Patent ID: 7964014
Filing Date: 2011-06-21
Classification: C21B,C22B,F27B,F27D,Y02P

Abstract:
1. A method of reduction of metal oxide-bearing green pellets for a reducing furnace characterized by charging (i) iron oxide-bearing green pellets for a reducing furnace obtained by shaping a feed powder containing a metal oxide-bearing powder and 5 to 30 wt % of a carbon-bearing powder, wherein, when shaping the green pellets, three or more types of feed powder, including at least two types of iron containing feed powder, are placed in separate storage bins, a mixing ratio of a mixture of feed powders is determined so that the mixture of said feed powder includes 20 to 80 wt % of powder particles of not more than 10 μm size and said feed powders are fed out from said bins, and the mixture of said feed powders is shaped into green pellets having a porosity of not more than 0.32 using a pan type pelletizer and then the green pellets are dried in a dryer at a temperature of not higher than 250° C., or (ii) iron oxide-bearing green pellets for a reducing furnace produced by a method characterized by pelletizing a feed powder containing a metal oxide-bearing powder and a carbon-bearing powder, wherein, when producing the green pellets, three or more types of feed powder, including at least two types of iron containing feed powder, are placed in separate storage bins, a mixing ratio of a mixture of feed powders is determined so that the mixture of said feed powder includes 20 to 80 wt % of powder particles of not more than 10 μm size and said feed powders are fed out from said bins, and the mixture of said feed powders is pelletized into green pellets having a porosity of not more than 0.32 using a pan type pelletizer and then the green pellets are dried in a dryer at a temperature of not higher than 250° C. into a zone of a rotary hearth reducing furnace having a furnace ambient temperature of 900 to 1200° C. and reducing them by firing at a temperature of not less than 1200° C. for not less than 5 minutes.