CFD modeling of date palm (Phoenix dactylifera) waste fast pyrolysis in a fluidized bed-including experimental kinetics, validation, and remarks on the modeling approach

The current estimate of worldwide date palm waste is similar to 3.8 million tons annually, with only 10% recycled and the rest discarded in landfills. This improper disposal leads to environmental concerns, including methane release and groundwater contamination. This study developed and experimentally validated a computational model of date palm waste fast pyrolysis in a fluidized bed reactor. The model employed a single-step devolatilization reaction scheme in a Eulerian-Eulerian CFD framework. The reaction kinetics were experimentally derived from thermogravimetric analysis of the feedstock and pyrolysis products. The pyrolysis was simulated at three different temperatures (450, 525, and 580 degree celsius). The impact of tar (bio-oil) thermal cracking on the pyrolysis yield was investigated using a model derived from lignocellulose biomass. At a pyrolysis temperature of 525 degree celsius, the devolatilization efficiency was 70.1%, and the predicted product composition was 41.2% bio-oil, 37.6% char, and 21.2% non-condensable gases, which closely matched the experimental findings. The mean gas residence time over the temperature range investigated was 0.38-0.45 s, falling within the recommended range for fast pyrolysis. Increasing the temperature beyond approximately 500 degree celsius decreased bio-oil yield, primarily due to the thermal cracking of tar. Remarks on the modeling approach and implementation for large-scale simulation are discussed.