JPS6011092B2 - How to treat electric furnace dust - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a processing method for recovering valuable metals from electric furnace dust containing harmful heavy metals and preventing the molten slag after agglomeration from collapsing.

Electric furnace dust is generated during electric furnace operation, collected in a back filter, transported from a hopper to the beretizer room by a conveyor, and sprinkled with an appropriate amount of water.
It is granulated and discharged. The components of electric furnace dust are
As shown in the table, it contains valuable metals such as zinc, as well as large amounts of toxic metal oxides such as chromium and cadmium, and because they elute when they come in contact with rainwater, they cannot be disposed of in landfills. Table 2 shows the results of the electric furnace dust total output test based on the method notified by the Environment Agency.

In addition, when used as a raw material for blast furnaces or as an auxiliary raw material for baking stripes, zinc cannot be removed during the freezing process, so zinc oxide in electric furnace dust is reduced by coke during blast furnace operation. It cannot be used because it becomes metal and corrodes the blast furnace wall.

Table 1 Chemical analysis values of electric furnace dust Table 2 Results of elution test of electric furnace dust For these reasons, each electric furnace manufacturer commissions a secondary concentrator to process the electric furnace dust.

In other words, ``The pellets brought in from each electric furnace manufacturer are mixed with coke powder, etc., placed in bags in a well furnace, which is a reduction sintering furnace, and reduced, and the reduced iron pellets are taken out in a magnetic separator, and at the same time the zinc is made into reduced barrels. It is oxidized again and recovered as crude zinc oxide, and harmful metal oxides are removed by wet treatment and reused.

In this way, recovering zinc from industrial waste that cannot be dumped and reusing it as a valuable resource is considered appropriate from a resource recycling perspective, but the cost of transporting it to a processing plant is , the energy required for reheating,
This cannot be said to be the best method considering the considerable cost sharing by the electric furnace manufacturer.

In addition, one or more additives are added to effectively utilize the sensible heat of molten steelmaking slag, reduce the viscosity of molten slag, lower the solidification temperature, and prevent the elution of harmful ions. Table 3 shows the chemical analysis values for mud, slate, slag, blast furnace slag, and karami. Table 3 Chemical analysis values of additives The present invention relates to a method for solving the above-mentioned problems. blast furnace slag,
In order to collect volatile oxides, mainly zinc oxide and lead oxide, which are mixed with one or more types of red mud, karami, masashi, and slate, the furnace direct dust collector is divided into two rooms and ducted. Normally, the electric furnace is operated using all chambers, and when the amount of barreled material increases, the damper of the duct at the entrance of each of the two chambers of the dust collection pipe is switched to close one of them. A method for treating electric furnace dust, characterized by separately collecting normal dust and volatile oxides.

In addition, when electric furnace slag is used as a sub-examiner heat source in the present method, the amount of molten electric furnace slag generated is insufficient compared to the amount of dust generated (taking into account rattan fever), so the amount of dust In actual operation, it would be efficient to explore a method of returning some of the waste and putting it into the electric furnace again.

Since the amount of molten slag generated in converters and blast furnaces is large, it goes without saying that such consideration does not need to be taken. The experiments that led to the development of the method of the present invention and their results will be shown below.

[Experiment 1] Electric furnace 1 with nominal capacity 4 and furnace top charging method with rotating furnace lid having the cross-sectional shape shown in the drawing, and bag filter 4 for direct feeding into the furnace
is divided into two chambers, and during normal operation, the switching dampers 3 and 16 are opened to let the dust fall, and the collected dust is put into the hopper above the beletizer 7 using a comper, and is granulated while being sprinkled with water by the beletizer 7.

At the end of scouring, when the amount of dust usually decreases, 1000 k9 of dust pellets are charged from the dust hopper 9, the switching valve 16 is closed, the switching damper 3 is opened, valuable metals are recovered using the bag filter 6, and the metals are put into the hopper outside the system. After the reaction was completed, the operation was reversed to collect the normal dust.

[Experiment 2] In an electric furnace 1 with a nominal capacity of 4 mm and a rotating furnace top charging system having the cross-sectional shape shown in the drawing, the steelmaking melt after normal operation was placed on a trolley 14 and placed in a ladle 12 with approximately 4000k9 Hijitsu, put it in the dust treatment chamber 15, insert the lance 11, and blow the air 1
While buffing, feed 900 ko of pellets from dust pellet hopper 8 and 150 ko of additives from additive hopper 10 (red mud, sukuita kun, karami as melting point lowering materials and harmful substances elution prevention materials). After adding 2 types of molten slag, molten slag, and blast furnace slag for 4 minutes, and blowing air for 3 minutes as after-blow, the lance was lifted from the molten slag.

At that time, the switching valve 16 is opened to collect normal dust, the switching valves 3 and 17 are closed, the switching valves 5 and 18 are opened, the dust is collected by the bag filter 6, valuable metal oxides are recovered, and the system I put it in the hopper outside. Table 4 shows the chemical analysis values of the valuable metal oxides recovered as the results of the above experiments. Table 4 Samples 1 Recovered materials put into the electric furnace at the end of the oxidation period operation 2 Recovered materials treated by melting in the dust treatment room When put into the electric furnace, the recovered materials remained without brightening The components are solidified into the steelmaking slag, and when they are similarly put into the melting process in the dust treatment room, the components that remain without being volatilized are also solidified into the steelmaking slag, so the chemical analysis value of the slag and the Environmental Agency notification. The dissolution test results are shown in Tables 5 and 6.

Table 5 Chemical analysis values of electric furnace slag Table 6
Elution test results for electric furnace slag. Also, the above slag was subjected to roadbed village test (JIS method), disintegration rate (10 to 25 according to ASTM standard)
(The grain size was measured on the side, and those below 10 grains were considered to be disintegrated).
F.Ca○ (JIS Cement Association method) was measured, and the main minerals contained were examined by X-ray diffraction. The results are shown in Table 7.

Table 7: Roadbed material test results, etc. *1 Most of the material had dusted and collapsed, so it was not measured.

〆-. 2S...Goo-20a.

-Si. 2 *3 Indicates the measurement results based on JIS B particle size.

Furthermore, even if a dust pellet of 1000k9 is introduced from the furnace section together with the steelmaking raw material during the oxidation period operation and before the start of the oxidation period operation, and the dust collected by the valuable metal recovery dust collector 6 is analyzed in the same manner as above, it is not found to be normal dust. Bright substances from the dust pellet were mixed in, and as shown in Table 8, the dust was light brown with high T and Fe content and low Zn content. Table 8: Chemical analysis values of recovered dust As explained above, according to the method of the present invention, electric furnace dust, which is currently difficult to dispose of as industrial waste, can be put into an operating electric furnace or molten While bubbling gas such as air is blown into steelmaking slag, it is added together with additives such as blast furnace slag, red mud, karami, masashi, slate, etc., and valuable metal oxides are recovered by appropriately switching the damper. In addition, residual components can be solid-dissolved in the slag to render it harmless, and since the slag after agglomeration does not disintegrate, it can be effectively used as a roadbed material, etc.

[Brief explanation of drawings]

The drawing is a schematic explanatory diagram of the method of the present application. In the figure, 1... electric furnace, 2... dust collection duct for operation, 3...
Switching damper, 4...Dust collector for operation (bag filter), 5...Switching damper, 6...Dust collector for valuable metal recovery and operation, 7...Beletizer,
8, 9... Dust barrel hopper, 10... Additive hopper, 11... Lance, 12... Nori pot, 13...
... Molten slag, 14 ... Trolley, 15 ...
...Dust processing chamber, 16, 17, 18...Switching damper.

Claims (1)

[Claims] 1. Electric furnace dust is charged alone into an electric furnace or into molten steelmaking slag into which bubbling gas is being blown together with one or more of blast furnace slag, red mud, karami, masa soil, and slate, and the dust is mainly oxidized. In order to collect volatile oxides consisting of zinc and lead oxide, the furnace direct dust collector is divided into two rooms with ducts attached, and normally all rooms are used for electric furnace operation, which results in a large amount of volatile substances. The electric furnace dust is characterized in that normal dust and volatile oxides are individually collected together by switching the damper of the duct at the entrance of each of the two chambers of the dust collector to close one of them at the time. Processing method.