A water tube exhaust gas boiler with forced water circulation designed for heat recovery from engine exhaust gas. The boiler is used in connection with one or more oil fired boilers which act as steam/water space. Water at saturation temperature is pumped from the oil fired boiler(s) into the exhaust gas boiler by the circulation pumps. In the MISSION™ XW boiler, heat from the engine exhaust gas is transferred to the water side by convection. The generated steam/water mixture is then discharged into the steam space of the oil fired boiler(s) where the heavier water particles separate from the steam.
The heat transfer surface is build up of vertical registers which consist of horizontal finned double steel tubes. The tube registers, including tube bends and tube supports, are placed in the exhaust gas flow. The design of the tubes gives an effective compact heating surface and prevents vibration from exhaust gas pulsations. The heating surface can be cleaned easily by means of soot-blowers. The cleaning medium is either compressed air or steam.
The boiler requires a continuous forced circulation of water through the boiler as dry running would seriously increase the danger of a fatal soot fire. The forced circulation must be provided by at least two circulating pumps. One pump must be kept in continuous operation (also in port) and the other one in automatic stand-by operation mode.