Pyrolysis of biomass in a batch fluidized bed reactor: Effect of the pyrolysis conditions and the nature of the biomass on the physicochemical properties and the reactivity of char

This work was carried out in order to understand the effect of the pyrolysis operating conditions and the nature of the biomass on the physicochemical properties of the char and its reactivity toward the combustion. The chars were obtained by fast pyrolysis of two types of cylindrical wood particle (beech stick: diameter of 6 mm, length of 10 mm and beech bark pellet: diameter of 10 mm, length of 15 mm) under an inert atmosphere of nitrogen in a fluidized bed reactor for three different temperatures (450, 650 and 850 degrees C) and at atmospheric pressure. The ultimate and FTIR analyses revealed that an increase in the pyrolysis temperature led to a raise of the carbon content and a decrease in the oxygen and hydrogen content. At high pyrolysis temperatures, Raman spectroscopy and XRD analyses showed that the char is more and more aromatic with a large size of the aromatic rings. The different chars prepared at a pyrolysis temperature of 850 degrees C exhibited a true density close to the one of graphite. The reactivity of chars was studied by isothermal combustion at 400 degrees C in TGA. The reactivity was found to be highly dependent on the pyrolysis temperature and the nature of the biomass. An increase in the pyrolysis temperature led to a decrease of the reactivity. Besides, char from fast pyrolysis of beech bark pellet is more reactive than char from fast pyrolysis of beech stick. (C) 2016 Elsevier B.V. All rights reserved.