composite boiler · boilers system

Alfa Laval Aalborg AQ AQ-12

The Alfa Laval Aalborg AQ-12 is a marine composite boiler, a type of boiler that generates the steam a ship needs while making use of the waste heat in the main engine's exhaust gases. Aalborg is a long-established name in marine boilers, and the composite design combines two heat sources in a single unit: an exhaust-gas section, through which the hot exhaust from the main engine passes to raise steam, and an oil-fired section with its own burner. This lets the boiler recover otherwise wasted energy while the ship is at sea and the main engine is running, and still produce steam independently in port or when the engine is stopped. Steam has many uses aboard a merchant ship even where it is not the means of propulsion. It heats heavy fuel oil and lubricating oil to the temperatures needed for pumping and for separation, warms cargo on some tankers, provides heat for accommodation and domestic services, and drives various auxiliary processes. Producing that steam efficiently matters for fuel economy, and a composite or exhaust-gas boiler does so by capturing heat from the engine exhaust that would otherwise be lost up the funnel, which reduces the amount of fuel that must be burned in the oil-fired section. In service the boiler must be operated and maintained with care. Water treatment is important to prevent scale and corrosion on the heating surfaces, the exhaust-gas side must be kept clean and guarded against soot fires, and the water level, pressure and safety devices such as the safety valves and level alarms must be monitored, since a boiler is a pressure vessel whose failure can be dangerous. The composite boiler such as the Aalborg AQ exemplifies the engineering emphasis on energy efficiency in ship design, integrating waste-heat recovery into the everyday supply of steam that keeps a ship's fuel systems, cargo and services working.