JP6094467B2 - Method for producing zinc oxide ore - Google Patents

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, including a step of volatilizing and separating a fluorine component remaining in the crude zinc oxide by firing the 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, crude zinc oxide derived from steel dust contains impurities such as fluorine at a certain concentration or more in addition to zinc oxide, which is the main component.

  Naturally, the fluorine concentration in the final product zinc is required to be extremely low. Further, in order to use zinc oxide ore as a raw material for zinc smelting by the ISP smelting method or the like, it is necessary to reduce the fluorine concentration of zinc oxide ore to a value allowed in each smelting process.

  In order to reduce the fluorine concentration of zinc oxide ore, as a method of separating and removing fluorine from the reduced zinc oxide after reduction roasting, a method of volatilizing and separating the fluorine component by firing in a dry heating furnace (Patent Document 2). See).

  Here, for example, with respect to zinc oxide ore for electrolytic smelting, the fluorine concentration of zinc oxide ore is reduced to less than 0.05% by mass in order to suppress the progress of corrosion of the aluminum permanent cathode used in the electrowinning process. There is a need to reduce. As a means for performing such high-accuracy separation and removal of fluorine, there is a method of increasing the volatilization rate of fluorine by increasing the temperature in the rotary kiln for performing the above-mentioned firing. However, when the temperature in the 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 high-grade zinc oxide ore production sites, such as zinc oxide ore for electrolytic smelting, in order to remove fluorine with high accuracy, the reduction in operating efficiency of the rotary kiln due to high-temperature operation is tolerated to some extent. However, there is a need for a zinc oxide ore production method that can reduce the fluorine concentration to an extremely low concentration while maintaining the operation efficiency.

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

  The present invention provides a zinc oxide ore that can reduce the fluorine concentration of zinc oxide ore to an extremely low concentration while maintaining the zinc grade of zinc oxide ore and the operating efficiency of the rotary kiln. It aims to provide a method.

  In a total process for producing zinc oxide ore from crude zinc oxide, a material in which a carbonaceous reducing agent such as carbon is incorporated is preferably used as a raw material to be input into the reduction roasting step. The present inventors have found that the above problem can be solved by controlling the amount of carbon derived from the carbonaceous reducing agent in the drying and heating step to a certain amount or less, and have completed the present invention. Specifically, the present invention provides the following.

  (1) A zinc oxide ore production method for producing zinc oxide ore from a powdery raw material ore containing fluorine, wherein the raw material ore and a carbonaceous reducing agent are mixed and granulated to form a reducing agent-incorporated pellet. A pre-mixing step, a reduction roasting step for roasting the reducing agent-incorporated pellets to obtain crude zinc oxide, and a wet process for subjecting the crude zinc oxide to wet treatment to remove the fluorine to obtain a crude zinc oxide cake And a drying heating step of baking the crude zinc oxide cake in a drying heating furnace, and maintaining the carbon concentration of the crude zinc oxide cake charged into the drying heating step at 0.3% by mass or less A method for producing zinc ore.

(2) The content ratio of the carbonaceous reducing agent in the reducing agent-incorporated pellet is 7.5% or less, and the crushing strength according to the following definition of the reducing agent-internal pellet is 4200 g or more and 6500 g or less. The manufacturing method of the zinc oxide ore as described.
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 is reduced. Let it be the crushing strength (g) of the agent-incorporated pellets.

  (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 the fluorine concentration of the zinc oxide ore after the drying heating step is set to 0.05 mass. % Or less, (1) or the manufacturing method of the zinc oxide ore as described in (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 powdered recycled carbon.

  According to the present invention, for example, in a process of producing zinc oxide ore by using a powdery raw material ore containing fluorine such as steel dust as a raw material, followed by a drying and heating step using a rotary kiln, the zinc quality of the zinc oxide ore and the rotary kiln A zinc oxide ore production method that can reduce the fluorine concentration of zinc oxide ore to an extremely low concentration while maintaining preferable operating efficiency can be provided.

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 content of a reducing agent interior pellet, the crushing strength of a pellet, and the carbon input amount to a drying heating process. It is a graph which shows the relationship between the carbon content of a reducing agent interior pellet, and the carbon input amount to a drying heating process. 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 a fluorine volatility.

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

<Overall process>
As shown in FIG. 1, the zinc oxide ore production method of the present embodiment is obtained by mixing and granulating a powdery raw material ore such as steel dust and a carbonaceous reducing agent such as recycled carbon, From the pre-mixing step S10, the reducing agent-incorporated pellets, and the other steel dusts by reduction roasting to obtain crude zinc oxide, the reduction roasting step S20, the crude zinc oxide obtained in the reduction roasting step S20, fluorine Wet process S30 to separate and remove halogen components such as in the treatment liquid to obtain a crude zinc oxide cake, and dry heating process S40 to obtain the zinc oxide ore by drying and heating the crude zinc oxide cake obtained in the wet process S30, This is an overall process including an exhaust gas dust cleaning step S50 for cleaning exhaust gas dust generated in the drying and heating step S40 to obtain a cleaned exhaust gas dust cake, and a waste water treatment step S60.

  The manufacturing method of the zinc oxide ore of the present embodiment pays attention to the carbon concentration of the crude zinc oxide cake put into the dry heating rotary kiln (DRK) in the drying heating step S40, and controls the concentration within a predetermined range. This is because the fluorine concentration of zinc oxide ore is maintained in a very low range. According to this method, the fluorine concentration of zinc oxide ore can be maintained in a very low range while maintaining the zinc quality of zinc oxide ore and the operating efficiency of the rotary kiln. For example, zinc oxide ore having a very low fluorine concentration that can be preferably used as zinc oxide sinter for electrolytic smelting can be produced under high productivity.

<Preliminary mixing process>
Prior to the reduction roasting step S20, the premixing step S10 is a step of mixing and granulating a raw material ore such as steel dust and a carbonaceous reducing agent such as recycled carbon to form a reducing agent-incorporated pellet. is there. 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.

  As the raw ore, various ores containing a valuable metal containing zinc in a ratio of a predetermined amount or more and having a fluorine content to be removed as an impurity of a predetermined amount or less can be used. 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. Below, the case where steel dust is used as a raw ore of crude zinc oxide in the manufacturing method of the zinc oxide ore of this invention is demonstrated.

  When steel dust is used as a raw material ore, there is no particular limitation, and generally steel dust (hereinafter also referred to as “steel dust A”) having high zinc quality and relatively low volatility of zinc under general reduction roasting conditions. There 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.

  As the carbonaceous reducing agent, it is possible to use carbon, recycled carbon, etc., which can be pelletized powder or slurry. Among these, recycled carbon can be preferably used from the viewpoint of promoting resource recycling and reducing costs.

  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. The powder form is not limited to a powder having a specific particle diameter, but powdered recycled carbon having a size of less than about 1 mm can be used very preferably as described above. Hereinafter, in the present specification, a case where powdered recycled carbon is used as a carbonaceous reducing agent used for obtaining a reducing agent-incorporated pellet in the zinc oxide ore production method of the present invention will be described.

  The reducing agent-incorporated pellets produced by mixing and granulating steel dust A and recycled carbon with a pan-type pelletizer have a carbon concentration of 0.3 at the time when they are introduced into the DRK in the drying and heating process after each process. The carbon concentration is adjusted to an appropriate value in advance at the time of mixing granulation so as to be not more than%.

  Specifically, the above adjustment is realized by optimizing both the carbon concentration and the crushing strength of the reducing agent-incorporated pellets when charged into the RRK within the range specific to the present invention defined below. Specifically, the carbon concentration of the reducing agent-incorporated pellets when charged into the RRK is 5.0% or more and 10.0% or less, preferably 5.0% or more and 7.5% or less. . At the same time, the reducing agent-incorporated pellet has a crushing strength of 4200 g or more and 6500 g or less, preferably about 6000 g according to the following definition.

[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 is reduced. Let it be the crushing strength (g) of the agent-incorporated pellets.
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).

  While controlling the carbon concentration and crushing strength of the reducing agent-incorporated pellets so as to be within the above ranges throughout the entire operation period, while enjoying the effect of improving the zinc volatilization rate of steel dust A by adopting the reducing agent-incorporating pellets The fluorine volatilization rate in the drying and heating step can be sufficiently increased. If the carbon concentration of the reducing agent-incorporated pellets is less than 5.0%, the improvement of the zinc oxide reduction rate by pelletization becomes insufficient. Further, even if the carbon concentration exceeds 10.0%, it is not preferable to improve the reduction rate beyond that because it is less desirable than the expected value and the cost performance is lowered. Also, if the crushing strength is less than 4200 g, even if the carbon concentration is 5.0% or more, the crushing strength is insufficient, so the amount of carbon mixed in the drying and heating process increases. If the crushing strength greatly exceeds 6500 g, since the granularity is retained inside the reducing kiln, the zinc volatilization rate becomes low, which is not preferable.

  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.

  Here, FIG. 2 is a graph showing the relationship between the carbon content of the reducing agent-incorporated pellets and the crushing strength of the pellets and the amount of carbon input to the subsequent drying and heating step S40. This measurement was performed by performing XRF analysis on the dried and heated kiln input cake coming out of the wet process S30. FIG. 3 shows the carbon content of the reducing agent-incorporated pellets (recycled carbon ratio at the time of producing the interior pellets) when the crushing strength of the reducing agent-incorporated pellets is limited to 6000 g, and the amount of carbon input to the subsequent drying and heating step S40. It shows the relationship.

  2 and 3, using a reducing agent-incorporated pellet with a high crushing strength of about 6000 g and further reducing the amount of recycled carbon to 7.5% or less, carbon input to the drying and heating step S40 It can be seen that the amount can be controlled to 0.3% or less.

<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 the steel dust by the reduction roasting process generally contains about 8 to 20% by mass of impurities such as halogen. In the reduction roasting step S20 of the present embodiment, it is preferable to adjust so that the fluorine concentration in the crude zinc oxide after the reduction roasting treatment is less than 0.6% by mass. The fluorine concentration in the zinc oxide ore may be made less than 0.6% by mass by sufficiently adjusting the composition and granulation state of steel dust, and the amount of additives such as CaO in consideration of the kiln internal wind speed and stirring state. it can. In this example, the fluorine concentration of the crude zinc oxide to be added to the subsequent wet process S30 is adjusted to the above range, and the processing conditions in each process are set to each range specific to the present invention as will be described in detail later. By adjusting, low halogen zinc oxide ore having a fluorine concentration of less than 0.05% by mass, which can be preferably used for zinc smelting by electrolytic smelting, can be produced more efficiently at lower cost than before. it can.

  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>
The wet treatment for separating and extracting impurities such as fluorine contained in the crude zinc oxide into the treatment liquid and further removing the impurities from the crude zinc oxide by a water washing method by solid-liquid separation treatment to obtain a crude zinc oxide cake, It can carry out 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 enhances the sedimentation property using an aggregating agent or the like. 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 reducing the fluorine concentration by the drying heating step S40 in which the 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. .

  The production method of the present invention is characterized in that the carbon concentration of the crude zinc oxide cake charged into DRK is 0.3% by mass or less. As described above, the carbon concentration of the crude zinc oxide cake depends not only on the carbon concentration of the carbonaceous reducing agent-incorporated pellets that are put into the reduction roasting process but also on the crushing strength of 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, the form of fluorine still remaining in the zinc oxide cake includes a volatile form (for example, lead chlorofluoride (PbFCl)) and a non-volatile form (for example, calcium difluoride (CaF ₂ )). Among these, volatile substances (PbFCl) are almost entirely volatilized by maintaining the temperature of the ore within the above temperature range, and almost all volatile chlorine and fluorine are exhaust gas treatment equipment in the exhaust gas dust cleaning step S50. To be discharged. On the other hand, since the non-volatile substance (CaF ₂ ) is a very stable compound, it does not decompose and volatilize in the DRK and is fixed to the zinc oxide ore.

  In the method for producing zinc oxide ore according to the present invention, the firing with DRK is performed within a range of about 1100 ° C. to 1150 ° C., which is a general operating temperature with a low risk of causing a reduction in the operating efficiency 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 charged into the slag is appropriately controlled by adjusting the amount of carbonaceous reducing agent added. It is possible to stably produce a high-quality crude zinc oxide having a very low fluorine concentration of 0.05% by mass or less, which can be used as a zinc material for use.

  It is considered that the excessive mixing of carbon into DRK inhibits the volatilization of fluorine due to the following reasons. That is, when a reducing agent such as carbon is mixed in the DRK, moisture and oxygen necessary for promoting volatilization of lead in the DRK react preferentially with the reducing agent, and as a result, lead Volatilization is suppressed. On the other hand, in DRK, fluorine tends to exist in the form of PbFCl, and in DRK, it volatilizes in the form of a complex of lead. Therefore, as described above, it is considered that when the volatilization of lead is inhibited, the volatilization rate of fluorine decreases accordingly.

Here, the form of fluorine still remaining in the zinc oxide cake includes a volatile form (for example, lead chlorofluoride (PbFCl)) and a non-volatile form (for example, calcium difluoride (CaF ₂ )). Among these, volatile substances (PbFCl) are almost entirely volatilized by maintaining the temperature of the ore within the above temperature range, and almost all volatile chlorine and fluorine are exhaust gas treatment equipment in the exhaust gas dust cleaning step S50. To be discharged. On the other hand, since the non-volatile substance (CaF ₂ ) is a very stable compound, it does not decompose and volatilize in the DRK and is fixed to the zinc oxide ore.

  In the method for producing zinc oxide ore according to the present invention, the firing with DRK is performed within a range of about 1100 ° C. to 1150 ° C., which is a general operating temperature with a low risk of causing a reduction in the operating efficiency 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 charged into the slag is appropriately controlled by adjusting the amount of carbonaceous reducing agent added. It is possible to stably produce a high-quality crude zinc oxide having a very low fluorine concentration of 0.05% by mass or less, which can be used as a zinc material for use.

<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 a zinc and / or lead component eluted in a trace 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 measuring 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. Is preferred. As a measuring method of carbon concentration, as described above, a measuring method by XRF analysis can be cited as a preferred example. By measuring and confirming the carbon concentration of the Zinc Oxide Cake at an appropriate interval at any time or at any appropriate time by this carbon concentration measuring step S70, the above-mentioned carbon concentration can be increased to 0.3% by mass with higher accuracy. The following range can be controlled.

  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.

  The following test was conducted in order to confirm that setting the carbon concentration of the crude zinc oxide cake to be added to DRK to 0.3% by mass or less contributes to the improvement of the kiln volatility in the drying and heating step.

  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. Depending on the operation, a method for producing crude zinc oxide was carried out. The details of the test operation conditions are as follows.

The following steel dust was used as the raw material ore. The composition of steel dust is as follows.
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.

  In addition, recycled carbon was used as the carbonaceous reducing agent. The amount of recycled carbon added to the total amount of raw material ore was appropriately adjusted so that the carbon content was within the range of 5 to 7.5%. 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.

  For the carbonaceous reducing agent-incorporated pellets, a plurality of types of lots were prepared so that the carbon content of each lot was different. And these carbonaceous reducing agent interior pellets measured each crushing strength beforehand for every lot which has the same composition.

  The carbonaceous reducing agent-incorporated pellets produced in this manner were put into a reduction roasting process to recover crude zinc oxide. Here, the RRK operating conditions were kept constant regardless of the carbon content of the carbonaceous reducing agent-incorporated pellets to be charged. 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. .

  After completion of the drying heat treatment, the volatilization rate of fluorine in the drying heating process was determined. The volatilization rate of fluorine is obtained by dividing the amount of fluorine in the dry heating process output calcined ore by the amount of fluorine in the crude zinc oxide cake charged into the dry heating kiln. And as above-mentioned, the relationship between the carbon content of the crude zinc oxide before DRK addition measured beforehand and the fluorine volatilization rate in the same process was verified. The results are shown in FIG. From FIG. 4, by maintaining the carbon concentration of the crude zinc oxide (crude zinc oxide cake) to be supplied to the drying and heating process at 0.3% by mass or less, the volatilization rate of fluorine in the drying and heating process is stably 90% or more. It can be seen that. In addition, when calculating from an average of 0.25% of the fluorine concentration in the crude zinc oxide cake charged into the drying and heating step, the fluorine concentration in the drying and heating step is set to 90% or more, and the fluorine concentration is 0.05% or less. High quality zinc oxide ore can be produced.

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 (4)

A zinc oxide ore production method for producing zinc oxide ore from powdery raw ore containing fluorine,
A premixing step of mixing and granulating raw material ore and a carbonaceous reducing agent to form 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 subjecting the crude zinc oxide to a wet treatment to remove the fluorine to obtain a crude zinc oxide cake;
A drying and heating step of baking the crude zinc oxide cake in a drying and heating rotary kiln ,
Maintaining the carbon concentration of the crude zinc oxide cake charged into the drying and heating step at 0.3% by mass or less ,
Firing by the dry heating rotary kiln is performed at 1100 ° C. or higher and 1150 ° C. or lower,
The manufacturing method of the zinc oxide ore which maintains the fluorine concentration of the said zinc oxide ore after the said drying heating process at 0.05 mass% or less . The content ratio of the carbonaceous reducing agent in the reducing agent-incorporated pellet is 7.5% or less,
2. The method for producing zinc oxide ore according to claim 1, wherein the crushing strength of the reducing agent-incorporated pellets is 4200 g or more and 6500 g or less.
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 is reduced. Let it be the crushing strength (g) of the agent-incorporated pellets. The method for producing zinc oxide ore according to claim 1 or 2 , wherein the raw material ore is steel dust. The method for producing zinc oxide ore according to any one of claims 1 to 3 , wherein the carbonaceous reducing agent is powdered recycled carbon.

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