Wärtsilä and Marioff, agreed early this year to co-operate in the area of emission control technologies for reciprocating engines. According to the agreement Wärtsilä will take care of the engine optimization, while Marioff will provide all water-related technologies, i.e. nozzles and water systems.
The Direct Water Injection system, one of the technologies promoted by Wärtsilä, cannot be used for very low NOx because the evaporation of the water in the combustion space will reduce combustion energy. In order to achieve the lowest NOx values it is required to evaporate the water before it enters the combustion space.
The Marioff’s Hi-Fog technology allows formation of very small water droplets. When the water in this form is introduced directly after the turbocharger in an environment of more than 200 degrees C and more than 75 m/s air velocity, the small water droplets will evaporate very fast. Evaporation of water requires substantial energy, therefore additional energy is introduced via the charge air cooler, which in this case is working as an air heater. This results in a combustion air saturated with water. Experiments have shown that it is possible to reach a NOx level of less than 3 g/kWh with this system from an initial value of 10-15 g/kWh.