JPS62170436A - Method for recovering valuable metal from dust discharged from metallurgical furnace for refining of metal - Google Patents

Abstract

PURPOSE:To make efficient and economical sepn. and recovery by providing dams to increase the reduction time of dust in the stage of reducing and evaporating the dust contg. Fe2O3, ZnO, PbO, in a rotary kiln and separating and recovering Zn and Pb. CONSTITUTION:The rotary kiln 1 is trisected in the longitudinal direction by the intermediate dams 6, 7 to the 1st reducing atmosphere zone A (about 650 deg.C), 2nd reducing atmosphere zone B (about 1,200 deg.C) and oxidative atmosphere zone C (about 1,200 deg.C). The dust contg. Fe2O3, ZnO and PbO is charged together with a solid carbonaceous reducing agent in this state into the rotary kiln 1 by a chute 2 and is moved in the kiln. The moving time is increased by the dams 6, 7, by which the reducing efficiency is improved. The ZnO and PbO are actively reduced and evaporated so as to be separated from the dust and are then reoxidized by oxygen to ZnO and PbO which are discharged together with an exhaust gas from an inlet 1a. The Fe2O3 is made into clinker together with the residual slag in the dust and is discharged from an outlet 1b.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for efficiently and economically recovering useful metals such as zinc and lead from dust discharged from a metallurgical furnace for metal refining. It is something.

[Prior art and its problems]

For example, when manufacturing steel using steel scrap, including scrap of galvanized steel sheets, as raw material in an electric furnace for steelmaking, a large amount of dust generated from the electric furnace during refining contains not only iron but also zinc, Contains large amounts of useful metals such as lead. Disposing of such dust as it is is not only extremely uneconomical in terms of effective use of resources, but also because the useful metals mentioned above are toxic substances, disposing of it as is is a serious pollution problem. This is a serious problem.

For this reason, research has been conducted on methods for recovering useful metals such as zinc and lead from the dust discharged from metallurgical furnaces for metal refining, such as electric furnaces for steelmaking. Volatilization recovery method has been put into practical use.

As one of the reduction and volatilization recovery methods using a rotary kiln,
For example, Japanese Patent Publication No. 57-44 filed by the applicant, etc.
No. 737 discloses a method consisting of:

A necessary amount of steelmaking electric furnace dust to reduce Fe2O3 contained in the dust to almost FeO, and a necessary paper to reduce zinc oxide, lead oxide, etc. contained in the dust. and a solid carbonaceous reducing agent in an amount equal to the total amount of the above-mentioned amount required as a heat source for each reduction, and the dust and the reducing agent are moved toward the outlet of the rotary kiln. The inside of the rotary kiln is made into an oxidizing atmosphere zone near the outlet and a reducing atmosphere zone elsewhere, and the temperature of the oxidizing atmosphere zone is increased by a burner provided at the outlet, and in the reducing atmosphere zone, By reducing Fe2O contained in the dust to FeO, reoxidizing FeO in the oxidizing atmosphere zone, and burning the reducing agent as a heat source, the oxidizing atmosphere zone is The temperature of the adjacent reducing atmosphere zone is increased, and thus zinc oxide, lead oxide, etc. contained in the dust are reduced and vaporized in the high temperature reducing atmosphere zone, and zinc, lead, etc. are removed from the dust. The thus separated zinc, lead, etc. are discharged from the rotary kiln together with the exhaust gas and recovered.

According to the above method, zinc contained in the dust,
Useful metals such as lead can be efficiently recovered.

However, in actual operation, it has been found that the conventional method as described above has the following problems. That is, the dust and solid carbonaceous reducing agent charged into the rotary kiln are moved from the inlet to the outlet by the rotation of the rotary kiln, which is inclined at a slope of 2/100 to 3/100. This moving speed is determined by the rotational speed of the rotary kiln and is constant everywhere from the inlet to the outlet.

Therefore, the reaction between the dust and the reducing agent in the rotary kiln tends to be insufficient, and as a result, the reducing agent is discharged without being fully used for the reaction, resulting in a larger amount of reducing agent being consumed than necessary for the dust. , leading to an increase in processing costs.

Additionally, in order to improve dust processing efficiency, increasing the amount of dust charged per unit time will shorten the time it takes for the dust to pass through the kiln if the rotation speed of the rotary kiln is constant, which will slow down the reduction reaction. This results in insufficient recovery efficiency of useful metals.

In order to increase the movement time of the dust and reducing agent within the kiln in order to ensure sufficient reaction between the dust and reducing agent, it is recommended to reduce the rotational speed of the kiln or use a large rotary kiln. However, reducing the rotational speed of the kiln greatly reduces the amount of dust to be processed, and on the other hand, installing a large rotary kiln requires a large amount of equipment and operating costs.

[Purpose of the invention]

Therefore, an object of the present invention is to extract useful metals such as zinc and lead from the dust discharged from a metallurgical furnace for metal refining without wasting solid carbonaceous reducing agents and without requiring a large rotary kiln. The objective is to provide a method for efficient and economical recovery.

[Summary of the Invention] The present invention is directed to reducing dust discharged from a metallurgical furnace for metal refining, which mainly contains F''203+ ZnO and PbO, together with a solid carbonaceous reducing agent, into a reducing atmosphere that occupies most of the area including the inlet part. Charged from the inlet into a rotary kiln consisting of a belt and an oxidizing atmosphere zone including an outlet part,
The rotary kiln is moved from the inlet to the outlet, and placed in the J-type elemental atmosphere zone, where the zinc oxide and lead oxide in the dust are reduced and vaporized by the reducing agent, thereby converting zinc and lead. In a method for recovering useful metals from dust discharged from a metallurgical furnace for metal refining, the method comprises: separating and recovering useful metals from the dust discharged from the metallurgical furnace for metal refining,
By providing at least two ring-shaped dams on the inner wall of the rotary kiln, the inside of the rotary kiln is divided into at least two reducing atmosphere zones and one oxidizing atmosphere zone, and the inside of the rotary kiln is divided into at least two reducing atmosphere zones and one oxidizing atmosphere zone. By temporarily blocking the movement of the dust and the reducing agent by the at least two ring-shaped dams, the movement time of the dust and the reducing agent is kept at a minimum, thus reducing the zinc oxide and lead oxide in the dust. It is characterized by improving efficiency.

[Structure of the invention]

Next, the method of the present invention will be explained with reference to the drawings. FIG. 1 is a schematic longitudinal cross-sectional view of a rotary kiln used in the method of the present invention, and FIG. 2 is a cross-sectional view taken along the line II in FIG. 1. As shown in the drawing, the rotary kiln 1 is installed at a slope of, for example, 3/100, and a chute 2 for charging dust and solid carbonaceous reducing agent is arranged at its inlet 1a, and its outlet A burner 3 is arranged in 1b in a horizontal direction toward the inside of the rotary kiln.

A ring-shaped inlet dam 4 is provided on the inner wall of the inlet 1a of the rotary kiln, and a ring-shaped outlet dam 5 is provided on the inner wall of the outlet 1b. A ring-shaped first intermediate dam 6 is provided on the inner wall at a position approximately one-third of the total length of the rotary kiln 1 from the inlet 1a of the rotary kiln 1. A ring-shaped second intermediate dam 7 is provided on the inner wall at about two-thirds of the way.

In this way, the rotary kiln l has a first reducing atmosphere zone A between the inlet dam 4 and the first intermediate dam 6.
The area from the first intermediate dam 6 to the second intermediate dam 7 is the second
The area from the second intermediate dam 7 to the outlet dam 5 is divided into a reducing atmosphere zone B, and an acid f arsenic atmosphere 4'6C (. The temperature is maintained at about 650°C or less in the atmosphere zone A, rises to about 1200°C in the second reducing atmosphere zone B, and rapidly rises to about 1200°C or more in the oxidizing atmosphere zone C. Even if it is controlled like this.

A mixture of dust and solid carbonaceous reducing agent, which is continuously charged into the charging chute 2 from the yacht inlet 1a into the rotary kiln 1, passes through the first reducing atmosphere zone A in the rotary kiln 1 at its exit. 1b, reaches the first intermediate dam 6, and is dammed until it is deposited at the height of the first intermediate dam 6. In this way, when the mixture deposited in the first reducing atmosphere zone A exceeds the height of the first intermediate dam 6, the mixture moves into the second reducing atmosphere zone B.

As mentioned above, when the charging rate of the mixture charged into the rotary kiln 1 per unit time and the amount of the mixture overflowing the first intermediate dam 6 per unit time become approximately constant. , which is the maximum amount of the mixture deposited in the first reducing atmosphere zone A.

Since the mixture in the rotary kiln 1 moves spirally while being stirred up and down due to its rotation, the movement time of the mixture in the first reducing atmosphere zone A is increased by the damming of the first intermediate dam 6 mentioned above. do.

The temperature in the first reducing atmosphere zone A is controlled to be low so that the temperature near the first intermediate dam 6 is 500 to 650°C. Thus, the mixture of dust and solid carbonaceous reducing agent is sufficiently dried and heated to the temperature required for the reduction reaction due to the increased travel time described above. In this way, since the temperature inside the first reducing atmosphere zone A is controlled to a low temperature, the reduction of iron oxide in the dust by the solid carbonaceous reducing agent is suppressed. Therefore, consumption of the reducing agent in the first reducing atmosphere zone A is small, and the reducing agent can be used efficiently for reducing zinc oxide, lead oxide, etc. in the second reducing atmosphere zone B, which will be described later. I can do it.

The mixture of dust and solid carbonaceous reducing agent in the second reducing atmosphere zone B moves inside the second reducing atmosphere zone B toward the outlet 1b, as in the first reducing atmosphere zone A described above. move and reach the second intermediate dam 7, and the second intermediate dam 7
It is dammed up and accumulated until it reaches a height of , and when it exceeds the height of the second intermediate dam 7, it moves into the oxidizing atmosphere zone C. Therefore, by blocking the second intermediate dam 7 mentioned above, the second
The travel time in the reducing atmosphere zone B increases.

The temperature in the second reducing atmosphere zone B is controlled so as to rapidly rise to a high temperature of about 1200° C. near the second intermediate dam 7. Therefore, in the high temperature portion of the second reducing atmosphere zone B, zinc oxide, lead oxide, etc. contained in the dust are actively reduced and vaporized and separated from the dust. In this way, zinc, lead, etc. separated from the dust are reoxidized by the oxygen present in the space inside the rotary kiln, become zinc oxide and lead oxide again, and are discharged from the inlet 1a of the rotary kiln 1 together with the exhaust gas. Collected by dust collector. On the other hand, Fe2 contained in the dust
O3 is reduced to FeO in the second reducing atmosphere zone B.

The above-mentioned reaction is carried out very efficiently due to the increase in the movement time of the mixture of dust and solid carbonaceous reducing agent in the second reducing atmosphere zone B, and the solid carbonaceous reducing agent is effective for the above-mentioned reaction. consumed.

The temperature in the oxidizing atmosphere zone C is controlled to a high temperature by a burner 3 disposed horizontally toward the interior of the rotary kiln 1 at the outlet 1b, and the FeO reduced in the second reducing atmosphere zone B is reoxidized. be done. The oxidation heat generated at this time is also added, and the temperature in the oxidizing atmosphere zone C is 12
The temperature rises rapidly to over 00℃. As a result, the oxidizing atmosphere zone C
The temperature of the second reducing atmosphere zone B in the vicinity of the second reducing atmosphere zone B is increased, and the reductive vaporization of the zinc oxide, lead oxide, etc. described above is promoted.

Fe2O re-oxidized in the oxidizing atmosphere zone C.

is discharged from the outlet 1b of the rotary kiln 1 as clinker together with the residue in the dust.

Next, the following test rotary kiln, whose scale is 1/1000th that of an actual furnace, was used to examine the movement of dust within the furnace.

(1) Length: 2,400 mm (2) Diameter: 280 mm (3) Slope: 3/100 (4) Location of the first intermediate dam: 850 mm from the entrance (5) Location of the second intermediate dam: 9 from the first intermediate dam
00 position (6) Height of intermediate dam: 30mx (7) Number of rotations: 1. ORPM Add 100 g/m of test dust with a particle size of 1 to 'I mm to the above rotary kiln (equivalent to 6 T/H of an actual furnace).
When the supplied amount and the amount discharged from the rotary kiln become the same, that is, when an equilibrium state is reached, 100 g of colored dust with a particle size of 1 to 4 yen is added to the rotary kiln. /mm was supplied for 1 minute.

Then, the time from the charging of the test dust and colored dust to the start of discharge, the peak time of discharge of colored dust, etc. were investigated.

For comparison, a test rotary kiln of the same scale as above was used except that 1, 11, and 2 intermediate dams were not installed, and the time from charging the test dust and colored dust to the start of discharge was calculated in the same manner as above. We also investigated the emission peak time of colored dust.

3 and 4 are graphs showing the results of the above investigation, in which FIG. 3 shows the case where an intermediate dam is provided, and FIG. 4 shows the case where no intermediate dam is provided. As shown in Figure 3, middle 1'
When the T'jj dam is installed, the time a from charging the test dust to starting discharging is 102 minutes, the time from charging the colored dust to starting discharging is 55 minutes, and the time a from charging the test dust to starting discharging is 55 minutes. The time C from charging until the discharge amount reached its peak was 120 minutes.

On the other hand, as shown in Figure 4, the time a from charging the test dust to starting discharging when no intermediate dam is provided.
' is 47 minutes, the time b' from charging the colored dust to the start of discharge is 33 minutes, and the time C' from charging the test dust until the discharge amount of colored dust reaches its peak is 65 minutes. It was a minute.

As is clear from the above, the time from charging the test dust to the start of discharging when an intermediate dam is installed is more than twice that when the intermediate dam is not installed, and the color change when an intermediate dam is installed The time from charging the dust to the start of discharge and the time from charging the colored dust to the peak discharge amount were about twice as long as when no intermediate dam was provided. Furthermore, when examining the amount of test dust accumulated inside the rotary kiln, it was found that the amount of accumulated dust in the rotary kiln was 6.7 kg without an intermediate dam, but 1 kg with an intermediate dam installed.
1.6 kg, and approximately 1.7 without an intermediate dam.
It was double that.

Fig. 5 shows that when test dust and colored dust of 200 g/h (equivalent to 12 ff'/h of an actual furnace) are supplied to the rotary kiln equipped with an intermediate dam in the same manner as above, Fig. 6 shows that , the time from the charging of test dust and colored dust to the start of discharge when 200.9/kg of test dust and colored dust are supplied in the same manner as above to the rotary kiln which is not provided with an intermediate dam; This is also the result of investigating the peak time of colored dust emissions.

As shown in Figure 5, when an intermediate dam is installed,
The time a from charging the test dust to the start of discharge is 65 minutes, the time from charging the colored dust to the start of discharge is 43 minutes, and the amount of discharge from the charging of the colored dust reaches its peak. The time C required for this to occur was 73 minutes.

On the other hand, as shown in Fig. 6, the time a from charging the test dust to starting discharging when no intermediate dam is provided.
' is 36 minutes, the time b' from charging the colored dust to the start of discharge is 26 minutes, and the time C' from charging the colored dust until its discharge reaches its peak is 5 minutes.
It was 5 minutes.

As is clear from the above, the time from the charging of test dust to the start of discharge when an intermediate dam is provided is approximately 1.8 times that when no intermediate dam is provided; The time from the charging of colored dust to the start of discharge is approximately 1.6 times that of the case without an intermediate dam, and the time from charging of colored dust to the peak discharge amount is approximately 1.6 times. 3: It was double. Furthermore, when the amount of test dust accumulated in the rotary kiln was investigated, it was 11.1 kg without an intermediate dam, while it was 14.8 kg with an intermediate dam, which is approximately 1.1 kg with an intermediate dam. It was three times as much.

From the above, it can be seen that in the present invention, the first
It is clear that by providing the second intermediate dam, the time for the dust to move within the rotary kiln, that is, the amount of dust accumulated, increases, thereby improving the dust processing efficiency.

[Embodiments of the invention]

Next, the present invention will be explained with reference to examples. The electric furnace dust for temperature control having the component composition shown in Table 1 was granulated into particles with a particle size of about 10 mm using a granulator, and then dried to prepare d red.

The above-mentioned dust and lettuce and a solid carbonaceous reducing agent consisting of coke and coal were charged into a rotary kiln 1 having a length of 24,000 mm and an inner diameter of 2,800 mm as shown in FIG. Rotary kiln 1 has 85
A ring-shaped first intermediate dam 6 with a height of 300 mm is provided on the inner circumference at a position of 00 mm, and the first intermediate dam 6 is
A ring-shaped second intermediate dam 7 with a height of 300 mm was provided on the inner circumference at a position 9000 mm from the center.

One round of charging dust pellets costs 6,000 to 7,000k.
g/'H, and charging and soaking of solid carbonaceous reducing agent is 570 ~
It is 665 kg/H.

At the outlet 1b of rotary kiln 1, rotary kiln 1
From the burner 3 provided toward the inside of the rotary kiln 1, 28 to 30 kg of kerosene per ton of dust was blown into the rotary kiln 1 together with air and burned.

The temperature inside the rotary kiln 1 is the first reducing atmosphere zone A.
below 650°C, and the second reducing atmosphere zone B
The temperature is raised to nearly 1200℃ near intermediate dam 7,
In the oxidizing atmosphere zone C, the temperature was rapidly increased to 1200°C or higher.

As a result, the dust particles are sufficiently dried and heated in the first reducing atmosphere zone A at °C, and the dust pellets are sufficiently dried and heated in the second reducing atmosphere zone B.
Zinc oxide, lead oxide, etc. contained in the dust were reduced and vaporized, separated from the dust, and recovered. Also,
Fe, 03 in the dust was reduced to FeO. Then, in the oxidizing atmosphere zone C, FeO is reoxidized to Fe2O3, and due to the high temperature oxidation heat generated at that time,
After increasing the temperature of the second reducing atmosphere zone B in the vicinity of the oxidizing atmosphere zone C, it was discharged from the outlet 1b as talin containing iron oxide together with other residues.

The amount of dust containing zinc oxide and lead oxide recovered was 1500.
~1800 kg/H, and its component composition is as shown in Table 2.

Table 3 shows the amount of solid carbonaceous reducing agent used per ton of dust, the amount of dust processed per m3 per day in the rotary kiln, and the products of the method of the present invention and the conventional method without an intermediate dam. This is the recovery rate. In addition, Figure 7 shows the change in the amount of solid carbonaceous reducing agent used (kg/T), Figure 8 shows the change in the amount of dust processed (T/D/m''), and Figure 9 shows the change in the product recovery rate (%). It is a graph showing each transition.

As is clear from the above Table 3 and Figures 7 to 9, according to the method of the present invention, the amount of solid carbonaceous reducing agent used is reduced by 15 kg/T compared to the conventional method, and the amount of dust processed is lower than the conventional method. It increased by about 0.37 T/D/rrl.

The product recovery rate varied depending on the Zn concentration (15 to 20%) in the dust, but was 23 to 27%, which was an increase of about 4% as is clear from FIGS. 3 and 9.

In the above description, two intermediate dams are provided in the length direction of the rotary kiln, but the number is not limited to two, and three or more may be provided.

7...Second intermediate dam.

〔Effect of the invention〕

As described above, according to the present invention, useful metals such as zinc and lead can be efficiently and economically extracted from dust discharged from a metallurgical furnace for gold milling using a smaller amount of solid carbonaceous reducing agent than before. This results in excellent industrial effects that can be recovered.

[Brief explanation of drawings]

Fig. 1 is a schematic vertical sectional view of the rotary kiln used in the method of the present invention, Fig. 2 is a sectional view taken along the line I-■ in Fig. 1, and Figs. 3 to 6 show the state of dust retention in the rotary kiln. FIG. 7 is a graph showing changes in the amount of solid carbonaceous reducing agent used, FIG. 8 is a graph showing changes in the amount of dust treated, and FIG. 9 is a graph showing changes in product recovery rate. In the drawing,

Claims (1)

[Claims] Mainly Fe_2O discharged from a metallurgical furnace for metal refining
_3. Dust containing ZnO and PbO, together with a solid carbonaceous reducing agent, is charged from the inlet into a rotary kiln consisting of a reducing atmosphere zone that occupies most of the area including the inlet area, and an oxidizing atmosphere zone that includes the outlet area. The dust is moved inside the rotary kiln from the inlet to the outlet, and in the reducing atmosphere zone, zinc oxide and lead oxide in the dust are reduced and vaporized by the reducing agent, and the zinc and lead are removed from the dust. In a method for recovering useful metals from dust discharged from a metallurgical furnace for metal refining, the method includes: separating and recovering useful metals from dust discharged from a metallurgical furnace for metal refining;
By providing at least two ring-shaped dams on the inner wall of the rotary kiln, the inside of the rotary kiln is divided into at least two reducing atmosphere zones and one oxidizing atmosphere zone, and the at least two reducing atmosphere zones By temporarily stopping the movement of the dust and the reducing agent in the dust by the at least two ring-shaped dams, the movement time of the dust and the reducing agent is kept long, and thus the zinc oxide and the reducing agent in the dust are A method for recovering useful metals from dust discharged from a metallurgical furnace for metal refining, characterized by improving lead reduction efficiency.