Specialized metallurgical processes – compositions for use therei – Processes – Electrothermic processes
Patent
1984-10-24
1986-05-27
Andrews, Melvyn J.
Specialized metallurgical processes, compositions for use therei
Processes
Electrothermic processes
C21B 1314
Patent
active
045913811
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process of producing iron. The invention, more precisely, refers to a process of iron production using a reactor, into which the reactants are injected beneath the surface of a molten bath.
A reactor for gas production where pig iron production occurs is known from Canadian Pat. No. 1,097,078.
The Canadian patent discloses a process which produces a gas mixture of substantially carbon monoxide (CO) and hydrogen gas (H.sub.2) from coal containing a certain amount of water. This is carried out according to the patent, by injecting carbon into a molten bath in a stoichiometric excess relative to the oxygen injected in the form of iron oxides into the molten bath, and, simultaneously, oxygen gas is injected in order to oxidize the excess carbon. Thus, the object of process is to produce gas, but a considerable amount of pig iron is also produced by this process.
In SE-PS No. 8103201-3 also a process of coal gasification using a reactor is described. According to this patent, carbon, oxygen gas and iron oxides are injected, with the iron oxides serving as a coolant. Carbon is injected in a stoichiometric excess relative to oxygen in the form of oxides in the bath. The invention according to the patent comprises the step of pressurizing the reactor, whereby a substantially greater amount of gas can be generated, because a greater amount of carbon and oxygen gas can be injected in relation to the bath size than under atmospheric pressure. The object of this patent is a high gas production, and the pig iron formed in this case is to be regarded as a byproduct.
The patents referred to above, thus, relate to processes of gas production where highest possible gas production is the objective. The additional production of pig iron is carried out by a continuous renewal of the molten bath in order to prevent the bath from being too heavily contaminated by impurities introduced with the coal.
The present invention relates to a pig iron production process where the maximum utilization of the energy content of the coal is obtained. Maximum energy utilization of coal implies that only carbon dioxide (CO.sub.2) leaves the process and at the same time a minimum quantity of coal is supplied to the process. The present invention, more precisely, relates to a process where pre-reduction as well as final reduction are integrated in a process and the energy content of the coal supplied is utilized at maximum. The present invention, thus, refers to a process of producing pig iron from iron ore concentrate, in which ore concentrate, coal, oxygen gas and slag formers are injected into a reactor vessel beneath the surface of a molten bath in the reactor. The invention is characterized in that the ratio CO.sub.2 /CO in the waste gas is increased to a value higher than corresponding to the condition of equilibrium at atmospheric pressure, whereby increased heat is generated in the bath for a specific coal amount, than the amount of injected coal in relation to ore concentrate is predetermined to be sufficient for a final reduction of pre-reduced ore concentrate in the reactor, and that CO and H.sub.2 in the exhaust gas are directed to a pre-reduction step, in which unreduced ore concentrate is pre-reduced and thereafter injected into the reactor. In a pre-reduction step ore concentrate is reduced to a degree, which is optimum for the final reduction in a reactor.
By completely reducing ore concentrate by means of melt reduction in a reactor while supplying coal, CO is formed and will be found in the waste gas from the reactor. The exhaust gas is cleaned from CO.sub.2 by washing whereafter remaining CO is used to pre-reduce unreduced ore concentrate, in which the CO is oxidized to CO.sub.2. According to the process, therefore, coal is supplied to the reactor only in an amount sufficient for the final reduction of the pre-reduced ore concentrate in the reactor. Such an amount of coal is sufficient so that in the waste gas there shall be sufficient CO in order to pre-reduce the unreduced iron ore concentrate in
REFERENCES:
patent: 4045214 (1977-08-01), Wetzel et al.
patent: 4238226 (1980-12-01), Sanzenbacher et al.
patent: 4434003 (1984-02-01), Geskin
Axelsson Carl-Lennart
Torssell Krister
Andrews Melvyn J.
IPS Interproject Service AB
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