A Spray Column (or Spray Tower) is a gas-liquid contactor used to achieve mass transfer between a continuous gas phase (that can contain dispersed solid particles) and a dispersed liquid phase.
It consists of an empty cylindrical vessel made of steel or plastic, and nozzles that spray liquid into the vessel.
The inlet gas stream usually enters at the bottom of the tower and moves upward, while the liquid is sprayed downward from one or more levels.
This flow of inlet gas and liquid in opposite directions is called countercurrent flow. Theoretically, the smaller the droplets formed, the higher the collection efficiency achieved but the liquid droplets must be large enough to not be carried out of the scrubber by the scrubbed outlet gas stream.
In order to maintain low gas velocities, spray towers must be larger than other scrubbers that handle similar gas stream flow rates.