JPS6056407B2 - How to treat electric furnace dust - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for producing steel by injecting a part of electric furnace dust containing harmful heavy metals generated in electric furnace steelmaking together with steelmaking raw materials or before the middle of the oxidation period, while performing steelmaking operations. This invention relates to a method of effectively utilizing the appearance of steelmaking slag in a molten state, recovering a part of the dust by volatilization and reusing it as an effective resource, and fixing the remaining part in the steelmaking slag.

Generally, electric furnace dust is industrial waste mainly containing useful oxides such as iron, zinc, and lead. However, it contains a large amount of zinc and toxic metals, and if this dust is buried in open ground, the toxic metals will be leached out by rainwater.

Furthermore, when used as a raw material for blast furnaces, the zinc and lead in the slag are in a metallic state and corrode the walls of the blast furnace, so they cannot be reused as raw materials for blast furnaces or disposed of in landfills.

Currently, we are sending it to dust processing companies, zinc smelting manufacturers, etc., and requesting that it be processed as raw material for refined zinc recovery. Furthermore, some electric furnace dust contains a large amount of lead, and when such electric furnace dust is added to molten steelmaking slag and treated in large quantities, 0.1% of lead ions are removed from the slag after treatment. It may elute about 0 to 10 μm.

As a method for treating such electric furnace dust, there is a method in which the electric furnace dust is poured onto the slag and melted.

However, there is a drawback that the surface of the molten slag is covered with a hardened film, which prevents it from entering the inside of the slag and a sufficient dissolution reaction cannot take place. Further, the method of pressurizing the electric furnace dust into the molten slag to cause a dissolution reaction has the disadvantage that it takes time to press the electric furnace dust into the slag.

The purpose of the present invention is to solve the above-mentioned problems, to make electric furnace dust harmless, and to make effective use of it. Then, the steel is charged into an electric furnace and steel-making operations are carried out.
A method for treating electric furnace dust, which comprises blowing bubbling gas into molten slag to remove residual electric furnace dust, and adding one or more of blast furnace slag, red mud, karami, masa soil, and slate. be.

In other words, considering the amount of steelmaking slag generated and the amount of dust, if sensible heat from the slag alone is insufficient to render the dust harmless, or if the zinc and lead content in the dust is low, some of the dust may be used together with the steelmaking raw materials. The zinc and lead content in the dust is increased through steelmaking operations, and bubbling gas such as nitrogen, oxygen, or air is injected into the molten steelmaking slag that receives this dust in a ladle. The surface-hardened film of the slag is involved, causing convection throughout the slag, and the sensible heat of the slag is used without adding new heat. Electric furnace dust, blast furnace slag, red mud, and masa soil are , slate, or karami, or in contact with the slag flow discharged into the ladle,
One or more of blast furnace slag, red mud, slate, masa soil, and karami are added to lower the solidification temperature and viscosity of the slag, and then electric furnace dust is introduced while bubbling gas is blown in to create convection. This allows the melting reaction to occur effectively.

In addition, the zinc and lead volatilized during this reaction are collected by installing a normal dust collector, taken out of the steelmaking equipment system, and used as valuable resources.

As a result, the steelmaking slag that has been left to cool after the reaction is completely prevented from leaching not only lead ions but also other heavy metal ions, and at the same time is also prevented from collapsing, and is expected to be effectively used as a roadbed material.

In addition, if pellets, briquettes, etc. in which reducing substances such as coke are added to electric furnace dust are used, Zn. ．． The volatilization of Pb, etc. is improved, and there is no problem in reforming the slag during the reduction stage. Below, some examples of experimental results of the present invention are shown.

Examples Steelmaking slag, electric furnace dust, red mud, masa soil, karami, blast furnace slag, and slate samples were dried in a constant temperature dryer of 105 to 110 for 24 hours or more, and then steelmaking slag, red mud, masa soil, and karami were dried. , blast furnace slag, and slate were roughly crushed to 4 Trrm or less, and only the steelmaking slag was further subjected to magnetic separation treatment to remove magnetic substances, and then used as a sample.

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

As shown in the examples in Tables 1 and 2, electric furnace dust seems to depend on the raw materials used in electric furnace steelmaking and operating conditions, but there are also considerable variations in chemical composition and elution tests.

Next, the test samples shown in Table 1 were ground and blended to 0.3 TmIrL or less, a Zegel weight was made, and the melting temperature was measured.

The results are shown in Table 3. In addition, steelmaking slag is placed in an electrofused magnetic crucible and remelted in a silicone electric furnace maintained at 1550'C, and nitrogen gas, air, or oxygen is blown into this at a flow rate of about 3f/min for 2 minutes to convect the slag. While stirring, red mud, masa soil, karami, blast furnace slag, slate, and electric furnace dust (approximately 5 mm diameter pellets) were added to the sample for a total sample size of 200 y.

After that, the temperature was maintained at 1520 to 1510°C for 1 minute, the power switch was turned off, and the temperature was about 1200°C, and the temperature was taken out of the furnace and allowed to cool. After cooling, the slag is subjected to an elution test based on the Environmental Agency notification, identification of the main mineral content by !n particle size, and those with a particle size of 5 or less were considered to be disintegrated.). The results are shown in Tables 4 to 6.

In addition, F-CaO is measured using the Cement Association method (JIS).
The disintegration rate was measured under ASTM standard autoclave conditions.
~107077! -5Wr! n was taken as a decaying material.

As is clear from Table 5, when electric furnace dust pellets with a low lead content are added to molten steelmaking slag while blowing nitrogen or air, some lead ions will be eluted if the amount added is large. Sometimes I do.

Therefore, while blowing nitrogen or air into molten steelmaking slag, electric furnace dust pellets, red mud, masa soil,
When karami, blast furnace slag, and slate are added, the melting temperature of the steelmaking slag decreases, which obviously lowers the melting point and inevitably lowers the viscosity.

As a result, sufficient convection of the molten slag due to the blowing of air or nitrogen occurs, and the reaction with the additives is completed, eliminating the elution of heavy metal ions. In addition, F-CaOl6-2Ca0-SiO2, which is the cause of the collapse of steelmaking slag, is extremely reduced, and stable minerals A2ca04-Al2O3●
SlO2, 2Ca0-MgO-2Si02, 2ca0-
Fe2O3, 3Ca0-Al2O3, Fe2O3, etc. are generated and no longer collapse. Next, examples of the present invention will be shown.

Of the electric furnace dust generated during electric furnace operation, approximately 40 to 5
Seven examples will be shown in which the electric furnace dust was treated while blowing out about 50 to 60% of air or nitrogen to the copper slag while returning 0% of the dust to the electric furnace together with the steelmaking raw materials.

Example 1 In an electric furnace 1 having a nominal capacity of 40 tons and having a top-charging method with a rotating furnace lid and having the cross-sectional shape shown in FIG. The switching valve 3 is opened through the switch valve 4, the switching valve 4 is closed, the dust is collected in the dust collector (back filter) 5, and the oxidation stage slag is discharged into the ladle 12 (approx. Then, insert the lance 11 and send air at 1 to 3k9/CTI, and while bubbling, add 800k9 pellets from the dust hopper 8 and 100k9 additives from the additive hopper 9 over 3 minutes and 3σ seconds. , After blowing air for about 3 minutes as an after-blow,
The lance was lifted from the molten slag.

At that time, the switching valve 4 was fully closed and 3 was closed by about 40%, and while the volatilized crude zinc was collected by the electrostatic precipitator 10, the dust generated from the electric furnace 1 during normal operation was collected by the back filter 5. .

Example 2 A specimen with a nominal capacity of 40 tons having the cross-sectional shape shown in FIG. In the electric furnace 1 with a rotating furnace top charging system, 500 kg of dust pellets are introduced from the dust pellet hopper 7 during copper manufacturing work, and the dust pellets 2 are passed through, and the switching valve 3 is fully closed. It was closed and dust was collected using a back filter 5.

The slag is discharged to another ladle and collected in the dust collector 5 in the same way during the reduction period operation, and the steelmaking slag (approximately 4000 kg) is collected in the ladle 12 placed on a trolley 15 for dust treatment. room 14
and insert lance 11 to pump air to 1~3k9/C.
While feeding and pulling with fl, 900 kg of dust pellet hopper 8 and 150 kg of additive material were introduced from additive hopper 9 over 4 minutes, and after blowing air for about 3 minutes, He pulled up Lance.

At this time, switch valve 4 is fully closed, 3 is opened approximately 50%, and 1
Volatized crude zinc from No. 4 was collected with an electrostatic precipitator 10, and normal operation dust was collected with a back filter 5.

Below, the test results of the samples conducted in Examples 1 and 2 will be described.

Table 7 shows the chemical analysis values of the recovered valuable metal oxide (crude zinc).

In addition, the oxidation stage and reduction stage slag generated in the above treatment are crushed,
After magnetic separation treatment, the elution test results are shown in Table 8 using the methods notified by the Environment Agency, and the slag analysis results are shown in Table 9.
IS method), disintegration rate (10 to 25 Tfr according to ASTM standard!
10TfrIn or less was considered a disintegrating material), F-CaO (JISl Cement Association method) was measured, and the main minerals contained were examined by X-ray diffraction.The results are shown in the first part.

In addition, dust pellets are introduced from the top of the furnace together with the steelmaking raw materials during the oxidation period operation and before the start of the oxidation period operation, and even if the dust collected by the operation dust collector 5 is analyzed, the volatile matter from the normal dust and dust pellets is As shown in Table 11, zinc is slightly higher in the light brown dust (approximately 2.5 to 4
．． 5), which is almost the same as normal dust.

Example 3 As shown in Fig. 2, 15% (700k9) of electric furnace dust pellets were charged while blowing air into the steelmaking slag (4000k9) received from the ladle into the ladle after continuous casting. Air was blown into the solution for 4 minutes to cause a vigorous reaction, and the volatilized zinc substance was 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 material tests, etc. based on the methods notified by the Environment Agency.

The results are shown in Method 1.

Table 13 shows the chemical analysis values of the steelmaking slag, dust pellets, and treated slag used.

Example 4 As shown in Figure 2, about 3.7% (4000k9) of steelmaking slag (4000k9), which is received from the ladle after continuous casting is finished, is mixed with slate, karami, red mud, etc. Approximately 18% (900 kg) of electric furnace task pellets were added while stirring the steel slag by blowing air into the furnace. Air was then blown in for 4 minutes to cause a vigorous reaction, and the volatilized zinc was collected using a dust collector. did.

After the reaction was completed, the steelmaking slag was cooled, crushed, and subjected to magnetic separation treatment, and then subjected to elution tests, roadbed material tests, etc. based on the methods notified by the Environment Agency. The results are shown in Table 14.

Further, the chemical analysis values of the steelmaking slag used, the dust pellets, the slag after treatment, and the chemical analysis values of the volatilized recovered material are shown in the first bale.

As explained above, the present invention is an industrial waste containing toxic metal oxides and their salts, which is difficult to dispose of, and is processed by inputting it together with steelmaking raw materials in an electric furnace. On the other hand, by effectively utilizing the sensible heat of the steelmaking slag in a molten state, the remaining electric furnace dust can be simply and easily treated to make the entire amount of generated material non-polluting, and valuable metals can be recovered. This prevents the steelmaking slag from collapsing, allowing it to be effectively used as roadbed material, etc.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of Embodiment 1 and Embodiment 2, and FIG. 2 is a schematic explanatory diagram of Embodiment 3 and Embodiment 4. In the figure, 1...Electric furnace, 2...Dust collection duct for operation, 3, 4...Switching damper, 5...
・Operation dust collector (back filter), 6... Pelletizer, 7, 8... Dust pellet hopper, 9... Additive hopper, 10... Electrostatic precipitator, 11... Lance, 12... Slow pot, 13... Molten slag, 14... Dust treatment chamber.

Claims (1)

[Claims] 1. Part of the electric furnace dust is charged into the electric furnace together with the steelmaking raw materials or before the middle of the oxidation period to perform steelmaking operations, and the dust enriched with zinc and lead is collected by the furnace direct dust collector. Then, the remaining electric furnace dust is removed from the blast furnace slag by blowing bubbling gas into the molten slag discharged from the electric furnace.
A dust collector installed separately from the above-mentioned furnace direct dust collector to collect volatile substances such as zinc oxide and lead oxide that are mixed in with one or more of red mud, karami, masa soil, and slate, and are generated at this time. 1. A method for treating electric furnace dust, characterized by recovering it by.