Effects of Particle Shrinkage and Devolatilization Models on High-Temperature Biomass Pyrolysis and Gasification

Abstract

The effects of two different particle shrinkage and devolatilization models on biomass pyrolysis and gasification behavior in a high-temperature (1400°C) entrained-flow reactor have been studied employing a three-dimensional Eulerian− Lagrangian computational fluid dynamic model in the framework of open-source codes, OpenFOAM. Both qualitative results (temperature distribution, gas composition, and particle distribution) and quantitative results (pyrolysis time, syngas production, carbon conversion, and particle residence time) are presented and analyzed. Results show that particle shrinkage models significantly affect the simulation results and the constant volume model predicts a faster devolatilization rate, higher H 2 , CO, and CH 4 productions, lower CO 2 production, higher carbon conversion, and longer particle residence time than the constant density model. However, the two devolatilization models employed give consistent results on the exit syngas production and carbon conversion, although the constant rate devolatilization model predicts a faster devolatilization rate and a longer particle residence time than the single kinetic rate devolatilization model. In addition, the sensitivity of the kinetic constants for the constant rate devolatilization model is also tested. These trends are the same for both the biomass pyrolysis and gasification applications. Moreover, the predicted results are also compared to the experimental data available in the literature, and the differences resulting from different particle shrinkage and devolatilization models are highlighted.

Methodology for material property determination

“…Instead of only studying temperature, Chaos also performed the sensitivity analyses of mass loss rate (MLR) to material properties. Other studies on the sensitivity of the pyrolysis model regarding different parameters had been conducted by researchers in the past as well . In this study, sensitivity analyses were performed on both the surface temperature and the MLR for a charring material to quantify the sensitive of the input properties.…”

Overview of Computational Fluid Dynamics Simulation of Reactor-Scale Biomass Pyrolysis

“…It was found higher temperature leads to lower tar yield. The effects of particle shrinkage were studied by testing two shrinking models in the DPM simulation of biomass pyrolysis in a falling reactor 98 with Scheme A2. The results showed that the constant volume model predicts a faster pyrolysis and longer particle residence time than the constant density model.…”

Computational Fluid Dynamics/Discrete Element Method Investigation on the Biomass Fast Pyrolysis: The Influences of Shrinkage Patterns and Operating Parameters

“…As mentioned before, the particle shrinkage should be considered in the modeling of conversions of solid fuels. A pair of shrinkage models were most commonly adopted in previous numerical studies: , namely, the constant size model and constant density model. Other shrinkage patterns were also proposed or employed by researchers. , Among different particle shrinkage models, the model proposed by Di Blasi gives a comprehensive description of the particle shrinkage for biomass pyrolysis process.…”

“…As mentioned before, the particle shrinkage should be considered in the modeling of conversions of solid fuels. A pair of shrinkage models were most commonly adopted in previous numerical studies: 19,20 namely, the constant size model and constant density model. Other shrinkage patterns were also proposed or employed by researchers.…”