The Visbreaking advanced control package combines Axens' latest generation multivariable controller MVAC, in association with a Stability Model (and P-Value analyzer) and fractionation inferentials; it is designed to maximize the cycle length of Visbreaking unit between two consecutive air decoking.
As process licensor and advanced control technology supplier, Axens combines all the necessary expertise for successful Visbreaking APC projects.
A 4 step strategy
- Stability estimation - Severity maximization under stability constraint - Optimization of fractionator operation: Adjustment of product draw(s) and pumparound(s) to ensure adequate heat removal, and desired product quality and separation. - Feed rate maximization, subject to furnace, soaker and tower constraints
Residue analyzer – Stability Model
Axens recommends the use of a “Peptization value” analyzer (from PORLA) in the fractionation residue, to calibrate the Stability Model. If analyzer readings are continuously available on-line, they can be directly used by the MVAC controller.
Benefits
- Constant and optimized conversion. - Stable residue, without asphaltene precipitation. - Reduction of furnace coking risk. - Maximization of cycle length between two air decoking. 10% to 50% - Consistent quality of valuable products. - Increased distillate yield. 1% to 2% - Increased throughput. 2% to 3%
