JP5565354B2 - Method for producing zinc oxide sinter - Google Patents

Description

  The present invention relates to a method for producing zinc oxide sinter, for example, a method for producing zinc oxide sinter having a low content of chlorine, fluorine, and lead from zinc-containing steel dust generated in a steel production process or the like.

  Steel dust generated in the steel manufacturing process contains a relatively large amount of zinc in addition to the iron component. Therefore, conventionally, steel dust is reduced and roasted by a reduction roasting method using a rotary kiln, so-called Wertz method, and zinc contained in the steel dust is reduced and volatilized and recovered as crude zinc oxide. . The crude zinc oxide recovered in this manner contains a considerable amount of halogen such as lead, chlorine and fluorine in addition to the main component zinc oxide. Crude zinc oxide is used as a raw material for zinc refining by electrowinning after zinc oxide sinter, but if the fluorine quality in the electrolyte is high, the aluminum cathode plate will melt and the cathode surface will be porous. As a result, the peelability of the electrodeposited zinc electrodeposited on the cathode surface is significantly reduced. In addition, if the chlorine quality in the electrolyte is high, lead is dissolved from the insoluble lead anode, the lead quality of the electrodeposited zinc is increased, and the lead quality of the final product, electrozinc, is exceeded. Therefore, it is preferable that the content of halogen such as lead, chlorine and fluorine in the crude zinc oxide is low.

  As a method for removing halogens such as lead, chlorine and fluorine from the crude zinc oxide, there is a method in which the recovered crude zinc oxide is directly heated and roasted to volatilize fluorine and volatilize lead as lead chloride. However, according to this method, it is necessary to raise the temperature of the kiln to be heated and roasted to about 1250 ° C., which causes a problem that molten zinc adheres to the refractory material of the kiln, which makes it difficult to operate the kiln. Many.

  Patent Document 1 discloses a zinc oxide sinter having a low fluorine content by removing impurities such as halides by performing wet treatment on the halogen-containing crude zinc oxide, and then charging it in a dry heating furnace. A method of manufacturing is disclosed. Furthermore, in Patent Document 2, as a pretreatment of the step of obtaining zinc oxide sinter from crude zinc oxide, the crude zinc oxide is introduced into a reduction furnace together with limestone and a reducing agent, whereby the fluorine component is reduced or reduced. A method for producing zinc oxide sinter fixed in slag as a calcium / fluorine compound and having a low fluorine content is disclosed. However, the content of fluorine in the zinc oxide sinter obtained by these methods was not sufficiently low as a raw material used in the ISP method (zinc / lead simultaneous smelting method). In the ISP method, when zinc oxide sinter having a high fluorine content is used, the generated fluorine causes a decrease in the condenser efficiency of zinc vapor or the quality of the recovered zinc metal.

Japanese Patent No. 45006017 JP 2002-326814 A

  By the way, dust is discharged when the crude zinc oxide is dried and fired. Further, when halogen is removed from the crude zinc oxide, a waste liquid containing halogen is generated. The dust contains a certain amount of zinc and lead, and the waste water contains a small amount of zinc and lead. Conventionally, these dusts have been extracted, stored, and then treated. Therefore, much labor and cost are required for storage and processing.

  The present invention has been made in view of such circumstances, and a first object is to provide a low content of chlorine, fluorine, and lead from zinc-containing steel dust generated in, for example, a steel manufacturing process, and electrolytic refining. A zinc oxide sinter suitable for the manufacturing method, and the second object is to efficiently extract zinc and lead from dust and wastewater-treated starch containing zinc and lead generated in the process, It is providing the manufacturing method of the zinc oxide sinter which can be collect | recovered.

  The present invention specifically provides the following.

  (1) A reduction roasting step of reducing steel dust containing zinc using a reducing agent in a reduction roasting furnace, and a wet refining process for subjecting the crude zinc oxide obtained in the reduction roasting step to a wet process. A first solid-liquid separation step of separating the slurry of the crude zinc oxide that has undergone the step, the wet refining step into a crude zinc oxide cake and a separated liquid, and the crude solid separated in the first solid-liquid separation step In a method for producing a zinc oxide sinter comprising a dehydration treatment step of dehydrating a zinc oxide cake, and a firing treatment step of firing the crude zinc oxide cake obtained in the dehydration treatment step in a drying heating furnace, A cleaning step for cleaning the dust discharged from the drying heating furnace in the baking treatment step, a second solid-liquid separation step for separating the dust that has passed through the cleaning step into a dust slurry and a supernatant, and the first Dust separated in the solid-liquid separation step 2 A deleading step for removing lead from the rally; a supernatant separated in the second solid-liquid separation step; and a defluorination step for removing fluorine from the filtrate obtained in the deleading step; A wastewater-treated starch obtained by subjecting the fluorine starch obtained in the defluorination step and the separation liquid separated in the first solid-liquid separation step to wastewater treatment, A method for producing a zinc oxide sinter characterized by treating in a reduction roasting furnace in the reduction roasting step and fixing fluorine in a reduction residue or reduction slag.

  (2) In the said baking treatment process, the manufacturing method of the zinc oxide calcination as described in (1) which makes the temperature in a drying heating furnace in the range of 900-1150 degreeC.

  (3) In the said deleading process, the manufacturing method of the zinc oxide calcination as described in (1) or (2) which adds sulfuric acid to dust slurry and makes pH in the range of 2-3.

  (4) The defluorination step is neutralized by adding a calcium compound to a mixed solution of the supernatant liquid separated in the second solid-liquid separation step and the filtrate obtained in the deleading step. After the treatment, a first defluorination step for solid-liquid separation, and a metal-based inorganic flocculant is added to the filtrate obtained in the first defluorination step for aggregation treatment, followed by solid-liquid separation. The method for producing a zinc oxide sinter according to any one of (1) to (3), comprising two defluorination steps.

  According to the present invention, it is possible to obtain a zinc oxide sinter having a low content of chlorine, fluorine and lead and suitable for electrolytic refining. Moreover, according to this invention, zinc and lead can be efficiently taken out and collected from dust and wastewater treatment starch containing zinc and lead generated during the process. Furthermore, according to the present invention, much labor and cost for storing and processing dust, which has been conventionally required, can be eliminated.

It is process drawing which shows the manufacturing method of the zinc oxide calcination which concerns on one Embodiment of this invention.

  Hereinafter, the manufacturing method of the zinc oxide sinter of this invention is demonstrated, referring drawings. FIG. 1 is a process diagram showing a method for producing zinc oxide sinter according to one embodiment of the present invention.

[Reduction roasting process]
The reduction roasting step is a step of reducing steel dust containing zinc using a reducing agent in a reduction roasting furnace. Here, steel dust refers to smoke ash generated in, for example, a steel manufacturing process. As the reduction roasting furnace, for example, a rotary kiln utilizing a solid-gas reaction is suitable. The reducing agent is not particularly limited, and examples thereof include coke and coal. If necessary, the reduction roasting furnace may be charged with a solvent such as limestone or meteorite. In the reduction roasting furnace, zinc and lead contained in the steel dust are volatilized and introduced into the dust collector together with the exhaust gas, where they are recovered as crude zinc oxide. Halogens other than fluorine contained in steel dust are mixed in crude zinc oxide, but most of fluorine is calcium fluoride, which is fixed in the reductant residue and reducing slag discharged from the reduction roasting furnace. , Can be discharged out of the system. Thereby, it is possible to reduce fluorine in the crude zinc oxide that is volatilized and recovered in the rotary kiln.

[Wet refining process]
The wet refining step is a step of subjecting the crude zinc oxide obtained in the reduction roasting step to a wet process. The crude zinc oxide recovered in the reduction roasting step contains a considerable amount of chlorine as a chloride compound. Fluorine is also included as a fluorine compound. In the wet refining process, crude zinc oxide is repulped with repulp water, and chlorine and fluorine in the crude zinc oxide are removed using a chemical such as sodium carbonate or sodium hydroxide. According to this wet refining process, in order to remove fluorine and the like from the crude zinc oxide, it is not necessary to raise the temperature in the drying heating furnace to about 1250 ° C. in the baking treatment process described later, and the refractory material of the drying heating furnace There is a possibility that the operation of the furnace becomes difficult due to the problem of adhesion of molten zinc.

[First solid-liquid separation step]
A 1st solid-liquid separation process is a process of isolate | separating the slurry of the rough | crude zinc oxide which passed through the said wet refining process into a rough | crude zinc oxide cake and a separation liquid. As the solid-liquid separator, a thickener, a calocon, or the like can be used. The separation liquid contains not only chlorine compounds and fluorine compounds removed in the wet purification process, but also trace amounts of zinc and lead. In the present invention, the separated separation liquid is subjected to wastewater treatment, and the obtained wastewater-treated starch is charged into the reduction roasting furnace in the reduction roasting step, which will be described in detail later. .

[Dehydration process]
The dehydration process is a process of dehydrating the crude zinc oxide cake separated in the first solid-liquid separation process. By subjecting the crude zinc oxide cake to a dehydration treatment, it is possible to reduce the amount of heat when the moisture in the crude zinc oxide cake is evaporated in a dry heating furnace in the next baking step. As the dehydrating device, for example, a compression dehydrator, a vacuum suction dehydrator, a belt dehydrator, or the like can be used.

[Baking process]
The firing treatment step is a step of firing the crude zinc oxide cake obtained in the dehydration treatment step in a dry heating furnace. In the baking treatment step, the temperature in the drying heating furnace is preferably set in the range of 900 to 1150 ° C. If it is in the above-mentioned range, when zinc is melted in the dry heating furnace, the problem of adhering and growing on the refractory material does not occur, and the situation where the operation of the furnace becomes difficult can be avoided. In the present invention, since chlorine and fluorine in the crude zinc oxide are previously removed in the wet refining step, it is not necessary to raise the temperature in the dry heating furnace to about 1250 ° C. in order to remove these.

  In the baking process, dust is generated in a drying heating furnace. The dust contains a certain amount of zinc or lead. Traditionally, these have been extracted, stored and processed. In the present invention, the dust is not extracted and processed separately, but is subjected to the following steps, and then charged into the reduction roasting furnace in the reduction roasting step. The details will be described later. .

[Washing process]
The cleaning process is a process of cleaning the dust discharged from the drying heating furnace in the baking process. Specifically, the dust is repulped with repulp water. In addition, it is preferable that the pH of repulp water exists in the range of 8-9.

[Second solid-liquid separation step]
A 2nd solid-liquid separation process is a process of isolate | separating the dust which passed through the said washing | cleaning process into a dust slurry and a supernatant liquid. As the solid-liquid separator, a thickener, a calocon, or the like can be used.

[Deleading process]
The lead removal step is a step of recovering lead from the dust slurry separated in the second solid-liquid separation step. The dust generated in the firing process includes a large amount of lead. However, conventionally, dust has always been extracted and stored and then processed. The present invention is significant in that it eliminates the labor and cost required for storage and reprocessing by taking out lead contained in dust in a form that can be used effectively. The method for removing lead from the dust slurry is not particularly limited, but a method of adding sulfuric acid to the dust slurry to bring the pH into a range of 2 to 3 is preferable. According to this method, lead in the dust slurry can be recovered as lead sulfate. In addition, the fluorine removal rate in the defluorination step described later can be improved, and the running cost can be reduced.

[Defluorination process]
The defluorination step is a step of removing fluorine from the supernatant liquid separated in the second solid-liquid separation step and the filtrate obtained in the deleading step. The defluorination step is not particularly limited, but preferably comprises the following first defluorination step and second defluorination step.

<First defluorination step>
In the first defluorination step, neutralization is performed by adding a calcium compound to a mixed solution of the supernatant separated in the second solid-liquid separation step and the filtrate obtained in the deleading step. After the treatment, solid-liquid separation is performed. Examples of calcium compounds include calcium hydroxide and calcium chloride, and these can be used alone or in combination. In the first defluorination step, fluorine is solidified and removed. Specifically, calcium fluoride is precipitated by adding calcium ions to the mixed solution containing fluorine. The addition amount of the calcium compound is appropriately adjusted according to the fluorine concentration in the mixed solution. Specifically, it is added so that the pH of the mixed solution is around 6.

<Second defluorination step>
In the second defluorination step, a metal-based inorganic flocculant is added to the filtrate obtained in the first defluorination step to perform an aggregation treatment, followed by solid-liquid separation. Examples of the metal-based inorganic flocculant include PAC (polyaluminum chloride). In the second defluorination step, the fluorine remaining without crystallization in the first defluorination step is aggregated.

  In the method for producing zinc oxide sinter according to the present invention, the fluorine starch obtained in the defluorination step and the separation liquid separated in the first solid-liquid separation step are subjected to waste water treatment. The obtained wastewater-treated starch is treated in a reduction roasting furnace in the reduction roasting step, and fluorine is fixed in the reduction residue or reduction slag. According to this, the dust discharged from the drying heating furnace in the baking treatment step, the fluorine starch obtained in the defluorination step, and the separated liquid separated in the first solid-liquid separation step. It becomes unnecessary to store and treat wastewater-treated starch obtained by performing wastewater treatment.

  Note that the present invention is not limited to the above-described embodiment, and modifications and improvements are included in the present invention as long as the object of the present invention can be achieved.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention does not receive a restriction | limiting at all in these description.

<Test Example 1>
As test materials, steel dust, which is smoke ash generated in a steelmaking furnace in the steel manufacturing process, was used. The steel dust was analyzed by ICP emission spectroscopy (ICP-AES), and the composition shown in Table 1 was obtained.

(1) Reduction roasting process The steel dust was charged together with coke and limestone into a rotary kiln equipped with a heavy oil combustion burner on the discharge end side with an inner diameter of 3.5 m and a length of 50 m. Coke was added so that it might become about 18 mass% with respect to steel dust, and limestone was added so that it might become about 7.5 mass% with respect to steel dust. Then, the volatilized zinc and lead were introduced into the dust collector together with the exhaust gas, and recovered as crude zinc oxide.

(2) Wet refining process The crude zinc oxide collect | recovered above was repulped with the repulp water, impurities, such as chlorine, were removed using sodium carbonate, and the crude zinc oxide slurry was obtained. The amount of sodium carbonate added was controlled by pH. The pH was adjusted to 6.5. The crude zinc oxide slurry concentration after repulping was adjusted to 200 g / L.

(3) 1st solid-liquid separation process The crude zinc oxide slurry obtained above was isolate | separated into the crude zinc oxide cake and the separation liquid using the thickener. The separation liquid was subjected to wastewater treatment to obtain wastewater-treated starch.

(4) Dehydration treatment step The crude zinc oxide cake separated as described above was made into a crude zinc oxide cake having a water content of 40% by mass or less using a compression-type dehydrator.

(5) Firing treatment step The crude zinc oxide cake dehydrated above was baked in a drying heating furnace at 1150 ° C.

(6) Washing process The dust discharged from the drying heating furnace in the baking process was repulped with repulp water.

(7) 2nd solid-liquid separation process The dust which passed through the said washing | cleaning process was isolate | separated into the dust slurry and the supernatant liquid using the thickener. Table 2 shows the grades of zinc, lead, chlorine, and fluorine of the separated dust slurry.

(8) Delead process The sulfuric acid was added to the dust slurry isolate | separated at the said 2nd solid-liquid separation process, and pH was adjusted to 2. Table 3 shows the quality of the obtained starch.

  As shown in Table 3, starch with high lead quality could be obtained. The main component contained in the starch was lead sulfate.

(9) Defluorination step (9-1) First defluorination step A mixture of the supernatant liquid separated in the second solid-liquid separation step and the filtrate obtained in the deleading step ( After adding calcium hydroxide to a fluorine concentration (1000 ppm), it was separated into a fluorine starch (calcium fluoride) and a filtrate using a thickener. The amount of calcium hydroxide added was controlled by the fluorine concentration of the mixed solution.

(9-2) Second Defluorination Step After adding 50 mg / L of PAC (polyaluminum chloride) to the filtrate obtained in the first defluorination step, a thickener is used to obtain a fluorine starch (fluoride). Aluminum fluoride) and the filtrate.

  Obtained by subjecting the fluorine starch obtained in the first defluorination step and the second defluorination step and the separated liquid separated in the first solid-liquid separation step to drainage treatment. The wastewater-treated starch was charged into the rotary kiln in the reduction roasting step together with the steel dust, coke and limestone having the grades shown in Table 1 above. Coke was added so that it might become about 18 mass% with respect to steel dust, and limestone was added so that it might become about 6.8 mass% with respect to steel dust. And the volatilized zinc and lead were introduced into the dust collector together with the exhaust gas, and the processes of the above (2) to (5) were performed using the recovered crude zinc oxide.

  And the zinc oxide sinter obtained through the baking process of said (5) was analyzed by ICP emission spectroscopic analysis (ICP-AES). The results are shown in Table 4.

  As shown in Table 4, zinc oxide sinter with low grades of chlorine, fluorine and lead could be obtained.

  From the above results, it has been clarified that according to the method for producing a zinc oxide sinter according to the present invention, a zinc oxide sinter having a low grade of chlorine, fluorine and lead and suitable for electrolytic refining can be obtained. Further, according to the method for producing zinc oxide sinter of the present invention, it is also clear that zinc and lead can be efficiently taken out and recovered from dust and wastewater-treated starch containing zinc and lead generated during the process. It became.

Claims (4)

A reduction roasting step of reducing steel dust containing zinc using a reducing agent in a reduction roasting furnace;
A wet refining step for performing a wet treatment on the crude zinc oxide obtained in the reduction roasting step;
A first solid-liquid separation step of separating the crude zinc oxide slurry that has undergone the wet purification step into a crude zinc oxide cake and a separation liquid;
A dehydration step of dehydrating the crude zinc oxide cake separated in the first solid-liquid separation step;
In the method for producing zinc oxide sinter, including a firing treatment step of firing the crude zinc oxide cake obtained in the dehydration treatment step in a dry heating furnace,
A cleaning step of cleaning dust discharged from the drying heating furnace in the baking treatment step;
A second solid-liquid separation step of separating the dust subjected to the washing step into a dust slurry and a supernatant;
A deleading step of removing lead from the dust slurry separated in the second solid-liquid separation step;
A defluorination step of removing fluorine from the supernatant separated in the second solid-liquid separation step and the filtrate obtained in the deleading step;
Waste water treatment starch obtained by subjecting the fluorine starch obtained in the defluorination step and the separated liquid separated in the first solid-liquid separation step to waste water treatment, the reduced roasting A method for producing a zinc oxide calcined ore characterized by treating in a reduction roasting furnace in a process and fixing fluorine in a reduction residue or reduction slag.   2. The method for producing a zinc oxide sinter according to claim 1, wherein in the firing treatment step, the temperature in the drying heating furnace is set within a range of 900 to 1150 ° C. 3.   3. The method for producing zinc oxide sinter according to claim 1, wherein in the deleading step, sulfuric acid is added to the dust slurry to make the pH within a range of 2 to 3. In the defluorination step, a calcium compound is added to the mixed solution of the supernatant liquid separated in the second solid-liquid separation step and the filtrate obtained in the deleading step, and then neutralized. A first defluorination step for solid-liquid separation;
4. A second defluorination step comprising solid-liquid separation after adding a metal-based inorganic flocculant to the filtrate obtained in the first defluorination step and subjecting it to a coagulation treatment. The manufacturing method of the zinc oxide sinter described in 2.

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