Gas: heating and illuminating – Generators – Retort
Patent
1997-04-11
1998-12-08
McMahon, Timothy
Gas: heating and illuminating
Generators
Retort
48197R, 75492, C10J 320
Patent
active
058462686
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process and a plant for producing liquid pig iron or liquid steel preproducts and sponge iron from charging substances comprised of iron ore, preferably in lumps and/or pellets, and optionally fluxes. The charging substances in a first reduction zone are directly reduced to sponge. The sponge iron in a meltdown gasifying zone is melted under the supply of carbon carriers and an oxygen-containing gas. A reducing gas containing CO and H.sub.2 is produced, which is introduced into the first reduction zone, is reacted there and is drawn off as an export gas. The drawn-off export gas is subjected to CO.sub.2 elimination as well as heating and, as a reducing gas at least largely free of CO.sub.2 is fed to at least one further reduction zone for the direct reduction of further iron ore, After the reaction with the iron ore, the gas is drawn off as an export gas.
2. Description of the Related Art
A process of this type is known, for instance, from DE-C 40 37 977. In that known process, export gas drawn off the further reduction zone is subjected to scrubbing and subsequently is subjected to CO.sub.2 elimination as well as heating together with the export gas derived from the first reduction zone. This mixed gas is then fed to the further reduction process as a reducing gas. Thereby it is feasible to utilize a portion of the reductants still present in the export gas derived from the further reduction zone, since that export gas is fed to the further reduction process as a recycle reducing gas.
The reducing gas fed to the further reduction process in that known process at first is subjected to preheating in a heat exchanger and subsequently is heated to the temperature required for the direct reduction in a second heating stage, the further heating being accomplished by a partial combustion of the reducing gas.
However, such a partial combustion causes deterioration of the quality of the reducing gas, because reductants are consumed and the CO.sub.2 and/or H.sub.2 O contents are increased. The increase in the CO.sub.2 content to a value that is too high may be compensated for by the reducing gas having only very slight contents of CO.sub.2 and H.sub.2 O prior to heating. Yet, this involves the disadvantage that, due to a strict specification with a view to the residual content of CO.sub.2, reductants are discharged along with the offgas leaving the CO.sub.2 elimination plant.
SUMMARY OF THE INVENTION
The invention aims at avoiding these drawbacks and difficulties and has as its object to provide a process, as well as a plant for carrying out the process, which enable the utilization as complete as possible of the energy of the export gas derived from the further reduction process, in particular by saving its reductants. In addition, minimization of the energy to be externally fed into the further reduction process is to be reached. Moreover, the CO.sub.2 elimination plant is to be operable in an efficient manner, i.e., with a loss of reductants as slight as possible, while nevertheless ensuring sufficiently low CO.sub.2 and H.sub.2 O contents in the reducing gas fed to the further reduction zone.
In a process of the initially defined kind, this object is achieved in that heat of the export gas leaving the further reduction zone is used for heating the export gas derived from the first reduction zone.
It is a particular object of the invention to use a minimum portion of export gas, derived from the further reduction process, for heating the reducing gas fed to the further reduction zone, such that this export gas will be available to the further reduction process as a recycle reducing gas in an amount as large as possible.
This object is achieved in that, for heating, sensible heat is recuperatively withdrawn from the export gas drawn off the further reduction zone in the hot unscrubbed state, and by means of a heat carrier, is transmitted to the export gas derived from the first reduction zone, the heat carrier advantageously bein
REFERENCES:
D. Siuka, et al., "Corex Leads Smelting Reduction Race", Steel Times International, vol. 18, No. 2, Mar. 1994, pp. 12-13.
Diehl Jorg
Rosenfellner Gerald
McMahon Timothy
Voest-Alpine Industieanlagenbau GmbH
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