Impact of flame confinement with inert ceramic foams on the particulate emissions of domestic heating systems

• Published in: Fuel (Guildford) 2021-11, Vol.304, p.121264, Article 121264
• Main Authors: Ciria, Desirée, Orihuela, María Pilar, Becerra, José Antonio, Chacartegui, Ricardo, Ramírez-Rico, Joaquín
• Format: Article
• Language: English
• Subjects: Air flow; Air-fuel ratio; Biomass; Biomass burning; Biomass energy; Cell density; Combustion; Combustion chambers; Confinement; Decomposition; Domestic heating; Emissions control; Feed rate; Flame confinement; Foams; Fuel mixtures; Heating systems; Mitigation; Particulate emissions; Particulate matter; Particulate matter emissions; Porous materials; Solid biomass combustion; Temperature distribution; Temperature profiles; Thermal decomposition
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2021.121264

•High mortality rates associated with particulate emissions are a worldwide concern.•Solid biomass combustion systems are among the main sources of particulate emissions.•Ceramic foams are effective PM abatement systems when placed as filters over the flame.•Flame confinement contributes to homogenise the thermal field in the combustion bed.•Improving the thermal decomposition process of biomass reduces particle emissions. Small solid biomass combustion systems are among the main contributors to the global particulate emissions share, and cheap, efficient abatement systems are not yet available for them. The placement of inert porous material to confine the combustion region is being recently explored as a possible mitigation system for this kind of pollution. However, given the complexity of biomass thermochemical decomposition processes, it is challenging to justify the performance of these systems on the basis of a physicochemical understanding. A foundational experiment-based study is carried out in this work to understand how combustion confinement affects the particulate emissions production mechanisms. A combustion unit was designed and built to systematically test ceramic foams with different porosities: keeping constant airflow and fuel feed rates. A comprehensive characterisation study was carried out on the solid biomass fuel, the temperature profile, the particulate emissions, and the remaining solid residue. The results evidenced that the use of foams has a substantial impact on the temperature distribution in the combustion chamber. The higher the cell density of the foam, the higher and more homogeneous are the temperatures reached in the combustion bed. This fact improved the thermal decomposition process of the pellets due to a better air-fuel mixture, leading to a reduction of the solid particulate matter emissions by more than 70%. These findings suggest that the use of an inert porous material above the combustion region might be a feasible solution for particulate emission control in small-size biomass combustion technology.