U.S. Department of Energy
Washington, DC. USA
Operating your boiler with an optimum amount of excess air will minimize heat loss up the stack and improve combustion efficiency. Combustion efficiency is a measure of how effectively the heat content of a fuel is transferred into usable heat. The stack temperature and flue gas Oxygen (or Carbon Dioxide) concentrations are primary indicators of combustion efficiency.
Natural Resources and Office of Energy
Typically, reducing O2 in the flue gas by 1 percent- for example, from 5 percent to 4 percent- increases boiler efficiency by about 2.5 percent.
Controlling excess air is the most important tool for managing the energy efficiency and atmospheric emissions of a boiler system.
As graph shows, the effect of air temperature on excess air in the flue gas can be dramatic.
Petroleum Conservation Research Association
If excess air ratio is too high, there will be increased heat losses in the exhaust gas. It is possible to reduces heat losses or effect Fuel saving, if the excess ratio is suitably reduced to standard air ratio. Fuel combustion efficiency is dependent on exhaust gas temperature and air to fuel ratio used in the combustion process.
Neil C. Widmer
The preferred way to address carbon combustion loses is to tune the fuel and air distribution in the furnace and balance spatial combustion conditions. The has historically been done with manual tuning services but now can be accomplished using online combustion tuning systems.
(Ex-Technical Advisor, Thermax Ltd.)
Ensuring that fuel burning appliances are set to achieve the optimum fuel-to –air ratio maximizes the safety, stability and efficiency of the combustion process, trim systems reduces energy consumption, costs and carbon dioxide emissions.
(Ex- Assistant Director, ATIRA)
Research work indicated that while solid fuel firing cannot be measured or easily controlled there is considerable scope to save fuel if combustion air can be controlled. The proposal is simple at first sight but there were a multiplicity of difficulties with took about long persistent research.
Ministry of Agriculture and Food
The fire side of the boiler is most important. The air-to-fuel ratio is critical for achieving optimum combustion efficiency. There is an optimum amount of excess air for each type of packaged boiler and fuel type. Only sufficient air should be supplied to completely combust the fuel since more than this amount increases the heat rejected to the flue.