Phase Transition Sorbent Intensified Biomass Gasification: Sorbent Performance, Reactor Design, and Hydrodynamic Studies

Sorption-enhanced gasification can produce hydrogen-rich syngas by in-situ CO₂ removal. However, conventional CaO-based sorbents suffer from severe degradation during cyclic operations. We proposed a new family of perovskite-based phase transition sorbents (PTSs) that can address the sorbent deactivation challenge. The PTSs showed superior stability and unique tunability for CO₂ uptake and release as well as the reaction heat for carbonation and calcination step. The resulting process has the potential to be highly efficient for biomass utilization. In order to demonstrate this novel gasification process, a cold flow model was designed and operated to study the hydrodynamics of a 5 kW_th dual fluidized bed reactor. The cold model consisted of a gasification reactor and an air reactor, both of which were operated under the bubbling fluidization regime for extended solid residence time. An overflow structure was adopted to minimize the unreacted biomass char escaping from the gasifier to the air reactor. The solids were recirculated from the gasifier to the air reactor via a riser operated under the dilute phase pneumatic transport regime. Surrogate particles (Geldart Group B) were used as bed materials to mimic the PTSs, and woody biomass powders were added to the gasifier to investigate solids mixing and the effectiveness of the overflow structure. The effects of key operating parameters, such as gas velocities and static bed height, on the gas-solid hydrodynamics were measured and discussed. Additionally, the computational particle fluid dynamic method was used to simulate the cold model and optimize the design and operating parameters. The experimental and modeling results are used as the basis to design and operate a 5 kW_th hot unit based on the PTS gasification concept.