Silica nanoparticle formation and deposition during biomethane combustion

Abstract: A fundamental investigation on silica (SiO2) nanoparticle formation and subsequent deposition during siloxane-containing biomethane combustion is undertaken using computational fluid dynamics for the first time. Silica formation is modelled using the population balance equation with the Method of Moments, considering the realistic effects of nanoparticle growth in a biomethane flame. By replicating real-world appliance conditions, particle deposition is analysed based on thermophoretic deposition characteristics. The simulations are performed for siloxane concentrations ranging from 0.23 to 264.0 mg Si/m3. The numerical results are validated against an in-house sectional population balance code. The results indicate that silica deposition on a relatively cold surface depends on the temperature gradient and is independent of particle size. The deposition layer thickness and mass grow non-linearly with siloxane concentration. The findings help inform biomethane quality standards regarding siloxane concentration limits, promoting the safe utilisation of biomethane in various gas appliances. Keywords: Biomethane, Siloxane, Silica nanoparticles, Computational fluid dynamics, Population balance modelling, Thermophoretic deposition