Granulated fertilizer containing water soluble forms of nitrogen, magnesium and sulphur with ammonia and magnesium cations and sulphate and nitrate anions and method of preparation thereof

摘要

Granulated fertilizer containing water soluble forms of nitrogen, magnesium and sulphur contains 15 to 30 % by weight of nitrogen, 1 to 18 % by weight of sulphur, 2 to 10 % by weight of magnesium, expressed as magnesium oxid MgO, in the form of boussingaultite (NH4)2SO4.MgSO . 6H2O and binary salts of ammonium nitrate 2NH4NO3.(NH4)2SO4 and 3NH4NO3.(NH4)SO4, where the content of boussingaultite in fertilizer is 40 to 45 % by weight. It is prepared in such a manner, that magnesite is treated with concentrated nitrous acid, containing 30 to 80 % HNO3, at the temperature from 60 °C to 130 °C, the treatment results in reaction mixture containing magnesium nitrate, calcium nitrate, eventually, according to the content in magnesite, nitrates of iron, manganese or other metal elements, and the rest of indecomposed magnezite; subsequently, the reaction mixture is neutralized with alkaline agent to the pH value 3 to 7.5; the neutralized reaction mixture is then reacted with ammonium sulphate at the temperature 80 °C to 130 °C during 20 to 80 minutes, where the result of reaction is the pulp of boussingaultite (NH4)2SO4.MgSO . 6H2O containing 10 to 30 % by weight of water, and this pulp is mixed with recycled material from previous production in the ratio 1 : 2 to 1 : 10 and granulated; the process results in wet granulate, from which after removing free water the final product is obtained.