Comprehensive Assessment of Particle-Scale Modeling for Biomass Pyrolysis: One-Dimensional versus Three-Dimensional Models

Abstract

The present work examines the impact of the dimensionality of single-particle models (SPMs) for the pyrolysis of thermally thick biomass particles. It builds up comprehensive one-and three-dimensional SPMs and assesses their performances to gain a systematic understanding of the accuracy of predicted results, predictive capability, and computational costs. Cylindrical wheat straw pellets with an average size of 10 mm length and 7 mm diameter were studied on their pyrolysis performances at temperatures ranged from 200 to 700 °C. It investigates the correlation between the inner heating rate of the particle and the resulting irregular porosity distribution in the pyrolyzed particle. The predictions of the models are in good agreement with the experimental measurement, and they show that the predicted char yield is not sensitive to the model dimensionality; however, the rate of mass loss and the char porosity are sensitive to the model dimensionality. Additionally, the three-dimensional SPM is found to be compatible with a wider range of biomass types. The model captures a higher heating rate at the surface and at the center of the particle compared to the region in between. This is linked to an uneven porosity distribution in the pyrolyzed particle, which is higher at the surface and at the center of the particle. While the three-dimensional SPM provides a small improvement in the prediction of the temperature profile compared to the one-dimensional model but offers additional details (e.g., temperature distribution, heating rate, and porosity distribution inside the particle); it requires significantly greater computational times, which might not be justifiable in many situations.

Three-Dimensional Simulation of the Pyrolysis of a Thermally Thick Biomass Particle

“…Figure 2a shows the temporal evolutions of the temperatures at the particle center and the interior position 2 mm away from the surface, in which the current predictions are compared with both the experimental and 3D simulation results reported in the literature. 40 The current simulation results are generally consistent with the experimental data, although some local deviations are also discerned. Furthermore, at the interior position 2 mm away from the surface, our predictions seem to perform better than the 3D simulation of Marti ́-Rossellóet al 40 In addition, Figure 2b presents the comparison of the normalized particle mass during pyrolysis.…”

“…40 The current simulation results are generally consistent with the experimental data, although some local deviations are also discerned. Furthermore, at the interior position 2 mm away from the surface, our predictions seem to perform better than the 3D simulation of Marti ́-Rossellóet al 40 In addition, Figure 2b presents the comparison of the normalized particle mass during pyrolysis. Note that the normalized particle mass is defined as the ratio of the instantaneous particle mass m t to its initial value m 0 .…”

“…Note that the normalized particle mass is defined as the ratio of the instantaneous particle mass m t to its initial value m 0 . In general, the predictive accuracy of the current model is comparable to the referred 3D model of Martí-Rosselló et al, which is much better than that of the 1D model.…”

“…Second, the pyrolysis experiment of a cylindrical wheat straw particle is employed to evaluate the model. 40 In the experiment, the particle has a diameter of 7 mm, a height of 10 mm, a density of 780 kg/m 3 , and an initial temperature of 343 K. It is fixed in a tubular reactor with an ambient temperature of 973 K. The computational domain is discretized into 24,128 cells, and the biomass particle is composed of 3542 cells. Figure 2a shows the temporal evolutions of the temperatures at the particle center and the interior position 2 mm away from the surface, in which the current predictions are compared with both the experimental and 3D simulation results reported in the literature.…”

“…Second, the pyrolysis experiment of a cylindrical wheat straw particle is employed to evaluate the model . In the experiment, the particle has a diameter of 7 mm, a height of 10 mm, a density of 780 kg/m 3 , and an initial temperature of 343 K. It is fixed in a tubular reactor with an ambient temperature of 973 K. The computational domain is discretized into 24,128 cells, and the biomass particle is composed of 3542 cells.…”