Study of agglomeration in fluidized bed gasification of biomass using CPFD simulations

Fluidized beds have been widely applied for gasification of biomass. However, at high temperatures ash melting and subsequently bed agglomeration may occur. When biomass is used for thermal conversion processes, inorganic alkali components present in the biomass fuels can be responsible for major problems. Understanding the ash melting and agglomeration in various gasification temperatures is crucial to optimize the design and operation conditions of a fluidized bed gasifier. This study focuses on the ash melting and the agglomeration process in a bubbling fluidized bed biomass gasification reactor. Using standard techniques, ash-melting analyses were performed to determine the initial agglomeration temperature in laboratory prepared ash samples from woodchips from Austria. Computational Particle Fluid Dynamic (CPFD) simulations were carried out using the commercial CPFD software package Barracuda Virtual Reactor (VR). The results show that the fluid dynamics gives important indications of unwanted agglomeration processes in a biomass gasification in a bubbling fluidized bed.