Multi-scale analysis and optimization of chemical looping gasification of biomass

Biomass is a great energy resource in China, but characterized by a low energy specific content, resulting in a high investment on its storage and transport. In order to avoid this problem the pelletized biomass is intensively used in recent years. Pelletizing allow to treat compacted, dustless products with higher efficiency. The present biomass utilization model is potentially to be substituted by using biomass pellets due to the fast development of the pelletizing technology. Chemical Looping Gasification (CLG) represents a unique gasification scheme that is directly related yet notably different from conventional gasification processes. The conventional oxygen production by air separation is not needed in CLG process, which allows enhanced biomass gasification and tar reforming to syngas by using oxygen carrier with minimal energy penalty. Initiated by the leading Chinese/Germany research groups in the areas of chemical looping and particle technology, our multidisciplinary team brings together to answer critical, interrelated scientific questions in fluidization, single particle technology, chemical reaction science and reactor/process modeling, spanning from micro-scale level to reactor and process scales on the CLG technology of biomass pellets. The proposed fundamental research focuses on four aspects. Fluidization behavior (1): dynamics of bubbles and biomass pellets in the fluidized bed. Single pellet (2): the development of mechanical strength of biomass pellet during devolatilization, heat conduction inside single pellet and heat transfer between pellets and bed materials. Moreover structural modification of single pellet during devolatilization will be investigated. The single biomass pellet gasification model will be developed based on BPM (Bonded Particle Model) model. Chemical reactions (3): gasification kinetics of biomass pellets and tar reforming over oxygen carriers. Process optimization (4): with the MP-PIC (Multiphase Particle in Cell) methodology, three-dimensional Euler-Lagrangian numerical model will be developed for CLG process. The fluid dynamics of interconnected fluidized beds, pellets fluidization, single particle micro scale model, gasification and tar reforming kinetics will be coupled together to simulate the whole CLG process. It will be done with regard to the gas-solid fluid characteristics in interconnected fluidized beds and scale-up of the CLG reactors. Fundamental findings obtained from the proposed research will significantly accelerate the development and deployment of CLG for efficient biomass gasification.

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