GB742386A - Manufacture of ammonium bicarbonate - Google Patents

Abstract

Ammonium bicarbonate is produced by absorbing equimolecular quantities of ammonia and carbon dioxide in an aqueous solution containing carbon dioxide and ammonia in the ratio of 1 : 1 to 3 : 4 by weight and nearly saturated therewith, said absorption being carried out at a temperature of 30-35 DEG C. at atmospheric pressure in a packed tower, allowing the temperature to rise to 45-50 DEG C., cooling the resulting solution to 25-30 DEG C. to produce a supersaturated solution, and crystallizing ammonium bicarbonate therefrom, e.g. in the presence of seed crystals. The mother liquor resulting after separation of the crystallized ammonium bicarbonate is returned to the absorption process, after the addition of make-up water if necessary. An absorption of equimolecular amounts of ammonia and carbon dioxide is effected by adjusting the proportions of these gases fed to the tower. An excess of up to 20 per cent carbon dioxide may be employed. Prior to the main absorption step, the solution may be treated with gaseous or aqueous ammonia, and then cooled. Lime kiln gas may be used as a source of carbon dioxide. The waste gas from the absorption tower may be washed with water, and the resulting solution used as make-up water.