Method and apparatus for the direct reduction of iron ores utilizing syngas

Abstract

A direct reduction plant for the production of a metallized product (DRI) by the reduction of iron ores in lump or pellet form, wherein the reducing gas utilized in the DRI reactor contains acid gases such as sulphur compounds and carbon dioxide. The make-up reducing gases are typically produced by partial oxidation of hydrocarbons (syngas) at a high pressure while the DRI reactor is usually operated at a lower pressure. The pressure level of the reducing gas effluent from the DRI reactor (top gas), after cooling and dewatering, is increased to the pressure level of the syngas and the resulting recycle reducing gas is then combined with the make-up syngas and treated in a single acid-gas absorption unit forming a combined stream of clean upgraded reducing gas which thereafter is expanded in a turbine for lowering combined reducing gas pressure to the pressure level of the DRI reactor and is then heated to a temperature preferably above 950° C. and used in the DRI reactor for producing said DRI. The compressor for raising the pressure of the initially cool recycle gas uses energy from the expansion turbine (used for lowering the pressure of the high-pressure combined reducing gas).

1 . A process for producing DRI in a reduction reactor utilizing make-up reducing gases containing sulphur compounds and/or carbon dioxide from a high-pressure source at a pressure level higher than the mean pressure level of operation of the DRI reactor, said process comprising reacting in the reactor at a temperature above about 800° C. lumps or pellets of iron ore with a first stream of recycle reducing gas that has been upgraded to be effective to produce said DRI, the great majority of which stream comprises hydrogen and carbon monoxide; withdrawing as a second stream the depleted reducing gas from said reduction reactor for recycling and subsequent upgrading; scrubbing and cooling said second stream for removing water thus producing a third stream of cold and dewatered recycle reducing gas; increasing the pressure of at least a portion of said third stream and combining such portion with the make-up reducing gases from the high-pressure source to form a fourth stream of high-pressure recycle reducing gas; removing acid gases including said sulphur compounds and carbon dioxide from said fourth stream to form a fifth stream of clean upgraded recycle reducing gas; lowering the pressure of said fifth stream by expansion in a turbine and using energy derived from such expansion to achieve the increase in pressure of said third stream; and increasing the temperature of said fifth stream to above about 800° C. to form said first stream. 
     
     
         2 . A process according to  claim 1 , wherein said reduction reactor is a moving bed reactor and the DRI is continuously discharged. 
     
     
         3 . A process according to  claim 2 , wherein the temperature of said fifth stream is raised above 830° C. 
     
     
         4 . A process according to  claim 3 , wherein said reducing gases containing sulphur and/or carbon dioxide are produced by partial oxidation of hydrocarbons. 
     
     
         5 . A process according to  claim 4 , wherein said hydrocarbon is a liquid derived from oil. 
     
     
         6 . A process according to  claim 4 , wherein said hydrocarbon is coal. 
     
     
         7 . A process according to  claim 4 , wherein the pressure level of the source of said reducing gases is in the range from 20 to 40 bars absolute. 
     
     
         8 . A process according to  claim 7 , wherein the pressure level in the reduction reactor is in the range of 2 to 7 bars absolute. 
     
     
         9 . A process according to  claim 8 , wherein the pressure level of said fifth stream is in the range of 6 to 10 bars absolute. 
     
     
         10 . A process according to  claim 9 , wherein temperature ranges from about 950° C. to about 1020° C. 
     
     
         11 . A process according to  claim 10 , wherein the composition of the first stream has a composition with a ratio of H 2 /CO in the range from 1.5 to 4.0 in volume percent. 
     
     
         12 . A process according to  claim 3 , wherein said reducing gases containing sulphur and/or carbon dioxide are produced as a syngas by partial oxidation of composition chosen from the group consisting of fossil fuels and biomass. 
     
     
         13 . A process according to  claim 2 , wherein the composition of the make-up reducing gases when combined with the third stream has a composition with a ratio of H 2 /CO in the range from 2 to 3 in volume percent. 
     
     
         14 . A process according to  claim 1 , further comprises cooling DRI in a cooling zone of said reduction reactor.