Patent ID: 7854786
Filing Date: 2010-12-21
Classification: C21B,Y02P

Abstract:
1. Process for the direct reduction of iron ore performed by means of a plant comprising a gravitational furnace having at least one iron ore reduction zone in the upper part thereof, and at least one carbon deposition zone and one reduced metal product cooling zone in the lower part thereof, iron ore feeding means, means for discharging the reduced metal product, means for feeding a reducing gas mixture into at least one section of a reactor in correspondence with the reduction zone, means for processing exhaust gas and powders comprising the following steps: a) extraction of the exhaust gas from the reactor using extraction means, b) cleaning and cooling of the exhaust gas in a first cleaning system, to eliminate water produced by reduction reactions, c) division of said exhaust gas into first and second streams, d) sending of the first stream as fuel gas to burners in heating means, e) recirculation of the second stream to improve the ratio (η) between reducing gas and oxidizing gas contained therein, comprising the steps of f) processing the second stream in a recirculation compressor, g) dividing the second stream into third and fourth recirculating gas streams, and h) removing CO i) mixing said third and fourth streams in said mixing means with a synthesis gas stream supplied by an external source in order to re-integrate the amount of reducing gas needed to reduce the iron ore, to form a reducing gas mixture, j) heating of the reducing gas mixture in the heating means to a temperature of between 800° C. and 950° C., k) feeding of the reducing gas mixture leaving the heating means into the reduction zone of the reactor, through feeding means, characterized in that l) at stage i) at least a portion of the synthesis gas stream supplied by the external source is made to pass through a processing device to separate pure methane from the synthesis gas, forming a fifth stream of pure methane and a sixth stream of reducing gas, comprising the CO and H m) said sixth stream is mixed with said reducing gas mixture by means of said mixing means, n) a portion of said fifth stream of pure methane is fed into the carbon deposition zone, a portion into the cooling zone, a portion into the feeding means leading into the reduction zone and a portion into the burners of the heating means.