Question

Why reboiler partial evaporised feed not totally?

Answer 1

For any distillation column, if you consider it to be a car, then the reboiler is its engine . Now as without an engine a car can't run. So, is the case with a distillation column. The function of a reboiler is to supply heat to column bottom so as to generate the desired vapour traffic within the column. But in case of crude distillation column, entire vaporisation upto a particular percentage of the crude throughput is achieved within the furnace/heater that precedes the column. The column employs stripping steam and the percentage of vaporisation achieved in the furnace lies in the range of 55–60 percent depending of the crude being processed, overflash requirement and distillate yield . Now in case of typical reboilers the percentage of vaporisation is small about 10–15 percent. This extent of vaporisation can't drive a crude distillation column.