Cold model testing of an innovative dual bubbling fluidized bed steam gasifier

Biomass gasification by a dual fluidized bed reactor is a very promising process to produce a hydrogen rich syngas from biomass wastes. In this process, the bed material circulation must be enough to transport heat from the combustor to the steam gasifier, and at the same time siphons/loop-seals must be properly designed to avoid gas leakage between the two reactor chambers (such as N2 from the combustor to the gasifier). A cold model of an innovative pilot scale dual bubbling fluidized bed gasifier (100 kWth as biomass input) has been realized. The Hybrid Lagrangian Particle Tracking (HLPT) technique and tracer gas analysis, both applied to the cold model, have been used to evaluate the flow rate of bed material circulation and the gas leakage between the steam gasification and the combustion chambers. The results have shown that the bed material circulation is 2–3 times the minimum required to assure allothermal gasification, while gas leakage is negligible for every operating condition evaluated experimentally.