Process and a plant 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, the process comprising the following steps:

• 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 the fluidized layer
• recovering particles from said fluidized layer and by an external pipe means transferring these to an external, separate after-treatment unit and subjecting said particles to at least one after-treatment selected from after-drying, cooling, classification including dust removal, agglomeration, coating and separation, involving gas contact in said unit and
• withdrawing a stream of dust-loaded gas from said unit through second external pipe means, wherein said dust-loaded gas stream is withdrawn by said second external pipe means conducted into the drying chamber, whereby the gas in this stream passes through the particle collecting filter inside the chamber before leaving the chamber together with said spent drying gas.