Natural gas has been acknowledged in recent years as an environmentally friendly fuel. Its sulfur content is almost zero and the NOx concentration in the exhaust gases can be reduced by over 80%.
A large scale LNG distribution network has been in place for years, with the gas available worldwide, mainly for industrial, electricity production and domestic use. Today shipowners also want to use LNG as a fuel because it is clean and offers a way to comply with emissions regulations. However, uncertainties over the supply of LNG bunkers are preventing a faster move to gas. Owners want to know if LNG will be available in the ports to which their ships trade, and they want to know how bunkering will be carried out.
Because of a lack of bunkering facilities, LNG trucks have been the preferred alternative to fill onboard type-C tanks of relatively small sizes. But there will be a need to transfer large volumes of LNG for bigger ships and additional concerns have been raised as a consequence.
There is no worldwide standard for LNG bunkering procedures, but the most representative European ports have already looked at the development of LNG bunkering facilities to cater to the expected level of demand. Most facilities are strategically located inside Emission Control Areas (ECAs). In addition, some of the ports are close to LNG terminals, which obviously helps when it comes to distribution. The US and Canada are also paying serious attention to LNG as a bunker fuel, as well as to a variety of related issues.
Meanwhile, the International Organization for Standardization has worked on guidelines to be published in 2014 that will cover standards of bunkering equipment and some other related issues, such as risk assessment, functional requirements, training and documentation.
Transfer operations between LNG carriers and LNG terminals have been carried out for decades with very few incidents, mainly limited to insignificant leaks in connection with such cargo procedures. Standards have been developed over many years for LNG transfers using loading arms for ship-to-terminal operations, and flexible hoses for ship-to-ship loading.
LNG bunkering is not a standard transfer operation, and there are currently no common international rules or guidelines for either bunkering procedures or standardised bunker equipment. Training of personnel is also required as crew members must be familiar with the properties of new bunker fuel and safety precautions.
The ways to bunker LNG
Different bunkering methods have been developed over the past decade to address specific scenarios attendant on growing demand, mainly in the Baltic countries. Truck-to-ship LNG bunkering operations are carried out from standardised LNG trucks, with more than one truck sometimes required to bunker a single ship. These bunkering procedures are not automatic. They involve many personnel and the operations are usually lengthy because the capacity of the transfer pumps on the trucks is limited. Nevertheless, it has been demonstrated that truck-to-ship bunkering is a flexible solution as many different ships can be bunkered in different port locations.
An alternative method is a permanent onshore bunkering facility. This is advisable for ships with a fixed trade and using the same berth for commercial operations, e.g. short-sea ferries. This type of LNG bunkering can take place through a short-distance cryogenic rigid pipe and a flexible pipe or a small loading arm for final connection with the ship in a bunkering station. LNG storage tanks should be placed at a suitable distance, as close as possible to the bunkering station. The duration of the bunkering operation will depend on the rate achieved by the transfer pumps, which can be adjusted. This type of bunkering process therefore normally takes less time than the truck-to-ship option. Depending on the level of sophistication of the bunker station, and the type of automatic equipment installed, the number of specialised personnel can be reduced.
Ship-to-ship LNG bunkering operations have so far only been performed in Sweden. These operations, which began at the start of 2013 in the port of Stockholm, have involved transfers from the small bunker barge Seagas to the ferry Viking Grace. No more than two hours is required to bunker approximately 150 m3. The fuel transfer operation is in fact undertaken on a daily basis as the capacity of the bunker barge is in line with the daily consumption of the ferry in its round trip from Stockholm (Sweden) to Turku (Finland).
The use of LNG bunkering ships would be recommended when there is a significant volume of LNG to be transferred. Essentially, the capacity of an LNG ship envisaged for bunkering operations would be in the range of 3000 - 6000 m3. Nevertheless, in order to complete the chain from the LNG terminal to the gas-fuelled ship, the bunker ship will need to be loaded at a small, custom-built terminal or at a standard LNG terminal adapted for small scale LNG carriers.Last but not least, some flexible solutions, such as cryogenic containers (with or without trailers), could be an alternative means of bunkering for some ships, e.g. container vessels and Ro-Ros. Standard 40 ft containers with a capacity of approximately 35 m3 of LNG are already available in the market. In such cases, the bunkering operation is limited to loading the LNG container, then fixing the container or trailer structure to the ship and the connection to the ship’s LNG cryogenic piping.
Part two of this article will be available shortly.
The full version of this article is available in the July/August issue of LNG Industry
Read the article online at: https://www.lngindustry.com/special-reports/13082014/the-outlook-for-lng-bunkering-part-one/