Method for producing shaped inorganic cyanide bodies and products obtained according to said method

Abstract

The invention relates to a method for producing shaped inorganic cyanide bodies, especially made of alkaline metal cyanides and alkaline earth metal cyanides, by pressing particulate inorganic cyanide obtained by means of a crystallization method. According to the invention, a cyanide crystallate separated from a mother liquor by means of a solid-liquid separation device and containing 2-15 wt. % water is fed to a forming device without the addition of an auxiliary forming agent and placed under pressure and compressed to form shaped bodies containing 0.1-12 wt. % water. The amount of water contained by the shaped bodies is always less than that contained in the crystallates used for the production thereof. Preferably, the crystallite is pressed out of a rotary filter or a centrifuge at a temperature of more than 40° C. to form shaped bodies containing 0.2-6 wt. % residual water. The inventive method can be carried out in a more economical manner than previously known methods using dried cyanide. The invention also relates to shaped inorganic cyanide bodies obtained according to said method.

1 . A process for producing shaped articles of inorganic cyanides, in particular alkali metal cyanides and alkaline earth metal cyanides, comprising shaping of particle-form inorganic cyanide, obtained by a crystallisation process, by means of a device for shaping the particle-form cyanide by press moulding, characterised in that 
 a cyanide crystallisate with a total water content of from 2 to 15 wt. %, separated off from a mother liquor during the crystallisation process by means of a solid/liquid separating device, is fed to a shaping device without the addition of a shaping auxiliary and press moulded under pressure into shaped articles with a water content in the range of from 0.1 to 12 wt. %, wherein the water content of the shaped articles is always lower than that of the crystallisate used in the production thereof.    
     
     
         2 . A process according to  claim 1 , characterised in that 
 press moulding in the shaping device proceeds at a temperature in the range of from 40 to 70° C.    
     
     
         3 . A process according to  claim 1  or  claim 2 , characterised in that 
 shaping is performed in a briquetting, tabletting or extrusion device.  
 
     
     
         4 . A device according to one of  claims 1  to  3 , characterised in that 
 cyanide crystallisate from a rotary filter with a water content of from 4 to 13 wt. % or from a centrifuge with a water content of from 2 to 10 wt. % is fed to the shaping device.  
 
     
     
         5 . A process according to one of  claims 1  to  4 , characterised in that 
 sodium cyanide or potassium cyanide crystallisate from a rotary filter or a centrifuge is converted into shaped articles, wherein the crystallisate is press moulded at a temperature above the transition temperature of sodium cyanide dihydrate (T u =35.7° C.) and at least partially dewatered at the same time.  
 
     
     
         6 . A process according to one of  claims 1  to  5 , characterised in that 
 shaping is performed above 40° C. under a pressure which allows dewatering to a shaped article residual water content (adherent moisture and hydrates) equal to or less than 6 wt. %, in particular 0.2 to 5 wt. %.  
 
     
     
         7 . Shaped articles of inorganic cyanides, especially alkali metal and alkaline earth metal cyanides, in particular sodium cyanide shaped articles, obtainable by the process according to one of  claims 1  to  6 .  
     
     
         8 . Shaped articles according to  claim 7 , characterised in that 
 they contain from 0.1 to 1 wt. %, in particular 0.2 to 0.7 wt. % of the metal hydroxide on which the cyanide is based.