JP2000199007A - Operation of furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise the molten iron tapping temp., to secure the fluidity of slag and to improve the reducibility and the fusibility by raising the temp. of coke. SOLUTION: A gas blowing hole 13 is arranged at a portion, in which the slag 11 is stayed and the filling layer of coke 2 continues to the furnace hearth, i.e., at the position which does not vertically overlap with at least a tuyere 4 at the lower part, in the furnace hearth part in a coke filling layer type vertical furnace 1 having two steps of the tuyeres 4 at the upper part and the lower part and for filling the coke 2, and the coke 2 in the slag 11 is burnt to generate the heat by blowing assistant gas, such as oxygen, hot blast from the gas blowing hole, and the pig iron 10 and the coke 2 are heated with the conduction of the heat by heating the slag 11. The filling layer of the coke 2 in the lower part of the tuyere 4 at lower step is cut into pieces with a raceway 12, and the coke 2 is floated up on the slag 11 and therefore, the effect is small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a solid reducing agent packed bed type smelting reduction furnace for filling a solid reducing agent such as coke with at least two upper and lower tuyeres.
It relates to a method of operating a furnace that injects powdered granular material such as electric furnace dust and melts and drops highly volatile metals such as zinc from the gas at the top of the furnace and iron on the hearth. Things.

[0002]

2. Description of the Related Art Such a furnace operation method is described in, for example, Japanese Patent Publication No. Hei 4-1043 and Japanese Patent Publication No. Hei 4-27406 proposed by the present applicant.
Of the former, the former adjusts the oxygen concentration in the blown gas for conveying the particulate ore such as particulate ore to the upper tuyere according to the amount of the particulate orifice to be blown,
It stabilizes the size and temperature of the raceway in front of the tuyere, thereby improving and stabilizing productivity.
In the latter case, the oxygen concentration in the gas blown into the tuyere of each of the upper and lower stages is independently adjusted according to the smelting reduction characteristics of the metal oxide and the amount of molten metal generated. It is possible to balance the air flow between the mouths, achieve the raceway temperature according to the characteristics of the raw materials, and reduce the fuel consumption per equivalent production amount.

[0003]

By the way, when the furnace to be operated is small and the amount of melt generated is small, or the raw material whose amount of melt generated is relatively small compared to the amount of gas generated is smelted. In such a case, the amount of decrease in the melt temperature in the hearth becomes large, which may cause a drop in tapping temperature, defective tapping slag, and cooling of the hearth.

[0004] In order to cope with such a problem, the above-mentioned conventional furnace operation method adjusts the oxygen concentration of the blown gas simply from the viewpoint of the melting property at the upper tuyere or the reducibility between the upper and lower tuyeres. It is not a solution to the problem. The present invention has been developed in order to solve the above-mentioned problems. The slag temperature in the hearth is quickly increased to secure the tapping temperature, the fluidity of the slag is increased, and the solid reducing agent is charged. It is an object of the present invention to provide a furnace operating method capable of increasing the temperature of a bed to improve and reduce and improve the melting property and stabilization.

[0005]

In order to solve the above problems, a method of operating a furnace according to claim 1 of the present invention comprises providing at least two upper and lower tuyeres and filling with a solid reducing material. A method for operating a solid reduction material packed bed type smelting reduction furnace, wherein a gas injection port is provided in a hearth where a packed bed of solid reduction material is present and in a portion where slag is stagnated, from which a flammability is improved. It is characterized by injecting gas.

According to a second aspect of the present invention, in the method of operating a furnace according to the first aspect, the gas inlet is provided so as not to vertically overlap at least a lower tuyere. It is a feature.

[0007]

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 may be set, for example, from the reducing capacity and the melting capacity to achieve the required smelting capacity, which is determined according to the depth of the raceway in front of each tuyere or the cross-sectional area. Is done.

[0008] Hot air or a gas enriched with oxygen, or pure oxygen as required, is used as blow gas from the blower 5 through the hot air generating furnace 6 to these tuyeres 3 and 4. This is because oxygen is required to burn the solid reducing material 2 in the furnace and use the combustion heat for melting, burning, evaporating, reducing, etc. the raw material, and also heats the blown gas. In this case, the sensible heat of the blown gas can be used as a form of heat input into the furnace. Also, among these, as the proportion of oxygen in the hot air supplied to the lower tuyere 4 increases, the amount of heat up to the upper tuyere 3 increases as described above, and when it becomes pure oxygen, The furnace temperature can be significantly increased. In the present embodiment, the tuyere front temperature and the furnace top temperature must be set high as described later, and in view of these, the ratio of oxygen in the supplied hot air may be adjusted.

On the other hand, a raw material is blown into the upper tuyere 3 from a raw material blowing device 7. 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. Of this raw material,
Oxides and hydroxides of low-volatile metals such as molten iron are reduced in the process of dropping the packed bed of the solid reducing material, 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 material 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, is 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. 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 if a large amount of bulk material is charged at once, the temperature of the furnace top may be too low. Therefore, the bulk material is charged continuously in principle, so that the temperature at the furnace top does not decrease. 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 raw material is charged at a time, it is sufficient that a sufficient amount of heat is obtained and the furnace top temperature can be maintained high. Also, when the bulk material is pulverized into powder and granules, it should be blown from the tuyere 3 in the upper stage.

In this 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 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. However, when the secondary combustion gas is burned, carbon dioxide is generated. In the present embodiment, the furnace top is included, and exhaust gas cooling and cooling is performed from the furnace top.
It is necessary to reduce the oxygen potential in the duct leading to the cleaning device in accordance with the temperature. For this purpose, it is necessary to measure the gas temperature and the composition and strictly control the supply amount of the secondary combustion gas.

The exhaust gas discharged from the furnace top in this way is sent into the exhaust gas cooling / cleaning device 9. 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, to cool and solidify a substance in a vapor state, and to drip 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,
As described later, 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 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 following describes conditions for using a powdery material such as electric furnace dust as a zinc-containing dust as a charging material, separating and recovering it into iron and zinc, and simultaneously extracting a high-calorie fuel gas.

In recent years, the amount of generation of iron scrap containing zinc, such as surface-treated steel sheets for automobiles, has increased. 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. At present, because of high collection costs, this dust is detoxified after dust collection, and then dumped to landfill. 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.

Here, an example of the composition of the raw material is shown in Table 1.
As is clear from the table, it contains a considerable proportion of iron and zinc, and also contains calcium oxide, silica, alumina and the like.

[0017]

[Table 1]

Next, the operating conditions are shown in Table 2. here,
The oxygen-enriched hot air shall be blown from the tuyere, and the powdery and charged raw materials shall also be blown from the tuyere.

[0019]

[Table 2]

As described above, the powdery granular material is blown from the tuyeres (the upper tuyeres when there are at least two tuyeres). If the temperature in front of the tuyere is low, the iron component to be separated and collected by melting and dropping is not sufficiently melted,
It is blown off by the rising air current in the furnace, discharged from the furnace top, and taken out by the exhaust gas cooling / cleaning device. In other words, iron will be mixed into the slurry in the exhaust gas cooling / cleaning apparatus where only zinc is to be separated and recovered. It has been found that the temperature before the tuyere, especially the temperature before the tuyere for blowing the powdery and granular raw materials, greatly contributes to this. FIG. 2 shows the relationship between the temperature in front of the injection tuyere and the concentration of iron contained in the slurry in the exhaust gas cooling / cleaning device (in the figure, the concentration of iron in the solid content).

As is apparent from the figure, the concentration of iron contained in the slurry is such that the temperature before the injection tuyere is 1500 ° C.
In the above region, the size becomes smaller. In other words, the tuyere temperature is 15
If the temperature is set to 00 ° C. or higher, the iron content in the powdery granular material is immediately melted and dropped in front of the tuyere, and therefore, it is considered that a small percentage of the iron is blown off by the rising airflow in the furnace.
Further, by setting the temperature before the blowing tuyere to 1700 ° C. or higher, the melting can be further promoted. Once melted in this way, the molten iron drops into the solid reducing material layer, is reduced during that time, and accumulates in the hearth. Therefore, if it is taken out, high-purity iron can be separated and recovered.

On the other hand, when gaseous zinc reacts with carbon dioxide, solid zinc oxide and carbon monoxide are produced. This reaction is a reversible reaction. As the temperature is lower or the oxygen potential is higher, solid zinc oxide is easily generated. When the temperature in the furnace and from the furnace top to the exhaust gas duct is low, or the oxygen potential is large, solid zinc oxide cannot reach the exhaust gas cooling / manufacturing device and adheres to the furnace wall or duct wall. If the amount becomes extremely large, the duct or the furnace may be closed, and the operation may not be continued.

The factors governing the reaction are temperature and oxygen potential. The oxygen potential is an index indicating the degree of oxidizing property of the atmosphere. Since the atmosphere at the top of the furnace is almost exclusively carbon dioxide and carbon monoxide, specifically, CO + 1
/ 2O ₂ = free energy change of reaction of CO ₂ ΔG ° = -67150 + 20.37 (T + 273) (ca
l) is defined by the following equation obtained from When the relationship between the oxygen potential and the temperature of the furnace top is examined by substituting the reaction heat necessary for the reaction, a single curve (substantially a straight line) shown in FIG. 3 is obtained. In the region where the oxygen potential is lower or the temperature is higher than this, gaseous zinc is stable. That is, the zinc state of the gas can be maintained in the lower left region of the curve in the figure. This area is given by the following two equations.

Log (Po ₂ ) = 2 log (Pco ₂ / Pco) − 29386 / (T + 273) +8.914 (1) log (Po ₂ ) −48138 / (T + 273) +25.35 (25) 2) However, T: Atmosphere temperature in the furnace or furnace top (° C) Po ₂ : Oxygen potential (atm) In addition to these conditions, the temperature of the furnace top is set to 730 ° C or more as a temperature condition in which zinc is further stabilized as a gas. did. Further, it is desirable that the gas temperature T (° C.) and the oxygen potential Po ₂ (atm) at the furnace top before the secondary combustion are in the region surrounded by the following three equations. The reason for this is that the adhesion of zinc oxide is reduced even in the part near the charging surface at the furnace top, the adhesion of zinc oxide in the furnace is eliminated, and there is no need to perform secondary combustion. This is because, even in the case of performing combustion, excessively high-temperature combustion gas is not generated, and it is not necessary to excessively reduce the oxygen potential.

T ≧ 730 ° C. log (Po ₂ ) ≦ −29386 / (T + 273) +6.51 (3) When operating while satisfying these conditions, zinc oxide adheres from the furnace top to the exhaust gas duct. In addition, it is possible to separate and recover zinc and iron as described above, and at the same time, it is possible to collect high-calorie fuel gas. On the other hand, if the conditions were not satisfied, the zinc oxide adhering to the furnace wall clogged the furnace in about one to two weeks, and the operation could not be continued. In order to control these conditions, the amount of air blown from the tuyere, the amount of oxygen enriched, the coke ratio changed by adjusting the feed rate of the raw material, the execution of secondary combustion at the furnace top and duct, and the secondary combustion The main means was gas conditioning.

Next, specific examples of improving the tapping temperature, securing the slag fluidity, and improving the reducibility and melting property by raising the temperature of the solid reducing material performed in the present embodiment will be described. FIG. 4 shows the hearth of the vertical furnace 1 described with reference to FIG. As described above, the solid reductant 2 charged from the furnace top is approximately continuous to the hearth as a packed bed. Pig iron 10 having a large specific gravity melted and dropped in the meantime accumulates in the hearth, and a slag 11 having a smaller specific gravity floats above it. The vertical furnace 1 has a so-called overflow type tapping structure, and the height of the pig iron 10 is determined by the height of the weir. Therefore, the location of the slag 11 is also accurately determined.

On the other hand, the same applies to the tuyere 3 in the upper stage, but a raceway 12 is also formed in front of the tuyere of the tuyere 4 in the lower stage. It is generally considered that the raceway 12 is hollow or the solid reductant 2 is in a rough state, and the blowing gas blown from each tuyere 3, 4 inside or around the raceway 12 is considered. As a result, the solid reducing material 2 burns and generates heat. Therefore, above and below this raceway 12,
The packed bed of the solid reducing material 2 is not continuous. Therefore, the solid reductant 2 below this does not receive the weight of the solid reductant above it, and the solid reductant 2 floats above the pig iron 10 or the slag 11 having a large specific gravity. Has become.

In the present embodiment, the slag 11 exists at a position not vertically overlapping the tuyere 4 at the lower stage, that is, at a position where the packed layer of the solid reducing material 2 is continuously present up to the hearth. Individual gas inlets 13
From which a combustible gas to be supplied to each of the tuyeres 3, 4 is blown, ie, hot air, oxygen-enriched gas or pure oxygen. As a result, the solid reductant 2 in the slag 11 immediately burns and generates heat, and the heat heats the slag 11, and heat transfer from the slag 11 causes the pig iron 1 to generate heat.
0 is also heated. Therefore, the tapping temperature can be improved, and the fluidity of the slag can be ensured. In particular, the viscosity of slag is highly temperature-dependent, and a slight decrease in temperature may cause a sharp increase in viscosity. In such a case, the fluidity of pig iron passing through the slag decreases. Therefore, increasing the fluidity of slag is important for securing smelting capacity. Further, since the solid reductant 2 above the slag 11 is also heated, the reducibility and the melting property are also improved.

Next, the gas injection port was provided in the hearth of a vertical furnace having a daily pig iron production of 30 t / d and a furnace volume of 27 m ³ , from which a combustion supporting gas was blown. An example will be described. The production of pig iron in this furnace is 820 kg /
h, the amount of slag produced is 330 kg / h. here,
180 ° phase from the lower tuyere centering on the center of the furnace
At a height of 300 mm from the hearth and provided a gas-supplying port to inject a combustible gas having various oxygen contents. FIG. 5 shows the relationship between the amount of oxygen from the gas inlet (the amount of oxygen in the auxiliary tuyere in the figure) and the temperature rise of the pig iron (the temperature rise in the figure). As is clear from the figure, the higher the oxygen concentration of the gas injected into the slag portion, the more the solid reducing agent burns, and as a result, the amount of rise in temperature of the pig iron increases.

Next, the same furnace was used, and the height from the hearth was 3
00 mm, the same as above, but the phase from the lower tuyere centered on the center of the furnace was changed variously, and the oxygen was 10 Nm ³ / h
The temperature rise of pig iron when boiled was investigated. FIG. 6 shows the result. In the figure, the auxiliary tuyere installation angle corresponds to the phase from the lower tuyere centering on the center of the furnace.
That is, 0 ° means that the gas inlet is provided directly below the lower tuyere. As is clear from the figure, when the gas inlet and the lower tuyere overlap vertically, the temperature rise of the pig iron is small, and if the phase is shifted by more than about 5 ° around the center of the furnace, The temperature rise becomes stable. This is because, below the tuyere of the lower stage, the packed layer of the solid reducing material is divided by the raceway, and the solid reducing material is floating on the slag. This is because the slag is not sufficiently burned or, conversely, the slag is locally cooled by the blown gas, so that not only the temperature of the pig iron rises but also the various effects described above cannot be obtained. for that reason,
The gas injection port must be arranged so as not to overlap at least with the tuyere of the lower stage, and it is preferable to shift the phase by 5 ° or more around the center of the furnace.

Further, it is not preferable to provide the gas injection port in a portion where pig iron is provided, since the gas injection port is formed by a lance or the like and melts.

[0032]

As described above, according to the method of operating the furnace according to the first aspect of the present invention, the furnace floor where the packed bed of the solid reducing material exists and the portion where the slag is retained are provided. Since the gas blowing port is provided and the supporting gas is blown from it, the solid reducing material in the part where the supporting gas is blown immediately burns and generates heat, thereby heating the slag. In addition, the tapping temperature can be increased by heat transfer, the fluidity of the slag can be ensured, and the temperature of the solid reducing material packed bed can be increased to improve and reduce the melting property and stabilize.

According to the method of operating a furnace according to claim 2 of the present invention, the gas injection port is provided so as not to vertically overlap at least the lower tuyere. Is stably present inside the slag by the weight from above without being cut by the raceway in front of the lower tuyere, and the effect of the invention of claim 1 is easily obtained.

[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 tuyere front temperature and a concentration of iron collected and contained in exhaust gas from a furnace top.

FIG. 3 is an explanatory diagram of a region controlled by a furnace top temperature and an oxygen potential.

FIG. 4 is a detailed explanatory view of a hearth section.

FIG. 5 is an explanatory diagram showing a relationship between an oxygen amount of gas blown into slag and a temperature rise amount of pig iron.

FIG. 6 is an explanatory diagram showing the relationship between the position of gas blown into slag and the amount of temperature rise of pig iron.

[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 10 is pig iron 11 is slag 12 is raceway 13 is gas inlet

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Natsuki Ishiwata 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Co., Ltd. (72) Takashi Matsui 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki 4K012 CB06 F-term (Reference) in Technical Research Laboratory, Steel Works, Ltd.

Claims (2)

[Claims] 1. A method for operating a solid reducing agent packed bed type smelting reduction furnace provided with at least two upper and lower tuyeres and filled with a solid reducing agent, wherein the hearth has a solid reducing agent packed bed. A method for operating a furnace, characterized in that a gas inlet is provided in a part where slag is retained, and a combustion supporting gas is injected from the gas inlet. 2. The furnace operating method according to claim 1, wherein the gas inlet is provided so as not to vertically overlap at least a lower tuyere.