Swenson manufactures spray dryers suitable for parallel, reverse, or mixed flow operation. The operation of the spray dryer is relatively simple. A slurry is atomized into the drying chamber in the form of droplets. 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 through the bottom.
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.
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.