JPS6023870B2 - How to treat electric furnace dust - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating electric furnace dust.

Generally, electric furnace dust is industrial waste mainly containing useful oxides such as iron, zinc, and lead.

However, it contains large amounts of zinc and toxic metals, and if this slag is buried in open ground, the toxic metals will be leached out by rainwater. In addition, when used as a raw material for blast furnaces, the zinc and lead in the dust corrode the walls of the blast furnace in a metallic state. Due to these adverse effects, it is currently impossible to reuse it as a blast furnace raw material or dispose of it in a landfill. Furthermore, some electric furnace dust contains a large amount of lead, and when such electric furnace dust is added to molten steelmaking slag for treatment, 0.1 to 0.0% lead is added to the steelmaking slag after treatment. .2 degrees of elution may occur.

There is a method for disposing of such electric furnace dust by charging the electric furnace dust from above and dissolving it, but it is blocked by the hardened film on the surface of the melt, preventing it from entering the inside of the melt and allowing a sufficient melting reaction to take place. There is a drawback that it is not done.

There is also a method of injecting electric furnace dust from above the welding and physically pressuring it into the inside of the weld using a push bee to cause a melting reaction, but with this method, it takes a long time to inject it into the weld. There are drawbacks that require The present invention aims to solve the above-mentioned problems and to make electric furnace dust harmless and to effectively utilize it. Hereinafter, the outline of the method for treating electric furnace dust according to the present invention will be explained.

In other words, electric furnace dust containing zinc, lead, and other harmful metals is mixed with nitrogen into molten steelmaking slag that is placed in a ladle together with one or more of blast furnace slag, red mud, karami, masashi, and slate. By adding and mixing oxygen or air while performing bubbling, the steelmaking slag's surface hardened coating is involved and convection is generated throughout the slag, making use of the sensible heat of the steelmaking slag without adding new heat. The dust and the one or more additives mentioned above are melted and reacted effectively in a short time. In addition, during this reaction, the ignited zinc and lead are recovered with a normal millet equipment and used as valuable resources.

As a result, the steelmaking slag left to cool after the reaction completely prevents the elution of not only lead ions but also other heavy metal ions, and at the same time prevents collapse, and is expected to be effectively used for roadbed villages.
Some examples of experimental results of the present invention are shown below.

Experimental Examples Steelmaking slag, electric furnace dust, red mud, masa soil, karami, blast furnace slag, and slate samples were dried for at least 2 hours in an overflow dryer at 105 to 110qC, then steelmaking slag, red mud, and slate were dried. , karami, blast furnace slag, and slate were coarsely crushed to 4 pieces or less, and only the steelmaking slag was further subjected to magnetic separation to remove magnetic substances, and then used as a sample.

The chemical analysis values of the sample are shown in Table 1 below. Table 1 Table 2 shows the results of an elution test based on the Environmental Agency notification for electric furnace dust generated at factories.

Table 2 provides the results of elution tests for factory-generated electric furnace dust.

The test results are shown in Table 3. As shown in the examples in Tables 1 and 2 of Table 3, electric furnace dust seems to be caused by the raw materials used in electric furnace steelmaking and the operating conditions.
There are also variations in composition, and considerable variation is seen in the elution of heavy metal ions such as lead in elution tests.

Next, the test samples shown in Table 1 were crushed to 0.3 mm or less and mixed appropriately to make a Zegel cone and used to measure the temperature of the melt.Meanwhile, steelmaking slag was placed in a dew-molten magnesia and held at 1550 oo. It is remelted in a furnace, and nitrogen gas or air is blown into it at a flow rate of about 3/min for 2 minutes to cause convection of the melt, and red mud, masashi, karami, blast furnace slag, slate, and electric furnace dust ( Approximately 5 fences ◇ pellets) were added.

(200 samples in total). After that 1520~1510oo
After holding it for 1 minute, turn off the power switch and heat it to about 1200o.
The mixture was taken out of the furnace at o and allowed to cool. After this slag has been allowed to cool, identification of the main minerals contained in the slag is carried out by Xray diffraction, a melting test based on the notification of the Environment Agency, measurement of free lime by the Cement Association method, and measurement of the disintegration rate (5 to 1 The following tests were conducted for each grain size, and those with 5 or less ribs were considered to be disintegrated.

These results are shown in Tables 4-01 to 6. Table 4 (
1) Table 4 (2) - As is clear from Table 5, Table 6, and Table 4, pellets with a small lead content and only electric furnace dust were brought to a molten state while blowing nitrogen or air. When added to steelmaking slag and melted, no heavy metal ions are eluted and there is no problem.

However, when a pellet containing only a small amount of lead, consisting of electric furnace dust, is added to and melted into molten steelmaking slag while blowing nitrogen or air, some lead ions may be released. Therefore, when electric furnace dust, blast furnace slag, red mud, masa soil, karami, and slate are added to the molten steelmaking slag while blowing nitrogen or air into it, the welding temperature of the steelmaking slag decreases, which clearly lowers the melting point. The viscosity inevitably decreases.

As a result, sufficient convection of the molten slag due to nitrogen or air blowing is carried out, and the reaction with the additives is completely carried out.
Elimination of heavy metal elution. In addition, F・Ca○, y-Xa01Si02, etc., which cause the collapse of steelmaking slag, are extremely small.
and stable mineral a○, A〆203・Si02・hona
○・Fe203,4Ca○・A and 203・Fe203 etc. are generated and no longer collapse. In addition, if the steelmaking slag lacks sensible heat, it is obvious from this experimental example that equivalent results can be obtained by supplying heat from the outside or adding a substance with a high reaction heat. It is.

Next, examples of the present invention will be shown.

Example 1 Example of addition of electric furnace dust alone A lance was inserted into approximately 6,000 k9 of molten steelmaking slag received in a pot, and nitrogen was blown in for 2 minutes to cause convection of the algae.

Next, 200k9 of electric furnace dust pellets were added, followed by 2.0kg of nitrogen. The additives were blown into the tank and reacted violently, and the formed zinc and other substances were collected using a dust collector. After the reaction was completed, the steelmaking slag was cooled, crushed, and subjected to magnetic separation treatment, and then subjected to elution tests, roadbed tests, etc. based on the Environmental Agency notification. The results are shown in Tables 7 and 8. The analytical values of the electric furnace dust used are shown in Table 9 of Example B. Table 7 Table 8 As shown in Table 7, electric furnace dust with high lead content (P
b≠4.67%), some elution of bell ions was observed.

Example (b) Addition Example of Electric Furnace Dust + Blast Furnace Slag + Karami A lance was inserted into approximately 600 k9 of molten steelmaking slag received in a pot, and nitrogen was blown in for 2 minutes to cause convection of the weld metal.

Next, 200 kg of electric furnace dust, 200 kg of blast furnace slag, and 200 kg of karami were added to the mixture, and nitrogen was then blown in for 2.5 minutes to cause the additives to react vigorously. The grooved zinc etc. was collected by a dust collector. did. After the reaction, the steelmaking slag was cooled, crushed, and sorted, and then subjected to elution tests and roadbed material tests based on the Environmental Agency notification.

The results are shown in Tables 9 to 12. Table 9 Table 10 Table 11 Table 12 As explained above, the present invention uses crab odor furnace dust, which is difficult to dispose of, as industrial waste containing toxic metal oxides and their salts. By skillfully utilizing the sensible heat and reaction mechanism of steelmaking slag in a molten state, it is possible to perform pollution-free treatment simply and easily, as well as to recover valuable metals.
It is also a rational and useful invention that can prevent steelmaking slag from being lost and make it possible to effectively use it for slag board materials and the like.

Claims (1)

[Claims] 1 Adding and mixing electric furnace dust with one or more of blast furnace slag, red mud, karami, masa soil, and slate while blowing nitrogen, oxygen, or air into molten steelmaking slag while bubbling it. A method for treating electric furnace dust, characterized by: