Debottlenecking Low Pressure Fractionating Towers

Ancillary units also have room for debottlenecking. For this example, we will use an aromatics recovery unit although the discussion is applicable to any low pressure tower. The extraction section can often be pushed beyond the normal design rates by running at a lower solvent to feed ratio. The downstream towers may then become limiting. In any low pressure tower, the raising the tower pressure may significantly unload the trays and overhead condenser. The reboiler load will increase, but may not become a limit, especially if it is a steam reboiler. Raising the tower pressure can increase the tower capacity in the range of 5-10%.