Closed-Loop Identification at the Hovensa Refinery

The Hovensa refinery located in the US Virgin Islands is a joint venture between a subsidiary of Amerada Hess and a subsidiary of Petroleos de Venezuela, S.A. (PDVSA). The facility is one of the most modern refineries in the United States and, with crude oil processing capacity of 495,000 barrels per day (BPD), is one of the largest in the world. The latest round of MPC retesting at the refinery was completed in an automated fashion, stepping multiple independent variables simultaneously while the MPC controller was in service. The crude #6 MPC application has 34 MVs and 90 CVs covering two furnaces, an atmospheric tower and a naphtha stabilizer. During the plant test, an existing MPC controller is online and active in stabilizing the operation while the test program moved all the 33 MVs simultaneously. The duration of the closed-loop plant-test, model identification and review was only eight days. The plant test was found to be non-intrusive to the normal operation of the plant allowing the operators to concentrate on their normal duties. This paper describes the technology, its use on a large MPC application on the crude #6 unit and documents the results of the testing and modelling project.