Park refinery was crucial to achieving value. APC systems, such as PACE, have proven to enhance operator efficiency, tighten control over critical parameters, optimise product yields and quality, and maximise economic performance. Key benefits that the refinery realised included: • Enhancing operator efficiency
React regn.
Main frac.
CO heater
Reactor separator & stripper
Riser
Main frac.
• Tighter control over critical parameters • Optimising product yields and quality. Enhancing operator efficiency
Regenerator
Figure 1 Overview of the FCC unit
One key benefit of PACE technology is its ability to improve operator efficiency. By integrating all three components – SMOC-RQE-RTO – into a unified interface, operators can get status updates and streamline their workflows. This sin - gle interface manages operating limits and enhances APC functionality to transform unit optimisation through refined modelling and tuning. This results in simplified activation, deactivation, and fine-tuning of operational parameters. Some of the key handles from the R&R, such as feed rate and riser temperature, are linked to the main fractionator compositions as predictions. Alternatively, WGC suction pressure in R&R can be used as a handle for MFRAC over- head pressure constraint. The MFRAC manipulated variable (MV) handles have been reorganised and fine-tuned to ensure that specific con - straints are managed by the appropriate handles. For exam - ple, when the inferential HCO 95% exceeds its upper limit: • First, reduce the slurry reflux return temperature. • If further temperature reduction is not feasible, increase the slurry reflux flow. It is important to note that HCO and LCO MVs are no longer directly applied in this control strategy. Instead, their effects on HCO 95% have been integrated into a predictive model. The technology aligns the controlled variables with real- time optimisation setpoints and optimises online LCO and naphtha analyser compositions. Significant enhancements include tighter control over critical parameters within the R&R controller, including CO heater outlet temperature, excess oxygen levels, regenerator bed delta temperature, and riser temperature. Tighter control over critical parameters Effectively managing the regenerator temperature in an FCC unit is necessary to optimise refinery operations. By minimising temperature variations, overall efficiency and performance can be improved. Several factors that influ - ence the regenerator temperature include operating condi- tions, catalyst activity, and feed qualities. The impact of effective temperature management can be seen in Figure 2 , which compares the regenerator bed tem- perature with and without APC control. The graph depicts a scale of 30°F for regenerator temperature. On the left side, the conditions without APC control show a standard deviation of 4.7, indicating significant temperature fluctua - tions. On the right side, the results under APC closed-loop regulation demonstrate a standard deviation of 1.7, illus- trating the tight control achieved through APC technology, even under varying operational conditions. Without APC, the riser temperature can vary
• The third loop is dedicated to the depropaniser (DC3) and debutaniser (DC4) columns. This intricate control framework, with more than 25 manipulated variables and 71 controlled variables, works in tandem to form the foundation of the refinery’s operations to improve performance. An overview of the FCC unit is shown in Figure 1 . Reactor regenerator and main fractionator structure This APC system consists of one application with two sub - controllers, which are responsible for managing the reactor regenerator, as well as the main fractionator in the FCC unit. The APC system uses five circulating reflux streams to control the main heat removal and product endpoints on the main fractionator. The R&R subcontroller’s main purpose is to manage the combined carbon monoxide (CO) boiler and feed preheater, riser, reactor, and regenerator components to ensure these elements operate efficiently and effectively. Effectively managing regenerator temperature in an FCC unit is necessary to optimise refinery operations. By minimising temperature variations, efficiency and performance can be improved Meanwhile, the MFRAC subcontroller focuses on sepa- rating the hydrocarbon vapour from the overhead reactor into individual product streams. Each product stream is then directed to its respective destination for further refine - ment or blending into valuable liquid fuels as follows: • Wet gas is compressed by the wet gas compressor and sent to the gas fractionator unit. • Naphtha, Light cycle oil (LCO), heavy cycle oil (HCO) and slurry are routed to their final destinations for further processing. This comprehensive control structure, with its ability to manage many different manipulated and controlled varia - bles, has been instrumental in optimising unit throughput and producing high-value products such as gasoline, light olefins, and diesel fuels. Efficient management of the various systems at Deer
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PTQ Q4 2024
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