Method for rendering inert dust residue containing silicon metal

Abstract

The invention relates to a method for rendering inert dust residue containing silicon metal, left over from trichlorosilane synthesis. The inventive method produces valuable materials containing silicon which can be used in metallurgical processes. According to said method, the process of rendering the residue inert is carried out in several steps. In a first step, 10 to 50 wt. % water, in relation to the quantity of residue, and an at least equimolar quantity of an alkaline compound, in relation to the chloride content of the residue, are added to the residue. Subsequently or simultaneously, the residue is heated to a temperature of 50 to 200° C. In a further step, at least twice the quantity of water is added to this mixture, which is extensively liberated from dissolved salts by filtration and subsequent washing with water.

1 . A method for rendering inert dust residue containing silicon metal originating from the trichlorosilane synthesis, characterised by the following steps: 
 the residues are mixed with 10 to 50 weight percent water, in relation to the quantity of residue, and an at least equimolar quantity of an alkaline compound, in relation to the chloride content of the residue;    the mixture is heated to a temperature ranging from 50 to 200° C.;    the heated mixture is mixed with at least the double amount of water; and    subsequently the mixture is extensively liberated from dissolved salts by filtration and subsequent washing with water.    
     
     
         2 . A method according to  claim 1 , characterised in that the alkaline compound is provided at a molar excess of 2 to 10%, in relation to the chloride content of the residues.  
     
     
         3 . A method according to  claim 1  or  2 , characterised in that the alkaline compounds used are NaOH, Na 2 CO 3 , NaHCO 3 , CaO, Ca(OH) 2  or cement.  
     
     
         4 . A method according to  claim 1  or  2 , characterised in that the alkaline compounds used are CaO, Na 2 CO 3  and cement or mixtures thereof.  
     
     
         5 . A method according to any one of  claims 1  to  4 , characterised in that in the first step the mixture is heated to a temperature ranging from 100 to 150° C., preferably 120 to 140° C.  
     
     
         6 . A method according to any one of  claims 1  to  5 , characterised in that after heating the mixture is maintained at this temperature for a period of 10 to 60 minutes.  
     
     
         7 . A method for the execution of a metallurgical process, in particular for the production of an iron alloy or copper, comprising the following steps: 
 a) rendering inert dust residue containing silicon metal originating from the trichlorosilane synthesis, comprising the following steps of rendering inert: 
 the residues are mixed with 10 to 50 weight percent water, in relation to the quantity of residue, and an at least equimolar quantity of an alkaline compound, in relation to the chloride content of the residue;  
 the mixture is heated to a temperature ranging from 50 to 200° C.;  
 the heated mixture is mixed with at least the double amount of water; and  
 subsequently the mixture is extensively liberated from dissolved salts by filtration and subsequent washing with water;  
   b) utilisation of these inert residues in the subsequent metallurgical process.