Demisters - Droplet Separator

Demister design

A demister is a droplet separator made of a mesh knitted from metal or plastic wires. The mesh is assembled in several layers and forms a demister pad, which is always oversized in width to avoid the gas bypassing the demister pad along the vessel wall.

Demister design, function and efficiency is determined by wire diameter, number of wires, number of mesh layers, mesh size and overall demister height.

The space between the wires is very evenly distributed throughout the demister and the surface area is extremely high per unit volume.

A smaller demister is manufactured as a unit with a support grid on each side of the demister pad. A larger demister consists of several sections to allow for insertion and removal through the manhole during installation and maintenance.

The mesh in each section is larger than the support grid to ensure a tight installation between the different segments and the vessel wall.

Separation efficiency

As the process gas passes through the demister, the liquid is trapped in the space between the wires, the droplets grow in size and are drained by the force of gravity.

The large volume of space in a demister means that the pressure drop is relatively low. Separation efficiency is 100% for droplets >5µm, provided that the demister design is based on correct process and operating data.

The illustration shows the separation refficienct for droplets >5µm at a given gas flow rate in % of the calculated maximum allowable gas flow velocity.

Choice of material

Choice of material depends on temperature and composition of the gas stream, among other things. Demisters are made in a variety of materials in different types of plastic or metal, such as

• 304L, 316L
• Polypropylene, PP
• Other special materials on request