Before APC, StdDev = 4.7
After APC, StdDev = 1.7
Figure 2 Comparison of regenerator bed temperature with and without APC control. Graphs generated by RaddicalView V.2020(168).
significantly when the unit feed rate and composition sta - bilise. Optimising the slide valve is geared towards maxim - ising its use within riser temperature limits or associated RTO setpoints. For the regenerator bed temperature, PACE dynamically adjusts the pure oxygen flow controller, mini - mising it until the bed temperature reaches its low limit or the real-time optimisation target. Similar precision is also observed in other critical parameters, including: • Tighter control over the CO heater oxygen and maximum CO limits. Tightly regulating the heater outlet temperature by optimising fuel gas flow to the heater ensures optimal operational efficiency and safety. • Precise regulation of the combustion air flow controller to maintain the minimum furnace stack oxygen levels. The system consistently maintains oxygen levels within pre - scribed limits to effectively manage fluctuations in airflow, ensure optimal combustion efficiency, and maximise the efficiency of the regeneration process. The control system is essential for maintaining the regen - erator bed temperature within a narrow range, significantly reducing the standard deviation from 4.7 to 1.7. By dynam - ically adjusting parameters such as pure oxygen flow and total regenerator air flow, the system optimises regenerator efficiency and maintains safety. Optimising product yields and quality To optimise product yields in the FCC unit, the MFRAC sec - tion focuses on maintaining the operational integrity of the column, particularly by preventing flooding and ensuring that critical levels associated with side draws are consist - ently maintained. One key aspect of optimising product yields in the FCC
unit is composition control. The naphtha final boiling point of the top side draw is a factor that determines the overall optimisation of the unit to produce the optimal yield of the product. Maximising the second side draw, which typically con - sists of LCO, is another important aspect in optimising product yields in the FCC unit. Adjusting LCO production, such as flow rate or temperature adjustments, allows the FCC unit to maximise LCO yield without exceeding its com - position limitations of 90% and 10%. Previously, naphtha final boiling point was not consid - ered a controlled variable in APCs. However, incorporating the final boiling point as a key optimisation variable, APC objectives now align with the refinery’s economic and scheduling priorities. Figure 3 illustrates the impact of APC control on the final boiling point, highlighting this alignment with plant objec - tives. Compared to the previous SMOC and absence of APC, PACE’s performance is excellent, reducing the stand - ard deviation by 1.2. This improvement is due to the tighter control of the final boiling point and reduced fluctuation in naphtha draw. Maximising economic performance Implementing PACE technology’s revamped economic function has helped optimise the Deer Park refinery’s eco - nomic performance. By strategically assigning different response speeds to different sections of the process, PACE effectively manages critical constraints to ensure the refin - ery operates to maximise its profit margins. The economic function operates via two distinct opera - tions: the reactor regenerator and main fractionator. The
No APC, StdDev = 1.54
SMOC Control, StdDev = 0.48
PACE Control, StdDev = 0.34
Figure 3 Impact of APC control. Graphs generated by RaddicalView V.2020 (168)
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PTQ Q4 2024
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