GRANULAR FERTILISER CONTAINING WATER-SOLUBLE FORMS OF NITROGEN, MAGNESIUM AND SULPHUR AND PREPARATION METHOD THEREOF Russian patent published in 2012 - IPC C05C1/00 

FIELD: chemistry.

SUBSTANCE: granular fertiliser containing water-soluble forms of nitrogen, magnesium and sulphur contains 18-24 wt % nitrogen, 8-12 wt % sulphur, 3-6% magnesium, expressed as magnesium oxide MgO, in form of boussingaultite - (NH₄)₂SO₄MgSO₄·6H₂O, and double salts of ammonium nitrate - 2NH₄NO₃(NH₄)₂SO₄ and 3NH₄NO₃·(NH₄)₂SO₄. Magnesite is treated with concentrated nitric acid containing 30-60% HNO₃ to form a reaction mixture containing magnesium nitrate, calcium nitrate and other nitrates according to content of metal compounds in magnesite, and a residue - undecomposed magnesite. The reaction mixture is neutralised with an alkaline reagent to pH 2-6, left to allow reaction with ammonium sulphate at temperature 80-120°C for 20-80 minutes to form a suspension of boussingaultite - (NH₄)₂SO₄MgSO₄·6H₂O, containing 10-30 wt % water. The suspension is mixed with a recycled product of the previous production in ratio 1:2-1:4 and granulated to form a moist granulate, from which the end product is obtained after removing free water.

EFFECT: obtaining fertiliser which is suitable for growing plants on soils with low content of water-soluble magnesium and for plants which require fast delivery of nutrients.

16 cl, 4 ex