Sieve plates and distillation columns

A distillation column which is provided with a plurality of spaced sieve plates, characterised in that the sieve plates are of polymeric material and are mounted on a central shaft coaxial with the column, said sieve plate comprising:

• (a) a circular base portion provided with
• (i) a central axial aperture adapted to receive the shaft,
• (ii) an additional aperture spaced from the central aperture and capable of receiving a tubular member acting as a weir and a downcomer, and
• (iii) a plurality of perforations such that the perforations represent in total a free area of between 3 and 20%, the perforations having a uniform average diameter between 0.6 and 4.0 mm,
• (b) a flexible, flared-lip portion around the circumference of the base providing sealing contact with the inner walls of the column and providing a reservoir for downcoming liquid, and
• (c) means for retaining the plate on the shaft.