ASHRAE ST-16-012

Abstract

Scope: Optimizing the combustion performance and reducing emissions of methane gas by varying excess air has been and continues to be an area of interest for researchers, manufacturers, and operators of equipment such as gas-fired boilers, with the aim of developing more energy-efficient systems and addressing ever-growing environmental concerns. Results were graphically displayed and discussed, illustrating the effects of excess air on the combustion process with regards to energy, temperature, and pollutants. Easy-to-use equations were developed with guidance on how to accurately optimize combustion. Methodology: Numerical software tools were used in analyzing injected methane gas and variable excess air ratios. Emissions such as carbon dioxide (CO2), carbon monoxide (CO), and nitrogen oxides (NOx) were also recorded and analyzed. Optimum energy output was investigated in relation to excess air and emissions. Results were tabulated and graphs generated. Equations were derived using industry-established software tools. The accuracy of the developed equations was assessed on statistical basis. Discussions on advantages and disadvantaged on excess air are included. Conclusion: Results were found to be in agreement with published official information. Precise control of excess air can improve energy efficiency and lower pollution levels in the flue gas. The developed equations can easily be programmed into a computer-controlled combustion system. Results in this paper can be also be used to assess similar existing processes. Once the computational fluid dynamics (CFD) model is set up, the model can be adjusted to suit specific simulation requirements.