JP7099299B2 - Manufacturing method of zinc oxide ore - Google Patents

Description

The present invention relates to a method for producing zinc oxide ore, which produces zinc oxide ore from steel dust as a raw material. More specifically, zinc oxide can stably maintain a high zinc recovery rate when zinc oxide ore is produced using steel dust, which is also a recycled product and usually has a certain degree of variation in its composition, as a raw material. Regarding the method of producing ore.

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 bullion in a zinc smelter. Crude zinc oxide dust, which is a raw material for zinc oxide ore, is a zinc-containing ore and can be obtained by subjecting steel dust generated from a blast furnace, an electric furnace, or the like in the steel industry to a reduction roasting treatment. This reduction roasting process of steel dust is generally performed by a reduction roasting process using a rotary kiln. When the reduction roasting process is performed by a rotary kiln, the steel dust as a raw material is put into the rotary kiln together with a carbonaceous reducing agent such as carbon and limestone which is a composition adjusting agent. (See Patent Document 1).

The maximum temperature inside the rotary kiln (hereinafter, also referred to as "reduction roasting rotary kiln (RRK)" in the present specification) to be reduced roasted is about 1050 to 1200 ° C. due to the combustion of the fuel heavy oil and the above-mentioned carbonaceous reducing agent. It is controlled. Steel dust is reduced and roasted in this reduction roasting rotary kiln (RRK), and the volatilized metallic zinc is reoxidized and solidified in the kiln, and then collected as particulate crude zinc oxide dust by an electrostatic collector or the like. To. The recovered crude zinc oxide dust is made into zinc oxide ore in which impurities are further separated by a subsequent wet process or a drying and heating process to improve the zinc grade to a necessary level, and is used as a raw material for zinc bullion. ..

Naturally, the zinc grade of the final product, zinc oxide ore, is 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 improve the zinc grade of zinc oxide ore to a value allowed in each smelting process.

Here, it is desirable to use steel dust as a raw material from the viewpoint of promoting resource recycling and cost reduction, but steel dust, which also has one aspect as industrial waste, is usually generated for each brand, that is, the source. The chemical composition and physical properties of each product differ greatly. Further, even if the sources are the same, it is inevitable that there will be some variation in the chemical composition and physical properties for each delivery unit, that is, for each lot. In a zinc oxide ore manufacturing plant that uses such steel dust as a raw material, a plurality of types of steel dust having different compositions that are carried in from moment to moment are used alone or in a mixed manner in the order of carrying in. There is.

For this reason, in a zinc oxide ore manufacturing plant that uses steel dust as a raw material, which is brought in from moment to moment, the zinc content and iron content of the raw material to be subjected to the reduction roasting process are switched between steel dust brands and lots. It is inevitable that the amount will fluctuate over time each time or every time the mixing ratio is changed, and in order to cope with this change, the amount of the carbonaceous reducing agent added to the reduction roasting step was adjusted as needed.

However, since the raw materials and the like charged in the rotary kiln that performs the reduction roasting process that is continuously operated proceed in the kiln over a certain residence time, the amount of the carbonaceous reducing agent added may be adjusted as needed. Even if adjusted, excess or deficiency of the carbonaceous reducing agent may occur in each part in 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-melt adheres to and grows on the inner wall of the kiln, forming a ring shape called beco. In some cases, the formation of ridges in the kiln caused poor discharge and deterioration of reactivity (hereinafter referred to as "beco" to refer to the formation of ring-shaped ridges called beco. be). Further, if the rotation speed of the rotary kiln is increased in order to suppress the sticking and growth of such a melt, in this case, the zinc recovery rate is lowered due to the decrease in the residence time of the raw material in the rotary kiln. The problem of zinc lnination has come to be recognized.

Oxidation that can prevent sticking and further stably improve the recovery rate of zinc in the reduction roasting process in a zinc oxide ore manufacturing plant that uses steel dust, which is also a recycled product and has variations in composition, as a raw material. There was a need for a method for producing zinc ore.

JP-A-2015-120948

INDUSTRIAL APPLICABILITY The present invention can prevent sticking and stably maintain the zinc recovery rate in the reduction roasting process at a desired height in a zinc oxide ore manufacturing plant using steel dust as a raw material. It is intended to provide a method for producing ore.

In the total process of producing zinc oxide ore, steel dust is preferably used as a raw material to be input to the reduction roasting step from the viewpoint of promoting recycling. When a plurality of types of steel dust having different compositions are used as raw materials to be charged in the reduction roasting process, the present inventors set the mixing ratio of the steel dust to zinc in the input raw material within a certain operation period. By adjusting the content ratio with iron so that it stays below the specified standard value, it is possible to prevent sticking and stably improve the zinc recovery rate in the reduction roasting process. The present invention was completed. More specifically, the present invention provides the following.

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

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

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

(4) Further, a wet step 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 step of subjecting the crude zinc oxide cake to a dry heat treatment are further performed. The method for producing zinc oxide ore according to any one of (1) to (3).

According to the present invention, in a zinc oxide ore manufacturing plant using steel dust as a raw material, it is possible to prevent sticking and stably maintain the zinc recovery rate in the reduction roasting step 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 zinc oxide ore of this invention.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

<Overall process>
The method for producing zinc oxide ore of the present invention is a compounding step S10 for obtaining a "compounding raw material for a reduction roasting process" having a composition peculiar to the present invention, and the "compounding material for a reduction roasting process" is subjected to reduction roasting and coarsely prepared. It is a manufacturing method including at least the reduction roasting step S20 for obtaining zinc oxide dust.

Further, as shown in FIG. 1, the method for producing zinc oxide ore of the present invention comprises crude zinc oxide dust obtained in the reduction roasting step S20 in addition to the above-mentioned compounding step S10 and reduction roasting step S20. Wet step S30 to obtain crude zinc oxide cake by separating and removing water-soluble impurities such as fluorine in the treatment liquid, and dry heating step S40 to dry and heat the crude zinc oxide cake obtained in the wet step S30 to obtain zinc oxide ore. The preferred embodiment thereof is the implementation as an overall process including the exhaust gas dust cleaning step S50 for cleaning the exhaust gas dust generated in the drying and heating step S40 to obtain the exhaust gas dust cake after cleaning, and the wastewater treatment step S60. The method. In the compounding step S10, the steel dust to be charged into the reduction roasting rotary kiln (RRK) is pelletized, and a reducing agent or the like is preliminarily added to further stabilize the zinc recovery rate in the reduction roasting step. It can also be improved.

The method for producing zinc oxide ore of the present invention is assumed to be carried out in a zinc oxide ore production plant in which a plurality of types of steel dust having different content ratios of zinc and iron are sequentially brought in as raw materials. It is a manufacturing method. Then, in more detail, the method for producing zinc oxide ore of the present invention actually includes each operating period from among a plurality of types of steel dust that are sequentially brought in at the zinc oxide ore manufacturing plant under the above conditions. It is a production method that can be suitably carried out in a production plant of zinc oxide ore used as a raw material by sequentially selecting a plurality of types of steel dust to be used in each case. It should be noted that, as a specific example of the embodiment of "selecting a plurality of types of steel dust sequentially and using them as raw materials" in "a situation where a plurality of types of steel dust are sequentially carried in", it is disclosed in the examples described later. The usage mode of the steel dust raw material in the test operation can be exemplified.

It should be noted that the above-mentioned carry-in status of steel dust is not a special situation in the production of zinc oxide ore using steel dust as a raw material, but is also a very general supply mode of raw materials. Therefore, in that sense, the manufacturing method of the present invention also has sufficient practicality and versatility.

In this production method, in the blending step S10, a plurality of types of steel dust having different content ratios of zinc and iron are mixed at a predetermined mixing ratio according to a unique control standard described in detail below. The first feature. As a result, the zinc recovery rate in the reduction roasting step S20 can be stably improved. Therefore, according to this production method, the zinc grade of zinc oxide ore, which is a raw material ore to be put into zinc smelting, can be stably maintained in a desirable high range.

<Mixing process>
The blending step S10 is a step of mixing steel dust at a predetermined mixing ratio to obtain a “blending raw material for a reduction roasting step”. More specifically, in this step, for example, as illustrated as a conceptual diagram in FIG. 1, the content ratios of zinc and iron are α, β, and γ, respectively, of three brands of steel dust. This is a step of mixing A to C according to a formulation plan determined based on the original operation control standard described in detail below.

In this step, it is preferable to further mix a carbon reducing agent such as recycled carbon in addition to steel dust, and it is more preferable to use each of these raw materials as a granulated pellet-shaped raw material. preferable. This mixed granulation work, so-called pelletizing, can be performed using a commonly used pelletizing device, and more specifically, a rotary pan type pelletizer or a biaxial non-constant velocity pin type granulation. It can be carried out by continuously supplying steel dust and recycled carbon so as to have a predetermined pellet composition using a machine, and mixing and granulating each of the above raw materials while adding mist-like water.

In the compounding process S10, the "variation" in each "standard operating period" specified in advance with respect to the "content ratio of zinc and iron in the compounding raw material for the reduction roasting process" for each unit operating period is a predetermined "variation". The mixing ratio of each steel dust for each "unit operating period" within the "standard operating period" is determined so as to be less than the "variation standard value".

As a specific example of the implementation of this manufacturing method, the standard operating period is January, the unit operating period is one day, and in the "mixing raw material for the reduction roasting process" which is a mixture of steel dust having different compositions. Regarding the "variation in the content ratio of zinc and iron", the "standard deviation σ" is managed as the "variation reference value", and the standard deviation σ is set to less than 0.3 for steel on each day. An example in which the mixing ratio of dust is determined in advance over the next month and the operation is performed can be given as an example of a preferable embodiment.

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

When the standard operating period is January and the unit operating period is one day, the standard deviation σ, which indicates the variation in the above “Zn / Fe ratio”, shall be calculated by the formula shown in the following [Equation 1]. Can be done. In this case as well, 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 recycled steel dust as a raw material, zinc in the "mixed raw material for the reduction roasting process", which is a mixture, is used in the entire process of mixing and using multiple raw materials that are sequentially brought in. It is actually impossible to completely eliminate the fluctuation of the content ratio (Zn content / Fe content) between iron and iron, considering the cost. However, as described above, the standard deviation σ is the monthly variation in the daily average value of the zinc-iron content ratio (Zn content / Fe content) in the “blending material for the reduction roasting process”. According to the method of control using the method, sticking is prevented while avoiding abrupt fluctuations in the above-mentioned content ratio (Zn content / Fe content), which has a significant effect on the zinc recovery rate. , The zinc recovery rate can be stably maintained at a desired height.

<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 "preparation raw material for the reduction roasting process" obtained in the preparation step S10 is continuously charged into the reduction roasting rotary kiln (RRK) together with the reducing agent, limestone and the like.

In the reduction roasting step S20, depending on the zinc content and the iron content in the above-mentioned "prepared raw material for the reduction roasting step", the zinc and carbon required for reducing the zinc and iron contained in the raw material are reduced. The required amount of the quality reducing agent is obtained, and the required amount of the carbonaceous reducing agent is added. In the production method of the present invention, since the sudden fluctuation of the above-mentioned content ratio (Zn content / Fe content) of the "blending material for the reducing roasting process" is avoided in advance, the brand of steel dust is switched. It is unlikely that there will be a discrepancy between the calculated required amount of reducing agent that occurs every time or every change in the mixing ratio and the actual progress of the reduction reaction in the kiln. Further, this can suppress the occurrence of a situation where the carbonaceous reducing agent is locally deficient.

More specifically, since the main components of steel dust are ZnO and Fe ₂ O ₃ , the Zn content and 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 will fluctuate significantly squared. By the way, the required amount of carbonaceous reducing agent required for reducing zinc and iron is obtained 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 → 2 FeO + 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 the carbonaceous reducing agent required for reducing iron is 1.5 times the required amount of the carbonaceous reducing agent required for reducing zinc. Will be. Therefore, when the Zn content / Fe content fluctuates greatly, the required amount of the carbonaceous reducing agent further fluctuates.

As described above, the amount of the carbonaceous reducing agent added is because the raw materials, etc. input in the rotary kiln that performs the reduction roasting process, which is continuously operated, proceed in the kiln over a certain residence time. Even if the above is adjusted at any time, excess or deficiency of the carbonaceous reducing agent may occur in each part in the rotary kiln. For example, even if the amount of carbonaceous reducing agent added is increased according to the raw material composition when switching the brand of steel dust or changing the mixing ratio, the CO gas generated in the rotary kiln remains small for a while. There is a local shortage of reducing agents. When the residence time of the rotary kiln is about 3 to 4 hours, the state continues for about 3 to 4 hours until the raw materials in the rotary kiln are replaced. When the carbonaceous reducing agent is locally deficient, iron, which should be reduced to metallic iron, forms a low melting point phase such as FeO, and the semi-melt adheres to and grows on the inner wall of the kiln, resulting in beco. May lead to poor discharge of stagnant material in the kiln and deterioration of reactivity.

When the rotation speed of the rotary kiln was increased in order to suppress the sticking and growth of the melt as described above, the zinc recovery rate was lowered due to the decrease in the residence time of the raw material in the rotary kiln. As described above, the fluctuation of the addition amount of the carbonaceous reducing agent destabilized the operation of the reduction roasting rotary kiln (RRK) and lowered the zinc recovery rate. According to the present invention, by controlling the variation of Zn content / Fe content to less than the standard value, the required amount of the carbonaceous reducing agent, that is, the fluctuation of the addition amount is suppressed, and this is used in the reduction roasting step. The zinc recovery rate can be stably improved.

In the furnace of this reduction roasting rotary kiln (RRK), the maximum temperature of the object to be treated is controlled in the range of about 1050 ° C. or higher and 1200 ° C. or lower by the combustion of heavy oil and the combustion of the charged carbonaceous reducing agent. The above-mentioned "blending material for the reduction roasting process" containing steel dust in the furnace 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), is captured, and is recovered as crude zinc oxide.

According to the production method of the present invention, high-grade crude zinc oxide can be obtained by stably increasing the recovery rate of zinc in the reduction roasting step S20. Specifically, the change over time in the content ratio of zinc and iron in the "blending material for the reduction roasting process" used in the reduction roasting step S20 has a specific range based on the above-mentioned control criteria peculiar to the present invention. By controlling the inside and appropriately adding the reducing agent as described above, for example, the monthly average zinc recovery rate in the above-mentioned reduction roasting step can be used as a guideline. It is possible to improve by about 0%. This makes it possible to efficiently produce, for example, high-grade zinc oxide ore, which can be preferably used for zinc smelting by an electrolytic refining method, at a lower cost than before. Further, since the zinc grade in the iron-containing clinker as a by-product can be lowered, stable production of high-quality iron-containing clinker is possible.

In the present specification, the "recovery rate of zinc in the reduction roasting process" is a reduction roasting rotary kiln (reduction roasting rotary kiln) with respect to the amount of zinc component contained in the "formulation raw material for the reduction roasting process" to be input to the reduction roasting process. It refers to the ratio of the amount of zinc component contained in the crude zinc oxide dust that has been volatilized and recovered in RRK). In addition, this "recovery rate of zinc in the reduction roasting process" is the zinc content in the steel dust as a raw material and the zinc content in the iron-containing clinker discharged from the reduction roasting rotary kiln (RRK), respectively. It can be measured by a fluorescent X-ray analyzer and calculated from the obtained analytical values, processing amount and output amount.

The reduction roasting residue remaining in the kiln without volatilization by the above reduction roasting method is recovered from the kiln discharge end as a product called iron-containing clinker and contains a large amount of reduced iron. Iron raw material for or is paid out for landfill.

<Wet process>
Wet treatment to obtain a crude zinc oxide cake by separating and extracting impurities such as fluorine contained in the crude zinc oxide dust into the treatment liquid and then removing the impurities from the crude zinc oxide dust by a water washing method by a solid-liquid separation treatment. Can be carried out 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 recovered by 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% by mass with respect to the fluorine content, and the chlorine content is preferably reduced to less than 1.0% by mass with respect to the chlorine content. In addition, cadmium existing as an ion in the neutral region can also be removed. In a state where impurities such as fluorine are removed in the treatment liquid, the treatment liquid to which the impurities are distributed is removed from the slurry by solid-liquid separation. As a result, the slurry of crude zinc oxide dust becomes a crude zinc oxide cake having a higher zinc content.

<Drying and heating process>
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 fired / granulated. By the dry heating step S40, the content of residual impurities such as fluorine is further reduced. At the same time, high-grade zinc oxide ore can be obtained.

Regarding the firing temperature of the drying heat treatment, the temperature inside the furnace is maintained and managed so that the temperature of the object to be fired when discharged from the drying heating rotary kiln (DRK) or the like is in the range of 1100 ° C. or higher and 1150 ° C. or lower. Is preferable.

<Exhaust gas dust cleaning process>
As a cleaning facility 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 exhaust gas dust cake after cleaning, a combination of a cleaning tower and a wet electrostatic precipitator is generally used. .. In addition, the exhaust gas dust cake after cleaning collected by these facilities is repeatedly circulated and charged into a dry heating rotary kiln (DRK) or the like that performs the dry heating step S40, which is an upstream process, in order to effectively utilize metal resources. Processing is being performed.

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

<Zinc recovery rate measurement process>
In the present invention, the zinc recovery rate measuring step S70, which is a step of measuring the zinc recovery rate in the reduction roasting step S20 by an equipment capable of measuring by, for example, the above-mentioned method, is provided as a downstream step of the reduction roasting step S20. Is preferable. By measuring and confirming the zinc recovery rate at all times or at appropriate intervals at any time by the zinc recovery rate measuring step S70, the zinc recovery rate can be controlled with higher accuracy.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. Further, the effects described in the embodiments of the present invention merely list the most suitable effects arising 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 compounding process, the "variation" in each "standard operating period" specified in advance for the "content ratio of zinc and iron in the compounding raw material for the reduction roasting process" becomes less than the predetermined "variation standard value". As described above, by implementing the production method of the present invention for determining the mixing ratio of each steel dust for each "unit operating period" within the "standard operating period", the zinc recovery rate in the reduction roasting step is significantly improved. The following tests were conducted to confirm that.

As a raw material for blending the "blending raw material for the reduction roasting process", 12 types of steel dust (steel dust A to L) having variations in composition within the following range were used.
Zn: 20-40% by mass, Pb: 0.5-3.0% by mass, Fe: 10-30% by mass, Cr: 0.1-1.0% by mass, F: 0.0-1.0% by mass %, Cd: 0.0 to 0.1% by mass.

First, as the test operation 1, 3 types of 8 types of steel dust, which are brought in from time to time in a quantity of about 500 tons per acceptance during one month, were selected and mixed. .. In the compounding, the combination of steel dust and the mixing ratio were adjusted so that the standard deviation of the daily average Zn / Fe ratio of the compounding raw material was 0.16 during one month. In selecting steel dust, in principle, three types were selected in the order in which they were delivered 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 tons per day. The "formulation change" for adjusting the combination of steel dust and the mixing ratio was performed 11 times in one month.

In test operation 1, in addition to the three types of steel dust, recycled carbon was mixed as a carbonaceous reducing agent and mixed and granulated with a Dow Pelletizer (registered trademark) manufactured by Shin-Nippon Minami Co., Ltd., and the particle size was 5. .0 to 10.0 mm carbonaceous reducing agent inner pellets were prepared. The amount of recycled carbon added to the total amount of steel dust in each compounded raw material was adjusted so that the carbon content was 8.0% by mass. Depending on the zinc content and iron content in the compounding raw material, the required amount of the carbonaceous reducing agent required for reducing zinc and iron can be obtained, but with respect to the required amount of the carbonic reducing agent. Since the amount of carbonaceous reducing agent contained in the carbonaceous reducing agent inner pellet having a carbon content of 8.0% by mass is adjusted to be small, powdered coke is used as the remaining insufficient carbonaceous reducing agent. It was directly put into the reduction roasting rotary kiln (RRK) together with the quality reducing agent inner pellets. The above-mentioned carbonaceous reducing agent inner pellets, powdered coke, limestone as a composition adjusting agent, and a repeating material were put into a reduction roasting rotary kiln (RRK) having an inner diameter of 3 m and a length of 50 m to carry out the reduction roasting step. The roasting temperature of the reduction roasting rotary kiln (RRK) was set in the range where the maximum temperature of the object to be treated was 1050 to 1200 ° C. in all test operations.

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

In each test operation, the monthly variation of the "daily average Zn / Fe ratio" in the compounding raw material for the reduction roasting process according to the following definition is controlled by the standard deviation σ, and the upper limit of the allowable range of the value is controlled. The "variation reference 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. In addition, a one-month steel dust preparation plan for each test operation so that the one-month variation in the "daily average Zn / Fe ratio" in each operation does not exceed the "variation standard value". It was determined.
Zn / Fe ratio = daily average zinc content in the compounding material (% by weight) ÷ average daily iron content in the compounding material (% by weight)

The standard deviation σ for one month of the "daily average Zn / Fe ratio" for each test operation (hereinafter, also simply referred to as "standard deviation σ of the Zn / Fe ratio") is the standard deviation σ of each steel dust (AL). Calculated from the Zn content and Fe content, the mixing ratio of the three types of steel dust for each compounding raw material amount, and the "formulation change" schedule, 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 carried out. The actual "standard deviation σ of the Zn / Fe ratio" in each test operation was as shown in Table 1 (in Table 1, it is simply indicated as "σ").

Regarding the values of the Zn content and Fe content of each steel dust used to calculate the above-mentioned "standard deviation σ of the" daily average Zn / Fe ratio "for each test operation" for one month, etc. Of the analytical values of each steel dust analyzed at the time of delivery, the latest value was used. On the day when the "formulation change" was carried out, the Zn content in the compounding raw material before and after the change was further weighted and averaged by the compounding time, and the daily average zinc content in the compounding raw material was obtained. And said. 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. For the zinc recovery rate, the zinc content in the steel dust described above and the zinc content in the iron-containing clinker discharged from the RRK were measured by a fluorescent X-ray analyzer, respectively, and the obtained analytical values and the treatment amount were obtained. And calculated from the output.

As the number of rotations of the kiln is reduced, the residence time in the kiln increases and the zinc recovery rate improves, but if the "standard deviation σ of the Zn / Fe ratio" increases, the furnace condition deteriorates when the formulation is changed. The sticking of the stagnant material in the kiln furnace progresses. In order to suppress this, in the test operation, an operation was performed to increase the kiln rotation speed. 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 the Zn / Fe ratio" was increased to 0.57, the retained material adhered and grew on the inner wall of the kiln regardless of the increase in the kiln rotation speed. Due to the formation of a ring-shaped dam, the operation was suspended due to poor 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 a predetermined value or less, the zinc recovery rate in actual operation can be significantly improved. I understand. It can also be seen that the zinc recovery rate can be 95% or more by controlling the operation by defining the "standard deviation σ of the Zn / Fe ratio" to be less than 0.3.

According to the production method of the present invention as described above, in the production of zinc oxide ore using steel dust having a large variation in chemical composition for each brand, the zinc recovery rate is 95% or more, which is the final product. It can be suitably used as a material for zinc smelting by an ISP smelting method or the like by enhancing the zinc grade of zinc oxide ore. In addition, the zinc content in the iron-containing clinker, which is a by-product, can be reduced to 2.0% or less, and the product can be sold to steel makers 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 Wastewater treatment process S70 Zinc recovery rate measurement process

Claims (4)

In a zinc oxide ore manufacturing plant where multiple types of steel dust having different content ratios of zinc and iron are sequentially carried in, zinc oxide ore is used as a raw material by sequentially selecting multiple types of steel dust from the steel dust. It is a manufacturing method of
A compounding process in which a plurality of types of the steel dust are mixed at a predetermined mixing ratio and used as a compounding raw material for a reduction roasting process.
It includes a reduction roasting step of adding a predetermined amount of a carbonaceous reducing agent to the compounding raw material for the reduction roasting step and performing a reduction roasting treatment to obtain crude zinc oxide dust.
In the compounding process, the variation in the content ratio of zinc and iron in the compounding raw material for the reduction roasting process for each unit operating period for each predetermined standard operating period is always less than the predetermined variation standard value. As described above, the mixing ratio of the steel dust for each unit operating period within the standard operating period is determined.
In the reduction roasting step, the carbonaceous reducing agent required for reducing the zinc and the iron is required according to the zinc content and the iron content in the compounding raw material for the reduction roasting step. A method for producing zinc oxide ore, wherein an amount is determined and a required amount of the carbonaceous reducing agent is added. The unit operating period is one day, and the content ratio of zinc and iron in the compounding raw material for the reduction roasting step is the daily average Zn / Fe ratio defined below.
The standard operating period is January, and the variation is the standard deviation of the Zn / Fe ratio.
The method for producing zinc oxide ore according to claim 1.
Zn / Fe ratio = daily average zinc content in the compounding material (% by weight) ÷ average daily iron content in the compounding material (% by weight) The method for producing zinc oxide ore according to claim 2, wherein the variation reference value is 0.3. A wet step 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.

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