Numerical simulation of municipal waste and food digestate blending combustion and NOx reduction under oxygen-enriched atmospheres

Abstract

The paper aims at exploring an approach to clean combustion of municipal solid waste (MSW) with a focus on NOx emissions, in response to a global strategy for clean energy. The objective is to use an orthogonal approach to assess the NOx reduction potential of co-combustion of anaerobic food digestate (AFW) and MSW in an oxygen-enriched atmosphere. The first step is the combustion of MSW in different oxygen concentration atmospheres (21%, 26%, 31%) to find the most efficient oxygen-rich atmosphere. Three AFW blending ratios of 10%, 15% and 20% were then selected on a mass basis to investigate co-combustion with MSW. The results show that the O2/CO2 atmosphere is lower in temperature but more uniformly distributed for the same 21% oxygen concentration. Meanwhile, oxygen-enriched combustion reduces NOx emissions and decreases with increasing O2 concentration, reaching a minimum of 26.36% of NOx production under air atmosphere. As the proportion of food digestate blending increases, the gas phase conversion of N tends to decrease and then increase, reaching a minimum at 15% blending, when the temperature distribution in the furnace chamber is optimal and the outlet NOx emissions are the lowest.