2-stage fluidized bed furnace for pre-reducing fine iron ore and

Details 2-stage fluidized bed furnace for pre-reducing fine iron ore and 2-stage fluidized bed furnace for pre-reducing fine iron ore and

1997-08-25

1999-07-06

Kastler, Scott

Specialized metallurgical processes, compositions for use therei

Processes

Producing or treating free metal

266172, C21B 1314

Patent

active

059192810

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a pre-reduction furnace for pre-reducing fine iron ore having a wide particle size distribution in a smelting reduction process for producing molten pig iron directly from iron ore and coal, without the need for sintering machines and coke ovens. More particularly, the present invention relates to a 2-stage fluidized bed furnace for pre-reducing fine iron ore which includes a high content of fine particle size ore which is readily decomposed by reaction heat at a pre-reduction temperature and a method for pre-reducing fine iron ore using the pre-reduction furnace.
2. Description of the Prior Art
Generally, methods of reducing iron ore to produce a molten iron include a blast furnace, a direct reduction process by which reduced iron is obtained in a solid form by using a shaft furnace, a rotary kiln and a fluidized bed furnace, as well as other methods using an electric furnace.
The blast furnace is the prevailing iron-making method at the present time. The blast furnace is charged with sintered ore, including fine iron ore, and large amounts of coke, using high quality coking coal as a heat source and as a reducing agent, so as to improve the permeability and reducibility of the iron ore at the shaft portion of the blast furnace.
The blast furnace iron making process has serious drawbacks, such as the immense facility investment, the lack in flexibility of operation due to high tonnage mass production, and the industrial pollution of the environment from the pre-treatment facilities. These problems are caused by the coke ovens required for distilling the coking coal and the facilities needed for manufacturing the sintered iron ore.
A direct reduction process by which iron is obtained by using a high-quality iron ore and a reducing gas from a nature gas has been limitedly employed in geographical areas that can be economically supplied with high quality iron ore and natural gas.
The quantity of crude steel production in the world is relatively low. However, the production of crude steel is gradually increasing, caused by the increasing demand for various kinds of structural steels, as well as by the deterioration in the quality of available scrap.
However, the above method is used through pre-treatments such as pelletizing and sintering to increase permeability when iron ore is charged in a furnace. This is very important in attaining a normal operation. In the case of a smelting reduction process which makes molten iron by directly using fine iron ore of the type having largely varying grain sizes without pre-treatment using coal, the above method has importance as a new method of producing iron capable of replacing a blast furnace. The smelting reduction method has been studied as a means for charging conventional iron ore in a simple reactor and reducing it after directly melting it. Recently, however, a smelting reduction process has been developed for charging iron ore in a melting furnace after pre-reducing a proper quantity in a solid state and finally reducing it. This approach is practical and energy efficient.
It is of interest to develop a technique employing a fluidized bed pre-reduction furnace which fluidizes fine iron ore by using an off-gas from a smelting reduction furnace supplied to the fluidized bed reduction furnace, which is known as a method of processing fine iron ores for pre-reduction of this process.
In a conventional fluidized bed direct reduction process related to such techniques, it is practical to use special fine particle size iron ore in which the particle size distribution is narrow. A fluidized bed reduction process using fine iron ores having a wide distribution of particle size (i.e., pre-reduction step of a smelting reduction process producing molten iron using coal as a heat source and as a reducing agent and iron ores without pre-treatment) has recently been developed but is not yet practical because of technical difficulties encountered. In a known smelting reduction process prod

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