Prodn. of urea fertiliser granules - using magnesium cpd. as crystallisation inhibitor

摘要

Prodn. of urea granules is effected by spraying an 85-98 wt.% aq. urea soln. contg. a crystallisation inhibitor (I) in the form of fine droplets (ave. dia. 20-120 micron) into a fluidised bed of urea particles at a temp. such that the water evaporates and the urea solidifies on the particles to form granules of the desired size. The improvement is that (I) is Mg(OH)2 and/or an inorganic Mg salt. The urea soln. may also contain one or more other fertiliser components, e.g. (NH4)2SO4, (NH4)H2PO4 and/or (NH4)2HPO4, in soln. and/or suspension. The amt. of (I) added is pref. equiv. to at least 0.1 (esp. 0.4-1.0) wt.% MgO based on the wt. of urea in the soln. Addn. of the Mg cpds. minimises dusting during granulation and produces granules which have a high crush strength, high bulk density and low caking tendency and are compatible in all proportions with superphosphate and triple phosphate granules. (Fl).