“Linking UOP models with Honeywell’s Profit® Controller allowed us to embed valuable process knowledge into our advanced control strategies.”
Kamrul Arrifin, Process Control Group Leader, PP(T)SB
Malaysia’s PETRONAS Penapisan Sdn Bhd plant in Kerith, known as PP(T)SB, contracted Honeywell to implement complex-wide advanced process control (APC) to help maximize production of paraxylene and maintain product quality. Honeywell implemented a series of advanced control applications across the complex, resulting in a 2.5 percent increase in overall aromatics production and a reduction in energy consumption.
The PP(T)SB aromatics complex processes naphtha condensate from two condensate feeds before passing it through a series of unit operations to produce paraxylene and benzene. The front-end process is similar to naphtha processing in a refinery – distillation, hydrotreating and naphtha reforming. The back-end process involves aromatics separation from non-aromatics followed by high purity distillation and aromatics upgrading through isomerization.
The units are closely linked together even though there is some intermediate strorage, which means that feed or feed composition changes upstream affect the operation of units downstream. Furthermore, disturbances such as changes in pressure could have a significant effect on the operation of high purity towers where constraints in the overall complex may appear.
PP(T)SB appreciated that Honeywell’s APC technology could help maintain product quality. The company also felt that by designing the APC strategies early, they would reduce costs by ensuring the correct instrumentation was in place as the unit was being constructed.
Honeywell completed the initial designs, including regulatory controls, initial APC design, operator interface and UOP module interface, before the plant was completed. The plant’s DCS platform was not a Honeywell system so Honeywell and PP(T)SB
PP(T)SB Aromatics Complex in Kerith
designed and implemented custom graphics for operator interaction with the advanced control applications.
Honeywell used its extensive expertise to implement multivariable control solutions using Profit Controller on each of the units in the aromatics complex. By working with UOP, Honeywell incorporated UOP process models into the Profit Controller applications. A total of 12 Profit Controller applications were implemented as well as several UOP process models providing either inputs as controlled variables or setting the limits for a particular variable within the controller.
The Profit Controller applications had to be designed to handle the interaction between the units. Once the whole complex was operational, it became clear that some key control objectives would have a big effect on the overall throughput.
PETRONAS Increases Aromatics Production with Honeywell’s Advanced Process Control 2
The complete APC solution was implemented over two phases. The front end of the plant up to and including the reformer applied APC first, and about a year later, APC was applied to the remainder of the units.
Operations maximized C9s into one unit by maximizing the heavy naphtha cut and making sure that there was enough hydrogen produced in the reformer. Good quality control in the Sulfolane unit meant smaller losses of aromatics to raffinate stream.
The UOP Platformer directly controlled the percentage of aromatics while honoring constraints such as reactor tube metal temperatures and maintaining the desired coke on catalyst to ensure that the regenerator was not overloaded.
The incorporation of a column profile predictor helped stabilize operation in the high purity columns.
Profit Controller handled these disturbances very well and enabled plant staff to achieve a stable operation throughout the complex and increase production of aromatics by 2.5 percent.
"We are seeing the benefit from the APC program within two years of plant start-up which has considerably increased the complex profitability and provided a focal point for plant improvement," said Kamrul Arrifin, Process Control Group Leader, PP(T)SB.