Yara International Asa

Robertus Louwe

Petr Chladek

Patrycja Kita

Odd-Arne Lorentsen

Lene Sund

Olav Lier

Marie Lacombe

Ole Edvard Kongstein

Asbjørn Solheim

The present application relates to a process for the reduction of NOx from a gaseous effluent generated in the production of fertilizer comprising the acid digestion of phosphate ore in the presence of urea, wherein said gaseous effluent generated has a NOx composition of 70 to 100 mole % NOand 0 to 30 mole % NO, comprising the steps of: a) contacting said gaseous effluent for 0.5 to 15 seconds with ozone, thereby providing a resultant gas mixture wherein NO and NOpresent in the NOx are oxidized to higher nitrogen oxides; and; b) removing higher nitrogen oxides from said resultant gas mixture; wherein urea is present during said acid digestion of phosphate ore in an amount of 0.25 wt % or less based on the weight of said phosphate ore; and; ozone is added to said gaseous effluent in an ozone/NOx ratio ranging between 0.5 and 1.4.

NOx removal from gaseous effluents

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.

Method and crystallizing tank and arrangement thereof for crystallizing calcium nitrate from the nitro-phosphate process

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Porsgrunn, Norway

Robertus Louwe