FUEL EMULSION AS A PRIMARY METHOD TO REDUCE NOx EMISSION FROM SLOW SPEED DIESEL ENGINE EXHAUST GAS

The exhaust emissions from large marine diesel engines on ocean going vessels contains among other pollutants a significant amount of Nitrogen Oxides (NOx) wich are the main by product of combustion and they contribute to acid rain as well as the formation of harmful ground-level ozone and photochemical smog. The manufacturers of the marine vessel engines and the shipbuilders have responded to the demands to reduce vessel emissions by improving the operation of the engines and by incorporating emissions control technologies in the design of new vessels. NOx formation is suppressed by water present in the combustion chamber. Water can be introduced in various ways, for example by humidification of the combustion air or by injecting water directly into the combustion chamber, or as fuel emulsification with water. If water is evaporated inside the combustion chamber the adiabatic combustion temperature (heat load) is reduced as a result of the higher molar heat capacity of water compared to air. The lower temperature and the better fuel distribution are leading to a lower formation of NOx. This paper describes method to reduce NOx from exhaust gas of the slow speed marine diesel propulsion engine B&W-5L90MC using fuel emulsification with water. The efficiency of the fuel emulsification system was tested on engine room full mission simulator Kongsberg ERS-L11 MAN B&W-5L90MC–VLCC Version MC90-IV which is installed on Faculty of Maritime studies in Split. The results are illustrated by figures and graphs which shows approximately 20% NOx reduction in exhaust gas