JP2000192125A - Operation of furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve and stabilize the concentration of zinc recovered from furnace top gas when the zinc and iron are separated and recovered from an electric furnace dust. SOLUTION: In the case of recovering the zinc, by using two stages of tuyeres at the upper and the lower stages, filling coke, charging raw material of the electric furnace dust through the upper stage of the tuyere and cooling the gas in the furnace top part at the outside of the furnace, e.g. the blasting quantity into the tuyere and the diameter of the furnace opening part are controlled to regulate the gas flowing speed at the furnace top part to <=1.5 m/sec and solid reducing material of the coke, etc., having >=300 μm size is automatically dropped into the furnace to improve and stabilize the concentration of the recovered zinc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method in which powdery or granular materials such as ore, dust, sludge and the like are blown from tuyeres of a solid-reduction-material-packed smelting reduction furnace for filling a solid reduction material such as coke. The present invention relates to a method of operating a furnace in which a gas at the furnace top is cooled outside the furnace to separate and recover highly volatile metals such as zinc.

[0002]

2. Description of the Related Art 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 or the like using this iron scrap as a main raw material, dust containing zinc and iron as main components is generated. This dust is currently
Due to the high cost of collection, after collection, they are detoxified and then landfilled.

[0003] However, the content of zinc contained in the electric furnace dust is 20 to 30%, and the same amount of iron is also contained. These forms may be oxides or hydroxides, but the amount of dust generated is as large as 15 kilograms per ton of steel, low cost and no waste, and each is collected in a completely separated state. There is a need for technology to do this.

As a furnace operating method for implementing such a separation and recovery technique in a vertical furnace filled with a solid reducing agent such as coke, for example, Japanese Patent Application Laid-Open No.
There is one described in JP-A-325646. In this furnace operation method, at least two upper and lower tuyeres are provided in a solid reducing agent packed bed smelting reduction furnace for filling a solid reducing agent, and zinc-containing powdery raw materials such as electric furnace dust are loaded from the upper tuyeres. Iron is melted and dropped in the furnace floor, and zinc is evaporated and raised to the furnace top.The gas at the furnace top is cooled outside the furnace, and highly volatile metals such as zinc are separated and recovered. It is to do.

[0005]

However, in the above-described conventional furnace operating method, fine powder or ash of a solid reducing material such as coke is apt to be mixed into the gas at the furnace top, and if the coke ratio changes due to fluctuations in the operating conditions. Accordingly, the mixing ratio of the recovered highly volatile metal such as zinc and the fine powder or ash of the solid reducing agent changes, and the problem that the concentration of the recovered highly volatile metal changes easily occurs.

The present invention has been developed in order to solve the above-mentioned problems. By providing an environment in which the fine powder and ash of the solid reducing material are easily dropped, the high volatility recovered from the furnace top gas is improved. It is an object of the present invention to provide a method of operating a furnace for stabilizing the concentration of metal.

[0007]

In order to solve the above-mentioned problems, a method for operating a furnace according to claim 1 of the present invention is characterized in that a solid reduction material packed bed type smelting reduction furnace has at least two upper and lower stages. A method for operating a furnace, wherein a tuyere is provided, a powdery and granular material is charged from an upper tuyere, and a gas at a furnace top is cooled outside the furnace to separate and recover a highly volatile metal. The gas flow velocity at the top is set to 1.5 m / sec or less.

According to a second aspect of the present invention, in the furnace operating method, at least one of a flow rate of gas blown from a tuyere and a furnace diameter is controlled to control a gas flow rate at the furnace top. It is characterized by doing.

[0009]

Embodiments of the present invention will be described below. FIG. 1 shows a vertical smelting reduction furnace (hereinafter simply referred to as a vertical furnace) to which the furnace operating method of the present invention is applied. This vertical furnace 1 is filled with a solid reducing material 2 such as coke, and constitutes a solid reducing material packed bed type smelting reduction furnace as a whole. The vertical furnace 1 is provided with at least two upper and lower tuyeres. As the vertical furnace 1 provided with the tuyeres 3 and 4 in the upper and lower stages in this manner, for example, a furnace developed for efficiently melting chromium ore can be applied. That is, when sufficient heat amount for smelting reduction cannot be obtained with only the tuyere 3 in the upper stage, the heat amount is supplemented from the tuyere 4 in the lower stage and the smelting reduction is sufficiently performed during that time. The number of tuyeres 3 and 4 is set based on the required reducing ability and melting ability.

[0010] In these tuyeres 3, 4, hot air and oxygen-enriched hot air or pure oxygen as needed are used as blowing gas from a blower 5 through a hot air generating furnace 6. On the other hand, the upper tuyere 3 is provided with a raw material blowing device 7.
Raw material is blown from. The raw material blown from the tuyere 3 at the upper stage is basically limited to a granular material, and melts, burns, reduces and evaporates immediately after blowing. Among these raw materials, the oxides and hydroxides of the low-volatility metal such as molten iron are reduced in the process of dropping the packed bed of the solid reducing material, and accumulate in the hearth. In addition, vapor of highly volatile metal such as zinc which evaporates,
It rises to the furnace top through the gap between the solid reducing materials 2 and is discharged together with the furnace gas as described later.

Powdery and granular raw materials such as electric furnace dust, which is zinc-containing dust, are in principle blown from the upper tuyere 3. Since the powdery and granular material is light, when it is charged from the furnace top, the low volatile metal is sufficiently melted and dropped into the packed bed of the solid reducing material 2 by the ascending airflow in the furnace, for example, as described above. Since the material is blown off before and is discharged from the furnace top as it is, the granular material is blown from the tuyere 3 in the upper stage in order to prevent the discharge. In other words, the powdery and granular material is
It must melt, burn and evaporate immediately in the raceway in front of the upper tuyere 3 to be blown.

On the other hand, since the massive raw material has a large weight, it does not blow off even if it receives a rising airflow in the furnace. In addition, since this kind of bulk 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. Also, when the bulk material is pulverized into powder and granules, the material is blown from the tuyere 3 in the upper stage. On the contrary,
Since the bulk charge is heavy, it does not blow off even when it receives the rising air current in the furnace. Also, this kind of bulk charge is
As mentioned above, there is no need to melt instantly in front of the tuyere,
As a rule, the furnace top charging device 8 is charged from the furnace top. In addition, as described later, in the present embodiment, it is necessary to maintain the temperature of the furnace top at a high temperature, but 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 principle, so that the temperature at the furnace top does not drop. More specifically, it is preferable to charge continuously by a charging pipe system from the furnace top. Of course, even if a large amount of bulk charge is charged at once,
It suffices if a sufficient amount of heat can be obtained and the furnace top temperature can be maintained high, but such an increase in the unit fuel consumption would be avoided. In addition, when the bulk charge is pulverized into powder and granules, it should be charged from the tuyere 3 in the upper stage.

Further, in the present embodiment, in order to keep the temperature of the furnace top high, the secondary combustion gas is supplied to the space of the furnace top and is intentionally burned in the furnace top. The secondary combustion gas is also supplied to the inside of 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 sent into the exhaust gas cooling / cleaning device 9. This exhaust gas cooling / cleaning device 9
Specifically, a wet cooling device, that is, spraying the liquid in the exhaust gas, lowering the exhaust gas temperature, cooling and solidifying the substance in a vapor state, dripping and settling with the liquid,
It is intended to separate and recover it as a slurry, and to collect gas that does not liquefy or solidify as a gas. In this embodiment, as described later, a highly volatile metal such as zinc is solidified and separated and recovered from the exhaust gas, and the exhaust gas to be discharged is obtained as a high-calorie fuel gas containing a carbon monoxide gas. In addition, by rapidly cooling such high-temperature exhaust gas, re-synthesis of dioxin which is a harmful substance contained in the raw material can be prevented.

Next, in the solid-reduction-material packed-bed smelting reduction furnace described above, iron oxides and hydroxides, which are low-volatile metals, and zinc oxides and hydroxides, which are high-volatile metals, are mainly used. The powdered material such as electric furnace dust containing the material is used as a charging material, which is separated and recovered into iron and zinc, and at the same time, a high calorie fuel gas is collected. Here, the furnace diameter is 1.2 m and the height is 8.0.
m, using a vertical furnace with upper and lower tuyeres. The blowing conditions and the blowing conditions of the raw materials were adjusted as shown in Table 1 below. Here, it is assumed that hot air enriched with oxygen is blown from the tuyere, and the powdery raw material is also blown from the tuyere.

[0015]

[Table 1]

Next, conditions for stabilizing the zinc concentration in the slurry (product) recovered by the exhaust gas cooling / cleaning apparatus will be described. First, the particle size distribution of the recovered product is shown in Fig. 2.
Table 2 shows the results of component analysis at each particle size. As apparent from these, it is considered that zinc in the recovered product has a small particle size, and that having a large particle size is carbon, that is, fine powder or ash of a solid reducing material. In addition, zinc in the recovered product has an extremely small particle size compared to the fine powder and ash of the solid reductant, so the fine powder and ash of the single solid reductant are more zinc It is considered heavier than the particles.
In order to reduce the fine powder and ash of the solid reducing material having a large particle diameter and a large weight from the recovered product as described above, a powder particle removing device such as a cyclone is interposed before the exhaust gas cooling / cleaning device. However, there are restrictions on cost and equipment.

[0017]

[Table 2]

On the other hand, the fine powder and ash of the solid reducing material in the recovered product have a large particle diameter and a large weight. For example, if the gas flow rate at the furnace top is slow, the solid reducing material should automatically fall into the furnace. Therefore, indicating the terminal velocity U _t in each particle size to 1 expression below. U _t = ((2 m · (ρ _p− ρ _g ) · g) / (C · ρ _p · ρ _g A)) ^0.5 (1) where m: particle weight (kg / piece) ρ _g : gas Density (kg / m ³ ) ρ _p : Particle density (kg / m ³ ) g: Gravitational acceleration (m / s ² ) A: Particle cross-sectional area (m ² ) C: Resistance coefficient Was set as follows.

When Re ≦ 5.76, C = 24 / Re 5.76 <Re ≦ 517, C = 10 / Re ^0.5 517 <Re, C = 0.44 where Re: Reynolds number is there.

Each particle size and terminal velocity thus obtained
Is shown in FIG. On the other hand, FIG.
From 2, the threshold value of the particle size of zinc and fine powder and ash of the solid reducing agent
Is assumed to be 300 μm, from FIG.
Flow velocity U at the furnace top _tIs about 1.5 m / sec.
You. That is, the gas flow rate at the furnace top is 1.5 m / sec.
If less than, fine powder of solid reducing agent larger than 300 μm
It is considered that the ash automatically falls into the furnace.

Therefore, as shown in Table 3, the conventional 1200
Nm ³ / h (Comparative Example) a was the blast volume 750 Nm ³ /
h (Example 1), and the total amount of blast oxygen is 160 Nm
^{From 3} / h (Comparative Example) to 250 Nm ³ / h (Example 1), finally, the gas flow rate at the furnace top was 1.85 m / s (Comparative Example) to 1.47 (m / s) (Example 1). ), A vertical furnace with a furnace diameter of 1.2 m, a height of 8.0 m, and three tuyeres in the upper and lower stages is used to separate and collect zinc and iron from electric furnace dust. went. As a result, the ratio of zinc in the obtained recovered product is shown in FIG.

[0022]

[Table 3]

As is clear from FIG. 4, in Example 1 in which the gas flow rate at the furnace top was 1.5 m / sec., The zinc concentration in the recovered product was improved and was more stable. On the other hand, in the comparative example which is the conventional method, it is found that the zinc concentration is low and unstable. Subsequently, in Example 1, the furnace diameter was not changed, but it was noted that the gas flow rate at the furnace top can be controlled by changing the furnace diameter. Table 4 shows the relationship between the furnace diameter and the gas flow rate at the furnace top in Examples 2 and 3. In addition, in Example 2,
In the third embodiment, the air blowing amount is set to 1200 which is the same as that of the comparative example.
And Nm ³ / h, was blown oxygen amount 250Nm ³ / h. In Example 2, the furnace top gas flow rate was 1.15 m / s by setting the furnace diameter to 1.5 m, and in Example 3, the furnace top gas flow rate was 0.82 m by setting the furnace diameter to 1.8 m. / S.

[0024]

[Table 4]

The zinc concentration in the recovered product in Example 2 was improved to 57.4%, and in Example 3, it was improved to 61%. FIG. 5 shows the relationship between the gas flow rate at the furnace top and the zinc concentration in the recovered product in Examples 1 to 3 and Comparative Example. As is clear from the figure, in each embodiment in which the gas flow rate at the furnace top is 1.5 m / sec or less, the gas flow rate at the furnace top is 1.5 m since the zinc concentration is high and stable. / Sec. Or less.

[0026]

As described above, according to the method of operating a furnace according to the first aspect of the present invention, by controlling the gas flow rate at the furnace top to 1.5 m / sec or less, the furnace top can be ,
An environment in which solid reductant such as coke with a relatively large particle size and weight is easily dropped automatically is used, and the mixing ratio with the highly volatile metal recovered from the gas at the top of the furnace is reduced by that much. The recovery concentration can be stabilized.

According to the method of operating a furnace according to claim 2 of the present invention, the gas flow rate at the furnace top is controlled by operating at least one of the flow rate of the gas blown from the tuyere and the diameter of the furnace. Since control is performed, the invention of claim 1 can be easily implemented.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a furnace to which a method for operating a furnace according to the present invention is applied.

FIG. 2 is an explanatory diagram showing a relationship between a particle diameter of a product recovered from a furnace top gas and a ratio thereof.

FIG. 3 is an explanatory diagram of a terminal velocity of each particle diameter.

FIG. 4 is an explanatory diagram of a zinc content ratio of a comparative example according to a conventional method and Example 1 of the present invention.

FIG. 5 is an explanatory diagram showing a relationship between a furnace top gas flow rate and a zinc concentration in a recovered product according to the present invention.

[Explanation of symbols]

 1 is a vertical furnace 2 is a solid reducing agent 3 is an upper tuyere 4 is a lower tuyere 5 is a blower 6 is a hot air generator 7 is a raw material injection device 8 is a furnace top charging device 9 is an exhaust gas cooling / cleaning device

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Takeshi Uchiyama 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Pref. Kawasaki Steel Research Institute (72) Inventor Yoshiaki Hara 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba 4K001 AA10 BA02 BA14 BA15 GA01 GB03 GB09 HA01 4K012 CB02 CB04 CB07

Claims (2)

[Claims] 1. A solid reduction material packed bed type smelting reduction furnace having at least two upper and lower tuyeres, wherein a powdery and granular charge material is blown from the upper tuyeres, and the gas at the furnace top is discharged outside the furnace. A method for operating a furnace for separating and recovering highly volatile metals by cooling at a temperature of 1.5 m / sec or less at the furnace top. 2. The furnace operation according to claim 1, wherein at least one of a flow rate of gas blown from a tuyere and a furnace diameter is operated to control a gas flow rate at the furnace top. Method.