First two-stroke success for ethane fuel
The world’s first two-stroke engine to run on ethane has successfully passed gas trials on board the liquefied ethylene gas (LEG) carrier ‘Gaschem Beluga’, with engine designer MAN Diesel & Turbo hailing the positive operational performance as “expanding alternative fuel possibilities”.
The Mitsui-MAN B&W 7G50ME-C9.5-GIE (gas injection ethane) unit is the first in a series of two main engines for two 36,000m3 LEG carriers ordered by Hartmann Reederei of Germany and Ocean Yield of Norway, and constructed at Sinopacific Offshore Engineering in China. Ethane was chosen as fuel for the LEG carriers, in preference to HFO, due to its more competitive pricing. As a fuel, its emissions profile is similar to methane and contains negligible sulphur and comparatively lower CO2.
MAN Diesel & Turbo personnel monitored proceedings aboard the vessel and reported successful operation on ethane during a sailing between Houston and the Bahamas, with the engine responding as expected to different loads. No gas leaks were observed while ethane levels in the double-walled piping were constant and comfortably under the gas’s lower explosive limit.
Gaschem Beluga has already achieved a total of 550 operational hours on ethane – after the gas test she crossed the Atlantic powered solely by the fuel. The vessel is equipped with a propulsion package supplied by MAN including a remote control system AT3000, a VBS 1350 – ODS Mk5 CP propeller, and a shaft generator with frequency converter that enables it to run on variable speed between 80 to 100 rpm.
Captain Ulrich Adami, fleet manager, Hartmann Reederei, said: “Developing and finalising this type of vessel was hard work for the whole team and the process took several years. We already knew that Gaschem Beluga was a very good ship with a pioneering technology. But there is always a difference between a plan and its successful implementation. We are proud that we achieved the expected results.”
René Sejer Laursen, sales & promotion manager, MAN Diesel & Turbo, added: “The reports from the ME-GIE trials and first operational experiences are very encouraging and confirm our faith in this ground-breaking technology. While the engine is primarily designed for the combustion of ethane gas, our research shows that it is also possible to operate the engine on other gas types. This development is particularly exciting as it opens the prospect for multi-fuel combustion, including the combustion of methane, waste gas, and volatile organic compounds (VOCs).”
MAN Diesel & Turbo said that its research has recently confirmed that ME-GIE operation on VOCs is feasible, making it a suitable main driver within the shuttle tanker and VLCC segments. MAN Diesel & Turbo currently has eight ME-GIE engines on order.
Using waste gas
While MAN B&W ME-GI engines have been designed for use by methane, operation on ethane is a new development. After methane, ethane is the second-largest component of natural gas representing between 1-6% of content by volume. However, before natural gas can be used as a commercial fuel, it must be processed to remove impurities, including ethane. Like many hydrocarbons, ethane is isolated on an industrial scale from natural gas, usually by liquefaction at cryogenic temperatures. Its chief use is within ethylene production.
The engines will be able to run on a mixture of LPG and methane (or ethane) with an unchanged gas-mode efficiency. Such a mixture may comprise as much as 50% LPG – in fact MAN Diesel & Turbo’s findings thus far indicate that an even greater LPG percentage can be used.
MAN Diesel & Turbo sees significant opportunities in the development of the ME-GIE as the engine can also run on almost any form of waste gas. Such gases could be the light hydrocarbons or VOCs emitted from crude oil during storage and during the loading/unloading of crude oil. This opens the door for new applications for the engine in, for example, shuttle tankers, for power generation in remote power plants, or in offshore applications – such as floating production storage and offloading vessels (FPSOs) – where VOC is abundant and poses a potential environmental hazard.
The ME-GIE is based on MAN Diesel & Turbo’s ME-GI dual-fuel engine – burning LNG - which has already received 200 orders. The ME-GIE features MAN Diesel & Turbo’s newly developed pump vaporizer unit (PVU), which matches the requirements for the supply of high-pressure LNG to the ME-GIE engine. The PVU is said to offer low installation costs and smaller space requirement than other fuel-gas supply systems while offering full pump redundancy. Tier III NOx operation can be met in combination with either high- or low-pressure selective catalytic reduction systems.
The engine can be delivered in the 5-90 MW power range.
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