Techno-economic feasibility evaluation framework for reverse-flow retrofitting in multi -product pipelines aimed at benefit augmentation

As China's energy transition advances, optimizing flow direction in multi-product pipelines becomes critical to accommodate structural shifts in oil consumption, particularly reverse-flow operations. Normally, pipelines adopt a large-to-small diameter design to match declining flowrates, but reverse-flow disrupts this arrangement, leading to a substantial drop in transport capacity, the reconstruction of pressure and contamination control strategies. Therefore, this paper proposes an economic evaluation framework for the reverse-flow multi-product pipelines. Based on pipeline flowrate constraints, a model is constructed, with a flowrate interval expansion factor introduced to retrofit pipe segments and enhance reverse-flow capacity. Within the model, the nonlinear flowrate-pipe diameter relationship is addressed via piecewise linearization, while a correction method minimizes approximation errors. Taking a pipeline as a case study, the sensitivity analysis of factors impacting the economic performance of renovation project is conducted. The results show, ⅰ) minor renovations increase transport capacity of reverse-flow by 39% measured by total turnover volume. ⅱ) The net benefit of renovation project is most sensitive to unit price of pipeline transportation, which the investment becomes viable when unit price of pipeline transportation exceeds 0.1755 CNY/(t⋅km). ⅲ) Compared with the normal rule, the proposed framework increases transportation revenue by 19.97%–20.29%. ⅳ) Compared with the pre-renovation condition, the potential for economic benefit growth ranging from approximately 27.93% to 31.21%. ⅴ) When model parameters such as flowrate interval expansion factor and economic velocity fall within reasonable ranges, the renovation scheme is valid. This study optimizes reverse-flow capacity through multi-modal control strategies and corrects the diameter of pipe segments, enhancing operational flexibility and efficiency in pipeline networks and providing a cost-optimized renovation solution for pipe segments. Future studies should prioritize real-time updating and feedback mechanisms for pipeline capacity during flow-direction optimization.