Surface stabilized combustion technology: an experimental evaluation of the extent of its fuel-flexibility and pollutant emissions using low and high calorific value fuels

Surface-stabilized combustion (SSC) is a fuel-flexible technology that extends the stability limits of lean premixed systems, while achieving ultra-low emissions of NO_x, CO and UHC (unburned hydrocarbons). To evaluate these attributes, the present study quantifies (1) operability characteristics i.e., lean blowoff limit and flashback behavior and (2) pollutant emissions (CO, N₂O, NH₃, NO and NO₂) of a commercial SSC burner when operating at a fixed fire rate on a wide range of fuel compositions. The experimental burner is the Duratherm™ ceramic-fiber burner by Alzeta Corporation. Experiments were carried out with multiple gaseous fuel blends starting with low reactivity biogas blends containing up to 65% CO₂ (by volume) balanced with natural gas, and high reactivity fuels such as hydrogen enriched natural gas (HENG) blends. The burner was able to stabilize multiple fuel compositions without requiring any modifications, which attests to the inherent fuel-flexibility of the technology. It was found that the modes of operation and flame stabilization of the SSC burner can be parametrized by the ratio of the speed of the mixture at the surface to its laminar burning velocity. The results affirm low emission operation is attainable on all fuels. In terms of nitrogen species other than oxides of nitrogen, the study found trace levels of N₂O and NH₃ (<0.1 ppm) emitted during steady state operation. However, the emission of those species can become significant during ignition and near the lean stability limit.