Record-breaking dual-fuel power

by | 12th March 2018 | News

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The Naval Architect: March 2018Engines

Dual-fuel, two-stroke propulsion engine technology has received a prestigious and large-scale endorsement through the nomination of X-DF machinery developed by Winterthur Gas & Diesel (WinGD) for CMA CGM containership newbuilds of record-breaking capacity.


The shipbuilding programme entails nine 22,000TEU vessels, all of which are scheduled to be delivered in 2020 for the Asia/North Europe trade. The orders have been split between two members of the China State Shipbuilding Corporation (CSSC), whereby five will be constructed by Hudong-Zhonghua, and four by Shanghai Waigaoqiao Shipbuilding. In each case, the primary power installation will be a WinGD licensee-produced 12-cylinder X92DF engine.


Swiss-headquartered WinGD has itself been a 100% subsidiary of CSSC since June 2016, following the Chinese group’s purchase of Wärtsilä’s remaining 30% shareholding.


CMA CGM plans to use the LNG fuel capability of the new ships’ plant to the maximum, while still reliant on an element of oil for the engine’s pilot ignition system. Each ship’s LNG fuel storage capacity will allow for a full round-voyage on LNG before refuelling, representing a substantially higher LNG bunker volume than on any other vessel to date.


By opting for LNG dual-fuel propulsion, operation in gas mode will virtually eliminate sulphur emissions, ensuring compliance with IMO’s 2020 global 0.5% sulphur cap, and will yield a 20% improvement in the ships’ Energy Efficiency Design Index (EEDI) relative to a diesel-fuelled installation. X-DF types meet IMO Tier III NOx criteria when running on gas, obviating the need for selective catalytic reduction (SCR) or exhaust gas
recirculation (EGR).   


But the move to embrace LNG in such fashion has to be seen not only in the light of unfolding legislative requirements but also in the context of CMA CGM’s own corporate goals. It demonstrates a belief in environmental responsibility, while also creating greater resilience to cope with what many believe will be ever more exacting controls on the shipping industry in years to come.


The fact that it chose to announce the deal for LNG-fuelled mainliner tonnage on the occasion of the UN Climate Change Conference (COP23) gathering in Bonn last November is not without significance. CMA CGM’s track record is such that, between 2005 and 2015, the group reduced CO2 emissions per container transported per kilometre by 50%, and is now embarked on a plan to achieve a further 30% cut by 2025. 


With direct drive to the propeller, the 920mm-bore, 12X92DF ‘cathedral’ engines specified for the 22,000TEU generation will be rated for a maximum 63,840kW output at 80rpm, making them the most powerful gas and dual-fuel engines ordered to date.


The X-DF series employs the lean-burn, Otto-cycle combustion process, with low-pressure gas admission and micro-pilot ignition, as is the standard technology on medium-speed DF engines. WinGD claims that the low-pressure solution saves costs because it uses less expensive, more energy-efficient gaseous fuel compression equipment compared with low-speed DF engines employing high pressure gas injection. Liquid fuel for pilot ignition will be marine gas oil, and should account for no more than 1% of total heat release.  


Each vessel will embody an LNG fuel tank of 18,600m3 capacity, arranged underdeck beneath the ship’s forward superstructure, with the fuel to be fed to the engine room aft. The Mark III membrane system designed by GTT, the market leader in LNG carrier cargo containment, will be used for the tanks, to be fabricated under licence by Hudong-Zhonghua for all nine newbuilds.  Although the nature and integration of the bunker tanks is space-efficient, CMA CGM’s decision to incorporate the biggest LNG bunker tanks to date has meant some penalisation of cargo capacity that would otherwise be attainable within the hull envelope. 


In support of the LNG-fuelled endurance factor being built into the nascent class of ships, CMA CGM has signed a long-term, fuel supply agreement with French energy group Total. Under the pact, unprecedented in the volumes involved for a shipping application, Total Marine Fuels Global Solutions will provide LNG bunkers totalling around 300,000 tonnes per annum over 10 years, starting in 2020.


Bureau Veritas will class the vessels, which were designed under the aegis of CMA Ships Solutions. Hydrodynamics, engine and fuel specifications, tank size and other areas were all investigated and modelled before the contract was awarded to CSSC.

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