1 ! 1/! LNG study for MPSE project 1. Fuel alternatives LNG is considered in this study as it meets the most stringent environmental restrictions. However, the ship will also be equipped with Marine Gas Oil tanks, to provide redundancy and flexibility during operation. As natural gas is a clean fuel, there is no need to install any exhaust gas cleaning equipment. However, a LNG configuration requires more space than a traditional fuel oil system. Safety aspects also increase the complexity of the supply chain, ship design and operations. 2. Engine alternatives There are two major manufacturers of DF engines, MAN and Wärtsilä. The latter will be used in this study as the company has already made concepts for integrating the whole system inside the vessel. DF-engines are needed as they can utilize both natural gas and diesel fuel. 3. LNG tank configuration LNG tanks require about 2-4 times more space than a conventional fuel storage tank, considering tank room and insulation. Trying to fit the large volume of LNG to provide a long operational range seems to not be possible with standard tanks. Therefore custom made tanks may be required, depending on the required range. EME have been into contact with LNG tank manufacturers and they seem to be able to manufacture a pressurized tank of 1000 m3 or 2 x 500 m3. The area shaded below is suitable for LNG tanks or corresponding equipment, based on a beam of 20m. For comparison, sizes of Wärtsilä LNGPac can be seen in comparison. The area in black of the tank cannot fit inside the vessel with the current setup.
2 ! 2/! 4. LNG system The LNGPac is a modularized, complete system for on-board gas fuel storage and handling. It includes pressurized storage tanks, cryogenic valves and connections, evaporators, LNG insulated piping, automation & controls and gas detection devices. Example of Wärtsilä LNGPac below.
3 ! 3/! 4.1.Bunkering station!
4 ! 4/! 5. Boil-off gas and holding time For this vessel, we are assuming a hotel load of 1000 kw. This hotel load is significantly above the power generated from boil-off, which means that a constant pressure inside the tank can be kept indefinitely. Holding time is describes how long time it will take to increase the tank pressure to the maximum allowed. The required holding time depends on how the vessel is operated. The tank pressure is being built-up by evaporation of LNG by thermal leakage through the insulation of the tank. The pressure does not build up if the hotel load is more than the heat leakage into the tank, due the capability of the DF-engine to use vaporized gas as fuel. As an indication, a 200 m3 pressurized type C tank, filled at 50% could hold LNG for about 25 days, even without any gas consumption from the tank. Boil-off from LNG storage tank should not be a problem for this installation.
5 !! 5/! 6. Range of vessel, LNG operation At the speed of 15 knots, the total engine power (propulsion power + 10% losses + hotel load), is estimated to be 4700 kw. This power can be achieved by 2 x 9L34DF. Based on this engine set up, an estimation of the operational range of the vessel was made. Correspondingly, we can estimate how long the LNG will last if the vessel operates at hotel load. A Wärtsilä 9L20DF engine at 0 % MCR will provide the power for the hotel load.
6 ! 6/! 7. Range of vessel, MGO operation If the DF-engines are operated on MGO, the following ranges can be estimated. The power supplied by 2 x 9L34DF-engines.
7 !! 7/!. Ventilation of LNG tank The LNGPac will be fitted with a pressure valve, which will release the gas to the atmosphere in order to avoid dangerous pressure build-up. The evacuated gas is vented to a safe location, following the requirements below. The gas mast will need to be installed according to regulations. One possible setup is seen below.
8 ! /! 9. Cold Recovery The Wärtsilä Cold Recovery solution, enables the cold energy of the LNG to be utilized by the ship s HVAC system. In the new Cold Recovery system Wärtsilä directly connects the ship s HVAC (or other refrigeration systems) to the Tank Connection Space. Thus a complete circuit consisting of heat exchangers, valves and pumps can be removed. Cold Recovery could be an option considering the vessel is in operation globally. 10. Rules and regulations by DNV GL The new DNV GL Rules for Gas Fuelled Ship Installations will be consistent with the IGF Code and are planned to be published July 2015 and to enter into force January 2016.