JP2020097760A - Manufacturing method of zinc oxide ore - Google Patents

Abstract

To provide a manufacturing method of zinc oxide ore, which can maintain a recovery rate of zinc in a reduction roasting process at a stably desirable height in a manufacturing plant of zinc oxide ore into which a plurality of kinds of steel dusts having different content ratios of zinc and iron are sequentially carried-in.SOLUTION: A manufacturing method of zinc oxide ore includes: a preparation process S10 in which a plurality of kinds of steel dusts are mixed at a predetermined mixing ratio to form a preparation raw material for the reduction roasting process; and a reduction roasting process S20 of obtaining crude zinc oxide dust by applying the reduction roasting process by adding a predetermined amount of a carbonaceous reducing agent to the preparation raw material for the reduction roasting process, in which, in the preparation process S10, a mixing ratio of the steel dusts for every unit operation period in the standard operation period is determined such that a variation in every predetermined standard operation period of content ratios of zinc and iron in the preparation raw material for reduction roasting process for every unit operation period becomes less than a predetermined variation standard value.SELECTED DRAWING: Figure 1

Description

The present invention relates to a zinc oxide ore manufacturing method for manufacturing zinc oxide ore from iron and steel dust as a raw material. More specifically, it is also a recycled product, and zinc oxide that can stably maintain a high zinc recovery rate when producing zinc oxide ore using iron or steel dust as a raw material, the composition of which is somewhat variable. The present invention relates to a method for producing ore.

BACKGROUND ART Conventionally, zinc oxide ore obtained by separating and removing impurities from zinc-containing ores such as crude zinc oxide has been widely used as a raw material for zinc ingots in zinc smelters. The crude zinc oxide dust, which is a raw material of zinc oxide ore, is a zinc-containing ore and can be obtained, for example, by subjecting iron and steel dust generated from a blast furnace or an electric furnace in the steel industry to a reduction roasting treatment. This reduction roasting treatment of iron and steel dust is generally performed by a reduction roasting treatment using a rotary kiln. When performing reduction roasting treatment by a rotary kiln, iron and steel dust as a raw material is put into a rotary kiln together with a carbonaceous reducing agent such as carbon and limestone as a composition adjusting agent. (See Patent Document 1).

The maximum temperature of the rotary kiln (hereinafter also referred to as “reduction roasting rotary kiln (RRK)”) for performing the reduction roasting treatment is about 1050 to 1200° C. due to combustion of the fuel heavy oil and the carbonaceous reducing agent. Controlled. Steel dust is reduced and roasted in the reduction roasting rotary kiln (RRK), and volatilized metallic zinc is reoxidized in the kiln to be solidified, and then collected as particulate coarse zinc oxide dust by an electrostatic precipitator or the like. It Then, the recovered crude zinc oxide dust is made into zinc oxide ore in which impurities are further separated by the subsequent wet process and dry heating process to improve the zinc grade to a required degree, and is used as a raw material for zinc ingots. ..

The zinc quality of the final product, zinc oxide ore, is naturally required to be high. In order to use zinc oxide ore as a raw material for zinc smelting by the ISP smelting method or the like, it is necessary to increase the zinc grade of zinc oxide ore to a value allowed in each smelting process.

Here, although it is desirable to use steel dust as a raw material from the viewpoint of promoting resource recycling and cost reduction, steel dust that also has one aspect as industrial waste is usually produced by each brand, that is, the source of generation. Each time, the chemical composition and physical properties differ greatly. In addition, even if they are generated from the same source, it is inevitable that there is some degree of variation in chemical composition and physical properties for each loading unit, that is, for each lot. In a zinc oxide ore production plant using such iron and steel dust as a raw material, a plurality of types of iron and steel dust having different compositions, which are introduced every moment, individually in the order of introduction, or by appropriately mixing and using them. There is.

For this reason, in a zinc oxide ore manufacturing plant that uses the iron and steel dust that is being delivered every moment as a raw material, the zinc content and iron content of the raw material to be subjected to reduction roasting treatment can be changed between steel dust brands and lots. It is unavoidable that the amount of carbonaceous reducing agent changes with time or each time the mixing ratio is changed, and in order to cope with this variation, the amount of the carbonaceous reducing agent added to the reduction roasting step was adjusted at any time.

However, the amount of carbonaceous reducing agent added is changed at any time, because the raw materials, etc. introduced in the rotary kiln that performs the reduction roasting process that is continuously operating progresses in the kiln over a certain retention time. Even if it is adjusted, excess and deficiency of the carbonaceous reducing agent may occur in each part of the rotary kiln. Due to this, when the carbonaceous reducing agent is locally deficient, a low melting point phase such as FeO is formed, and the semi-molten material adheres and grows on the inner wall of the kiln, forming a ring shape called beco. The above-mentioned ridges may be generated, resulting in poor discharge of the accumulated matter in the kiln and deterioration of reactivity (hereinafter, referred to as “beco” with the generation of ring-shaped ridges referred to as “beco”). is there). Further, if the rotation speed of the rotary kiln is increased in order to suppress such sticking and growth of the melt, in this case, the retention time of the raw material in the rotary kiln is reduced and the recovery rate of zinc decreases. The problem of being lost has come to be recognized.

In a zinc oxide ore manufacturing plant that uses steel dust as a raw material, which is also a recycled product and has variations in composition, it is possible to prevent stickiness and further stabilize the recovery rate of zinc in the reduction roasting process. A method for manufacturing zinc ore has been sought.

JP, 2005-120948, A

INDUSTRIAL APPLICABILITY The present invention, in a zinc oxide ore manufacturing plant using steel dust as a raw material, prevents stickiness and can stably maintain the recovery rate of zinc in the reduction roasting step at a desired height. An object is to provide a method for producing ore.

In the total process for producing zinc oxide ore, steel dust is preferably used as a raw material to be added to the reduction roasting step from the viewpoint of promoting recycling. The present inventors, when using a plurality of types of steel dust of different composition, as a raw material to be fed to the reduction roasting step, the mixing ratio of those steel dust, zinc in the input raw material within a certain operating period and By adjusting so that the variation in the content ratio with iron is less than the predetermined standard value, it is possible to prevent sticking and to stably improve the recovery rate of zinc in the reduction roasting step. The present invention has been completed and the present invention has been completed. More specifically, the present invention provides the following.

(1) In a zinc oxide ore manufacturing plant into which a plurality of types of iron and steel dust having different content ratios of zinc and iron are sequentially loaded, a plurality of types of iron and steel dust are sequentially selected from the iron and steel dust and used as raw materials. A method for producing zinc oxide ore, which comprises mixing a plurality of types of the iron and steel dust at a predetermined mixing ratio to obtain a reducing roasting step compounding material, and a predetermined amount of the reducing roasting step compounding material. A reducing roasting step of obtaining a crude zinc oxide dust by adding a carbonaceous reducing agent and performing a reducing roasting treatment, wherein the blending step comprises blending for the reducing roasting step for each unit operation period. The variation in content ratio of zinc and iron in the raw material, the variation in each predetermined standard operating period, so that it is always less than a predetermined variation reference value, the steel for each unit operating period in the standard operating period The mixing ratio of dust is determined, and in the reducing roasting step, it is necessary to reduce the zinc and the iron according to the zinc content and the iron content in the raw material for the reducing roasting step. The method for producing a zinc oxide ore, comprising: determining the required amount of the carbonaceous reducing agent, and adding the required amount of the carbonaceous reducing agent.

(2) The unit operation period is one day, and the content ratio of zinc and iron in the blending raw material for the reduction roasting step is a daily average Zn/Fe ratio defined below. The method for producing zinc oxide ore according to (1), wherein the standard operation period is January, and the variation is a standard deviation of the Zn/Fe ratio.
Zn/Fe ratio=average daily zinc content (% by weight) in compounded raw material/average iron content (% by weight) in compounded raw material

(3) The method for producing zinc oxide ore according to (2), wherein the variation reference value is 0.3.

(4) 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, and a dry heating process of subjecting the crude zinc oxide cake to a dry heating treatment. The method for producing zinc oxide ore according to any one of (1) to (3), which comprises:

According to the present invention, in a zinc oxide ore manufacturing plant using steel dust as a raw material, stickiness can be prevented, and the recovery rate of zinc in the reduction roasting step can be stably maintained at a desired height. A method for producing zinc oxide ore can be provided.

It is a flowchart which shows an example of the manufacturing method of the zinc oxide ore of this invention.

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

<Overall process>
The zinc oxide ore manufacturing method of the present invention comprises a compounding step S10 for obtaining a “reducing roasting step compounding material” having a composition unique to the present invention, and a reduction roasting of this “reducing roasting step compounding raw material” And a reducing roasting step S20 for obtaining zinc oxide dust.

Moreover, as shown in FIG. 1, in addition to the above-described mixing step S10 and reduction roasting step S20, the method for producing zinc oxide ore of the present invention further uses crude zinc oxide dust obtained in the reduction roasting step S20. , A wet process S30 for obtaining a crude zinc oxide cake by separating and removing water-soluble impurities such as fluorine from the treatment liquid, and a drying and heating process S40 for drying and heating the crude zinc oxide cake obtained in the wet process S30 to obtain zinc oxide ore. Manufacturing as a preferred embodiment is an overall process including an exhaust gas dust cleaning step S50 for cleaning the exhaust gas dust generated in the drying and heating step S40 to obtain an exhaust gas dust cake after cleaning, and a wastewater treatment step S60. Is the way. In the blending step S10, the steel dust to be put into the reduction roasting rotary kiln (RRK) is pelletized, and further, a reducing agent or the like is preliminarily incorporated therein to further stabilize the zinc recovery rate in the reduction roasting step. It can also be improved.

The zinc oxide ore manufacturing method of the present invention is assumed to be carried out in a zinc oxide ore manufacturing plant under a situation where a plurality of types of steel dust having different content ratios of zinc and iron are sequentially loaded as raw materials. It is a manufacturing method. Then, the zinc oxide ore manufacturing method of the present invention, more specifically, in the zinc oxide ore manufacturing plant under the above-mentioned circumstances, from among the plurality of types of iron and steel dust that are sequentially carried in, each operating period is actually It is a manufacturing method that can be suitably carried out in a zinc oxide ore manufacturing plant used as a raw material by sequentially selecting a plurality of types of steel dust to be used for each. It should be noted that as a specific example of an aspect of “selecting a plurality of types of steel dust sequentially and using them as a raw material” under “a situation in which a plurality of types of steel dust are sequentially carried in” is disclosed in the examples described later. It is possible to exemplify the usage mode of the steel dust raw material in the test operation.

In addition, the above-mentioned situation of carrying in the iron and steel dust is not a special situation in the production of zinc oxide ore using the steel dust as a raw material, and is a very general manner of supplying the raw material. Therefore, in that sense, the production method of the present invention has sufficient practicality and versatility.

This manufacturing method comprises mixing a plurality of types of steel dust having different zinc and iron content ratios at a predetermined mixing ratio in accordance with a unique control standard described in detail below in the blending step S10. The first feature. Thereby, the recovery rate of zinc in the reduction roasting step S20 can be stably improved. Therefore, according to this manufacturing method, the zinc grade of the zinc oxide ore, which is the raw material ore to be added to the zinc smelting, can be stably maintained in a desired high range.

<Preparation process>
The mixing step S10 is a step of mixing steel dust at a predetermined mixing ratio to obtain a "mixing raw material for reduction roasting step". More specifically, in this step, for example, as illustrated in a conceptual diagram in FIG. 1, three types of steel dusts having zinc and iron content ratios of α, β, and γ, respectively. It is a step of mixing A to C in accordance with a blending plan determined based on an original operation management standard described in detail below.

In this step, it is preferable to further mix a carbonaceous reducing agent such as recycled carbon in addition to the iron and steel dust, and it is preferable to use each of these raw materials as a pelletized raw material. preferable. The operation of this mixed granulation, so-called pelletizing, can be performed by using a commonly used pelletizing device, and more specifically, a rotary pan pelletizer or a biaxial non-uniform speed pin granulator. Using a machine, iron and steel dust and recycled carbon are continuously supplied so as to have a predetermined pellet composition, and the above raw materials are mixed and granulated while adding mist-like water.

In the blending step S10, with respect to the "content ratio of zinc and iron in the blending raw material for the reducing roasting step" for each unit operation period, the "variation" in each "standard operation period" defined in advance is a predetermined "variance". The mixing ratio of each steel dust is determined for each "unit operation period" within the "standard operation period" so that it is less than the "variation standard value".

As a concrete example of the implementation of this manufacturing method, the standard operating period is one month, the unit operating period is one day, and it is a mixture of a plurality of iron and steel dusts having different compositions. "Standard deviation σ" is managed as "variation standard value" for the "variation of content ratio of zinc and iron", and the steel on each day is controlled so that the value of this standard deviation σ is less than 0.3. An example in which the mixing ratio of dust is determined in advance for the next one month and operation is performed can be given as an example of a preferred embodiment.

The "content ratio of zinc and iron in the compounding raw material for the reduction roasting step" is, when the unit operation period is one day, specifically, the average daily Zn/Fe defined below. Ratio. The unit operation period can be changed according to the operation form.
Zn/Fe ratio=average daily zinc content (% by weight) in compounded raw material/average iron content (% by weight) in compounded raw material

In addition, when the standard operating period is one month and the unit operating period is one day, the standard deviation σ showing the variation of the above “Zn/Fe ratio” should be calculated by the formula shown in [Equation 1] below. You can Also in this case, the standard operating period and the unit operating period can be changed according to the operating mode.

In the production of zinc oxide ore, which operates from steel dust, which is also a recycled product, in the entire process of mixing and using multiple raw materials that are sequentially loaded, the zinc in the “reduced roasting process blended raw material” that is a mixture It is impossible in reality to completely eliminate the fluctuation of the content ratio of Zn and iron (Zn content/Fe content) if cost is also taken into consideration. However, as described above, the monthly variation of the average daily value of the content ratio of Zn and iron (Zn content/Fe content) in the “reduced roasting process blended raw material” is calculated by standard deviation σ. According to the method of controlling by using, it is possible to prevent stickiness while avoiding the abrupt change of the above content ratio (Zn content/Fe content) that has a significant effect on the recovery rate of zinc. , The recovery rate of zinc can be stably maintained at a desired height.

<Reduction roasting process>
As a specific method of performing the reduction roasting step S20, a reduction roasting method using a reduction roasting rotary kiln (RRK) is generally adopted. In the reducing roasting step S20, the “reducing roasting step blending raw material” obtained in the blending step S10 is continuously charged into a reducing roasting rotary kiln (RRK) together with a reducing agent and limestone.

In the reducing roasting step S20, carbon required for reducing zinc and iron contained in the above-mentioned "reducing roasting step compounding raw material" in accordance with the zinc content and the iron content. Determine the required amount of carbonaceous reducing agent and add the required amount of carbonaceous reducing agent. In the production method of the present invention, a rapid change in the above content ratio (Zn content/Fe content) of the “mixing raw material for reduction roasting step” is avoided in advance, so that the brand of steel dust is switched. It is unlikely that there is a discrepancy between the calculated required amount of the reducing agent that occurs each time the mixing ratio is changed and the actual progress of the reduction reaction in the kiln. Further, this makes it possible to suppress the occurrence of a situation where the carbonaceous reducing agent is locally insufficient.

More specifically, since the main components of steel dust are ZnO and Fe ₂ O ₃ , the Zn content and the Fe content often change in inverse proportion depending on the brand. That is, if the Zn content decreases, the Fe content increases, and conversely, if the Zn content increases, the Fe content decreases. Therefore, if nothing is controlled, the Zn content/Fe content fluctuates greatly in the square. By the way, the required amount of carbonaceous reducing agent required to reduce zinc and iron is determined based on stoichiometry. In the reduction roasting step, the following reactions are carried out.
C+O ₂ →CO ₂
C+CO ₂ → 2CO
ZnO+CO→Zn(g)+CO ₂
Fe ₂ O ₃ +CO→2FeO+CO ₂
FeO+CO→Fe+CO ₂
g: represents a gas.
That is, if the number of moles is the same, the required amount of carbonaceous reducing agent required to reduce iron is 1.5 times the required amount of carbonaceous reducing agent required to reduce zinc. Becomes Therefore, if the Zn content/Fe content varies greatly, the required amount of carbonaceous reducing agent also varies significantly.

As mentioned above, the amount of carbonaceous reducing agent added is limited because the raw materials, etc. introduced in the rotary kiln that carries out the reduction roasting process, which operates continuously, progresses in the kiln over a certain retention time. Even if it is adjusted at any time, excess or deficiency of the carbonaceous reducing agent may occur in each part of the rotary kiln. For example, when changing the brand of iron and steel dust or changing the mixing ratio, even if the amount of carbonaceous reducing agent added is increased according to the raw material composition, the CO gas generated in the rotary kiln remains low for a while. There is a local shortage of reducing agent. When the residence time of the rotary kiln is about 3 to 4 hours, that state continues for about 3 to 4 hours until the raw material in the rotary kiln is replaced. When the carbonaceous reducing agent is locally insufficient, iron, which should be reduced to metallic iron originally, forms a low melting point phase such as FeO, and the semi-molten material adheres and grows on the inner wall of the kiln. In some cases, resulting in poor discharge of the residue in the kiln and deterioration of reactivity.

When the number of rotations of the rotary kiln is increased in order to suppress the sticking and growth of the melt as described above, the retention time of the raw material in the rotary kiln is reduced and the zinc recovery rate is reduced. As described above, the fluctuation of the addition amount of the carbonaceous reducing agent made the operation of the reduction roasting rotary kiln (RRK) unstable and reduced the recovery rate of zinc. According to the present invention, by controlling the variation of Zn content/Fe content to be less than the reference value, the required amount of carbonaceous reducing agent, that is, the variation of the addition amount, is suppressed, and thus, in the reduction roasting step. It is possible to stably improve the recovery rate of zinc.

In the furnace of the reduction roasting rotary kiln (RRK), the maximum temperature of the object to be treated is controlled to be in the range of 1050°C or more and 1200°C or less by the combustion of heavy oil and the combustion of the carbonaceous reducing agent charged. In the furnace, the above-mentioned "compounding raw material for reduction roasting process" containing iron and steel dust is reduced and roasted, and the volatilized metallic zinc is reoxidized in the furnace to become powdery zinc oxide. The powdery zinc oxide is introduced into the dust collector together with the exhaust gas from the reduction roasting rotary kiln (RRK), and is captured and recovered as crude zinc oxide.

According to the production method of the present invention, high-quality crude zinc oxide can be obtained by stably increasing the zinc recovery rate in the reduction roasting step S20. Specifically, the change over time of the content ratio of zinc and iron in the "reducing roasting step compounding raw material" used in the reducing roasting step S20 is within a specific range based on the above-mentioned control criteria specific to the present invention. Since the reducing agent is controlled within the above range and the reducing agent is appropriately added as described above, for example, the one month average zinc recovery rate in the above reduction roasting step is used as a guideline. It is possible to improve it by about 0%. As a result, for example, it becomes possible to efficiently produce a high-grade zinc oxide ore that can be preferably used for zinc smelting by the electrolytic smelting method at a lower cost than before. Further, since the grade of zinc in the iron-containing clinker, which is a by-product, can be reduced, stable production of high-quality iron-containing clinker becomes possible.

In the present specification, the “recovery rate of zinc in the reduction roasting step” means the reduction roasting rotary kiln (with respect to the amount of zinc component contained in the “reducing roasting step compounding material” to be added to the reduction roasting step ( RRK) refers to the ratio of the amount of zinc component contained in the crude zinc oxide dust that is volatilized and recovered. Further, the "recovery rate of zinc in the reduction roasting step" is defined as the zinc content in the raw material steel dust and the zinc content in the iron-containing clinker discharged from the reduction roasting rotary kiln (RRK), respectively. It can be calculated from the analytical value, the amount of treatment, and the amount of output obtained by measuring with a fluorescent X-ray analyzer.

The reducing roasting residue remaining in the kiln without being volatilized by the above reducing roasting method is recovered from the kiln discharge end as a product called iron-containing clinker, and contains a large amount of reduced iron content. It is paid out for iron raw materials for land use or for landfill.

<Wet process>
Wet treatment to separate and extract impurities such as fluorine contained in the crude zinc oxide dust into the treatment liquid, and further to remove the impurities from the crude zinc oxide dust by a water washing method by solid-liquid separation treatment to obtain a crude zinc oxide cake. Can be performed by the following processing steps.

The crude zinc oxide dust recovered from the steel dust in the reduction roasting step S20 is repulped with industrial water or the like. The crude zinc oxide dust can be collected with an electrostatic precipitator or the like. The crude zinc oxide dust that has become a slurry is subjected to pH adjustment and aggregation treatment, and then dehydrated. By this washing and dehydration, the halogen content of the crude zinc oxide cake is preferably reduced to less than 0.6 mass% for the fluorine content and less than 1.0 mass% for the chlorine content. Also, cadmium existing as ions in the neutral region can be removed. When impurities such as fluorine are removed from the treatment liquid, the treatment liquid in which the impurities are distributed is removed from the slurry by solid-liquid separation. Thereby, the slurry of the crude zinc oxide dust becomes a crude zinc oxide cake having a higher zinc content.

<Dry heating process>
The crude zinc oxide cake obtained in the wet process S30 is charged into a heating furnace such as a dry heating rotary kiln (DRK) and fired/granulated. The dry heating process S40 further reduces the content of residual impurities such as fluorine. At the same time, a high-quality zinc oxide ore can be obtained.

Regarding the firing temperature of the dry heating treatment, the temperature inside the furnace is maintained and controlled so that the temperature of the fired product when discharged from the dry heating rotary kiln (DRK) or the like is in the range of 1100°C or higher and 1150°C or lower. It is preferable.

<Exhaust gas dust cleaning process>
As the 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 the cleaned exhaust gas dust cake, a combination of a cleaning tower and a wet electrostatic precipitator is generally used. .. In addition, the exhaust gas dust cake collected by these facilities after cleaning is repeatedly circulated into the dry heating rotary kiln (DRK) for performing the dry heating step S40, which is an upstream step, so as to effectively utilize metal resources. Processing is taking place.

<Wastewater treatment process>
The wastewater treatment step S60 removes fluorine and cadmium from the waste liquid containing a high concentration of fluorine and cadmium separated from the crude zinc oxide dust in the wet step S30, and further neutralizes a trace amount of heavy metals contained in the waste liquid. In this process, the precipitate is removed by treatment, and the pH is finally adjusted to produce harmless wastewater.

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

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. In addition, the effects described in the embodiments of the present invention are merely listed as the most preferable effects resulting from the present invention, and the effects according to the present invention are limited to those described in the examples of the present invention. is not.

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.

In the blending process, the "variation" for each "standard operating period" of the "content ratio of zinc and iron in the blending raw material for the reduction roasting process" becomes less than the predetermined "variance reference value". Thus, the implementation of the manufacturing method of the present invention that determines the mixing ratio of each steel dust for each "unit operation period" within the "standard operation period" significantly improves the zinc recovery rate in the reduction roasting step. The following tests were conducted to confirm this.

As raw materials for preparing the "reduced roasting step preparation raw material", 12 types of steel dusts (steel dusts A to L) having different compositions in the following ranges were used.
Zn: 20-40 mass%, Pb: 0.5-3.0 mass%, Fe: 10-30 mass%, Cr: 0.1-1.0 mass%, F: 0.0-1.0 mass%. %, Cd: 0.0 to 0.1 mass %.

First, as the test operation 1, three kinds were selected from eight kinds of steel dust of 8 kinds of brands which are carried in momentarily at a quantity of about 500 tons per acceptance during one month, and blended. .. In the blending, the combination of the steel dust and the mixing ratio were adjusted so that the standard deviation of the Zn/Fe ratio of the daily average of the blended raw materials was 0.16 in one month. When selecting the iron and steel dust, three types were selected in the order in which they were delivered in principle so that the treatment would be completed within about one month after the delivery. The total amount of the three types of steel dust is 240 to 310 t per day. The “mixing change” for adjusting the combination of the steel dust and the mixing ratio was performed 11 times in one month.

In the test operation 1, in addition to three types of steel dust, recycled carbon was mixed as a carbonaceous reducing agent, and mixed granulation was carried out by Dow Pelletizer (registered trademark) manufactured by Shin-Nichinan Co., Ltd. A carbonaceous reducing agent-containing pellet having a size of 0 to 10.0 mm was produced. The amount of recycled carbon added to each of the mixed raw materials was adjusted so that the carbon content was 8.0% by mass. The required amount of the carbonaceous reducing agent required to reduce zinc and iron is determined according to the zinc content and the iron content in the prepared raw material. Since the amount of carbonaceous reducing agent contained in the carbonaceous reducing agent-containing pellets having a carbon content of 8.0% by mass is adjusted to be small, powder coke is used as the remaining insufficient carbonaceous reducing agent. It was directly put into a reducing roasting rotary kiln (RRK) together with the reducing agent-containing pellets. The above-mentioned pellet containing carbonaceous reducing agent, powder coke, limestone as a composition adjusting agent, and a repeated product were put into a reducing roasting rotary kiln (RRK) having an inner diameter of 3 m and a length of 50 m to carry out a reducing roasting step. Regarding the roasting temperature of the reduction roasting rotary kiln (RRK), the maximum temperature of the object to be treated was in the range of 1050 to 1200° C. in all test operations.

Next, as test operations 2 to 5, a test was carried out in which the standard deviation of the daily average Zn/Fe ratio of the prepared raw materials was changed to adjust the combination of iron and steel dust and the mixing ratio during one month. As a result, the brand of iron and steel dust used among all 12 types, the total amount of 3 types of iron and steel dust per day, and the number of "mixing changes" performed in one month were slightly different, but the method and The conditions were the same as in the test operation 1 and the test operations 2 to 5 were performed.

In each test operation, the monthly deviation of the "daily average Zn/Fe ratio" in the raw materials for reduction roasting process defined below was controlled by the standard deviation σ, and the upper limit of the allowable range of the value was controlled. The "variation standard value", which is also a value, was set to a different value in the range of 0.1 to 0.6 for each test operation. Moreover, in order to prevent the monthly variation of the "average daily Zn/Fe ratio" in each operation from exceeding the "variation standard value", a mixing plan of steel dust for one month for each test operation. It was determined.
Zn/Fe ratio=average daily zinc content (% by weight) in compounded raw material/average iron content (% by weight) in compounded raw material

The standard deviation σ of the “daily average Zn/Fe ratio” for each test operation during one month (hereinafter, also simply referred to as “standard deviation σ of Zn/Fe ratio”) is calculated for each steel dust (A to L). Calculated from the Zn content rate, the Fe content rate, the mixing ratio of three types of iron and steel dust for each blending raw material amount, and the schedule of "blending change", and this value is the "variation standard value" specified in advance for each test operation. The formulation was planned to be less than, and the formulation process was performed. The actual “standard deviation σ of Zn/Fe ratio” in each test operation was as shown in Table 1 (in Table 1, simply referred to as “σ”).

The values of the Zn content and the Fe content of each iron and steel dust used to calculate the above-mentioned "standard deviation σ for one month of "daily average Zn/Fe ratio" for each test operation" and the like are as follows. Among the analysis values of each steel dust analyzed at the time of delivery, the latest value was used. In addition, regarding the day when "modification change" was carried out, the Zn content ratio in the preparation raw material before and after the change was further weighted averaged by the preparation time, and the value of the daily average zinc content in the preparation raw material was calculated. And The same applies to the Fe content.

Then, the recovery rate of zinc in the reduction roasting step was measured and compared for each test operation. The results are as shown in Table 1. The recovery rate of zinc was determined by measuring the zinc content in the above-mentioned steel dust and the zinc content in the iron-containing clinker discharged from RRK by a fluorescent X-ray analyzer, and the obtained analysis value and treatment amount. And calculated from the output.

As the rotation speed of the kiln decreases, the residence time in the kiln increases and the recovery rate of zinc improves. However, if the “standard deviation σ of the Zn/Fe ratio” increases, the furnace conditions deteriorate when the composition is changed. Accumulation of accumulated substances in the kiln furnace progresses. In order to suppress this, in the test operation, an operation of increasing the kiln rotation speed was performed. As a result, the residence time in the kiln decreased and the zinc recovery rate decreased. Further, in the test operation 5 in which the “standard deviation σ of Zn/Fe ratio” was increased to 0.57, the accumulated matter adhered and grew on the inner wall of the kiln regardless of the increase of the kiln rotation speed. As a ring-shaped dam was formed, the operation was stopped due to defective discharge of residue in the kiln.

From Table 1, in the production method of the present invention, by controlling the “standard deviation σ of the Zn/Fe ratio” to be a predetermined value or less, it is possible to significantly improve the zinc recovery rate in actual operation. I understand. It is also understood that the zinc recovery rate can be 95% or more by controlling the operation by defining the “standard deviation σ of Zn/Fe ratio” to be less than 0.3.

According to such a production method of the present invention, in the production of zinc oxide ore using iron and steel dust having a large variation in chemical composition for each brand, the final product is obtained by setting the zinc recovery rate to 95% or more. It can be preferably used as a material for zinc smelting by the ISP smelting method or the like by improving the zinc grade of zinc oxide ore. Further, the zinc content in the iron-containing clinker, which is a by-product, can be 2.0% or less, and the product can be sold to a steel manufacturer as a high-quality recycled product. From the above, the present invention greatly contributes to the development of industry from the viewpoint of promoting resource recycling.

S10 Mixing process S20 Reduction roasting process S30 Wet process S40 Drying and heating process S50 Exhaust gas dust cleaning process S60 Waste water treatment process S70 Zinc recovery rate measuring process

Claims (4)

In a zinc oxide ore manufacturing plant in which a plurality of types of iron and steel dust having different content ratios of zinc and iron are sequentially loaded, a plurality of types of iron and steel dust are sequentially selected from the iron and steel dust and used as a raw material. The manufacturing method of
A mixing step of mixing a plurality of kinds of the steel dust at a predetermined mixing ratio to prepare a reducing raw material for the roasting step,
A reducing roasting step of obtaining a crude zinc oxide dust by adding a predetermined amount of carbonaceous reducing agent to the raw material for the reducing roasting step and performing a reducing roasting treatment,
In the blending step, the variation in the content ratio of zinc and iron in the blending raw material for the reducing roasting step for each unit operation period, in each predetermined standard operation period, is always less than a predetermined variation reference value. So as to determine the mixing ratio of the steel dust for each unit operation period within the standard operation period,
In the reduction roasting step, the carbonaceous reducing agent necessary for reducing the zinc and the iron is required according to the zinc content and the iron content in the raw material for the reduction roasting step. A method for producing a zinc oxide ore, the amount of which is determined, and the required amount of the carbonaceous reducing agent is added. The unit operation period is one day, the content ratio of zinc and iron in the reducing roasting step preparation raw material is a daily average Zn/Fe ratio defined below,
The standard operating period is one month, and the variation is a standard deviation of the Zn/Fe ratio,
The method for producing the zinc oxide ore according to claim 1.
Zn/Fe ratio=average daily zinc content (% by weight) in compounded raw material/average iron content (% by weight) in compounded raw material The method for producing zinc oxide ore according to claim 2, wherein the variation reference value is 0.3. 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 performing a dry heat treatment on the crude zinc oxide cake.

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