JPH07116530B2 - Method for melt desulfurization of zinc sulfide concentrate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a smelting method using zinc sulfide concentrate.

[Prior Art] A method for obtaining metallic zinc from a zinc sulfide concentrate is roughly classified into a wet method and a dry method.

In the wet method, the calcined ore obtained by roasting a sulfide concentrate is dissolved in sulfuric acid to obtain a zinc sulfate solution, and electrolytic zinc is obtained by electrolysis after performing a cleaning solution such as deironization. It is obtained by melting in a furnace to obtain metallic zinc.

In the dry method, a roasted ore and 40 to 60% by weight of reducing coal are mixed, and this is charged into a horizontal retort to heat the retort from the outside to reduce and volatilize zinc and condense it with a horizontal condenser. Distillation method, kneading roasted ore and pulverized coal and coke into a briquette, and heating the briquette in a carbonization furnace to form coke into a vertical externally heated retort while continuously heating it. A vertical distillation method in which zinc is supplied to reduce and volatilize zinc and to condense it with a condenser provided in the upper part of the retort, or a mixture of calcined ore and coke powder to sinter to obtain sinter ore and coke powder It is charged in a cylindrical furnace, and electricity is supplied from the electrodes installed above and below the furnace, and the mixed raw material itself is subjected to electric resistance heating as a low antibody to reduce it by distillation, or as a pretreatment, sulfide concentrate. Is mixed with an appropriate amount of solvent, oxidatively sintered and desulfurized to obtain a sintered mass. Charge the blast furnace with the course,
It is heated and reduced in a blast furnace to volatilize zinc, splash molten zinc in this zinc vapor to capture zinc as a lead-zinc alloy, and then cool this to separate the zinc melt by the difference in solubility, and if necessary refine it. There is the ISP method of staying to obtain metallic zinc.

Among these dry methods, the ISP method is widely adopted because it can be simultaneously smelted with zinc and lead, has high productivity, and has a large allowable amount for impurities.

[Problems to be solved by the invention] However, if the roasting temperature is too high to accelerate the oxidation in the desulfurization step, which is the pretreatment of the ISP method, a part of the raw material is melted and fused to the melting equipment. However, there is a problem that it becomes difficult to discharge the fired product from the equipment, and in the worst case, the operation must be stopped. Further, the melting of a part of the raw materials causes the particles to agglomerate to reduce the surface area of the reaction particles, so that the roasting temperature must be set to 1100 ° C. or less, and there is a problem that the desulfurization rate becomes slow.

And, even if the roasting temperature is 1100 ° C or lower, in order to prevent the particles from agglomerating, it is necessary to constantly circulate about 4 times the amount of the recycle powder of the raw material to be put into the sintering machine in the process. There is a problem. Further, if the roasting temperature becomes low, there is a problem that the heat of oxidation generated in the desulfurization reaction cannot be effectively utilized.

Therefore, an object of the present invention is to provide a desulfurization method having a high desulfurization rate and high thermal efficiency.

[Means for Solving the Problem] As a result of various investigations by the present inventors, if molten slag is made of oxides such as iron and zinc generated by desulfurization reaction and gangue components such as SiO ₂ , heat transfer The inventors have found that the speed and mass transfer rate, particularly oxygen transfer rate, are extremely fast, and that a desulfurization rate higher than that of roasting can be obtained, and the present invention has been completed.

That is, the melt desulfurization method of the present invention, a raw material mainly containing zinc sulfide and a flux, industrial oxygen, oxygen-enriched air,
By reacting with any one of the air, a part of the zinc in the raw material is recovered as a smoke ash mainly composed of zinc oxide, the remaining zinc is recovered as a molten slag, at this time, the molten slag,
It is maintained at a temperature of 1200 ° C or higher, contains iron oxide and silicic acid, and has a sulfur grade of 0.3 to 15% by weight (hereinafter referred to as%).

In the melt desulfurization method of the present invention, auxiliary fuels such as heavy oil, pulverized coal and coke can be used together with the raw material and the flux, if necessary.

Further, in the melt desulfurization method of the present invention, the distribution ratio of zinc in the raw material to the smoke ash and the slag can be adjusted by adjusting the amount of oxygen supplied to the raw material and / or the amount of added flux. Then, preferably, 5 to 95% of zinc in the raw material is recovered as smoke ash, and the rest is recovered as molten slag.

[Operation] In the present invention, ZnS in the raw material reacts with oxygen to generate ZnO particles and SO ₂ according to the formula.

ZnS (s) + 3 / 2O ₂ (g) → ZnO (s) + SO ₂ (g) The rate of this reaction increases significantly above 1200 ° C. Therefore, the reaction temperature and the slag temperature are adjusted to 1200 ° C or higher by adjusting the degree of oxygen enrichment and / or the amount of auxiliary fuel added.

As described above, the molten slag of the present invention contains iron oxide and silicic acid, but the molten slag is iron oxide produced from iron contained in the raw material at about 10%, and SiO ₂ which is the main component of gangue. And flux.

The composition of the molten slag, an FeO-Fe ₂ O ₃ -SiO ₂ based slag is intended to be basic, then add CaO as slag components as required, lowering the melting point.

The components of the molten slag will be described below.

Although Fe in the concentrate usually exists as FlS, this FeS is extremely reactive and is rapidly oxidized to iron oxides of various valences. Among these iron oxides, Fe ₃ O ₄ has a high melting point and is likely to precipitate. The precipitation of Fe ₃ O ₄ causes the bottom of the furnace to rise, and eventually operation becomes impossible. In order to prevent this, it is necessary to reduce the Fe ₃ O ₄ grade in the molten slag as much as possible.

The present invention is based on the results of research on the relationship between the quality of Fe ₃ O ₄ in the molten slag and the properties of the molten slag.

FIG. 1 shows the results obtained by investigating the relationship between the Fe ₃ O ₄ grade and the S grade in the slag produced by the method of the present invention. In FIG. 1, the vertical axis represents the Fe ₃ O ₄ content in the molten slag, and the horizontal axis represents the S content in the molten slag.

According to FIG. 1, it is understood that the Fe ₃ O ₄ quality sharply increases when the S quality becomes 0.3% or less.

From this result, it can be seen that the S grade in the molten slag needs to be 0.3% or more in order to prevent the precipitation of Fe ₃ O ₄ . The upper limit of the solubility of S in this molten slag is about 15%. Therefore, in the present invention, the sulfur content in the molten slag is 0.3 to 15% by weight.

ZnO particles generated by the formula are absorbed by this molten slag,
It becomes a melt. If the amount of oxygen that reacts with the raw material is small, ZnS
Part of the ZnO is decomposed according to the formula to generate Zn vapor, and this vapor is generated by free air leaking in the gas treatment facility or by supplying free air to the ZnO according to the formula.
It becomes particles and is collected as smoke ash.

ZnS (s) → Zn (g) + 1 / 2S ₂ (g) Zn (g) + 1 / 2O ₂ (g) → ZnO (s) Therefore, it is easy to change the amount of oxygen supplied to the concentrate in the raw material. The distribution ratio of Zn to smoke ash can be adjusted.

However, even if the amount of oxygen supplied is set to 0, a part of the generated Zn vapor becomes ZnS by the inverse reaction of the formula and is taken into the slag, so it is difficult to make the distribution ratio of Zn to the smoke ash 100%.

Conversely, even if a large excess of oxygen is supplied, and ZnS particles in the raw material are all ZnO particles, absorption into the slag cannot be completed in time, and some ZnO particles are scattered as smoke ash, It is also difficult to set the distribution rate of Zn to 100%. Needless to say, the distribution ratio of Zn to the smoke ash can be adjusted by adjusting the amount of slag.

When applying the present invention, how much the distribution rate of Zn to the smoke ash depends on the operation mode of the smelter performing the melt desulfurization method, so the total energy cost of the smelter is minimized. It is preferable to select

The apparatus used for carrying out the present invention may be any apparatus to which the self-smelting smelting method or the bath smelting method can be applied. When the method of the present invention is carried out using such a device, the time required to complete the reaction of the formula is 1
It is about a second, which is much faster than when using a conventional sintering machine.

The smoke ash obtained by the method of the present invention can be directly supplied to the next step, the briquetting step. In addition, Zn in slag can be easily recovered by the commonly used slag fuming method, but considering that this slag fuming method requires a considerably high temperature, slag at a temperature of 1200 ° C or higher is used. The method of the present invention for obtaining is very energetically advantageous.

[Example-1] In this example, the method of the present invention was applied to a test smelting furnace of a self-smelting and refining system.

As shown in FIG. 2, this test smelting furnace is composed of a shaft 10 having a height of 4 m and an inner diameter of 1.5 m, and a settler 20 having a length of 5.25 m and an inner diameter of 1.5 m. Mining chute
An oxygen / fuel burner 14 provided with 12 is provided, one end of a settler 20 is connected to the shaft 10, and a waste flue 22 is provided at the other end.

Using the test smelting furnace shown in FIG. 2 and using the raw materials having the compositions shown in Table 1, test operation was carried out under the conditions of Case-1 and Case-2 shown in Table 2. The results are shown in Table 3 as Case-1 and Case-2.
It was shown to.

Comparing Case-1 and Case-2, it can be seen that as the total flux rate (Table 2) increases, the Zn volatilization rate (Table 3) decreases. From this, it can be seen that the total flux rate may be decreased in order to increase the distribution rate of Zn to the smoke ash, and the total flux rate may be increased in order to decrease it.

[Example-2] In this example, the method of the present invention was applied to a bath smelting type test smelting furnace.

As shown in FIG. 3, this test smelting furnace is provided with a blowing lance 16 and a blowing tank 18 in place of the second oxygen / fuel burner 14, and an oxygen / fuel burner 24 on the side wall.
The structure is the same as that of the example 1 except that the height of the shaft 10 is 2.8 m. In this test smelting furnace, a test operation was performed in which the raw material having the composition shown in Table 1 was blown into the slag layer in the furnace from the lance 16 together with the air for sending and oxygen (industrial oxygen having a purity of 90%). went.

The conditions in the test operation are shown in Case-3 and Case-4 of Table 2, and the results are shown in Case-3 and Case-4 of Table 3.

When Case-3 and Case-4 in Table 3 are compared, the same results as in Example-1 are obtained in the bass smelting.

[Example-3] Using the same test kneading furnace as in Example-2, Case- in Table 2 was used.
According to the conditions shown in FIG. 5, the raw material having the composition shown in Table 1 was blown into the slag layer in the furnace together with the air for the sending operation. The purpose of this example is to supply by air only oxygen necessary for oxidizing a part of FeS in the Zn concentrate. According to this condition, most of ZnS should decompose according to the formula. The obtained average results for 3 days are shown in Case 5 in Table 3.

In case-5 of Table 3, S grade in slag is 12.9.
%, But in terms of spot, maximum S quality of 15.0% is obtained. In addition, the volatility of Zn is as high as 71.8%.

As a result, in order to recover Zn as smoke ash, it is understood that the amount of reactive oxygen is limited and the total flux rate is lowered.

[Example-4] A test operation was performed under the same conditions as in Example-3 except that 400 Nm ³ / h of air was blown onto the slag surface in the settler 20. The operating conditions are shown in Case 6 of Table 2 and the obtained results are shown in Table 3 of Ca.
It is shown in se-6. From the results of Case-6 in Table 3, it can be seen that the S grade in the slag was lowered, Zn was volatilized and removed from the slag, and the Zn grade in the slag was also lowered. As a result, the volatilization rate of Zn and the smoke ash generation rate are higher than the values of Case-5. This blows air on the slag surface,
This is because the amount of oxygen that reacts with Zn on the slag surface is increased.

Therefore, it can be said that the distribution ratio of Zn to the smoke ash can be adjusted by increasing or decreasing oxygen.

[Effects of the Invention] In the method of the present invention, the oxides such as iron and zinc produced by the desulfurization reaction and the gangue components such as SiO ₂ are constituted as the molten slag, and the raw material is blown into the molten slag, so that the flow rate is The heat of desulfurization reaction can be effectively used in the reduction step because the temperature is extremely fast and the product temperature is high. Furthermore, it is possible to distribute Zn to smoke ash and slag at any ratio.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between Fe ₃ O ₄ grade and S grade in slag produced by the method of the present invention. FIG. 2 is a schematic cross-sectional view of a test smelting furnace of a self-smelting and smelting system used in an example of the present invention. FIG. 3 is a schematic cross-sectional view of a bath smelting type test smelting furnace used in the embodiment of the present invention. In the figure, reference numerals indicate the following elements. 10: Shaft 12: Concentrate chute 14: Oxygen / fuel burner 16: Injection lance 18: Injection tank 20: Settler 22: Waste flue 24: Oxygen / fuel burner

Claims (3)

[Claims] 1. In a desulfurization step of a zinc smelting method for desulfurizing, reducing and purifying a raw material mainly composed of zinc sulfide, a raw material mainly composed of zinc sulfide and a flux are mixed with industrial oxygen, Oxygen-enriched air, reacted with any one of the air, a portion of the zinc in the raw material is recovered as a smoke ash mainly consisting of zinc oxide, the balance zinc is recovered as a molten slag, at this time, the molten slag is 1200 It is maintained at a temperature of ℃ or higher, contains iron oxide and silicic acid, and has a sulfur content of 0.3-1.
A method for melt desulfurization of zinc sulfide concentrate, characterized in that the content is 5% by weight. 2. The method for melting desulfurization of zinc sulfide concentrate according to claim 1, wherein at least one of heavy oil, pulverized coal and coke is added to the raw material and the flux. 3. The distribution ratio of zinc in the raw material between the smoke ash and the slag is adjusted by adjusting the amount of oxygen and / or the amount of flux supplied to the raw material. Method for melt desulfurization of zinc sulfide concentrates.