KR100322040B1 - Recovering method of valuable metal from eaf dust using limestone sludge - Google Patents

Abstract

The present invention relates to a method for recovering a useful metal component from an electric dust by using limestone sludge generated as a by-product in the steelmaking process.

According to the present invention, limestone sludge, which is a by-product of the steelmaking process, can be recycled by using limestone sludge instead of limestone as a subsidiary material for adjusting basicity during electric dust treatment, and at the same time, expensive. By using instead of limestone, it is economical to recover useful components from dust by electric furnace at low cost.

Description

Method of recovering useful ingredients from electric furnace dust using limestone sludge {RECOVERING METHOD OF VALUABLE METAL FROM EAF DUST USING LIMESTONE SLUDGE}

The present invention relates to a method for recovering a useful metal component from an electric dust by using limestone sludge generated as a by-product in the steelmaking process.

In recent years, as environmental and environmental concerns are intensifying, electric furnace dust generated by the steel industry, especially electric furnace companies, contains not only a large amount of recyclable components, but also a high content of heavy metals. It is classified as a specific waste and is experiencing significant difficulties in recycling and landfilling.

Therefore, the useful components are recycled through the reprocessing of dust, and the slag generated after the treatment is made harmless so that the general landfill method is useful.

Conventional methods of treating dust with electricity are often stabilized by mixing various raw materials, such as Korean Patent Publication Nos. 87-003932 and 95-36604, but in this case, storage of each raw material is difficult. In addition, in most cases, the dust is not treated solely with electricity.

In addition, even when only the dust in the electric furnace is treated alone, most of the landfill or melting directly with the secondary raw material directly in the electric resistance furnace.

In addition, the electric furnace dust has a different composition depending on the source of the occurrence, mainly have a composition change for each company according to the difference in the operation method, the difference in the production steel species, and the various subsidiary materials resulting from this.

Therefore, in the process of electric dust treatment, the secondary material is mixed with the electric dust of the company to make a slag composition which is easy to melt and then melted.

In general, useful components that can be recovered in the dust of the electric furnace include Fe, Zn, and also contains a large amount of SiO ₂ , CaO, etc., which forms the main constituents of slag. It can be easily discharged in the process.

FIG. 1 shows a SiO ₂ -CaO-FeO ternary state diagram. As can be seen from this state diagram, it can be seen that the lowest slag melting temperature is exhibited when the basicity is 1.7.

Therefore, it can be seen that fixing the slag basicity to 1.7 in the operation process is advantageous for the low melting point of the slag.

Usually, when using one type of electric dust, the basicity is adjusted by using limestone as the CaO source to adjust the basicity of the slag to 1.7.

However, this method has the disadvantage of purchasing expensive limestone and crushing it to an appropriate size.

In addition, in order to secure the economics of the existing process in all industries, the technology development has been made in the direction of developing alternative raw materials that can replace expensive raw materials. Instead of using limestone as an auxiliary raw material, it was conceived that an electric dust can be treated economically by adjusting the slag composition by using fine limestone sludge generated as a by-product from the steelmaking process.

The present invention was made in the process of solving the problems of the prior art as described above and developing an economical alternative raw material, economical by using limestone sludge generated as a by-product in the iron making process instead of limestone as an auxiliary raw material in the electric furnace dust treatment. It is an object of the present invention to provide a method for recovering useful components from dust by improving the electric furnace.

1 is a diagram showing a state diagram of SiO ₂ -CaO-FeO ternary system,

2 is a view showing a comparison of the Fe component recovery rate in the electric furnace according to the invention and comparative examples,

3 is a view showing a comparison of the Zn component recovery rate in the electric furnace according to the invention example and comparative example.

In order to achieve the above object, in the present invention, in order to recover the useful components from the dust generated in the electric furnace, the limestone sludge which is a by-product of the steelmaking process is used.

Hereinafter, the present invention will be described in detail with reference to the preferred embodiments.

Table 1 shows the chemical composition of the electric dust used in the present invention, the iron content is about 38% by weight as a whole, the ZnO content is about 19% by weight.

In addition, the basicity of the electric furnace dust is 0.57, and in the case of electric dust, about 6.0 wt% of limestone should be added.

TABLE 1 (% by weight)

division T.Fe ZnO SiO ₂ CaO Al ₂ O ₃ MgO Na ₂ O K ₂ O Pb CD basicity Dust 37.8 19.2 5.7 3.3 0.87 1.1 1.5 2.1 2.0 0.018 0.57

Table 2 shows the amount of the main raw materials and subsidiary materials when recycling dust and limestone or limestone sludge produced in an electric furnace in a total amount of 100 kg. It was shown that the basicity was maintained at 1.7, and in Fig. 2 and Fig. 3, the result of experiments by adjusting the basicity in the invention example using the electric roaster as the main raw material and the limestone sludge as the subsidiary material and the comparative example using the limestone as the subsidiary raw material was used. The recovery rates of phosphorus Fe and Zn are compared and shown.

TABLE 2

Test Example Composition (㎏) % Recovery Dust A Dust B Limestone Limestone sludge Fe Zn Inventive Example 94.0 - - 6.0 85.7 86.2 Comparative example - 93.9 6.1 - 84.6 85.9

As can be seen from Figure 2 and 3, in the case of the invention example Fe was recovered 85.7%, the metal Zn was found to recover about 86.2%, in the case of Comparative Example Fe is recovered 84.6%, metal Zn is 85.9 % Recovered.

Therefore, according to the invention example, it can be seen that the Fe recovery rate is 1.1%, Zn recovery is 0.3% increase compared to the comparative example. The actual recovery rate remained at about 1% due to the characteristics of the dust, which resulted in a large amount of gas generated as the reduction reaction proceeded. As a result, some dust was removed from the reaction vessel due to the unreacted reaction and recovered in the bag filter.

In addition, since the recovery amount (secondary dust) of the mixed dust in the bag filter is large, the quicklime or silica that is mixed with the subsidiary materials is injected into the bulk instead of the fine powder, so the amount of fine powder is reduced so that the amount of secondary dust is generated. It turns out that this becomes small.

Therefore, according to the present invention as described above, by using the limestone sludge to replace the limestone as an auxiliary material for adjusting the basicity during the electric dust treatment, by using the limestone sludge to recover the useful components without reducing the recovery rate, the limestone sludge which is a by-product of the steelmaking process is recycled. At the same time, it is economical because it can recover useful components from electric furnace dust at low cost by using instead of expensive limestone.

Claims (1)

Injecting dust generated in the electric furnace into the furnace; Melting dust by charged electricity; A method for recovering a useful component from an electric dust comprising a step of recovering a useful metal by excluding slag while tapping the molten melt. In order to maintain the most stable optimum basicity of molten slag in the step of charging the furnace dust into the furnace, the mixture of the electric furnace dust and limestone sludge in a ratio of 64:36 to charge the mixture Method for recovering useful components from electric furnace dust using limestone sludge.