A classifying fluid bed granulation unit includes a perforated bed floor; a fluid bed section; a solid feed inlet or internal crushing device; a fluidization air inlet; a liquid solution or melt feed inlet and nozzles; an air outlet; and a product outlet; wherein the fluid bed section comprises at least one particle classification element comprising one or more vertically inclined channels having top and bottom end feed openings, and wherein the one or more vertically inclined channels have upper and lower side slots. In operation of the above fluid bed granulation unit, each channel of the element is separating particles into large particle and small particle fractions and transporting the large particle fraction upwards and the small particle fraction downwards in each channel, and the large particle and small particle fractions are transported out of the upper and lower side slots, respectively.