Question

Define residence time and briefly explain why liquid-liquid separators residence time is larger than the gas-liquid separators.

Answer 1

Residence time is the volume per unit volumetric flow rate or it's ratio of volume to volumetric flow rate or in simple words it's time spent by the molecules inside the reactor (here separator).

Liquid-liquid separators- separation of both the liquids will be on the basis of density difference. So higher density liquid will be on the top layer and lower density liquid will be in the bottom layer.

gas-liquid separators: separators used to separate water droplets or vapor from liquid stream, it basically works on gravity. Cyclone separator is commonly used gas-liquid separator.

In liquid-liquid separator at interface of both liquids means smallest particle of higher density liquid and largest particle of lower density fluid and it's difficult to separate, so the particles will be inside the separator for the longer time (means higher residence time) whereas in gas-liquid separator due to gravity liquid particles will be collected at bottom and gas particles at top means separation will be faster or molecules will be inside the reactor for a shorter time so lower the residence time.