Prediction of the equilibrium compositions in the combustion products of a domestic boiler

In this study, two prediction models were developed to determine equilibrium compositions in the combustion products of a domestic boiler. These models are based on the Gibbs energy minimization and equilibrium constant methods. According to the domestic boiler standards (EN 15502–1 and EN 437), gaseous fuels (G20, G25, and NG) were selected to predict gaseous emissions. A novel investigation was realized for a domestic boiler's lean premixed burner in compliance with relevant standards. In the range of 0.6–0.9 equivalence ratio, the equilibrium compositions of the species were obtained. The proposed models were compared with CHEMKIN commercial software to verify the prediction of the results. Adiabatic flame temperatures and combustion products (NO, CO, N2, O2, CO2, and H2O) were estimated using prediction models. The estimated values showed good agreement with the results obtained from CHEMKIN software. Under efficient boiler operating conditions (ϕ=0.65, 0.7, and 0.75), minor deviations were observed comparing with the CHEMKIN results. For gaseous fuels, CO and NO emissions reach peak values near ϕ=0.9 and ϕ=0.85, respectively. Without using complex chemical kinetics mechanisms, models provide reliable estimates. The proposed models can be parametrically applied not only for boilers but also for other applications in combustion processes. •Combustion gaseous emissions and adiabatic flame temperatures prediction.•Investigation of G20, G25 and NG fuels on domestic heating boilers.•Prediction models with Gibbs energy minimization and equilibrium constant method.•Estimation of NO, CO, N2, O2, CO2 and H2O species.•Comparison with the results obtained from CHEMKIN and proposed models.