Presently, climate change and the need to reduce greenhouse gas emissions have become a global concern among stakeholders and policymakers. Therefore, development and use of alternatives sources of energy other than fossils fuels have attracted significant attention of researchers. Among the available non-fossil energy sources, biomass stands out due to its abundance and environmentally friendly nature. Recent studies indicate that different methods have been developed to enable efficient utilization of biomass by converting it into liquid fuel. For instance, a fluidized bed reactor is widely used for fast pyrolysis of biomass. Alternatively, several numerical simulation models such as the computational fluid dynamics have been developed to investigate biomass pyrolysis in a fluidized bed under different condition. Unfortunately, the effects of the varying conditions and model parameters have not been fully explored thus leading to unreliable results. Therefore, researchers have been looking for alternatives and have identified computational fluid dynamics/discrete element method as a promising solution.
To this note, Zhejiang University scientists: Chenshu Hu (PhD student), Professor. Kun Luo, Shuai Wang (PhD student), Dr. Liyan Sun and Professor Jianren Fan from State Key Laboratory of Clean Energy Utilization investigated biomass fast pyrolysis in a fluidized bed. Additionally, they further investigated the effects of the gas velocity and particle shrinkage on the behaviors of the gas-solid phases. In particular, they developed a computational fluid dynamics/ discrete element method for simulation purposes. Their research work is currently published in the research journal, Industrial and Engineering Chemistry Research.
Briefly, the research team commenced their work by cross-examining the computational fluid dynamics/discrete element method coupling method. Next, temporal and spatial characteristics of the biomass particles were analyzed taking into consideration different conditions involving heat transfer, entrainments behavior, chemical reactions, and movements. Additionally, experimental data from literature was used to validate the simulations results.
From the simulations and experiments, the authors observed that the shrinkage patterns exhibited significant effects on the entrainment behaviors and minor effects on the product yields. The analysis also showed that after shrinkage, the entrainment velocity increased with the increase in the particle size. As a result, the constant size and constant density shrinkage patterns lead to shortest and longest residence time, respectively. Furthermore, it was worth noting that the temporal characteristics of the biomass pyrolysis were hardly affected by the superficial gas velocity specifically in terms of chemical conversion and heat transfer. However, it significantly affected the spatial properties of the pyrolysis process.
In summary, the study by Zhejiang University researchers successfully presented the use of computational fluid dynamics/discrete element methods in the analysis of the biomass pyrolysis processes thus overcoming challenges witnessed in the previous techniques like two-fluid models. Generally, the influence of model parameters and different fluidized bed conditions are uncovered. Altogether, the proposed framework offers a promising solution in enhancing the use of biomass energy as a way of reducing the dependence on fossils fuels, which is a key environment pollutant.
Hu, C., Luo, K., Wang, S., Sun, L., & Fan, J. (2018). Computational Fluid Dynamics/Discrete Element Method Investigation on the Biomass Fast Pyrolysis: The Influences of Shrinkage Patterns and Operating Parameters. Industrial & Engineering Chemistry Research, 58(3), 1404-1416.Go To Industrial & Engineering Chemistry Research