Sujendran Suppiah - Petronas - Melaka Refinery
The Delayed Coker of PETRONAS Penapisan Melaka consists of a two-drum Coker with a design capacity of 29.5 kbpd and has been in service for more than 15 years. Because of extremely volatile oil refining margins, refineries are having difficulties reaching consensus about where profitability is heading over the next five to 10 years. With a desire to continuously increase our profits, we have pushed our Coker to its limit towards upgrading the bottom of the barrel to valuable lighter product(s). This constant pushing resulted into extreme high temperature during normal operation and cooling during the quenching process, thus impacting the material integrity of the drums.
In 2019, we observed significant bulging and sharpness (inwards and outwards) at the third and fourth weldment of the coke drums. We studied the patterns of existing quenching use during the whole life of the drums, and it was determined to be quite aggressive in the beginning. Currently there are no temperature instruments installed at the drums to monitor the temperature gradients during the quenching process. We adopted new automation designed to replace the traditional quench methodology. The objectives were to minimize the thermal effects during drum quenching; calculate the best quenching flow sequence (to minimize temperature rate of change at every drum switch) by using QILC (Quadratic Iterative Learning Control) Approach and hence prolong the drum life-span by minimizing the cracking rate at the early onset of quenching.
Iterative Learning Control (ILC) is a control technique originally proposed for systems that repetitively perform the same task. It improves the set point tracking accuracy progressively through repetitive learning. In simple words, ILC will try to minimize error from previous results versus the reference profile that we want. Since quenching activity in cokers is a repetitive event , QILC is among the best solutions rather than the normal ramping methodology that had been used for years.
The rate of change of temperature had improved from 3.1 degC/min to 1.07 degC/min. This effort helps in assisting the material integrity, essentially prolonging the life of the drums and avoiding ULPO Cost of repairing the drums , costing millions of RM.
Essentially, the new automation for quenching is significantly useful in assisting boardman(s) daily tasks of performing the quenching activity and in tandem, supporting the safety precautions to operate the plant.
Siti Sarah joined Malaysian Refining Company Sdn BHd in 2014. She is responsible for APC applications in the CDU-2 ,VDU-2 Reformer Unit, Lube Complex & Delayed Coker. In the lube plant she is in charge of the Exapilot Expert System controlling Lube Plant Grade. She also participates in a new initiative for Operational Excellence to improve Plant Conditions. Before her Melaka assignment she was responsible for APC in an LNG plant.
Siti Hazirah binti Mohd Aini graduated from Vanderbilt University, USA in Chemical Engineering in 2011 and joined Malaysian Refining Company Sdn. Bhd in 2012 as an assistant operation engineer in the Production department. In 2014, she joined the Technology department as a process technologist for Hydrogen Production Units and has been involved in multiple turnarounds and improvement projects for HPUs. She is now a process technologist for the Delayed Coker Unit.