JPH0313291B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for melting and reducing metal oxides. In recent years, there has been a tendency for ore resources containing metal oxides to be less in the form of lumps and more in the form of powder. Such granular ores are often agglomerated and then smelted in a melting furnace in the same way as ordinary lump ores. As these melting furnaces, electric furnaces, converters, or other melting furnaces are used. Furthermore, the agglomerated ore may be pre-reduced and then melted and reduced in the various melting furnaces described above to reduce power consumption and energy costs. However, using a converter or other melting furnace other than an electric furnace to melt and reduce ores that are difficult to melt and hard to reduce, such as pre-reduced ores of chromite, has the drawback that the operation is extremely difficult. The method of pre-reducing agglomerate ore and then melting and reducing it in an electric furnace is the most stable production method.
Conventionally, ferrochrome has been produced by making chromium powder ore into pellets, pre-reducing the pellets in a rotary kiln, and then melting and reducing the pre-reduced pellets in a submerged arc electric furnace. However, processing costs to agglomerate powdery ore are large, and even if the agglomerated ore is pre-reduced, the electric energy required to melt and reduce it in an electric furnace is still large, and The disadvantage was that economic efficiency was put under pressure due to chemical treatment costs and power consumption costs. The inventors of the present invention aimed to reduce manufacturing costs, and in particular to eliminate the use of electrical energy.
As a method for producing various molten metals by directly using powdered ore, he invented a smelting reduction method that uses a preliminary reduction furnace and a smelting reduction furnace in which a carbon-based solid reducing agent packed bed was formed, and he filed a patent application in 1983- A patent application was previously filed under No. 63294. The method uses a preliminary reduction furnace and a smelting reduction furnace, and after blowing exhaust gas from the smelting reduction furnace into the preliminary reduction furnace to preliminary reduce the granular ore,
Pre-reduced ore is supplied from at least the upper tuyere of the plurality of tuyeres provided in two upper and lower stages in the lower part of the smelting reduction furnace, and the solid reducing agent and tuyere of the packed bed formed in the smelting reduction furnace are supplied. In this method, the molten metal accumulated in the hearth is melted and reduced by hot air and/or oxygen-enriched air blown from the furnace, and the molten metal accumulated in the hearth is discharged together with the slag in a timely manner. By the way, according to experiments in a test furnace implementing the above method, when pre-reduced ore and flux are injected from the upper tuyere, the pre-reduced ore melts together with the flux in the high temperature region formed near the tip of the tuyere. When the packed bed formed by the solid reducing agent is dropped, the melting reduction is promoted, and the molten metal and slag are accumulated in the hearth as separation of the metal and slag progresses. At this time, for example, when smelting chrome ore, Si in the composition of the molten metal is 4 to 9.
%, S is 0.1~0.5%, P is 0.1~0.4%, C is 3~
7%, the remainder being essentially the main component, the metallic element Cr;
It is Fe, and in order to adjust the content of Si or other elements in the molten metal to a predetermined amount, it is necessary to re-smelt it in another furnace after discharging it from the smelting reduction furnace. Furthermore, under conditions where the operation becomes unstable due to various factors and the heat supply is insufficient or the smelting reaction leading to the hearth is insufficient, it is necessary to smelt, for example, chromium ore into the discharged molten slag. in case of,
Cr and Fe increase in the unreduced oxide state, and the fluidity of the molten metal and molten slag decreases, making it difficult to discharge these molten materials.
Once the molten material reaches the hearth with insufficient smelting or heat, there are limits to the measures that can be taken, such as increasing the temperature of the blast.
It was not possible to obtain sufficient effect. The present invention aims to provide a method for melting and reducing metal oxides that can eliminate and improve the drawbacks of the invention previously filed by the present inventors, and the scope of the claims is as follows: The above object can be achieved by providing a method. That is, the present invention introduces high-temperature exhaust gas discharged from a vertical smelting reduction furnace having a packed bed formed of a carbon-based solid reducing agent into a pre-reduction furnace, and charges granular ore into the pre-reduction furnace. A smelting reduction method for granular metal oxide ore by blowing pre-reduced ore obtained by fluidized pre-reduction through the tuyere of the smelting reduction furnace, in which a plurality of blowing devices are provided in the hearth part. Various refining agents in at least one state of solid, gas, or liquid are passed through the blowing device into at least one of the molten metal bath and the molten slag bath stored in the hearth sump. Alternatively, a heating agent may be directly injected to promote various refining reactions and/or temperature raising reactions in the hearth, while adjusting the composition and temperature of the molten metal and molten slag, and then discharging the molten metal and molten slag from the smelting reduction furnace. The present invention relates to a characteristic method for melting and reducing metal oxide ores. Next, one embodiment of the present invention will be described with reference to the drawings. The melting reduction furnace 1 is a vertical furnace, and a packed bed made of a carbon-based solid reducing agent is formed in the furnace, and the reducing agent is normally supplied to the furnace through a reducing agent supply port 2 provided at the top of the furnace. supplied within. High-temperature reducing exhaust gas generated in the smelting reduction furnace 1 is supplied from the exhaust port 3 to the preliminary reduction furnace 4 via the supply port 5 provided at the lower part of the preliminary reduction furnace 4, and in the same furnace 4, powdered ore is produced. The function is to preliminarily reduce the amount by fluid reduction. At this time, flux is also supplied into the furnace 4 if necessary. The pre-reduced ore and flux discharged from the pre-reduction discharge port 6 provided in the pre-reduction furnace 4 are transported into the melting reduction furnace 1 through a plurality of tuyeres 7 provided in two upper and lower stages, respectively. Blown with hot air and/or oxygen-enriched air.
The ore and flux injected from the tuyere 7 melt in the high temperature area near the tip of the tuyere in the furnace, and are further melted and reduced as they drip, forming molten slag and molten metal as they accumulate in the hearth. Separates into two phases. In the hearth below the tuyere level, a plurality of hearth blowing pipes 8 are provided diagonally penetrating the hearth shell so that their tips are immersed in the molten material stored in the hearth. Various refining agents and temperature increasing agents in at least one state selected from solid, gas, and liquid are blown into the molten metal bath 9 and/or slag bath 10 through the blowing pipe 8. At this time, the position of the tip of the blowing tube can be moved as appropriate. The molten metal and slag whose composition has been adjusted in this way are poured out from the taphole 11. Next, reaction formulas (1) to (4) are shown for several examples of refining reactions using gaseous and solid refining agents. [Si] + O ₂ = SiO ₂ ... (1) [S] + CaC ₂ = (CaS) + 2C ... (2) (Cr ₂ O ₃ ) + 3C = 2 [Cr] + 3CO ... (3) (FeO) + C =[Fe]+CO...(4) By the way, liquid refining agents include molten metals based on alloys of various metal elements, and these liquids can also be injected into the furnace by injecting them through the hearth injection pipe 8. The composition of the molten metal stored in the bed can be adjusted. Note that as the temperature increasing agent, a thermite agent such as an aluminum type can be used. According to experimental results using the various refining agents and temperature raising agents mentioned above, either singly or in combination, the composition and fluidity of molten metal and/or slag can be easily controlled by the refining reaction and temperature raising reaction in the hearth. It turns out that it can be done. Next, an example in which the present invention was carried out using a test furnace will be described. Example (1) Raw material: Pre-reduced chromium ore, supply amount 360
Kg/h Preliminary reduction rate 35% Particle size distribution 50-100mesh (80%) (2) Flux: Supply amount 180Kg/h Silica stone, lime (3) Type of carbon-based solid reducing agent: Coke, supply amount
600Kg/h Particle size distribution 15~30mm (4) Amount of air blown to the vertical furnace: 1250Nm ³ /h Air temperature 800~900℃ Air tuyeres 4 each on the upper and lower sides, 8 in total (pre-reduced chromium ore and flux are placed in the upper 4) (5) Molten metal production: 245Kg/h (6) Molten slag discharge: 340Kg/h (7) Experimental results

[Table] As can be seen from the examples above, according to the present invention,
By injecting a refining agent or a temperature raising agent into the molten material stored in the hearth, it is possible to adjust the composition of the molten metal and molten slag in the hearth, and also improve the fluidity of the molten material. Since it can be controlled, the trouble of discharging the melted material has been solved. The effects of the present invention can be summarized as follows. By injecting the refining agent and temperature raising agent directly into the molten metal or molten slag bath accumulated in the hearth, the refining reaction and temperature raising reaction can be accelerated in the hearth, resulting in the following advantages: There is. (1) The time for refining molten metal outside the furnace is significantly reduced. (2) Production rate increases by improving the reduction rate of metal oxides in slag. (3) Problems with iron tapping and slag due to poor fluidity of the molten material can be resolved.

[Brief explanation of the drawing]

The figure is a system diagram of one example of an embodiment of the present invention. 1... Melting reduction furnace, 2... Reducing agent supply port, 3...
...Exhaust gas discharge port, 4...Preliminary reduction furnace, 5...Gas supply port, 6...Preliminary reduction ore discharge port, 7...Tuyere,
8... Hearth blowing pipe, 9... Molten metal bath, 10...
...molten slag bath, 11...tap hole.

Claims (1)

[Claims] 1. High-temperature exhaust gas discharged from a vertical smelting reduction furnace having a packed bed formed by a carbon-based solid reducing agent is introduced into a pre-reduction furnace, and on the other hand, granular ore is charged into the pre-reduction furnace for fluidized pre-reduction. A hearth of a smelting reduction furnace in which a plurality of blowing devices are provided in the hearth in a method for smelting and reducing powdery metal oxide ore by blowing pre-reduced ore obtained through the tuyeres of the smelting and reducing furnace. Various refining agents or temperature increasing agents in at least one of solid, gas, and liquid states are passed through the blowing device into at least one of the molten metal bath and molten slag bath distilled in the sump. A metal oxidation method characterized by directly injecting molten metal and molten slag to promote various refining reactions and/or temperature raising reactions in the hearth, adjusting the composition of the molten metal and molten slag, and controlling the temperature, and then discharging from the smelting reduction furnace. Method for melting down ore.