Heat Requirement of a Column

The heat flow Q required to operate the column adiabatically is provided via the reboiler. A heat balance over the rectification column shown in Fig. 2-33, gives 

g p is the vaporization enthalpy referred to the pressure and composition Xp in the condenser. (If the amount of overhead vapor condensed is the same as the reflux to the column, the condenser acts as a dephlegmator. The dephlegmator and the additional condenser/cooler required to condense and subcool the overhead product E must be included in the heat balance.) 

Heat losses Qy from the rectification unit depend on the type and thickness of the insulation material. The reflux is increased by heat losses from the rectification column by a so-called wild reflux . These unavoidable heat losses relaxe the concept of adiabatic operation. 

Vapor flow at the top of the enriching column above the enriching tray or above the 

Enthalpy of the feed mixture F at the feed and boiling states, respectively Ah, g Vaporization enthalpy of the feed mixture yA,oi Molar fraction of LS in G  

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