Fuel Additives

• Fuel additives have long promised significant benefits for NOx reduction, and there are sound theoretical foundations for believing that appropriate additives can modify combustion processes to reduce NOx formation.
• If the additive is water, and this is incorporated and distributed as small droplets within the fuel, these small droplets can “explode” when the fuel gets hot during injection to a cylinder, so ensuring better mixing of fuel and air, and so more controlled combustion – these are known as emulsion fuels.
• The water mixed with the oil can also be used to dissolve other additives, and sophisticated modification of combustion processes becomes possible.
• So far, there have been few large scale or commercial trials of such technologies in the marine context, but it is reasonable to expect that, with appropriate incentives, good, cost effective technologies will be marketed.

INDEPTH
To ensure the mixing of oil and water in emulsion fuels, small quantities of other additives, and it is the design and management of the additives and the mixing process that is the “black art” of fuel additives.

These fuels are also known as emulsion fuels, with proportions of water up to about 20% of the fuel volume. NOx performance is good, but there are usually some performance penalties. Many buses operate on such fuels.

The EU has started to address the complex issue of an appropriate tax for land based use of oil water mixtures.