GB737520A - Improvements in processes for the production of white calcium cyanamide - Google Patents

Abstract

Calcium cyanamide is produced by fluidizing calcium carbonate in a stream of gas comprising ammonia at a temperature of for example 400-850 DEG C. The temperature may be lower if the calcium carbonate is in very finely divided form. The water vapour produced by the reaction is removed as quickly as possible and the partial pressure thereof in the reaction zone maintained as low as possible, i.e. by employing rapid gas flow and an ammonia gas stream diluted with inert gas, for example carbon dioxide, flue gas, electric furnace waste gas, hydrogen or nitrogen. These gases also inhibit ammonia decomposition. Solid ammonia decomposition inhibitors can be mixed with the calcium carbonate, for example silica gel, active carbon, alumina or calcium sulphide. The reaction may be effected in and around pipes coated with an ammonia decomposition inhibitor, e.g. pure aluminium or fused or powdered aluminium oxide. A number of fluidized beds arranged in series may be employed. A gas flow of at least 2 cm./sec. and a proportion of ammonia in the gas of below 50 per cent may be employed.