Methanol, also known as “wood alcohol” as previously was made by pyrolysis of wood, is produced from various feedstocks, but natural gas is currently the most economical method. It is worldwide available as a marine fuel, cost effective and significantly reduces emissions of sulphur oxides, nitrogen oxides, CO2 and particulate matter.
Methanol is a biodegradable, water soluble, clear liquid with the chemical formula CH3OH, is the simplest alcohol, containing the least carbon and the most hydrogen of any liquid fuel. It is a liquid at atmospheric pressure that ranges between 176 and 338 K (–93°C to +65°C), making storage less expensive than LNG, H2, and NH3. Because of its density and lower heating value (19.5 MJ/kg), methanol necessitates approximately 2.5 times larger fuel tanks than MGO per energy unit, and similar or smaller fuel tanks than LNG.
Methanol has a good combustion, a good energy efficiency and low emission, but to be used in diesel engines requires an ignition enhancer which is a small amount of diesel oil. There are other approaches as well, like glow plug ignition which enables the compression ignition engine to run solely on methanol, without requirement of a pilot fuel to serve as the ignition source. Another solution, especially as a retrofit option is to introduce methanol into engine’s intake ports by adding a low-pressure methanol fueling system and port fuel injectors.
MAN B&W ME-LGI 2stroke dual fuel engine can run on methanol, fuel oil, marine diesel oil, ammonia or gas oil and they have the ability to achieve Tier III NOx standards (2-4 g/kWh) without after-treatment.
The new injection concept enables the exploitation of more low flash point fuels such as methanol, ethanol and LPG and the engine ability to run on these sulphur-free fuels offers great potential for ship operation within SECA zones.
Since the LGI is an add-on to the electronically controlled ME engine, converting an existing diesel engine into a dual-fuel engine capable of using both diesel and, for example, methanol is possible. The diesel fuel system is not majorly changed compared to a standard ME engine. As is the case for the ME-GI, the ME-LGI fuel system can change over to fuel mode, burning diesel oil or HFO from one stroke to the other without any limitation in speed or load.
Methanol is hygroscopic which means that will absorb water vapours directly from atmosphere, which will dilute its fuel value. Also, it contains soluble and insoluble contaminants and chloride ions which have a large effect on the corrosivity by chemically attack of metals causing pitting and by increasing fuel conductivity which leads to electric and galvanic corrosion.
Moreover, methanol is toxic in high concentrations as ingestion of 10 ml can cause blindness and 60-100 ml can be fatal. Due its volatility it is not necessary to be ingested to be dangerous since the liquid can be absorbed through the skin and vapours through the lungs. Methanol is much safer when is blended with ethanol.
Same as for ammonia, the use of methanol will lead to major changes in engine room, as the entire treatment of HFO will disappear (settling tanks, purifiers, heaters, booster pumps, viscometers, filters etc.), but new system will need to be installed specific for methanol use.