Vessels are usually a type of pressure container that can be positioned either vertical or horizontal depending on space restriction. Some process may require the vessel to have internal components.
Columns are vertical vessels with multiple levels of internal trays or packings which act as a mass transfer device for the separation of liquids and vapours throughout the process.
Reactors are a type of vessel that contains a ‘catalyst or agitators’ which facilitate the process of changing the fluid or vapour that pass through the tubes. Depending on the operation, these units can be tall vertical vessels or some can be spherical shaped vessels.