CO2 transport

Captured CO2 must be transported from the points of capture to the storage sites. This task provides knowledge and methods to ensure that the transport is safe and efficient, performing in-depth investigations into running-ductile fractures in CO pipelines, ship transport, and impurities and non-equilibrium flows of CO.
Svend Tollak Munkejord
Task leader: Svend Tollak Munkejord

Results 2021

How CO₂ flows through restrictions

For the design and operation of CO2 processing plants and transportation systems, engineers need to estimate the flow rates through restrictions such as control and safety valves. If the pressure drop across the restriction is high enough, the flow will become choked, i.e. it will attain a value that will not increase if the pressure drop increases. There is a need to develop and validate models that are generic enough to be implemented in simulation tools for CCS applications such as pipes and vessels. To amend the situation, we have performed experiments in the ECCSEL depressurization facility using two sizes of nozzles and orifices (see the figures). We have also proposed a delayed homogeneous depressurization model to account for some of the non-equilibrium phenomena occurring in the flow through the restriction. The results were encouraging, as the model provided very good predictions of literature data for flow through a converging-diverging nozzle for relatively high temperatures. However, we need to work more to describe the low-temperature case.

Model to predict running-ductile fractures in CO₂ pipelines​

We are working to improve our ability to predict running-ductile fractures in CO2 pipelines. The work has progressed along three main lines of research.

The first is to improve methods for describing the steel and crack behaviour in a finite-element modelling framework, including the consistent calibration of model parameters based on limited input from material tests. The second line of research is to describe the pressure load on the pipe walls from the escaping CO2, properly taking non-equilibrium effects into account (see also the previous paragraph). The third line of research is to “distil” the knowledge obtained into an engineering tool.

We have previously assessed pipeline designs for the Northern Lights project. This year we wrote an update of this work together with Equinor, which will be presented at the TFAP Conference in March 2022.

Photo of a nozzle
A converging 12.7 mm nozzle screwed into the depressurization tube.
Scientific illustration
Pressure measured at a position 8 cm from the outlet of the depressurization tube. It can be observed that decreasing restriction diameter gives a higher pressure (and therefore lower mass-flow rate). An orifice gives a higher pressure and lower mass-flow rate than a nozzle.

Educating the next generation of CCS scientists

This year, we co-supervised a master’s candidate from the Department of Structural Engineering at NTNU on modelling ductile fracture in steel structures. Our two PhD candidates who work on the topic of fracture mechanics related to fracture-propagation control in pipes, and on the topic of depressurization of CO₂ in pipes, have both successfully completed their first year. Both candidates are co-supervised by NTNU and SINTEF.