Plantwide Control of Two Stage Desalting Process for Feed Rate and Grade Disturbances

The control of crude oil desalting operation in a desalter, especially for the oil-water level control is critical for safe operation. The problem is particularly severe in two-stage desalter, wherein the brine stream from second stage desalter is recycled to first stage desalter. In this work, a dynamic model for the process comprising a kettle and two desalting units is developed. The two control structures are proposed which are differentiated based on the adopted level control strategy. The first control structure is combined with override controllers for increasing the flexibility of process operation with respect to feed rate and grade disturbances. A supervisory layer consisting of two advisory controllers is proposed, which provides the manipulation for manually operated mix valves in the process.