Mist Eliminators
 

DESIGN ADVICE

Comprehensive performance information is available on a wide range of standard designs, enabling KnitMesh engineering staff to tailor the mist eliminator design to suit most applications.

For best performance, it is important to achieve uniform gas flow distribution and maximum effective area, and advice can be given on the most appropriate positioning, in terms of disengagement distances from vessel inlet, outlet and other vessel internals.

SIZING

For equipment based on direct and/or inertial interception, gas stream velocity affects all three principles involved in separation (impingement, coalescence and drainage). Flooding, or re-entrainment of liquid, can occur if the flow of gas prevents drainage, and the effective area of the mist eliminator is therefore established by determining an appropriate superficial velocity for the equipment. The overall performance of the mist eliminator is then a balance between efficiency and pressure drop.

= maximum superficial gas velocity (m/s)
= liquid density (kg/m3)
= gas density (kg/m3)
= a constant which is specific to the separation equipment and is a function of process parameters such as:
  • Liquid loading
     
  • Gas and liquid viscosity
     
  • Gas pressure
     
  • Surface tension


Derating factors are often applied to allow a safety margin for exceptional conditions such as liquid slugs and gas surges. For example, mesh mist eliminators should generally be designed with a velocity of 75% of V, to allow for surges and with a minimum velocity of 30% of V.