NEWS

Strict legislation on air pollution and greenhouse gas emissions, as well as conflicts in countries with oil reserves, are prompting the shipping industry to focus on alternatives to heavy oil. Small ferries can run on pure electricity, but large cruise and transport ships usually rely on liquefied natural gas (LNG). The boil-off gas from an LNG tank can be very different from the gas that is pumped out of the bottom of the tank and vaporized. Furthermore, the composition varies depending on where the LNG was bunkered. Additionally, there is a shortage of skilled workers in the industry who can operate the complex and very sensitive process gas chromatographs. Therefore, operators have to resort to alternative measurement methods. A gasQS^™ static had to prove itself in two sea trials earlier this year (see thumbnail). The challenge here was to be able to integrate additional measurement technology into an almost completed ship. The measuring device had to be installed within a few days and the staff on site had to be trained accordingly. The successful measurements in the diagram show the fluctuations in the methane number. The transitions between gas from the boil-off phase and from the liquid phase (after evaporation of LNG) are interesting: The boil-off gas with high methane content has a higher methane number than the gas from the liquid phase. Since the higher hydrocarbons can condense out of the liquid phase in the feed line, the LNG from this feed line briefly contains an increased proportion of higher hydrocarbons after the change from boil-off gas, resulting in a lower methane number. Measuring the gas quality will be necessary for gas engine manufacturers in the future.