Method for upgrading steel plant dust

Abstract

The invention concerns a method for upgrading steel plant dust to recuperate industrially reusable compounds. Said method comprises an attrition and dilution step, a solid/liquid separating and solid washing step, an acid leaching step, and acid purification step comprising a carburizing reaction or a carburizing and decalcification reaction. Said method is characterised in that it comprises an oxidation/neutralisation step which includes a step oxidizing iron into iron oxyhydroxides and/or iron oxides and a neutralizing reaction of the reaction medium.

1 . A method for utilising steelworks dust with a view to recovering industrially reusable compounds, said method having an attrition and dilution step, a step of solid/liquid separation and washing of the solid, an acid lixiviation step, an acid purification step comprising a cementation reaction or a cementation and decalcification reaction, said method being characterised in that it comprises an oxidation/neutralisation step, said step comprising a reaction of oxidation of the iron into iron oxyhydroxides and/or iron oxides and a reaction of neutralisation of the reaction medium.  
     
     
         2 . A method according to  claim 1 , characterised in that the oxidation reaction is carried out by means of an oxidant taken from the group comprising hydrogen peroxide, oxygen and air.  
     
     
         3 . A method according to either of the preceding claims, characterised in that the neutralisation reaction is carried out by means of a solution of soda, potash, sodium bicarbonate, potassium bicarbonate, ammonia or similar, in order to maintain the pH of the reaction medium substantially between 2.5 and 5.  
     
     
         4 . A method according to one of the preceding claims, characterised in that the oxidation and neutralisation step is carried out substantially between 10° C. and 100° C.  
     
     
         5 . A method according to one of the preceding claims, characterised in that the acid lixiviation step is carried out by means of a sulphuric acid solution titrating substantially between 8% and 25% acid and at a temperature substantially between 50° C. and 100° C.  
     
     
         6 . A method according to one of the preceding claims, characterised in that the acid purification is carried out at a pH substantially between 2 and 4 and at a temperature substantially between 20° C. and 100° C.  
     
     
         7 . A method according to one of the preceding claims, characterised in that a hydraulic classification step is carried out after the attrition and dilution step and before the step of liquid/solid separation and washing of the solid.  
     
     
         8 . A method according to one of the preceding claims, characterised in that it comprises a basic lixiviation step following the step of solid/liquid separation and washing of the solid.  
     
     
         9 . A method according to one of the preceding claims, is characterised in that metallic zinc, zinc oxides and/or zinc ferrite are recovered from the liquid phase resulting from the oxidation/neutralisation step.  
     
     
         10 . A method according to one of the preceding claims, characterised in that it comprises a step of drying and/or heat treatment of the solid phase resulting from the oxidation/neutralisation step enabling iron oxides and/or iron oxyhydroxides to be obtained.  
     
     
         11 . A method according to one of the preceding claims, characterised in that it comprises a step of electrolysis of the liquid phase resulting from the oxidation/neutralisation step, enabling metallic zinc to be obtained.  
     
     
         12 . A method according to  claim 8 , characterised in that the solid phase resulting from the basic lixiviation step undergoes the acid lixiviation step.  
     
     
         13 . A method according to  claim 8 , characterised in that the liquid phase resulting from the basic lixiviation step undergoes a basic purification step.  
     
     
         14 . A method according to  claim 13 , characterised in that the basic purification step comprises a cementation reaction or a cementation and desilylation reaction.  
     
     
         15 . A method according to  claim 13  or  14 , characterised in that an electrolysis step follows the basic purification step, enabling metallic zinc and/or zinc oxides to be isolated.