JP6098499B2 - 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, which includes a process of volatilizing and recovering a zinc component by a reduction roasting process and maintaining a high zinc recovery rate.

  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 blast furnace, an electric furnace, or the like 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. Moreover, in order to further improve the recovery rate 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).

  The maximum temperature in the rotary kiln performing the reduction roasting process is controlled to about 1050 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 .

  Of course, the final product zinc grade is required to be extremely high. In order to use zinc oxide ore as a raw material for zinc smelting by the ISP smelting method or the like, it is necessary to increase the zinc quality of zinc oxide ore to a value allowed in each smelting process.

  However, in order to further improve the recovery rate of zinc during the reduction roasting treatment, when pelletizing the above materials, even if the type of steel dust and carbon to be pelletized is constant, it is not always necessary In the reduction roasting process, it has been empirically known that a high zinc recovery rate may not be stably maintained.

  In the field of zinc oxide ore production using pellets made of steel dust or carbon as a material, there is a demand for a method of producing zinc oxide ore that can further stably improve the zinc recovery rate in the reduction roasting process. It was.

JP 2008-261005 A

  The present invention provides a zinc oxide that can more stably maintain the zinc recovery rate in the reduction roasting process at a desirable height in a zinc oxide ore production site using pellets made of steel dust, carbon, or the like as a material. It aims at providing the manufacturing method of an ore.

  In a total process for producing zinc oxide ore from crude zinc oxide, pellets, which are a kneaded product of steel dust and a carbonaceous reducing agent such as carbon, are preferably used as raw materials to be input into the reduction roasting step. The present inventors have found that by optimizing the crushing strength of such pellets to be input to the reduction roasting step, the recovery rate of zinc in the reduction roasting step can be stably improved. It came to complete. More specifically, the present invention provides the following.

(1) A zinc oxide ore production method for producing zinc oxide ore from iron and steel dust, a premixing step of kneading the steel dust and a carbonaceous reducing agent to obtain a reducing agent-incorporated pellet, and the reducing agent A reduction roasting step in which interior pellets are subjected to a reduction roasting treatment to obtain crude zinc oxide; a wet step in which wet treatment is applied to the crude zinc oxide to remove a part of fluorine; and a rough oxidation after the wet step A drying heating step of drying and heating the zinc cake. In the preliminary mixing step, the crushing strength of the reducing agent-incorporated pellets is 950 g to 1500 g, and the zinc recovery rate in the reduction roasting step is 95 % Zinc oxide ore production method.
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.

  (2) The method for producing a zinc oxide ore according to (1), wherein aging is continued until the crushing strength of the reducing agent-incorporated pellet reaches 950 g or more, and aging is terminated before the crushing strength exceeds 1500 g.

  (3) A reductant-incorporated pellet comprising a steel dust and a carbonaceous reductant, and having a crushing strength of 950 g or more and 1500 g or less, which is a mixed pellet to be charged into a reduction roasting process as a raw material for zinc oxide ore.

  According to the present invention, in the production of zinc oxide ore using pellets made of steel dust, carbon or the like as a material, the zinc recovery rate in the reduction roasting step can be stably maintained at a desired height. A method for producing the ore 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 an example of transition of the aging period and crushing strength of the pellet used for the manufacturing method of the zinc oxide ore of this invention.

  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 this embodiment is a reduction in which a reducing agent is incorporated by mixing and granulating a powdery raw material ore such as steel dust and a carbonaceous reducing agent such as carbon. Crude oxidation obtained in the pre-mixing step S10 to make the agent-incorporated pellets, the reducing agent-incorporated pellets, and other steel dusts by reduction roasting to obtain crude zinc oxide, the reduction roasting step S20, the reduction roasting step S20 Wet process S30 in which a halogen component such as fluorine is separated and removed from the zinc to obtain a crude zinc oxide cake, and the crude zinc oxide cake obtained in the wet process S30 is dried and heated to obtain zinc oxide ore. This is an overall process including an exhaust gas dust cleaning step S50 for cleaning the exhaust gas dust generated in the heating step S40 and the drying heating step S40 to obtain a cleaned exhaust gas dust cake, and a waste water treatment step S60.

  The method for producing zinc oxide ore of the present embodiment pays attention to the crushing strength of the reducing agent-incorporated pellets produced in the premixing step S10 and put into the reduction roasting rotary kiln (RRK), and the crushing strength falls within a predetermined range. It is characterized in that the method can stably improve the recovery rate of zinc in the reduction roasting step of the reducing agent-incorporated pellets by controlling to the above. According to this method, it is possible to maintain the zinc quality of zinc oxide ore, which is a material ore to be input to zinc smelting, in an extremely high range. For example, a zinc oxide ore with extremely high zinc quality that can be preferably used as a zinc oxide sinter for electrolytic smelting can be produced with 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. This mixing granulation operation, so-called pelletizing S11, can be performed using a generally used pelletizing apparatus. 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 size of the reducing agent-incorporated pellet is preferably about 1 to 20 mm and more preferably about 5 to 10 mm in order to improve the Zn recovery rate in addition to the ease of handling. If the size of the reducing agent-incorporated pellet is less than about 1 mm, there is a problem of carry-over when it is charged into the kiln, and if it exceeds about 20 mm, the Zn recovery rate is deteriorated.

  The moisture content of the reducing agent-incorporated pellet is preferably about 10 to 15% by mass in order to control the particle size in addition to the conditions for granulation.

  As the raw material ore, various raw materials containing valuable metals including zinc in a ratio of a predetermined amount or more and having a fluorine content to be removed as impurities as 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, about the manufacturing method of the zinc oxide ore of this invention, the embodiment in the case of using steel dust as raw ore of crude zinc oxide 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 zinc recovery under general reduction roasting conditions. There may be. For such steel dust A as well, a general steel dust having a relatively high zinc recovery rate (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 recovery rate in the same manner as in the case where the carbonaceous reducing agent is not put in the interior and put into the reduction roasting furnace.

  As the carbonaceous reducing agent, carbon, recycled carbon, etc., which can be pelletized powder or slurry can be used. Among these, recycled carbon can be preferably used from the viewpoint of promoting resource recycling and reducing costs. Below, the case where recycled carbon is used as a carbonaceous reducing agent used in order to obtain a reducing agent interior pellet in the manufacturing method of the zinc oxide ore of this invention is demonstrated.

  As described above, the reducing agent-incorporated pellets produced by mixing and granulating steel dust A and recycled carbon with a pan-type pelletizer have a crushing strength of 950 g to 1500 g, preferably 1000 g to 1100 g. In addition, the crushing strength in this specification shall mean the strength of the pellet 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).

  Here, in general, when the crushing strength of the reducing agent-incorporated pellet is less than 950 g, the pellet is finely broken during transportation to the RRK, and a part of the pellet is scattered, thereby reducing the zinc recovery rate. It is already well known that this is undesirable because it increases the loss of recoverable zinc. From the viewpoint of preventing such excessive destruction and scattering of pellets, it is generally demanded that the crushing strength of the pellets is sufficiently large to exceed 950 g. For example, the crushing strength of reducing agent-incorporated pellets that are widely used at present is at least 950 g or more, and pellets having a crushing strength of about 4000 g to 6000 g, which greatly exceeds 950 g, are also widely used.

  However, if the crushing strength exceeds 1500 g, the proportion of the pellet-like aspect that is maintained as it is in the RRK increases, and this becomes the rate of diffusion of the zinc reduction reaction into the reducing agent-incorporated pellet, and the reduction reaction. It has been found as a unique finding by the inventors of the present invention that the progress is delayed, and in this case as well, the improvement of the recovery rate of zinc is hindered. That is, with respect to the reducing agent-incorporated pellets that are originally more preferable to have a high crushing strength, the crushing strength is intentionally limited to a range of 1500 g or less, which is close to the lower limit side of the usable crushing strength range. Thus, there is a novel point of the present invention in that the recovery rate of zinc can be maintained in a high range of 95% or more.

  For example, the crushing strength of the reducing agent-incorporated pellets can be optimized by, for example, adjusting the period of aging 12 after pelletizing S11 of the reducing agent-incorporating pellets (hereinafter referred to as “aging period”) to an optimum period. Can be realized. Regarding the crushing strength of the reducing agent-incorporated pellets after the pelletizing S11, the crushing strength gradually increases during the aging period immediately after the pelletizing 11, and reaches a peak value when a certain period of time elapses. Furthermore, it has been found that the crushing strength of the reducing agent-incorporated pellets gradually decreases as the aging period continues within the aging period after the peak value has elapsed. Therefore, the aging 12 of the reducing agent-incorporated pellet after pelletizing S11 is continued until the crushing strength reaches 950 g or more, and is finished before the crushing strength exceeds 1500 g. By adjusting the aging period, the crushing strength of the reducing agent-incorporated pellets can be controlled within the optimum range of 950 g to 1500 g.

  FIG. 2 is a graph showing an example of transition of the aging period and crushing strength of pellets used in the method for producing zinc oxide ore of the present invention. As a specific example of the adjustment of the aging period, for example, in the case of a pellet in which a change in crushing strength is seen as shown in FIG. It is preferable to put into the roasting process.

  Note that the carbon concentration of the reducing agent-incorporated pellets charged into the RRK is preferably 5.0% or more and 10.0% or less, and more preferably 5.0% or more and 7.5% or less. By controlling the carbon concentration of the reducing agent-incorporated pellets to be within the above range, the effect of improving the zinc recovery rate of the steel dust A by adopting the reducing agent-incorporating pellets can be enjoyed stably at a high level. it can. 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. Moreover, even if the carbon concentration exceeds 10.0%, it is not preferable because the reduction rate beyond that is not as desirable as the expected value, and the cost performance is lowered.

<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 recovery 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 this 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 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.

  According to the production method of the present invention, high-grade crude zinc oxide can be obtained by stably increasing the zinc recovery rate in this reduction roasting step. Specifically, the zinc recovery rate in this reduction roasting step can be 95% or more. As a result, for example, a high-grade zinc oxide ore that can be preferably used for zinc smelting by electrolytic smelting can be efficiently produced at a lower cost than before. In addition, since the zinc quality in the iron-containing clinker, which is a byproduct, can be reduced, stable production of a high-quality iron-containing clinker is possible.

  In the present specification, “recovery rate of zinc in the reduction roasting process” means that it was volatilized and recovered in the RRK with respect to the amount of zinc component contained in the reducing agent roasted pellets to be charged in the reduction roasting process. The ratio of the amount of zinc component contained in crude zinc oxide. The “recovery rate of zinc in the reduction roasting process” is calculated using a fluorescent X-ray analyzer for the zinc content in the raw steel dust and the zinc content in the iron-containing clinker discharged from the RRK. It can be calculated from the measured and obtained values.

  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, The following processing steps can be performed.

  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. The crude zinc oxide in the slurry is subjected to pH adjustment and aggregation treatment, and then dehydrated. By this washing and dehydration, the halogen concentration of the zinc oxide cake is preferably reduced to less than 0.6% by mass for the fluorine concentration and to less than 1.0% by mass for the chlorine concentration. 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.

<Dry heating process>
While further reducing the concentration of residual impurities such as fluorine by the drying heating step S40 in which the zinc oxide cake obtained in the wet step S30 is charged into a heating furnace such as a drying heating rotary kiln (DRK) and fired and granulated, High quality zinc oxide ore can be obtained.

  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.

<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.

<Zinc recovery rate measurement process>
In the present invention, the zinc recovery rate measurement step S70, which is a step of measuring the zinc recovery rate in the reduction roasting step S20, for example, with equipment that can be measured by the above-described method, is provided as a downstream step of the reduction roasting step S20. Is preferred. By measuring and confirming the zinc recovery rate at an appropriate interval at any time or at any appropriate time by the zinc recovery rate measurement step S70, the zinc recovery rate is within a range of 95% or more with higher accuracy. 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 the crushing strength of the reducing agent-incorporated pellets introduced into the RRK contributes to an improvement in the zinc recovery rate in the reduction roasting step when the crushing strength is 950 g to 1500 g.

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 5.0 to 7.5%. And said raw material ore and a carbonaceous reducing agent were mixed and granulated by the pan pelletizer, and the carbonaceous reducing agent interior pellets with a particle size of 5.4-9.6 mm were produced. And these carbonaceous reducing agent interior pellets measured each crushing strength beforehand for every lot which has the same composition.

  These carbonaceous reducing agent-incorporated pellets were put into an RRK having an inner diameter of 3 m and a length of 30 m to carry out a reduction roasting process. The RRK roasting temperature was in the range of 1050 to 1200 ° C. For the pellets having different crushing strengths, the recovery rate of zinc in this reduction roasting step was measured. The results are shown in Table 1. The zinc recovery rate was calculated from the values obtained by measuring the zinc content in the steel dust and the zinc content in the iron-containing clinker discharged from the RRK, respectively, using a fluorescent X-ray analyzer.

  From the above examples, in the preliminary mixing step, according to the zinc oxide ore production method of the present invention, wherein the crushing strength of the reducing agent-containing pellets is 950 g or more and 1500 g or less, at the same roasting temperature as in the past, The zinc recovery rate is set to 95% or higher, whereby the zinc quality of the crude zinc oxide ore can be improved to 70.0% or higher. Thereby, for example, even if the firing temperature in the subsequent drying superheating step is about 1100 ° C., it is possible to stably obtain an extremely high-grade zinc oxide ore that can be preferably used as a zinc oxide ore for electrolytic smelting. it can. In addition, by setting the zinc recovery rate to 95% or more, the zinc quality in the iron-containing clinker that is a by-product can be reduced to 2% or less, and it can be sold to steel manufacturers as a high-quality product. Advantages are also recognized from the viewpoint of promoting recycling.

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 Zinc recovery rate measurement process

Claims (3)

A zinc oxide ore production method for producing zinc oxide ore from steel dust,
A preliminary mixing step of kneading the steel dust and a carbonaceous reducing agent to obtain a reducing agent-incorporated pellet;
A reduction roasting step for obtaining crude zinc oxide by subjecting the reducing agent-incorporated pellets to reduction roasting;
A wet process of subjecting the crude zinc oxide to a wet treatment to remove a portion of fluorine;
A drying heating step of performing a drying heating treatment on the crude zinc oxide cake after the wet step,
In the preliminary mixing step, the crushing strength of the reducing agent-incorporated pellets is set to 950 g to 1500 g,
A method for producing zinc oxide ore, wherein the zinc recovery rate in the reduction roasting step is 95% or more.
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 a zinc oxide ore according to claim 1, wherein the aging is continued until the crushing strength of the reducing agent-containing pellet reaches 950 g or more, and the aging is terminated before the crushing strength exceeds 1500 g. It is a mixed pellet to be put into the reduction roasting process as a raw material for zinc oxide ore,
Consists of steel dust and carbonaceous reducing agent,
Reducing agent furnished pellet pressure壊強degree is 1500g or less than 950 g.
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. The crushing strength (g) of the agent-containing pellets

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