Engine makers customize dual-fuel propulsion systems


With tougher emissions regulations on the horizon, vessel operators have options to comply using traditional diesel engines fitted with aftertreatment technology, or invest in dual-fuel technology that leapfrogs the phased-in emission requirements.

Operators are looking for cost-effective ways to comply; the International Maritime Organization (IMO) Tier III regulations come into effect Jan. 1, 2016, and the U.S. Environmental Protection Agency has issued its own rules. The IMO also has tough near-shore emissions regulations for what are known as emission control areas, or ECAs.

The IMO established four ECAs globally: Baltic Sea, North Sea, U.S. Caribbean and North American, which includes most of the U.S. and Canadian coast.

The North American ECA currently requires ships operating within 200 nautical miles of the U.S. and Canadian coasts to burn fuels containing less than 1 percent sulfur. On Jan. 1, 2015, the requirement shifts to allow only fuels with less than 0.1 percent sulfur content. These fuels typically have a higher cost.

To meet requirements, diesel-fueled engines must use aftertreatment such as selective catalytic reduction (SCR) and exhaust gas recirculation (EGR) that reduce emissions of pollutants.

Until recently, most vessels fueled by liquefied natural gas (LNG) were tankers that used boil-off gas from the cargo to power the engines. But the use of LNG as a fuel for other types of vessels is spreading. Engine maker Wartsila has tracked more than 100 LNG-fueled vessel projects around the world. 

Most of the major marine engine manufacturers have dual-fuel engines, usually a pairing of LNG and various traditional marine diesel fuels such as light fuel oil, heavy fuel oil or marine diesel oil. Manufacturers say the engines meet current and future requirements for emissions of nitrogen oxide (NOx), carbon dioxide (CO2), sulfur oxide (SOx) and particulates when operating on LNG fuel.

“A gas engine, because of the inherent cleanliness of natural gas fuel, meets all current and all future emission requirements better than any traditional fueled engine and without any aftertreatment,” said John Hatley, Americas vice president of ship power for Wartsila North America Inc.

Dual-fuel technology offers flexibility, making it possible to use diesel fuel away from restricted areas and LNG when operating in port, close to shore or in an ECA. Operators can choose which fuel to use based on availability and price.

Wartsila said a dual-fuel vessel can be set up to run on LNG as the primary fuel, with the capability to use liquid diesel fuels for backup and repositioning. The dual-fuel engines can start and stop in LNG mode, idle for up to 8 hours in gas mode and switch between gas and liquid fuels with no interruption in engine operation.

Dual-fuel systems are available in both 2-stroke and 4-stroke diesels, and some types may use diesel as a pilot fuel to start combustion. There are differences between a diesel-only and dual-fuel engine. For instance, components for MAN’s dual-fuel ME-GI include a modified exhaust receiver, modified cylinder cover with gas-injection valves and gas-control block, an expanding top gallery platform, high-pressure fuel-supply pipes, and mounted gas-control units.

The American Clean Skies Foundation, a nonprofit advocate for switching vehicles to use gas fuels, reported that conversion of vessels to LNG operations could be costly — up to $7 million to convert a medium-size tugboat, $11 million for a large car and passenger ferry and up to $24 million for a Great Lakes bulk carrier. In its 2012 report, “Natural Gas for Marine Vessels: U.S. Market Opportunities,” the foundation estimated that about 16 percent of the cost was allocated to engine conversion. The rest was devoted to LNG storage tanks and related vessel and safety modifications.

For many operators, fuel costs may play a major role in the decision to adopt LNG. Federal Maritime Commissioner William Doyle told a recent conference audience that because of the shale gas energy boom, natural gas for production of LNG is more than 50 percent less expensive than marine residual fuel and marine distillate fuel on an energy-equivalent basis.

A 539-ton MAN brand dual-fuel engine is lowered into a TOTE newbuild at General Dynamics NASSCO.

Courtesy General Dynamics NASSCO

At this point, most of the non-tanker LNG operations have been in ferries and smaller vessels such as tugs and offshore supply vessels (OSVs). Some LNG containerships in domestic and short-sea service will enter service soon. But the real potential for environmental impact rests with LNG adoption by the deep-sea sector.

Lloyd’s Register conducted a study that found that deep-sea shipping accounts for 70 percent of the fuel demand and associated emissions.

“Unless the deep-sea merchant ships — the bulkers, tankers and containerships — start adopting LNG, you can’t talk about widespread adoption in terms of fuel demands,” said Dimitris Argyros, lead environmental consultant for Lloyd’s.

However, scaling up for the trans-Pacific and trans-Atlantic routes could present problems simply due to the amount of LNG required for the voyage.

“I think when shipowners and operators look at the cost of storing that much LNG as opposed to moving cargo, it starts to make less sense to store LNG as a fuel,” said Roy Bleiberg, director of gas solutions for the American Bureau of Shipping.

Norway has led the shift toward LNG-fuel operations, due to strict environmental control areas as well as emissions taxes and subsidies. According to ship classification society Det Norske Veritas (DNV), the first ship with dual-fuel LNG propulsion was the Norwegian passenger ferry Glutra, launched in 2000. LNG-powered ferries entered service in 2006, with engines from Rolls-Royce. In 2013, four more Rolls-Royce-powered ferries entered service for ferry operator Torgatten Nord serving the Lofoten Islands in the north of Norway.

Norway is home to a single-fuel cargo vessel, the LNG-powered MS Høydal. The vessel, purpose-built for replenishing feed for the salmon and trout farms located along north Norway’s coast, relies on tank trucks for weekly refueling.

A crew of six operates the 230-foot-long, 52-foot-beam Høydal, according to Rolls-Royce. Normal speed is around 12 knots with very low NOx emissions and an LNG consumption of 529 pounds per hour.

Jones Act carrier Totem Ocean Trailer Express (TOTE) is converting its four-vessel fleet to run on LNG. For TOTE, the top priority is the environment rather than the cost because forecasting future commodity prices can be a risky business. Environmental requirements are clearly laid out for the future.

“We see LNG as the best thing for the environment, and at the same time we’re future-proofing the business,” said Ben Christian, project leader for TOTE. “We decided to use the best technology available so we won’t have to keep making incremental changes.”

TOTE is converting two existing Orca-class vessels in the Washington-Alaska trade to LNG. It is building two new dual-fuel Marlin-class vessels for the Jacksonville-Puerto Rico run.

The first two 3,100-teu Marlin-class vessels are under construction at the General Dynamics NASSCO Shipyard in San Diego. They are scheduled to be delivered in late 2015 and early 2016, according to Christian. They will have an expected service life of 40 years.

NASSCO will refit the two 10-year-old Orca-class vessels, operated by TOTE in the Alaska trade, during the slow season in the winters of 2016 and 2017.

For the refit, the four medium-speed diesels will be replaced with four slow-speed dual-fuel engines from Wartsila, along with integrated LNG storage and fuel gas handling systems. The LNG will be stored in two 1,100-cubic-meter tanks located above the cargo deck. Operators won’t see any changes in vessel speed or power, and the refit incorporates the redundancy of four engines to face the Alaskan seas. After the refit, the Orcas will have a 30-year service life.

“Those were the most environmentally friendly ships of their time and we are making another leap forward with them,” Christian said.

Building on the track record developed in Norway, more manufacturers are offering LNG-capable engines.

Caterpillar began shipping dual-fuel marine engines in 2013. In a news release, the company said the engines will provide flexibility for vessels operating in regulated and/or lesser-regulated areas without major changes to the engine room or exhaust gas system. The engines will operate on LNG, marine diesel oil and heavy fuel oil, with best emissions performance in gas mode.

Caterpillar’s M 46 DF, the company’s first marine dual-fuel solution, was used to power a newbuild ordered by Germany’s AIDA cruises. In gas mode, the company said the M 46 will comply with IMO Tier III as well as EPA Tier 4 regulations.

A Caterpillar compressed natural gas (CNG) dual-fuel engine will power one of seven fast ferries ordered for Rio de Janeiro, Brazil, in preparation for the 2016 Summer Olympic Games. The other six ferries for Assessoria Transporte Aquaviaro will be built with the option to retrofit the engine room for CNG use.

In the United States, the first of six LNG-fueled offshore support vessels ordered by Harvey Gulf, a privately owned and operated marine transportation company, will likely enter service before the TOTE vessels, according to Bleiberg of the American Bureau of Shipping. With the sixth vessel, Harvey Gulf will become the largest owner and operator of LNG-powered OSVs in the world, according to Chief Executive Shane Guidry.

A Harvey Gulf announcement said the company will spend $400 million to build, own and operate the LNG-powered offshore support vessels, as well as two LNG fueling docks, the first at the company’s Port Fourchon, La., terminal.

Harvey Gulf worked with the Coast Guard to develop environmentally friendly OSVs to operate in the Gulf of Mexico, complying with the ABS Enviro+ notation. With 43 people on board, each 302-foot vessel will carry over 16,000 barrels of liquid mud, 10,000 cubic feet of dry cement and 1,500 barrels of methanol.

In 2013, Crowley announced plans to build LNG-powered combined container/roll-on/roll-off vessels for its Jacksonville-Puerto Rico service. Crowley has contracted with VT Halter Marine Inc. of Pascagoula, Miss., to build the two 720-foot con-ro ships, which are designed to travel at speeds up to 22 knots and have a capacity of 2,400 teu. The boxes range in size from 20-foot standards to 53-foot-long, high-capacity units, along with up to 400 vehicles in weather-tight car decking.

The main propulsion and auxiliary engines will be fueled by LNG. According to Crowley, the LNG fuel will reduce the amount of CO2 emissions attributable to each container by approximately 38 percent.

A Rolls-Royce BV35-40P 12G is one of four gas engines powering the Norwegian car ferry MV Bergensfjord. Four other sister vessels also contain this engine model.

Courtesy Rolls-Royce

Crowley expects the Commitment-class Jones Act ships to enter service in the second and fourth quarters of 2017, to replace Crowley’s towed triple-deck barge fleet in service since the early 1970s.

According to Crowley, the ships will exceed all regulatory requirements. They will have the CLEAN notation, which requires limitation of operational emissions and discharges, as well as the Green Passport, both issued by classification society DNV.

Nordic Hamburg subsidiary GNS Shipping has ordered two dual-fuel containerships from Yangzhou Guoyu Shipbuilding in China. They will be the first short-sea box ships in Europe to run on LNG. The engines from Wartsila will use LNG but will also be able to burn conventional marine diesel oil/heavy fuel. Both vessels are scheduled to be delivered in 2016 and operated by Containerships Ltd.

Bunkering LNG presents some challenges in infrastructure and training. Harvey Gulf, TOTE and other operators are either building their own bunkering facilities or working with vendors to set up suitable terminals (see sidebar on page 58). In many parts of the world, vessels are fueled from LNG barges or shoreside trucks, which require less investment and offer more flexibility for operating requirements.

“From a technical point of view, we have experience in doing ship-to-ship LNG transfers so this is nothing new in terms of how we’re going to do it or what equipment we’re going to use,” said Argyros of Lloyd’s Register.

However, there is a concern about onboard and shoreside crews being trained to handle LNG, which is stored under pressure at -260° F.

“On the operations side, the main thing is you have personnel in the engine room who are not accustomed to an LNG-powered engine,” Argyros said. “This is a niche part of the market and you have a much smaller skill pool to look for people.” Argyos predicted experienced operators from the LNG tanker trade will be in high demand in engine rooms.

Industry experts agree that training will be critical as use of LNG spreads.

“With multiple operators at different ports, where we will have multiple crews having to operate and bunker the vessels, consistent training in that aspect will be imperative,” Bleiberg said.

As more LNG-powered vessels enter service in the next few years, the rest of the industry will be watching.

“There will be a lot of discussion about how the stewardship of your fleet will compare with other fleets, whether you’re the greenest,” Bleiberg said. “There is that element to it that the shipowners and operators are trying to leverage.”

By Professional Mariner Staff