JPH0610295B2 - Recovery method of valuable metal in molten slag during smelting reduction refining - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) In recent years, oxides such as Cr ore and pellets or semi-reduced oxides have been added to hot metal in order to save energy including reduction of electric power cost. The operation of smelting reduction refining is being carried out.

Regarding the method of recovering valuable metals in molten slag during smelting reduction refining, the technical content described in this specification is to reduce and recover as much as possible the unreduced metal oxides contained in the molten slag generated during smelting reduction refining by a converter. It proposes the development result about the advantageous method to do.

(Prior Art) In smelting reduction refining of Cr ore and the like, a large amount of slag is generated due to gangue and the like, and unreduced ore content remains in the slag. Therefore, it is necessary to recover the valuable metal from the slag as much as possible because it is not preferable from the viewpoint of resource saving to discard such a slag as it is.

As an attempt to cope with this, for example, in Japanese Patent Laid-Open No. 54-158320, the slag generated during the melting of high chromium steel is left in the reaction vessel, and the hot metal that is the iron source for the next heat is placed in this reaction vessel. Inject and bubble N ₂ through the bottom blowing tuyere
It has been proposed to reduce and recover Cr and Fe contents.

In addition, in the refining of stainless steel, etc.
A technique for reducing and recovering Cr oxide in slag by adding l and Si is known (see Japanese Patent Publication No. 60-7687).

(Problems to be Solved by the Invention) The conventional technique for reducing and recovering the unreduced oxide remaining in the molten slag as described above has the following problems.

That is, when only the slag is left in the reaction vessel and the hot metal of the next heat is charged therein, there is a risk of bumping or the like when the hot metal is charged.

Moreover, when adding Al and Si, it is advantageous for recovery from a small amount of slag, but a large amount of slag is generated in smelting reduction refining that uses a large amount of oxides such as ores, and the stirring efficiency of slag It is difficult to improve the production efficiency, it takes a long time to reduce and recover the oxide, and the element is expensive, which is disadvantageous in productivity and economic efficiency.

An object of the present invention is to effectively reduce and recover unreduced metal oxides remaining in the molten slag produced during the melt reduction refining of metal oxides in a converter while avoiding the conventional problems described above. We are proposing an advantageous method to do this.

(Means for Solving Problems) The present invention is for recovering valuable metals from molten slag generated when a metal oxide is put into a bottom-blown converter or a top-blown converter to perform smelting reduction refining. After discharging the molten metal that has undergone smelting reduction from the converter, oxygen gas and pulverized coal are blown through the bottom blowing tuyere into the residual molten slag in the converter to leave a metal oxide in the slag. Is a method for recovering valuable metals in molten slag during smelting reduction refining, which is characterized by reducing and recovering.

(Operation) Usually, in the smelting reduction refining of Cr ore, about 200 to 400 kg of slag is finally produced per ton of crude molten steel, and 1 to 5% of unreduced Cr, Fe is contained in these slags under atmospheric pressure. Minutes remain.

The invention is concerned with such unreduced C remaining in the slag.
It aims to safely and efficiently reduce and recover r, Fe, etc.

The reduction recovery procedure will be described in detail below.

First, when the smelting reduction refining by the converter is completed, the molten metal, that is, the crude molten steel is discharged from the converter, and the molten slag is left in the converter.

Then, oxygen and pulverized coal are blown into the molten slag through the bottom blowing tuyere to reduce and refine the slag while stirring.

Here, it is necessary that oxygen and pulverized coal can be simultaneously injected from two systems of bottom blowing tuyere that can be individually supplied into the converter.

Further, the amount of these blows is appropriately determined based on the following conditions.

That is, the pulverized coal is (1) for a heat source for keeping the slag in a molten state, (2) for reducing the residual metal oxide in the slag, and (3) for compensating the heat of decomposition and absorption during the reduction, Regarding oxygen, the amount necessary to burn the pulverized coal in the total amount of (1) and (3) is supplied.

In this invention, pulverized coal is blown from the bottom blowing tuyere of the converter, because the pulverized coal is floated on the slag when added from the upper part of the converter, the reaction efficiency is low, and the pulverized coal is Since it is trapped in the exhaust gas, there is a problem that the yield of addition is deteriorated. To effectively avoid these problems, pulverized coal is blown from the bottom blowing tuyere.

Fig. 1 shows slag 30 to 50t produced by smelting reduction refining of Cr ore using 85t bottom blowing converter, and pulverized coal 20 to 25k
g / slag t, oxygen gas 15-18Nm ³ / slag t, quick lime 15
Cr ₂ O ₃ in the slag under the supply condition of 0 to 200 kg / t slag
It is the experimental result which investigated the decreasing tendency of.

In order to blow oxygen and pulverized coal from the bottom blowing tuyere to reduce and recover the oxides in the slag, it is of course necessary to keep the slag in a molten state, but the temperature of the slag was set to 1500 ° C or higher by this experiment. In the case, the Cr oxide in the slag is almost 1
It is obvious that the temperature is less than or equal to%, and therefore, it is effective to adjust the temperature above this temperature.

(Example) 80 tons of hot metal was charged into an 85 tons top and bottom blowing converter, and Cr ore (T.
Cr ore was smelting-reduced and refined by adding Cr 40%) and auxiliary materials semi-continuously.

Table 1 shows the amounts of Cr ore and auxiliary materials used.

During refining, the bottom blowing tuyere of the converter (total 7: 3 for supplying oxygen gas, 4 for supplying pulverized coal using N ₂ gas as carrier gas)
Blowing oxygen gas 100 Nm ³ / min, from the book), from the top lance was also subjected to smelting reduction refining by blowing oxygen gas 170Nm ³ / min.

The theoretical concentration of Cr in the reduced melt at the end of blowing (stopping) should have risen to 16.0%, but
The Cr concentration increased only to 13.3%.

The molten metal content at the time of blowing is C: 4.0%, Cr: 13.3
%, Mn: 0.05%, P: 0.03%, S: 0.03%. In addition, T.Cr in 42.9t of slag produced during refining was 4.66%.

Therefore, after discharging the molten metal that has undergone smelting reduction refining from the converter, (1) pulverized coal for increasing the slag temperature: 12 kg / slag t (target temperature 1550 ° C), (2) pulverized coal for reducing Cr ₂ O ₃ : 2 kg / slag t (3) Cr ₂ O ₃ pulverized coal for compensating decomposition heat: 8.5 kg / slag t, and 16.6 Nm ³ / slag t for burning the pulverized coal of (1) and (3) Oxygen gas was blown into the bottom of the converter for 10 minutes at the same time.

As a result, 3.0t of reduced molten metal (C: 5.0
%, Cr: 57%, Fe: 35%) could be recovered.

After that, when slag was collected and analyzed, it was confirmed that T.Cr was 0.20%.

It should be noted that FIG. 2 shows the oxygen gas and pulverized coal supply system of the converter used in this example, and FIGS. 3 (a) to (e) show the reduction and recovery procedure of the metal oxides remaining in the slag. It is shown schematically.

(Effect of the Invention) According to the present invention, when the unreduced metal oxide remaining in the slag produced by the smelting reduction refining using metal oxides such as Cr ore, Mn ore, Mo, V is bumped, etc. It is possible to efficiently carry out reduction and recovery without the risk of
Further, the processing time required for reduction and recovery can be significantly shortened to improve productivity.

[Brief description of drawings]

Fig. 1 is a graph showing the relationship between Cr oxide in slag and slag temperature, Fig. 2 is a supply system diagram of oxygen gas and pulverized coal in a converter, and Fig. 3 is a recovery procedure of valuable metals in slag. It is the figure shown.

Claims (1)

[Claims] 1. When recovering valuable metal from molten slag generated when a metal oxide is introduced into a bottom-blown converter or a top-blown converter to perform smelting reduction refining, smelting reduction is performed from the converter. After discharging the finished molten metal, oxygen gas and pulverized coal are blown into the residual molten slag in the converter through a bottom blowing tuyere to reduce and recover the metal oxide remaining in the slag. A method for recovering valuable metals in molten slag during smelting reduction refining.