US 5,542,963 AGranted

Direct iron and steelmaking

OwnerWilliam L. Sherwoodinventor

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Abstract

The process of the invention comprises gaseous reduction of iron oxides in solid state combined with concurrent melting of the hot reduced iron within a closed system without cooling down the charge or exposing it to the outside atmosphere. It incorporates the continuous recycling of a major portion of the off-gases from reduction, and fully utilizes the chemical heat contained in the fuel and reductant by substantially complete oxidation to CO.sub.2 and H.sub.2 O in the system gaseous reaction products and recovery of their sensible heat, prior to final exhaustion as waste gases. Features include dewatering of the off-gas from reduction, enriching with hydrocarbon and recycling a major portion, and separately combusting a minor portion for transfer of the sensible heat to the enriched major portion, and also usually the combustion of a second minor portion with oxygen as fuel for melting, with the sensible heat of these combustion products also utilized for heating the enriched and recycled portion. The reduction stage is suitably conducted in a gas-solid reaction zone within a shaft furnace, and the melting in a gas-solid-liquid reaction zone within a rotary furnace which also contains a gas-liquid reaction zone adapted for controlling of the liquid iron temperature and composition. Supplemental materials such as iron and steel scrap, alloys and fluxes may be added directly into the rotary furnace, and the product may be discharged either batch-wise or continuously be siphon into an evacuated withdrawal chamber for final alloying and refining prior to casting.

A process for direct iron and steelmaking comprising the following steps, in combination:

a) maintaining a gas-solid reaction zone within a reduction reactor adapted for heating and reduction of a charge of iron oxide materials to obtain metallic iron, by contact with hot process gases containing H.sub.2 and CO;
b) maintaining a gas-solid-liquid reaction zone within a rotary furnace adapted for melting within a partially fused bath by heat transferred from the rotating furnace walls in contact with said bath during furnace rotation;
c) feeding iron oxide materials into said reduction reactor;
d) transferring said solid metallic iron from said gas-solid reaction zone into said gas-solid-liquid reaction zone substantially without cooling or exposure to the outside atmosphere of said iron;
e) supplying heat by introducing fuel and oxidant for combustion to form hot gaseous combustion products comprising CO.sub.2 and H.sub.2 O within said rotary furnace from which heat is transferred to said walls and said bath, thereby melting said solid metallic iron to form liquid metallic iron in said gas-solid-liquid reaction zone;
f) exhausting top gas containing H.sub.2 O and CO.sub.2 as well as unreacted H.sub.2 and CO from said gas-solid reaction zone;
g) removing a major portion of the H.sub.2 O contained in said top gas;
h) mixing a major portion of said dewatered top gas together with reducing gases to form an enriched gas mixture;
i) exhausting said gaseous combustion products of said fuel and oxidant in step (e) from said rotary furnace and transferring sensible heat contained therein to comprise sensible heat of said enriched gas mixture from step (h);
j) supplying additional heat to said enriched gas mixture sufficient to sustain said heating and reduction of iron oxide materials to yield hot solid metallic iron;
k) recycling said enriched gas mixture into said reduction reactor;
and
l) discharging of said liquid metallic iron and slag from said gas-solid-liquid reaction zone.

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Abstract

Claims23