Method for coating particles in a spray-drying plant

A method for producing a free-flowing powder comprising particles of a carrier material coated with a coating composition using a spray-drying plant comprising a spray-drying chamber and an atomizing means selected from a high-pressure atomizing nozzle and an atomizing wheel arranged in the spray-drying chamber, the method comprising

• supplying the coating composition in liquid form to the atomizing means of the plant and atomizing the liquid coating composition into a flow of droplets,
• supplying a flow of transport gas comprising particles of the carrier material dispersed therein to the spray-drying chamber separately from the coating composition,
• supplying a flow of drying gas to the chamber, the drying gas being of a temperature selected to solidify the liquid coating composition,
• allowing droplets in the flow of liquid droplets of the coating composition to collide with the particles of the carrier material dispersed in the transport gas, the direction and flow rate of the transport gas being adapted to substantially prevent contact between the drying gas and the droplets, so that the liquid coating composition, before any substantial drying thereof, will form a substantially continuous liquid coating layer on the particles, the flow of the transport gas with the particles of the carrier material dispersed therein and the flow of the drying gas being directed substantially parallel to each other and being regulated so that they form a substantially distinct interface of a substantially constant shape in a region upstream of and adjacent to the region where the collision between the liquid droplets and the particles takes place,
• then allowing the thus applied continuous coating layer on the particles to at least partially dry by contact with the drying gas, and
• withdrawing the coated particles from the spray-drying chamber.