US 5,958,588 AGranted

Process for preparing alkali metal cyanide and alkaline earth metal cyanide granules and the high purity alkali metal cyanide granules obtainable thereby

AssigneeDegussa-Huls AG

InventorsRudiger Schutte, Hans Christian Alt, Catrin Becker-Balfanz, Manfred Sauer, Lukas Von Hippel, Oliver Feuer, Jurgen Lorosch

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Abstract

A process for the direct preparation of alkali metal cyanide and alkaline earth metal cyanide granules from an HCN-containing gas and an aqueous solution or suspension of an alkali metal or alkaline earth metal hydroxide. The reaction is performed in a reactor for fluidized bed spray granulation, wherein a solution or suspension of the hydroxide is sprayed onto seed granules of the cyanide being prepared and at the same time a hydrogen cyanide-containing gas is supplied to the reactor and water is evaporated by means of a fluidizing gas. The preferred fluidizing gas is steam. The reaction gases from a BMA or Andrussow process may be quenched with water and the gas mixture used as fluidizing gas. By using a CO.sub.2 -free HCN-containing gas, alkali metal cyanide granules with advantageous properties, including a combined concentration of alkali metal carbonate and alkali metal formate of less then 0.4 wt. %, are obtainable.

Claims18

Dependent claims

A process for preparing alkali metal cyanide or alkaline earth metal cyanide granules in a reactor including reacting hydrogen cyanide with an alkali metal hydroxide or alkaline earth metal hydroxide, wherein the alkali metal hydroxide is sprayed into the reactor as an aqueous solution or the alkaline earth metal hydroxide is sprayed into the reactor as an aqueous suspension and there reacted with gaseous hydrogen cyanide, and evaporating the water introduced to and formed in the reactor;

wherein said process comprises carrying out the reacting step in a reactor having a fluidized bed for fluidized bed spray granulation at a fluidized bed temperature in the range 100.degree. to 250.degree. C.;
spraying the solution or the suspension onto the fluidized bed that consists essentially of seed granules of alkali metal cyanide or alkaline earth metal cyanide being produced,
simultaneously supplying a hydrogen cyanide-containing gas to the reactor in an amount of at least one mole of HCN per metal equivalent;
reacting said solution of alkali metal hydroxide or suspension of alkaline earth metal hydroxide with said hydrogen cyanide gas in a neutralization reaction;
and
evaporating the water by means of a stream of fluidizing gas, having an inlet temperature between 110.degree. and 500.degree. C., flowing through the fluidized bed.

3 more elements

Dependencies are inferred from the claim text.