Economizer (exhaust gas boiler)

An economizer, or exhaust gas boiler, is a waste-heat heat exchanger in the main engine uptake that raises steam or hot water from exhaust gas leaving the turbocharger at about 230 to 280 degrees C. Finned water tubes recover heat that would otherwise go up the funnel, supplying the ship’s steam services and, on larger plants, a steam turbo-generator in a waste heat recovery system. Gas-side fouling by soot lowers heat transfer and raises the soot fire risk, so soot blowers clean the tube banks in service. Outlet temperature must stay above the acid dew point to limit cold-end sulfuric acid corrosion.