The operation of the spray dryer is relatively simple.  A slurry is atomized into the drying chamber in the form of droplets.

150 Hp drive for direct-driven rotary wheel atomizer being tested in laboratory test pit

When these droplets contact the warm gases, they dry to a powder.

The hot gases, generated by either steam coils or a combustion furnace, enter the cylindrical drying chamber at various points, depending on the type of dryer.  in the parallel-flow configuration, the air enters through the top; in the mixed flow configuration, the air enters tangentially; and, in the reverse flow configuration, the air enters though the bottom.

SWENSON Test Center spray dryer designed primarily for use in laboratory and pilot plants

Atomization may be achieved in one of three ways: (1) high pressure nozzles, (2) two-fluid nozzles, or (3) centrifugal atomizers.  The selection of the proper atomizer is governed by the characteristics of the material to be dried.

Any product which is removed from the chamber by the spent drying gases is separated from them by means of a cyclone or a fabric filter dust collector.

Operating diagram of a parallel-flow SWENSON spray dryer for special products

  The exhaust gases can be further cleaned by a wet scrubber if required.

A spray dryer can also be operated in a closed loop using an inert gas, such as nitrogen, as the drying medium. 

SWENSON 22' diameter mixed-flow spray dryer used for drying silica gel catalyst