JPS61238907A - Method for adding metallic oxide to refining furnace - Google Patents

Abstract

PURPOSE:To contrive the effective utilization of waste gas, the increase in the efficiency of refining reaction, the improvement of the consumption of heat quantity, etc., by passing a metallic oxide through a fluidized layer formed by a waste reducing gas formed in the stage of refining to reduce and preheat the same then charging the metallic oxide into a refining furnace. CONSTITUTION:The metallic oxide for refining to be added in the midway of refining in a converter 1 is ground to fine grains and is introduced into a duct 2 provided above the furnace mouth. On the other hand, the waste gas flow rate in the duct 2 is controlled by regulating the blow rate of the top and bottom blowing gas to the converter to form the fluidized layer of the above-mentioned metallic oxide in the duct 2 so that said layer stagnates therein. The metallic oxide is heated and reduced in such fluidized layer by the waste gas of the high temp. contg. CO at a high ratio. The blowing of the above-mentioned blowing gas is thereafter temporarily stopped and the reduced and preheated metal in the fluidized layer is dropped and charged into the furnace. The blowing is then restarted. The refining reaction is thus speeded up and the consumption of the heat quantity is improved without inducing the temp. drop of the molten steel in the furnace by the loading of the metallic oxide. The effective utilization of the waste gas is attained as well.

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention proposes a method for adding metal oxides such as ore as a refining material to a metal refining vessel, especially a converter. This is a technology in which ore, etc. to be processed is passed through a fluidized bed using reducing exhaust gas generated during refining from a converter, and then introduced into the furnace, and is a method of adding refining materials that belongs to the smelting reduction technology.

(Prior art) When refining steel in a metal refining vessel, for example, a converter, ferroalloys are used, including Fe-Mn, Fe-Cr, Fe-Ni.
Since ferroalloys such as ferroalloys such as ferroalloys are expensive, recently, techniques have been proposed that utilize various ores (i.e., metal oxides) of Mn, Ni, Cr, etc. in order to reduce costs.

Such a known technique, as proposed in JP-A-54-158320 or JP-A-55-91913, involves adding a reducing agent such as coal or coke and a heat source together with the metal oxide during refining. It is a method that was realized as a technology for melting and reducing using carbon in hot metal.

(Problems to be Solved by the Invention) In the case of the method of adding ore into the converter according to the above-mentioned known technology, a significant temperature drop generally occurs, and therefore, in addition to the reducing agent, carbonaceous material, Si, etc., are used as a heat source. must be added, which is not economical.

In addition, in the case of known technology, taking a converter as an example, the main component is the refining reaction, and therefore the main component of the refining exhaust gas is CO, which is recovered unburned and used as a heat source for heating furnaces, etc. However, during collection, water was sprayed in the middle of the flue to cool it down before collection, resulting in a loss of heat energy.

(Means for Solving the Problems) The present invention aims to develop a technology that can overcome the problems faced by the above-mentioned conventional technology, and focuses on the reducibility and sensible heat of exhaust gas generated in a smelting furnace. The various ores to be processed are introduced into the exhaust gas outlet duct above the smelting furnace mouth and fluidized, at least a portion of which is preliminarily reduced with high-temperature exhaust gas, and the sensible heat of the exhaust gas is recovered by heat exchange. This is a method designed to improve reaction efficiency and thermal efficiency during melting and reduction in a furnace, and the gist of the present invention is that reducing exhaust gas generated during refining can be recovered through a duct installed above the furnace mouth. When adding the metal oxide to be used for refining into the refining furnace during the refining process,
The metal oxide to be charged, which has been made fine in advance, is introduced into the duct, and the flow rate of the exhaust gas is controlled so that the fine-grained metal oxide forms a fluidized bed and stays in the duct. After the thermal reduction of the oxide has progressed, the generated preheated reduction product is dropped into the refining vessel by controlling the gas flow rate.

(Function) Regarding the background of the idea of the present invention, the following is an example of a technology in which metal oxides to be added from the furnace mouth during refining are preheated and reduced with converter exhaust gas before being added in steel refining in a converter. Nitori,
This will be explained below.

The reduction reaction of oxide ores such as Mn, Ni, and Cr added to the converter is an endothermic reaction and requires a large amount of heat. Therefore, by utilizing the sensible heat and reduction characteristics of the high-temperature exhaust gas containing a large amount of CO generated during converter refining, as shown in Figure 1, the above-mentioned oxide ore, which has been made into fine particles, is temporarily heated in the converter 1. The gas is introduced into the duct 2 provided on the opening, and a fluidized bed is formed by controlling the gas flow rate. After a certain period of time, when sufficient preheating and reduction have been achieved, the gas flow rate is reduced to preheat and reduce the gas flow rate. The reduction product is dropped into the molten steel in the converter to accomplish the final melt reduction.

In order to fluidize the oxide ore in the duct 2 above the furnace mouth, an exhaust gas control valve (not shown) is installed on the downstream side of the duct.
Alternatively, a blower (not shown) may be used to satisfy the following conditions.

That is, fluidization is possible by controlling the particle size, specific gravity, exhaust gas flow rate, and duct diameter (fluidized bed) of the upper part of the refining vessel (converter) within the range shown by the following formula.

U,, < U < U, (11U,,
f: Fluidization start speed U7. Fluidization terminal velocity (=8.72mf) d: particle size (m
) ρ,: Particle density (kg/rI?) ρ,: Exhaust gas density (kg/rr?) g: Gravitational acceleration (m/sec”) In the case of a converter, the particle size of the metal oxide is generally By controlling the amount of blowing gas and the amount of exhaust gas from the exhaust fan, it is possible to form, maintain, and release the fluidized bed.

(Example) Next, according to the present invention, using an 85 ton top/bottom blowing converter,
An example will be described in which fluidized bed preliminary reduction is performed in a duct to add NiO into the furnace during refining. The conditions for implementation are as shown below.

Molten metal in O converter: SO5304 (target Ni 8.5χ)
QNiO usage: 20kg/l (Ni 1.5χ
equivalent) specific gravity 5. O Ni = 75χ Particle size = Average particle size 0.5 *n(A
)0 = 25 χ ○Duct diameter: 2.7mφ, exhaust gas temperature: 1400'C
1○ Exhaust gas particle amount: 2100ONm3/H, duct part (
6.1 m/s), Ni0 grains were introduced and fluidized in the duct.

The fluidization time was 10 minutes, and the amount of gas blown from the lance tuyere at this time was: top blowing: 9ONm"O,/win% bottom blowing: 8ONm"Oz/min + 2ONm'N,/min
It is. Fluidization was completed by interrupting blowing. The exhaust gas flow rate at that time was 300ONm'/h (0.9m/s
) (Bottom blown Nt 5ONm"/win only). After dropping into the furnace, ot was blown again for refining.

Under the above implementation conditions, U IIf+Uf was as follows.

U-r (fluidization start speed) = 4.8 m/sUt
(Fluidization terminal velocity) =41.5 cm/5cl
-0.5 tn For comparison, an example is shown in which NiO with a particle size of 20 m5 (B) was introduced from the furnace mouth during refining.

FIG. 3 shows the relationship of particle size to exhaust gas temperature in this example. The exhaust gas temperature value is the average value measured by the three temperature measuring devices shown in FIG. 1 for 10 minutes from the NiO injection. Regarding (A) where the average particle diameter d=0.5 mm, the exhaust gas temperature has decreased, and as is clear from the above conditions, it is certain that heat exchange is occurring. On the other hand, in case (B) with a particle size of d=20 m, since it is not fluidized, the exhaust gas temperature is almost the same as in the case where NiO is not added.

Furthermore, Fig. 4 shows the relationship between coke consumption rate and particle size.

As is clear from this figure, the coke consumption rate is lower for the average particle diameter d = 0.5 wm (A), which is considered to be fluidized.

Therefore, by utilizing the fluidization of the metal oxide in the duct above the furnace mouth, it is possible to simultaneously reduce the basic unit of coke for reduction and coke for heating by 1.5 kg/l. Regarding the Nt yield, no significant difference was observed due to the difference in particle size, and both were at normal levels.

The effects of the above-mentioned embodiments will be even greater if they are used in large quantities by modifying the device, that is, by enlarging the duct that serves as the fluidized bed.

(Effects of the Invention) As explained above, according to the present invention, during the operation of the refining furnace, additives are preheated and reduced using the high-temperature exhaust gas generated during refining, so that the exhaust gas can be used effectively, and Excellent effects such as speeding up the refining reaction, improving yield, and improving unit heat consumption can be expected.

[Brief explanation of drawings]

Figure 1 is a route diagram showing how the method of the present invention is implemented in a converter, Figure 2 is a route diagram to explain the flow in the duct, and Figure 3 is a diagram showing the relationship between particle size and exhaust gas temperature. Figure 4 is a graph showing the relationship between particle size and coke consumption rate. ■...Converter 2...Duct 3...Temperature measuring device

Claims (1)

[Claims] 1. The reducing exhaust gas generated during refining is collected in the refining furnace through a duct installed above the furnace mouth. Before adding the metal oxide to be used for refining into the furnace during the refining process, the metal oxide is pulverized in advance. The metal oxide to be charged is introduced into the duct, and the flow rate of the exhaust gas is controlled so that the fine particulate metal oxide forms a fluidized bed and stays in the duct, and the metal oxide is heated. A method for adding metal oxide to a smelting furnace, which comprises, after progressing the reduction, dropping the generated preheated reduction product into a smelting container by controlling the gas flow rate.