Cfd Simulation Scale-up of a Dual-fluidized Bed Gasifier for Biomass

The University of California in collaboration with West Biofuels, LCC, has developed an advanced thermochemical gasification system (5 ton/day) for the conversion of waste stream biomass for the production of bio-fuels and bio-energy. The “Pyrox” gasifier design is based on a dual-fluidized bed system operating at atmospheric pressure with air. Simulation of this gasifier was conducted with a new CFD simulation software package, SDBG (San Diego Biomass Gasifier), developed from the open source MFIX code from the National Energy Technology Laboratory as its kernel. SDBG was used to perform CFD simulation of the gasifier column reactor with its detailed geometry in full size and at 1/5 scale for two sets of mono-disperse particles of differing size and density. It is often assumed that dynamic similarity can be ensured only when the Glicksman’s full set of non-dimensional scaling parameters are kept identical. However, CFD simulations suggests that Glicksman’s much desired simplified set of scaling parameter suffices for dynamic similarity as long as the particle collision properties (particle-particle and particlewall restitution coefficient) used in continuum kinetic theory closures are kept at a critical value.