A tower is a cylindrical welded structure process equipment consisting of a shell, tower head (or tower cover), and support, suitable for distillation, absorption, and extraction to complete heat and mass transfer processes in the chemical industry.

According to their structure, they can be divided into two types: plate towers and packed towers.

Commonly used are foam tower, packed tower, serrated plate tower, spray plate, float valve tower, Kate tower, overlapping tower (S-type tower), tongue tower, circulating plate tower, rotating plate tower and guide screen tray tower.