the improvement of the process carbotermico for producing sponge iron and process carbotermico so perfected

摘要

Carbothermic process for reducing iron ore in an externally heated vertical retort characterized in that the charging mixture is pre-heated while descent within a first zone of the retort and with a substantially constant thermal charge; a second and progressive heating following the pre-heating in a second zone of the retort to initiate the carbothermic reaction and the first reduction phase of the charged mixture; the speed of descent within the second zone being progressively slower and the thermal charge being substantially constant; and a third and constant heating following the second and progressive heating in a third zone of the retort so as to complete the reduction process; the speed of descent within the third zone being substantially the same as the speed of descent in the second zone, the thermal charge being substantially constant, and maintaining the outside temperature of the second and third zones substantially constant in at least a part of the second zone and in all of the third zone, while maintaining the outside temperature of the retort at the second zone higher than the outside temperature of the retort at the third zone. Sponge iron and excess coal are withdrawn from a cooling zone of the retort after it has been cooled below the air oxidation temperature of the sponge iron, the withdrawal rate being controlled in order that the momentary speed of descent of the mixture within the retort is constant at every point in any one single horizontal section of the retort.