DESIGN OPTIMIZATION OF AIR STAGED COMBUSTOR GEOMETRY FOR LOW-GRADE BIOMASS PRODUCER GAS COMBUSTION

Abstract

Since industrial revolution, the supply of the needed energy depended on fossil fuel burning. Nowadays, renewable energies are getting attention for replacing fossil fuels to mitigate the raising crisis of global warming caused by greenhouse emissions. Biomass energy is one of the carbon-neutral renewable energies. However, low heating value of producer gas from biomass gasification requires longer residence time to burn. Long residence time of fuel burning brings increment of the NOx formation. Thus, staged combustion is applied to control the NOx emissions of the combustor. In this study, combustion characteristics of air staged combustor were studied. Effects of geometry manipulative variables, such as combustor diameter (D), diameter ratio (DR) of air distributor to total combustor diameters and length ratio (LR) of air distributor to total combustor lengths were investigated. The results showed combustor with smaller diameter and larger DR released less NOx gases but it resulted in higher CO emissions and lower mean outlet temperature. With the increment of LR, CO emissions raised and mean outlet temperature decreased but NOx emissions did not change much with the LR variation. Therefore, optimum chamber geometry was found to be 250 mm diameter, DR of 0.6 and LR of 0.2 to maximize the temperature at the chamber outlet while achieving acceptable CO and NOx emissions from the staged combustor.