in addition to the preliminary mixing step S10 and the reduction roasting step S20, the crude zinc oxide obtained in the reduction roasting step S20 is For example, a wet process S30 in which halogen components such as fluorine and water-soluble impurities such as cadmium are separated and removed in the treatment liquid to obtain a crude zinc oxide cake, and the crude zinc oxide cake obtained in the wet process S30 is dried and heated to oxidize. An overall process comprising a drying heating step S40 for obtaining zinc ore, an exhaust gas dust cleaning step S50 for cleaning exhaust gas dust generated in the drying heating step S40 to obtain a cleaned exhaust gas dust cake, and a waste water treatment step S60. , the preferred embodiment of which is a manufacturing method.

In the method for producing zinc oxide ore of the present invention, particularly in the preliminary mixing step S10, not only a reducing agent but also a conventional reduction roasting is added to the raw material pellets mainly composed of steel dust to be put into a reduction roasting rotary kiln (RRK). This production method stably improves the recovery rate of zinc in the reduction roasting process by preliminarily incorporating limestone that has been separately charged into the rotary kiln (RRK). According to this production method, it is possible to maintain the zinc grade of zinc oxide ore, which is a raw material to be fed into zinc smelting, within a high range. For example, zinc oxide ore with extremely high zinc grade, which can be preferably used as zinc oxide ore for electrolytic smelting, can be produced with high productivity.

<Pre-mixing step>
In the preliminary mixing step S10, prior to the reduction roasting step S20, raw material ore such as steel dust, a carbonaceous reducing agent such as recycled carbon, and a composition adjusting agent mainly composed of limestone are mixed and granulated. , a step of obtaining a "reduction roasting pellet" containing a reducing agent and limestone. This mixed granulation operation, so-called pelletizing, can be performed using a commonly used pelletizing device, more specifically, a rotary pan-type pelletizer or a twin-axis non-uniform pin-type granulator. Using a machine, iron and steel dust, recycled carbon, and limestone are continuously supplied so as to have a predetermined pellet composition, and the above materials are mixed and granulated while adding water in the form of mist. can.

The size of the "reduction roasting pellets" is preferably in the range of about 1 mm to 20 mm in order to improve the zinc recovery rate in addition to ease of handling, and in the range of about 5 mm to 10 mm It is more preferable to have If the size of the "reduction roasting pellets" is less than about 1 mm, there is a problem that it will carry over when it is put into a reduction roasting rotary kiln (RRK), and if it exceeds about 20 mm, the zinc recovery rate will deteriorate. unfavorable in

Moreover, the moisture content of the pellets for reduction roasting is preferably in the range of about 10% by mass or more and 15% by mass or less in order to control the particle size in addition to the conditions for granulation.

As raw material ores, various raw materials containing zinc and other valuable metals at a ratio of a predetermined amount or more and containing fluorine or the like to be removed as impurities at a predetermined amount or less can be used. Dust and sludge generated in metal smelting and processing processes, which can be pelletized, or in the form of slurry can also be used. Among them, iron and steel dust can be preferably used from the viewpoint of promotion of resource recycling and cost reduction. An embodiment of the method for producing zinc oxide ore according to the present invention in which steel dust is used as raw material ore for crude zinc oxide or the like will be described below.

When iron and steel dust is used as the raw material ore, there is no particular limitation, and iron and steel dust (hereinafter also referred to as "steel dust A") that generally has a high zinc grade and therefore has a relatively low zinc recovery rate under general reducing roasting conditions. There may be. Such iron and steel dust A is also made into a "reduction roasting pellet" unique to the present invention in which a reducing agent and limestone are incorporated in advance in the preliminary mixing step S10, so that the zinc recovery rate is relatively high. High general iron and steel dust (hereinafter also referred to as “steel dust B”) is introduced into the reduction roasting furnace without a carbonaceous reducing agent and limestone, and zinc is volatilized with a high recovery rate. can be recovered.

As the carbonaceous reducing agent, carbon, recycled carbon, or the like, which can be pelletized, can be used as a powder or slurry. Among them, recycled carbon can be preferably used from the viewpoint of promotion of resource recycling and cost reduction. An embodiment in which recycled carbon is used as the carbonaceous reducing agent in the preliminary mixing step S10 of the zinc oxide ore production method of the present invention will be described below.

The carbon content of the "reduction roasting pellets" to be put into a reduction roasting rotary kiln (RRK) is preferably 5.0% by mass or more and 12.0% by mass or less, and 5.0% by mass or more. It is more preferably 0% by mass or less. By setting the carbon content of the "reduction roasting pellets" within the above range, the effect of improving the zinc recovery rate of iron and steel dust by adopting "reduction roasting pellets" can be stably enjoyed at a high level. be able to. When the carbon content of the “pellets for reduction roasting” is less than 5.0% by mass, the effect of improving the reduction rate of zinc oxide due to pelletization is insufficient. Also, if the carbon content exceeds 10.0% by mass, the rate of increase in the reduction rate gradually decreases, resulting in a decrease in cost effectiveness, which is not preferable.

As limestone, it is preferable to use limestone having a particle size of 0.1 mm or more and 5 mm or less. This makes it easier to uniformly disperse the limestone in the pellets when mixing and granulating the "pellets for reduction roasting".

Regarding the amount of limestone added to the "reduction roasting pellets" to be put into the reduction roasting rotary kiln (RRK), the content of limestone in the reduction roasting pellets is 2.0 parts by weight per 100 parts by weight of the raw material ore. It is preferable to set the amount to be added so as to be 1 part or more and 10.0 parts or less by weight. Here, the raw material ore mentioned above is raw material ore such as iron and steel dust, and refers to all raw materials including repeated materials.

If the content of limestone in the pellets for reduction roasting is less than 2.0 parts by weight per 100 parts by weight of raw material ore, the reduction rate of zinc oxide by pelletization tends to be insufficient. On the other hand, if the content exceeds 10.0 parts by weight, the ratio cannot be lowered when the CaO/SiO ₂ of the iron-containing clinker increases due to fluctuations in the raw material composition, so the upper limit is 10.0 parts by weight. It is preferable to make it below a part.

Here, the adjustment of CaO / SiO ₂ of the iron-containing clinker produced from the reduction roasting process, that is, the adjustment of the melting point of the retentate in the kiln (volatile residue) is performed separately from the limestone incorporated in the "pellet for reduction roasting". This is done by adjusting the amount of limestone additionally added in the reduction roasting process. And this additional charge of limestone is, more particularly, _FeO- It is determined by determining the composition ratio of CaO—SiO ₂ and determining the content of limestone (CaCO ₃ ) that is lacking in the raw material ore based on the FeO, SiO ₂ , and CaO contents of the raw material ore. In this case, if the content of limestone in the pellets for reduction roasting exceeds 10.0 parts by weight per 100 parts by weight of raw material ore, the amount of limestone additionally introduced in the reduction roasting process is , even if it is 0, a situation in which CaO becomes excessive may occur. This is the reason why the CaO/SiO ₂ ratio of the iron-containing clinker cannot be lowered when the limestone content in the pellets for reduction roasting exceeds 10.0 parts by weight.

The main purpose of adding limestone to raw material ore in zinc oxide ore manufacturing process is composition adjustment. From that point of view, it is not strictly required that the limestone be uniformly mixed with the raw material ore. Therefore, conventionally, limestone has been added separately from pellets, which are a kneaded product of steel dust and a carbonaceous reducing agent such as carbon. On the other hand, in the present invention, in order to maximize the reducing effect of limestone, limestone is homogeneously mixed with steel dust and a carbonaceous reducing agent such as carbon, and limestone is mixed with steel dust and carbon such as carbon. It was made to exist in the very vicinity of the reducing agent. As a result, while avoiding the excessive addition of limestone, it has become possible to make the most effective use of limestone for reduction in addition to its original purpose of adjusting the composition.

<Reduction roasting process>
As a specific method for performing the reduction roasting step S20, a reduction roasting method using a reduction roasting rotary kiln (RRK) is generally adopted. In the reduction roasting step S20, the "reduction roasting pellets" obtained in the pre-mixing step S10 are continuously fed into a reduction roasting rotary kiln (RRK) together with an additional reducing agent and limestone. At this time, in addition to the iron and steel dust A used as "pellets for reduction roasting", iron and steel dust B, which has a relatively high zinc recovery rate, is added to the reduction roasting rotary kiln ( RRK) may be similarly injected. In this case, the iron and steel dust B is also preferably formed into pellets having a size of about 5 to 10 mm in advance, if necessary.

In the furnace of this reduction roasting rotary kiln (RRK), the maximum temperature of the material to be treated is controlled within the range of about 1050° C. or higher and 1200° C. or lower by combustion of heavy oil and combustion of charged carbonaceous reducing agent. In this furnace, the "reduction roasting pellets" containing the iron and steel dust A and the iron and steel dust B are both reduced and roasted, and the volatilized metallic zinc is re-oxidized in the furnace to form powdery oxidation. becomes zinc. Powdery zinc oxide is introduced into a dust collector together with exhaust gas from a reduction roasting rotary kiln (RRK), captured and recovered as crude zinc oxide dust.

According to the production method of the present invention, high-quality crude zinc oxide dust can be obtained by stably increasing the zinc recovery rate in the reduction roasting step S20. Specifically, in the reduction roasting step S20, by using the “reduction roasting pellets” having a composition unique to the present invention, the limestone to be introduced in the reduction roasting step is granulated from the raw ore in the pre-mixing step S10. Compared to the case where the same amount of limestone is separately added to the reduction roasting rotary kiln (RRK) without being mixed with the pellets, the recovery rate of zinc in this reduction roasting step S20 is improved by 2.0% or more. It is possible to As a result, for example, high-grade zinc oxide ore that can be preferably used for zinc smelting by electrolytic smelting can be efficiently produced at a lower cost than before. Moreover, since the content of zinc in the iron-containing clinker, which is a byproduct, can be reduced, it is possible to stably produce high-quality iron-containing clinker.

In this specification, the "recovery rate of zinc in the reduction roasting process" refers to the amount of zinc contained in the "reduction roasting pellets" and steel dust that are put into the reduction roasting process, and the reduction roasting rotary kiln. (RRK) refers to the ratio of the amount of zinc contained in the crude zinc oxide dust volatilized and recovered. In addition, this "zinc recovery rate in the reduction roasting process" is based on the zinc content in the raw material "reduction roasting pellets" and steel dust, and the iron-containing clinker discharged from the reduction roasting rotary kiln (RRK). can be calculated from the analytical values obtained by measuring the zinc content of each with a fluorescent X-ray spectrometer and the amount of each material.

In addition, the reduction roasting residue remaining in the kiln without volatilization by the above reduction roasting method contains a large amount of reduced iron content, so it is collected from the kiln discharge end as a product called iron-containing clinker. iron raw materials for commercial use or discharged to landfill.

<Wet process>
Water-soluble impurities such as fluorine, chlorine, or cadmium contained in the crude zinc oxide dust are separated and extracted into the treatment liquid, and solid-liquid separation treatment is performed to remove the impurities from the crude zinc oxide dust by water washing. Wet processing to obtain a zinc oxide cake can be carried out by the following process steps.

The crude zinc oxide dust recovered from the steel dust by the reduction roasting step S20 is repulped with industrial water or the like. Collection can be performed with an electric dust collector or the like. The slurry of crude zinc oxide dust is subjected to pH adjustment and agglomeration treatment, and then dehydrated. By this washing and dehydration, the halogen content of the zinc oxide cake is preferably reduced to less than 0.6% by mass in terms of fluorine content and to less than 1.0% by mass in terms of chlorine content. Cadmium present as ions in the neutral region can also be removed. In a state in which impurities such as fluorine have been removed from the treatment liquid, the treatment liquid in which the impurities are distributed is removed from the crude zinc oxide dust by solid-liquid separation. This results in a slurry of crude zinc oxide dust resulting in a crude zinc oxide cake with a higher zinc content.

<Drying and heating process>
The content of residual impurities such as fluorine is further reduced by a dry heating step S40 in which the crude zinc oxide cake obtained in the wet step S30 is charged into a heating furnace such as a dry heating rotary kiln (DRK) and baked and granulated. In addition, it is possible to obtain high-grade zinc oxide ore.

Regarding the firing temperature of the dry heat treatment, the temperature inside the furnace should be maintained and managed so that the temperature of the material to be fired when discharged from the dry heat rotary kiln (DRK) is in the range of 1100 ° C to 1150 ° C. is preferred.

<Exhaust gas dust cleaning process>
As cleaning equipment for performing the exhaust gas dust cleaning step S50 for cleaning the exhaust gas dust generated in the drying and heating step S40 to obtain a cleaned exhaust gas dust cake, a combination of a cleaning tower and a wet electrostatic precipitator is common. . In addition, the exhaust gas dust cake after cleaning collected by these facilities is repeatedly circulated into a drying and heating rotary kiln (DRK) or the like that performs the drying and heating step S40, which is an upstream process, to effectively utilize metal resources. processing is taking place.

<Wastewater treatment process>
The wastewater treatment step S60 removes fluorine and cadmium from the wastewater containing high concentrations of fluorine and cadmium separated from the crude zinc oxide in the wet process S30, and further neutralizes heavy metals contained in trace amounts in the wastewater. It is a step of removing precipitates by means of water, and finally adjusting the pH to make harmless waste water.

<Zinc recovery rate measurement step>
In the present invention, a zinc recovery rate measurement step S70, which is a step in which the recovery rate of zinc in the reduction roasting step S20 is measured by, for example, the above-described method, is provided as a downstream process of the reduction roasting step S20. is preferred. The zinc recovery rate can be controlled with higher accuracy by measuring and confirming the zinc recovery rate at all times or at appropriate intervals in the zinc recovery rate measurement step S70.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. Moreover, the effects described in the embodiments of the present invention are merely enumerations of the most suitable effects resulting from the present invention, and the effects of the present invention are limited to those described in the examples of the present invention. is not.

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.

By implementing the production method of the present invention in which the "pellets for reduction roasting" having the unique composition of the present invention obtained in the preliminary mixing step are used in the reduction roasting step, the recovery rate of zinc in the reduction roasting step is significantly improved. In order to confirm that, the following tests were conducted.

Iron and steel dust was used as the raw material ore for producing the pellets of each example and comparative example. The composition of this steel dust is as follows.
Zn: 22% by mass, Pb: 0.6% by mass, Fe: 25% by mass, Cr: 0.4% by mass, F: 0.6% by mass, Cd: 0.05% by mass.

Recycled carbon was used as a carbonaceous reducing agent for producing pellets in each of Examples and Comparative Examples. The amount of the recycled carbon to be added was appropriately adjusted so that the carbon content was 8.0% as a ratio to the total amount of raw material ore.

Limestone having a particle size of 0.5 to 3 mm was used for producing pellets in each of Examples and Comparative Examples. The amount of limestone added was adjusted so that the limestone addition rate with respect to the total amount of raw material ore was the addition rate shown in Table 1 for each example and comparative example.

Then, the above raw ore, carbonaceous reducing agent, and limestone are mixed and granulated by Dow Pelletizer (registered trademark) manufactured by Shin Nichinan Co., Ltd., and each example having a particle size of 5.0 to 10.0 mm and comparative pellets were obtained.

Each of the above pellets was charged into a reduction roasting rotary kiln (RRK) having an inner diameter of 3 m and a length of 50 m to carry out a reduction roasting process. The roasting temperature of the reduction roasting rotary kiln (RRK) was in the range of 1050°C or higher and 1200°C or lower. The amount of limestone as described in Table 1 as the additional amount of limestone was added to each comparative example and example so that the total amount of limestone input was constant in the process of all comparative examples and examples, respectively. It was additionally charged into a roasting rotary kiln (RRK). Then, the recovery rate of zinc in the reduction roasting process was measured for each of the comparative examples and the examples in which pellets with different limestone addition rates were added. In addition, the zinc recovery rate is obtained by measuring the zinc content in the steel dust and the zinc content in the iron-containing clinker discharged from the reduction roasting rotary kiln (RRK) using a fluorescent X-ray analyzer. It was calculated from the analytical values obtained and the amounts of each material. The results were as shown in Table 1.

From Table 1, it can be seen that the recovery rate of zinc in the reduction roasting process is significantly improved by implementing the production method of the present invention in which the "pellets for reduction roasting" having a unique composition obtained in the preliminary mixing process are used in the reduction roasting process. confirmed to improve. It has also been confirmed that, according to the method for producing zinc oxide ore of the present invention, the recovery rate of zinc in the reduction roasting process can be improved by at least about 1.5%, and up to about 3% at the same roasting temperature as in the conventional method. rice field.

According to such a production method of the present invention, in the production of zinc oxide ore using iron and steel dust, the zinc recovery rate is set to 95% or more, so that the zinc grade of zinc oxide ore, which is the final product, is increased. , as a raw material for zinc smelting by the ISP smelting method or the like. Also, by reducing the content of zinc in the iron-containing clinker, which is a by-product, to 2.0% or less, it can be sold to steel manufacturers as a high-quality recycled product. From the above, the superiority of the present invention is recognized also from the viewpoint of promotion of resource recycling.

S10 Pre-mixing step S20 Reduction roasting step S30 Wet process S40 Drying heating step S50 Exhaust gas dust cleaning step S60 Waste water treatment step S70 Zinc recovery rate measurement step

Claims (5)

a pre-mixing step of mixing and granulating raw ore containing zinc oxide and additive materials to obtain pellets for reduction roasting;
a reduction roasting step for obtaining crude zinc oxide dust by subjecting the pellets for reduction roasting to a reduction roasting treatment,
wherein the additive material contains a carbonaceous reducing agent and limestone;
A method for producing zinc oxide ore. The method for producing zinc oxide ore according to claim 1, wherein the raw material ore is steel dust. The method for producing zinc oxide ore according to claim 1 or 2, wherein the content of limestone in the pellets for reduction roasting is 2.0 parts by weight or more and 10.0 parts by weight or less per 100 parts by weight of the raw material ore. . a wet process of subjecting the crude zinc oxide dust to a wet treatment to remove water-soluble impurities to obtain a crude zinc oxide cake;
The method for producing zinc oxide ore according to any one of claims 1 to 3, further comprising a dry heating step of subjecting the crude zinc oxide cake to a dry heat treatment. Pellets for reduction roasting to be introduced into the reduction roasting process as a raw material for zinc oxide ore,
A pellet containing a raw material ore containing zinc oxide, a carbonaceous reducing agent, and limestone.

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