JPS59162213A - Operating furnace of melt reduction furnace - Google Patents

Abstract

PURPOSE:To accelerate reduction with a min. amt of flux and to discharge smoothly slag in a method for charging powder ore and flux to a titled furnace contg. a C contg. solid reducing agent and provided with plural upper and lower stages positioned near a tuyere by blowing specifically the flux. CONSTITUTION:A C contg. solid reducing agent is charged into a vertical melt reduction furnace 1 to form a packed bed. Powder ore and a flux for accelerating the reduction thereof are supplied by a device 7 to a fluidized preliminary reduction furnace 6, where the ore is preliminarily reduced and heated by using the high temp. waste gas generated in the furnace 1. The preliminarily reduced ore and flux are transferred through a discharging port 8 to the upper and middle tuyeres 3, 4 in the lower part of the furnace and are blown together with the hot air from a hot stove 11 into the furnace 1. These materials are immediately melted, and while the molten material drops in the reducing agent packed bed in the lower part of the furnace 1, the materials are reduced and the molten metal and slag are formed. A flux for adjusting the final slag component in the hopper 9 is blown together with the hot air through a tuyere 5 into the furnace 1 to discharge the slag smoothly. The molten metal is melted together with the flux and is finally accumulated in the hearth part. The molten metal is properly tapped through a discharging port 10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a vertical smelting reduction furnace which contains a packed bed of a carbon-based solid reducing agent and has a plurality of slats arranged vertically in two or, if necessary, three stages. In the operating method of a smelting reduction furnace that produces molten metal by blowing powdered ore through the tuyeres, the reduction of powdery ore is promoted with the minimum amount of flux injection, and the slag is smoothly discharged. The present invention relates to a method of operating a smelting and reducing furnace, which allows for a method of blowing 7 lux from the tuyere of the smelting and reducing furnace.

In recent years, the raw material ores made of various metal oxides, including iron ore, have become more granular ores than lumpy ores, and the proportion is expected to continue to increase in the future. Conventionally, the common method for smelting using powdery ore is to pre-reduce the powdery 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, there are many smelting methods in which a binder is added to the pre-reduced ore to agglomerate it, and the agglomerate is melted and reduced in a melting furnace.

However, this method not only requires materials for agglomeration, processing costs, and processing energy, but also requires firing after agglomeration. Another drawback is that the cost for treating NOx, SOx, dust, etc. in the gas discharged from the furnace is large.

In addition to the above-mentioned methods, methods have also been proposed in which the pre-reduced ore is melted and reduced without agglomeration or calcination using an arc furnace or a furnace that uses plasma or pure oxygen. The method using plasma not only consumes a huge amount of power, but also has restrictions on location, and the method using a furnace that uses plasma consumes so much power that it is currently difficult to apply on an industrial scale. Furthermore, with the method using a furnace that uses pure oxygen, even though it is easy to obtain a high-temperature atmosphere, it is difficult to maintain a reducing atmosphere and the amount of oxygen used increases, all of which require technical solutions. It's fraught with problems.

By the way, the present inventors have previously proposed in Japanese Patent Application No. 56-63294, in which a packed bed of a carbonaceous solid reducing agent is continuously formed inside a vertical furnace, in order to advantageously solve the above-mentioned problems. Powder and granular ore were pre-reduced using the reducing exhaust gas discharged from the vertical furnace through a plurality of blades (groups of blades) arranged on the lower body wall of the vertical furnace in two lower stages. The partially reduced ore is heated with hot air consisting of high-temperature air or oxygen-enriched air at a temperature of 300 to 1300°C, with additional flux added if necessary. We proposed a method for melting and reducing powder and granular ores using a vertical furnace.

In the above method, the charge is transported by a preheated oxidizing gas stream and blown into the vertical melting reduction furnace from the tuyere group. The carbon-based solid reducing agent is dropped into the high-temperature region of a packed bed, and is melted and reduced, stored in the hearth, and taken out of the furnace as appropriate. The development of the smelting reduction method has made it possible to smelt powder and granular ores extremely effectively.

When powdered ores are smelted and reduced in the vertical smelting reduction furnace described above, an appropriate flux is added to facilitate the melting of these ores in the carbon-based solid reducing agent packed bed to facilitate reduction. It is necessary to ensure a residence time in the packed bed for sufficient reduction within the slag and to ensure conditions under which the reduced slag can be easily slaged off.

In other words, in the smelting reduction method described in -, in the process in which the molten ore to which Franks has been added is directly reduced in the packed bed of carbon-based solid reducing agent formed from the upper layer to the hearth, melted and dripped, and the slag is removed. It was necessary to reduce the base rate, reduce the amount of added flux as much as possible, and develop an operating method that would constantly maintain smooth slag drainage. In this case, lowering the slag ratio directly reduces the energy required to produce molten metal.

However, the problem of ensuring operating conditions for smelting reduction reactors has been shown to be a very complex problem, based on high-temperature simulation experiments in the laboratory and extensive experiments in small operating reactors. .

For example, when the flux composition is changed, its reducing property changes, gas foaming changes accordingly, and the residence time in the carbon-based solid reducing agent packed bed changes significantly.

In addition, due to the high temperature, 5i02, MgO, and A
Texture 203 is considerably vaporized and the slag composition changes.

Furthermore, there are complex problems such as the characteristic values of the initial and intermediate slag, especially the surface tension, contact angle, viscosity, etc., changing as the reduction rate of the molten ore changes, which greatly changes the dripping behavior.

The present inventors found that among these very complicated phenomena in the smelting reduction method, (1) If the molten ore to which flux is added is very easily soluble, the packed bed can be dropped quickly and the operating efficiency can be improved. However, the reduction rate decreases (2) If the molten ore is extremely difficult to melt, the packed bed must be heated to a higher temperature, which increases energy consumption and reduces productivity. (3) Addition As the amount of flux increases, the apparent loss of slag increases and the reduction rate of molten ore decreases. In order to be used, the melting temperature of this final slag must be below 155°C;
It is desirable that the viscosity of the slag is 10 poise or less at 1550'0 (the viscosity of the slag is 1550
The inventors have confirmed that when the temperature exceeds lo poise, it becomes very difficult to remove the slag. ) (5) The composition of the flux that controls the dripping state of molten ore in the packed bed and increases the reduction rate is different from the composition of the flux that must be added to smooth the removal of slag. I discovered 5 points.

The present inventors further continued experiments based on the above discovery and completed the present invention. 5 The gist of the present invention is that powdered ore and 7 lux are mixed together with hot air in a vertical melting reduction furnace containing a packed bed of a carbon-based solid reducing agent and provided with a plurality of layers in the vertical direction. In a method of operating a smelting reduction furnace that produces molten metal by blowing in molten metal, a flux for promoting reduction is injected from the tuyeres in the L section, and a flux for smoothing the slag removal from the bottom tuyere is injected. A method of operating a smelting reduction furnace is provided.

In the present invention, the amount of flux blown into the melting reduction furnace is significantly reduced compared to the operating method in which powdered ore and flux are evenly blown into the tuyere from the upper stage or from the upper/middle stage tuyeres. In other words, we changed the method of injecting flux by excluding the bottom tuyere, while the powdered ore injected from the two tuyeres melts at the high temperature at the tip of the tuyere, and the packed bed of carbon-based solid reducing agent is dropped. Ensure that sufficient reduction is achieved and that the amount of flux blown into the slag is minimized, and at the same time, the conditions for smooth removal of slag from the bottom layer are satisfied and the amount of blown flux is minimized. In this case, the total amount of flax injected will decrease and the reduction rate of the molten ore will increase. CaO-based fusix is used as the reduction promoting flux that is injected from the upper tuyere, that is, the tuyeres except for the bottom tuyere, and is a flux that lowers the viscosity of the slag that is blown in from the bottom tuyere and allows for smooth slag removal. For example, by using an operating method using a 5-inch flux, it is possible to easily obtain results in which the overall amount of flux blown is reduced and the reduction rate is increased.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a system diagram of the apparatus used to carry out the method of the present invention. A carbon-based solid reducing agent, preferably lump coke, is charged into the vertical smelting reduction furnace 1 via a charging device 2, and a reducing agent packed layer is formed in the vertical smelting reduction furnace 1. In the lower part of the vertical melting reduction furnace 1, there are 2 to 3 tiers of slats. −
H. The middle stage has tuyeres 3 and 4 for blowing the pre-reduced ore and the flux that promotes its reduction together with hot air, and the bottom stage has tuyeres for blowing in flux and hot air to be added to smooth the removal of slag. It is 5.

Powdered ore and flux added to promote its reduction are supplied to a fluidized pre-reduction furnace 6 by a supply device 7,
In this preliminary reduction furnace 6, preliminary reduction and heating is performed using the high temperature exhaust gas generated in the vertical melting reduction furnace 1.

The pre-reduced ore and flux are transferred from the outlet 8 of the pre-reduction furnace 6 to the upper and middle tuyeres 3 and 4 by applying the principles of gravity transport and gas transport.

The vicinity of the tuyere tips of the upper tuyere 1 3, middle tuyere 4, and bottom tuyere 5 in the vertical melting reduction furnace 1 are heated by the hot air blown from the hot blast furnace 11, similar to the vicinity of the tuyere tips of a blast furnace. A raceway is formed and a high temperature region of 2000 to 2500° C. is formed, and the pre-reduced ore and flux blown into this region together with hot air or added oxygen are immediately heated and easily melted. Then, while dropping the carbon-based solid reducing agent packed bed at the lower part of the melting reduction furnace 1, it is reduced to produce molten metal and molten slag, and smelting is performed. A flux hopper 9 for adjusting the final slag component is installed in the lowermost tuyere 5.
Supplies flux to facilitate smooth removal of slag. The molten metal is melted together with the flux injected from the lowermost tuyere 5, and is finally accumulated in the hearth, and is then passed through the tap hole 10.
The hot water is discharged outside the furnace in a more timely manner.

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

EXAMPLE The present invention was carried out in a test reactor using the system system shown in FIG. The manufacturing metal is Fe-B-5i from colemanite ore.
-A C-based alloy was produced.

As a comparative example, an operating method was also implemented in which flux was uniformly supplied from each layer.

The operating conditions are as follows.

(1) Boron-containing ore: Colemanite Particle size: 200 mesh or less Supply to the L11 tuyere: l 70 kg/hr
(2) Iron ore brand: Brazil MBR Ore particle size: 2 mm or less Amount supplied to the preliminary reduction furnace: 740 kg/hr Amount supplied to the 1-1 middle stage: 600 kg/hr Preliminary reduction rate
= 65% (3) Flux (A) uniform supply method (comparative example) Limestone: 150 kg/hr Silica stone: 126 kg/hr Blow-in siding ・Flux injection percentage of upper and middle siding total: 276 kg/hr (
B) Split supply method (method of the present invention) ■ Limestone + 35 kg/hr Blow tuyeres: Upper and middle tuyere ■ Limestone: 35 kg/hr Silica stone: 82 kg/hr Blow tuyeres: Total of bottom tuyere Flux injection amount: 152 kg/hr (4
) Type of carbon-based solid reducing agent: Coke particle size: 20~
30mm Supply % + 603kg/hr (5) Air blowing i to the vertical melting reduction furnace: 180ONrrf/
hr Air blowing temperature: 900°C Air blowing size: L stage, lower stage, bottom stage each 4 each, total 12 pieces (6) Fe -B-3i -C molten metal production amount and slag discharge amount (A) Uniform flux supply method ( Comparative example) 430 kg
/hr (Component B = 3.0%, 5i = 2.8%,
C=3.0%, Fe=Bal) Slag discharge amount:
434kg/hr (B) Flux divided supply method (method of the present invention) 450
kg/hr (component B = 5.1%, Si -2,
1%, C=2.8%, Fe=Bal) Slag discharge amount:
351 kg/hr When injecting flux into the smelting reduction furnace through the multi-stage tuyeres as described below, the flux suitable for melting and reduction in the packed bed is injected from the tuyeres other than the lowest stage, and the slag is discharged from the lowest stage tuyeres. Adjust the final slag to meet the requirements for slag.Inject flux.By operating the smelting reduction furnace, the total amount of flux injected is reduced, which not only lowers the energy cost of molten metal production but also increases the reduction rate. It has become clear that it has the effect of

[Brief explanation of the drawing]

FIG. 1 is a system diagram of the apparatus used to carry out the method of the present invention. 1... Vertical melting reduction furnace, 2... Raw material supply device, 3.
4.5... Window, 6... Preliminary reduction furnace, 7... Ore/flux supply device, 8... Preliminary reduced ore/flux discharge port, 9... 18
．． 4” Franks hopper for adjusting slag components, 10...
・Molten metal/slag discharge port, 11...Hot stove applicant: Kawasaki Steel Corporation Agent Patent attorney: Yoshio Kosugi, 1 Kawasaki-cho, Chiba City, Kawasaki Steel Corporation, Chiba Works [phase] Inventor: Shunji Hamada, Chiba City Kawasakicho 1 Kawasaki Steel Corporation Chiba Works

Claims (1)

[Claims] ■ Molten metal is produced by blowing powdered ore and flux together with hot air into a vertical smelting reduction furnace that contains a packed bed of carbon-based solid reducing agent and has multiple layers of panels in the vertical direction. A method for operating a smelting and reducing furnace, characterized in that a flux for promoting reduction is injected from an upper tuyere, and a flux for smoothing slag removal is injected from a tuyere at the bottom. .