Method for producing pig iron

Abstract

The invention concerns a process for the production of pig iron with the help of blast furnaces or other suitable devices in which iron-containing materials are reduced and melted in the presence of fuels. According to the invention, metallurgical coke can (be replaced) by cheaper organic exchange fuels, with the help of a coupling of a multi-step process for the gasification of the replacement fuels to reduction gas and coke with a blas furnace process to which the products of the gasification process are supplied together or separately at the height of the tuyeres or via these into a heating. The gasification process is also used for the pre-reduction of iron oxides, fine ore and ore concentrate.

1 . Process for the production of pig iron with the help of fossil and secondary fuels, especially of hard or brown coals or other organic fuels, such as refuse and sewage sludge, from iron ores or other iron oxides, which are made available as in nature or worked up, e.g. as sinter, pellets, fine ore or concentrate, in a blast furnace process with external gasification of the fuels, characterised in that 
 in the case of the gasification in the first process step, a part of the fuel is gasified chemically-exothermally with air and/or oxygen with addition of blast furnace gas from the blast furnace process and/or water vapour under a pressure which is higher than the pressure in the blast furnace at the height of the tuyeres and at a temperature between 1000 and 1800° C. to give reduction gas;    in a second gasification process step, further fuel is blown into the hot reduction gas from the first process step, there partly reacts chemically-endothermally with the reduction gas and the mole ratio of the reducing gas components carbon monoxide and hydrogen to those of the oxidising components carbon dioxide and water vapour amounts to at least 3:1 and    the reduction gas from the second gasification step is blown into the blast furnace at the height of the tuyeres with a temperature of 300 to 1000° C.    
     
     
         2 . Process for the production of pig iron according to  claim 1 , characterised in that the temperature gradient in the reduction zones of the blast furnace is regulated by the blowing in with the reductive gas of coke dust obtained from the second process step of the gasification process.  
     
     
         3 . Process for the production of pig iron according to one of claims  1  or  2 , characterised in that coke dust separated from the reduction gas is recycled into the gasification process, whereby, in the gasification process, the supplying with fresh fuel is reduced in favour of the recycled coke dust and, in the case of the recycling into the second process step, for the ensuring of the greatest possible conversion, the coke dust is first supplied to the hot gasification agent from the first process step in its direction of flow for the thermal activation and only thereafter the fresh fuel is supplied to the cooled gasification agent by the blowing in of the coke dust.  
     
     
         4 . Process for the production of pig iron according to one of the preceding claims, characterised in that 
 to the external, preferably powdery fuels, before the blowing into the second process step of the gasification process, are admixed iron oxide dusts, fine ore and/or iron ore concentrate;    this mixture is blown into the second process step, where the iron oxide dusts, the fine ore and/or ore concentrate are partly pre-reduced to iron sponge;    the solid mixture obtained, consisting of residual coke, iron sponge and pre-reduced ore, is passed with the reduction gas from the gasification process into a dust separator;    the solids mixture separated from the reduction gas is blown into the blast furnace process or a melting trough with gasification taking place of the residual coke with air and/or oxygen and further reduction of the fine-grained ore to iron sponge.