Yara International Asa

Olav Lier

Robertus Louwe

A method for crystallizing calcium nitrate from an aqueous calcium nitrate composition including from 6 to 12 weight % nitric acid, from 11 to 17 weight % phosphoric acid, and from 36 to 49 weight % dissolved calcium nitrate, which aqueous composition is optionally directly obtainable from digesting phosphate rock in nitric acid. The method includes filling at least one vertical crystallizing tank through an inlet with the aqueous calcium nitrate composition. The crystallizing tank includes a vertical cylindrical section, a first inlet, a first outlet, a second inlet, three concentric banks of cooling coils, an agitator, and a temperature measurement device. The method includes circulating through the banks of cooling coils a cooling fluid, having an initial temperature ranging from −40° C. to −5° C., and rotating the agitator such that a minimum average heat transfer of 400 W/m·K is achieved on the cooling coil the most distant from the agitator.

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Porsgrunn, Norway

Olav Lier