Optimal pipeline design for CCS projects with anticipated increasing CO2 flow rates

• Developed an equation to evaluate whether an oversized pipeline should be used.
• Developed a design equation for the oversized pipeline diameter.
• Oversized pipelines are more economical for shorter pipeline lengths.
• Oversized pipelines are less economical for larger flow rate changes.
• A larger gap between two flow rates will make oversized design less economical.

Large-scale CCS projects with multiple CO2 sources will require large investments. Optimising the pipeline network design for cost reduction has been proposed as a potential way to reduce overall CCS costs. This paper presents a two-step methodology for the optimal design of on-shore pipelines with a projected increase in CO2 flow rate. The first step involves determining whether an oversized design is preferable over a duplicate pipeline design, on the basis of the levelised CO2 transport cost. This is performed through a simple correlation that depends on key parameters including the length of the pipeline, the timing and magnitude of the flow increase. If the oversized design is preferred, the second step of the proposed method determines the optimal diameter for the oversized pipeline. The approach, based on modelling of a wide range of generic cases, provides a two-step method to quickly verify whether an oversized pipeline is necessary, to assess the costs of using an oversized design against those of building duplicate pipelines, and to identify the pipeline design that minimises levelised cost of CO2 transport. A sensitivity analysis shows that the correlations are applicable for a wide-range of values for flow rate, transport distance, discount rate, steel price, booster pump and electricity costs. In addition, the correlations for pipeline cost and optimal diameter developed in this paper can be integrated into and accelerate the existing large scale, staged CO2 pipeline network optimisation models.