JPH06271954A - Operation of reduction furnace for smelting zinc and/or lead - Google Patents

Abstract

PURPOSE:To promote the slag formation of ash content in the settled coke and to prevent the production of metallic iron with unburning carbon by blowing a gas into the slag in a settler of a reduction furnace for smelting zinc or lead through a lance with its tip part dipped into the slag. CONSTITUTION:In the reduction furnace for smelting the zinc and/or the lead composed of a shaft 1, settler 2 and uptake 3, powdery coke, oxygen and raw material are supplied from each of charging holes 7-9, and the raw materials are reduced with a reducing gas produced by oxidation of coke to recover the zinc, lead, etc., as their metallic vapor. In the operation method of reduction furnace, one or more kinds of nitrogen, air, oxygen-enriched air and industrial oxygen are blown into the slag in the settler 2 through the lance 6 arranged at a setter roof and dipped into the slag 4 at its tip part. By this method, the molten slag is intensely stirred with a little quantity of the gas, and the slag layer and the ash content in the powdery coke or the unburning carbon are uniformly and sufficiently mixed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a zinc and / or lead smelting reduction furnace for treating a raw material containing zinc oxide.

[0002]

2. Description of the Related Art There are various methods for reducing and volatilizing zinc from a zinc oxide raw material, such as a blast furnace method, a blow smelting method, a flash smelting method and a slag fuming method. Among them, the flash smelting method. That is, a method in which powdered coke is burned in an oxidizing gas to obtain a reducing gas, and powdered zinc oxide is dispersed in a high temperature region formed at that time to instantaneously perform melt reduction to obtain metallic zinc vapor (for example, Japanese Patent Application No. 4-36918) is an excellent smelting method that can use inexpensive coke powder and has high productivity.

However, even in this flash smelting method,
In securing and maintaining a good furnace condition in the operation of the reduction furnace, the following two points are problems. The first is
This is a problem caused by the sedimentation in the furnace of the ash remaining after the combustion of powder coke. About 15 in powder coke
% Ash exists, but among the ash remaining after combustion of powder coke, those with a relatively large particle size settle on the slag in the furnace, and the other ash is discharged outside the furnace along with the exhaust gas. The ash that settled in the furnace has a smaller specific gravity than the molten slag, and since it is a high melting point substance because it contains alumina and silica as the main components, it floats in a semi-solid state on the molten slag surface in the furnace. Exists. Further, the intermediate layer, which is the boundary between the ash and the molten slag, has high quality of alumina and silica, and has a high viscosity. When semi-solid ash is present on the molten slag surface in this way, it not only adheres to the furnace wall and narrows the bath, but also causes tap holes to be blocked when extracting slag, making slag extraction very difficult. Become.

Next, there is a problem caused by the unburned carbon settling in the furnace. Of the coke dust, those that do not contribute to gasification remain as unburned components, but those with a relatively large particle size settle on the slag in the furnace, and the others are discharged outside the furnace along with the exhaust gas. It The carbon that has settled in this furnace may cover the surface of the molten slag and cause a strong strong reduction reaction locally to excessively reduce the iron oxides in the slag. It accumulates in the inside and causes a big trouble in the furnace operation.

As described above, it is important to solve the reduction furnace operation in the flash smelting process in order to promote the ashing of the ash of the powder coke that has settled in the furnace and the prevention of the production of metal iron due to unburned carbon. Although it is a problem, it has long been desired to develop an effective method for solving these problems.

[0006]

A method of operating a reduction furnace for zinc and / or lead smelting is proposed which is capable of promoting slag formation of powdered coke ash settled in the furnace and preventing generation of metal iron due to unburned carbon. The purpose is to

[0007]

In the operation of a zinc and / or lead smelting reduction furnace consisting of a shaft, a settler and an uptake, nitrogen, air, oxygen-enriched air and industrial air in the slag of the settler from the settler ceiling are used. It is characterized in that at least one selected from the group consisting of oxygen is blown through a lance whose tip is immersed in slag.

[0008]

If the lance tip is immersed in the slag melt and gas is blown into it, strong stirring of the melt can be obtained even if the amount of gas is small. Due to this effect, the ash content of the slag layer and the powdered coke or the unburned carbon is uniformly and sufficiently mixed, so that the promotion of the slag of the powdered coke ash and the reduction degree of the slag can be uniformly maintained. This can solve the problems of clogging of tap holes due to adhered substances and metal iron deposition due to local strong reduction of the slag surface.

Furthermore, since there is no temperature gradient in the depth direction of the slag melt due to strong stirring, heat can be applied to the furnace bottom,
It is also possible to suppress buildup of the furnace bottom.

In addition, since the amount of injected gas can be small, there is no concern that the amount of exhaust gas will suddenly increase and the heat balance of the slag melt will not be significantly affected. Even if an oxidizing gas such as air is blown in, if the amount is small, the degree of reduction of the molten slag and the exhaust gas will not be significantly changed.
However, if it is necessary to strictly maintain the degree of reduction of the molten slag and the exhaust gas, it is preferable to use an inert gas such as nitrogen.

In particular, when air, oxygen-enriched air, or industrial oxygen is used, it is appropriately used together with nitrogen gas, does not affect the CO ₂ / CO ratio of exhaust gas, and does not peroxidize the slag. Therefore, it is preferable to limit the blowing amount to a small amount.

Amount of powdered coke ash on slag, amount of unburned coke, amount of high-melting semi-solid suspended matter containing alumina and silica as main components, amount of metal iron deposited and grown on bottom of furnace Although it depends on the amount of gas to be blown and the speed at which it is blown, if the lance is immersed in the slag too deeply, the slag layer will be agitated only locally, so there is no effect. It is preferable to determine the immersion depth while observing. It was confirmed that when the immersion depth was 50 mm as in Examples described later, the effect was obtained in the range of the diameter of 1500 mm, so the immersion depth is preferably 50 mm or more. Further, the number of lances used is not limited to one, and it is desirable to determine the number of lances after confirming the above effects.

Furthermore, since this equipment is a very simple one consisting only of lances and gas flow pipes, even if it is a large-scale reduction furnace, if the settler ceiling has several holes,
Even when the equipment is relocated for the purpose of local recovery of the furnace condition, it is only necessary to extend the gas flow pipes, and the relocation is very simple.

[0014]

EXAMPLE In order to confirm the effect of the present invention, the shaft 1 shown in FIG. 1 has an inner diameter of 1.5 m, a height of 2.5 m, a settler 2 an inner diameter of 1.5 m, a length of 5.25 m, and a zinc oxide raw material treatment amount of 10
A reduction volatilization test of zinc from a zinc oxide raw material was performed using a t / day medium-scale test furnace.

Here, as the zinc oxide raw material, a calcined ore obtained by oxidizing and roasting zinc sulfide concentrate (Zn: 60.1% by weight,
Pb: 6.59 wt%, S: 0.5 wt%) and iron refined powder (Zn: 2.71) obtained by beneficiating the converter slag of copper smelting
% By weight, Pb: 2.72% by weight) were mixed at a ratio of 4 to 1, and the mixture was charged from the raw material charging port 9 by the flow air. Further, the powder coke charged from the powder coke charging port 7 of the shaft 1 by the flow air is CDQ dust (C: 80.96% by weight, F
e: 1.48% by weight, CaO: 1.84% by weight, SiO
₂ : 6.29% by weight, average particle diameter 22 μm) was used. Also, 90% O ₂ is charged from the oxygen charging port 8 to generate exhaust gas, metallic zinc vapor and dust which are taken up by 3
It is led out of the furnace.

A lance 6 using a stainless steel pipe having an inner diameter of 10 mm and an outer diameter of 16 mm is installed at the position of the settler ceiling shown in FIG. 1 and 20 Nm ³ / at a pressure of 1 kg / cm ^2.
The nitrogen gas of the time was blown. The immersion depth of the lance in the molten slag 4 was adjusted to be about 50 mm (the slag depth was about 300 mm). Further, the measurement at the furnace bottom level was performed using the measurement hole 10 located at a distance of 700 mm from the lance insertion hole.

Table 1 shows the test conditions and the results. A schematic diagram of the test furnace is shown in FIG. In Table 1, the slag composition and tap condition are for the slag extracted from the slag hole 5. The gas composition is the value at uptake 3. The unburned carbon rate is calculated by calculating the gasification rate of the powder coke from the CO, CO ₂ , O ₂ concentrations measured at the outlet of the flash reduction furnace and the amounts of powder coke and oxidizing gas that are charging conditions. It is a value calculated from the formula of carbon rate (%) = 100−gasification rate (%).

[0018]

[Table 1]

In Table 1, when the conventional operation shown in Case 1 (Comparative Example) is carried out, it is very difficult to extract the slag due to the outflow of the highly viscous slag and the clogging of the tap holes due to the coke ash content. It was not possible to completely discharge the adhered substances to the outside of the furnace. Then, when hot water was stirred by blowing gas into the slag bath, the coke ash content in the powder was sufficiently slagged as shown in Case 2 (Example), so that the slag could be extracted very smoothly. The slag removal amount shown in Table 1 shows the fluidity of slag 1
Although it is one of the indicators, it can be seen that in Case 2 (Example), the extraction amount increased sharply and the furnace condition recovered. In addition, the quality of iron metal in the slag was lowered, there was no concern about the generation of iron in the furnace, and the furnace bottom level was kept low, and good results were obtained.

When the effect of gas injection on the metallurgical performance was examined, the ratio of the amount of injected gas to the total amount of exhaust gas was small, so that the partial pressure of Zn vapor hardly changed even when the gas was injected. . Further, the unburned carbon rate was reduced by gas injection, and good results were obtained. It is considered that this is because when the molten slag splashed by the gas injection comes into contact with the exhaust gas, it works to collect a part of the unburned carbon.

[0021]

EFFECTS OF THE INVENTION According to the present invention, by a simple method, promotion of slag formation of powdered coke ash settled in the furnace and prevention of metal iron production by unburned carbon are achieved, and a good furnace in a reduction furnace operation is achieved. The situation can be secured and maintained.

[Brief description of drawings]

FIG. 1 is a schematic view of a reduction furnace for carrying out the method of the present invention.

[Explanation of symbols]

 1 Shaft 2 Settler 3 Uptake 4 Slag 5 Slag hole 6 Lance 7 Powder coke charging port 8 Oxygen charging port 9 Raw material charging port 10 Measuring hole

Claims (1)

[Claims] 1. In the operation of a zinc and / or lead smelting reduction furnace comprising a shaft, a settler and an uptake,
Characterized by blowing at least one selected from the group consisting of nitrogen, air, oxygen-enriched air and industrial oxygen into the slag of the settler from the settler ceiling through a lance whose tip is immersed in the slag. A method for operating a reducing furnace for smelting zinc and / or lead.