Hapag Lloyd’s Sajir container ship will be the largest vessel so far converted to run partially on LNG
Merchant ship operators worldwide are under pressure to comply with International Maritime Organisation rules on SOx and NOx emissions. Until now, operators have been able to burn the lowest and dirtiest grades of heavy oils with relative impunity.
That is now ending. The IMO has introduced two new emissions standards that restrict a ship’s fuel sulphur content to 0.5% in selected US and EU littorals, and 3.5% on oceanic waters.
Shipowners are facing a choice of three options. Option 1 is to buy more expensive lower-sulphur fuel. Since ships consume large quantities of fuel (5 million bpd globally), that is an expensive choice. Option 2 is to fit scrubbers to remove SOx and NOx from the exhaust funnel. This is currently the most popular solution. Option 3 is to replace heavy oils with methane, bunkered in the form of LNG. Wholesale replacement is unlikely – too much un-depreciated plant value would have to be written off. However, partial replacement is becoming a realistic option.
If a ship has its engines adapted to take dual fuels (expensive but not outrageously so), and has a small LNG fuel bunkering and handling system fitted (moderately expensive, but again not outrageous), then it can switch to compliant LNG propulsion as it enters and leaves the low-emissions zones close to EU and US ports, and revert to dirtier (but still compliant) oil for the bulk of its passage.
Sailing with giants
So far, LNG dual-fuelling has been confined to small ships. However, Hapag Lloyd has now announced the dual-fuelling of the 153,000 tonne Sajir, a 15,000 TEU containership. This is probably the largest dual-fuel conversion yet.
Sajir will be fitted with an LNG storage and handling system provided by MAN Cryo (MAN acquired a marine gas fuel-handling and supply business from Linde’s Cryo in February 2016). The fuel system will displace around 3% of Sajir’s container capacity.
Reports conflict over what is planned for Sajir’s engine. However, it appears that its existing engine will be replaced rather than modified, with a unit that uses high-pressure methane in a diesel cycle. The result of this choice will be minimal methane slippage.
At loads below 10% the engine’s control system automatically switches to fuel oil, but above 10% the operator can specify the gas/fuel mix. By the time it is installed (the work is scheduled for 2020, and will be carried out in Shanghai’s Huarun Dadong Dockyard shipyard) the most restrictive NOx regulations will be in force, and Sajir’s power plant will need to use an exhaust gas catalytic reducer to bring NOx emissions down to the permitted level, as methane forms NOx when combusted at the higher temperatures of the diesel cycle. The gas system operates at 4,350 psi.