MAN looks at alternative fuels and optimising the existing fleet
MAN Diesel & Turbo was first to the market with an LNG-fuelled two-stroke engine, and is now looking other low flash point fuels, as well as helping existing vessels save fuel and meet emissions limits in order to remain competitive.
The race for viable gas-fuelled large low speed marine engines sees MAN Diesel & Turbo in the lead at present, thanks to the early introduction of its ME-GI engine. This is based on high pressure gas technology developed by MAN at its two-stroke centre in Denmark, in cooperation with licensees Hyundai Heavy Industries in Korea and Mitsui Engineering & Shipbuilding in Japan.
Originally announced in 2011, the ME-GI engine builds on the company’s original dual-fuel concept from the 1990s, known as the MC-GI. The first two-stroke GI engine, a 12K80MC-GI-S, entered service at a power plant in Chiba, near Tokyo, Japan in 1994.
The ME-GI follows on from the original engine in that it is a gas-injection, dual-fuel, low-speed unit intended as main propulsion in LNG carriers or any other type of merchant marine vessel, which 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. Depending on relative price and availability, as well as environmental considerations, the ME-GI engine gives shipowners and operators the option of using either gas or HFO.
Examples have run at MAN’s Diesel Centre in Copenhagen as well as at Hyundai and Mitsui, and the unit has picked up significant orders from TOTE in North America, for two 8L70 ME-GI powered 3,100TEU container ships, and international operator Teekay LNG Partners. The Teekay order, for two LNG tankers, is particularly notable as the ships have a twin-screw plant based on 2 x 5G70ME-GI ultra-long-stroke G-type engines for high propulsion efficiency.
Notwithstanding this early success, MAN has continued with the development of its dual-fuel two-stroke portfolio and has announced the development of the MELGI derivative, with offers the possibility of using other sustainable low flash-point fuels such as methanol and liquefied petroleum gas (LPG) rather than LNG.
Methanol, according to MAN, is sulphur-free and the company sees considerable market potential for its use, stemming from the low-sulphur fuel requirements for ship operation within ECAs. All its existing MAN B&W two-stroke engines are expected to be suitable for retrofit, in a cost-effective manner, for LGI operation. One particular advantage that methanol, LPG and similar fuels hold over LNG is that the onboard storage tank arrangements are much simpler, opening the door to simple retrofits.
Ole Grøne, senior vice president – low speed promotion & sales, said: “We can really see the momentum towards dual-fuel operation building now. The ME-GI engine we introduced – and immediately received orders for – in late-2012 confirmed the growing demand to have the option to run ships on LNG as well as HFO in the face of increasing fuel prices. Owing to market interest, we have now extended our dual- fuel engine programme with an ME-LGI unit that can run on liquid fuels.
“The interest in our ME-LGI engine confirms this dual-fuel, low-speed trend and offers even more alternatives to HFO – including methanol, LPG, di-methyl ether (DME), and bio- ethanol as well as several other, low-flashpoint fuels.”
MAN has subsequently signed a Letter of Intent with Vancouver-based Waterfront Shipping for the use of four MAN ME-LGI engines on its ships. The engines will run on a blend of 95% methanol and 5% diesel fuel. The four G50ME-LGI units are targeted for the end of 2014, with engine delivery to follow in the summer of 2015.
The ME-LGI concept’s ‘ME-’ prefix indicates that it is based on the ME electronically controlled engine, in this case with fuel injected by a so-called ‘booster’ fuel injection valve. This fuel booster, valve ensures that fuel gas can be injected at low pressure, and is claimed to significantly reduce first time costs and increase reliability. MAN developed the ME-LGI engine knowing that methanol and LPG carriers have operated at sea for many years and many more LPG tankers are currently being built as the global LPG infrastructure grows. With a viable, convenient and economic fuel already on-board, exploiting a fraction of the cargo to power a vessel, makes sense, the company says. With another important factor being the benefit to the environment, MAN Diesel & Turbo believes that with further development a fully Tier-III-compatible ME-LGI version will be viable.
MAN Diesel and Turbo has developed a range of retrofit solutions that apply its latest developments to engines in service, bringing them up to current standards, meeting modern emission levels and cutting running costs. The concept applies to all MAN Diesel & Turbo engines, propellers and turbochargers.
Heading the list of options is the Alpha Lubricator system, based on the principle of injecting a specific volume of oil into a cylinder liner after a preset number of engine revolutions. This can be adjusted as required for each individual cylinder unit, and a computer automatically adjusts the feed-rate according to the engine’s power output. The Alpha Lubricator thus cuts feed rates, offering potential savings in lubricating oil costs of 20%-30%.
Slide fuel valves come as standard on all new MAN B&W engines but can be retrofitted on MC mechanical engines. The slide fuel valve eliminates the so-called ‘sac volume’, reducing fuel-oil consumption and eliminating dripping from the fuel-valve nozzle. Additionally, it offers NOx reduction potential. The reduced sac volume leads to better combustion, fewer deposits throughout the gas-ways and a reduction in HC, NOx, PM emissions and smoke. The valves offer improved low-load performance with regard to soot formation, reducing the need to run at high revolutions in order to clean exhaust channels.
Although most older MAN B&W two-stroke engines are designed for continuous operation at 100% engine load, with appropriate precautions and de-rating, safe and reliable continuous engine operation down to 10% engine load is possible with more frequent inspections but without major modifications. The basic requirements for slow steaming are slide fuel valves and the monitoring of exhaust gas ways for fouling. MAN Diesel & Turbo also recommends fitting the Alpha Lubricator. For existing applications with three or four turbochargers, the company recommends a turbocharger cut-out system to improve main-engine performance during all low-load operations.
In an industry where slow steaming has become the norm – and for the majority of vessels this looks like a lasting trend – fuel savings can be further enhanced by upgrading and or retrofitting propellers. The company’s Kappel propeller claims fuel savings of up to 6%, or greater when combined with other propulsion improvements, such as engine de-rating and installation of the company’s PMI system, a computerised tool for performance evaluation of engines.
MAN Diesel & Turbo has carried out a case study involving a typical 74,000dwt Panamax tanker. Before starting work on any ship, the company’s service division, MAN PrimeServ, carries out a full analysis covering:
Investigation of full engine-de-rating potential;
Torsional vibration calculations;
Whether a torsional vibration counter is needed;
Propeller performance, for new propeller at new rating;
Quote for engine de-rating and propeller.
The tanker case study suggested a savings potential of 12-15% in terms of fuel consumption when allowing for costs for de-rating, the replacement of the original propeller with an Alpha Kappel propeller, and the installation of a rudder bulb. With the total cost coming to €1.2 million, a payback time of 2½ years was projected.
One current problem recognised by the company is the difficulty faced by shipowners in obtaining finance for de-rating and other essential modifications. Financial institutions mostly display little interest in facilitating the loans required.
Since 2009, MAN Diesel & Turbo has offered the Trident financing programme to facilitate customer investment in PrimeServ retrofits, knowing that saved expenses will cover the investment. The company believes that the investment required to purchase retrofit solutions is relatively low compared to the resultant savings, and the payback period can often be under two years..
The scheme is directly linked to a two-year payback period, with four semi-annual payments. In this way, the payment is spread out over the payback period and ultimately balanced by the savings created by the retrofit itself. PrimeServ sees this distributed payment model as a significant incentive to attract its customers to retrofit solutions.
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