Optimizing Oil Use during Pipeline Flushing and Changeover Operations

Pipeline flushing operations are vital for ensuring product integrity in multi-product petroleum facilities where different grades of petroleum products are transported using the same pipeline network. During product changeovers, pipelines must be thoroughly flushed to remove residual oil from previous batches. Traditional flushing methods, which involve using the next product as the flushing oil, generate commingled oils—a mixture of residual and flushing oils that do not meet the required product specifications. These oils are sold at a lower value, leading to high economic losses as petroleum facilities conduct thousands of flushes annually. Furthermore, emissions associated with these flushing operations contribute to environmental concerns due to limited repurposing and reuse. With the quantity of commingled oil produced across the industry, there is a critical need for more efficient flushing processes that lead to resource minimization while improving sustainability.

This research aims to address these challenges by introducing an optimized flushing process. To better understand the flushing dynamics, we explore two flushing operations of direct oil to oil displacement and an enhanced air blowing technique. The direct oil to oil displacement process involves the introduction of a moving plug of the flushing oil to displace the residual oil, thus an interplay of a two-oil system is produced. The enhanced air blowing technique involves partially displacing the residual oil using air, followed by introducing flushing oil to completely remove both the air pockets and the remaining residual oil. Optimal conditions of the air blowing technique in terms of air flowrate and duration of air blowing were attained through the design of experiments. The experiment analyzed the flushing dynamics between a transition from a higher to a lower viscosity product known as a step down and a transition from a lower to a higher viscosity product known as a step up. The product purity is determined through the monitoring of the instantaneous real-time viscosity during the flushing process as detected by an inline viscometer. With a data acquisition system seamlessly integrated, data from the experiment is collected and analyzed. The effectiveness of these two flushing operations is analyzed for optimal conditions of time and volume requirement to achieve product purity. These experiments were conducted using a pilot plant scaled down to 1/5th of a generic lubricant oil plant. The effectiveness of the pilot plant in simulating the operations at the industrial plant was validated through dimensionless residence time distribution (RTD) studies[1]. This study demonstrates how an industrial-scale pilot plant was used to explore and optimize flushing techniques during product changeovers involving oils of varying viscosities. The findings provide valuable insights for improving flushing operations at the industrial level, offering a scalable solution that promotes resource efficiency and sustainability.

References

[1] B. Gao et al., “Improved Design of Flushing Process for Multi-Product Pipelines,” presented at the Foundations of Computer-Aided Process Design, Breckenridge, Colorado, USA, Jul. 2024, pp. 137–144. doi: 10.69997/sct.171679.

Additional References:

1. Jerpoth, S. S.; Hesketh, R.; Slater, C. S.; Savelski, M. J.; Yenkie, K. M.* 2023 Strategic Optimization of the Flushing Operations in Lubricants Manufacturing and Packaging Facilities. ACS Omega, 8(41), 38288-38300.
2. Gao, B.; Slater, C. S.; Curtis, S.; Fracchiolla, M.; Theuma, D.; Roth, S.; Padros, E.; Yenkie, K. M.; Hesketh, R.P.*Enhancing efficiency and quality in oil pipeline flushing: a novel laboratory scale pilot plant study. Accepted to the 2024 ASEE Annual Conference, Portland, OR.
3. Jerpoth, S. S.; Hesketh, R.; Slater, C. S.; McClernan, R.; Savelski, M. J.; Yenkie, K. M.* Application of discretized non-linear programming to minimize mixed oil formation in flushing operations of lubricants pipelines. FOCAPO 2023 conference, January 8-12, 2023