Ship Transport of CO2: Technical Solutions and Analysis of Costs, Energy Utilization, Exergy Efficiency and CO2 Emissions
Increased focus on reducing CO2 emissions has created growing interest in CO2 capturing from industrial processes for storage in geologic formations or injection in oil reservoirs for enhanced oil recovery (EOR). Due to the scattered CO2 sources and the uncertainty in the growth of the CO2 market, a cost effective and flexible transport system is required. In this work a ship transport concept is developed as an alternative to pipeline transport. New technical solutions, cost-, energy-, exergy- and CO2 emission analysis for ship-based transport of CO2 are presented. The concept includes all the elements in the transport chain, namely liquefaction, intermediate storage, loading system, semi-pressurized ship and offshore unloading system.
Economical large-scale transport of CO2 by ship could be done in semi-pressurized vessels of around 20 000 m3 at pressures near triple point (6.5 bara and –52°C) in order to use well established design for commercial construction of LPG carriers and intermediate storage. This condition also gives the highest density in the liquid state, which reduces the transport unit cost. Liquefaction of CO2 is best achieved in an open cycle, where the refrigeration is partly or fully provided by the feed gas itself. The offshore unloading system will transport the liquid CO2 from the dedicated CO2 ship to the wellhead on the platform at the required temperature and pressure. During the unloading phase the ship is connected to a submerged turret loading (STL) system. The CO2 is pumped to a pressure high enough to avoid phase transition in the transfer lines. A flexible riser, a subsea pipeline and an insulated pipeline in the platform shaft bring the CO2 from the unloading location to the topside of the platform. The CO2 is pumped to injection pressure and heated to avoid operational problems before it is injected into the reservoir for EOR using conventional water injection wells.
The total specific energy requirement for the selected transport chain is 142 kWh tonne−1 CO2, where the liquefaction process accounts for 77%. An exergy analysis of the chain is performed showing that the minimum work required in the chain is 60 kWh tonne−1 CO2, giving a chain rational efficiency of 42%. The total CO2 emissions are estimated to be approximately 1.4% of the inlet CO2. The total costs of ship-based transport are calculated to be 20–30 USD tonne−1 for volumes larger than 2 Mt y−1 and distances limited to the North Sea. Ship transport offers a flexible alternative for bringing CO2 to offshore installations. Dedicated CO2 carriers for transport of CO2 directly from the source to the oil fields might be a key element in future CO2 infrastructures.
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Multi-period, multi-objective optimisation of the Northern Lights and Stella Maris carbon capture and storage chains
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CO<inf>2</inf> capture from offshore oil installations: An evaluation of alternative methods for deposition with emphasis on carbonated water injection
2024, Carbon Capture Science and TechnologyCapture and storage of CO2 from gas turbine power plants can be an alternative to electrification from shore to reduce the emissions from petroleum production facilities on the Norwegian Continental Shelf. The objective of this work was to analyse and rank various options for storage using technical economic analyses. The following alternatives were considered:
- 1.
Dissolution of CO2 in sea water and aquifer storage of carbonated water
- 2.
Injection of pure CO2 into an aquifer
- 3.
Compression of CO2 and pipeline transport to a collection centre
- 4.
Liquefaction of CO2 and ship transport to a collection centre
- 5.
Dissolution of CO2 in sea water and injection into oil fields (carbonated water injection, CWI)
The economic calculations show that alternatives 1 – 4 have negative net present values. A higher future CO2 tax than presently envisaged will be needed to make the alternatives economically viable. All cases related to Alternative 5 (project lifetime, heterogeneous and homogeneous reservoir models, green and brown fields) exhibit positive net present values due to incremental oil production. Most, but not all, injected CO2 remained in the reservoir, depending on the injection period.
Oxygen in the captured CO2, formation of gas hydrates and corrosion of well materials may cause operational problems of injecting sea water with dissolved CO2. These aspects have been briefly discussed. Some additional measures may have to be taken to alleviate undesired effects, but none of the issues are likely to prohibit implementation of CWI.
The results obtained suggest that CWI into producing oil reservoirs offers an economic viable and safe way for disposal of CO2 captured from offshore petroleum production plants provided that a capture plant can be installed, and that the remaining lifetime of the reservoir is so long that the benefits of improved oil recovery can be realised.
- 1.
Because carbon capture and storage methods are considered greenhouse gas reduction technologies, demand for a large liquefied CO2 (LCO2) carrier to transport captured CO2 to storage sites has arisen. To prevent the emission of boil-off CO2 gas during transport, a CO2 re-liquefaction system would be required. This study suggests a new type of LCO2 subcooling re-liquefaction system for an LCO2 carrier and demonstrates its effectiveness by comparing its performance with that of conventional re-liquefaction systems considering LCO2 storage pressure. The results show that the suggested LCO2 subcooling system has lower specific energy consumption than that of conventional LCO2 re-liquefaction systems, even with a simpler configuration. At 15 bar of storage pressure, the LCO2 subcooling system has a lower specific energy consumption of 176.91 , which is 18.2 and 5.3 % lower than that of the Linde–Hampson cycle and vapor-compression refrigeration cycle using NH3 as a refrigerant, respectively. Additionally, economic benefits can be obtained because the boil-off CO2 compressor is not required in an LCO2 subcooling system. Finally, considering CO2 re-liquefaction performance and the design constraints of the LCO2 carrier, 15 bar LCO2 storage conditions with a subcooling system are considered the most economical LCO2 carrier design.
Modeling a supply chain for carbon capture and offshore storage—A German–Norwegian case study
2024, International Journal of Greenhouse Gas ControlCarbon capture and storage (CCS) for industrial emission point sources is one of the potential instruments to achieve net-zero carbon dioxide () goals. However, emission point sources and storage formations are often far from each other, which requires capable transportation infrastructure. While pipeline transportation promises low cost for high and stable flows of , ship transportation may be more expensive but also more flexible with regards to transport quantities and storage locations. Here, we present a mixed integer programming (MIP) model to provide decision support for a CCS Supply Chain Design Problem (CCS-SCDP) with the goal of minimizing total supply chain costs. We apply the model to four future supply scenarios, capturing from German industrial sources and bringing them to the Northern Lights unloading port in Kollsnes, Norway, for storage in a submarine geological formation. Our analysis reveals that the fraction of transportation costs of total supply chain costs drop considerably from 22 to 10 percent by economies of scale if annual capture volume increases. For low capture volumes, a ship-based solution is cheaper, while an offshore pipeline solution is favored for larger capture volumes. Accordingly, the potential gains from economies of scale in a pipeline-based solution must be balanced against potential lock-in effects in the investment decision for a CCS supply chain.
Technoeconomic evaluation of post-combustion carbon capture technologies on-board a medium range tanker
2024, Computers and Chemical EngineeringThe international maritime organization has recently set targets and timelines for reducing global greenhouse gas emissions from the maritime industry, which currently stand at 1.1 Gt/year and make 3 % of the global emissions. Reducing emissions by increasing engine efficacy is the immediate target, but there is a limit to how much this path can achieve. Onboard post-combustion carbon capture and concentration in large marine vessels is emerging as an interim approach to reduce maritime emissions until large-scale deployment of low/zero emission fuels become viable. In this paper, we evaluate three carbon capture technologies (chemical absorption using either aqueous MEA or aqueous NH3 as the solvent, cryogenic separation, and membrane separation) for a medium-range tanker for two fuels, namely heavy fuel oil and liquefied natural gas. The capture cost per tonne of CO2 (recovery>90 %, purity>95 %) was considered as the assessment criterion, with simultaneous evaluation of other aspects such as energy and space demands. The simulations were carried out using MATLAB and ASPEN V12. For rate-based models, the adjustable parameters for the model were tuned using pilot plant data. Additionally, options for hot and cold energy integration were also assessed and implemented. Based on the reference ship conditions and assessment criteria, the simulation studies show that amine-based absorption is the best prospect for on-board capture by a clear margin.
Energy and exergy analysis of a novel ejector powered CO<inf>2</inf> liquefaction system (EPLS) and comparative evaluation with four other systems
2023, Energy Conversion and ManagementCO2 emissions from industrial activities has been imposed several environmental problems to the human life. Mitigation actions like designing and implementing the CO2 capture systems is a beneficial way to reduce the amount of carbon dioxide in the atmosphere. In the last part of capturing process, the CO2 needs to be pressurized to be transported, stored, or used elsewhere. In the present study, five different systems for the carbon dioxide post-capture are designed and compared with each other which include a multi-stage compression, basic and modified Claude, the ejector boosted absorption systems, and the new introduced ejector powered liquefaction system (EPLS). The effect of several decision parameters on the performance of each system is evaluated and the detailed energetic and exergetic analysis of the components in each system is carried out. The results show that the new introduced EPLS system has better performance (in terms of COP and second law efficiency) than other four systems and the multi-stage compression system has the nearest values to the EPLS. The dependency of the EPLS performance to the main decision parameters including the pressure ratio and the intercooling temperature is considerably lower than other evaluated systems. In this regard, the multi-stage compression system indicates the largest dependence to the pressure ratio and intercooling temperature of compressors. The evaluations on the components of each system reveals that by the modifications in the Claude layout, the modified Claude system requires less cooling demand than other systems (585.5 kW at the basic conditions) and on the other hand, the DEBARS system has the lowest power consumption between the other systems (280.6 kW at the basic conditions). Evaluations on the exergetic efficiencies of components show that the intercoolers beside the compressors in the main subsystems and the liquid ejector in DEBARS, have the highest exergy destruction ratio in each system.