Air Heater Efficiency

CleanAir has the experience and capabilities to conduct air heater efficiency testing in accordance with accepted industry protocols (ASME PTC 4.3). By determining the average inlet and outlet concentration of either flue gas excess oxygen (O2) or carbon dioxide (CO2), the air in-leakage into the system can be calculated.

The temperature of the flue gas leaving the airheater (which is the final heat exchange element in the boiler) has a direct influence on the station efficiency. For example, a 70 ºF increase in this temperature could result in a 0.5% decrease in station efficiency.

There are many causes of an increase in this temperature, all to do with reductions in energy absorbed from the hot gas in or after the furnace. The most usual problems are:

  • fouling of the external heat transfer surfaces of the furnace, superheaters, reheaters and economizers - many of these surfaces have to be regularly cleaned using jets of steam. This "soot blowing" wastes the steam, so the extent of soot blowing is always a compromise between the reduction in efficiency caused by soot blowing and increase in efficiency resulting from cleaner heat transfer surfaces;

  • fouling of the internal heat transfer surfaces of the furnace, superheaters, reheaters and economizers caused mainly by incorrect chemistry of the water and steam in these tubes; or by incorrect material selection of the tubes; or by the tube material overheating; or combinations of these; and

  • fouling, corrosion/erosion and blocking of airheater elements.