Restrictions imposed by the IMO (international Maritime organization) Marine fuel bladder on the content of sulfur oxides in ship fuel are inevitably approaching. It is already obvious that the transition from high-sulfur fuel oil (3.5%) to distillate (0.5% sulfur content) will not be instantaneous around the world and will definitely add work to the sailors.
However, it is too late to make amendments (all changes are possible only through MARPOL VI); and Edmund Hughes, head of air pollution and energy efficiency at IMO, believes that 96% of vessels, mostly large sea vessels, will meet the new requirements as early as January 1, 2020.
Marine fuel bladder
Some ship owners install scrubbers on ships and will continue to use high-sulfur fuel oil; some will switch to low-sulfur fuel oil to meet the requirements. Meanwhile, there is a third way. We have prepared an overview of alternative types of marine fuel that can replace traditional fuel oil. They emit almost no SO2 and can significantly reduce emissions of other greenhouse gases.
LNG fuel for marine vessels
Scrubbers lead the way in the preparatory technology race for IMO Sulphur Cap 2020, by October 2019, 3,023 vessels were equipped with scrubbers or ordered their installation. However, in the League of alternative fuels in the first place is liquefied natural gas. As of February 2019, there were 143 LNG-powered vessels in operation worldwide, and another 135 were under construction.
The use of liquefied natural gas in a marine engine requires a moderate number of modifications. However, there are a number of advantages and disadvantages of an LNG propulsion system:
Advantages of LNG fuel
Marine fuel bladder
Liquefied natural gas is the cleanest fuel because it produces the least amount of GHG (greenhouse gases).
LNG has been used as a fuel for ships since the early 2000s, so the technology is already well established and there are many suppliers on the market. Competition also contributes to lower prices.
In addition, the cost of LNG is comparable to the price of traditional fuel. Liquefied natural gas cannot yet compete with fuel oil due to logistics and other costs; however, unlike other alternative fuels, LNG will become a full-fledged replacement for oil in the near future. According to experts, the share of LNG will reach 23% of the total amount of marine fuel by 2050 (now it is about 0.3%).
Piston engines, gas turbines and their consumables, as well as special cryogenic fuel systems for LNG are produced on an industrial scale and are freely available.
Disadvantages of LNG fuel:
LNG has a higher specific energy intensity than fuel oil, but the energy intensity per unit volume is only 43% of high-sulfur fuel oil. Therefore, fuel tanks take up 3-4 times more space compared to ships running on traditional fuel.
The problem of bunkering. The General reluctance to introduce LNG-fueled engines to the shipping industry was partly due to logistical difficulties. Liquefied natural gas for marine engines can still be found only in a limited number of ports around the world, which does not suit most players. Often ships have long routes in which the next point is not determined in advance, which means that fuel must be available at any port. Therefore, companies often take a wait-and-see attitude towards new technologies.
Methanol is a promising marine fuel
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Waterfront Shipping recently celebrated the addition of two methanol – powered vessels to the fleet. Mari Couva and Mari Kokako have a deadweight of 49,000 tons, and will use diesel and methanol, testing its capabilities as ship fuel.
In fact, CH3OH (methanol) ranks second after LNG in the ranking of promising alternative fuels. In addition, this gas has its own advantages, making it more convenient for use in the marine industry:
Methanol remains in the liquid state at temperatures from -93 ° C to + 65 ° C (at atmospheric pressure), which eliminates the need to install complex cryogenic containment systems (the cost of a fuel system using methanol is approximately 1/3 of the price of an LNG system for a marine engine).
It can be produced from natural gas, coal and renewable sources. There are technologies for producing methanol directly from harmful emissions into the atmosphere, which is the most promising in the light of reducing COx emissions.
NOx emissions depend on the type of engine used. In the case of a two-stroke diesel engine, there will be a 30% reduction in emissions (compared to high-sulfur fuel oil), while using a four-stroke engine will reduce emissions by 60%.
Ammonia is a new fuel for ships
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Dutch C-Job Naval Architects recently proposed the concept of a tanker carrying ammonia that uses its own cargo as fuel. Their research has shown that NH3 can become another alternative marine fuel option if certain safety measures are taken. The main conclusions of the study are as follows:
Solid-oxide fuel cells are the most efficient power generation technology for ammonia fuel, but there are some practical problems (low energy efficiency, engine response to load), as well as the high cost of the system, which prevents it from becoming a working model.
Ammonia fuel does not contain a carbon component, so it does not emit COx. At the same time, NOx emissions are maintained at an acceptable level, so it is a reasonable choice in terms of environmental protection.
The safe handling of ammonia on ships not intended for NH3 cargo does not require the installation of complex and expensive protective equipment (detectors, shut-off valves to isolate leaks, fuel systems with double walls, etc.).)
At the same time, there will be no problems with bunkering for ammonia fuel, since it is produced all over the world and transported through most ports.
Marine fuel bladder
H2 is another interesting alternative to marine fuel that is currently being considered. For use on ships, hydrogen is either liquefied (the cryogenic liquid has a temperature of -240° C), placed in compression tanks, or stored as a chemical compound.
Currently, H2 is produced from natural gas, as well as by electrolysis. The latter can be carried out at solar and wind power plants simultaneously with the generation of electricity. Produced from renewable energy sources, hydrogen becomes one of the cleanest fuels with zero greenhouse gas emissions.
The most efficient energy generator for H2 is fuel cells. We described hydrogen fuel cells in our article “Shipping 2030: new technologies in the marine industry”. The production of hydrogen and fuel cells is well developed, but they still remain uncompetitive in price with conventional marine engines.
Meanwhile, the port of Antwerp ordered the Hydro tug, the first H2-powered tug. They found a compromise, so the tug will use the capabilities of hydrogen and the internal combustion engine. Hydro tug boasts ultra-low emissions because it combines two-fuel technology and a sophisticated particle filter.
The tug will be built by Compagnie Maritime Belge (CMB) within two years.
Have you ever thought that ships can use biodiesel or biogas as fuel? Marine engineers in Norway and the Netherlands are developing concepts that run on biofuels from hydrotreated vegetable oil, fatty acid methyl ether (FAME) or liquefied biogas. These are mainly passenger vessels, ferries, offshore and specialized vessels.
The main component of biofuels is methane, so its behavior is very similar to the use of LNG or methanol. However, the production of bio fuel is now much more expensive.
Scientists also foresee certain problems with bunkering. Today, biofuels are only available in some ports in Norway, the Netherlands, the United States and Australia. Thus, these projects are being developed at the local level, but bio-combustible is already included in the assessment of alternative fuels DNV GL, is being actively studied and considered as a real option for alternative marine fuel for ships of the future.