JPS59110712A - Reduction of powdery granular ore - Google Patents

Abstract

PURPOSE:To effectively steadily carry out the preliminary reduction of ore, by using shaft type evolved gas as reduction gas in countercurrently moving the ore and reduction gas in plural cyclones arranged in series by multi-steps. CONSTITUTION:Powdery granular ore is charged into the top stream cyclone 23 of preliminary reduction unit 2 from a raw material hopper 1 and at that time the reducing gas evolved from a cyclone 22 on down stream side is used as carrier gas. Further, the high temperature reducing gas evolved from a fusion reduction furnace 3 is utilized for the cyclone 21 positioned on the downest stream side. The reducing gas successively moves to 22 and 23 cyclones on upper stream side, flows into their insides respectively taking unreduced ore powder therewith, repeats the heating, reduction and separation and transfers the preliminary reduction product having reached required reducibility to the tuyere part of fusion reduction furance 3 via a discharge pipe 6. Thus, stable operation, high gas utilization ratio and the improvement of reducibility can be achieved.

Description

[Detailed description of the invention] The present invention relates to a method for reducing powdery ore,
In particular, it relates to a technology for obtaining reduction products by a method that combines preliminary reduction using a suspension preheater system using cyclones installed in multiple stages in series and vertical smelting reduction using a carbonaceous packed bed.

In recent years, the raw material ores that serve as the main source of various metal oxides, including iron ore, have been decreasing, with powder and granular ores being more common than lump ores, and the proportion is expected to continue to increase in the future. It will be done. A common method for smelting powder or granular ore is to pre-reduce the powder or granular ore using a fluidized bed, and then melt and reduce the pre-reduced ore in an electric furnace, converter, or other melting furnace.

In this case, the pre-reduced ore is agglomerated by adding a binder,
Many methods involve melting and reducing the agglomerates in a melting furnace. However, this method not only requires materials for agglomeration, processing costs, processing energy, etc., but also requires a firing furnace if firing is required after agglomeration. Another drawback is that the cost of processing SOx and dust in the gas emitted from the gas increases considerably.In addition to the above methods, arc furnaces, plasma, or furnaces that use pure oxygen are also used. Therefore, a method has been proposed in which the pre-reduced ore is smelted and reduced without agglomeration or calcination, but the method using an arc furnace would not only consume a huge amount of electricity but also Furthermore, the method using a furnace that uses plasma consumes so much power that it is difficult to apply it on an industrial scale at present.Furthermore, the method using a furnace that uses pure oxygen does not allow high-temperature atmospheres. Although it is easy to obtain, it is difficult to maintain a reducing atmosphere and the amount of powder used is large, all of which involve problems that require technical solutions.

Therefore, recently, methods using pre-reduction and smelting reduction have been attracting attention as a reduction technology for powder and granular ores that does not require electricity. For example, a combination of a fluidized bed pre-reduction furnace and a vertical smelting reduction furnace. This is a method of producing ferroalloys directly from powdered ore using the equipment described above. This known method utilizes the high-temperature exhaust gas of a smelting reduction furnace as a source of the reducing agent and heat necessary for the pre-reduction of metal oxide-containing ores, and is the most popular method for pre-reduction in a fluidized bed format. ,
Since the granular ore can be used directly without agglomeration, it is possible to produce molten metal at a lower cost than the above-mentioned method.

The main conditions necessary for the fluidized bed as a pre-reduction furnace in the above-mentioned known method are: (8) Uniform and stable fluidization phenomenon can be obtained; (8) uniform and stable fluidization phenomenon can be obtained;
(4) The required reduction rate can be obtained even with a short residence time (
(5) generation of less dust due to particles flying out of the fluidized bed, etc.0 However, generally speaking, these various conditions are necessary for preliminary reduction. The higher the temperature of the fluidized bed, the more difficult it is to maintain it, and if a large amount of dust is included in the fluidized gas generated from the smelting reduction furnace (C8), the difficulty of operating the bed will be further increased. For example, dispersion as an aeration device has the disadvantage that dust and condensate deposits may occur, leading to clogging, and this requires the development of various new methods and devices.

In order to overcome the above-mentioned drawbacks of the prior art, the present invention advantageously utilizes the characteristics of the smelting reduction technology using a vertical furnace, while replacing the fluidized bed pre-reduction furnace with a suspension-type pre-reduction furnace which does not have the above-mentioned drawbacks. We propose a reduction method that is convenient for achieving stable operation, high gas utilization rate, and improvement in reduction rate by implementing a reduction method that performs reduction.

FIG. 1 shows a schematic diagram of a reduction system consisting of a preliminary reduction stage and a melt reduction stage suitable for carrying out the present invention.

1 in the figure shows a powder ore raw material hopper, a 2t-J suspension type preliminary reduction device, and an 8-digit melting system! l
I reduction furnace.

The preliminary reduction device 2 includes a plurality of cyclones 21 and 22.
．． 28 are connected in series through a transfer pipe (4), so that the reducing gas and the granular ore react in contact with each other as they move in opposite directions, and the reduction rate increases sequentially. 0 In other words, when powder and granular ore are entrained with reducing gas and flowed into the cyclone 2'1, the incoming airflow swirls along the inner wall surface of the cylinder, but at that time, it is influenced by centrifugal force. The ore falls, while the reducing gas rises.In the course of such contact and separation, and as it moves between the cyclones 21 to 28, the required reduction rate is determined. A prereduction product is obtained.

The above melting reduction furnace 8 is a development of the invention of Japanese Patent Application No. 56-68294, which was previously proposed by the present inventors.
While a full packed bed of carbonaceous solid reducing agent is formed in the vertical furnace, reducing exhaust gas is discharged from the electric furnace through multiple groups of panels arranged in multiple stages on the lower body wall of the electric furnace. Partially reduced ore, which is obtained by pre-reducing powder and granular ore using
This furnace completely melts and reduces the pre-reduced ore by blowing air at a high temperature of about 00° C. or oxygen-enriched air into a vertical furnace under air flow.

In the lower part of the trunk wall of the vertical melting reduction furnace 8, a plurality of slats 4 and Φ' are arranged, for example, in two upper and lower stages, and air is heated, for example, through these slats 4 and 4'. By blowing downward, the packed bed in the furnace is ignited, and the reducing exhaust gas generated in the furnace is thus generated through the exhaust port 5, and is introduced into the preliminary reduction device for use.

The packed bed thus formed in the furnace generates a raceway near the tuyere tip similar to that at the tip of a blast furnace tuyere, forming a high temperature area, and the powder and granular ore that are blown into this area together with the preheated air are It is immediately heated and easily melted, and as it drips into the lower part of the furnace, it is reduced to produce molten metal and molten slag for smelting. All the molten metal accumulated in the hearth is removed from the furnace in a timely manner. The same applies to molten slag.

In addition, the area around the raceway that forms the high temperature region of the packed layer has a low dust content in the combustion atmosphere of the lumpy carbon-based reducing agent, that is, the oxygen partial pressure is low. The reduction of the powder and granular ore to be melted is carried out very favorably.

Next, preferred embodiments of the present invention will be described.

Powdered or granular ore is supplied from the raw material hopper 1 into the most upstream cyclone 23 of the preliminary reduction device 2. At this time, the gas to be transported is the reducing gas generated from the cyclone 22 located on the downstream side. On the other hand, the cyclone 21 located on the most downstream side has the melting reduction furnace 3
Utilizing the generated high temperature reducing gas, the reducing gas is Jl.
Moving on to cyclone 22.28 located on the i-th upstream side,
All the unreduced ore powder flows into the interior and is heated.
The reduction-separation process is repeated to produce a pre-reduced product that has reached a desired reduction rate, and is transported to the 3 tuyeres of the smelting reduction furnace through the discharge pipe 6'fr.

Therefore, the flow of granular ore gradually moves downstream from the most upstream cyclone 28, whereas the reducing gas flows into the -H most downstream cyclone 21 and then gradually moves upstream 111! It takes the form of countercurrent movement toward l, and pre-reduction proceeds during the entire transfer. After the preliminary reduction stage is completed, heated air is blown into the melting reduction furnace 8 as a reactive carrier gas to perform final melting reduction, and the molten metal and slag are discharged from the tapping lower.

Note that the cyclone described herein is not limited to eight stages, and can be arranged in accordance with ore conditions and the like.

Note that the exhaust gas generated by the smelting reduction furnace supplied to the pre-reduction device 2 may be enriched with hydrocarbons such as methane, for example, when pre-reducing ores that are difficult to reduce (chromium ore, etc.). good.

In addition, to blow and charge powder and granular ore into the smelting reduction furnace 8 using heated air, the upper panel group 4 is used. ~Show T to Marty Harime Utsumugi%
*Forehearth from 9 to the snout to the bad bird (Blow into the C),
There is no need for a strong solid reducing agent as in blast furnaces, and the carbonaceous solid reducing agent used in the packed bed may not be expensive strongly caking coal, but weakly caking coal or non-caking coal. Charcoal can also be used satisfactorily and is economically advantageous.

In this invention, the tuyere groups 4, 4'' are arranged, for example, in two stages, upper and lower, so that the ore that is blown into the furnace together with the preheated air through these tuyere groups or only through the tuyere 4 melts near the tips of the tuyeres. If the amount of heat required for reduction is insufficient, even if melting occurs near the tip of the tuyere, the hearth will cool down to the point where insufficient heat is supplied on the way to the bottom of the hearth, inhibiting reduction. In this sense, powder and granular ore are mainly supplied from the upper tuyere group 4, and the hearth is heated to a high temperature by the lower tuyere group 4'. It is desirable to secure the amount of heat necessary for reducing the melt that is dropped.

Next, according to the method of the present invention, ferrochrome was produced using a test furnace, and the results will be reported.

(1) Pre-reduction device cyclone... 8 bases Brand of raw material... Particle size of chromium ore raw material from Philippines: 0.4 m or less Raw material supply amount 2850 yen/hr Pre-reduction rate: 80 yen (8) Melting Reduction furnace carbon-based solid reducing agent; Coke particle diameter: 20-49 mm Supply amount = 550 Ume/hr Air flow rate: 1B70 Nm/hr Air blowing temperature: 945°C Air blowing tuyeres: 8 each (4 each on the upper and lower rows) (Supplying preliminary reduction products) (8) 7Erochrome production powder: 195 to 9/group
Composition: 0r54.5%, 06.1%, Si5.8
% Slag discharge amount: 295 kf/hr As explained above, according to the present invention, (1) the waste gas generated in the smelting reduction furnace is effectively utilized, so that the sensible heat recovery rate is increased.

(IA) Multi-stage pre-reduction equipment can be easily achieved, and since the ore and gas are moved in countercurrent flow, as the reduction progresses, the gas comes into contact with a gas having a higher reducing ability, which improves the efficiency of gas utilization. In addition to improving stability, a stable and highly prereduced product can be obtained.

(8) Unlike using a fluidized bed, a gas distribution plate is not required, so troubles such as clogging and sintering are eliminated, and smooth operation is possible.

You can expect similar effects.

[Brief explanation of drawings]

Part 1 (2) is a schematic diagram showing the system system of the present invention. l... Raw material hopper 2... Preliminary reduction device 8.
...Melting reduction furnace. (11) Figure 1 (12) 0 Inventor Tsutomu Fujita Inside the Chiba Works of Kawasaki Steel Co., Ltd., 1 Kawasaki-cho, Chiba City 0 Inventor Shunji Hamada Inside the Chiba Works of Kawasaki Steel Co., Ltd., 1 Kawasaki-cho, Chiba City

Claims (1)

[Claims] 1. A pre-reduction stage in which preheating and reduction are performed while the ore and reducing gas are brought into contact with each other in a flowing flow between a plurality of cyclones installed in multiple stages in series; ) While filling with a carbon-based solid reducing agent, the powder and granular ore of the preliminary reduction product are injected into the furnace together with oxidizing gas through tuyeres installed in multiple stages above and below the lower part of the furnace wall for reduction. , a smelting-reduction stage that leads to a melting reaction; and a granular ore characterized in that reduction is carried out by circulating the gas generated in the vertical furnace for smelting-reduction as a reducing gas in the preliminary reduction stage. How to get back.