Here we describe our project that we are working on. We at Donsötank wants to be a forerunner when it comes to safety and environmental issues. We are continuously working on projects to develop our existing core business that is Oil Tankers, but are also focusing to expand the business in to other fleet segments in transports at sea. Offshore, Tugs, Dry cargo, LNG-transports. to mention a few.
This projects aim is to build and operate one small scale LNG-feeder. We see a demand of a vessel this size to distribute LNG to the Nordic region, when it comes to bunkering and also to supply the land industry. Our LNG-Feeder are planned to be built with A-tanks. The A-tanks are of a non pressurized design, same as used in the LPG-feeders but with a new patented support system. These supports lets the tanks move freely to take up the size changes of the tanks, due to the higher temperature changes when loading LNG compared to LPG. The tanks are insulated with a void space of 600mm and 400mm insulation covered by a second barrier supplied by Torgy LNG. This insulation is enough to contain the LNG in the tanks up to one week before the pressure reach 0,7bar which is the maximum pressure for this tank design.
Since this is a non pressurized tank we must take care of the so called boil-off from the LNG-cargo. Releasing methane into the atmosphere is a driver for the greenhouse effect and is something that no one wants. For taking care of the boil-off from the LNG that is in this case about 9 ton methane per day, we are installing one pure gas main engine from Rolls-Royce to use the boil-off as fuel to move the vessel from A-B. The consumption of the main engine is exactly 9 tons per day, same as the boil off from the LNG cargo. If the vessel has to stay at anchorage for longer periods we have installed a liquefaction plant on the vessel to take care of the boil-off, this uses energy to convert the gas into liquid again. If none of the two boil-off equipment previously mentioned should work for some instance, we have also installed one methane burner that can burn the methane as a last insurance. Just to make sure we prevent any leakages of methane in to the atmosphere.
The advantages with building a LNG-Feeder with A-tanks instead of C-tanks are many.
Due to low pressure in the tanks the LNG is always delivered cold to the customer.
Cheaper construction. A LNG-feeder is a costly vessel to build, mostly due to the tanks. The A-tank design is cheaper to build than the C-tank, and can be built at any shipyard.
How ever, we have met some challenges during the way
LNG market for small scale distribution and bunkering has not developed as predicted
Banks unwilling to take risk in a “new” market and with a “new” pilot LNG-vessel
Project partners are Donsötank, Jahre Holding, DNVGL, Torgy and Rolls-Royce.