Development of biogas combustion in combined heat and power generation

Based on the biogas feedstock and its generation cycle, a considerable part of biogas ingradients are noncombustible gases. Low calorific value (LCV) of biogas is one of the most important barriers of biogas development in the combined heat and power (CHP) generation. Biogas purification is usually performed in sensitive utilizations, however modification methods such as cryogenic and membrain are not economic. Therefore, new methods of biogas utilization should be experimented. In this study, characteristics of biogas are investigated under various combustion regimes such as biogas conventional combustion, hydrogen-enriched biogas traditional combustion, biogas flameless mode and hydrogen-enriched biogas flameless combustion. Since biogas conventional combustion is not well-sustained due to LCV of biogas, hydrogen addition to the biogas components could improve combustion stability however NOx formation increases. Although flameless combustion of fosil fuel have been developed, few documents could be found about biogas flameless mode. Flameless combustion of biogas could be one of the best methods of pure biogas utilization in CHP generation. Combustion stability and low pollutant formation are the main advantages of biogas flameless combustion. The initial cost of flameless combustion instalation is high due to the cost of instrumentation and special equipments. In order to maintain the temperature inside the flameless chamber, some especial materials such as ceramic should be utilized. Biogas flameless combustion could be modified by hydrogen-enrichment strategy. The temperature distribution inside the flameless chamber is more uniform when small amounts of hydrogen added to the biogas components and the flameless regime is more sustained. In this circumstance the rate of pollutant formation is a little higher than pure biogas flameless combustion.