Open    Access



Combustion of Renewable Biogas Fuels



Author(s)

Chaouki Ghenai¹ and Isam Janajreh²

Full-Text PDF XML     1150 Views

DOI:10.17265/1934-8975/2015.10.001

1. Sustainable and Renewable Energy Department, College of Engineering, University of Sharjah, Sharjah 27272, United Arab Emirates
2. Mechanical Engineering Program, MASDAR Institute of Science and Technology, Abu Dhabi 54224, United Arab Emirates

Biogas fuel is a sustainable and renewable fuel produced from anaerobic digestion of organic matter. The biogas fuel is a flammable mixture of methane and carbon dioxide with low to medium calorific values. Biogas is an alternative to conventional fossil fuels and can be used for heating, transportation and power generation. CFD (computational fluid dynamic) analysis of the combustion performance and emissions of biogas fuel in gas turbine engines is presented in this study. The main objective of this study is to understand the impact of the variability in the biogas fuel compositions and lower heating values on the combustion process. Natural gas, biogas from anaerobic digester, landfill biogas, and natural gas/biogas mixture fuels combustion were investigated in this study. The CFD results show lower peak flame temperature and CO mole fractions inside the combustor and lower NO_x emissions at the combustor exit for the biogas compared to natural gas fuel. The peak flame temperature decreases by 37% for the biogas landfill (CO₂/CH₄ = 0.89) and by 22% for the biogas anaerobic digester (CO₂/CH₄ = 0.54) compared to natural gas fuel combustion. The peak CO mole fraction inside the combustor decreases from 9.8 × 10^-2 for natural gas fuel to 2.22 × 10^-4 for biogas anaerobic digester and 1.32 × 10^-7 for biogas landfill. The average NO_x mole fraction at the combustor exit decreases from 1.13 × 10^-5 for natural gas fuel to 0.40 × 10^-6 for biogas anaerobic digester and 1.06 × 10^-10 for biogas landfill. The presence of non-combustible constituents in the biogas reduces the temperature of the flame and consequently the NO_x emissions.

Anaerobic digestion, biogas, non-premixed combustion, NO_x emissions, CFD.