Pyrolysis kinetics of elephant grass pretreated biomasses
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The Elephant Grass (Pennisetum purpureum Schum) was pretreated by two independent processes, through washing with hot water (W-EG) and acid solution (AW-EG) to improve its energy properties to apply it in a thermochemical process conversion into fuel. The biomasses were analyzed by proximate and ultimate analysis; and the pyrolysis kinetics, before and after pretreatments, were evaluated by the apparent activation energy (E a) for decomposition in the temperature range of greater volatile matter through the Model-free kinetics using thermogravimetric analysis data. The kinetics of the microcrystalline cellulose Avicel PH-101 was performed to evaluate the E a result of pure cellulose. The pretreatments were efficient in increasing the volatile matter and heating value, decreasing moisture and ash content, and improving its energetic power to the application in fast pyrolysis process for bio-oil production. The TG results have shown that the reduction in ash content facilitates the pyrolysis process, increasing the volatile matter and decreasing the apparent activation energy required to biomasses degradation, due to less diffusional resistances to heat and mass transfer of W-EG and AW-EG. The Avicel PH-101 showed the highest value of apparent activated energy (E a = 276.2 kJ mol−1) which could be explained by its crystallinity, suggesting that crystalline cellulose regions are less accessible to heat diffusion than amorphous regions, requiring more energy to its degradation.
KeywordsElephant grass Biomass ash Kinetics Pyrolysis Thermogravimetric analysis
Authors gratefully acknowledge the CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico) for financial support, and PPGCEP (Programa de Pós Graduação em Ciência e Engenharia de Petróleo) and LabTam/NUPPRAR/UFRN for facilities.
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