Traykolonner

Traykolonner are a type of distillation column that use a series of perforated trays to promote contact between rising vapour and descending liquid. The trays provide surfaces where mass transfer can occur, improving the separation of components with different volatilities. The Swedish term is often used in engineering contexts to distinguish plate (tray) columns from packed columns.

Operation in a tray column begins with feed entering the column. Vapour rises through the trays, while liquid flows across each tray and down through downcomers to the tray below. On each tray, a portion of the liquid evaporates into the vapour phase and a portion of the vapour condenses into the liquid phase, allowing components to equilibrate. The overall separation is governed by the number of theoretical stages (trays) and the reflux ratio, which recycles liquid back to the top of the column.

Common tray designs include bubble-cap trays, sieve trays, and valve trays. Bubble-cap trays use caps to break vapour into small bubbles; sieve trays have perforations in the tray deck; valve trays incorporate movable, check-like valves. The choice of tray type depends on factors such as feed foaming tendency, liquid viscosity, pressure drop, and operating conditions.

Tray columns are often compared with packed columns. Tray columns offer easier control and good performance for feeds that foam or contain heavy impurities, and they facilitate inspection and maintenance. However, they typically involve higher pressure drops and a larger footprint for the same separation, and are more prone to flooding at high liquid rates.

Design and analysis commonly use methods related to theoretical stages and tray efficiency, with the McCabe–Thiele approach providing guidance for determining the required number of trays and reflux to achieve a target separation. Tray kennels are constructed from materials suited to the process, including carbon steel and stainless steel, and are used across petrochemical, solvent, and pharmaceutical industries.