Veba-Chemie Aktiengesellschaft

Walter Hilt

Manfred Schweppe

Heinrich Hahn

Hans Heumann

Heinz Liebing

An improved process in the preparation of sustained release fertilizer compositions which comprises subjecting a preponderantly water-soluble granular fertilizer composition first to accretive granulation under accretive granulation conditions with a melt, solution or slurry of one or several fertilizers and in a second stage coating these treated grains with a suitable almost impermeable envelopment.

Method of preparing fertilizers with retarded nutrient release

Ammonium polyphosphate is manufactured on a continuous basis by reacting gaseous ammonia and aqueous phosphoric acid at elevated temperatures in a one or multiple stage falling film reaction zone in the presence of a diluting gas if desired, using wet phosphoric acid, preferably containing 28-32%, by weight P.sub.2 O.sub.5 and an excess of ammonia. The phosphoric acid and the gaseous ammonia are preferably carried in counterflow and the temperature in the falling film reaction zone is adjusted using heat transfer fluids to within the range of 120.degree. - 260.degree. C.

Growing community of inventors

Herne, Germany

Walter Hilt