Patent GB-498019-A (GB)
Title: Improvements relating to the production of cyanides
IPC: C01C3/00
Filed: 1937-07-02
Abstract: <PICT:0498019/III/1> <PICT:0498019/III/2> Cyanides are obtained by causing an inflammable gas to be burnt with atmospheric air to heat a mixture of carbonaceous matter and a basic or alkaline compound containing the metal corresponding to the cyanide required, atomizing or activating the atmospheric nitrogen contained in the combustion gases and causing the atomized or activated nitrogen to react with the heated mixture. The inflammable gases may be produced by destructively distilling a mixture of carbonaceous matter and the basic or alkaline compound.  The nitrogen may be atomized or activated by the passage of a silent electric discharge therethrough. Sodium cyanide, potassium cyanide, ferric cyanide, or with the addition of metals such as iron or copper, complex cyanides such as potassium ferrocyanide or potassium cuprocyanide may be produced by the process.  As shown, a mixture of carbonaceous matter and sodium-containing alkaline compound is fed from a hopper 1 by a screw device 2 through a pipe 3 into one end of a horizontal cylindrical pre-heating chamber 4, through which it is progressively fed by means of a series of separate impeller units 5 fixed on a central shaft 6. The impeller units have helical blades provided with flanges on the ends and on one side.  The inflammable gases evolved through the destructive distillation taking place in the chamber 4 pass through a passage 16 and pipe 17 to a nozzle 18 where the gases are burnt by means of air drawn through the surrounding horizontal tube 19.  The flame is arranged to impinge on a heap of coke or other solid 20. The combustion gases pass through a lower chamber 13B and through ports 31, Fig. 5, at the inner end thereof into an upper compartment 13A.  Herein they are subjected to a silent electric discharge produced by pairs of electrodes 21, 21a of variable length.  This activates the nitrogen present in the gases.  The gases containing the atomized nitrogen pass through passages 22 into the rear end of a reaction chamber 12 and flow therethrough in countercurrent to the solid mixture of carbonaceous material and sodium containing alkali which is fed by a screw device 10 from the chamber 4 through a passage 11 and is passed by further impeller units towards the rear end.  In this chamber sodium cyanide is formed and passes as a molten mass through a passage in a bearing block 9 and a nozzle 29 into a vessel 30.  The residual gases pass from the chamber 12 through passages 23 into an upper forward furnace chamber 14A and then downwards through ports into a lower chamber 14B.  As they pass through these chambers their heat effects the destructive distillation in the chamber 4.  The gases then pass around a horizontal partition 24, pre-heat the air entering through the tube 19, descend through a tube 25 and pass through caustic-soda solution in a tank 27.  This solution absorbs the carbon-dioxide and water vapour in the gases and creates a suction through the furnace.  The suction may be assisted, particularly when starting up by the attachment of a suction pump to a pipe 28. The alkali carbonates formed in the tank 27 may be used in the process.  Preferably with a gas temperature of 800-1000 DEG  C. a direct current of 200-300 volts is applied to the electrodes 21, 21a while maintaining a current density on the electrodes of 1,5-2,0 ampres per square inch. Containers containing caustic alkalies may be introduced into the activating chamber in order to remove solid impurities and carbon dioxide.  The reaction may be accelerated by the introduction of the ultimate cyanide product into the primary mixture.  The temperature of operation may be sufficiently high to volatilize simple cyanides which may be recovered by condensation.  The Provisional Specification describes also the production of atomized nitrogen by passing combustion gases through a stove containing heated refractory brick.