Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Patent
1998-01-20
1999-01-12
Kastler, Scott
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
266160, 266171, B03C 1015, C01B 3130
Patent
active
058580603
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a process for the purification of iron carbide. Iron carbide Fe.sub.3 C is produced industrially by reaction, in an industrial furnace generally consisting of a fluidized-bed reactor, of a mixture of iron oxides in a reducing atmosphere which is rich in hydrogen and methane. The Fe.sub.3 C obtained at the outlet of the reactor is not pure: it contains, of course, a large quantity of Fe.sub.3 C, of the order of 90 to 95%, and also Fe, 0.5 to 1.5%, iron oxides, essentially magnetite Fe.sub.3 O.sub.4, 2 to 5%, as well as gangue, for example SiO.sub.2 whose nature varies depending on the origin, is used as ore. This mixture based on iron carbide Fe.sub.3 C is used as the supply of metal in an electrical steelworks furnace.
BRIEF DESCRIPTION OF THE INVENTION
The invention relates more particularly to a process making it possible to purify iron carbide, in particular to separate the impurities present with the iron carbide Fe.sub.3 C.
To this end, the ferromagnetic properties of the various components are employed. It is known, from U.S. Pat. No. 4,396,423, a proces for the recovery of iron carbide and zinc from a gangue of ore, after a carbiding step and before separation of zinc from iron carbide. Thus, it is known that iron carbide Fe.sub.3 C is ferromagnetic at ambient temperature and that this property disappears above a certain temperature, called the Curie temperature. In particular, as regards Fe.sub.3 C and depending on its characteristics, this Curie temperature varies from 180.degree. C. to 230.degree. C.
This same property is also valid for the compounds mixed with the Fe.sub.3 C, 768.degree. C. for Fe and 575.degree. C. for Fe.sub.3 O.sub.4. These values are indicative and may vary depending on the chemical purity of the samples.
The object of the present invention is to make it possible to exploit this property in the various withdrawal zones of a fluidized-bed reactor for manufacturing iron carbide, by proposing separation steps at different temperatures which are chosen as a function of the Curie temperatures of the various components mixed with the iron carbide, in order to obtain a purification of the iron carbide at the end of this succession of separation steps.
To this end, the process for the purification of iron carbide, is characterized in that: reaction chamber, being used for heating the products in the recycling phase, in an atmosphere of composition suitable for not destroying the iron carbide, passes through a first magnetic field, thus making it possible to separate it into a magnetic fraction (iron and oxides) and a non-magnetic fraction (iron carbide and gangue), temperature below the Curie temperature of iron carbide, magnetic field, thus making it possible to separate it into a magnetic fraction (iron carbide) and a non-magnetic fraction (gangue).
Other characteristics and advantages of the present invention will emerge from the following description, given with reference to the appended drawings which illustrate an entirely non-limiting illustrative embodiment thereof. In the figures:
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a schematic diagram illustrating the process of magnetically sorting a mixture;
FIG. 2 is a schematic view illustrating the process of magnetically sorting a mixture containing iron carbide;
FIG. 3 illustrates the application of the magnetic separation process to a fluidized-bed reactor;
FIG. 4 illustrates the application of the magnetic separation process to a circulating fluidized-bed reactor.
DETAILED DESCRIPTION OF THE INVENTION
According to a preferred embodiment of a plant for implementing the process forming the subject-matter of the invention, it mainly includes at least one magnetic separator 1, 2, advantageously arranged at the outlet of the withdrawal zones of a fluidized-bed reactor 3.
In an application to the manufacture of iron carbide, a fluidized-bed reactor 3, containing a charge of iron ore fines reacting within a reducing atmosphere, in particular rich in hydrogen and in methane
REFERENCES:
patent: 3936372 (1976-02-01), Frangiskos
patent: 4396423 (1983-08-01), Stephens, Jr. et al.
patent: 4398945 (1983-08-01), Stephens, Jr.
Kastler Scott
TH Engineering France S.A.
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