Improvements in or relating to the preparation of cyanamide

摘要

In preparing cyanamide as claimed in the parent Specification, the calcium cyanamide slurry is passed to a central portion of a zone of centrifugal action and a gaseous calcium precipitant such as carbon dioxide, sulphur dioxide or sulphur trioxide is simultaneously fed to the central portion of the zone, intimate contact between the slurry and the precipitant is caused by centrifugally forcing the mixture between closely spaced blades of a rotor and a stator, the resultant slurry is removed from the zone and an aqueous solution of cyanamide is recovered therefrom. As shown, a closed vessel 1 is charged with water or a weak cyanamide solution, and a calcium cyanamide slurry is fed continuously through a line 4. Carbon dioxide is introduced through a duct 5 and is distributed by means of a rotor 2 being driven through radially-displaced stator blades 3 to be thoroughly mixed with the calcium cyanamide slurry. The reaction product containing free cyanamide in solution and calcium carbonate is forced out over a deflecting plate 10 and through a duct 9 to a filter. The filter solids are washed with water, the resulting wash liquor being returned to the apparatus for further extraction of crude calcium cyanamide. The whole apparatus may be under a super-atmospheric pressure of carbon dioxide.