Fragmentation Effect on Batches of Pine Wood Char Burning in a Fluidized Bed

Abstract

Batches of Pinus pinea char particles with average diameters of 2.2, 2.8, and 3.6 mm were burned in a bubbling fluidized bed at temperatures of 600, 700, and 750 °C, with a velocities ratio U/U mf = 9. The results show that only primary fragmentation occurs with an average fragmentation ratio of 1.5. No effect of the secondary fragmentation phenomena is observed. The increase in the number of particles in the bed because of fragmentation is accounted over the burning time, and its effect is evaluated on the determination of the global combustion resistance.

Considerations on Experimental Studies of Vegetable Char Combustion in Fluidized Bed

“…For the sake of simplicity, results for only two of the tested sizes, 1.8 and 3.6 mm, are shown, but for all tested sizes the trends are equal. The shape of the CO 2 concentration curves also shows that there is primary fragmentation and absence of secondary fragmentation, phenomena which are discussed elsewhere (Rangel and Pinho, 2010).…”

“…Elutriation is out of the question as an explanation for the low carbon recovery rate, as the fragmentation phenomenon occurring with this type of char does not lead to elutriable particle sizes (Rangel and Pinho, 2010). Table 1 also shows densities and proximate analysis for the studied particles.…”

Simple Methodology To Quantify the Fragmentation on Batches of Char Pellets During Fluidized Bed Combustion

“…The real explanation is not a lower combustion resistance but an increase of the overall surface area of reactant particles. Because this increase was not taken into account, its influence was translated into a decrease of the overall combustion resistance. , Therefore, the next step is to take into account the influence of the fragmentation process on the overall surface area of particles available for the reaction and re-evaluate the experimental data, in the case of fragile particles, by comparing the corresponding Sh and k c to those obtained with the stronger particles.…”

“…The secondary fragmentation is the result of the internal structure of the particles. Thus, this type of fragmentation is mainly caused by the physical shocks that occur between coal particles during combustion. , …”

“…Rangel and Pinho and Pereira and Pinho have studied the importance of the fragmentation phenomenon in biochar combustion using a fluidized bed. Both studies used the interrupted combustion method, which is a time-consuming method with high complexity.…”