Large-scale sloshing test (Image: MARIN)
Switching to LNG as a fuel can reduce CO2 by up to 20% and significantly improve the air quality by reducing PM and NOx, and is therefore a focus of the Dutch Government as it strives to reduce gas emissions that affect the environment and health. SLING, a unique collaboration between public and private entities, and part of the Dutch Organisation for Scientific Research (NWO) funded in part by the Ministry of Education, Culture and Science and Ministry of Economy, has received a grant to find solutions to financial thresholds that currently inhibit broad development.
Funds in the amount of EUR 3.45 million (USD 3.65 million) have been approved, bringing the total research budget to 5.3 million. The funds have been awarded by technology foundation STW, which is part of NWO.
Acknowledging the LNG-as-fuel market is still in its development phase, STW explains huge investments are needed by LNG suppliers in the required infrastructures (LNG stations, feeders, bunker barges), and by end users (ship and truck owners) in new technologies to run on LNG. LNG prices at fuel stations need to be low enough for end users to switch fuel, and high enough for suppliers to invest.
The business case can be improved by reducing the infrastructure costs. SLING, so-named for the term that refers in the industry to Sloshing of Liquefied Natural Gas, focuses on the reduction of the investment and the operational costs for LNG feeders and bunker barges by an optimal design of LNG cargo tanks. According to Maritime Research Institute Netherlands (MARIN), sloshing in partially filled LNG tanks is the most emerging technical issue and concern of the LNG industry associated with the application of membrane technology.
LNG is stored onboard a ship at a temperature just below its boiling point (ca. -162°C) at near atmospheric pressure. Special insulated cargo tanks are required to minimize the heat transfer, protecting the steel structure of the ship and limiting the evaporation of LNG (boil-off). LNG will slosh inside the tank exerting impact loads on the cargo tank when the tank is partially filled and exposed to ship motions. By applying membrane cargo tanks for feeders or bunker barges, as used in the large scale LNG chain, maximum use of available space can be achieved, resulting in compacter ships or increased capacity. This reduces the investment costs. As sloshing loads are expected to be smaller for small scale LNG, a new balance between strength of tank insulation and its thermal efficiency could be obtained leading to a reduction of the operational costs.
Such an optimisation requires a clearer understanding of the sloshing physics, as the existing design methodology shows to be overly conservative but not always entirely representing reality. The challenge with sloshing is that it involves a liquid, a vapour and a structure that interact at different length and time scales. SLING will research the multiphase physics and draw-up the basis for a representative design methodology, through four interconnected projects which are named: (1) Liquid, (2) Vapour, (3) Structure, and (4) Interaction. The projects will be realised using an innovative test set-up, advanced measurements, and numerical modelling.
The main applicant for the project, Prof. ML Kaminski (TU Delft) is supported by the following participants: Phase Transition (Shell, Total, Nippon Kaiji Kyokai, GTT, MARIN, Accede BV, Anthony Veder, Argos, Bureau Veritas, Damen, Demcon-BuNova and Femto Engineering), University of Groningen, Eindhoven University of Technology, and University of Twente.
(Source: STW)
