Biomass cofiring with coal, when combined with carbon capture and sequestration (CCS), can remove atmospheric carbon dioxide (CO2) because the CO2 consumed during biomass growth is not released back into the atmosphere after combustion. Cofiring biomass with coal can also contribute to compliance with renewable portfolio standards (RPS) and the reduction of pollutant emissions, such as mercury and sulfur oxides (SOx).
The physical characteristics and composition of biomass can vary significantly. When cofiring biomass with coal, these differences can impact the structure of the volatile flame — the region where combustion of volatiles dominates. The length and location of the volatile flame are important to flame stability, and determine the location and extent of volatile release. This, in turn, has an effect on the emission of such pollutants as nitrogen oxides (NOx). Previous studies focused on the effects of parameters such as the cofiring ratio, particle size and air-fired versus oxy-fuel conditions on flame length and volatile breakthrough.
Our current work focuses on moisture variation and its impacts. Moisture content is among the more variable and difficult-to-control parameters of biomass fuels. We are analyzing the impacts of moisture content on volatile breakthrough and volatile flame length. Both parameters affect boiler efficiency. We are also performing computational fluid dynamics (CFD) modeling to analyze NOx emissions under our operating conditions.
Ultimately, we seek to gain a broad understanding of how flame structure, volatile breakthrough and NOx emissions change as we simultaneously alter operating conditions and biomass properties.