Engine and fuel system developers are exploring the next generation of fuel gas supply systems to accommodate LPG and eventually ammonia for two-stroke engines.
MAN Energy Solutions has tested an LPG fuel conditioning module (FCM) from Alfa Laval using its first LPG-burning, dual-fuel ME-LGIP engine. Tests with the fuel valve train and a simulated engine load began in the second quarter of 2018, followed by online tests using MAN’s 4T50ME-X prototype engine Copenhagen in early 2019.
“Both sets of test results verify the booster’s ramping functions and its ability to match the output pressure to our engine’s changing load,” said MAN promotion manager, dual-fuel engines René Sejer Laursen. “In fact, almost no influence from the engine load can be seen, which demonstrates the effectiveness of Alfa Laval’s automation and control.”
LPG must be pumped at a higher supply pressure than other low flashpoint fuels (including LNG and methanol) to avoid it changing state and to handle a variety of compositions on the butane-propane spectrum. To deliver LPG at the 53 barg pressure required, the FCM incorporates new pumping technology and high-pressure heat exchange.
The high-pressure skid has a filtration stage comprising two independent chambers, which allows for servicing while in continuous operation – a setup derived from Alfa Laval’s previous booster experience with methanol. The automation and control system matches the LPG flow to fluctuating engine load without unnecessary heat input from the pumping and flashing of light fractions in the LPG.
The unit is also capable of full liquid LPG recovery and partial gas recovery when the engine or fuel valve train is purged. This saves vessel operators from losing their cargo or fuel and minimises the release of hydrocarbons into the atmosphere in line with international regulations and guidance.
As reported previously, MAN is developing an ammonia-fuelled engine. Mr Laursen said that the Alfa Laval FCM LPG had been evaluated for use with ammonia fuel. The system can be made compatible with only a small investment, he said.
Alfa Laval previously developed a methanol FCM to work with MAN’s ME-LGI engines onboard seven chemical tankers chartered by Methanex subsidiary Waterfront Shipping in 2017.
The uptake of alternative fuels in shipping will be discussed by shipowners at Riviera Maritime Media's Sulphur Cap 2020 Cnference in Amnsterdam on 8-9 May.