GB351098A - - Google Patents

Abstract

<PICT:0351098/III/1> Ammonium carbonate; metal salts.--Granular chemical fertilizers containing easily decomposable, hygroscopic, volatile or otherwise unstable substances are stabilized by subjecting them to a superficial chemical treatment whereby the surface layer only of each granule is converted into a more stable form so as to form a protective coating. For example granules of ammonium bicarbonate may be treated with a solution of sodium chloride whereby the granules are coated with a layer of sodium bicarbonate usually containing a small proportion of ammonium chloride. The substances reacting with the granules may be so chosen that the stable substance formed in the surface layer also possesses fertilizing properties. A solution of the reacting material, which may be in the form of a thin spray or mist, may be aspirated or forced through a thin layer of the granular material. The quantity of solution supplied may be regulated according to the desired depth of the reaction in the granules. The granules to be treated pass from a hopper 1, in amounts which may be regulated by an axially adjustable cone, to a disc centrifuge 2 having a covering disc 4, and escape from the disc in a narrow layer which is treated with a fine spray of a solution of the reacting material from an annular nozzle 5 surrounding the disc 2. The stream of granules treated in this way passes into a collecting chamber 6, and excess solution is received in a discharge trough 11. The granules may be dried by gentle heating. Alternatively, the solution may be supplied to the disc centrifuge, in which case the annular nozzle is replaced by an annular distributer.