from natural gas-fired boilers are flue gas recirculation (FGR) and low NOx burners. In an FGR system, a portion of the flue gas is recycled from the stack to the burner windbox. Upon entering the windbox, the recirculated gas is mixed with combustion air prior to being fed to the burner. The recycled flue gas

⇔ Airflow and flue gas flow is slightly lower or about the same. Natural gas boilers operate at lower excess air (O2) and a different airflow requirement for stoichiometric combustion. Coal fired boilers normally operate with 3-3.5% O2 (about 20% excess air). Whereas natural gas boilers normally operate at 1-1.5% O2 (about 7% excess air).

Combustion of standard fossil fuels (natural gas and ASTM Grade Oil) in commercial and industrial boilers results in the following nine emissions; carbon dioxide, nitrogen, oxygen, water, carbon monoxide, nitrogen oxide, sulfur oxides, volatile organic compounds, and particulate matter.

Early boilers provided this stream of air, or draught, through the natural action of convection in a chimney connected to the exhaust of the combustion chamber. Since the heated flue gas is less dense than the ambient air surrounding the boiler, the flue gas rises in the chimney, pulling denser, fresh air into the combustion chamber.

Optimal content of carbon dioxide - CO 2 - after combustion is approximately 10% for natural gas and approximately 13% for lighter oils. Normal combustion efficiency for natural gas at different combinations of excess air and flue gas temperatures are indicated below:

Gas boilers may feature electronic or piezoelectric igniters.The former is more convenient, because it ignites fuel in the combustion chamber without any direct human involvement; in the latter case, one has to press a button to launch a device.; Gas-fired condensing boilers are a new type of autonomous heating equipment for homes and apartments. They boast high efficiency – much higher than ...

Boiler combustion is the study of how fuels are burned in boilers that heat water for steam. There are many applications for steam boilers, including chemical process heating, steam heat for buildings and hot water, and steam to drive electrical turbine generators. Combustion is the reaction of ...

combustion in boilers 1. Combustion Theory Lecture 12 Combustion in Boilers 2. Learning Outcomes 1. Overview of general boiler designs and applications – Heat balance/heat transfer/ heat availability/excess air/size and shape of the combustor – Boiler configurations: Smoke tube (Fire tube) and water tube/ Water wall designs Natural Circulation and Forced Circulation 2.