JPH0314889B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a rigid smelting reduction device which has a packed bed of a carbon-based solid reducing agent built therein and has a plurality of tuyeres arranged vertically in two or, if necessary, three stages. In the operating method of a smelting reduction furnace, which uses a furnace to produce molten metal by blowing powdered ore through the tuyere, 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 for operating a smelting-reduction furnace, which involves a method of injecting flux from the tuyere of the smelting-reduction furnace to maintain a high temperature.

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 of treating _NOx , _SOx , dust, etc. in the gas discharged from the furnace is considerable.

In addition to the above-mentioned methods, methods have 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, although 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 cannot be solved technologically. It is fraught with problems.

By the way, the present inventors previously attempted to solve the above-mentioned problems advantageously by continuously forming a packed bed of carbonaceous solid reducing agent inside a vertical furnace in Japanese Patent Application Laid-open No. 57-198205. Partially reduced ore is produced by pre-reducing powder and granular ore using the reducing exhaust gas discharged from the vertical furnace through a plurality of tuyere groups arranged in two stages, upper and lower, on the lower body wall of the vertical furnace. , add more flux if necessary to 300~
A method for melting and reducing powder and granular ores in a vertical furnace, in which the above partially reduced ore is melted and reduced by blowing hot air made of high-temperature air or oxygen-enriched air into a vertical furnace under air flow conveying air at a temperature of 1300°C. Proposed.

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

When smelting and reducing powdery ores in the above-mentioned rigid smelting reduction furnace, an appropriate flux is added to facilitate the melting of these ores in the carbon-based solid reducing agent packed bed, making it easier to reduce them, and 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 above-mentioned smelting reduction method, in the packed bed of carbon-based solid reducing agent formed from the upper tuyere to the hearth, the molten ore to which flux has been added is directly reduced, and in the process of melting and dripping and being discharged, the reduction rate increases. It was necessary to increase the amount of flux added and to reduce the amount of added flux as much as possible, and to develop an operating method that would always 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 the operating conditions of the smelting reduction furnace has been found to be a very complex problem from high temperature simulation experiments in the laboratory and extensive experiments in small operating furnaces.

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

In addition, due to the high temperature, SiO ₂ and MgO in the slag
Al ₂ O ₃ is considerably vaporized and the slag composition changes.

Furthermore, as the reduction rate of the molten ore changes, the characteristic values of the slag in the initial and intermediate stages, especially the surface tension, contact angle, viscosity, etc., change, resulting in a large change in the dripping behavior, which poses complex problems.

Among these extremely complex phenomena in the smelting reduction process, the present inventors found that (1) If the molten ore to which flux has been added is highly soluble, the packed bed can be dripped quickly and the operating efficiency can be improved. (2) If the molten ore is very difficult to melt, the packed bed must be heated to a higher temperature, which increases energy consumption and reduces productivity. 3) If more fluxes are added, the sensible heat loss of the slag will increase and the reduction rate of the molten ore will decrease; (4) The final slag that has accumulated at the bottom of the packed bed consisting of a high-temperature carbon-based solid reducing agent will In order to smoothly and steadily discharge the slag, it is desirable that the melting temperature of this final slag is 1550℃ or less, and that its viscosity is 10 poise or less at 1550℃ (the viscosity of the slag is 10 poise or less at 1550℃). (5) Flux composition that controls the dripping state of molten ore in the packed bed and increases the reduction rate. The following five points were discovered: the composition of the flux is different from that of the flux that must be added to facilitate slag drainage.

The present inventors continued experiments based on the above discoveries and completed the present invention.

The present invention melts powdered ore by blowing hot air together with powdered ore and flux into a vertical melting reduction furnace that contains a packed bed of a carbon-based solid reducing agent and has tuyere groups arranged in multiple stages in the vertical direction. In the operating method of a smelting reduction furnace for manufacturing metals, basic flux for promoting reduction, such as CaO-based flux, is injected together with powdered ore from the upper tuyere, and acidic flux is used to smoothly discharge the slag from the lowermost tuyere. ,for example
A method of operating a smelting reduction furnace characterized by injecting SiO ₂ -based flux.

In the present invention, the amount of flux blown into the smelting reduction furnace is significantly smaller than that of 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, the flux injection method is such that the powdered ore injected from the upper tuyere, excluding the bottom tuyere, is melted at the high temperature at the tip of the tuyere, and is sufficiently reduced while the packed bed of carbon-based solid reducing agent is dropped. and the amount of flux blown into the tuyere is set to a minimum, while the condition that slag slag is smoothly discharged from the lowest tuyere is satisfied, and the amount of flux blown into the tuyere is set to the minimum. In this case, the total amount of flux injected is reduced and the reduction rate of the molten ore is increased. A CaO-based flux is used as the reduction promoting flux injected from the upper tuyere, that is, the tuyere except for the bottom tuyere, to reduce the viscosity of the slag injected from the bottom tuyere and to ensure smooth slag removal. By using an operation method that uses SiO ₂ -based flux as the flux to be used, 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. Two to three stages of tuyeres are provided in the lower part of the vertical melting reduction furnace 1. The upper and middle tuyeres are tuyeres 3 and 4, through which hot air is blown in to pre-reduced ore and the flux that promotes its reduction, and the lowest tuyere is tuyere 5, through which hot air and flux added to smooth the removal of slag are blown in. It is.

Powdered ore and flux added to promote its reduction are supplied to a fluidized pre-reduction furnace 6 by a supply device 7, and in this pre-reduction furnace 6, high-temperature exhaust gas generated in the vertical smelting reduction furnace 1 is fed to the fluidized pre-reduction furnace 6. It is pre-reduced and heated using

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

A hot blast furnace 1 is installed near the tips of the upper tuyere 3, the middle tuyere 4, and the lower tuyere 5 in the vertical smelting reduction furnace 1.
The hot air blown from 1 generates raceways similar to those near the tip of the blast furnace tuyere, and
A high temperature region of 0.degree. C. is formed, and the pre-reduced ore and flux blown into this region with hot air or added oxygen are immediately heated and easily melted. Then, while dropping the carbon-based solid reducing agent filling bed in the lower part of the melting reduction furnace 1, it is reduced to produce molten metal and molten slag, and smelting is performed. Flux is supplied to the lowermost tuyere 5 from a flux hopper 9 for final slag component adjustment to facilitate smooth removal of slag. The molten metal is melted together with the flux injected from the lowermost tuyere 5 and is finally stored in the hearth, and is tapped out of the furnace from the tap 10 at a timely manner.

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

EXAMPLE The present invention was implemented in a test reactor using the system system shown in FIG. The manufacturing metal is from colemanite ore.
A Fe-B-Si-C alloy was manufactured.

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

The operating conditions and results are as follows.

(1) Boron-containing ore: colemanite particle size: 200 mesh or less Supply amount to the upper and middle tuyeres: 170Kg/hr (2) Iron ore brand: Brazil MBR Ore particle size: 2 mm or less Supply amount to the pre-reduction furnace: 740Kg/hr Supply amount to upper and middle tuyeres: 600Kg/hr Preliminary reduction rate: 65% (3) Flux (A) Uniform supply method (comparative example) Limestone: 150Kg/hr Silica stone: 126Kg/hr Blowing blade Mouth: Upper and middle tuyere total flux injection amount: 276Kg/hr (B) Split supply method (method of the present invention) Limestone: 35Kg/hr Injection tuyere: Upper and middle tuyere Limestone: 35Kg/hr Silica stone : 82Kg/hr Injection tuyere: Total amount of flux injected into the bottom tuyere: 152Kg/hr (4) Type of carbon-based solid reducing agent: Coke particle size: 20-30mm Supply amount: 603Kg/hr (5) Air flow rate to the rigid smelting reduction furnace: 1800Nm ³ /hr Air blowing temperature: 900℃ Air tuyere: 4 each in the upper, lower, and bottom tiers, total 12 (6) Production volume of Fe-B-Si-C molten metal and slag discharge amount (A) Uniform flux supply method (comparative example) 430Kg/hr (Component B = 3.0%, Si = 2.8%, C =
3.0%, Fe=Bal) Slag discharge amount: 434Kg/hr (B) Flux divided supply method (method of the present invention) 450Kg/hr (Component B=5.1%, Si=2.1%, C=
2.8%, Fe=Bal) Slag discharge amount: 351Kg/hr (7) Reduction rate of B Contained in colemanite supply amount of 170Kg/hr
The B ₂ O ₃ content is 45.5% and the amount of B is 24.0 Kg/hr.

(A) Amount transferred to molten metal in Comparative Example B: 12.9Kg/hr Amount of unreduced B: 24.0−12.9=11.1Kg/hr Reduction rate of B: 53.8% (B) Transfer amount to molten metal in Method B of the present invention Transfer amount: 22.95Kg/hr Unreduced B amount: 24.0−22.95=1.05Kg/hr B reduction rate: 95.6% As described above, when flux is injected into the melting reduction furnace from the multi-stage tuyeres, The smelting reduction furnace is operated by injecting flux suitable for smelting reduction in the packed bed from the tuyere, and by injecting flux from the lowest tuyere to adjust the final slag to satisfy the conditions required for slag removal. It has become clear that this method not only reduces the total amount of flux injected and lowers the energy cost of producing molten metal, but also increases the reduction rate.

[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... Rigid melting reduction furnace, 2... Raw material supply device,
3,4,5...Tuyere, 6...Preliminary reduction furnace, 7...
Ore/flux supply device, 8...Preliminary reduced ore/
Flux discharge port, 9... Flux hopper for final slag component adjustment, 10... Molten metal/slag discharge port, 11... Hot blast furnace.

Claims (1)

[Scope of Claims] 1. In operation of a vertical smelting reduction furnace in which powdered ore is blown into a bed filled with a solid reducing agent together with hot air to melt and reduce the blown ore, basicity for promoting reduction is added together with the powdered ore from the upper tuyere. A method for operating a smelting reduction furnace characterized by injecting flux and injecting acidic flux for smooth removal of slag from the lowest tuyere.