Granulation of powdered bleach activators - by spraying with binder soln. in fluidised bed

摘要

Granulation of powdered N-acetylated bleach activators is effected by fluidising the powder with air and spraying it with an aq. granulating liq. contg. a binder and opt. a surfactant. The powder is injected into the fluidisation chamber at a rate of 200-700 kg/m2.hr., together with up to 120% of this amt. of recycled undersized material ('cyclone dust'), along a path parallel to the median line of the circular chamber but displaced from it by 0.3-0.6 R, where R is the radius. The granulating liq. has a solids content of 15-40% and is injected vertically downwards from a point above the quadrant in which the powder inlet is located, in the form a spray cone whose perimeter is 0.0025-0.1 R from the chamber wall at the level of the fluidised bed. The air flow rate is at least 2000 m3/m2.hr. and is such that the relative humidity of the outlet air does not exceed 95%. The amt. of powder (x) and the amt. of solids supplied by the granulating liq. are such that y = a/x + 0.04, where a = 35-45. USE/ADVANTAGE - The process may be used to granulate bleach activators such as 1,5-diacetyl-2,4-dioxo-hexahydro-1,3,5 -triazine, tetraacetyl-ethylenediamine or tetraacetylglycouril. The process is energy-efficient, allows precise control of the active content of the granules, and gives uniform-sized granules with good storage stability, esp. as components of detergent compsns