Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Patent
1998-10-05
2000-10-24
Andrews, Melvyn
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
75451, 266172, C21B 1100
Patent
active
061360651
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention pertains to a process for the direct reduction of ore dusts or fines with a broad particle size spectrum by means of hydrogen in a horizontal fluidized bed chute. The present invention also pertains to a device for carrying out this process.
BACKGROUND OF THE INVENTION
A horizontal reactor with internal oncoming flow bottoms with all the devices necessary for the operation of such a reactor has been known from DE 43 26 562 C2.
The horizontal fluidized bed reactor according to DE 43 26 562 C2 has a drawback, namely, that it can operate only with a predetermined particle size spectrum, which is determined by the oncoming flow velocity (fluidization velocity) in the fluidized bed. Thus, a different particle size spectrum requires different oncoming flow velocities. In addition, screen classification is necessary before charging the material onto the fluidized-bed reactor.
SUMMARY AND OBJECTS OF THE INVENTION
The object of the present invention is to improve the process claimed in the abovementioned document such as to make it possible to optimally reduce the broadest possible particle size spectrum of ore dust or fines in a horizontal fluidized-bed chute. Another object of the present invention is to design a prior-art fluidized-bed chute such that the intended process can be carried out. Another object of the present invention is to guarantee an optimal mode of operation of the reduction plant in terms of heat economy.
Reference may be made to parts of the specification documents of DE 43 26 562 C2 in the description of the device. DE 43 26 562 C2 corresponds to U.S. Pat. No. 5,545,251 which is hereby incorporated by reference.
The present invention is based on the use of the basic concept of the reactor described in DE 43 26 562 C2 and U.S. Pat. No. 5,545,251.
According to the process of the present invention and of the device, it is possible to process ore dusts with a particle size spectrum ranging from less than 6.3 mm to 0.02 mm. Particle sizes ranging from less than 3.0 mm to 0.02 mm are preferably selected.
Ore dusts stored in buffer tanks are charged into pressure vessels arranged under them. These pressure vessels are used as pressure sluices for introducing the ore dust into a preheater. This preheater, e.g., a fluidized-bed reactor or a spouted-bed reactor, as well as the adjoining horizontal fluidized-bed chute, are under vacuum.
One pressure vessel each is loaded from a buffer tank under atmospheric pressure, while the other pressure vessel is unloaded into the preheater.
The preheater is used to preheat the ore dust using the so-called top gas from the horizontal fluidized-bed chute, the reduction reactor proper.
The oncoming flow velocity in the preheater is selected to be such that ore dust with a particle size ranging from less than about 0.5 mm is very extensively removed from the preheater. This ore dust is separated via a hot gas cyclone and is fed, together with the preheater ore dust from the preheater, into the first chamber of the horizontal fluidized-bed chute, i.e., the reduction reactor proper.
The unloading of the preheater arranged upstream of the horizontal fluidized-bed chute, namely, the unloading of the particle fractions ranging from, e.g., less than about 3 mm to about 0.5 mm, takes place in an uncontrolled manner via a solids line, via which the ore dust is charged into the first chamber of the horizontal reduction reactor. This chamber is provided with a heat exchanger, by which the ore dust can be heated to a desired temperature of the fluidized bed. The fluidized bed temperature shall preferably be in the range of about 680.degree. C. to 700.degree. C. The oncoming flow medium and the reducing medium is preferably hydrogen, which had been previously heated to about 710.degree. C. in a reducing gas heater. The oncoming flow velocity is selected to be such that essentially no ore dust can be discharged any more.
It is especially advantageous according to the present invention to use reducing gas heated to a high temperat
REFERENCES:
patent: 4978387 (1990-12-01), Kepplinger
patent: 5382277 (1995-01-01), Rose
patent: 5545251 (1996-08-01), Knop
patent: 5560762 (1996-10-01), Bresser et al.
Heinrich Peter
Knop Klaus
Andrews Melvyn
Ferrostaal Aktiengesellschaft
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