The Influence of Surface Tension On the Performance of Mist Separator, Part II

The influence of surface tension on the performance of mist separator

Part 2: Effect of density, wettability and co knit material

Wolfgang Heikamp, Rhodius GmbH

Armin Pitzer, Rhodius GmbH

Attilio Praderio, Conoco Philipps

Prof. Dr. Michael Schultes, Raschig GmbH

In many chemical, refinery and petrochemical processes wire mesh mist separators are installed to remove fine droplet from gas streams. The design of these separators are mostly based on the following equation using a wire mesh characterizing K- factor,

Vc= K  QUOTE            ρ = ρ_L

Vc= design flow velocity

This equation ( Saunders – Brown ) became an industrial standard to calculate a knitted wire mesh separator. There are many  individually proposal for the K factor at different application.

Another  design criteria was initially recommended by Bürkholz, based on many test datas, which can also used for the estimation of  the flooding velocity. Vc as a function of the L/V liquid/gas mass flow ratio, the density difference between liquid and gas Δρ and the liquid density ρ_L.

It has to be noticed that this equation does not take into account any surface tension and wettability effects and is only proved for air/water systems. Based on other gas/liquid separation processes it is well known that low surface tensions (especially below 20 mN/m) are reducing the flooding velocity of equipments.

In recent experimental studies with commercially available mist eliminators the influence of  surface tension, wettability and co knit material on the flooding velocity was newly investigated. A test rig was developed to study the flooding performance of mist eliminators with surface tensions from 68 mN/m down to 12 mN/m.

The results of these experimental investigations will be presented and compared to literature data. In addition an outlook will be given for further work.