JP2021123778A - Method of manufacturing zinc oxide ore - Google Patents

Abstract

To provide a method of manufacturing zinc oxide ore capable of retaining a chlorine grade in a crude zinc oxide cake low by heightening a chlorine removal rate while suppressing usage of sodium carbonate in a wet process.SOLUTION: A method of manufacturing a zinc oxide ore includes: performing a chlorine amount-estimating process of estimating a content of a sodium aqueous solution-soluble chlorine of a crude zinc oxide cake raw material at any step before performing a wet process 20 in a production process of a zinc oxide ore including a reduction calcination process S10, a wet process S20, and a heating dry process S30; and performing a pH-adjusting process of adjusting a pH of a sodium carbonate aqueous solution to a pH corresponding to a content of the sodium aqueous solution-soluble chlorine of the crude zinc oxide cake raw material in a wet process S20.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing zinc oxide ore. More specifically, the present invention relates to a method for producing zinc oxide ore, which can remove chlorine contained in a raw material ore in a zinc oxide ore production process at a lower cost and with a sufficiently high removal 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 bullion in a zinc smelter.

Steel dust generated in the steel manufacturing process contains a relatively large amount of zinc in addition to the iron component. Therefore, steel dust is used as the above-mentioned zinc-containing ore, and zinc contained therein is widely recovered as crude zinc oxide dust to produce zinc oxide ore.

As an example of a typical method for obtaining crude zinc oxide dust by separating iron and zinc in steel dust, a reduction roasting method using a rotary kiln (so-called Waelz method) can be mentioned. When this method is used, zinc in the steel dust is reduced in the kiln furnace and volatilized as metallic zinc. When the metallic zinc separated on the gas side as a gas is cooled to 1000 ° C or lower, it quickly reacts with the surrounding oxygen to become zinc oxide and solidifies. It is collected from the exhaust gas by an electrostatic collector or the like.

The crude zinc oxide dust obtained in the reduction roasting step contains a part of halogens such as fluorine and chlorine contained in steel dust as impurities. As a treatment for separating and removing halogen from the crude zinc oxide dust, there is a method of alkaline cleaning the crude zinc oxide dust (see Patent Documents 1 and 2). The crude zinc oxide dust is usually put into a wet step of performing the above cleaning to remove the halogen component. At this time, in many cases, the secondary raw material containing zinc and chlorine is also put into this wet process together with the above-mentioned crude zinc oxide dust.

Here, among the halogen components contained in the above crude zinc oxide dust and the secondary raw material, about 80% or more of chlorine is removed in the wet process in order to finally satisfy the product standard value of zinc oxide burnt ore. It is required to remove at a rate. By increasing the amount of chemicals such as soda ash (sodium carbonate) used for alkaline cleaning in the wet process, the chlorine removal rate can be increased to about 90%. However, on the other hand, in order to reduce the production cost of zinc oxide ore, it has been required to suppress the excessive use of sodium carbonate while maintaining the required chlorine removal rate.

JP-A-2002-332259 Japanese Unexamined Patent Publication No. 2016-145423

According to the present invention, it is possible to sufficiently increase the removal rate of chlorine in the wet process while suppressing the excessive use of sodium carbonate, and maintain the chlorine quality in the crude zinc oxide cake obtained from the process at an appropriate low quality. It is an object of the present invention to provide a method for producing zinc oxide ore which can be produced.

When the present inventors conducted an elution test with water and an aqueous sodium carbonate solution on various raw materials to be put into the wet process, a chlorine compound in which most of the chlorine contained in the raw materials was dissolved only in water (the present invention). A raw material that is referred to as a "water-soluble chlorine compound" in the specification) and a chlorine compound in which most of the contained chlorine is soluble in an aqueous sodium carbonate solution but not in water alone (in the present specification, "soluble in an aqueous sodium solution"). It was found that it can be roughly divided into two types: the raw material, which is called "chlorine compound"). Based on this new finding, the present inventors pay attention only to the content of "sodium aqueous solution-soluble chlorine" in the raw materials to be put into the wet process, and perform the wet process with respect to this content. We have found that the above problems can be solved by optimizing the pH of the aqueous sodium solution, and have completed the present invention. In the present specification, the "sodium aqueous solution-soluble chlorine" is chlorine contained in the above-mentioned "sodium aqueous solution-soluble chlorine compound", and most of the chlorine is soluble in the sodium carbonate aqueous solution, but is not. Chlorine that is water-soluble and insoluble in water alone. Specifically, the present invention provides the following.

(1) A reduction roasting step of reducing and roasting a primary raw material which is an iron-containing crude zinc oxide raw material containing chlorine and iron to obtain crude zinc oxide dust, and the crude zinc oxide dust and iron containing chlorine. A wet step of obtaining a crude zinc oxide cake by repulping the crude zinc oxide cake raw material, which comprises a secondary raw material which is a non-iron-containing crude zinc oxide raw material, with an aqueous sodium carbonate solution and then dehydrating the crude zinc oxide cake, and the crude In the process of producing zinc oxide ore, which includes a drying and heating step of baking a zinc oxide cake to obtain zinc oxide ore, at any stage before the wet step, the sodium aqueous solution of the crude zinc oxide cake raw material is used. A chlorine amount estimation process for estimating the content of soluble chlorine is performed, and in the wet step, the pH of the sodium carbonate aqueous solution is adjusted to a pH corresponding to the content of the sodium aqueous solution soluble chlorine of the crude zinc oxide cake raw material. A method for producing zinc oxide ore to be treated.

(2) The amount of chlorine is estimated by regarding the primary raw material as steel dust and the content of the sodium aqueous solution-soluble chlorine contained in the secondary raw material as the content of the sodium aqueous solution-soluble chlorine of the crude zinc oxide cake raw material. The method for producing zinc oxide ore according to (1), wherein the treatment is carried out.

(3) The secondary raw material is a mixture of a plurality of types of the non-iron-containing crude zinc oxide raw materials, and the pH adjustment treatment is carried out with the sodium aqueous solution-soluble chlorine content contained in the individual non-iron-containing crude zinc oxide raw materials. The method for producing zinc oxide ore according to (2), which is carried out by adjusting the pH of the sodium carbonate aqueous solution according to the amount of each non-iron-containing crude zinc oxide raw material used.

(4) The method for producing zinc oxide ore according to any one of (1) to (3), wherein the pH of the aqueous sodium carbonate solution after the pH adjustment treatment is 6.0 or more and 6.5 or less.

According to the present invention, it is possible to provide a method for producing zinc oxide ore, which can appropriately maintain a low chlorine grade in a crude zinc oxide cake obtained from a wet process while suppressing excessive use of sodium carbonate. ..

It is a flowchart which shows an example of the manufacturing method of zinc oxide ore of this invention. It is a schematic diagram which shows the basic structure of the wet processing equipment which performs the wet process which is one process of the manufacturing method of zinc oxide ore of this invention. It is a graph which shows the result of stratifying the relationship between the pH of the sedimentation separation apparatus which performs a wet process, and the chlorine grade of a crude zinc oxide cake by the chlorine load from a secondary raw material. It is a figure which shows an example of the multidimensional matrix table used for performing the pH adjustment treatment in the wet process of the manufacturing method of zinc oxide ore of this invention.

<Overall process>
FIG. 1 is a flowchart of the method for producing zinc oxide ore of the present invention. The method for producing zinc oxide ore of the present invention includes a reduction roasting step S10 for obtaining crude zinc oxide dust by reducing and roasting a primary raw material such as steel dust, a crude zinc oxide dust obtained in the reduction roasting step S10, and two. The crude zinc oxide cake obtained in the wet step S20 and the wet step S20 obtained by separating and removing halogen elements such as fluorine and chlorine from the next raw material in the treatment liquid to obtain a crude zinc oxide cake is dried and heated to obtain zinc oxide ore. The obtaining drying and heating step S30 is an essential step.

Here, in the present specification, it is a raw material containing zinc and is a raw material to be input to the reduction roasting step S10, which is a step upstream of the wet step S20 in the entire process of zinc oxide ore production. Is referred to as "primary raw material". Further, in the present specification, in the entire process of zinc oxide ore production, the raw material ore containing zinc that is directly input to the wet step S20 without going through the upstream process is referred to as "secondary raw material". And.

The method for producing zinc oxide ore of the present invention uses a "iron-containing crude zinc oxide raw material" which is a raw material containing chlorine and iron in addition to zinc as the "primary raw material" to be input to the reduction roasting step S10. This is a process that can be widely applied to the production of zinc oxide using a "non-iron-containing crude zinc oxide raw material" that contains chlorine in addition to zinc as a "secondary raw material" and does not contain iron. Then, when the production method of the present invention is carried out, the crude zinc oxide dust obtained from the primary raw material and the secondary raw material are put into the wet step S20 together.

The chlorine content of the above-mentioned "iron-containing crude zinc oxide raw material" used as the primary raw material and the "non-iron-containing crude zinc oxide raw material" used as the secondary raw material is preferably 1% by weight or more. Further, the iron content of the above-mentioned "iron-containing crude zinc oxide raw material" is preferably 7% by weight or more. The "iron-containing crude zinc oxide raw material" is more preferably steel dust. The method for producing zinc oxide ore of the present invention can be particularly preferably applied to a process carried out using each raw material having a composition range as described above.

Further, in the overall process of zinc oxide production to which the method for producing zinc oxide of the present invention can be preferably applied, in addition to the above steps, the exhaust gas dust generated in the drying and heating step S30 is washed and washed. An exhaust gas treatment step for obtaining an exhaust gas dust cake, a wastewater treatment step for detoxifying the discharge liquid discharged from the wet step S20, and the like are performed together as an overall process. These steps may be appropriately performed in a conventionally known manner.

Then, in the method for producing zinc oxide ore of the present invention, among the above steps, the pH of the sodium carbonate aqueous solution used in the wet step S20 corresponds to the content of "sodium aqueous solution-soluble chlorine" as the raw material for the crude zinc oxide cake. The main feature of this production method is that a pH adjustment process is performed to obtain a pH to be adjusted.

<Reduction roasting process>
As a specific method for performing the reduction roasting step S10 for obtaining crude zinc oxide dust from a primary raw material such as steel dust, a reduction roasting method using a reduction roasting rotary kiln (RRK) can be used. When steel dust is used as the primary raw material and it is reduced and roasted by a reduction roasting rotary kiln, the steel dust is preliminarily mixed and granulated with a carbonaceous reducing agent such as coal or coke, and has a size of 5 It is molded into pellets of about 10 mm. Then, these pellets, steel dust that has not been mixed and granulated, a carbonaceous reducing agent such as coal and coke, and limestone (CaCO ₃ ) as a melting point adjusting agent are continuously added to the reduction roasting rotary kiln. It is thrown in.

When the reduction roasting step S10 is carried out, the inside of the reduction roasting rotary kiln is controlled so that the maximum temperature of the object to be processed is about 1,100 to 1200 ° C. by the combustion of heavy oil and the combustion of the charged carbonaceous reducing agent. ing. Steel dust is reduced and roasted in this furnace, and when the volatilized metallic zinc is cooled to 1000 ° C. or lower, it is reoxidized in the furnace to become powdery zinc oxide, which is recovered as crude zinc oxide dust. Lead contained in a small amount in steel dust becomes dust in the form of lead oxide and is recovered as crude zinc oxide dust. Then, a part of the halogen derived from the primary raw material is recovered as a halogen compound bonded to a part of zinc and lead in a state of being mixed with the crude zinc oxide dust.

<Wet process>
The wet step S20 is a step of performing a wet treatment. The wet treatment includes crude zinc oxide dust obtained by adding a primary raw material (iron-containing crude zinc oxide raw material) to the reduction roasting step S10, which is an upstream step thereof, and a secondary directly charged into the wet step S20. Impurities such as chlorine contained in the "crude zinc oxide cake raw material" composed of the raw material (non-iron-containing crude zinc oxide raw material) are extracted into an aqueous sodium carbonate solution, and further solid-liquid separation treatment is performed to finally obtain impurities. Is a process for obtaining a crude zinc oxide cake by removing the zinc oxide cake by a water washing method. In the present specification, as the raw material for obtaining the crude zinc oxide cake, the above-mentioned crude zinc oxide dust and the secondary raw material to be put into the wet step S20 are collectively referred to as "crude zinc oxide cake raw material". It shall be.

FIG. 2 is a schematic view showing the basic configuration of the wet processing equipment 10 capable of performing the wet step S20. The wet treatment equipment 10 is provided with a coagulation tank 1 and a sedimentation separation device 2. Further, the sedimentation separation device 2 is further provided with a pH measuring device 3.

In the wet step S20, first, the crude zinc oxide cake raw material composed of the slurry obtained by repulping the crude zinc oxide dust recovered in the reduction roasting step S10 and the slurry obtained by crushing the secondary raw material is put into the coagulation tank 1. Will be done. In addition to the above-mentioned crude zinc oxide cake raw material, soda ash (sodium carbonate) and a coagulant are also added to the coagulation tank 1. Then, in the coagulation tank 1, impurities such as chlorine contained in the crude zinc oxide cake raw material are extracted and removed into the sodium carbonate aqueous solution.

The above slurry and each drug are stirred and mixed in the coagulation tank 1 and then sent to the sedimentation separation device 2. As the sedimentation separation device 2, for example, a general thickener can be preferably used. The solid settled and separated by the settling and separating device 2 is taken out from the bottom of the settling and separating device 2 and dehydrated by a filter, and then put into a drying and heating kiln in which the drying and heating step S30 is performed. As the filter, it is preferable to use a type such as a vacuum suction type that can continuously supply dehydrated crude zinc oxide cake. Further, the clear liquid overflowing from the upper part of the sedimentation separation device 2 is sent to the wastewater treatment step, but a part of the clear liquid is reused as process water.

The pH measuring device 3 is installed in the clarification liquid portion, and the amount of sodium carbonate added is adjusted so that the indicated value of the pH measuring device 3 becomes a specified pH.

In the wet step S20, the soda ash (Na ₂ CO ₃ ) is ionized in the aqueous solution as shown in the chemical formula (formula 1) shown below. Since the equilibrium formula of the chemical formula (formula 2) is biased to the right, the liquidity of the aqueous solution is alkaline. Further, as the "sodium aqueous solution-soluble chlorine compound" of the crude zinc oxide cake raw material, for example, the forms of lead chloride (PbCl ₂ ) and lead chloride fluoride (PbFCl) can be estimated. Then, it is presumed that the halogen extraction reaction from the crude zinc oxide cake raw material follows the chemical formulas (formula 3) and (formula 4). When the CO ₃ ^2- ions in the solution is consumed by the dehalogenation reaction represented by the chemical formula (Formula 3) (Formula 4), to move the equilibrium equation of Formula (Equation 2) is on the left, OH ^- ions are reduced pH Decreases. Therefore, since the pH measured by the pH measuring device 3 can be used as an index for confirming the progress of dehalogenation, the indicated value of the pH measuring device 3 can be used to maintain the specified pH. The amount of addition may be adjusted. Furthermore, according to the chemical formula (Formula 2), lead chloride (PbCl _2), the amount _CO ^{3 2-} in the amount of increase or decrease in accordance with the lead fluoride chloride (PbFCl), i.e. OH ^- of the amount of increase or decrease, i.e., the pH of the It turns out that an increase or decrease is necessary. Specifically, lead chloride (PbCl _2), if an increase in the amount of lead fluoride chloride (PbFCl), increase the allowed and _CO ^{3 2-} in the amount increase the setting pH, lead chloride (PbCl _2), fluoride chloride a decrease in the amount of lead iodide (PbFCl), or reducing the amount of _CO ^{3 2-} lowering the set pH.

Na ₂ CO ₃ → 2Na ⁺ + CO ₃ ^2-・ ・ ・ (Equation 1)
^{_{CO 3 2- + H 2 O ←}} → HCO 3 - + OH - ··· ( Formula 2)
PbCl ₂ + Na ₂ CO ₃ → _{PbCO 3} + 2 NaCl ... (Equation 3)
PbFCl + Na ₂ CO ₃ → _{PbCO 3} + NaF + NaCl ... (Equation 4)

Here, in general, in order to satisfy the standard value of zinc oxide roasting ore, which is a product in the production of zinc oxide ore, the chlorine grade of the crude zinc oxide cake may be suppressed to the reference value or less in this wet step S20. Desired. In the conventional production of zinc oxide ore, in consideration of the large variation in chlorine grade in the crude zinc oxide cake, the sedimentation separation device 2 is used to avoid the risk of abnormal chlorine grade in the zinc oxide burnt ore as a product. The pH setting of the above was fixed at a safe constant value (for example, pH 6.5), and a large amount of sodium carbonate was added in an amount necessary to maintain the pH setting, so to speak, over-control was performed.

On the other hand, in the production method of the present invention, in order to meet the above-mentioned requirements concerning the chlorine grade of the crude zinc oxide cake, the above-mentioned carbonic acid is prepared according to the content of "sodium aqueous solution-soluble chlorine" of the crude zinc oxide cake raw material. A "pH adjustment process" is performed to adjust the pH of the aqueous sodium solution.

Further, in the production method of the present invention, in order to perform the above-mentioned "pH adjustment treatment", the "crude zinc oxide cake raw material" to be charged into the wet step S20 at any stage before the wet step S20 is performed. Perform the "chlorine amount estimation process" to estimate the content of "sodium aqueous solution soluble chlorine". Hereinafter, methods for carrying out these two processes will be described with reference to specific examples.

(Chlorine amount estimation process)
The "chlorine amount estimation process" for estimating the content of "sodium aqueous solution-soluble chlorine" in the "crude zinc oxide cake raw material" can be performed, for example, by the method shown in the following paragraph.

In an example of the "chlorine amount estimation process", first, 10 times the weight ratio of water is added to the sample of the "crude zinc oxide cake raw material" to be processed for the chlorine amount estimation process, and the mixture is stirred. By filtering, a solid content in which the water-soluble chlorine compound has been removed from the above-mentioned "raw zinc oxide cake raw material" is obtained. Then, a sodium carbonate aqueous solution having a pH of 8 or more, which is 10 times the weight ratio of the solid content, is added and stirred, and the filtrate is obtained by filtering after stirring. Subsequently, the chlorine concentration of the filtrate is measured, and the amount of chlorine is obtained by multiplying the chlorine concentration by the volume of the filtrate. Further, the chlorine content of the "crude zinc oxide cake raw material" is obtained by dividing the chlorine amount by the weight of the "crude zinc oxide cake raw material". By multiplying the chlorine content obtained by the dissolution test in this way by the amount of the "crude zinc oxide cake raw material" input to the wet process, the content of the "sodium aqueous solution-soluble chlorine" of the "crude zinc oxide cake raw material" is estimated. be able to.

The "chlorine amount estimation process" according to the above method may be performed at any stage before the "crude zinc oxide cake raw material" to be processed to be subjected to the chlorine amount estimation process is put into the wet step S20. As an example, for crude zinc oxide dust, a sample can be obtained by collecting a slurry of crude zinc oxide dust and filtering it. As for the secondary raw materials, samples can be collected from each raw material that arrives in the form of a flexible container or the like. After obtaining each of these samples, the content of crude zinc oxide dust and "sodium aqueous solution-soluble chlorine" as a secondary raw material is determined by the above method. The amount of the "crude zinc oxide cake raw material" processed in the wet process varies depending on the crude zinc oxide dust and the secondary raw material. Therefore, the content of the above crude zinc oxide dust and the secondary raw material "sodium aqueous solution soluble chlorine" is used as a parameter, and the value is multiplied by the amount of the crude zinc oxide dust and the secondary raw material processed to obtain "sodium aqueous solution soluble chlorine". , And finally, by summing the contents of each "sodium aqueous solution-soluble chlorine", the content of "sodium aqueous solution-soluble chlorine" of the crude zinc oxide cake raw material can be estimated. The above method can be mentioned as an example of a preferable embodiment of the "chlorine amount estimation process".

Further, in the above-mentioned "chlorination amount estimation processing", when the secondary raw material is a mixture of a plurality of types of non-iron-containing crude zinc oxide raw materials, they are included in the individual secondary raw materials (non-iron-containing crude zinc oxide raw materials). "Chlorine content estimation processing" is performed individually for the content of "sodium aqueous solution soluble chlorine", and by multiplying the processing amount of each secondary raw material (non-iron-containing crude zinc oxide raw material), "crude zinc oxide cake raw material" The "chlorine amount estimation process" for determining the content of "sodium aqueous solution-soluble chlorine" can be performed.

Further, in the method for producing zinc oxide ore of the present invention, when the primary raw material to be charged into the reduction roasting step S10 is steel dust, the content of "sodium aqueous solution-soluble chlorine" in the "crude zinc oxide cake raw material" is increased. In the estimated chlorine amount estimation process, the chlorine amount calculation process is performed by regarding the content of "sodium aqueous solution-soluble chlorine" contained in the secondary raw material as the content of "sodium aqueous solution-soluble chlorine" in the crude zinc oxide cake raw material. , Can be carried out more easily.

It should be noted that the crude zinc oxide dust obtained by reducing and roasting steel dust contains almost no "sodium aqueous solution-soluble chlorine", and the finding that most of the contained chlorine is "water-soluble chlorine" is the invention of the present application. It is an original finding obtained by these subjects at the time of the above-mentioned dissolution test, and the above-mentioned embodiment is based on this original finding. Steel dust is dust generated when iron scrap is melted in electric furnaces and blast furnaces in the steel industry, and has a low lead content. Therefore, it is estimated that the content of _{lead chloride (PbCl 2} ) and lead chloride fluoride (PbFCl) in the crude zinc oxide dust obtained by reducing and roasting steel dust is also low.

(PH adjustment process)
As an example, the pH adjusting treatment for adjusting the pH of the sodium carbonate aqueous solution used in the wet step S20 according to the content of the "sodium aqueous solution-soluble chlorine" of the crude zinc oxide cake raw material estimated by the above-mentioned "chlorine amount estimation treatment" is used as an example. , Do as follows.

The pH adjustment treatment is performed according to the control target value of the chlorine grade in the crude zinc oxide cake obtained in the wet step S20. For example, in order to satisfy the product standard value of the chlorine grade of zinc oxide ore, it is necessary to adjust the chlorine grade of the crude zinc oxide cake obtained in the wet step S20 to about 1.2% or less.

Here, when steel dust is used as the primary raw material, the relationship between the pH of the sedimentation separation device 2 and the chlorine grade of the crude zinc oxide cake is stratified by the content of the secondary raw material "sodium aqueous solution-soluble chlorine". , It has been confirmed that there is a negative correlation between them as shown in FIG. According to FIG. 3, in order to adjust the chlorine grade of the crude zinc oxide cake to about 1.2% or less, the content of the secondary raw material "sodium aqueous solution-soluble chlorine" is 6.0 to 8.0 tons per day. In this case, adjust the pH of the aqueous sodium carbonate solution to 6.5, adjust the pH to 6.3 when it is 4.0 to 6.0 tons, and adjust the pH to 6.2 when it is 2.0 to 4.0 tons. I know it's good.

Therefore, for example, steel dust is used as the primary raw material, and as the secondary raw material, the secondary raw material A containing about 13% of "sodium aqueous solution-soluble chlorine" and the secondary raw material A containing about 3% of "sodium aqueous solution-soluble chlorine" are used. In the case of using the raw material B, the amount of each secondary raw material input to the wet step S20 (the amount processed per day) and the chlorine grade of the crude zinc oxide cake are in a preferable range based on the correlation shown in FIG. The pH setting value that can be kept inside can be defined as an optimum value at any time while flexibly fluctuating in the range of pH 6.0 or more and 6.5 or less. If the pH is less than 6.0, sodium carbonate is not added. Therefore, considering the fluctuation of the load amount of "sodium aqueous solution-soluble chlorine", the chlorine grade of the crude zinc oxide cake may exceed the control target value. When the pH is increased, the impurity cadmium forms a hydroxide and is mixed in the crude zinc oxide cake. The lower the pH, the more cadmium can be extracted and removed in the liquid. Further, from the viewpoint of reducing the amount of sodium carbonate used, which is a subject of the present invention, the lower the pH, the better. Therefore, the upper limit of pH is preferably 6.5.

Then, by controlling the amount of sodium carbonate used according to the pH setting value thus defined, the amount of sodium carbonate used can be reduced as compared with the conventional case, and the chlorine grade of the crude zinc oxide cake can be appropriately adjusted. Can be maintained.

In addition, a multidimensional matrix table (see FIG. 4) or a multidimensional graph showing the combination of the amounts of each secondary raw material input to the wet step S20 and the corresponding optimum pH value of the sedimentation separation device 2 is displayed. The pH adjustment process can be performed more efficiently by preparing the pH value in advance and setting the above pH value while manually referring to the pH value at any time or automatically by the information processing apparatus.

<Drying and heating process>
The crude zinc oxide cake obtained in the wet step S20 is put into a heating furnace such as a dry heating rotary kiln (DRK) and fired and granulated. In the dry heating step S30, the fluorine concentration is further reduced to produce zinc oxide ore. can do. The firing temperature in the drying and heating step S30 is preferably 1000 ° C. or higher and 1200 ° C. or lower.

<Other processes>
In the whole process of producing zinc oxide ore, an exhaust gas dust cleaning step is performed to clean the exhaust gas dust generated in the drying and heating step S30 to obtain an exhaust gas dust cake after cleaning. The cleaning equipment for performing this step can be a combination of a cleaning tower and a wet electrostatic precipitator. Further, in the same process, fluorine and cadmium are removed from the waste liquid containing high concentrations of fluorine and cadmium separated from the crude zinc oxide cake raw material in the wet step S20, and heavy metals contained in a trace amount in the waste liquid are removed. A wastewater treatment step is also carried out in which sediment is removed by neutralization treatment, and finally the pH is adjusted to make harmless wastewater.

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

(Example)
Steel dust is used as the primary raw material, and as the secondary raw material, "high lead Weltzkirundast" (secondary raw material A) and "crude zinc oxide recovered by RHF (Rotary Heart Finance)" (secondary raw material B). ) Was used to test the production of zinc oxide ore by the production method of the present invention.

The crude zinc oxide dust obtained by reducing and roasting the above-mentioned primary raw material and each of the above-mentioned secondary raw materials were put into a wet step. The input amounts of the crude zinc oxide dust, the secondary raw material A, and the secondary raw material B were 100 to 200 tons, 0 to 48 tons, and 0 to 75 tons, respectively, based on the dry amount per day.

When the "chlorine content estimation process" was performed in advance for the secondary raw material A and the secondary raw material B by the above-mentioned methods, the content of "sodium aqueous solution-soluble chlorine" for the secondary raw material A was determined. The content of the secondary raw material B was 12 to 13% by weight based on the dry amount, and the content was 2 to 3% by weight based on the dry amount.

Then, based on the combination of the amounts of each secondary raw material input to the wet step S20 prepared in advance and the multidimensional matrix table (see FIG. 4) showing the optimum pH value of the corresponding sedimentation separator, sedimentation separation is performed. The pH setting value of the treatment liquid in the apparatus was set to 6.0 to 6.5, and sodium carbonate (soda ash) in an amount commensurate with this pH value was added to the coagulation tank.

In this example, as a result, the amount of sodium carbonate (soda ash) added is 19.4 kg / t (soda ash basic unit (amount of soda ash used per ton of zinc oxide ore)), and drying and heating are performed. The chlorine grade of the zinc oxide ore obtained through the process was 0.76% by weight.

(Comparison example)
The pH setting value of the treatment liquid in the solid-liquid separator is fixed at 6.5 regardless of the content of "sodium aqueous solution-soluble chlorine" of the crude zinc oxide cake raw material, and the amount of sodium carbonate (sodium carbonate) corresponding to this pH value ( The production was carried out under the same conditions as in Examples except that sodium ash) was added to the coagulation tank.

In this comparative example, as a result, the amount of sodium carbonate (soda ash) added was 43.5 kg / t (soda ash basic unit (amount of soda ash used per ton of zinc oxide ore)), and it was dried and heated. The chlorine grade of the zinc oxide ore obtained through the process was 0.55% by weight.

In the examples, the chlorine grade of zinc oxide ore was slightly higher than that in the comparative example, but it was within a sufficiently acceptable range. On the other hand, in the examples, the soda ash basic unit was less than half that of the comparative example, and a sufficient effect was obtained.

From the above Examples and Comparative Examples, according to the production method of the present invention, it is possible to appropriately maintain the chlorine grade in the crude zinc oxide cake obtained from the wet step while suppressing the excessive use of sodium carbonate. I know what I can do.

1 Coagulation tank 2 Sedimentation separator (thickener)
3 pH measuring device 10 Wet processing equipment S10 Reduction roasting process S20 Wet process S30 Drying and heating process

Claims (4)

A reduction roasting process in which a primary raw material, which is an iron-containing crude zinc oxide raw material containing chlorine and iron, is reduced and roasted to obtain crude zinc oxide dust.
A crude zinc oxide cake raw material composed of the crude zinc oxide dust and a secondary raw material which is a non-iron-containing crude zinc oxide raw material containing chlorine and not iron is repulped with an aqueous sodium carbonate solution and then dehydrated. , Wet process to obtain crude zinc oxide cake,
In the process for producing zinc oxide ore, which comprises a drying and heating step of calcining the crude zinc oxide cake to obtain zinc oxide ore.
At any stage before the wet step, a chlorine amount estimation process for estimating the content of the sodium aqueous solution-soluble chlorine of the crude zinc oxide cake raw material is performed.
In the wet step, a method for producing zinc oxide ore, wherein the pH of the sodium carbonate aqueous solution is adjusted to a pH corresponding to the content of the sodium aqueous solution-soluble chlorine of the crude zinc oxide cake raw material. The primary raw material is steel dust,
The content of the aqueous sodium solution-soluble chlorine contained in the secondary raw material is regarded as the content of the sodium aqueous solution-soluble chlorine of the crude zinc oxide cake raw material, and the chlorine amount estimation process is performed.
The method for producing zinc oxide ore according to claim 1. The secondary raw material is a mixture of a plurality of types of the non-iron-containing crude zinc oxide raw materials.
In the pH adjustment treatment, the pH of the sodium carbonate aqueous solution is adjusted according to the sodium aqueous solution-soluble chlorine content contained in the individual non-iron-containing crude zinc oxide raw material and the amount of each of the non-iron-containing crude zinc oxide raw materials used. Do by doing,
The method for producing zinc oxide ore according to claim 2. After the pH adjustment treatment, the pH of the sodium carbonate aqueous solution is 6.0 or more and 6.5 or less.
The method for producing zinc oxide ore according to any one of claims 1 to 3.

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