JPH01301812A - Converter which prevents erosion of furnace wall by secondary combustion - Google Patents

Abstract

PURPOSE:To effectively prevent the erosion of furnace wall refractories by secondary combustion by providing tuyeres to be used exclusively for blowing gaseous hydrocarbon to the lower part of a converter throat and specifying the height from the furnace bottom and blowing angle of the tuyeres. CONSTITUTION:The tuyeres 5 to be used exclusively for blowing the gaseous hydrocarbon (gaseous methane, gaseous propane, etc.) or the gas contg. a part of the gaseous hydrocarbon are provided to the lower part of the throat 4 of the composite converter 1 having, for example, a top blowing lance 2 and bottom blowing tuyeres 3 in combination at the time of executing converter operation by secondary combustion method. The height of the tuyeres 5 from the furnace bottom, designated as HL, and the height from the furnace bottom to the throat, designated as HV, are regulated to 0.6HV<=HL<=0.9HV and the blowing angle theta of the tuyeres 5 to horizontal is regulated to -30 deg.<=theta<=30 deg.. The gas blown from the tuyeres 5 is uniformly spread to the sections exposed to the high-temp. gas near the throat, etc., to equally lower the temp. of the sections and to effectively prevent the erosion of refractories. The exhaust gas having high calory is recoverable.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a converter that effectively prevents melting of furnace wall refractories and enables recovery of high-calorie exhaust gas.

<Conventional technology and its challenges> With the development of converter steel manufacturing method, the “steel-through system” has been introduced in the steel industry.
has been established for a long time, and steel production efficiency has improved dramatically, but in recent years, as the global economy has entered a period of stability, demand for steel has steadily stabilized from a temporary unlimited state. I've started to follow it.

For this reason, measures have recently been taken to curb the production of blast furnace pig iron, and at the same time, a large amount of underground scrap has become available and its price has stabilized, so the proportion of scrap in the raw materials for converter steel production has been increased. Studies have begun to establish a converter operation method that also incorporates iron ore and manganese ore.

Among these, measures to increase the scrap ratio when the heat source of hot metal decreases due to hot metal processing and iron ore.

``Technology for applying heat to converters'' as a measure to increase the yield of manganese ore, etc. is attracting attention, and in particular, ``technology to combust CO gas generated during decarburization operations in converters to COz gas in the furnace'' is attracting attention. Securing the required amount of heat through the secondary combustion method is an effective and practical means.''In addition to the normal main oxygen supply nozzle, the top blower is equipped with an 02 supply nozzle for CO gas combustion. "Secondary combustion" methods include a method of operating a converter using a lance, and a method of using a converter in which a 0□ feed nozzle for CO gas combustion is placed diagonally downward in the furnace shoulder (throttle part). Various proposals regarding the law were made.

However, when the above-mentioned "secondary combustion method" is adopted, a) the temperature of the exhaust gas in the furnace rises and the melting loss of the refractory increases (particularly noticeable near the lower part of the furnace mouth).

b) Since the CO content in the exhaust gas decreases, it is disadvantageous in terms of energy recovery.

New problems such as these have arisen, and the need for solutions has been recognized.

Therefore, in order to solve these problems, the present inventors first coated the throttle part of the converter with a carbon-based material, and the carbon in this coating and the carbon present in the high-temperature exhaust gas were
A method for preventing melting of furnace wall refractories by utilizing an endothermic reaction with O (Japanese Patent Application No. 303366/1982)

(B) Carbon in the blown carbon and CO2 in the high-temperature exhaust gas produced by blowing carbon into the constriction section of the converter.
A method for preventing melting and damage of furnace wall refractories by utilizing an endothermic reaction with a furnace wall (Japanese Patent Application No. 61-303366).

(C) A method of blowing carbonaceous powder into the converter through a top blowing lance to prevent melting of the furnace wall refractories.

(D) A method for preventing melting of the furnace wall refractories by blowing carbonaceous powder into the converter through the top blowing lance while rotating the top blowing lance around the axis.

The following proposals were made.

These proposals effectively solved the problems associated with "melting of furnace refractories" and "decrease in exhaust gas calories" when the secondary combustion method was adopted, but the problems continued. According to the studies conducted by the present inventors, the above (A) ~
It has become clear that the method shown in (D) still has the following points to be improved.

That is, the method (A) has the inherent problem that it tends to pick up [C] from the coating when the molten metal is tapped out of the converter, making it unsuitable for melting low carbon steel. In addition, in the method (B) above in which carbonaceous powder is injected from the nozzle of the converter constriction part, it is difficult to uniformly inject the carbonaceous powder, resulting in local supercooling and, on the contrary, thermal spalling of the refractory. The problem is that it tends to cause

On the other hand, although the above methods (C) and (D) can carry out more uniform blowing of carbonaceous material than the above method (B), it is still impossible to blow completely uniformly, and as a result, there are Inconveniences such as overcooling and generation of unreacted carbonaceous material cannot be avoided.

In addition, in the method of injecting carbonaceous powder, it is required to size the carbonaceous material to less than 1 grain in order to increase its reactivity, which necessitates an expansion of the equipment scale, which is a cost advantage. It was also pointed out that there would be a decrease in

Means for Solving the Problems> The present inventors have solved the above-mentioned problems that occur when trying to adopt the secondary combustion method for converter operation, and have solved the problems such as melting of furnace refractories and increased costs. As a result of repeated research to realize stable converter operation without any inconvenience, we found that [it does not matter whether the converter is a top-blowing converter, a bottom-blowing converter, or a combined converter; A tuyere is installed at the bottom of the furnace mouth, and during converter operation, hydrocarbon gas such as methane gas or propane gas, or a portion of hydrocarbon gas such as coke oven gas (hereinafter abbreviated as COG) is extracted from the tuyere. When the containing gases are blown in, these gases come into contact with COz in the high-temperature exhaust gas, and a) In the case of methane gas: CHa+3Co□→4CO+2H,O.

b) For propane gas: C3H1+7CO2→IOCO+4H2O.

For COG: [Hz (inCOG) 10 COz→CO+H20°CH
The endothermic reaction of a(incOG)+3COR-4CO+2H20° occurs, lowering the temperature near the refractory in the furnace, and it does not cause inconveniences such as uneven injection or residual unreacted carbon powder. This led to the finding that the effect of preventing melting and loss of fuel is further improved, and the calorie content of exhaust gas is further increased."

The present invention has been made based on the above findings, and provides a converter with a configuration in which a dedicated tuyere for blowing hydrocarbon gas or gas partially containing hydrocarbon gas is provided at the lower part of the furnace mouth. Furthermore, the height HL of the tuyere from the hearth bottom is
within the range of 0.6HV≦HL≦0.9HV (however, HV is the height from the bottom of the furnace to the mouth of the furnace),
In addition, by setting the blowing angle θ of the tuyere within the range of -30°≦θ≦30° with respect to the horizontal, it is possible to effectively prevent melting of the refractories in the furnace when the secondary combustion method is adopted. It is characterized by the fact that it is able to prevent oxidation and to recover high-calorie exhaust gas.

Here, the basic type of converter is the "top-blown converter."

As mentioned above, it may be either a "bottom blowing converter" or a "compound converter having both top blowing and bottom blowing".

In addition, methane gas or propane gas is suitable as the "hydrocarbon gas" to be blown in from the tuyere for blowing hydrocarbon gas, but of course other gases may also be used. '' is not limited to COG. However, as COG, it is sufficient to use general COG that has been collected in a coke oven in a steelworks and has been purified and removed from dust and other impurities.The typical gas composition of such COG is shown in Table 1. That's right.

Chapter 1 Table Next, the present invention will be explained in more detail based on the drawings.

<Function> FIG. 1 is a schematic diagram of a composite converter 1 having both a top blowing lance 2 and a bottom blowing tuyere 3, which is an example of a converter according to the present invention. A tuyere 5 dedicated to blowing hydrocarbon gas is provided at the bottom, and when applying the secondary combustion method, hydrocarbon gas or gas partially containing hydrocarbon gas is blown from this tuyere 5. , the gas spreads uniformly to areas exposed to high-temperature gas, such as near the furnace mouth, and absorbs C in the high-temperature exhaust gas.
Since it contacts with O2 and causes an endothermic reaction to produce CO, the temperature of the area is lowered evenly, so that refractory erosion is effectively prevented. Moreover, since high-calorie exhaust gas containing a large amount of CO is generated, exhaust gas energy recovery is also extremely advantageous.

In addition, in FIG. 1, the reference numeral 6 indicates slag, and 7 indicates hot metal or molten steel.

By the way, when installing tuyere for blowing hydrocarbon gas at the lower part of the furnace mouth, the height HL from the furnace bottom shown in Fig. 1 is set to 0 in relation to the height HV from the furnace bottom to the furnace mouth. .6HV≦H4≦0.9HV, and the horizontal angle θ of the tuyere is -30”≦
It is preferable to set the value in the range of θ≦30″. This is because if the installed state of the tuyere is rHt<0.6HVJ or θ<−30′J, the heat supply to the molten iron and slag is reduced due to the decrease in exhaust gas temperature. decreases, while rHL > 0.9HVJ or “θ〉3
0°, hydrocarbon gas and exhaust gas (high-temperature Co
This is because the reaction with t) becomes insufficient and the effect of lowering the exhaust gas temperature decreases.

Hereinafter, the effects of the present invention will be specifically explained using examples.

<Example> HL at the bottom of the furnace mouth of a 15-ton combined converter as shown in Figure 1
Three tuyeres for blowing hydrocarbon gas with θ=06 (horizontal) were installed at equal intervals at a position of =0.8HV, and the amount of hot metal was lQt.

Hot metal temperature: 1280℃.

Decarburization treatment of dephosphorized hot metal was carried out under the following conditions: top-blown oxygen lance: 12φ x 6 holes x 15'1 blowing time: 15 minutes.

On the other hand, for comparison, decarburization of dephosphorized hot metal was carried out using the same complex converter as above under the same conditions except for the presence or absence of hydrocarbon gas and carbon material injection.

At this time, the maximum temperature reached on the refractory surface at the bottom of the furnace mouth,
The amount of erosion of the refractories and the measured values of the exhaust gas components at the furnace mouth are
Shown in the table.

The surface temperature of the refractory in the furnace was measured by setting a thermocouple at a depth of 3R from the surface of the refractory.

As is clear from the results shown in Table 2, when using the converter according to the present invention equipped with tuyeres for blowing propane gas or COO, the efficiency of the reaction between hydrocarbon gas and CO2 gas increases. This improvement not only significantly reduces the amount of corrosion of refractories compared to when using a conventional converter, but also increases the amount of OCO in the exhaust gas, further reducing converter operating costs. I understand.

(Blank below) Summary of Effects> As described above, according to the present invention, existing converters can be used as is, the melting of the furnace wall refractories is minimized, and high-calorie exhaust gas can be recovered. This makes it possible to realize a converter, further improve the operating efficiency of the converter, and further reduce the operating cost of the converter, which is extremely useful in industry.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a converter according to the present invention. In the drawings, ■...Combined converter, 2...Top-blowing oxygen lance. 3...bottom blowing tuyere, 4...furnace mouth. 5...Tuyere for blowing hydrocarbon gas. 6...Slag, 7...Hot metal or molten steel.

Claims (1)

[Scope of Claims] (1) A converter characterized in that a dedicated tuyere for blowing a hydrocarbon gas or a gas partially containing a hydrocarbon gas is provided at the lower part of the furnace mouth. (2) The height H_L of the tuyere from the hearth bottom is within the range of 0.6H_V≦H_L≦0.9H_V (however, H_V is the height from the hearth bottom to the hearth mouth), and the blowing of the tuyere The converter according to claim 1, wherein the angle θ is set within the range of -30°≦θ≦30° with respect to the horizontal.