The objective of this thesis is the study of the influence of char properties on its reactivity of oxidation and gasification under different atmospheres, including air, carbon dioxide and water vapor.
To modify the properties of the chars, the conditions of the pyrolysis process were varied: initial material used, final temperature of the pyrolysis process and composition of the atmosphere in the pyrolysis process.
As for the initial material, we used: oak wood, beech wood, oak wood doped with iron (II) sulphate (FeSO4), oak wood doped with potassium hydroxide (KOH) and almond shell. The chars were produced by pyrolysis at temperatures of 450 and 500 °C in atmospheres of N2, H2O y H2O+N2.
This thesis focused on the study of the reactivity of these chars, which was carried out by thermogravimetry. The first step was to determine the experimental conditions that would ensure a kinetic regime in thermogravimetric experiments, that is, the absence of transport limitations both external and internal. This is a fundamental step since if there are transport limitations the reactivity studied will not correspond to the thermochemical process investigated (oxidation and gasification), but to physical transport processes. For this, two types of experiments were carried out: oxidation up to 600 °C with a char of known reactivity at a constant heating rate, varying the air flow and the amount of initial mass used; and gasification experiments at 900 °C (isothermal) in an atmosphere of carbon dioxide (CO2).
Next, the reactivity of the different chars was characterized using the experimental conditions previously defined. The oxidation reactivity was measured in an air atmosphere up to a temperature of 600 °C under a constant heating rate. The gasification reactivity was determined in a CO2 atmosphere at 900 °C (isothermal experiments). In some cases, it was necessary to vary these conditions to analyse more complex chars. This will be presented and discussed in more detail throughout the thesis.
This work was carried out in the context of a major research project in the Multi-phase reactive flows group, part of the Chair for Energy Process Engineering and Conversion Technologies for Renewable Energies of the Technische Universität Berlin.Outgoin
