Method for the reduction of nickel from an aqueous solution

Abstract

The invention relates to a method for the precipitation of nickel from an aqueous solution containing its sulphate as a metallic powder suitable as an alloying element for refined steel. In this method, nickel reduction takes place continuously in one or several autoclaves at a temperature of 80-180 ° C. and hydrogen pressure of 1-20 bar, whereby the production capacity can be raised significantly, compared to batch processes made in correspondingly dimensioned devices or equipment.

1 . A method for the reduction of nickel powder suitable as a component of refined steel, from an aqueous solution containing nickel sulphate in a pressurised space using hydrogen reduction, characterised in that reduction occurs continuously at a temperature between 80-180° C. and at hydrogen pressure between 1-20 bar in at least one autoclave equipped with a mixer.  
     
     
         2 . A method according to patent  claim 1 , characterised in that reduction occurs at a temperature between 110-160° C. and at hydrogen pressure between 2-10 bar.  
     
     
         3 . A method according to patent  claim 1 , characterised in that reduction occurs in at least one autoclave, which is divided into sections by partitions, and where each section is equipped with a mixer.  
     
     
         4 . A method according to patent  claim 3 , characterised in that the solution surface of the slurry decreases by section in the direction of the solution flow.  
     
     
         5 . A method according to patent  claim 1 , characterised in that reduction occurs in several autoclaves, which are arranged in series and equipped with mixers.  
     
     
         6 . A method according to patent  claim 5 , characterised in that the autoclaves are single-sectioned.  
     
     
         7 . A method according to any of the above patent claims, characterised in that the autoclaves arranged in series are both single and multi-sectioned.  
     
     
         8 . A method according to some of the above patent claims, characterised in that the autoclaves are essentially cylindrical in shape.  
     
     
         9 . A method according to patent  claim 1 , characterised in that the nickel content of the aqueous solution containing nickel sulphate to be fed into the pressurised space is at least 30 g/l.  
     
     
         10 . A method according to patent  claim 9 , characterised in that the nickel content of the aqueous solution of nickel to be fed into the pressurised space is at least 50 g/l, preferably at least 80 g/l.  
     
     
         11 . A method according to patent  claim 1 , characterised in that the composition of the aqueous solution containing nickel sulphate to be fed into the pressurised space, that is the feed solution, is adjusted at the feed solution preparation stage.  
     
     
         12 . A method according to patent  claim 1 , characterised in that a reduction catalyst is used to aid reduction.  
     
     
         13 . A method according to patent  claim 12 , characterised in that iron (II) sulphate, FeSO 4 , is used as reduction catalyst.  
     
     
         14 . A method according to patent  claim 12 , characterised in that chrome (II) sulphate, CrSO 4 , is used as reduction catalyst.  
     
     
         15 . A method according to patent claims  11  or  12 , characterised in that the reduction catalyst is added to the feed solution at the preparation stage.  
     
     
         16 . A method according to patent  claim 12 , characterised in that the reduction catalyst is added to the feed solution just before the solution is fed into the pressurised space.  
     
     
         17 . A method according to patent  claim 12 , characterised in that the reduction catalyst is fed directly into the pressurised space.  
     
     
         18 . A method according to patent  claim 1 , characterised in that the solution to be fed into the pressurised space is neutralised at the preparation stage with ammonia so that the mole ratio becomes 1.6-2.4.  
     
     
         19 . A method according to patent  claim 1 , characterised in that the nickel solution is neutralised with ammonia in the pressurised space so that the mole ratio becomes 1.6-2.4.  
     
     
         20 . A method according to patent  claim 1 , characterised in that the nickel solution contains practically no ammonium sulphate.  
     
     
         21 . A method according to patent  claim 1 , characterised in that the suspension of nickel powder and solution is removed from the pressurised space and from which suspension the nickel powder is separated.  
     
     
         22 . A method according to patent  claim 21 , characterised in that the nickel remaining in the end solution after separation is removed by sulphide precipitation or ion exchange.  
     
     
         23 . A method according to patent  claim 21 , characterised in that at least part of the nickel remaining in the end solution after separation is removed as a binary salt NiSO 4 .(NH 4 ) 2 SO 4 .6H 2 O.  
     
     
         24 . A method according to patent  claim 23 , characterised in that when the majority of the nickel from the end solution has been recovered as a binary salt, the residual nickel is removed from the end solution either by sulphide precipitation or ion exchange.  
     
     
         25 . A method according to patent  claim 23 , characterised in that binary salt NiSO 4 .(NH 4 ) 2 SO 4 .6H 2 O is dissolved in the preparation stage of the feed solution and returned as feed for the continuous hydrogen reduction of nickel in a pressurised space.  
     
     
         26 . A method according to patent  claim 23 , characterised in that binary salt NiSO 4 .(NH 4 ) 2 SO 4 .6H 2 O is dissolved in the preparation stage of the feed solution and fed to the hydrogen reduction of nickel as a batch process.  
     
     
         27 . A method according to some of the above patent claims, characterised in that binary salt NiSO 4 .(NH 4 ) 2 SO 4 .6H 2 O is dissolved using ammonia.  
     
     
         28 . Nickel powder, characterised in that the powder is made by hydrogen reduction of an aqueous solution containing nickel sulphate, performed continuously in a pressurised space at a temperature between 80-180° C. and a hydrogen pressure of 1-20 bar.  
     
     
         29 . Nickel powder according to patent  claim 28 , characterised in that a catalyst is used in reduction.  
     
     
         29 . Nickel powder according to patent  claim 28 , characterised in that the iron content of the nickel powder is 0.1-2.0%.  
     
     
         30 . Nickel powder according to patent  claim 28 , characterised in that the iron content of the nickel powder is 0.6-1.4%.