Separation of Phases Vapor + Liquid

Vapor-Liquid Separation Vapor and liquid volumes from thermodynamics Remove liquid drops from vapor, vapor bubbles from liquid Avoid foaming Key processes: –Gravity settling –Impingement

Gas Liquid Separators Vessel volume = time for settling Mesh pads = impingement

Gravity Settling Terminal settling velocity of droplets in vapor: C’=f(Re)

Souders-Brown Approximation K = factor for sizing separators Horizontal m/s Vertical 0.05 to 0.11 m/s Ulrich recommends K=0.06 m/s - use 1/2 of these values when no demisters Approximation for 125  m droplets:

Liquid/Liquid Separations Called decanters or coalescers Low terminal velocities due to small  Coalescence of droplets is important Typically design from time and L/D Horizontal to allow maximum interfacial area e.g. Hydrocarbon water min

Lecture Problem Gas-liquid and liquid-liquid separators are very common in the process industries. These vessels are given many different names, but they all operate on similar principles of gravity- driven fluid separation. What do the following vessels do? How much of each fluid phase (as a fraction of vessel volume) would be present in each at normal operation? Compressor knock-out drum Steam drum API Separator Reflux accumulator Slug catcher Steam trap Flash tank Fluid-Fluid Separators