Process and an apparatus for spray drying

A process for spray drying a liquid to produce an agglomerated product by atomizing the liquid into a drying chamber to form droplets, introducing a first stream of drying gas downward into the upper part of said chamber to partially dry the droplets, introducing a second stream of drying and fluidizing gas upward in the bottom portion of the chamber through a perforated plate to maintain a fluidized layer of particles on said plate, withdrawing a stream of spent drying gas comprising gas from said first and said second stream of gas from the chamber through particle collecting filter means thereby retaining particles on the surface of said filter means, releasing said retained particles from the filter means, to allow their contacting other particles in the chamber for agglomeration and transfer into a first fluidized layer in the chamber, from where the particles after further drying pass to a second fluidized layer intimately united to and encircling or immediately beneath said first fluidized layer for an after-treatment comprising at least one treatment selected from after-drying, cooling, classification including dust removal, agglomeration, coating and separation, and dust-loaded gas is withdrawn from a location above said second fluidized layer by pipe means and by said means introduced into the drying chamber from where said gas passes through the particle-collecting filter inside the chamber before leaving the chamber together with said spent drying gas.