Technology qualification of low-pressure CO₂ ship transportation

Background
Carbon capture and storage (CCS) will be a key technology to meet the goals of the Paris and Glasgow agreements. Although the technologies and the industry are very much still emerging, a possible challenge is connecting capture sources to facilities for use or storage sites, especially where pipelines are not an option due to combination of transport distance and volumes. As a result, it is expected that CO₂ ship transport technology will be needed if large quantities are to be safely transported at costs that are commercially viable.

Shipping of liquified CO₂ already takes place, although at a limited scale and exclusively for commercial trade (food and beverage, cleaning, chemical). Liquid CO₂ is currently transported on ships as a semi-refrigerated under pressure, similarly as for other gases (e.g., propane, butane, etc.). At this so-called medium-pressure condition, carbon dioxide is transported in liquid state at pressure in the range of 15 to 18 barg and a temperature of approximately -21 to -26 °C. Current ship maximum cargo capacities for medium-pressure condition are in the range of 7500 m3. Alternatively, pipeline could be used to transport carbon dioxide in dense (liquid) phase at ambient temperature and pressure typically above 100 barg or gas phase at ambient temperature up so a pressure of approximately 35 barg.

For a large-scale value chain, a development towards larger transport volumes per ship is foreseen, also to enable offshore cargo transfer for direct injection. This is expected to benefit from reduced tank pressure, denoted low-pressure. At low-pressure, the carbon dioxide is foreseen to be transported at tank pressure in range of 6 to 7 barg and corresponding liquid temperatures in range of -46 to -49 °C. The reduced pressure and temperature allow for larger cargo tank diameter and also benefit from increased product (liquid) mass density, hence increased cargo capacity per ship. Considering both investment and operating cost, increased ship cargo capacities is foreseen to enable a reduction in overall transport cost.

Besides the increased ship tank size and cargo volumes, a low-pressure condition will also have technical and commercial implications for the entire transport value chain with regards to conditioning of product for transport, loading and offloading operations and intermediate storage of product.

The potential challenge with respect to the lower pressure is the operation in the proximity to the triple point for CO₂. At the triple point, the CO₂ can be present in either solid (dry ice), liquid and gas state. The solid state is perceived as a challenge with regards to operability within the value chain. There is currently no industry experience with large scale low-pressure CO₂ ship transport.

Objective
DNV AS on the behalf of the consortium composed by Equinor Energy AS, Gassco AS, TotalEnergies EP Norge AS and Shell is leading a Technology Qualification Programme for low-pressure CO₂ ship transportation concept.

The objective of the Technology Qualification of the low-pressure CO₂ ship transportation is to provide evidence of the technical feasibility of a low-pressure CO₂ ship transportation concept, mitigating the risks and removing uncertainties related to design, construction, and operation through the execution of the Technology Qualification Programme, as described in, DNV-RP-A203,

Activities
The study was divided in two phases: planning phase and execution phase. The objective of the planning phase, executed from to Q2 to Q4 2020 and financed by the Partners, was to identify technical uncertainties and to establish relevant qualification activities to address the risks and uncertainties. Next, through the technology and threat assessment, novel technology elements and associated risks and uncertainties were identified and ranked and the necessary qualification activities to de-risk the concept were defined.

The qualification activities were carried out in the execution phase from Q3 2021 to Q1 2024 financed by the partners and Climit programme. The activities included:

Conceptual design of a conditioning and liquefaction plant and experimental demonstration of the liquefaction at low-pressure

Basic ship concept design of an appropriate and efficient dedicated CO₂ carrier and cargo handling system to accommodate and handle large volume of CO₂ ( ̴ 30 000 m3)

Design of the cargo containment system and qualification of selected material to accommodate the large cargo weight, ensure constructability and operation for design temperature at -55 °C.

Investigate, by executing experimental activities, the operability of a low-pressure system in proximity to the triple point and determine a safe envelope for the operation as well as demonstrate ability to deal with eventual dry ice formation.

Simulation tools for assessing of cargo handling and operations, interaction with the loading and offloading onshore facilitates and benchmarking of process simulation tools.

Experimental and modelling work within CO₂ thermodynamics to reduce the uncertainty in software design tools

Achievement
The results of the qualification activities have been deemed sufficient to confirm that there are no technical obstacles preventing the implementation of a low-pressure CO₂ ship transport value chain. This indicates that the technology is ready for initial use. However, it is recognized that there are still technical issues that need to be addressed during the specific development and execution of projects.

Additionally, some findings from the activities carried out under the CETO Joint Industry Project (JIP) have been published and made available to the industry.

It’s important to note that while the technology is considered ready for first use, ongoing attention to remaining technical issues is crucial for the successful development and execution of specific projects. The sharing of findings with the industry also helps in advancing the collective knowledge and addressing any potential challenges in the implementation of this technology.

Future plans
The partners are currently in dialogue to execute additionalactivities related to the low pressure value chain, such as:

Further investigate potential material suitable for low-temperature application. The activities shall address production and welding technology to identify cost-efficient material and achievable design temperatures.

Evaluate the feasibility, benefits, and technical barriers with the use of a re-liquefaction plant on board of low-pressure CO₂ carriers. The re-liquification plant will actively allow to control the pressure increase during voyage and hence allow for optimization of the design pressure for the cargo containment system.

Further investigate the solubility limit of different trace components, including acid produced by chemical reactions at low pressure condition.

Investigate chemical reactions between trace components at low pressure condition and implication with respect to corrosion at low-pressure condition.

Determine a suitable LP CO₂ product specification. The task may include an analysis to balance the cost for lowering the level of impurities with benefits of reduced corrosivity.

List of publications:

GHGT16 Proceedings, CETO: Technology Qualification of Low-Pressure CO₂ Ship Transport; Gabriele Notaro, Jed Belgaroui, Knut Maråk, Roe Tverrå, Steve Burthom, Erik Mathias Sørhaug. 16th Greenhouse Gas Control Technologies Conference, Lyon 23-27 October 2022

Michael Drescher, Adil Fahmi, Didier Jamois, Christophe Proust, Esteban Marques-Riquelme, Jed Belgaroui, Leyla Teberikler, Alexandre Laruelle. “Blowdown of CO₂ vessels at low and medium pressure conditions: Experiments and simulations” 0957-5820/© 2023 Institution of Chemical Engineers. Published by Elsevier Ltd.

GHGT16 Proceedings, Poster presentation, BLOWDOWN OF CO₂ VESSELS AT LOW AND MEDIUM PRESSURE CONDITIONS: EXPERIMENTS AND SIMULATIONS; Michael Drescher, Adil Fahmi , Didier Jamois , Christophe Proust , Esteban Marques-Riquelme, Jed Belgaroui, Leyla Teberikler, Alexandre Laruelle. 16th Greenhouse Gas Control Technologies Conference, Lyon 23-27 October 2022

Rod Burgass, Antonin Chapoy “Dehydration requirements for CO₂ and impure CO₂ for ship transport” , Fluid Phase Equilibria. Volume 572, September 2023, 113830

Antonin Chapoy, Pezhman Ahmadi, Rod Burgass “Direct Measurement of Hydrate Equilibrium Temperature in CO₂and CO₂ Rich Fluids with Low Water Content”, Fluid Phase Equilibria Volume 581, June 2024, 114063

Franklin Okoro, Antonin Chapoy, Pezhman Ahmadi, Rod Burgass “Effects of non-condensable CCUS impurities (CH4, O2, Ar and N2) on the saturation properties (bubble points) of CO₂-rich binary systems at low temperatures (228.15–273.15 K)” Greenhouse Gases: Science & Technology, 26 December 2023