Characterization of Biogas as an Alternative Fuel in Micro-Scale Combustion Technology

Abstract

This study observes the flame characteristics of the biogas in micro/meso-scale (MSC) combustion technology, namely in a cylindrical MSC. For comparison, the fuel and combustor variations were carried out with backward-facing step size (bfs) as the flame holder in the combustor. The bfs are varied by changing the combustor's length of the inlet diameter. However, the size of the outlet diameter of the combustor is always constant to obtain a continuous combustion reaction zone. Biogas/methane (CH4), butane gas (C4H10), and a mixture of biogas-butane are used as fuel, with air as the oxidizing agent. The results showed that the type of fuel, reactant flow velocity, and equivalent ratio that occurred in the fuel variation and the bfs variation of the cylindrical msc influenced the flame characterization. Stable flame forms in the stoichiometric to rich equivalent ratio area and the medium to high reactant velocity area. The result shows that the equivalent ratio (ϕ) is 1.23 – 1.44, the flame stability limit at the combustor ratio of 0.7, and biogas fuel has low flame stability compared to butane and the biogas-butane mixture. Moreover, the flame can be stable on butane fuel in the equivalent ratio (ϕ) 0.85 – 1.43 and (ϕ) 0.86 – 1.19 for the biogas-butane fuel mixture. Furthermore, when the D1/D2 increases, the flame stability of biogas tends to be wider than when the combustor ratio is 0.7, where the equivalent ratio (ϕ) is 0.98 – 1.42. The result also shows that the flame can be stable on butane fuel in the equivalent ratio (ϕ) 0.71 – 1.43, and for the biogas-butane fuel mixture, the flame can be stable in the equivalent ratio (ϕ) 0.69 – 1.32. However, the best characterization of biogas combustion is formed in the variation of biogas treatment by mixing butane gas (biogas-butane). One of the methods used is called with a wider flame stability limit area. More varied flame visualization variations with a more widely distributed flame mode map, flame, and combustor wall temperature. The result shows that the combustor wall temperature of butane is around 225-250 °C, higher than the characterization of biogas combustion around 150 °C, where it's without mixing butane gas for the possible test ranges.