JP2541200B2 - Converter for preventing melting of furnace wall due to high temperature gas - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a converter capable of recovering exhaust gas having high calories in order to prevent melting damage of a refractory on a furnace wall due to high temperature gas.

<Background technology> With the development of the converter steelmaking method, the steel industry has a “steel integrated system”
The steel production efficiency has improved dramatically for a long time since its establishment, but with the recent global economic downturn, demand for steel has shown a steady stabilization trend from a temporary unrestricted state. I started to trace.

Because of this, recently, there has been a tendency to take measures to control the production amount of blast furnace pig iron, and at the same time, a large amount of commercial scrap has been circulating and its price has stabilized, so that scrap as a raw material for steelmaking in converter furnaces The establishment of a converter operation method in which the use ratio is increased and iron ore or manganese ore is also compounded has begun to be considered.

Of these, "heat application technology for converters" is attracting attention as a measure for increasing the scrap ratio when the heat source of the hot metal decreases due to hot metal treatment, and for increasing the distribution of iron ore, manganese ore, etc. It is most effective and practical to secure the required amount of heat by the "secondary combustion method" in which the CO gas generated during the decarburization operation in the furnace is burned to CO ₂ gas in the furnace. " Besides CO gas combustion
A method of the O ₂ delivery nozzle with a spray lance on which is disposed performing converter operation, rolling disposed toward the O ₂ delivery nozzle for CO gas combustion obliquely downward Rokata portion (narrowed portion) Various proposals have been made regarding the "secondary combustion method" such as a method using a furnace.

However, when the "secondary combustion method" as described above is adopted, (a) the temperature of the exhaust gas in the furnace rises and the melting loss of the refractory increases, and (b) the CO content in the exhaust gas decreases. Therefore, it is difficult to say that the above-mentioned "secondary combustion method" has been put to practical use in converter steelmaking, where new problems such as energy recovery are disadvantageous, and the reduction of operating costs is strictly demanded. there were.

Moreover, even if such a "secondary combustion method" is not actively promoted, the exhaust gas temperature in the converter during operation is around 1800 ° C, so there is a constant concern of refractory melting loss. Sufficient measures were eagerly awaited.

<Means for Solving Problems> From the viewpoints described above, the present inventors have found that the melting loss of the refractory in the furnace is almost eliminated not only during the normal operation but also during the operation in which the secondary combustion ratio is increased. As a result of intensive studies to provide a converter that rarely occurs and the energy recovery rate is sufficiently satisfied, the following findings were obtained. That is, A) the same applies to any type of converter, but when a carbonaceous material is coated on the inner surface of the refractory material at the portion where the high temperature exhaust gas in the furnace is in direct contact, CO ₂ in the high temperature exhaust gas becomes C in the material coating causes an endothermic reaction of C + CO ₂ → 2CO to lower the temperature in the vicinity of the refractory, B) The temperature decrease in the vicinity of the refractory due to this endothermic reaction is sufficient to prevent melting of the refractory. Yes, the melting loss of the refractory in the furnace is remarkably suppressed even if the converter operation is performed with the secondary combustion ratio increased. C) Moreover, the CO gas in the exhaust gas increases due to the endothermic reaction. Therefore, the calorie of the exhaust gas increases, which is extremely advantageous from the viewpoint of energy recovery. D) Furthermore, in addition to coating the carbonaceous material on the inner surface of the refractory, a tuyere is provided at the lower part of the furnace mouth of the converter. , Converter operation In the blowing carbonaceous material powder from該羽port, since the lower the temperature of the furnace refractories vicinity undergoes an endothermic reaction shown C of the carbonaceous material powder also CO ₂ in the high-temperature exhaust gas by the formula , The refractory material melting prevention effect is further improved, and the calorie of exhaust gas is further increased.

The present invention has been made based on the above findings. "As shown in Fig. 1, a portion of the inner surface of the furnace wall 1 exposed to high-temperature gas is coated with a carbonaceous substance 2 to form a converter (converter). The basic form of the furnace is not specified), or, as shown in FIG. 2, the part of the inner surface of the furnace wall 1 exposed to the high temperature gas is coated 2 with a carbonaceous material. By constructing the converter by providing the tuyere 4 for blowing carbonaceous material powder in the lower part of the furnace mouth 3, it is possible to effectively prevent melting damage of the refractory in the furnace due to high temperature gas, and The feature is that "the collection is possible".

Here, in FIGS. 1 and 2, reference numeral 5 indicates a top blowing oxygen lance, 6 a bottom blowing tuyer, 7 a slag, and 8 hot metal or molten steel, respectively.

It should be noted that the above-mentioned "site exposed to high-temperature gas on the inner surface of the furnace wall" is not particularly specified, but usually the vicinity of the lower part of the furnace opening as shown in FIG. 1 or 2 corresponds to this. To do. Further, as the carbonaceous substance forming the coating layer, there can be mentioned, for example, coals and coal powder, and the coating is a refractory material which constitutes the furnace wall by spraying after mixing the carbonaceous substance powder with a binder and water. Means such as coating on the inner surface of the required site may be adopted. Then, as the carbonaceous substance blown from the tuyere for blowing the carbonaceous substance, powder having an average particle diameter of about 0.125 mm such as coke powder or coal powder is suitable.

By the way, when the tuyere for blowing carbonaceous material is provided in the lower part of the furnace mouth, the height [H _L ] from the furnace bottom shown in Fig. 2 is 0.6H _V ≤H _L ≤0.9H _V (however, H _V is the range from the bottom to the height of the furnace), and the horizontal angle [θ] of the tuyere is preferably set within the range of −15 ° ≦ θ ≦ 15 °. This is because the height of the tuyeres blowing carbonaceous material [H _L] is the height from the furnace bottom to the furnace opening [H _V]
Is less than 0.6 times, or the tuyere horizontal angle [θ] is -15
If the temperature falls below °, the heat supply to the molten iron / slag tends to be insufficient due to the decrease in exhaust gas temperature, while the height H _L is 0.9H.
_{This is because if V} is exceeded or [θ] exceeds 15 °, the effect of lowering the temperature of exhaust gas in the furnace becomes insufficient, and improvement in the refractory melt damage prevention effect commensurate with installation of tuyere cannot be expected.

 Next, the present invention will be specifically described with reference to examples.

To <Example> Example 1 refractory surfaces of the furnace wall inner surface of the first on 10 tons, as shown in FIG Bottom both blown composite blowing converter, extending from throat to a depth of 1/2 H _V With a thickness of 5 mm, C: 85%, SiO ₂ : 5.2% and Al ₂ O ₃ : 3.1%
Applying carbonaceous powder containing this, and using this converter, the amount of hot metal: 8000kg, hot metal temperature: 1280 ~ 1295 ℃, use blow oxygen lance: 12φ x 6 holes x 15 °, blowing time: 15 minutes The dephosphorized hot metal was decarburized under the conditions.

On the other hand, for comparison, the same conventional top / bottom double-blown combined blowing converter was used, except that the carbonaceous material powder was not applied to the inner surface, and the decarburization treatment of the dephosphorized hot metal was performed under the same conditions. Also carried out.

Table 1 shows the maximum temperature reached by the refractory surface at the lower part of the furnace opening, the melting loss of the refractory material, and the measured values of the exhaust gas components in the furnace. The surface temperature of the refractory was measured by setting a thermocouple at a depth of 3 mm from the surface of the refractory.

From the results shown in Table 1, when the converter according to the present invention in which the inner surface of the furnace wall is coated with the carbonaceous material is used, the melting loss of the refractory material is significantly reduced as compared with the case where the conventional converter is used. It is clear that you can.

The refractory surface of the oven wall inner surface in Example 2 first on 10 tons, as shown in FIG Bottom both blown composite blowing converter, the thickness of 3mm over the throat depth of 1/2 H _V 85%, SiO _2:: C with is 5.2% and the Al ₂ O _3: 3.1%
The carbonaceous powder containing carbon is applied and the tuyere for blowing carbonaceous material powder is installed on the upper part of the furnace ( _HL = 0.8H _V , θ = 10
゜), using this converter while blowing coke powder (-60 mesh, C content: 88%) from the tuyere for carbonaceous material powder blowing (blowing amount: 60 kg), hot metal amount: 8000 kg, hot metal temperature: The dephosphorized hot metal was decarburized under the conditions of 1290 to 1310 ° C., blowing oxygen lance after use: 14φ × 3 holes × 10 ° and 9φ × 6 holes × 20 °, and blowing time: 15 minutes.

On the other hand, for comparison, the conventional top / bottom double-blown composite blowing converter similar to the above except that the carbonaceous material powder was not applied to the inner surface and the tuyere for blowing the carbonaceous material powder was not installed. The dephosphorized hot metal was also decarburized under the same conditions.

Table 2 shows the maximum reached temperature of the refractory surface at the lower part of the furnace opening, the melting loss of the refractory material, and the measured values of the exhaust gas components in the furnace. In addition, the surface temperature of the refractory material is the same as in Example 1.
In the same manner as above, a thermocouple was set at a depth of 3 mm from the surface of the refractory material for measurement.

Also from the results shown in Table 2, when the carbonaceous material was coated on the inner surface of the furnace wall and the converter according to the present invention in which the tuyere for blowing carbonaceous material powder was installed was used, the conventional converter was used. It is apparent that not only the melting loss of refractory materials can be significantly reduced, but also the amount of CO in exhaust gas can be increased at the same time, and an effect in terms of energy recovery can be expected sufficiently.

The refractory surface of the oven wall inner surface of the Example 3 on 10 tons, as shown in FIG. 1, the bottom two-blown composite blowing converter, the thickness of 7mm over the throat depth of 1/2 H _V 85%, SiO _2:: C with is 5.2% and the Al ₂ O _3: 3.1%
Was applied.

Then, using this converter, 5000 kg of dephosphorized pig iron as seed water
The chromium ore (total Cr content: 31%, total Fe content: 20.6%) was melt-reduced. The operating conditions of the converter at this time are as follows: Hot metal hot metal amount: 5000kg, Hot metal hot metal temperature: 1250 ℃, Final hot metal temperature: 1600 ℃, Blowing oxygen lance: 12φ × 6 holes × 15 °, Blowing time: 130 minutes Met.

On the other hand, for comparison, the same conventional top / bottom double-blown combined blowing converter was used, except that the carbonaceous material powder was not applied to the inner surface, and the reduction treatment of chromium ore was carried out under the same conditions. .

Table 3 shows the maximum reached temperature of the refractory surface at the lower part of the furnace mouth, the melting loss of the refractory material, and the measured values of the exhaust gas components in the furnace. The surface temperature of the refractory was measured by setting a thermocouple at a depth of 5 mm from the surface of the refractory.

As is clear from the results shown in Table 3, in this case as well, when the converter according to the present invention in which the inner surface of the furnace wall is coated with the carbonaceous material is used, the fire resistance is higher than that in the case where the conventional converter is used. It can be seen that the melting loss of the material can be significantly reduced.

<Summary of Effects> As described above, according to the present invention, the existing converter is used as it is to provide a converter capable of recovering exhaust gas having a high calorie with minimal melting loss of the refractory of the furnace wall refractory. Therefore, it is possible to further improve the converter operating efficiency, and further reduce the converter operating cost, which brings about an extremely useful effect in the industry.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of “a converter having a carbonaceous material coating on the inner surface of the furnace wall” according to the present invention, and FIG. 2 is a “schematic coating of carbonaceous material on the inner surface of the furnace wall” according to the present invention. FIG. 1 is a schematic diagram showing an example of a “converter having a tuyere for blowing carbonaceous material powder”. In the drawing, 1 ... furnace wall, 2 ... carbonaceous material coating layer, 3 ... furnace mouth, 4 ... tuyere for blowing carbonaceous material powder, 5 ... top blowing oxygen lance, 6 ... bottom blowing Mouth, 7 ... slag, 8 ... hot metal or molten steel.

Claims (2)

(57) [Claims] 1. A converter for preventing melting of a furnace wall due to a high temperature gas, characterized by coating a portion of the inner surface of the furnace wall exposed to the high temperature gas with a carbonaceous material. 2. A high temperature gas, characterized in that a portion exposed to the high temperature gas on the inner surface of the furnace wall is coated with a carbonaceous material, and a tuyere for blowing carbonaceous material powder is provided at the lower part of the furnace mouth. Converter that prevents melting damage to the furnace wall.