Kinetic modelling of biomass torrefaction as a pre-treatment for gasification

Bruno Filipe Bandarra Campos

Key information

Authors:

Bruno Filipe Bandarra Campos (Bruno Filipe Bandarra Campos)

Supervisors:

Miguel Abreu de Almeida Mendes (Miguel Abreu de Almeida Mendes); Raquel Inês Segurado Correia Lopes da Silva (Raquel Inês Segurado Correia Lopes da Silva)

Published in

12/09/2021

Abstract

Biomass presents some obstacles regarding its usage, such as the moisture content, low bulk density, low calorific value, high volatile and oxygen contents, and its fibrous nature can create challenges to store, transport and efficiently convert biomass into fuels and other products. Torrefaction has the potential to improve biomass properties acting as a mild heat treatment in the temperature range of 200-300 ºC under inert atmosphere inducing partial decomposition of the organic biomass components. The literature, focused on experimental studies, shows that torrefaction reduces the moisture content, confers hydrophobicity, biochemical stability, higher energy density and high grindability of biomass. It is well known that the kinetic modeling of biomass torrefaction is essential to define the progress of the decomposition-reaction paths and to evaluate the dependence of the rate of progression on process parameters, especially in regards to kinetic mechanisms that are able to predict release rate profiles, product yields and the product speciation, focused on the torrefaction uses. Therefore, the developed works consists of adapting a torrefaction kinetic scheme. These adaptations consist on adjusting two tunable parameters, correction of kinetic parameters and molar coefficients of specific species, in order to provide better results for a sample of nuthell, resultant from agricultural residues. It was compared against experimental data the product yields and gas composition. The implemented model, despite having a relative error of 30 %, it is the one with better predictions. The kinetic model, after the adaptations, presented an improvement of 20 % against the pre-modified kinetic scheme.