Objectives are to maximize the production of more valuable products, minimize energy consumption, operate in safe and stable conditions and minimize the effects of crude change.
This application uses MVAC, Axens' multivariable predictive controller from latest generation, in association with inferentials and cutpoint technology.
A seven-step strategy
* dynamic estimation of the True Boiling Point (TBP) curve of the crude using heat and mass balance around the crude unit ; to improve control, temperatures are compensated for partial pressure effect * side stream cutpoint calculation (using estimated TBP) * product quality estimation using on-line analyzer, inferred properties or a combination * adjustment of product draws, pumparounds, furnace and top temperatures to maximize higher value, on-specification products, even during crude switch. * adjustment of pumparounds to ensure adequate heat removal, maximum heat recovery and desired product separation, subject to loading constraints * feed maximization, subject to furnace and tower constraints (flooding,…) , even during crude switch * pressure minimization
Benefits
* better yields * consistent quality of valuable products * substantial reduction of duration and magnitude of disturbances generated by crude switch * increased throughputt * better energy use
