Ship Design for CO2 Transport - Purpose Made or Multigas Carrier?

Abstract

Carbon Capture and Storage is addressed by IEA as one of the key technologies in a scenario where net zero CO2 emissions is reached by 2050 (NZE) and thus limiting the rise in global temperature to 1.5°C. In the NZE, 1.6 gigatons/y CO2 will be captured by 2030, ramping up to 7.6 gigatons/y in 2050, This will require huge logistic operations. The CO2LOS I-III projects investigate CO2 transport by ships and have found that where feasible with respect to harbour conditions etc, a limited number of large ships tend to be more cost effective than several small, also when the cost of intermediate storage in both ends of the logistics values chain is included. According to the work done, large ships will also provide improved regularity in harsh sea environment, and this is particularly important for offshore unloading. In the previous work of CO2LOS, we have mainly focused on ships up to 10 000 t CO2, for short sea trading. This paper shall present a concept for larger ships. The ships will be designed for CO2 transport, but the possibility for carrying alternative cargoes will be investigated, either for return voyages, or for alternative use. The question is how to optimize the ship design for various liquified gases. The CO2 transport is assumed to be performed at low pressure (7-10 barg) which requires low temperatures ( -40 to -55°C). Other gases have other transport requirements, so the feasibility of designing a multigas carrier will be investigated. The possibilities for repurposing the ships and/or dual cargo ship transport may be crucial to ensure a profitable scenario for the logistics operations. Dual cargo trade should increase the revenue, and the possibility for repurposing will reduce the risk associated with the investments. The focus areas for this paper are: • Very large CO2 carriers, (>150 000 t), for blue water trades e.g., Gulf of Mexico – Europe. A conceptual ship design for this trade will be presented. • The potential and feasibility to use the ship to transport other gases on return voyages. The relevant class rules and the IGC code compatibility of potential gas cargoes with CO2 will be studied, and the SIGTTO Chapter 7, ref [3], regarding the changeover procedures needed for a potential return cargo will be discussed. • Potential repurposing of the ship Briefly stated, we find that it is not possible to make a blanket judgment on the feasibility of alternating cargos or repurposing the vessel. This must be decided on a case-by-case basis.

Keywords: CO2 transport, ship transport, CCS