MARINE DIESEL ENGINE EXHAUST GAS EMISSIONS AND CONTROL
~by Trans Marine Propulsion Systems, Inc.
Ships are an integral part of modern commercial transport, leisure travel, and military system. A diesel engine was used for the first time for the propulsion of a ship sometime in the 1910s and has been the choice for propulsion and power generation, ever since. Since the first model used in ship propulsion, the diesel engine has come a long way with several technological advances. A diesel engine has a particularly high thermal efficiency. Added to it, the higher energy density of the diesel fuel compared to gasoline fuel makes it inherently, the most efficient internal combustion engine. The modern diesel engine also has a very unique ability to work with a variety of fuels like diesel, heavy fuel oil, biodiesel, vegetable oils, and several other crude oil distillates which is very important considering the shortage of petroleum fuels that we face today.
In spite of being highly efficient and popular and in spite of all the technological advances, the issue of exhaust gas emissions has plagued a diesel engine. This issue has gained a lot of importance since 1990s when IMO, EU, and the EPA came up with the Tier I exhaust gas emission norms for the existing engine in order to reduce the NOx and SOx. Harsher Tier II and Tier III norms were later announced for newer engines. Diesel fuels commonly used in marine engines are a form of residual fuel, also know as Dregs or Heavy Fuel Oil and are essentially the by products of crude oil distillation process used to produce lighter petroleum fuels like marine distillate fuel and gasoline. They are cheaper than marine distillate fuels but are also high in nitrogen, sulfur and ash content. This greatly increases the NOx and SOx in the exhaust gas emission. Ship owners are trapped between the need to use residual fuels, due to cost of the large volume of fuel consumed, in order to keep the operation of their ships to a competitive level on one hand and on the other hand the need to satisfy the stringent pollution norms as established by the pollution control agencies worldwide.
Newer marine diesel engines are being designed to meet the Tier II and Tier III norms wherever applicable but the existing diesel engine owners are still operating their engines with the danger of not meeting the applicable pollution norms worldwide. Here we make an effort to look at some of the measure that the existing marine diesel engine owners can take to reduce emissions and achieve at least levels prescribed in Tier I. Proper maintenance and upkeep of the engine components can be effectively used to reduce the exhaust gas emission. We introduced a pilot program on diesel engine performance monitoring in North America about two years ago and it has yielded quite satisfying results for several shipping companies and more and more ship owners are looking at the option of implementing this program on their ships...Read the entire article
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