JPH10273740A - Method for recovering valuable metal from powdery wet raw material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remarkably reduce the thermal load needed to vaporize water and decompose powdery wet raw material in a smelting reduction furnace by regulating the exhaust gas temp. after heat-exchanging to a specific value or higher, at the time of drying the powdery raw material while executing the heat exchange with the powdery wet raw material containing metal high in vaporizing pressure by utilizing the exhaust gas sensible heat in a vertical type smelting reduction. SOLUTION: The exhaust gas generated in the vertical type smelting reduction furnace 1 is supplied to an exhaust gas piping 5 arranged in a heat exchanger 4 through a cyclone 14 and metallic sludge, etc., containing valuable metal is brought into contact with the heated piping surface to dry and remove the moisture contained in the metallic sludge, etc. At this time, the exhaust gas temp. after heat-exchanging, is made to >=800 deg.C and the dried metallic sludge is transported to a powder injecting device 8 through a hopper 6 for dried sludge and a hopper 7 for discharging and injected from upper step tuyeres 9 in the vertical type smelting reduction furnace 1 and smelted. By this method, the metallic sludge can be dried within the wide range of about 10-50% water without casing the problem such as the sticking of low m.p. metal in the heat exchanger 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering valuable metals from wet powdery raw materials using a vertical smelting reduction furnace having tuyeres provided in upper and lower stages, and containing a low melting point metal such as zinc and lead. The present invention relates to a technique for recovering valuable metals from powdery wet raw materials such as metal sludge.

[0002]

2. Description of the Related Art In recent years, it has been said that it is necessary to collect and recycle valuable resources from the viewpoint of effective use of resources and energy saving.
Various approaches have been reported. The mainstream of the current method of manufacturing steel products in Japan is the blast furnace-converter method. The blast furnace-converter method consists of a steelmaking process, a steelmaking process, a rolling process and a subsequent secondary processing process, and various dust, slag,
Sludge etc. are generated. Efforts are being made to collect valuable metals from dust, slag, and sludge, or to manufacture by-products.However, the current situation is not always sufficient. Is difficult.

[0003] A problem associated with the recycling of iron scrap is the problem of electric furnace dust treatment. In electric furnace dust, chromium, cadmium, lead and other elements that elute out when landfilled and cause environmental pollution are several percent, and zinc content is 1%.
It contains about 0 to 40% and about 25 to 50% of iron. These are treated and recycled, that is, inexpensive fixation of harmful metals such as chromium and recovery and recycling of valuable metals such as Zn and Fe. Technology was desired.

[0004] The present inventors have addressed the problem of electric furnace dust treatment, and disclosed in Japanese Patent Application Laid-Open No. 7-173548, for zinc-containing dusts such as electric furnace dust.
In a vertical smelting reduction furnace having a packed bed of carbon-based solid reducing agent,
Zinc-containing dust such as zinc-containing dust is blown through the tuyere to reduce and evaporate the zinc content in the dust, while recovering zinc by cooling the exhaust gas containing the evaporated zinc vapor outside the furnace. Has been disclosed. further,
At this time, while the zinc-containing dust is being blown, the furnace temperature of the vertical smelting reduction furnace is maintained at 600 ° C. or higher, or the furnace temperature of the vertical smelting reduction furnace is changed to the exhaust gas generated in the furnace. A technology has been developed that can efficiently recover zinc from zinc-containing dust by adjusting a plurality of combustion lances for secondary combustion.

[0005] A vertical smelting reduction furnace is one in which a strong reducing power is realized by installing a two-stage tuyere in a coke packed bed, and a metal sludge containing valuable metals as hydroxides or oxides. Considering that it is suitable for the treatment of slag, treatment of metal sludge using a vertical smelting reduction furnace was studied. As a result of the examination, the biggest problem was the moisture in the metal sludge. In other words, the substance to be treated in the vertical smelting reduction furnace must basically be a dry powder, and when the moisture of the metal sludge is brought into the smelting reduction furnace, it evaporates and decomposes water in the furnace. Two reasons are that a large amount of heat is required and the thermal load is significantly increased. For this reason, a drying method for metal sludges using the exhaust gas of a vertical smelting reduction furnace was studied.

[0006] Both direct heating, in which exhaust gas and sludge are in direct contact, and indirect heating, in which heat is exchanged through partition walls, were studied. First, as a direct heating method, as shown in FIG. 3, metal sludges were charged into a fluidized bed type drying apparatus for introducing exhaust gas from a vertical smelting reduction furnace and dried. In this case, the configuration is the same as that of the fluidized bed pre-reduction using the sensible heat and reducing power of the exhaust gas generated in the smelting reduction furnace, but the drying result was that sludge could be dried, but zinc, lead, and sodium in the exhaust gas Low melting point metals such as potassium, cadmium, etc. migrate to the sludge side in the drying unit, and the low melting point metal originally contained in the metal sludge and the low melting point metal newly added in the drying unit It was found that the vapor of the low-melting metal in the exhaust gas was condensed in the drying device and circulated in a cycle of shifting to the metal sludge again. In this method, the low melting point metal is not discharged out of the system and cannot be recovered as valuable metal.

[0007] Also, when the latent heat (combustion heat) of the exhaust gas is used as the direct heating of the sludge, no fundamental improvement in the emission of low melting point metals has been made. When the exhaust gas passes through the heat exchange pipe pipe arranged in the drying device as indirect heating, there is a problem that the low-melting-point metal adheres and grows on the pipe inner surface, eventually leading to blockage. there were.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to dry powdery raw materials such as metal sludge using the exhaust gas of a vertical smelting reduction furnace, and (1) circulate the low melting point metal in the system. (2) to solve the problem that the low melting point metal adheres to and grows on the inner surface of the pipe for heat exchange and eventually causes the pipe to be clogged. Accordingly, an object of the present invention is to realize the recovery of valuable metals from metal sludge.

[0009]

SUMMARY OF THE INVENTION The present invention provides a carbon material-filled bed,
A vertical smelting and reducing furnace for recovering valuable metals from powdered wet raw materials containing metals with high vapor pressure using a vertical smelting and reducing furnace having a plurality of tuyeres provided in upper and lower stages that blow high-temperature air. Using the sensible heat of flue gas of the exhaust gas to raise the temperature of the flue gas after heat exchange with the wet powder material to 800 ° C. or higher, drying the wet powder material, and blowing the dry powder material from at least the upper tuyere. Of valuable metals from coal. Here, the carbonaceous material refers to a carbon-based solid reducing agent made of coke or coal or both.

[0010] The heat exchange is performed by indirect heating to prevent the metals from depositing and fixing inside the indirect heating device from exhaust gas containing metals having a high vapor pressure. Also, with direct heating,
By setting the temperature of the powder raw material after the heat exchange to 600 ° C. or higher, entrainment of the low-melting-point metal is eliminated, and metal having a high vapor pressure is prevented from circulating in the system. The reason why the temperature of the exhaust gas after the heat exchange is set to 800 ° C. or more is to prevent accumulation of the low-melting-point metal contained in the metal sludge in the system and to precipitate, sink, and pipe in the heat exchanger for indirect heating. This is to eliminate problems such as road blockage and discharge the low-melting metal to the outside of the system together with the exhaust gas.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the equipment configuration used to realize the present invention. The vertical smelting reduction furnace 1 is formed with a packed layer 2 of a carbon-based solid reducing agent (hereinafter referred to as carbonaceous material) composed of coke or coal or both, and the carbonaceous material is supplied from a carbon material hopper 3 It is supplied and charged into the furnace so as to maintain a predetermined stock line at the furnace top of the vertical smelting reduction furnace 1.

A pipe 5 through which the exhaust gas generated in the vertical smelting reduction furnace 1 flows is disposed inside the heat exchanger 4, and the metal sludge supplied to the heat exchanger 4 is heated to a high temperature by a pipe. Heated on the surface, the moisture contained in the metal sludge is dried and removed. The dried metal sludge is supplied to the hopper 6
Then, the powder is blown from the powder blowing device 8 into the upper tuyere 9 of the vertical smelting reduction furnace 1 via the hopper 7. Further, when melting the powdery metal sludge, the smelting solvent for limestone and silica stone added for the purpose of adjusting the viscosity and melting point of the slag is supplied at a predetermined ratio by the powder blowing device 8 to the metal sludge. A suitable amount is cut out and blown into the upper tuyere 9 of the vertical smelting reduction furnace 1.

The blown air is heated to 800 to 1000 ° C., and is blown as hot air into the vertical smelting reduction furnace 1 from the upper tuyere 9 and the lower tuyere 10 through a blower tube.
At that time, an appropriate amount of oxygen is enriched in the hot air as needed. The hot air burns the carbonaceous material in the vertical smelting reduction furnace 1. By the combustion heat and the reducing gas generated at that time, the metal sludge blown into the upper tuyere 9 is melted, the oxides and hydroxides in the metal sludge are reduced, and the low-melting metals are turned into steam, It is discharged from the furnace top through a packed bed of carbonaceous material. At this time, a plurality of secondary combustion lances 11 are installed at the furnace top for the purpose of raising the temperature of the upper portion of the packed bed, and the exhaust gas is burned. The vapor of the melting metal can be discharged from the duct at the top of the furnace.

Further, the oxides or hydroxides of iron, chromium, and nickel in the metal sludge are melted in the tuyere tip raceway of the upper tuyere 9 by the heat of combustion of the carbonaceous material. The packed layer 2 descends toward the lower tuyere 10.
In the process, the gas is brought into countercurrent contact with the reducing gas generated at the tuyere tip of the lower tuyere 10 and reduced, and at the same time, comes into contact with the carbon material of the carbon material packed layer 2 in the middle of dripping and is directly reduced. Separate into metal and slag. Then, the molten metal finally accumulated in the hearth is discharged from the tap hole 12 and the slag is discharged from the slag port 13, and at the same time, chromium and the like are fixed in the molten metal and made harmless.

The gas supplied to the heat exchanger 4 is provided by a cyclone 14 on the exhaust gas discharge side of the vertical smelting and reducing furnace 1, and the carbon which is generated by the carbon material among the dust that has flown out of the vertical smelting and reducing furnace 1. After collecting relatively coarse dust of about 10 μm or more including the carbon and separating most of the carbon contained in the dust, the whole or a part thereof is branched and supplied to the vertical smelting reduction furnace 1. It is what was constituted. By installing a cyclone, accumulation of foreign substances in the pipe 5 arranged inside the heat exchanger, or clogging of the pipe by foreign substances is avoided. Dust mainly composed of carbon passes through a dust storage hopper 15 and a part of the collected dust is blown into an upper tuyere 9 of the vertical smelting reduction furnace 1 using a dust transport device 16. Then, part of the dust in the dust storage hopper 15 opens and closes the valves 17a and 17b, and is discharged out of the system via the dust discharge hopper 18.

Here, the drying of metal sludge will be described. In the method of the present invention, the temperature of exhaust gas is constantly measured at the exit side of the heat exchanger, and the temperature is maintained at 800 ° C. or higher to reduce the smelting content contained in the metal sludge. Low-melting-point metal vapor which has been reduced and volatilized in the furnace and transferred into the exhaust gas can be prevented from adhering to the inside of the pipe. Here, the reason why the exhaust gas temperature was set to 800 ° C. or higher on the exit side of the heat exchanger is that if the temperature was lower than 800 ° C., adhesion of the low-melting metal vapor to the inside of the pipe could not be prevented. In particular, when the operation is continued for a long period of time, the low-melting-point metal vapor adheres to the inside of the pipe and grows in a layered form. Once adhered, it is strong and difficult to remove. The temperature is desirably higher than 800 ° C. for preventing adhesion.

Next, temperature compensation of the exhaust gas is performed as an adhesion preventing operation. Specifically, (1) increase the flow rate of the exhaust gas branched for drying the metal sludge (2) burn the auxiliary fuel (3) There are methods such as supplying oxygen to the exhaust gas and burning the exhaust gas, and an appropriate method may be selected from these methods.

The gas after the heat exchange in the cooling tank 5 is introduced into a dust remover 19 and sprayed directly with water from a water spray pipe 20 to recover and cool the low melting point metal mainly composed of Zn in the exhaust gas. Is suspended in the cooling water in the dust remover 19 and stored as a slurry liquid 21. Exhaust gas after dust removal cooled to 200 ° C. or lower by water spray is sent out of the system. The level of the slurry liquid 21 in the dust remover 19 is controlled by using a level meter 23 and a flow control valve 24. The dust mainly composed of Zn is transported as a slurry liquid 21 to a dehydrator 25 using a slurry pump 22 and has a slurry concentration of 40 to 50%.
After dehydration in the range of 80%, the Zn content is discharged to the container 27 as a oxidized slurry via the slurry transport device 26.

Further, the effluent of the dehydrator 25 is sent to a sedimentation tank 28 to sediment solids such as dust contained in the effluent to some extent, and a treated water 29 from which most of the solids have been removed is supplied to a treated water pump 30. Circulates through the water spray pipe 20 to the dust remover 19. In FIG. 1, the exhaust gas generated in the vertical smelting reduction furnace 1 may be directly guided to the dust remover 19.
In this case, the equipment can be simplified by omitting the cyclone 14 and the dust storage hopper 15.

Further, as a method for recovering the product, a wet recovery method shown in FIG. 1 in which water is directly sprayed on the exhaust gas using a water spray to cool the exhaust gas and recover dust containing zinc from the exhaust gas is used. On the other hand, the dry recovery method shown in FIG. 2 may be used. That is, in FIG. 2, the cyclone dust collecting device 14, the indirect cooling type dust remover 31, and the bag filter 33 are arranged at the subsequent stage of the vertical smelting reduction furnace 1. Dust remover 3
Introduced in 1. A cooling water pipe 32 is provided inside the dust remover 31.
The high-temperature gas or dust is cooled to about 200 ° C. or lower by heat exchange between the sensible heat and cooling water of the high-temperature gas and dust, and then sent to the bag filter 33. Then, the cooled dust accumulated in the dust remover 31 and the bag filter 33 is cut out from the transport device 35 using the cut-out devices 34a and 34b, and is discharged out of the system. The exhaust gas is exhausted out of the system from the exhaust pipe 36 and collected as a by-product gas.

[0021]

EXAMPLES Using a vertical smelting reduction furnace having the following specifications and shown in FIG. 1, an operation test of metal sludge treatment was conducted on metal sludges having the composition shown in Table 1. (1) Smelting reduction furnace Furnace diameter: 1.2 m, height: 8.0 m, tuyere: upper and lower three each (2) Ventilation conditions Ventilation amount: 1500, 1600 Nm ³ / hr, ventilation temperature;
900 ° C Enriched oxygen content; 200 Nm ³ / hr (3) Powder injection Mixing ratio: Metal sludge 90% (dry space) Solvent (limestone + silica stone) 10% Injection amount: 800 kg / hr (metal sludge, dry base) (4) Mixing of metal sludge and water mixing; sludge A: sludge B: sludge C: sludge D = 3: 3: 3: 1 average sludge water content: 10, 20, 30, 50% by weight (external number) 90-93% Fe, 1-2%
Si, 4.0 to 4.3% C, 0.8 to 1.2% Mn,
It was pig iron containing 0.6 to 0.9% Cr. The slag composition is 24 to 27% SiO ₂ , 16 to 24%, Al _{2
O 3, 22~25% CaO, 2.3~2.6} % MgO,
It was 5.7 to 6.8% MnO.

Table 2 shows the test results. In order to make the operating conditions of the smelting reduction furnace uniform, the blowing amount of metal sludge was adjusted. The sludge moisture is a value in an operation test after mixing four types of sludge. As shown in Table 1, the original water content of the sludge is 30-70%, but it is 10-50% for the test.
Dewatered and adjusted to%. Table 2 shows an invention example and a conventional example. In the example of the present invention, the temperature of exhaust gas after heat exchange with
By setting the temperature to 0 ° C. or more, the metal sludge could be dried in a wide range of water content of 10 to 50% without causing a problem such as adhesion of a low melting point metal in the heat exchanger. When the exhaust gas temperature is 8
Since the temperature is set to 00 ° C. or higher, it is necessary to supply the entire amount of the exhaust gas to the heat exchanger and burn a part of the exhaust gas under the condition of high moisture. On the other hand, under conditions of low moisture, it was sufficient to introduce a part of the exhaust gas into the heat exchanger. On the other hand, the comparative example was carried out using the apparatus shown in FIG. 3 at a sludge moisture of 10%. However, as a result of condensation of the low melting point metal in the heat exchanger, fluidization and introduction and removal of the sludge were performed. Did not work, resulting in the supply of all of the exhaust gas. Furthermore, the results after drying also showed large variations, and the difference from the examples of the present invention was apparent.

In the case of sludge treatment that does not contain elements having a high vapor pressure such as zinc and lead, the temperature of the exhaust gas at the heat exchanger outlet is reduced to 80%.
There is no problem if the temperature falls below 0 ° C.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

According to the present invention, in the operation of treating metal sludge using a vertical smelting reduction furnace and recovering low melting metal and separating and recovering it as hot metal and slag, the vertical smelting reduction furnace is used for drying metal sludge. Effective utilization of the sensible heat of the exhaust gas generated in the furnace, the moisture introduced into the smelting reduction furnace is removed in advance by drying the metal sludge, and the thermal burden required for evaporation and decomposition of the moisture in the smelting reduction furnace Is significantly reduced.

The energy efficiency of the entire processing system is improved, and as a result, it is effective in suppressing carbon dioxide gas. Further, as apparent from the principle, application of the present invention does not prevent application to other than metal sludge. In the process of recovering valuable metals from water-containing dust containing low-melting-point metals and the processing of slurry-type dust obtained by wet dust collection, such as occurs when water is previously washed as dechlorination of electric furnace dust. It is clear that similar excellent results can be obtained.

[Brief description of the drawings]

FIG. 1 is a process flow diagram of an embodiment of the present invention.

FIG. 2 is an example of a process flow suitable for the present invention.

FIG. 3 is a process flow diagram of a comparative example.

[Description of Signs] 1 vertical smelting reduction furnace 2 packed bed of carbon-based solid reducing agent 3 hopper for carbon material 4 heat exchanger 5 exhaust gas pipe arranged inside heat exchanger 6 hopper for dried sludge 7 dried sludge Discharge hopper 8 Powder blowing device 9 Upper tuyere 10 Lower tuyere 11 Secondary combustion lance 12 Tap hole 13 Slag outlet 14 Cyclone 15 Dust reservoir hopper 16 Dust transport device 17a, 17b Valve 18 Dust discharge hopper 19 Dust removal 20 Water spray pipe 21 Slurry liquid 22 Slurry pump 23 Liquid level gauge 24 Flow control valve 25 Dehydrator 26 Slurry transport device 27 Container 28 Precipitation tank 29 Treated water 30 Treated water pump 31 Indirect cooling type dust remover 32 Cooling water pipe 33 Bag filter 34a, 34b Cutting device 35 Transport device 36 Exhaust pipe 37 Smelting solvent 38 Hot air

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Yoshiaki Hara 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Co., Ltd. (72) Inventor Hiroshi Itaya 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Research Institute

Claims (2)

[Claims] 1. Use of a vertical smelting reduction furnace having a plurality of tuyeres provided in two upper and lower stages into which a carbon material-filled layer and high-temperature air are blown, to convert valuable metals from a powdery wet raw material containing a metal having a high vapor pressure. At the time of recovery, the exhaust gas temperature after heat exchange with the powder wet raw material is set to 800 ° C. or higher using the exhaust gas sensible heat of the vertical smelting reduction furnace to dry the powder wet raw material, and the dried powder raw material is blown from at least the upper tuyere. A method for recovering valuable metals from a wet powder raw material. 2. The method according to claim 1, wherein the heat exchange is indirect heating.