Methanol as a Marine Fuel

Methanol as a Marine Fuel

Methanol is also known as methyl alcohol and its chemical formula is CH3OH. Methanol is also called wood alcohol as it was once produced as a byproduct of the destructive distillation of wood. Industrial methanol is produced in a catalytic process directly from carbon monooxide, carbon dioxide and hydrogen. Methanol is light, volatile, colorless, flammable liquid with a distinctive odor very similar to that of ethanol. Methanol is highly toxic and unfit for consumption. At room temperature, it is a polar liquid. It is used as an antifreeze, solvent, fuel, and as a denaturant for ethanol.

Methanol has the most basic molecular structure of all the alcohols. It has four hydrogen atoms, one oxygen atom and one single carbon atom. It is flammable at room temperature and burns with an almost invisible blue smokeless flame. The demands on the marine industry regarding exhaust emissions are getting stricter. At the start of the year 2015 the maximum allowed sulphur content in marine fuels used by vessels operating within a SECA will be restricted from 1,0 % to 0,1 %. Vessels that normally run on heavy fuel oil will then either have to change to a low sulphur alternative or to install a scrubber unit to lower the sulphur content in the exhaust gas. Methanol has a sulphur content of 0.5 PPM which is considerably lower than the requirements of fuels used within a SECA. The lower heating value of methanol is about half of the heating value of diesel oils and residual fuels, also the density of methanol is lower than for diesel oils and residual fuels. Methanol has previously only had very limited use on marine applications, mostly as liquid fuel cells which are producing low outputs used as auxiliary power for private boats and yachts.

The main advantages to use a fuel cell instead of a combustion engine are its low noise levels and its almost zero nitrous oxides and Particle emissions. Methanol is either produced from fossil fuels or biomass. Fossil fuels are by far the most common source of raw-material for the production of methanol. A benefit of methanol is that it can be manufactured from numerous different types of hydrocarbons. The most common source of raw material is methane found in natural gas. Methanol made from renewable hydrocarbons and carbohydrates are getting a lot of attention as an environmentally friendly fuel, especially in Europe. In Holland there is a plant which produces methanol from crude glycerine. There are safety concerns about the use of methanol in a marine environment. Methanol is flammable, has a low flashpoint and is considered toxic.

The methanol institute has released a Methanol Safe Handling Manual for methanol distributors and users. This manual covers firefighting procedures for handling and preventing a methanol fire. When comparing methanol to gasoline for the interest of the automobile industry, methanol is considered safer. This is because methanol has a lower heat release rate than gasoline, it ejects less flammable fumes and methanol vapours are more easily dispersed to the atmosphere than gasoline. IMO is currently working on a regulatory framework that will cover the use of low flashpoint fuels on-board vessels. The code will be called: The International Code of Safety for ships using gas or other low flash-point fuels (IGF Code). In 2013 the classification society Den Norske Veritas (DNV) released a new set of tentative regulations for marine vessels regarding low flashpoint fuels, which includes methanol. Methanol is difficult to ignite in an ordinary diesel engine. There are today two leading engine manufactures developing large marine engines compatible to run on methanol. The first one is Wartsila who are focused on developing four-stroke diesel cycle engines (Danbratt & Haraldson, 2013). The second company is MAN Diesel Turbo which is focused on remodelling their two-stroke diesel cycle engines to be methanol compatible.

The procedure of installing a methanol engine can be made through either building a new ship with a clean installation or as a conversion of the old engine. The conversion of the old engine is completed by replacing the cylinder head for a LGI type, adding the double walled piping, a new monitor system and installing a new ventilation system for the fuel pipes. This conversion is called retrofit and can be performed to all of the existing 2-stroke crosshead engines that MAN delivers. The retrofit will not affect the performance of the engine specification more than higher fuel consumption because of the lower heating value of methanol compared to diesel or HFO. Because methanol is a low flashpoint fuel there must be a ventilation system installed to prevent any leakage from entering the engine room atmosphere.

This ventilation system is combined with double walled piping which is installed to all piping within the engine room. If there is to be a leakage of the fuel from the primary pipe it will be leaking into the next pipe, the fuel fumes will be transported by the pipe ventilation to a gas detector. If any methanol fumes are detected the system will automatically shut of the methanol supply and switch over to full diesel operation. The price for constructing a new vessel with methanol fuelled engines is slightly higher than installing a regular diesel engine. This is mainly due to the costs for the double walled piping, inert gas system for tanks and the fuel delivery system. To retrofit a diesel powered vessel to run on methanol the cost will be about the same as installing the systems for methanol power for a new constructed ship at the shipyard.

When comparing investment costs for a methanol powered vessel and an LNG powered vessel the methanol vessel will be less expencive. This is beacuse a methanol vessel don’t need expencive high pressure fuel tanks and a very advanced fuel delivery sytem. From an environmental point of view, methanol performs well. Methanol readily dissolves in water and is biodegraded rapidly, as most micro-organisms have the ability to oxidize methanol. In practice, this means that the environmental effects of a large spill would be much lower than from an equivalent oil spill.

Toxicity of methanol:

• Methanol is not classified as a carcinogen while several of the substances in MGO, MDO and IFO are classified as carcinogens.
• Methanol is as most dangerous if ingested, it can cause blindness and death. Drinking 25 ml of methanol can be fatal.
• There is not much known about the long term effect of methanol exposure, but they are believed to be similar to the short-term effects.

The engine manufactures can supply several different types of methanol powered engines. IMO are working on guidelines and regulations concerning methanol vessels. With these upcoming regulations methanol is not considered to be more dangerous than the common marine fuels. The future price development of methanol is considered to be favourable compared to established marine fuels. The main bottleneck for restricting the use of methanol aboard vessels is the limited established logistics for supplying the vessels with fuel. Methanol is readily available worldwide and every year over 70 million tons are produced globally.

The main feed-stock in methanol production is natural gas. However, methanol could be 100% renewable, as it can be produced from a variety of renewable feed-stocks or as an electro-fuel. This makes it an ideal pathway fuel to a sustainable future in which shipping is powered by 100% renewable fuels. Methanol has been tested with positive results in heavy duty vehicles on land and is an interesting alternative fuel for shipping. Many factors point to its suitability as a viable solution to current environmental and regulatory challenges. Methanol, in common with other alcohols, provides clean burning in the engine and produces low levels of soot in combustion compared with diesel oil or HFO.  In the various tests of methanol fuel in marine diesel engines, emissions of nitrogen oxides and particulates have been very low and, being sulfur-free, methanol does not produce sulfur oxide emissions.

Characteristics of methanol as a fuel

Methanol is an nice replacement for gasoline and is used in mixed fuels, and it can also achieve a good level of performance in diesel engines. Its use in diesel engines requires an ignition enhancer, which may be a small amount of diesel oil. In all tests performed, methanol shows good combustion properties and energy efficiency as well as low emissions from combustion.

A drawback of alcohol fuels such as methanol is that energy contents are lower than for traditional fuels. Given equivalent energy density, the space needed for storing methanol in a tank will be approximately twice that of traditional diesel fuels. Methanol and LNG are similar in terms of energy density.

Regarding other emissions, sulfur is not present in methanol but may be released in small amounts in the upstream processes, depending on the energy carrier used for processing and transport. The emissions from the vessel are related to the sulfur content in the diesel quality fuels. NOx emissions are low from the engines using methane and methanol because of a low combustion temperature and well-defined fuels. In order to make a fuel attractive for shipping, there has to be an adequate infrastructure that covers a large number of ports. Bunkering of ships can be carried out by bunkering vessels as well as from land, and for both solutions there is a need for terminals that provide fuel. The infrastructure for methanol available today is based on the worldwide distribution of methanol to the chemical industry. This ensures widespread availability, although there may be a need for additional terminals for ship fuel. Within the SECAs, there are numerous terminals that serve the chemical industry. For some ports in Europe, methanol is one of the leading chemicals in terms of volume handled. Currently, bunkering of methanol fueled ships is performed by truck. The trucks deliver the methanol to a bunkering facility with pumps built in containers on the quay next to the ferry. This is a solution that is flexible and easy to build. The technology and safety precautions build on long experience from methanol deliveries for other applications.

The methanol industry is global, with production in Asia, North and South America, Europe, Africa and the Middle East. The raw material is mainly natural gas for all producing countries except China, where the primary feed-stock is coal (Seuser, 2015). Global annual methanol production capacity exceeds 100 million tons. Methanol is used for many purposes, mainly in the chemical industry; fuel accounts for around nine million tons, mostly used as blend in gasoline. The global demand in 2014 was estimated at around 65–70 million tons, out of which at least 40 million tons were used in China (IHS, 2015). Methanol is available in all major shipping hubs globally. Several new plants are under construction.

Safety and handling of methanol

Changing fuels poses new challenges to operators in terms of handling and safety. Methanol is a low flashpoint fuel, meaning that it can vaporize and mix with air to form a flammable mixture at a relatively low temperature, a fact that has to be addressed in the safety assessment. Having a low flashpoint is a characteristic that methanol shares with LNG. However, unlike LNG, methanol is a liquid at ambient temperature and pressure, meaning that it can be stored in ordinary tanks with few modifications. With regards to storage and handling, methanol shares many characteristics with HFO.

Future engine technologies

Current methanol engines are all modified from dual-fuel engines intended for HFO, diesel and gas. A limited number of engines are suitable for retrofit. The converted engines are performing well but are not optimized for the purpose. The change to methanol fuel allows construction of more efficient and smaller engines.  Several universities are developing new engine concepts for the combustion of methanol, and also other alcohols, in a diesel process. They include MIT, University of Ghent and Lund University of Technology. The production cost of methanol is dependent on the raw material and production process. The processes that produce methanol via synthesis gas can be run with many raw materials, both fossil and renewable. For renewable raw material, a difference in production cost will arise from the upstream chain, that is, raw material acquisition.Methanol is an attractive alternative from the point of view of fuel storage and bunkering infrastructure costs. Additionally, methanol is modular, allowing shipping companies to start with relatively modest investments and build up gradually as more ships convert to the fuel. As a fuel, methanol has been cost-competitive for the better part of the past five years but is currently at a disadvantage compared with low-sulfur marine gas oil.