EconomizerAs mentioned earlier, the economizer is more or less thesame as an exhaust gas boiler except it doesn’t have itsown steam chamber but uses the one in the boiler.Talking economizers, there are normally twodifferent ways of mounting depending whether it isinstalled on a land-based or marine-based boiler.On the boiler located on land we use the boiler’s fluegas as shown on the sketch. The water circulatedabove the economizer is normally supplied by themain feed pump, but can also be fitted with its owncirculation pump, see Fig. 11 on the following page.The chimney will also include a bypass to allow wastegases to pass the heat exchanger.BaffleBaffleFlangesSteamCondensateWater outletWater inlet To ejectorvacuum systemBaffleFlangedcoverplateTube sheet Tube sheetFig. 10: CondenserDeaeratorBoilerBurnerFeed pumpCondensateSteamEconomizerexhaust frommain engineexhaustto funnelDeaeratorSteamCirculationEconomizerBoilerBurnerFeed pumpCondensateexhaust frommain engineexhaustto funnelFig. 11Fig. 12 14 15grundfos boiler feed manual grundfos boiler house componentsThe economizer on marine boilers differs from theland-based boilers because it is installed in the funnelon the main engine as waste gases released from thatsource are significantly greater. Energy produced bymarine applications often allows for the generation ofoverheated steam fed directly from economizer andout into the piping.Referring to the illustration in Fig. 12, the circulationpump has to be sized to the pressure and temperaturein the boiler, which may easily be 20 bar and 170°C.Because of this, pumps featuring air-cooled top andbearing flange may be required. The pump does notnormally need to be capable of delivering a high differential pressure as it only has to overcome the pressure loss in the pipe heat exchanger (the economizer).When installing an economizer it is very importantto monitor, that the flue gas temperature in the economizer, ducts or chimney does not drop below thedew point temperature. If the flue gas condensatesand the fuel contained any substances that turn intoacids, the condensate will become very aggressiveand possibly corrode the parts in contact. If condensation of flue gases is desired in order to reach higher thermal efficiency, please take contact to the fuelsupplier for chemical analysis, and select materials forthe parts, that can handle the acids