APC - Visbreaking
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 decokings. As a process licensor and an advanced control technology supplier, Axens combines all the necessary expertise for successful Visbreaking APC projects.
A four- step strategy is implemented
- 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.
- 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%