PTQ Q2 2022 Issue

Digital twin optimises FCC operations for real separator behaviour Digital twins based on process simulationmodels are invaluable for overcoming limitations in the design or operations phases to optimise plant profitability


S eparation processes play a crucial role in the oil and gas upstream, midstream, and downstream sectors. For exam- ple, in refineries, the overhead ves - sels and the crude distillation and vacuum distillation units separate hydrocarbon reflux from sour water and overhead vapours. In many cases, excessive liquid carry-over influences product quality or yield. To assure appropriate product yields, treatment and conversion units employ two- and three-phase separation processes critical to proper operation of such units. Other important separators include the compressor suction scrubbers or knock-out (K.O.) drums. The proper design of these devices is necessary to ensure the operational integrity of the com - pressors. Common concerns include excessive carry-over and large drop - let size in the suction gas. Often, droplet size criteria are met while the flow rate of liquid carry-over is excessive or vice versa. In most oil companies and engi- neering, procurement and construc- tion (EPC) contractors, separation expertise is either limited or absent. Therefore, in the design phase of new facilities, oil companies and EPC contractors rely heavily on ven - dors for vessel sizing and/or vessel performance estimates. Additionally, the industry traditionally lacks uni- fied separation vessel design prac - tices. As a result, the design and sizing of vessels rely on various tra - ditional in-house standards, rules-of- thumb, and disparate ‘spreadsheet tools’. Frequently, in-house tools provide criteria based sizing of ves - sels and internals, but cannot predict

carry-over performance. This means engineers can produce designs with- out appreciating the extent to which the separation equipment will fulfil its purpose. On the one hand, ves - sels may be oversized. On the other hand, they may have insufficient capacity to handle off-design condi - tions or process upgrades. Software tools Due to the complexity of many oil and gas process operations, insight- ful engineering teams are keenly aware that an appropriate digital twin is vital to achieving key busi - ness objectives, including: • Improve profitability with assured ROI by increasing operating margins while reducing expenses • Better facility management, pro - duction planning, and decision making from a holistic view of facil - ity performance • Meet and enhance unit produc- tion targets through continuous process unit monitoring • Identify system bottlenecks and major operational risks • Devise possible debottlenecking strategies with corrective actions Process simulation provides a powerful platform for designing, monitoring, and optimising refin - ery and petrochemical operations. Recent developments in simula - tion technology have improved the accuracy and user-friendliness of these tools. The Petro-SIM process simulator is well suited to building digital twins because it provides meaningful data regarding the effi - ciency and effectiveness of plant operations at an asset level. In addition, MySep software is adept at simulating the perfor -

mance of separation equipment. For design, the software guides engineers to follow sound practices to assure performance. For evaluat - ing existing equipment, it brings to bear proprietary incremental mod- elling to predictions of carry-over. KBC and MySep have partnered to combine the strength of Petro- SIM’s process simulation with MySep’s rigorous separator model- ling. The combination of these tools help operators mitigate risks and optimise operations to ensure the following: • Efficiency : They provide a com - plete detailed representation of the plant to assess the interactions between various units and asset groups • Accuracy : They use rigorous thermodynamic packages and research-validated ratings. The model predictions can be used with confidence, even when extrapolat - ing them to new conditions and feedstocks • Better decision-making : Petro- SIM’s time series function enables process engineers to run a series of steady-state simulations and observe the long-term impact on operations • Cost savings : Engineering, oper - ations, training, planning, and cap- ital improvement projects use one model. All key stakeholders use the same technology to streamline work processes Case study In a refinery FCC unit, reactor prod - ucts enter the main fractionation column (MFC). The side stripper on the MFC produces heavy naphtha and light cycle oil. Then, light gas-

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