Dual fuel gains credibility in the low speed market

ME-GI test engine at MAN Diesel & Turbo in Copenhagen ME-GI test engine at MAN Diesel & Turbo in Copenhagen

Both major designers of large low speed two stroke marine engines have demonstrated their commitment to gas as an alternative fuel and have demonstrated dual-fuel technology applied to their engine designs, while, additionally, two Asian licensees are demonstrating their commitment to LNG ship power.

Looking at gas engine technology in general, Wärtsilä claims to be by far the biggest and to occupy a market leading position among the three major gas engine manufacturers. The company claims wide experience of gas-fuelled engines in both land-based and marine applications. Based on this long experience, combined with its marine market knowledge, Wärtsilä believes the time is right to take major development steps in its engine technology by applying dual-fuel technology to its Low Speed portfolio.

Tomas Aminoff, director product management, Wärtsilä Ship Power, explains that the company has more than 40 years of experience in gas engine applications for the marine sector. However, the real breakthrough came with the introduction of the company’s dual-fuel engine technology in the mid 1990s. “Today”, says Mr Aminoff, “Wärtsilä is the recognised global leader in gas engine applications for both the marine and power plant industries. Today there are around 180 vessels in service or on order with Wärtsilä medium speed dual-fuel engines resulting in more than 600 engines and five million running hours.”

He cites the example of the breakthrough conversion project of the 25,000dwt product tanker Bit Viking in late 2011. Bit Viking is operated by Statoil along the Norwegian coastline, and in November 2011 she began sailing with her the two Wärtsilä 6L50DF main engines fuelled by LNG. Bit Viking is the first, and still the only, gas mechanical LNG powered vessel in service and has been operating during the most demanding winter storms in North Sea on gas. Her operational record on gas fuel to date shows over 99% availability.

Encouraged by the track record of medium speed dual-fuel engines, Wärtsilä announced, in February 2011, the development of a low speed dual-fuel engine. The following September, Wärtsilä released information about the successful trials on the test engine in Trieste. The development work on the 50cm-bore converted Wärtsilä RT-flex50 continues, and further information is expected to be announced to the marine industry during 2012.

The decision to select low pressure dual-fuel technology is based on Wärtsilä’s experience of gas technologies and on feedback from the marine community, which the company says has indicated a clear preference for such technology.

Wärtsilä’s current offerings in gas-fuelled engines encompass three distinct gas technologies:

  • dual-fuel (DF) engines based on low pressure gas feed with combustion according to the Otto principle and wide fuel flexibility;
  • spark ignition (SG) engines based on low pressure gas feed with combustion based on the Otto principle and with gas operation only; and
  • gas diesel (GD) engines with high pressure gas feed with Diesel combustion and wide fuel flexibility.

Wärtsilä claims to be biggest manufacture in all three technological areas, and to have wide experience in both power plant and marine applications. Based on this experience, and when taking the specific marine market demand into account, Wärtsilä decided that dual-fuel technology was the most appropriate for the low speed portfolio.

“The benefit with the Dual-Fuel technology is that it allows a gas handling system that stay below 10 bar in all conditions and meet international and local Sulphur and NOx limitations, Including IMO Tier III, without any secondary methods like SCR or EGR at the same time while offering full fuel flexibility”, says Mr Aminoff. “No other gas technology can do this. Compared to a high pressure system the gas handling becomes simpler, safer and more reliable thanks to the lack of high pressure gas equipment that requires both extra investment and consumes energy when in operation. Also NOx secondary methods are not needed on-board the vessel and EGR or SCR can be eliminated and once again both investment and operating costs can be saved.”

A large merchant vessel with a single low speed engine can burn HFO when crossing the oceans, and switch to gas only when approaching shore and needing access to environmentally sensitive areas, thus minimising the need for expensive gas storage systems. For container vessels, Wärtsilä considers one possibility to be the utilisation of containers to store gas tanks. These can be added to the vessel at the final port before entering an environmental control area (ECA) and can even be exchanged during the stay in the ECA. In this way the investments in gas handling equipments can be minimised. This gives additional freedom to switch between gas and HFO depending on what fuel is cheaper at any point of time and to take full advantage of regional price differences.

“The future is gas, for flexibility dual-fuel and for simplicity and safety for the crew it is low pressure”, says Mr Aminoff.

MAN Diesel & Turbo sees parallels between the debut of the Selandia and the introduction of LNG fuel. “Exactly at the centenary for the change from steam to diesel, the marine engine of the future is ready to further reduce CO2 emissions”, says the company.

“In 1912, Diesel engines showed that, in comparison with steam power, it was possible to substantially reduce CO2 emissions per produced kilowatt-hour. As early as in 1920, CO2 emissions had reduced by more than 50%. Throughout the next 50 years, Diesel engines and steam engines competed for further reductions in fuel consumption, and hence CO2 emissions. The diesel engine won,” says Hans Otto Kristensen, senior researcher at the Institute for Mechanical Technology at The Technical University of Denmark.

MAN also emphasises the fact that Selandia’s engines were designed in Copenhagen, at B&W, where MAN Diesel & Turbo’s research into gas-fuelled two-stroke engines is conducted today. “Natural gas has turned out to be an attractive fuel for marine engines, as a gas engine has an approximately 25% lower CO2 emission level than a corresponding diesel engine. At the same time, a change from diesel to natural gas will solve the problems with sulphur pollution, so that the strict requirements on sulphur emissions coming into force in 2015 can be easily met, says Mr Kristensen.

“Exactly 100 years after Selandia excited the world, we developed the ME-GI gas engine, which is ready to start a new era and reduce CO2 emissions further. In my opinion, the future is liquefied natural gas”, says Thomas Knudsen, head of business unit low speed, MAN Diesel & Turbo.

The company adds that two Far Eastern companies, both MAN licensees, have separately announced their intention to build prototypes of MAN’s two-stroke gas engine. This, says MAN, means the ME-GI is edging closer to commercial production.

Both HHI-EMD (the engine and machinery division of Hyundai Heavy Industries) and MES (Mitsui Engineering and Shipbuilding) have said they are to carry out full-scale demonstrations of the ME-GI principle based on the temporary conversion of existing production engines to ME-GI units. Accordingly, HHI intends to convert an 8S70ME-GI unit in November 2012, while MES will convert a 6S70ME-GI unit in the second quarter of 2013.

Ole Grøne, senior vice president low-speed promotion & sales, MAN Diesel & Turbo said: “We view this latest development in the ME-GI project as very positive. It is immensely encouraging that some of our biggest licensees, based in the greatest shipbuilding countries in the world, are showing such tangible interest in this gas engine.”

Formally unveiled at a major event at MAN Diesel & Turbo’s Copenhagen Diesel Research Centre in May 2011, just after delegates to the 33rd Motorship Propulsion and Emissions conference had received a preview, the ME-GI development can be traced back to the 1990s and the prototype MC-GI dual-fuel engine. The ME-GI engine is a gas-injection, dual-fuel, low-speed diesel engine that, can burn gas or fuel-oil at any ratio, depending on the energy source available on board and dictated by relative cost and owner preference. MAN Diesel & Turbo sees significant opportunities arising for gas-fuelled tonnage as fuel prices rise and exhaust emission limits tighten. Its research indicates that the ME-GI engine, incorporating additional exhaust gas recirculation and waste-heat recovery modules, will deliver reductions in CO2, NOx and SOx fulfilling IMO Tier III regulations.

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