JPS6033175B2 - How to treat electric furnace dust - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering valuable resources, mainly zinc and lead, from electric furnace dust.

Electric furnace dust is generated during electric furnace operation by collecting it with a back filter, conveying it from the hopper to the beretizer room by a conveyor, and sprinkling it with an appropriate amount of water.
The granules are granulated into 5th cubes and discharged.

The components of electric furnace dust are shown in Table 1, and it contains valuable metals such as zinc, as well as large amounts of harmful metal oxides such as lead, chromium, and cadmium, which are eluted into rainwater, etc.
Landfill disposal is not allowed. Table 2 shows the elution test results for factory-generated electric furnace dust based on the Environmental Agency notification.

Furthermore, when used as an auxiliary raw material for sintering to be used as a blast furnace raw material, zinc cannot be removed during the sintering process, so the zinc oxide in the 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 for Electric Furnace Gusto (by weight) The blending ratio of raw materials is as follows.

Weight Weight Weight example 1 Steel scrap 40% Pressed material 40% Gray powder (braced material) 20*Example 2 ″ 10% ″
60% ″ 30% Example 3 ″ 70%
〃 15* 〃 15%Table 2 Elution test of electric furnace dust according to Environment Agency Notification K For these reasons, each electric furnace manufacturer commissions a secondary concentrator to process the electric furnace dust. There is.

In other words, carbonaceous agent is mixed with pseudo-mini pellets brought in from each electric furnace manufacturer, and the mixture is charged into the Ull furnace, which is a reduction incinerator, and reduced.Reduced iron pellets are collected using a magnetic separator, and at the same time, they are reduced and vaporized. The zinc is oxidized again and recovered as crude zinc oxide, and harmful metals are removed by wet treatment and reused.

From the perspective of resource recycling, recovering zinc from industrial waste that cannot be thrown away and reusing it as a valuable resource is considered appropriate from a resource recycling perspective. This is not the best method considering the cost, the energy required for reheating, and the electric furnace manufacturer's considerable cost share. The method of the present invention relates to a method for solving the above-mentioned problems, and its gist is to charge electric furnace dust into an operating electric furnace and collect volatile oxides mainly consisting of zinc oxide and lead oxide. A back filter is installed through a branch duct in the middle of the duct that connects the electric furnace and the furnace direct dust collector, and a damper is installed inside each of the ducts and the branch duct. First, when performing normal oxidation period operation, open the damper leading to the furnace direct dust collector, close the damper leading to the back filter to perform normal dust collection, and immediately before the end of oxidation period operation, remove the electric furnace dust. At the same time, switch both dampers, open the damper leading to the back filter, close the damper leading to the furnace direct dust collector,
The brightening oxides are collected by the back filter, then both dampers are switched again, and the normal reduction period operation is continued with dust collection using the furnace direct dust collector, and just before the end of the reduction period operation, the electricity is turned on again. This is a method for treating electric furnace dust, in which furnace dust is charged and volatile oxides are recovered by switching both dampers.

The experiments that led to the invention of the present application and their results will be shown below.
Example of an experiment Install back filter 6 into each duct with damper 3.
, 4 are provided.

First, damper 3 is opened, damper 4 is closed, and scrap metal is charged, melted, melted, and oxygen is blown into the steel. The thing separates and rises, and the steel guys are on it.

Shortly before the end of this oxidation reaction, an electric furnace dust pellet of approximately 200k9 is introduced from the furnace section, and at the same time, the damper 3 is closed and the damper 4 is opened, and the oxidation products of valuable metals are collected by the back filter 6, and the generation of oxidation products is When the process is complete, return the damper to its original state, tilt the furnace a little to let the steel birch flow out, and then scrape it out completely from the charging door with a wooden peg and remove it, returning the furnace to its original state. It is returned to steel and refined through reduction phase reactions.

The recovered fume was a nearly white powder, and the iron contained in the electric furnace dust was successfully mixed with molten steel or molten steel and recovered as a product with a high zinc content.

Its components are shown in Table 3. *...The components that remain in the electric furnace without being vaporized when it is put into the electric furnace are mainly dissolved in the slag during the oxidation stage, and the slag hardly expands or disintegrates, and is not eluted by rainwater, etc. It has become. Tables 4 and 5 show the chemical analysis values of the slag during the oxidation stage during normal operation, the slag when electric furnace dust was charged, and the results of the elution test as notified by the Environment Agency.

Table 3 (Weight *) Table 4 Chemical analysis values of electric furnace slag (Weight *) Sample 1 Oxidation stage slurry from normal operation 2 Oxidation stage slurry with electric furnace dust added Table 5 Elution test results and roadbed material test results are shown in Table 6. The disintegration rate was measured according to the ASTM standard (200oo, 20 ribs/clump, held for 3 hours) for particle sizes from 10 to 25, and particles of 1 or less were considered to be disintegrated, and (F. CaO) was conducted using the JIS Cement Association method, and the roadbed material test was conducted using the JIS method.

Table 6 Electric furnace slack roadbed material test results, etc. *・・・・１
The test results for three particle sizes are shown.

In addition, at the end of the reduction period operation, electric furnace dust pellets (100
0k9) was charged from the top of the furnace, damper 3 was closed and damper 4 was opened in the same manner as described above, and the product was recovered through back filter 6. A product with a high zinc content, which was almost the same as the components shown in Table 3, was recovered. Tables 7 and 8 show the chemical analysis values of the reducing stage slag during normal operation, the slag when electric furnace dust was charged, and the results of the elution test notified by the Environment Agency. Table 7 Chemical analysis values of electric furnace slack (weight: Tsutomu) Sample 1 Reduction stage slag during normal operation 2 Reduction stage slag into which electric furnace Gusto was added Table 8 Elution test results Beret (10
00k9) from the top of the furnace and analyzed the dust collected in the back filter 6 by the same operation as above, as shown in Table 9, the normal dust and the residue from the dust pellet were mixed, and T.Fe It is light brown dust with a high Zn content (approximately 4.5% higher than the Zn content of the input dust).

*Table 9: Chemical analysis of recovered dust (weight) Furthermore, the results of roadbed material tests are shown for the first time, but the test methods are the same as those shown in Table 6.

Table 10 Roadbed material test results, etc. The abbreviations of the main minerals contained are as follows: o Ge. ．． ．． ．． '． ．． ．． 20a0. AZ202・Si02
04AF. ．． ．． ．． ．． ．． 40a0. -Apu203
・Fe208AK・・・20a0. Mg0.2S
i02 He...Fe20302F...
...20a○・Fe203 r-02S・
・・・・・・r-20a○・Si02 As stated above, according to the method of the present invention, wastes containing valuable but harmful metal oxides and their salts are currently difficult to dispose of as industrial waste. By charging the electric furnace dust having the Since the agglomerated slag does not disintegrate, it has the advantage that it can be effectively used for roadbed materials, etc.

[Brief explanation of drawings]

The drawing is a schematic explanatory diagram of the method of the present invention. In the figure, 1: electric furnace, 2: dust collection duct, 3, 4: switching damper, 5: operational dust collector, 6: back filter.

Claims (1)

[Claims] 1. Electric furnace dust is charged into an operating electric furnace, and a back filter that collects the generated volatile oxides mainly consisting of zinc oxide and lead oxide is connected to the electric furnace and the furnace direct dust collector. It is installed through a branch duct from the middle of the duct, and dampers are installed inside both the above duct and the branch duct, and during normal electric furnace operation,
Only the damper in the duct connected to the furnace direct dust collector is opened to collect dust, and the electric furnace duct is inserted into the electric furnace at the end of the oxidation and reduction periods to generate the volatile oxides mentioned above. A method for treating an electric furnace duct, which is characterized by opening only a damper in a branch duct leading to a back filter to recover volatile oxides.