JP2016166381A - Method for producing zinc oxide ore - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a zinc oxide ore capable of obtaining a zinc oxide ore with high quality while maintaining the high working rate of a rotary kiln.SOLUTION: There is provided a method for producing a zinc oxide ore comprising: a preliminary mixing step where a raw material ore and a carbonaceous reducing agent are mixedly granulated to obtain a reducing agent-inner packaged pellet; a reduction roasting step where the reducing agent-inner packaged pellet is roasted to obtain crude zinc oxide; a wet step where a halogen group element(s) is removed from the crude zinc oxide by wet treatment to obtain a crude zinc oxide cake; and a dry heating step where the crude zinc oxide cake is fired by a drying heating furnace. In the preliminary mixing step, the raw material ore to be used has a grain size distribution in which the ratio of 0.5 mm under is 10% or lower, the carbonaceous reducing agent to be used in the preliminary mixing step has a grain size of 200 μm or lower, and also, the content ratio of the carbonaceous reducing agent in the reducing agent-inner packaged pellet is controlled to 18% or lower.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 includes a drying heating step of obtaining zinc oxide by firing crude zinc oxide that is an intermediate product.

  Conventionally, zinc oxide ore obtained by separating and removing impurities from a 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 can be obtained, for example, by subjecting steel dust generated from a steelmaking furnace such as a blast furnace or an electric furnace in the steel industry to a reduction roasting treatment. This reduction roasting treatment of steel dust is generally performed by a reduction roasting treatment using a rotary kiln.

  When performing reduction roasting treatment with a rotary kiln, steel dust as a raw material is put into the rotary kiln together with a carbonaceous reducing agent such as carbon. In addition, in order to further improve the volatility of zinc, steel dust to be put into the rotary kiln is mixed and granulated with a carbonaceous reducing agent in advance to form a reducing agent-incorporated pellet having a size of about 5 to 10 mm. Is also widely performed (see Patent Document 1).

  In the rotary kiln that performs the reduction roasting treatment, the maximum temperature is controlled to about 1100 to 1200 ° C. by the combustion of fuel heavy oil and the carbonaceous reducing agent. Steel dust is reduced and roasted in the rotary kiln, and the volatilized metallic zinc is reoxidized and solidified in the kiln, and then collected as particulate crude zinc oxide by an electric dust collector or the like. Then, the recovered crude zinc oxide is further converted into zinc oxide ore having further improved the zinc quality to a necessary level by further separating impurities by a subsequent wet process or drying heating process, and becomes a raw material for zinc smelting .

  Here, from the viewpoint of promoting resource recycling, it is desirable to reuse the steel dust as a zinc raw material. However, on the other hand, the crude zinc oxide derived from steel dust contains impurities composed of halogen group elements such as fluorine and chlorine at a certain concentration in addition to the main component zinc oxide.

  Here, in order to improve the quality of zinc, which is the final product, it is required that the halogen concentration of zinc oxide ore as the material be extremely low.

  In order to reduce the halogen concentration of zinc oxide ore, as a method of separating and removing halogen group elements from crude zinc oxide after reduction roasting, a method in which halogen components are volatilized and separated by baking in a dry heating furnace (patent document) 2).

  As a means for separating and removing the halogen group elements, there is a method of increasing the volatilization rate of the halogen group elements by increasing the temperature in the rotary kiln in which the above firing is performed. However, when the temperature in the rotary kiln is increased to, for example, about 1300 ° C., the reaction product by the drying heat treatment softens and melts and adheres to the inner wall of the rotary kiln, and the deposit increases as the operation time elapses. However, there is a drawback that the raw material becomes an obstacle when moving in the rotary kiln, and eventually the operation is stopped.

  At the zinc oxide ore production site, in order to obtain high-grade zinc oxide ore by removing the halogen group elements, it is currently necessary to tolerate a decrease in the operating rate of the rotary kiln due to high-temperature operation. There has been a demand for a method for producing zinc oxide ore that can obtain high-grade zinc oxide ore while maintaining a high operating rate.

JP 2008-261005 A JP-A-9-125169

  An object of this invention is to provide the manufacturing method of the zinc oxide ore which can obtain a high quality zinc oxide ore, maintaining the high operation rate of a rotary kiln.

  In a total process for producing zinc oxide ore from crude zinc oxide, pellets in which a carbonaceous reducing agent such as carbon is incorporated are preferably used as raw materials to be input into the reduction roasting step. As a result of original research, the present inventors have obtained knowledge that the above-mentioned problems can be solved by controlling the amount of carbon derived from this carbonaceous reducing agent in the drying and heating step to a certain amount or less. It was. As a specific means for realizing this, when manufacturing pellets with the above-described reducing agent built therein, the particle diameters of the raw material ore and the carbonaceous reducing agent and the carbon concentration in the pellet are predetermined. By controlling within the optimum value range, it was found that the amount of carbon mixed into the drying and heating step can be kept below a certain amount, and the present invention has been completed. More specifically, the present invention provides the following.

  (1) A zinc oxide ore production method for producing zinc oxide ore from zinc-containing powdery raw ore, wherein the raw material ore and a carbonaceous reducing agent are mixed and granulated to obtain a reducing agent-incorporated pellet. A mixing step, a reduction roasting step of roasting the reducing agent-incorporated pellets to obtain crude zinc oxide, a wet step of removing a halogen group element from the crude zinc oxide by a wet treatment to obtain a crude zinc oxide cake, A drying heating step of baking the crude zinc oxide cake in a drying heating furnace, and the raw material ore used in the preliminary mixing step has a particle size distribution with a ratio of 0.5 mm under 10% or less, The method for producing zinc oxide ore, wherein the carbonaceous reducing agent used in the mixing step has a particle size of 200 μm or less, and the content ratio of the carbonaceous reducing agent in the reducing agent-incorporated pellet is 18% or less.

  (2) The method for producing zinc oxide ore according to (1), wherein the raw material ore has a particle size distribution in which a ratio of 6.7 mm over is 50% or more.

  (3) The drying heating furnace is a drying heating rotary kiln, firing by the drying heating rotary kiln is performed at 1100 ° C. or more and 1150 ° C. or less, and a zinc recovery rate from the crude zinc oxide cake in the drying heating step is 95% or more. The method for producing zinc oxide ore according to (1) or (2).

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

  (5) The method for producing zinc oxide ore according to any one of (1) to (4), wherein the carbonaceous reducing agent is recycled carbon.

  ADVANTAGE OF THE INVENTION According to this invention, in manufacture of a zinc oxide ore, a high quality zinc oxide ore can be obtained, maintaining the operation rate of a rotary kiln. More specifically, zinc oxide ore having a zinc grade of 65% or more can be stably obtained.

It is a flowchart which shows an example of the manufacturing method of the zinc oxide ore of this invention. It is a graph which shows the relationship between the carbon input to the drying heating process of the manufacturing method of the zinc oxide ore of this invention, and product zinc quality.

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

<Overall process>
The method for producing zinc oxide ore of this example is a method characterized by improving the zinc quality of zinc oxide ore by controlling the amount of carbon mixed in the drying and heating step. Such a manufacturing method of the present invention can be preferably applied to, for example, the entire process as shown in FIG. According to such an embodiment, the zinc quality of zinc oxide ore can be maintained in a high concentration range, specifically, a concentration of 65% or more while maintaining the operation rate of the rotary kiln.

  As shown in FIG. 1, the entire process includes a premixing step S10 in which a powdered raw material ore such as steel dust and a carbonaceous reducing agent such as recycled carbon are mixed and granulated to form a reducing agent-incorporated pellet, Reducing agent-incorporated pellets and other steel dusts are reduced and roasted to obtain crude zinc oxide. Reduction roasting step S20 to obtain crude zinc oxide. From the crude zinc oxide obtained in the reduction roasting step S20, halogen group elements such as fluorine and chlorine. Is separated and removed from the treatment liquid to obtain a crude zinc oxide cake, and a dry heating step S40 to obtain a zinc oxide ore by drying and heating the crude zinc oxide cake obtained in the wet step S30, and a drying heating step S40. An exhaust gas dust cleaning step S50, a waste water treatment step S60, and a carbon concentration measurement step S70 for cleaning the exhaust gas dust generated in step 1 to obtain an exhaust gas dust cake after cleaning are provided.

  The method for producing zinc oxide ore of the present embodiment is characterized in that the grade of zinc oxide ore is controlled by controlling the carbon concentration of the crude zinc oxide cake charged into the drying and heating rotary kiln (DRK) in the drying and heating step S40 to a predetermined range or less. Based on the unique knowledge that it can be improved, such control is realized mainly by optimizing the material and formulation of the reducing agent-incorporated pellets. According to this method, the zinc quality of the zinc oxide ore can be maintained at a high concentration of 65% or more while maintaining the operation rate of the rotary kiln. Such zinc oxide ore can be preferably used as zinc oxide ore for electrolytic smelting.

<Preliminary mixing process>
The pre-mixing step S10 is a step prior to the reduction roasting step S20, in which a powder mainly composed of a raw material ore such as steel dust and a carbonaceous reducing agent such as recycled carbon is mixed and granulated to form a reducing agent-incorporated pellet. It is. For this mixing granulation, a generally used pelletizing apparatus can be used. For example, using a rotating pan-type pelletizer, steel dust, recycled carbon, and other additives as necessary are continuously supplied to achieve a predetermined pellet composition, and mist-like moisture is added. While pelletizing. The pellet size is preferably about 5 to 10 mm, and the water content is preferably about 10 to 15% by mass.

  In the production method of the present invention, as a raw material ore, a powdery raw material ore whose particle size distribution is in the specific range of the present invention can be used. That is, a powdery raw material ore having a particle size distribution with a 0.5 mm under ratio of 10% or less can be used. This is because, when the particle size distribution of the raw ore exceeds 0.5%, the amount of carbon mixed in the DRK in the drying and heating process increases to an unfavorable range. The reason why the amount of carbon mixed in DRK increases is considered as follows. First, if the proportion of raw ore with a very small particle diameter increases to a certain ratio or more as described above, it becomes the core during pellet formation, and it is a minimum that does not reach the minimum particle diameter that can maintain the strength of the whole pellet. The proportion of particles will increase. For this reason, the ratio of the reducing agent which will be mixed in the reduction roasting process with the pellet of relatively small intensity | strength and the state of a very small fine powder without being pelletized increases. Many of these relatively low-strength pellets roll in the reductive roasting rotary kiln (RRK) in which the reductive roasting process is performed, or are crushed gradually while moving while rubbing each other. The agent scatters in the RRK. Most of the scattered reducing agent and the reducing agent mixed in the RRK in the form of the above-mentioned extremely fine powder are not able to perform the function as the reducing agent and are carried on the air flow in the RRK. It will be carried out of the RRK. From the above, regarding the particle size distribution of the raw ore, when the ratio of under 0.5 mm exceeds 10%, it is considered that the amount of carbon mixed in the DRK in the drying and heating process increases.

  Further, for this particle size distribution, the ratio of 6.7 mm over is more preferably 50% or more. This is because the amount of carbon mixed into DRK in the drying and heating step increases to an unfavorable range when the 6.7 mm over ratio is less than 50% in the particle size distribution of the raw material ore. As the proportion of the raw material ore having a small particle size increases, the particles that become the core of the pellet become smaller, so the strength of the pellet decreases. Also in this case, as described above, many of the relatively low strength pellets are gradually broken in the RRK, and the reducing agent in the pellet is scattered in the RRK. And many of these scattered reducing agents will be carried out of RRK on the airflow in RRK, without being able to exhibit the function as a reducing agent. From the above, regarding the particle size distribution of the raw ore, when the ratio of over 6.7 mm is less than 50%, it is considered that the amount of carbon mixed in the DRK increases in the drying and heating step.

  As long as the above conditions for the particle size distribution are satisfied, various powdered ores containing valuable metals including zinc can be used as raw material ores. Also, dust or sludge generated in a metal refining process or processing process, which can be pelletized, or a slurry can be used. Among these, steel dust can be preferably used from the viewpoint of promoting resource recycling and reducing costs. Hereinafter, the case where steel dust is used as the raw ore of crude zinc oxide in the method for producing zinc oxide ore of the present invention will be described.

  As long as the above-mentioned conditions concerning the particle size distribution are satisfied, the steel dust is generally high in zinc quality, and is therefore steel dust having a relatively low zinc volatility under general reduction roasting conditions (hereinafter also referred to as “steel dust A”). May be. For such steel dust A as well, a general steel dust having a relatively high volatility of zinc (hereinafter also referred to as “steel dust B”) is obtained by preliminarily mixing with the reducing agent in the preliminary mixing step S10. Can be recovered by volatilizing zinc at a high volatility rate in the same manner as in the case where the carbonaceous reductant is not put in the interior and put into the reduction roasting furnace.

  In the production method of the present invention, as the carbonaceous reducing agent, a powdery reducing agent having a particle size in the predetermined range of the present invention can be used. That is, it is possible to use a reducing agent such as carbon having a particle diameter of 200 μm or less or recycled carbon, which can be pelletized, or a slurry.

  As the carbonaceous reducing agent, recycled carbon can be preferably used from the viewpoint of promotion of resource recycling and cost reduction. Recycled carbon is generally uniformly in the form of powder and is relatively inexpensive and easily available compared to other carbonaceous reducing materials. Such powdery recycled carbon is excellent in dispersibility in the reducing agent-incorporated pellets and is easy to granulate. From the above, powdered recycled carbon can be used particularly preferably as a carbonaceous reducing agent used in the production method of the present invention. Hereinafter, in this specification, the case where powdery recycle carbon is used as a carbonaceous reducing agent used in order to obtain a reducing agent interior pellet in the manufacturing method of zinc oxide ore of the present invention is explained.

  In the reducing agent-incorporated pellets produced by mixing and granulating steel dust A and recycled carbon with a pan-type pelletizer, the carbon concentration at the time of mixing and granulation is adjusted to 18% or less.

  As described above, by maintaining the particle size distribution of the powdered material used for the production of the reducing agent-incorporated pellets and the carbon concentration in the pellets within the above specific range, each step is followed to DRK in the drying and heating step. The carbon concentration at the time of charging can be made 2% or less, and as a result, the zinc quality of the crude zinc oxide can be made 65% or more.

  In addition, the carbon concentration at the time of charging into the DRK in the drying and heating process is adjusted such that the crushing strength according to the following definition of the reducing agent-incorporated pellets when charging into the reduction roasting rotary kiln (RRK) is 4200 g or more and 6500 g. Hereinafter, it is preferably granulated so as to be about 6000 g. By optimizing the crushing strength within this range, the effects of the present invention are more stably exhibited. When the crushing strength is significantly lower than 4200 g, the strength required for the pellets is insufficient, and the pellets are gradually broken during the movement in the RRK. As a result, for the same reason as described above, carbon is mixed into the DRK. This is because it may increase, and if it exceeds 6000 g, the strength of the pellet becomes excessive, and the action as a reducing agent may be insufficient.

[Definition of crushing strength]
In the present specification, the crushing strength refers to a value defined below.
Crushing strength: When the reducing agent-incorporated pellet is compressed by a crushing strength measuring device equipped with a spring gauge and a sample setting plate, the measured value (g) of the spring measuring at the time when the reducing agent-incorporated pellet is damaged The crushing strength (g) of the agent-incorporated pellets is used. In addition, in order to ensure the stability of the sample at the time of measurement and perform the measurement stably, for example, the pressure applied to the sample is measured by three spring gauges as the total of the three pressures measured respectively. A three-point indicating type crushing strength measuring device can be preferably used. In this case, the sum of the measured values of the three spring gauges is the crushing strength (g).

  Note that the crushing strength of the reducing agent-incorporated pellets strongly depends on the crushing strength of steel dust or the like as raw material ore. Therefore, pellets having a desired crushing strength can be manufactured by limiting the strength of the steel dust to be selected to a high strength. Also, the desired crushing strength can be obtained by adjusting the aging period after pellet granulation.

<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 employed. In the reduction roasting step S20, the reducing agent-incorporated pellets obtained in the preliminary mixing step S10 are continuously charged into the RRK together with limestone and the like. At this time, in addition to the steel dust A formed as a reducing agent-incorporated pellet, steel dust B having a relatively high zinc volatilization rate may be similarly introduced into the RRK together with a carbonaceous reducing agent such as coke. In this case, the steel dust B is preferably formed into pellets having a size of about 5 to 10 mm in advance as necessary.

  In the RRK furnace, the maximum temperature of the object to be treated is controlled to about 1100 to 1200 ° C. by burning heavy oil and burning the carbonaceous reducing agent. In this furnace, the reducing agent-incorporated pellets containing steel dust A and steel dust B are both reduced and roasted, and the volatilized metallic zinc is reoxidized in the furnace to become powdered zinc oxide. Powdered zinc oxide is introduced into the dust collector together with the exhaust gas from the RRK, captured, and recovered as crude zinc oxide.

  The crude zinc oxide obtained from steel dust by a reduction roasting process generally contains impurities such as halogen group elements of about 8 to 20% by mass. In the reduction roasting step S20 of the present embodiment, it is preferable to adjust the carbon concentration of the crude zinc oxide after the reduction roasting treatment to be less than 2.0% by mass. The carbon concentration of the crude zinc oxide can be reduced to less than 2.0% by adjusting the composition and granulation state of the steel dust and the additive amount of additive such as CaO in view of the air speed in the kiln and the stirring state. . In this example, by adjusting the carbon concentration to be introduced into the subsequent wet process S30 to the above range, the zinc quality that can be preferably used for zinc smelting by the electrolytic smelting method is high quality of 65% by mass or more. The zinc oxide ore can be efficiently produced.

  Incidentally, the reduction roasting residue that remains in the kiln without being volatilized by the above reduction roasting method contains a large amount of reduced iron, and thus is recovered from the kiln discharge end as a product called reduced iron pellets. It is paid out to the manufacturer as an iron raw material.

<Wet process>
Impurities containing halogen group elements such as fluorine and chlorine contained in the crude zinc oxide are separated and extracted in the treatment liquid, and further, impurities are removed from the crude zinc oxide by a water washing method by a solid-liquid separation treatment. The wet process for obtaining the zinc oxide cake can be performed by the process in the following wet process S30.

  The crude zinc oxide recovered from the steel dust in the reduction roasting step S20 is repulped with industrial water or the like. The collection can be performed with an electric dust collector or the like. Moreover, it is not necessary to use an alkaline solution for this repulp. The crude zinc oxide in the slurry is subjected to pH adjustment and aggregation treatment, and then subjected to primary dehydration. The pH is adjusted to a weakly acidic solution of about 6 to 7 to elute cadmium, and the agglomeration uses a flocculant or the like to improve the sedimentation property. After this primary dehydration, it is diluted with industrial water and further subjected to secondary dehydration. It is preferable to reduce the halogen concentration of the zinc oxide cake to less than 0.6% by mass for the fluorine concentration and to less than 1.0% by mass for the chlorine concentration by the washing and dehydration twice.

  In a state where impurities such as fluorine are removed in the treatment liquid, the treatment liquid in which the impurities are distributed is removed from the slurry by solid-liquid separation. Thereby, a crude zinc oxide slurry becomes a higher concentration crude zinc oxide cake. In addition, about the dehydration process for solid-liquid separation, moisture forced dehydration apparatuses, such as gravity sedimentation type slurry concentration apparatuses, such as a thickener, and a vacuum dehydrator can be used.

<Dry heating process>
Zinc oxide ore can be produced while further improving the zinc quality by the drying heating step S40 in which the crude zinc oxide cake obtained in the wet step S30 is put into a heating furnace such as a drying heating rotary kiln (DRK) and baked. .

  In the premixing step S10, which is an upstream step of the entire process, the production method of the present invention is optimized by preliminarily reducing the properties of the reducing agent-incorporated pellets within a predetermined condition range. It is characterized in that the carbon concentration of the resulting crude zinc oxide cake is maintained at 2.0 mass% or less. As described above, the carbon concentration of the crude zinc oxide cake largely depends on the carbon concentration of the carbonaceous reducing agent-incorporated pellets input to the reduction roasting process and the particle size distribution of each powdery material constituting the pellets. By controlling these two factors, the carbon concentration of the crude zinc oxide cake charged into DRK can be maintained within an appropriate range.

  Regarding the firing temperature of the drying heat treatment, it is preferable to maintain and manage the furnace temperature so that the temperature of the object to be fired when discharged from DRK is in the range of 1100 ° C. or higher and 1150 ° C. In the present specification, “fired at 1100 ° C.” means that the fired product is fired in a furnace temperature environment in which the temperature of the fired product at the discharge end of the DRK is 1100 ° C. as described above. Shall.

  Here, when the reducing atmosphere in DRK is strengthened by carbon still remaining in the crude zinc oxide cake, zinc is reduced and volatilized in the exhaust gas, the zinc fixation rate to the product is reduced, and the zinc quality in the zinc oxide ore is descend. Further, the strengthening of the reducing atmosphere in the DRK hinders the volatilization of halogen group elements such as fluorine, which causes a reduction in zinc quality.

  In the method for producing zinc oxide ore according to the present invention, DRK firing is performed within a range of about 1100 ° C. to 1150 ° C., which is a general operation temperature with a low risk of causing a reduction in the operation rate of the rotary kiln. In the premixing step S10, which is the upstream process of the entire system, the carbon concentration of the crude zinc oxide cake fed into the is properly controlled by adjusting the amount of carbonaceous reducing agent added, and thereby the zinc quality A high-quality crude zinc oxide can be stably produced.

<Exhaust gas dust cleaning process>
As the cleaning equipment for performing the exhaust gas dust cleaning step S50 for cleaning the exhaust gas dust generated in the drying and heating step S40 and obtaining the exhaust gas dust cake after cleaning, a combination of a cleaning tower and a wet electrostatic precipitator is common. . In addition, a process for effectively using metal resources has been conventionally performed by repeatedly circulating the exhaust gas dust cake collected by these facilities into upstream processes such as DRK in the drying and heating process S40. .

<Wastewater treatment process>
The wastewater treatment step S60 removes fluorine and cadmium from the waste liquid containing high concentration of fluorine and cadmium separated from the crude zinc oxide in the wet step S30, and further neutralizes heavy metals contained in a small amount in the waste liquid. This is a process of extracting and finally adjusting the pH to be harmless waste water.

  The waste liquid separated in the wet process S30 also contains zinc and / or lead components eluted in a very small amount from the crude zinc oxide. In order to recover the heavy metal component, neutralization is performed as described above. This neutralization treatment is generally performed by adding slaked lime. The addition method of this slaked lime can use the method of adding solid slaked lime directly to a wet processing liquid, the method of adding the solution which melt | dissolved slaked lime in the liquid state, etc. to a wet processing liquid. Moreover, the addition amount of slaked lime can also be adjusted by measuring the pH of the neutralization process liquid after addition.

  The neutralized starch containing the zinc compound or lead compound recovered by this neutralization treatment is repeatedly used in the wet treatment step, wet-treated with the zinc oxide slurry obtained from the reduction roasting step, and DRK. A method of firing and granulating and fixing to zinc oxide ore is generally performed.

<Carbon concentration measurement process>
In the present invention, a carbon concentration measurement step S70 that is a step of measuring the carbon concentration of the crude zinc oxide cake that is put into the drying and heating step S40 is provided as a step between the wet step S30 and the drying and heating step S40. Also good. As a measuring method of carbon concentration, as described above, a measuring method by XRF analysis can be cited as a preferred example. By this carbon concentration measurement step S70, the carbon concentration of the above-mentioned zinc oxide cake is always measured or confirmed at appropriate intervals as needed, and the result is appropriately fed back to the control of the upstream side, so that the above-mentioned The carbon concentration can be controlled with higher accuracy.

  As mentioned above, although embodiment of this invention was described, this invention is not restricted to embodiment mentioned above. The effects described in the embodiments of the present invention are only the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. is not.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.

  According to the production method of the present invention, it is possible to control the carbon concentration of the crude zinc oxide cake to be supplied to the DRK for performing the drying superheating step to 2.0% by mass or less, and thereby oxidation through the drying superheating step. In order to confirm that the zinc grade of zinc ore can be 65% or more, the following tests were conducted.

  As described above, a test in a manufacturing facility capable of performing the entire process including the preliminary mixing step S10, the reduction roasting step S20, the wet step S30, the drying and heating step S40, the exhaust gas dust cleaning step S50, and the wastewater treatment step S60. By the operation, crude zinc oxide was produced. The operation was separately performed using the reducing agent-incorporated pellets of Examples 1 to 3 that satisfy various requirements of the present invention and the reducing agent-incorporated pellets of Comparative Examples 1 to 3 that do not satisfy the same conditions. In addition, the details of the test operation conditions are as follows.

As the raw material ore, steel dust having different particle size distributions was used for each of the reducing agent-incorporated pellets of Examples 1 to 3 and Comparative Example 6. Each particle size distribution is as shown in Table 1. In addition, about the composition of steel dust, what was in all the following ranges was used.
Zn: 20-35% by mass, Pb: 1-3% by mass, Fe: 10-35% by mass, Cr: <0.1% by mass, F: 1.0% by mass, Cd: 1.0% by mass, is there.

  Recycled carbon was used as the carbonaceous reducing agent. Regarding the particle size of the recycled carbon, all particles having a particle size of 50 μm or less were used. The amount of recycled carbon added to the total amount of raw material ore was adjusted as appropriate so that the content ratio of recycled carbon in the reducing agent-incorporated pellets was the content ratio shown in Table 1, respectively.

  And said raw material ore and a carbonaceous reducing agent were mixed and granulated by the pan pelletizer, and it was set as the carbonaceous reducing agent interior pellet with a particle size of 5.4-9.6 mm.

  The carbonaceous reducing agent-incorporated pellets produced in this manner were put into a reduction roasting process to recover crude zinc oxide. Here, regardless of the carbon content of the carbonaceous reducing agent-incorporated pellets to be charged, the RRK operating conditions were all kept constant in the operations using the pellets of any example. About roasting temperature, it was set as the range of 1100-1150 degreeC.

  The crude zinc oxide obtained in the reduction roasting step was further charged into a wet process, and the crude zinc oxide (crude zinc oxide cake) obtained from the wet process was charged into a dry heating step. The baking temperature was 1100 to 1150 ° C., and the drying heat treatment was performed. In addition, in order to grasp the carbon content of the crude zinc oxide (crude zinc oxide cake) charged in the drying and heating process, the carbon content of the crude zinc oxide cake in the stage immediately before the addition to the DRK was measured for each lot. . The carbon content for each example and comparative example is shown in Table 1 as “C quality”.

  After completion of the drying heat treatment, the zinc quality of the product was measured. This zinc quality is a numerical value obtained by analyzing a burned ore obtained through a drying and heating process with an X-ray analyzer. The zinc quality for each example and comparative example is shown in Table 1 as “Zn quality”. From these results, the value of carbon content in the input to DRK is plotted on the horizontal axis, and the zinc grade value of each zinc oxide ore, which is the final product calculated from DRK, is plotted on the vertical axis. FIG. 2 shows a graph showing the above.

  Moreover, the zinc collection | recovery rate from the rough | crude zinc oxide cake in the drying heating process in the case of using the reducing agent interior pellet of Example 1 was calculated | required. This zinc recovery rate is obtained by dividing the amount of zinc in the burned ore produced from DRK by the amount of zinc in the crude zinc oxide cake immediately before being put into DRK. As a result, the zinc recovery rate of Example 1 was 97.6%.

  From Table 1 and FIG. 2, the carbon concentration of the crude zinc oxide (crude zinc oxide cake) to be introduced into the reduction drying heating step is reduced to 2.0 mass% or less by using the reducing agent-incorporated pellets that satisfy the conditions of the present invention. It can be understood that it can be retained, and further, the zinc quality of the zinc oxide ore that has undergone the drying superheating step can be retained at 65.0% or more.

S10 Preliminary 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 Carbon concentration measurement process

Claims (5)

A method for producing zinc oxide ore, which produces zinc oxide ore from powdery raw ore containing zinc,
A premixing step of mixing and granulating raw material ore and a carbonaceous reducing agent to obtain a reducing agent-incorporated pellet;
A reduction roasting step of roasting the reducing agent-incorporated pellets to obtain crude zinc oxide;
A wet process of removing a halogen group element from the crude zinc oxide by a wet treatment to obtain a crude zinc oxide cake;
A drying heating step of baking the crude zinc oxide cake in a drying heating furnace,
The raw material ore used in the premixing step has a particle size distribution with a ratio of 0.5 mm under 10% or less, the carbonaceous reducing agent used in the premixing step has a particle size of 200 μm or less, and The manufacturing method of the zinc oxide ore which makes content ratio of the said carbonaceous reducing agent in the said reducing agent interior pellet 18% or less.   2. The method for producing zinc oxide ore according to claim 1, wherein the raw material ore has a particle size distribution in which a ratio of over 6.7 mm is 50% or more. The drying heating furnace is a drying heating rotary kiln;
Firing by the dry heating rotary kiln is performed at 1100 ° C. or higher and 1150 ° C. or lower,
The method for producing zinc oxide ore according to claim 1 or 2, wherein a zinc recovery rate from the crude zinc oxide cake in the drying and heating step is maintained at 95% or more.   The method for producing zinc oxide ore according to any one of claims 1 to 3, wherein the raw material ore is steel dust.   The method for producing zinc oxide ore according to any one of claims 1 to 4, wherein the carbonaceous reducing agent is recycled carbon.

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