JP6838390B2 - Manufacturing method of zinc oxide ore - Google Patents

Description

The present invention relates to a method for producing zinc oxide ore. More specifically, the present invention uses zinc oxide ore in the case where fine powdered crude zinc oxide having a higher zinc grade is used as an additional raw material in addition to a raw material ore having a relatively low zinc grade such as steel dust. Regarding the manufacturing method of.

Steel dust generated from blast furnaces and electric furnaces in the steel industry contains a considerable amount of zinc and lead components in addition to iron oxide, which is the main component of the steel dust. Is being recovered as zinc oxide ore.

As a general method for producing this zinc oxide ore, crude zinc oxide dust obtained by a reduction roasting step (Walez method) is subjected to a wet step to remove halogen components, and a zinc oxide-containing wet cake obtained in the wet step is obtained. A method of obtaining zinc oxide ore by baking (hereinafter referred to as "crude zinc oxide cake") in a dry-heating rotary kiln (DRK) that performs a drying-heating step is widely used.

Here, in the above-mentioned zinc oxide ore manufacturing process, in addition to the main raw materials such as steel dust, the steel dust generated at the steel mill is further on-site treated in the same place using a rotary hearth furnace or the like. A powdered material in the form of fine powder with a higher zinc grade may be used as an additional raw material. In the present specification, such a fine powdered raw material containing zinc oxide will be referred to as "crude zinc oxide fine powder". The crude zinc oxide fine powder derived from steel dust generally has an extremely small particle size of 2 μm or less in terms of the number-based average particle size (d50) and a water content of 3% by weight or less. Is.

As a procedure for treating such crude zinc oxide fine powder, a procedure (P1 in FIG. 1) that involves a step of repulping with crude zinc oxide dust in a wet step can be mentioned. However, in the case of this procedure, the cohesiveness in the sedimentation separation device after repulping is poor and the sedimentation rate is extremely slow, so that only a very small amount can be treated. Therefore, the slurry extracted from the bottom of the sedimentation separator, that is, the slurry concentration at the inlet of the solid-liquid separator could not be increased, and efficient processing could not be performed.

On the other hand, the above-mentioned crude zinc oxide fine powder has a high zinc grade and usually has a low content of impurities such as chlorine and fluorine. Therefore, as long as the chlorine concentration is not more than a predetermined concentration, the treatment procedure (P2 in FIG. 1) of directly feeding the crude zinc oxide cake that has undergone the wet step into the DRK that is subjected to the drying and heating step is followed. Can be considered. Each crude zinc oxide raw material such as a crude zinc oxide cake is usually charged into the DRK by a general-purpose quantitative charging device such as a screw feeder (see Patent Document 1).

However, since the crude zinc oxide fine powder has an extremely small particle size and is dried as described above, the crude zinc oxide fine powder and the crude zinc oxide cake can be completely prepared only by the general-purpose charging device as described above. It is difficult to mix with, and the crude zinc oxide cake in the form of a hydrous cake and the dried crude zinc oxide fine powder are mixed and charged into the DRK. Therefore, in the conventional process, the crude zinc oxide fine powder charged into the DRK has been taken away to the exhaust gas with a high carryover rate. In the present specification, the crude zinc oxide cake after the reduction roasting step, the crude zinc oxide fine powder, etc., were taken away in the DRK exhaust gas with respect to the weight of all the raw materials put into the drying and heating furnace such as DRK. The weight ratio of dust is referred to as "carryover rate" in the drying and heating process.

When the carryover rate in the drying and heating process increases to 8% by weight or more, dust adheres to and accumulates in the exhaust gas stack and the equipment in the DRK exhaust gas treatment equipment due to the increase in the dust concentration in the DRK exhaust gas. Problems such as blockage of the cleaning liquid piping due to an increase in the slurry concentration of the cleaning liquid occurred, which made it necessary to frequently stop the operation of the DRK, resulting in a decrease in the operating rate of the zinc oxide ore production facility.

JP-A-2009-144213

In view of the above situation, in the production of zinc oxide ore using crude zinc oxide fine powder having a high zinc grade as an additional raw material, zinc oxide is produced by reducing the carryover rate of the input material in the drying and heating step. An object of the present invention is to provide a manufacturing method capable of increasing the productivity of burnt ore.

Before putting the crude zinc oxide fine powder into the DRK, the present inventors knead and granulate the crude zinc oxide fine powder while applying a shearing force in advance to obtain crude zinc oxide pellets having predetermined properties. We have found that the problems can be solved and have completed the present invention. More specifically, the present invention provides the following.

(1) Zinc-containing raw material ore and crude oxidation having a higher zinc grade than the zinc-containing raw material ore, a chlorine concentration of less than 3%, a number-based average particle size (d50) of 2 μm or less, and a water content of 3% by weight or less. A method for producing zinc oxide ore using fine zinc powder as a raw material. The zinc-containing raw material ore is reduced and roasted in a rotary kiln for reduction roasting to reduce zinc contained in the zinc-containing raw material ore. A reduction roasting step of volatilizing to obtain crude zinc oxide dust, and a wet step of wet-treating the crude zinc oxide dust to remove water-soluble impurities contained in the crude zinc oxide dust to obtain a crude zinc oxide cake. And the kneading granulation step of pelletizing the crude zinc oxide fine powder, the crude zinc oxide cake, and the crude zinc oxide pellets obtained by pelletizing the crude zinc oxide fine powder are put into a rotary kiln for drying and heating. A drying and heating step of obtaining zinc oxide ore by firing the zinc oxide ore is provided. In the kneading and granulating step, the crude zinc oxide fine powder is kneaded by adding water while applying a shearing force. Further, it is a step of granulating and pelletizing while applying a shearing force, and the moisture content of the crude zinc oxide pellet after granulation is 14% by weight or more and 19% by weight or less, and particles having a particle diameter of 4 mm or more. A method for producing zinc oxide ore, which has a particle size distribution of 30% by weight or more.

(2) The method for producing zinc oxide ore according to (1), wherein the content of the crude zinc oxide pellets after granulation is 15% by weight or more.

(3) The method for producing zinc oxide ore according to (1) or (2), wherein the kneading is performed by a non-uniform speed twin-screw kneader and the granulation is performed by a non-uniform speed twin-screw granulator. ..

(4) The method for producing zinc oxide ore according to any one of (1) to (3), wherein the zinc-containing raw material ore is steel dust.

According to the present invention, in the production of zinc oxide ore using crude zinc oxide fine powder as an additional raw material, the productivity of zinc oxide burnt ore is increased by reducing the carryover of the input in the drying and heating step. Can provide a manufacturing method capable of

It is a flowchart which shows an example of embodiment of the manufacturing method of zinc oxide ore of this invention. It is sectional drawing of the rotary kiln which can carry out the manufacturing method of zinc oxide ore of this invention preferably.

Hereinafter, a preferred embodiment of the method for producing zinc oxide ore of the present invention will be described. However, the present invention is not limited to the following embodiments.

<Overall process>
As shown in FIG. 1, in the method for producing zinc oxide ore of the present invention, in addition to primary raw materials such as steel dust, crude zinc oxide fine powder having a higher zinc grade is produced in a zinc oxide ore production plant by the Waelz process. This is a production method that can be applied when the process of producing zinc oxide ore is carried out in combination. The overall process performed in the zinc oxide ore production plant by the Welts method is the reduction roasting step S10 to obtain crude zinc oxide by reducing and roasting primary raw materials such as steel dust, and the crude zinc oxide obtained in the reduction roasting step S10. Wet step S20 to obtain crude zinc oxide cake by separating and removing fluorine and cadmium from dust, and crude zinc oxide fine powder obtained in wet step S20 are dried and heated to produce zinc oxide (burnt ore). Obtaining Drying and Heating Step S40, Exhaust Gas Treatment Step S50 for Solid Air Separation Treatment to Separate DRK Exhaust Emissions Discharged from Drying and Heating Step S40 into Solid and Gas, and Wastewater for Separating Discharged Liquid Discharged from Wet Step S20 The processing step S60 is provided. The method for producing zinc oxide ore of the present invention is a kneading and granulation step in which crude zinc oxide fine powder to be put into the drying and heating step S40 is made into crude zinc oxide pellets having predetermined properties before being put into DRK. S30 is further performed as an indispensable step. The amount of zinc oxide produced in a production plant to which the method for producing zinc oxide ore of the present invention can be preferably applied is generally, for example, about 6 t / h or more and 10 t / h or less.

The general composition of the steel dust that can be used as a raw material in the production method of the present invention is as follows: zinc is 18% by weight or more and 35% by weight or less, lead is 0.2% by weight or more and 3.5% by weight or less, and iron. Is generally 15% by weight or more and 30% by weight or less, chlorine is 3% by weight or more and 4.5% by weight or less, and fluorine is 0.5% by weight or more and 0.8% by weight or less (all based on the dry amount). Is the target. The zinc content of 18% by weight or more and 35% by weight or less corresponds to the purity of zinc oxide of approximately 22% by weight or more and 44% by weight or less.

<Reduction roasting process>
As a specific method for performing the reduction roasting step S10, it is common to adopt a reduction roasting method using a reduction roasting rotary kiln (RRK). Further, steel dust is widely used as a primary raw material to be charged into RRK. Steel dust is continuously charged into RRK together with a carbonaceous reducing agent such as coal and coke and limestone. Inside the RRK body, the maximum temperature of the object to be treated is controlled to about 1100 to 1200 ° C. by the combustion of heavy oil and the combustion of the charged carbonaceous reducing agent. Steel dust is reduced and roasted in the RRK body, and the volatilized metallic zinc is reoxidized in the exhaust gas to become powdery zinc oxide. Lead contained in a small amount in steel dust volatilizes as lead oxide. Powdered zinc oxide, lead oxide and the like are introduced into the dust collector together with the exhaust gas from RRK, captured and recovered as crude zinc oxide dust. This crude zinc oxide dust generally contains about 8 to 20% of halogen impurities such as chlorine.

<Wet process>
In the wet step S20, the above halogen impurities contained in the crude zinc oxide dust recovered through the reduction roasting step S10 are separated and extracted into the treatment liquid, and further, the impurities are removed from the crude zinc oxide dust by the solid-liquid separation treatment. This is a step of performing a wet treatment. In the wet step S20, crude zinc oxide dust is repulped to obtain a slurry containing crude zinc oxide. By this treatment, halogen impurities such as chlorine and cadmium contained in the crude zinc oxide dust are mainly distributed in the treatment liquid. Then, in this state, the treatment liquid to which impurities are distributed is separated into a discharge liquid by solid-liquid separation. For the dehydration treatment for solid-liquid separation, a gravity settling slurry concentrator such as a thickener or a water forced dehydrator such as a vacuum dehydrator is used. Then, the above slurry from which impurities have been sufficiently removed is dehydrated by a vacuum suction type dehydrator or the like to obtain a wet cake containing zinc oxide (crude zinc oxide cake), which is put into the drying and heating step S40 of the next step.

<Kneading and granulation process>
The kneading and granulating step S30 is a step of converting the crude zinc oxide fine powder into crude zinc oxide pellets having "unique properties that are difficult to carry over" peculiar to the present invention before being charged into the DRK. This "unique property that does not easily carry over" means that the crude zinc oxide pellets have a specific particle size distribution and a specific water content range, and also remain in the pellets in a so-called "lump" state. It means that the amount of crude zinc oxide fine powder to be produced is extremely small. As used herein, the term "lump" refers to a state in which uncontrolled humidity dry fine powder is unevenly present. More specifically, it is a state in which the dry fine powder is sealed inside the pellet, or a state in which the pellet in the dry fine powder state is dispersed and sealed in the crude zinc oxide cake. In the production method of the present invention, the means for pelletizing the crude zinc oxide fine powder is specified as a method capable of kneading and granulating while applying a strong shearing force to the powder, thereby granulating. Later crude zinc oxide pellets can be provided with such "unique properties that are difficult to carry over".

[Crude zinc oxide fine powder]
Here, the crude zinc oxide fine powder to be treated by the production method of the present invention has a higher zinc grade and a higher chlorine concentration than the zinc-containing ore which is the primary raw material to be charged into the reduction roasting step S10 in the production method. It is a fine powder raw material of less than 3%. The zinc grade of this crude zinc oxide fine powder is preferably 50% by weight or more based on the dry weight. The number-based average particle size (d50) of the crude zinc oxide fine powder is 2 μm or less, and the water content is 3% by weight or less. For example, coarse zinc oxide dust in the form of fine powder generated by on-site treatment of steel dust generated in a steel mill using a rotary hearth furnace or the like in the steel mill is widely applicable, and zinc oxide ore It is used as a general secondary raw material in the production of. The particle size of the fine powder is a numerical value that can be measured by a laser analysis / scattering method.

The composition of the above-mentioned crude zinc oxide fine powder derived from steel dust is 52% by weight of zinc, 4% by weight of lead, 12% by weight of iron, 2% by weight of chlorine, and 0.5% by weight of fluorine (any of them). Generally, it is about the dry amount standard). The zinc content of 52% by weight corresponds to approximately 65% by weight of zinc oxide purity.

In the whole process of conventional general zinc oxide production, the crude zinc oxide fine powder is put into a wet step (P1), or in many cases, the crude zinc oxide cake obtained in the wet step S20. At the same time, it is directly charged into the DRK in which the drying and heating step S40 is performed (P2). As described above, in the former case (P1), the productivity is mainly due to the low processing efficiency of the wet treatment, and in the latter case (P2), the productivity is mainly due to the high carryover rate. There was a problem that it was forced to decline. In the production method of the present invention, crude zinc oxide fine powder is kneaded by adding water with a non-uniform speed twin-screw kneader, and then granulated by a non-uniform speed twin-screw granulator. By obtaining crude zinc oxide pellets having "difficult-to-difficult properties" and directly feeding them into the DRK, the problems in any of the above cases can be solved.

[Crude zinc oxide pellets]
In the production method of the present invention, the above crude zinc oxide fine powder is kneaded by adding water while applying a shearing force, and then granulated while further applying a shearing force to obtain "unique properties". By using the provided crude zinc oxide pellets, the above-mentioned carryover rate can be significantly reduced. Kneading and granulation performed while applying a shearing force can be performed using a non-constant velocity biaxial kneader and a non-constant velocity biaxial granulator.

The crude zinc oxide pellets granulated by the kneading and granulating step in the production method of the present invention have a water content of 14% by weight or more and 19% by weight or less, preferably 15% by weight or more and 19% by weight or less. If the water content of the crude zinc oxide pellets is less than 14% by weight, the proportion of pellets, so-called "lumps", in which unconditioned humidity dry fine powder is encapsulated increases. The strength of the pellets in the "lump" state is extremely low, increasing the carryover rate in the DRK. Further, when the crude zinc oxide pellets are conveyed, they are easily crushed by a drop impact or the like at the time of transfer between conveyors constituting the transfer device, which causes dust generation. On the other hand, if the water content of the crude zinc oxide pellets exceeds 19% by weight, the proportion of cake-like or paste-like products that cannot be granulated due to excessive water content increases, the amount of adhesion to the transport device increases, or for quantitative cutting. It becomes difficult to transport due to the shelving of the hopper.

Regarding the particle size of the crude zinc oxide pellets after granulation, the particle size distribution should be such that the proportion of particles having a size of 4 mm or more is 30% by weight or more. Since the particle size of the crude zinc oxide pellets after granulation varies depending on the granulation time, it can be adjusted to the above range by, for example, optimizing the rotation speed of the stirring blade of the granulator. By keeping the particle size distribution of the crude zinc oxide pellets in the above range, it is possible to suppress carryover and also suppress dust generation from the conveyor of the transport device during transport of the fine powder of crude zinc oxide powder.

[Non-constant speed twin-screw kneader / non-constant speed twin-screw granulator]
In the production method of the present invention, in order to perform kneading and granulation while applying a shearing force to crude zinc oxide fine powder, a non-uniform speed twin-screw kneader and a non-uniform speed twin-screw granulator It is preferable to carry out each of these treatments using.

The non-constant speed biaxial kneader has a plurality of plate-shaped or rod-shaped stirring blades arranged on the rotating shaft, which is compared with a general drum-type kneader or pan-type kneader. Since the shearing force works, it has a feature that the mixing ability of powdery substances is high. Further, since the rotation speeds of the respective shafts are unequal, the mixing capacity becomes higher. The rotation speed ratio of each axis is set to, for example, 4: 5. Water as a binder during granulation is added to the crude zinc oxide fine powder kneaded with a non-uniform velocity twin-screw kneader, and the moisture content of the crude zinc oxide pellets after granulation is within a specific range. The humidity is adjusted so that it becomes.

Similar to the non-constant velocity biaxial kneader, the non-constant velocity biaxial granulator also has a plurality of plate-shaped or rod-shaped stirring blades arranged on the rotating shaft, and is a general drum type. Compared with a granulator or a pan-type granulator, the mixing state is good, and the above-mentioned lumps are extremely unlikely to occur. Further, since the rotation speeds of the respective shafts are unequal, the mixing capacity becomes higher. The rotation speed ratio of each axis is set to, for example, 4: 5.

The non-constant velocity twin-screw kneader and the non-constant velocity twin-screw granulator are not necessarily essential constituents of the present invention, but crude zinc oxide for exhibiting the effects of the present invention with high accuracy. The devices currently available as a means of granulating pellets are substantially limited to these devices. Of course, as long as it is a kneaded granulation means capable of imparting a high shearing force to the crude zinc oxide fine powder in the process of kneading and granulation, even if it is a process performed by other means similar to the above apparatus, the scope of the present invention Is.

<Drying and heating process>
In the drying and heating step S40, the zinc oxide cake and the crude zinc oxide pellets having the properties peculiar to the present invention, which can be obtained through the above-mentioned zinc oxide cake and the kneading and granulating step S30 in the wet step S20, are charged into the DRK and fired. This is a step of further reducing the concentrations of cadmium and fluorine to obtain zinc oxide ore (calcination).

The heating temperature in the drying and heating step S40 is preferably maintained and managed so that the temperature of the burnt ore when discharged from the DRK is 1100 ° C. or higher and 1150 ° C. or lower. Here, the form of fluorine still remaining in the crude zinc oxide cake charged into the DRK is generally mostly lead chloride (PbFCl) and partly calcium difluoride (CaF ₂ ). It has become. Of these, almost all of PbFCl is decomposed and volatilized by maintaining the temperature of the burnt ore within the above temperature range, and almost all of chlorine and fluorine derived from PbFCl are discharged to the exhaust gas treatment facility in the exhaust gas treatment step S50.

The moisture content of the crude zinc oxide cake to be treated in this drying and heating step S40 is generally 20% by mass or more and 30% by mass or less. The general composition of this crude zinc oxide cake is that zinc is 61% by mass or more and 68% by mass or less, lead is 7% by mass or more and 10% by mass or less, and chlorine is 0.3% by mass or more and 0.9% by mass or less. , Fluorine is 0.2% by mass or more and 1.5% by mass or less (both are based on the dry amount). This crude zinc oxide cake is charged into the DRK by a quantitative charging device such as a screw feeder together with the crude zinc oxide pellets obtained by pelletizing the above-mentioned crude zinc oxide fine powder.

The crude zinc oxide cake and the crude zinc oxide pellets charged into the DRK are dried, heated, and fired on the discharge end side.

The exhaust gas generated by the DRK is sucked from the charging end side, removed via a wet exhaust gas cleaning facility and a wet electrostatic precipitator, and discharged from the chimney via a blower such as a fan.

In the drying and heating step, the size of zinc oxide ore discharged from DRK is generally 1 mm or more and 6 mm or less, and its general composition is 60% by mass or more and 70% by mass or less of zinc and 3% by mass or more of lead. 5% by mass or less, chlorine is 0.5% by mass or more and 1.5% by mass or less, and fluorine is about 0.6% by mass or less (all based on the dry amount).

[Rotary Kiln]
As the DRK used for performing the drying and heating step S40, a rotary kiln 1 as shown in FIG. 2 can be used. The rotary kiln 1 is a heating device provided near the kiln main body 10 which is a cylindrical kiln having fire resistance, a transport device 20 which is a means for transporting zinc oxide cake and crude zinc oxide pellets, and a discharge port 12 side of the kiln main body 10. Yes The burner section 30, which is the heat source of the rotary kiln 1, the drive gear 40 that transmits the rotational force in the R direction in the figure to the kiln body 10, the fixed hood 50 that prevents the diffusion of exhaust gas discharged from the kiln body 10, and the kiln. It is a rotary heating furnace provided with a kiln support portion (not shown) that supports the main body 10.

The rotary kiln 1 having the above configuration heats the inside of the kiln main body 10 to a high temperature of about 1100 ° C. or higher and 1300 ° C. or lower by the burner portion 30, and conveys the kiln main body 10 in a state of being rotated in the R direction by the drive gear 40. The apparatus 20 continuously charges the DRK charging raw material 2, which is a mixture of zinc oxide cake and zinc oxide pellets, from the charging port 11 in the a direction shown in FIG. The DRK input raw material 2 of the zinc oxide cake and zinc oxide pellets moves in the kiln body 10 toward the discharge port 12 while being stirred and fired along the inclination of the kiln body 10, and the temperature is high from the discharge port 12. It is discharged in the b direction as a product to be fired.

The transport device 20 is a device for transporting and charging zinc oxide cake to be charged into the kiln main body 10 into the kiln main body 10, and is inserted and arranged in the furnace from the furnace butt side of the kiln main body 10. The transport device 20 is not particularly limited, but as an example, a non-uniform speed twin-screw conveyor that exhibits excellent stirring power particularly during transport of zinc oxide cake can be preferably used.

In the non-constant speed biaxial screw conveyor, unlike a belt conveyor and a conventionally known general screw conveyor, two rotating shafts rotate at a non-constant speed. Therefore, a delicate different phase conversion occurs, and the kneaded blades scrape each other's transported objects. As a result, the non-constant velocity twin-screw conveyor can smoothly convey the DRK input raw material 2 containing the highly adhesive zinc oxide cake while self-cleaning without clogging.

The temperature of the zinc oxide ore burnt discharged from the rotary kiln is continuously measured and monitored by a radiation thermometer. Here, the firing temperature is maintained and managed so as to be in the range of 900 ° C. or higher and 1200 ° C. or lower at the firing temperature of zinc oxide ore.

<Exhaust gas treatment process>
In the exhaust gas treatment step S50, the solid air separation treatment of the DRK exhaust gas discharged from the DRK is performed in the drying and heating step S40. The separated and recovered DRK exhaust gas dust is washed and recycled as a zinc oxide-containing slurry in the wet step S20, which is an upstream step of the drying and heating step S40, to perform a treatment for effective utilization of metal resources.

<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 crude zinc oxide in the wet step S20, and further neutralizes heavy metals contained in a trace amount in the waste liquid. This is a step of forming a precipitate and finally adjusting the pH to make harmless wastewater.

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 preferable effects arising from the present invention, and the effects according to the present invention are not limited to the above embodiments.

In a crude zinc oxide production plant capable of carrying out the entire process shown in FIG. 1, a test operation of crude zinc oxide ore production by the production method of the present invention was carried out. The effect of the present invention was verified by measuring the carryover rate of the raw material in the drying and heating step in the test operation of each Example and Comparative Example and observing the state of dust generation during transportation to the DRK. In each operation, steel dust and crude zinc oxide fine powder having the compositions shown in Table 1 below were used as raw materials.
The measurement and observation results are as shown in Table 2 below.

[Example 1]
(Kneading and granulation process)
Regarding the kneading and granulation process in which the crude zinc oxide fine powder to be input to the DRK is used as crude zinc oxide pellets, the following kneading and granulation can be performed while applying shearing force to the fine powdered raw material. This was done using a granulator. The amount of water added as a binder during kneading was adjusted so that the water content of the crude zinc oxide pellets was 19% by weight. The treatment amount of the crude zinc oxide fine powder in the kneading and granulating step was 15 t / h. The particle size distribution of the crude zinc oxide pellets after granulation measured by the sieving method was 85% by weight in a proportion of 4 mm or more.
Non-constant speed twin-screw kneader: "Dow Mixer (registered trademark)" manufactured by Shin Nichinan Co., Ltd.
Non-constant speed twin-screw granulator: "Dow Peletizer (registered trademark)" manufactured by Shin Nichinan Co., Ltd.
The rotation speeds of the non-uniform speed twin-screw kneader were set to 20 RPM and 25 RPM (60 Hz at the inverter frequency), and the rotation speeds of the non-uniform speed twin-screw granulator were also set to 20 RPM and 25 RPM (60 Hz at the inverter frequency).
(Drying and heating process)
The crude zinc oxide pellets obtained in the above kneading and granulation step were put into a DRK for producing 7 to 8 t / h zinc oxide ore at a treatment amount of 1 to 2 t / h.

[Example 2]
(Kneading and granulation process)
In the kneading and granulation step in which the crude zinc oxide fine powder charged into the DRK was used as the crude zinc oxide pellets, the amount of water added as a binder was adjusted so that the water content of the crude zinc oxide pellets was 15% by weight. Except for the above, the same equipment and conditions as in Example 1 were used. The particle size distribution of the crude zinc oxide pellets after granulation measured by the sieving method was 70% by weight in a proportion of 4 mm or more.
(Drying and heating process)
The drying and heating step was carried out under the same conditions as in Example 1.

[Example 3]
(Kneading and granulation process)
In the kneading and granulation step in which the crude zinc oxide fine powder charged into the DRK was used as the crude zinc oxide pellets, the amount of water added as a binder was adjusted so that the water content of the crude zinc oxide pellets was 14% by weight. Except for the above, the same equipment and conditions as in Example 1 were used. The particle size distribution of the crude zinc oxide pellets after granulation measured by the sieving method was 35% by weight in a proportion of 4 mm or more.
(Drying and heating process)
The drying and heating step was carried out under the same conditions as in Example 1.

[Comparative Example 1]
(Kneading and granulation process)
In the kneading and granulation step in which the crude zinc oxide fine powder charged into the DRK was used as the crude zinc oxide pellets, the amount of water added as a binder was adjusted so that the water content of the crude zinc oxide pellets was 20% by weight. Except for the above, the same equipment and conditions as in Example 1 were used. As a result, it became a water-containing cake because it could not be granulated due to excessive water content, and the amount of adhesion to the transport belt and the cut-out hopper increased, which made it difficult to transport.

[Comparative Example 2]
(Kneading and granulation process)
The crude zinc oxide fine powder was put into the DRK as it was without performing the kneading and granulating step (procedure of P2 in FIG. 1).
(Drying and heating process)
According to the conditions of Example 1, the above crude zinc oxide fine powder was charged into a DRK for producing 7 to 8 t / h zinc oxide ore at a treatment amount of 1 to 2 t / h.

[Comparative Example 3]
(Kneading and granulation process)
In the kneading and granulation process in which the crude zinc oxide fine powder to be input to the DRK is used as crude zinc oxide pellets, the raw material in the form of fine powder is kneaded by a general drum type kneader and a pan type granulator. Using a granulator, kneading and granulation was performed without applying a shearing force. The amount of water added as a binder during kneading was adjusted so that the water content of the crude zinc oxide pellets was 19% by weight as in Example 1. The treatment amount of the crude zinc oxide fine powder in the kneading and granulating step was also set to 15 t / h as in the examples. The particle size distribution of the crude zinc oxide pellets after granulation measured by the sieving method was 80% by weight in a proportion of 4 mm or more.
(Drying and heating process)
The drying and heating step was carried out under the same conditions as in Example 1.

From the above results, in the production of zinc oxide burnt ore, the production method of the present invention uses a crude zinc oxide fine powder, for example, a non-uniform velocity twin-screw kneader and a non-uniform velocity twin-screw kneader when the crude zinc oxide fine powder is charged into the DRK. It is a manufacturing method that can reduce the carryover rate by kneading and granulating while applying shearing force by a kneading and granulating device consisting of a non-constant velocity twin-screw granulator. It can be seen that this is a production method that can contribute to the improvement of the productivity of zinc oxide ore.

S10 Reduction roasting process S20 Wet process S30 Kneading and granulation process S40 Drying and heating process S50 Exhaust gas treatment process S60 Wastewater treatment process 1 Rotary kiln 2 DRK Raw material 10 Kiln body 11 Input port 12 Discharge port 20 Conveyor device 30 Burner section 40 Drive gear 50 Fixed hood

Claims (4)

Zinc-containing raw material ore and crude zinc oxide fine powder having a higher zinc grade than the zinc-containing raw material ore, a chlorine concentration of less than 3%, a number-based average particle size (d50) of 2 μm or less, and a water content of 3% by weight or less. Is a method for producing zinc oxide ore using
A reduction roasting step in which zinc contained in the zinc-containing raw material ore is reduced and volatilized to obtain crude zinc oxide dust by reducing and roasting the zinc-containing raw material ore in a rotary kiln for reduction roasting.
A wet step of removing water-soluble impurities contained in the crude zinc oxide dust by wet-treating the crude zinc oxide dust to obtain a crude zinc oxide cake.
The kneading and granulating step of pelletizing the crude zinc oxide fine powder and
The crude zinc oxide cake and the crude zinc oxide pellets obtained by pelletizing the crude zinc oxide fine powder are put into a rotary kiln for drying and heating and calcined to obtain zinc oxide ore.
The kneading and granulating step is a step of kneading the crude zinc oxide fine powder by adding water while applying a shearing force, and then granulating and pelletizing the crude zinc oxide fine powder while further applying a shearing force.
The crude zinc oxide pellets after the granulation, the water content is at 19 wt% or less 14 wt% or more and the ratio of particles diameter 4mm or more of the particles is 30 wt% or more of the particle size distribution, zinc oxide ore Manufacturing method. The method for producing zinc oxide ore according to claim 1, wherein the content of the crude zinc oxide pellets after granulation is 15% by weight or more. The method for producing zinc oxide ore according to claim 1 or 2, wherein the kneading is performed by a non-uniform speed twin-screw kneader, and the granulation is performed by a non-uniform speed twin-screw granulator. The method for producing zinc oxide ore according to any one of claims 1 to 3, wherein the zinc-containing raw material ore is steel dust.

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