JP2003027152A - Method for operating smelting reduction furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase concentration of high volatility metal recovered from furnace top gas by suppressing exhaust of fine powder of carbonaceous solid reducing agent and ash content from the furnace top. SOLUTION: In a smelting reduction furnace 1 which produces molten metal by injecting powdery and granular metallic oxide containing-raw material into the smelting reduction furnace 1 having tuyeres 3, 4 arranged in at least two steps at the upper and the lower parts for blowing high temperature oxygen- enriched air into a packed layer of the carbonaceous solid reducing agent 2, from at least the upper step tuyere 3 and further, cools the furnace top gas at the outside of the furnace to separate and recover the high volatility metal, the grain diameter of bulky raw material and/or bulky auxiliary material charged from the furnace top part is made smaller than the grain diameter of the carbonaceous solid reducing agent.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ore, dust, or the like from a tuyere of a solid reducing agent packed bed type smelting reduction furnace filled with a carbon-based solid reducing agent such as coke. The present invention relates to a method of operating a furnace in which a granular material such as sludge is blown, a gas at a furnace top is cooled outside the furnace, and a highly volatile metal such as zinc is separated and recovered. [0002] In recent years, the amount of generated iron scrap containing zinc, such as surface-treated steel sheets for automobiles, has been increasing. In an electric furnace and the like using this iron scrap as a main raw material, zinc and iron are used. Dust as a main component is generated. This dust is currently
Due to the high cost of collection, after dust collection, it is treated to make it harmless and then landfilled. [0003] Incidentally, the content of zinc contained in the electric furnace dust is 10 to 30%, and the same amount of iron is also contained. The form of zinc and iron is oxide or hydroxide, but the amount of dust generated is as large as 15 kg per ton of steel, and it is low-cost and completely separated without waste. There is a need for technology to do this. [0004] As an example of such a separation and recovery technique, there is a method described in Japanese Patent Application Laid-Open No. 8-325646 as an operation method for performing the operation in a vertical furnace filled with a solid reducing agent such as coke. In this furnace operation method, at least two upper and lower tuyeres are provided in a solid reducing agent packed bed type smelting reduction furnace that fills a solid reducing agent, and zinc-containing powdery raw materials such as electric furnace dust are supplied from the upper tuyeres. The molten iron is melted and dropped on the hearth, zinc evaporates and rises to the furnace top, and the gas at the furnace top is cooled outside the furnace to separate and recover highly volatile metals such as zinc. It is to do. However, in the above-mentioned conventional furnace operating method, fine powder or ash of a solid reducing agent such as coke is apt to be mixed into the gas at the furnace top, and if the coke ratio increases due to fluctuations in operating conditions, the coke is recovered accordingly. The problem is that the mixing ratio of the highly volatile metal such as zinc and the fine powder or ash of the solid reducing agent changes, and the concentration of the recovered highly volatile metal decreases. As a method for addressing this problem, Japanese Patent Laid-Open No.
There is a method described in 00-192125. This prevents the fine powder and ash of the carbon-based solid reducing agent from scattering at the furnace top by setting the gas flow rate at the furnace top to 1.5 m / s or less. As a method of adjusting the flow rate of the furnace top gas, there are a method of adjusting the furnace diameter in advance at the time of construction, and a method of adjusting the gas amount by changing the oxygen enrichment rate of the gas blown from the tuyere during operation. However, when the operation is performed at a gas flow rate of 1.5 m / s at the furnace top, particles having a particle diameter of 300 μm or less are discharged out of the furnace together with gas. As a result, among the fine powder and ash of the carbon-based solid reducing agent, particularly those having a fine particle size and a part of the blowing material are discharged out of the furnace together with the furnace top gas and mixed with the recovered highly volatile metal. Will be lost. Also,
Once the equipment is constructed, the furnace diameter and the like cannot be easily changed. Therefore, when the amount of dust treatment is to be increased, a case in which the furnace top gas flow rate is limited may occur. Accordingly, the present invention has been developed to solve the above-mentioned problems. The present invention provides an environment in which fine powder and ash of a carbon-based solid reducing agent are difficult to be discharged from a furnace top, thereby recovering from a furnace top gas. It is an object of the present invention to provide a method of operating a furnace for increasing the concentration of a highly volatile metal. In order to achieve the above object, a method for operating a smelting reduction furnace according to the present invention comprises at least a step of blowing high-temperature oxygen-enriched air into a packed bed of a carbon-based solid reducing agent. A molten metal is produced by blowing a powdered metal oxide-containing material from at least the upper tuyere into a smelting reduction furnace having tuyeres provided in two stages, and cooling the gas at the furnace top outside the furnace. A method for operating a smelting reduction furnace for separating and recovering highly volatile metals, wherein the particle size of the bulk material and / or bulk auxiliary material charged from the furnace top is smaller than the particle size of the carbon-based solid reducing agent. It is characterized by having done. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a vertical smelting reduction furnace to which the furnace operating method of the present invention is applied (hereinafter, simply referred to as a vertical furnace).
It is. This vertical furnace 1 is filled with a carbon-based solid reducing agent 2 such as coke, and constitutes a solid reducing agent packed bed smelting reduction furnace as a whole. The vertical furnace 1 is provided with at least two upper and lower tuyeres. As described above, examples of the vertical furnace 1 in which the tuyeres 3 and 4 are provided in upper and lower two stages include, for example, a furnace developed for efficiently melting chromium ore. In other words, when the upper tuyere 3 alone does not provide sufficient heat for smelting reduction,
The calorific value is supplemented from the tuyere 4 in the lower stage, and the molten metal is sufficiently melted and reduced during that time. The number of tuyeres 3 and 4 is set based on the required reducing capacity and melting capacity. Hot air and oxygen-enriched air are blown into these tuyeres 3 and 4 from blower 5 through hot air generating furnace 6 as blowing gas. In addition to the blowing gas, a raw material is blown into the upper tuyere 3 from a raw material blowing device 7. The raw material blown into the furnace from the upper tuyere 3 is, in principle, limited to a granular material, and melts, burns, reduces, and evaporates immediately after blowing. Of these raw materials, the oxides and hydroxides of the low-volatile metals such as molten iron are reduced in the process of dropping the packed bed of the solid reducing agent 2 and accumulate in the hearth. The vapor of the highly volatile metal such as zinc that evaporates rises to the furnace top through the gap of the solid reducing agent 2 and is discharged together with the furnace gas. Powdery and granular raw materials such as electric furnace dust, which is zinc-containing dust, is blown from the upper tuyere 3 in principle. The powdery material is light, so when it is charged from the furnace top,
Due to the ascending current in the furnace, for example, as described above, the low-volatile metal is sufficiently melted and blown off before dripping in the packed bed of the solid reducing agent 2, and is discharged from the furnace top as it is. The raw material is blown from the tuyere 3 in the upper stage in order to suppress the generation of the gas. In other words, the powdery raw material immediately melts, burns, and evaporates in a space (hereinafter referred to as a “resway”) in front of the upper tuyere 3 to be blown. On the other hand, since a lump of raw material such as iron scrap is heavy, it does not blow off even if it receives a rising air current in the furnace. In addition, since this kind of massive raw material does not need to be instantaneously melted in front of the tuyere as described above, the raw material is charged from the furnace top by the furnace top charging device 8 in principle. In addition, as described later, in the present embodiment, the temperature of the furnace top needs to be maintained at a high temperature, whereas when a large amount of the bulk charge is charged at once, the temperature of the furnace top decreases too much. As a rule, the bulk charge is charged continuously in small quantities in principle so that the temperature at the furnace top does not drop. Specifically, it is preferable to continuously charge a small amount at a time by a charging pipe system from the furnace top. It should be noted that a sufficient amount of heat can be obtained even if a large amount of bulk charging material is charged at a time, and that the furnace top temperature be maintained high. However, such a unit increases the fuel consumption rate and should be avoided. In this embodiment, in order to keep the temperature of the furnace top high, a secondary combustion gas is supplied to the space of the furnace top and intentionally burned in the furnace top. The secondary combustion gas is also supplied to the duct for discharging the exhaust gas from the furnace top and burned in the duct. The exhaust gas discharged from the furnace top in this way is supplied to an exhaust gas cooling / cleaning device 9.
Sent inside. The exhaust gas cooling / cleaning device 9 is specifically a wet cooling device, that is, a liquid is sprayed in the exhaust gas to lower the temperature of the exhaust gas, and a substance in a vapor state is cooled and solidified, and is dripped together with the liquid. Precipitation is performed so that it can be separated and recovered as a slurry, and gas that does not liquefy or solidify is collected as a gas. In this embodiment, a highly volatile metal such as zinc is solidified and separated and recovered from the exhaust gas, and the discharged exhaust gas is obtained as a high-calorie fuel gas containing carbon monoxide gas. Further, by rapidly cooling the high-temperature exhaust gas in this way, it is possible to prevent re-synthesis of dioxin which is a harmful substance contained in the raw material. next,
The conditions for stabilizing the zinc concentration in the slurry (product) recovered by the exhaust gas cooling / cleaning device will be described. First, FIG. 2 shows the particle size distribution of the recovered product, and Table 1 shows the results of component analysis at each particle size. [Table 1] As is apparent from the above, the zinc in the recovered product is a substance vaporized in front of the tuyere and re-solidified in the quenching tower, so that the zinc concentration in dust having a small particle diameter is high. On the other hand, those having a large particle diameter of 0.4 mm or more have a high ratio of C and gangue components of 80% or more, and carbon,
That is, the main component is fine powder or ash of the solid reducing agent. Therefore, in order to increase the zinc concentration in the recovered product, it is necessary to suppress the emission of fine powder of the solid reducing agent and dust having a large particle diameter derived from ash outside the furnace. These dusts, unlike zinc vapor, are discharged outside the furnace through the gap between the packed beds from the tuyere in a solid state, unlike zinc vapor. Therefore, the smaller the diameter of the packing particles, the smaller the amount of dust passing through the packing layer.
Referring to FIG. 3, the particle diameter x that can pass through the packed bed of solid reducing agent 2 is (r + x): r = 2: √3, assuming that the particles are spherical. Is 0.15 times the packed particle diameter r. However, since the gas actually passes between the filled particles on a gas, the particle diameter is about 0.1 times the filled particle. I know I can get through. Therefore, the particle diameter r of the solid reducing agent 2 is set to 4
If the particle size is reduced to about mm, the emission of dust having a particle diameter of about 0.4 mm, which is a problem, can be prevented, but in this case, the liquid permeability of the melt generated in front of the tuyere deteriorates, and In addition, there is a danger that the pressure loss in the furnace may increase and cause a malfunction. Here, the present inventors have conceived to reduce the particle size of the charge other than the solid reducing agent charged from the furnace top, that is, the flux (bulk auxiliary material) and / or the bulk material. Since the flux and the bulk raw material are melted in front of the tuyere and dropped into the packed bed, the liquid permeability at the lower part of the upper tuyere is not deteriorated even if the particle diameter is reduced. Further, the melting property in front of the tuyere can be improved by reducing the particle diameter. Therefore,
When the particle size of the solid reducing agent was kept constant and the particle size of the other furnace top charge was reduced, the amount of dust discharged from the outside of the furnace could be reduced, and the zinc concentration in the recovered product Could be greatly improved. At this time, there was no deterioration in liquid permeability at the lower part of the furnace or a large increase in pressure loss at the shaft part on the tuyere, and stable operation could be continued. Hereinafter, the present invention will be described in detail with reference to examples. An operation experiment was performed using a smelting reduction furnace having a processing amount of a metal oxide of 30 t / day. The used oxide raw material is electric furnace dust generated from electric furnace factory,
Includes metal oxides such as iron and zinc. Table 2 shows the composition of the raw materials used. [Table 2] The operating conditions of the smelting reduction furnace are as follows: total air flow (total of upper and lower tuyeres) of 1900 Nm ³ / hr, oxygen enrichment to upper tuyeres of 260 Nm ³ / hr, lower tuyeres Based on an enriched oxygen amount of 40 Nm ³ / hr, a blowing temperature of 700 ° C., and a raw material blowing rate of 1040 kg / hr (25 t / d). As the charge from the furnace top, in addition to coke as a carbon-based solid reducing agent, quartzite and limestone are used as fluxes. Table 3 shows the particle size of each. [Table 3] Conventionally, the particle diameters of coke and flux have been made substantially the same in consideration of the solid flow in the shaft and the like. As a result, the zinc concentration in the recovered product was about 50%. Therefore, both limestone and silica stone were gradually reduced in particle size before the operation. As a result, as shown in Table 3, it was confirmed that the zinc concentration in the recovered product increased as the particle diameter of limestone and silica stone decreased. FIG. 3 shows the particle size distribution of the recovered product in Example 3 in which the particle diameter was reduced to about 5 mm.
Particles having a particle diameter of 4 mm or more disappeared, confirming the effect of the present invention. In addition, under these conditions, there was no significant change in the pressure loss in the furnace and the tapping residue, so it was confirmed that the present invention can improve the zinc concentration in the recovered product without deteriorating the furnace condition. Was. As is apparent from the above description, according to the present invention, the fine powder and ash of the carbon-based solid reducing agent can be made difficult to be discharged from the furnace top, so that they can be recovered from the gas at the furnace top. The concentration of the highly volatile metal that is obtained can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram schematically showing a smelting reduction furnace. FIG. 2 is a graph showing the particle size distribution of a conventional recovered product. FIG. 3 is a diagram schematically showing the size of a spherical particle that can pass through a gap between the filler particle and the filler particle. FIG. 4 is a graph showing a particle size distribution of a recovered product when the present invention is carried out. [Description of Signs] 1 ... vertical furnace (melting reduction furnace) 2 ... packed bed of carbon-based solid reducing agent 3 ... upper tuyere 4 ... lower tuyere

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22B 5/10 C22B 19/04 7/00 19/32 19/04 B09B 3/00 303L 19/32 ZAB 304G (72) Inventor Shinichi Masumoto 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. 4D004 AA02 AA37 BA05 CA29 CA37 CC11 4D059 AA00 BB04 CC07 DA58 4K001 AA10 AA30 BA05 BA14 DA05 EA01 GA01 GB01 GB03 GB09 HA01 JA01 4K012 CB02 CB06 CB07

Claims (1)

Claims: 1. A powdery and granular metal is placed in a smelting reduction furnace having at least two upper and lower tuyeres that blow high-temperature oxygen-enriched air into a packed bed of a carbon-based solid reducing agent. A method for operating a smelting reduction furnace for producing molten metal by injecting an oxide-containing raw material from at least the upper blade □ and cooling the gas at the top of the furnace outside the furnace to separate and recover highly volatile metals, comprising: A method for operating a smelting reduction furnace, wherein the particle size of the bulk material and / or the bulk auxiliary material charged from above is made smaller than the particle size of the carbon-based solid reducing agent.