Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Patent
1991-06-20
1993-03-30
Rosenberg, Peter D.
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
75 1053, C21B 1306
Patent
active
051980193
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to the reduction of iron oxides and is particularly concerned with a process and apparatus for supplying pre-reduced iron oxide to a smelting vessel for the production of iron or steel.
BACKGROUND
Ferrous bath-smelting processes with direct injection of ore and reducing agents are attractive from a commercial point of view. This arises from the fact that ore fines can be fed directly, obviating the need for lump feed as required by the blast furnace. Further, steaming coal can be used as reducing agent without prior removal of volatile matter in coke ovens.
Reducing agent (usually coal) consumption on such a system can be excessive, however, and the key to efficient operation of the smelting vessel is post-combustion of smelter offgas. In one embodiment of this concept, an oxygen-containing gas is admitted into the space above the bath and some of the carbon monoxide and hydrogen present is oxidised to carbon dioxide and water. The heat thus liberated is transferred back to the bath, and this reduces the amount of reducing agent needed in the process. Such a system is described in Australian patent specification No. 74409/81 the contents of which are incorporated herein by reference.
The smelter offgas from such a process contains appreciable amounts of carbon monoxide and hydrogen, and leaves the main vessel at relatively high temperature (eg. 1600.degree. C.). To further reduce the amount of reductant consumed in the overall process, it is beneficial to pre-reduce incoming iron ore feed with this offgas prior to admitting it to the smelting vessel. One such proposal is described in Australian patent specification No. 28044/84, in which the pre-reduction occurs in a shaft furnace.
Stickiness of particles under pre-reduction conditions is a potential problem. At temperatures above about 1000.degree. C., particles begin to cling to surfaces and thus create serious difficulties in plant operation. To avoid this, it is necessary to arrange the process in such a way as to maintain pre-reduction temperatures in the range 800-1000.degree. C. At temperatures much below 800.degree. C., pre-reduction rates slow appreciably and excessive residence-times are needed.
The proposal in the aforementioned AU-28044/84 aims to avoid this difficulty by cooling the offgas in a preconditioning chamber in which the offgas is additionally reduced by an intensive mixing action between the gas and coal dust caused by a special grid or lattice-lining over which the gas is passed. A cyclone is then required to separate the coal dust from the reduced, cooled offgas, prior to passing the gas to a shaft furnace to reduce the iron ore. However, it would be anticipated that a buildup of the sticky particles would occur on the special grid or lattice-lining and other surfaces of the preconditioning chamber.
Australian patent specification No. 69827/87 proposes an alternative arrangement in which fine ore having a particle size up to a maximum of 0.1 mm is introduced directly into the hot reducing gas immediately downstream of the offgas outlet from the smelting vessel.
It is an object of the present invention to alleviate the disadvantages of the aforementioned proposals and particularly to facilitate the partial reduction of particulate iron oxide containing material in the smelter offgas in an improved range of particle sizes.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention there is provided a process for supplying pre-reduced iron oxides to a smelting vessel which comprises directing a hot reducing offgas from the vessel into a vertical riser duct without substantial cooling of the offgas and conducting the reducing offgas upwardly through the riser duct, entraining particulate iron oxide containing material in the hot reducing offgas in the riser duct thereby cooling the offgas and simultaneously partially reducing the material as it is conveyed by the offgas through the riser duct, separating the partially reduced material from the offgas and introduci
REFERENCES:
patent: 2805929 (1957-09-01), Udy
patent: 3235374 (1966-02-01), Mahony
patent: 4073642 (1978-02-01), Collin et al.
patent: 4094665 (1978-06-01), Collin et al.
patent: 4359212 (1982-11-01), Bengtsson et al.
"FluxFlow Process Gas Cleaning and Heat Recovery System" A. Ahlstrom Corp., Finland.
Dry Rodney J.
La Nauze Robert
CRA Services Limited
Rosenberg Peter D.
LandOfFree
Manufacture of iron and steel in a duplex smelter and solid stat does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Manufacture of iron and steel in a duplex smelter and solid stat, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Manufacture of iron and steel in a duplex smelter and solid stat will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1278396