Method for the direct reduction of iron ore

Abstract

The invention relates to a process for direct reduction of iron ore to sponge iron, wherein the iron ore passes through a reduction zone for reducing the iron ore to sponge iron. The reduction zone is subdivided into a pre-reduction zone supplied with a first reduction gas and into an end-reduction zone supplied with a second reduction gas. The first reduction gas has a different gas composition compared to the second reduction gas. A first reduction gas has a hydrogen proportion at least 5% by volume higher compared to the second reduction gas.

1 . A process for direct reduction of iron ore to sponge iron, wherein the iron ore passes through a reduction zone for reducing the iron ore to sponge iron, wherein the reduction zone is subdivided into a pre-reduction zone supplied with a first reduction gas and into an end-reduction zone supplied with a second reduction gas, wherein the first reduction gas has a different gas composition compared to the second reduction gas, wherein a first reduction gas having a hydrogen proportion at least 5% by volume higher compared to the second reduction gas is used. 
     
     
         2 . The process as claimed in  claim 1 , wherein the first reduction gas has a hydrogen proportion of at least 55% by volume. 
     
     
         3 . The process as claimed in  claim 2 , wherein the first reduction gas consists of hydrogen. 
     
     
         4 . The process as claimed in  claim 3 , wherein the first reduction gas is heated to a temperature between 500 and 1200° C. 
     
     
         5 . The process as claimed in  claim 4 , further comprising using a second reduction gas having at least one of (i) a higher proportion of at least one compound or mixture of carbon and hydrogen and (ii) at least one compound or mixture of carbon and oxygen compared to the first reduction gas. 
     
     
         6 . The process as claimed in  claim 5 , wherein the second reduction gas comprises at least one of (i) at least one compound or mixture of carbon and hydrogen and (ii) at least one compound or mixture of carbon and oxygen in a proportion of at least 55% by volume. 
     
     
         7 . The process as claimed in  claim 6 , wherein the second reduction gas comprises at least one of (i) at least one compound or mixture of carbon and hydrogen and (ii) at least one compound or mixture of carbon and oxygen in a proportion of at least 70% by volume. 
     
     
         8 . The process as claimed in  claim 7 , wherein as a result of the carbon-containing compound or mixture the second reduction gas brings about a carburizing of the pre-reduced iron ore in the end-reduction zone. 
     
     
         9 . The process as claimed in  claim 8 , wherein the carbon content of the sponge iron after passage through the end-reduction zone is in the range from 0.5% by weight to 3.5% by weight. 
     
     
         10 . The process as claimed in  claim 9 , wherein the second reduction gas is heated to a temperature between 700 and 1300° C. 
     
     
         11 . The process as claimed in  claim 10 , wherein the sponge iron passes through a cooling zone arranged downstream of the reduction zone which is supplied with a cooling gas. 
     
     
         12 . The process as claimed in  claim 11 , wherein the reduction zone above the cooling zone is arranged in a shaft furnace and the iron ore passes through the shaft furnace in a vertical direction. 
     
     
         13 . The process as claimed in  claim 11 , wherein the reduction zone comprises a pre-reduction zone and an end-reduction zone comprising at least one fluidized bed reactor in each case. 
     
     
         14 . The process of  claim 13  wherein the cooling zone comprises one or more fluidized bed reactors.