JPS6362808A - Method for recovering valuable metal in molten slag during smelting and reduction refining - Google Patents

Abstract

PURPOSE:To safely and efficiently reduce and recover unreduced metal oxide by discharging a molten metal subjected to smelting and reduction from a converter, then blowing gaseous oxygen and pulverized coal through bottom blowing tuyeres to the residual molten slag in the converter. CONSTITUTION:The molten metal (crude molten steel) is discharged from the converter and the molten slag is held remaining in the converter at the point of the time when the smelting and reduction by the converter end. The oxygen and pulverized coal are blown through the bottom blowing tuyeres into the molten slag and while the slag is kept stirred, the reduction refining is executed. The oxygen and pulverized coal are required to be blown simultaneously from two systems of the bottom blowing tuyeres which can supply the oxygen and the pulverized coal simultaneously. The blowing rates thereof are adequately determined for a heat source, reduction, etc. The unreduced metal oxide is efficiently reduced and recovered by the above-mentioned method without having danger of bumping, etc.

Description

[Detailed Description of the Invention] (Field of Industrial Application) In recent years, in order to save energy including reducing electricity costs, oxides or semi-reduced oxides such as Cr ore and pellets have been added to hot metal. Melting reduction and refining operations are underway.

The technical content described in this specification regarding the method for recovering valuable metals in molten slag during smelting reduction smelting is particularly focused on reducing and recovering as much as possible unreduced metal oxides contained in molten slag generated during smelting reduction smelting using a converter. This paper proposes the development results of an advantageous method for doing so.

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

As an attempt to deal with this, for example, JP-A-54-158
In Publication No. 320, slag generated during melting of high chromium steel is left in a reaction vessel, hot metal, which is the iron source for the next heat, is injected into the reaction vessel and N2 is bubbled through the bottom blowing tuyere. It has been proposed to reduce and recover the Cr and Fe components.

In addition, in the refining of stainless steel, etc., at the final stage of refining,
A technique is known in which Cr oxides in slag are reduced and recovered by adding Si.

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

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

AI again! When +Si is added, it is advantageous for recovery from a small amount of slag, but in smelting reduction smelting that uses a large amount of oxides such as ores, a large amount of slag is generated.
It is difficult to improve the stirring efficiency of the slag, it takes a long time to reduce and recover the oxides, and the elements are expensive, resulting in poor productivity and economic efficiency.

The purpose of this invention is to effectively reduce and recover unreduced metal oxides remaining in molten slag generated during melting reduction refining of metal oxides, etc. in a converter, while avoiding the conventional problems described above. The point is to suggest an advantageous method for doing so.

(Means for Solving the Problems) This invention provides a method for recovering valuable metals from molten slag generated when metal oxides are charged into a bottom blowing converter or a top and bottom blowing converter for melting and reduction refining. After discharging the molten metal that has undergone melt reduction from the converter, oxygen gas and pulverized coal are blown into the remaining molten slag in the converter through the bottom blowhole to remove metal oxides remaining in the slag. This is a method for recovering valuable metals in molten slag during smelting reduction refining, which is characterized by recovery by reduction.

(Function) Normally, in the smelting and reduction refining of Cr ore, the final result is crude melting! Approximately 200 to 400 kg of slag is produced per 1i41, and 1 to 5% of unreduced Cr and Fe remain in these slags under atmospheric pressure.

This invention utilizes such unreduced C remaining in the slag.
The aim is to safely and efficiently reduce and recover rt Fe components.

The details of the reduction and recovery procedure will be explained below.

First, when the melting reduction refining in the converter is completed, the molten metal, that is, the crude molten steel, is discharged from the converter, leaving molten slag in the converter.

Oxygen and pulverized coal are then blown into the molten slag through the bottom blowhole to reduce and refine the slag while stirring.

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

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

In other words, pulverized coal is used as (1) a heat source to keep the slag in a molten state, (2) a reduction of metal oxides remaining in the slag, and (3) a compensation for the heat of decomposition and absorption during reduction. Further, oxygen is supplied in an amount necessary to burn the total amount of pulverized coal in (11 and (3)).

In this invention, pulverized coal is injected from the bottom blowing tuyere of the converter. The reason for this is that if it is added from the top of the converter, the pulverized coal will float on the slag, resulting in low reaction efficiency. There are problems such as deterioration of the addition yield because it is trapped in the exhaust gas, and in order to effectively avoid these problems, pulverized coal is blown through the bottom blowing tuyere.

Figure 1 shows pulverized coal 20-25 kg/slag t and oxygen gas 15-18 Nm for 30-5 Qt of slag produced by melting and reducing Cr ore using a bottom-blown converter.
3/Slag [, quicklime 150-200 kg/slag t
These are the results of an experiment in which the decreasing tendency of CrzOs in the slag was investigated under the supply conditions of .

In order to reduce and recover the oxides in the slag by blowing oxygen and pulverized coal through the bottom blowing tuyeres, it is of course necessary to keep the slag in a molten state, but in this experiment, when the temperature of the slag was raised to 1500°C or higher, It is clear that the content of Cr oxide in the slag is approximately 1% or less, and therefore it is effective to adjust the temperature to above this temperature.

(Example) 80 tons of hot metal 85 was charged into a top-bottom blowing converter, and Cr
Ore (T, Cr 40%) and auxiliary raw materials were semi-continuously charged to perform smelting reduction refining of CrK stone.

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

Table 1 During refining, the bottom blowers of the converter (7 in total: 3 for oxygen gas supply, 4 for pulverized coal supply with N2 gas as carrier gas)
Blow in oxygen gas 10,100N/win from
In addition, 17 ONm'/min of oxygen gas was blown from the top blowing lance to perform melting and reduction refining.

Theoretically, the Cr concentration in the reduced molten metal at the end of blowing (stopping) should have risen to 16.0%, but the Cr'774 degree in the obtained molten metal rose only to 13.3%. .

In addition, the molten metal composition at the time of blow-stopping is C: 4.0χ, Cr: 1
3.3%, Mn: 0.05%, p:o, o3%, S
: 0.03%. Furthermore, the T and Cr content in the slag 42.9% produced during refining was 4.66%.

After discharging the molten metal that has undergone smelting and reduction refining from the converter, (1) Pulverized coal to raise the slag temperature: 12 kg/slag t (target temperature 1550°C), (2)
Cr z O: + pulverized coal for reduction: 2 kg/slag t (31 Cr z 03 pulverized coal for decomposition heat compensation: 8.5
kg/t of slag and (11. (31) In order to burn the pulverized coal, 16.6 Nm3/t of slag was blown into each pulverized coal for 10 minutes at the same time from the bottom blowing tuyeres of the converter.

As a result, 3. Reduced molten metal of OL (C:5
．． 0%, Cr: 57%, Fe: 35%).

After that, the slag was collected and analyzed, and it was found that T and Cr were 0.
．． It was confirmed that it was 20%.

Figure 2 shows the oxygen gas and pulverized coal supply system for the converter used in this example, and Figures 3 (a) to (e) show the reduction and recovery procedure for metal oxides remaining in the slag. Shown schematically.

(Effects of the Invention) According to the present invention, when reducing and recovering unreduced metal oxides remaining in slag produced in smelting reduction refining using metal oxides such as Cr ore, Mn ore, Mo+V, etc., bumping etc. It is possible to carry out reduction and recovery efficiently without any danger, and it is also possible to significantly shorten the processing time required for reduction and recovery, thereby improving productivity.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between Cr oxide in slag and slag temperature, Figure 2 is a diagram of the supply system of oxygen gas and pulverized coal in the converter, and Figure 3 is a graph showing the recovery procedure for valuable metals in slag. FIG. Fig. 1 Slade 1 degree ('C) Fig. 2 (A) Omutsu East (d) Fig. 3

Claims (1)

[Claims] 1. When recovering valuable metals from the molten slag generated when metal oxides are charged into a bottom-blown converter or a top-bottom-blown converter for smelting and refining, the molten metal that has been smelted and reduced from the converter. smelting reduction smelting characterized by reducing and recovering metal oxides remaining in the slag by blowing oxygen gas and pulverized coal into the remaining molten slag in the converter through a bottom blowing tuyere after discharging the slag. Method for recovering valuable metals from molten slag.