What is the impact of excess air on efficiency?
In theory, to have the most efficient combustion in any combustion process, the quantity of fuel and air would be in a perfect ratio to provide perfect combustion with no unused fuel or air. This type of theoretical perfect combustion is called stoichiometric combustion. In practice, however, for safety and maintenance needs, additional air beyond the theoretical "perfect ratio" needs to be added to the combustion process - this is referred to as "excess air".
With boiler combustion, if some excess air is not added to the combustion process, unburned fuel, soot, smoke, and carbon monoxide exhaust will create additional emissions and surface fouling. From a safety standpoint, properly controlling excess air reduces flame instability and other boiler hazards. Even though excess air is needed from a practical standpoint, too much excess air can lower boiler efficiency. So a balance must be found between providing the optimal amount of excess air to achieve ideal combustion and prevent combustion problems associated with too little excess air, while not providing too much excess air to reduce boiler efficiency. Research has shown that 15% excess air is the optimal amount of excess air to introduce into the boiler combustion process. While some boilers have been able to achieve 15% excess air at the top end of a boiler's firing range, the challenge presents itself at the lower end of the firing range, or below 60% of the boiler's maximum capacity.
In general, most boilers tend to increase excess air requirements as the firing rate of the boiler decreases, leading to lower efficiency at the lower end of the firing range. To complicate matters, most boilers operate on the lower end of the firing range - so selecting a boiler that has low excess air throughout the firing range is important. This will ensure that you are always operating at high efficiencies.
-
SZL series coal-fired steam boilerLive Chat6-35 t/h1-2.5 MPa
-
DZL series biomass-fired steam boilerLive Chat2-10 t/h1-2.5 MPa
-
SZS series gas-fired (oil-fired) steam boilerLive Chat2-110 t/h1.25-5.3 MPa
-
Email us
-
WhatsApp: +86 18861589035
WeChat: +86 13506150756
Live Chat
-
As global attention toward sustainable development intensifies, green and eco-friendly practices have become the main theme across all industries. For traditionally high-energy, high-emission sectors, technological innovation is essential to achieve clean production and unlock new growth. The plastic foam industry, a vital part of industrial manufacturing, has long faced the dual challenges of high energy consumption and environmental pressures. The emergence of biomass boilers offers a new gree...17 Jun 2025
-
With the ongoing advancement of the “Belt and Road” Initiative, economic and trade cooperation between China and Kyrgyzstan has become increasingly close. In February 2025, the two countries announced the launch of negotiations on a service trade and investment agreement, injecting new momentum into their bilateral collaboration. Against this backdrop, Chinese industrial equipment is making its way into Kyrgyzstan, helping local businesses grow—ZOZEN Boiler stands out as an exe...10 Jun 2025
-
ZOZEN Boiler Showcases Multi-Dimensional Energy Solutions at Serbia’s TOPS 2025 Scientific SymposiumFrom June 2 to June 3, 2025, the TOPS 2025 Scientific Symposium, hosted by the Serbian Heating Association, was held in grand fashion. As one of the most influential events in the European heating industry, it attracted leading international brands such as Weishaupt, Bosch, and KSB, with a collective focus on cutting-edge technologies in gas and biomass boilers. In light of rising energy costs, biomass boilers, with their outstanding cost-saving potential, became a hot topic of discussion. As th...11 Jun 2025