Transcripción del resumen del autor. A modeling study is conducted on blends of CH4 and CO2 simulating biogas from digestion plants or landfills to compare predictions from four nonsooting counterflow diffusion flames and to examine their thermal and chemical structure. Four flames, involving simulated biogas highly diluted with N2 in the fuel stream, have nearly identical strain rates (a 134 s-1) and stoichiometric mixture fractions (zf 0.76) but different CO2 mole fractions (0, 0.069, and 0.15). Profiles of major and critical minor species as well as some radical species are compared. Chemical and thermal influences of biogas CO2 content are evaluated. Quantification of the chemical influences of biogas CO2 content is vital because results demonstrate that through these effects CO2 dilution reduces emissions of NOx and greenhouse gases even without flame temperature reduction. CO2 dilution produces a reduction in the peak of acetylene, which is an important soot precursor. Without any flame temperature reduction, a typical digestion plant biogas with a mass flow rate nearly three times larger than pure CH4 gas may reduce NO and NO2 peaks by 25%. Biogas reduces the net release of three greenhouse gases: CO2, CH4, and N2O. A carbon dioxide emission index, EICO2, quantifies the ratio of the mass of net CO2 emitted to the mass of CH4 burned. The flame with typical landfill biogas proportions of CO2 and CH4 has the lowest EICO2, whereas the flame burning pure CH4 has the highest EICO2.

6