Cryogenic separation recovery step

A sharp separation results in two high purity, high recovery product streams. No restrictions ate placed on the mole fractions of the components to be separated. A separation is considered to be sharp if the ratio of flow rates of a key component in the two products is >10. The separation methods that can potentially obtain a sharp separation in a single step ate physical absorption, molecular sieve adsorption, equiHbrium adsorption, and cryogenic distillation. Chemical absorption is often used to achieve sharp separations, but is generally limited to situations in which the components to be removed ate present in low concentrations. 

Low-pressure operation presents the drawback of incomplete recovery by flashing of liquefiable products such as propane and butanes, which are partly lost in the purge. These loses can be reduced by a supplementary separation step (absorption or cryogenics). 

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