Distillation Tower Energy Efficiency Improved by Advanced Control Techniques

A 43.65 MMBTU/HR energy reduction was achieved in the co-product recovery distillation section of Beaumont Chemical Plant via improvements in constrained multi-variable control. Various novel techniques were employed in order to improve the energy efficiency of the distillation towers:

• Reduction of multiple tower refluxes via tighter control at upper thresholds on tower overhead key component concentrations.  This task involved deployment of inferential quality estimators (where analyzers were absent) with a feedback enforced via lab samples. 
• Employing tray analyzer prediction-error feed-forwards for tighter control of distillate purity on long time-to-steady-state towers
• Recycle stream flow was reduced by more than 50% while optimizing tower weeping and reboiler constraints on the first tower in co-product recovery train, 

These activities resulted in a 43.65 MMBTU/HR reduction in combined reboiler duties, which is equivalent to ~35.7% of total energy utilization by all distillation towers in co-product recovery section. An associated reduction of 4,432 Tons of Annualized net CO2 emissions were also realized.