Question

Compare and contrast the three types of plates in plate distillation systems.

Answer 1

Answer:-

In a plate distillation column as the name suggests number of plates or trays are persent in column which makes the distillation process easier and accurate. There are various types of trays used which are decided on many factors such as cost, vapour capacity, pressure drop, mass transfer efficiency, etc. There are three main types of plate. They are discussed below:-

1. Sieve Trays- These trays are mostly known for there low cost. These trays are made of normal metals designed in plate form with number of perforated holes in it. From this tray fluid vapour pass straight upward through the fluid or liquid persent on plate. Sieve tray has lowest pressure drop amd efficiency but has highest vapour capacity .

2. Bubble Cap Trays - In this type of tray the metal plates consist of number of holes and each hole is attached to a riser or chimney fitted over it. The bubble cap is mounted over hole which create space between riser and the cap through which vapour passes. Vapor rises up by passing through these chimney or riser which is sent down by the cap and finally it escape by bubbling through liquid present on plate. These trays are mostly used when liquid holdup has to be controlled . The cost of bubble cap tray is highest but has lowest vapour capacity . While the bubble cap tray has highest pressure drop and efficiency .

3. Valve Trays - In this type of tray the metal plate are perforated and these perforations or holes are occupied by liftable caps. The fluid vapour moving up lifts the cap and create a passage for flowing vapour itself. These tray provide better mixing then sieve tray. Valve tray has pressure drop in between of bubble cap tray and sieve tray. Like bubble cap tray, valve tray has higher efficiency and like sieve tray, valve tray has highest vapour capacity.