Furnace for the direct reduction of iron oxides and method for the manufacturing thereof

Abstract

A gravitational furnace for the direct reduction of mineral iron, comprising a substantially cylindrical container, a reactor arranged in a median zone of the container, between a device to feed the mineral iron and a zone to discharge the reduced metal iron. Distribution nozzles are provided in the peripheral wall of the cylinder to introduce reducing gas into the reactor. A substantially cylindrical passive element is inserted into the furnace inside the container, substantially coaxial with its longitudinal axis, to define a substantially annular reaction chamber of the reactor. Also the manufacturing of the furnace is disclosed.

1  - Gravitational furnace for the direct reduction of mineral iron, comprising a substantially cylindrical container having a substantially vertical longitudinal axis, feeding means disposed on the upper part of said container to feed the mineral iron, a reactor disposed in a median zone of said container, a lower zone to discharge the reduced metal iron, and distribution means disposed on the peripheral wall of said cylindrical container to introduce reducing gas into said reactor, wherein a substantially cylindrical passive element is disposed inside said cylindrical container, substantially coaxial to said longitudinal axis, to define a substantially annular reaction chamber of said reactor and wherein the inner diameter (d 1 ) of said cylindrical container and the outer diameter (d 2 ) of said cylindrical passive element have values which cause that both the cross-section of said annular reaction chamber is maximised and the distribution of said reducing gas coming from said distribution means is optimised.  
     
     
         2  - Furnace as in  claim 1 , wherein said passive element is made of refractory material.  
     
     
         3  - Furnace as in  claim 1 , wherein said passive element is tubular in shape.  
     
     
         4  - Furnace as in  claim 1 , wherein said passive element has an upper end shaped like a truncated cone, so as not to impede the downwards flow of the mineral iron introduced from above.  
     
     
         5  - Furnace as in  claim 1 , wherein said passive element has a lower end shaped like a truncated cone to facilitate the flow of the reduced metal iron towards said discharge zone.  
     
     
         6  - Furnace as in  claim 1 , wherein supporting means are provided to connect said passive element to said container.  
     
     
         7  - Furnace as in  claim 1 , wherein said reaction chamber has a diameter (d 1 ) variable preferably between about 7 and 10 meter and wherein the diameter (d 2 ) of said passive element is variable preferably between about 2 and 4.5 meter, so that the transverse width (s) of said reaction chamber advantageously has a value of between about 2.5 and 2.7 meter.  
     
     
         8  - A method to manufacture a furnace according to any of the preceding claims, wherein it comprises the step of calculating the inner diameter (d 1 ) of said cylindrical container and the outer diameter (d 2 ) of said cylindrical passive element, with respect to an diameter (d 3 ) of a furnace without any central element, by applying the following system of equations:  
       
         
           
             
               { 
               
                 
                   
                     
                       
                         
                           π 
                           · 
                           
                             
                               d 
                               1 
                               2 
                             
                             4 
                           
                         
                         - 
                         
                           π 
                           · 
                           
                             
                               d 
                               2 
                               2 
                             
                             4 
                           
                         
                       
                       = 
                       
                         π 
                         · 
                         
                           
                             d 
                             3 
                             2 
                           
                           4 
                         
                       
                     
                   
                 
                 
                   
                     
                       
                         
                           
                             d 
                             1 
                           
                           2 
                         
                         - 
                         
                           
                             d 
                             2 
                           
                           2 
                         
                       
                       = 
                       s 
                     
                   
                 
               
             
           
           
           
               
           
         
       
       where s is the transverse width of said reaction chamber.