Specialized metallurgical processes – compositions for use therei – Processes – Free metal or alloy reductant contains magnesium
Patent
1997-03-05
1999-03-16
Ryan, Patrick
Specialized metallurgical processes, compositions for use therei
Processes
Free metal or alloy reductant contains magnesium
75611, 75585, 75392, 75414, 75433, C21B 1300
Patent
active
058823778
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a smelting reduction process of chromium ore, and more particularly to a process for directly using a cheap chromium ore instead of an expensive alloying iron to attain stable smelting reduction in a high efficiency.
BACKGROUND ART
Heretofore, the production of stainless steel has been carried out by using ferrochromium obtained through carbon reduction of chromium ore or the like in an electric furnace. However, the production of the ferrochromium was necessary to take a greater amount of electric power and the production cost thereof became high and hence the production cost of the stainless steel became also high.
As a countermeasure for solving the above problem, there has been developed so-called smelting reduction process in which chromium ore or unreduced or semi-reduced pellets of the chromium ore subjected to a preliminary treatment are subjected to carbon reduction in a metallurgical reaction vessel such as a convertor or the like without using electric power to prepare a chromium-containing molten metal (for example, JP-A-58-9959 and JP-A-55-91913).
However, the aforementioned smelting reduction process of chromium ore has still the following problems. Al.sub.2 O.sub.3 and so on), while the gangue ingredient is included in fuel and a carbonaceous material as a reducing agent, so that a greater amount of slag is created during the smelting reduction. efficiency is low, the refractory is considerably lost by a metal oxide ingredient (Cr.sub.2 O.sub.3, FeO) having a high oxidizing property and also the smelting time becomes longer. calculated from carbon balance and heat balance, slag foaming and slopping are caused and hence the operation becomes unstable. in the smelting reduction.
However, when the carbonaceous material is excessively used, the amount of carbon remaining in the slag becomes large after the completion of blowing, which brings about the lowering of the utilization of the carbonaceous material and also badly exerts on the effective use of the slag.
DISCLOSURE OF THE INVENTION
It is an object of the invention to advantageously solve the aforementioned problems and to provide a smelting reduction process of chromium ore in which (1) the increase of the slag amount can be controlled, (2) the reduction reaction efficiency in the chromium ore can be improved to attain the mitigation of refractory erosion, reduction of operating time and stabilization of operation, and (3) it is possible to effectively use the slag at the smelting reduction step, and hence chromium-containing molten metal can cheaply and efficiently be obtained as a base melt of stainless steel.
That is, the essentials and constructions of the invention are as follows. material and a chromium ore into hot metal admitted in a metallurgical reaction vessel such as a converter or the like, feeding an oxygen gas to burn the carbonaceous material and conducting fusion and reduction of the chromium ore through heat of combustion to produce a chromium-containing molten metal, characterized in that a carbon substance having a Hardgrove grindability index (HGI) of not more than 45 and a volatile matter (VM) of not more than 10% is used as the carbonaceous material. carbonaceous material charged in the metallurgical reaction vessel has such a particle size formation that a ratio of particle size larger than a given particle size (dp) calculated from the following equation (1) is not less than 80%: )
W: feed rate of carbonaceous material (kg/min)
Q: rate of generating (CO+CO.sub.2) from an inside of a vessel resulted from the supply of oxygen (Nm.sup.3 /min)
D: opening diameter of a vessel (m). carbonaceous material is charged into the metallurgical reaction vessel in an amount that a total surface area of the carbonaceous material charged is not less than 60 m.sup.2 per 1 ton of slag existing in the vessel. portion of the carbonaceous material having a particle size smaller than the particle size calculated by the equation (1) is agglomerated. the reaction vessel is a converter usin
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Aida Kimiharu
Bessho Nagayasu
Kishimoto Yasuo
Nishikawa Hiroshi
Sudo Fumio
Elve M. Alexandra
Kawasaki Steel Corporation
Miller Austin R.
Ryan Patrick
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