US 5,186,741 A · Direct reduction process in a rotary hearth furnace

Abstract

The invented pellet reclamation process includes forming green pellets of a mixture of steel furnace dust, a carbonaceous material such as coal, charcoal, lignite, petroleum coke, or coke, and an organic binder. The green pellets are fed over a layer of burnt pellets on a rotary hearth furnace which successively conveys the pellets first through a drying and coking zone in which the pellets are dried and any volatile matter driven out of the carbonaceous material. The pellets then travel through a reduction zone where the pellets are subjected to a higher temperature at which the contained iron oxide is reduced and remains within the pellets and the zinc, lead and cadmium oxides are reduced, volatilized, re-oxidized and carried off as oxides in the waste gases. The reduced pellets (DRI) are ultimately carried into a discharge zone where they are discharged from the rotary hearth furnace. An apparatus for performing the process is also disclosed.

Claims16

Dependent claims

A method of recovering iron from iron-bearing steel mill wastes comprising the steps of:

(a) combining steel mill wastes, having metallic oxides including iron oxides therein, with carbonaceous material and an organic binder to form a mixture;
(b) mixing said mixture with water to form a wetted mixture;
(c) pelletizing said wetted mixture to form green pellets;
(d) charging said green pellets into a rotary hearth furnace;
(e) drying and coking said green pellets for 10 to 15 minutes at a temperature no higher than 900.degree. C. (1652.degree. F.) to form dried pellets;
(f) reducing said dried pellets for 20 to 30 minutes at a temperature no higher than 1150.degree. C. (2102.degree. F.) to form reduced pellets;
and
(g) discharging said reduced pellets from said rotary hearth furnace;
wherein:
the charging step (d) and the discharging step (g) occupy about 10% of the total time the pellets remain within the rotary hearth furnace;
the drying and coking step (e) occupies approximately 25% of the total time the pellets remain within the rotary hearth furnace, and
the reducing step (f) occupies approximately 65% of the total time the pellets remain within the rotary hearth furnace.

9 more elements

Dependencies are inferred from the claim text.

Direct reduction process in a rotary hearth furnace

Life of this patent

Direct reduction process in a rotary hearth furnace

Life of this patent

Abstract

Claims16