The Influence of Low Surface Tension on the Performence of Mist Eliminators

The influence of surface tension on the performance of mist separator

Wolfgang Heikamp, 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 droplets from gas streams. The design of these separators are mostly based on the following equation using a wire mesh characterizing K- factor,

Vc= K          ρ = ρ_L

Vc= design flow velocity and is 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.

This equation (Souders – Brown ) became an industrial standard to calculate a knitted wire mesh separators. There exist many proposals for the K factor in different applications.

Another design criteria was initially recommended by Bürkholz, based on considerable test data, which can also be used for the estimation of the flooding velocity.

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

In recent experimental studies with commercially available mist eliminators the influence of surface tension on the flooding velocity was investigated. A test rig was developed to study the flooding performance of mist eliminators with surface tensions from 68 mN/m down to 15 mN/m.

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