The aim of this work was on the thermal characterization of wastes of the sugarcane industry, such as bagasse, filter cake and vinasse, in both forms: pure and blended. Thermogravimetric analysis (TG), derivative thermogravimetric (DTG) and differential thermal analysis (DTA) were used for the evaluation of the thermal behavior of the samples under four different atmospheres: N 2 , CO 2 , N 2 /O 2 and CO 2 /O 2 . Comparison of thermal behavior of the samples under combustion (N 2 /O 2 ) and oxy-combustion (CO 2 /O 2 ) reveals that replacing N 2 by CO 2 causes displacement of mass loss steps to higher temperatures and increases some DTG peaks. Higher heat capacity of carbon dioxide and higher partial pressure of CO 2 molecules in relation to N 2 ones explain these observations. Under CO 2 (100 %) environment, an endothermic event-due to CO release-is observed at around 900°C, which is attributed to the reverse Boudouard reaction. Interestingly, in all samples, when vinasse is present, such endothermic event starts at lower temperature (*700°C), which can be understood as a reaction catalyzed by the high potassium content in the vinasse. Synergistic effect studies indicated that bagasse improved reactivity of blends due to its higher volatile content. Since there are no reports regarding the thermal characterization of wastes of the sugarcane industry under combustion, oxy-combustion and gasification atmospheres, this work establishes an important database for the study of similar types of biomass in the field of bioenergy.
The influence of the partial pressure of carbon dioxide (CO2) on the thermal decomposition process of a calcite (CI) and a dolomite (DP) is investigated in this paper using a thermogravimetric analyser. The tests were non-isothermal at five different heating rates in dynamic atmosphere of air with 0% and 15% carbon dioxide (CO2). In the atmosphere without CO2, the average activation energies (E(alpha)) were 197.4 kJ mol(-1) and 188.1 kJ mol(-1) for CI and DP, respectively. For the DP with 15% CO2, two decomposition steps were observed, indicating a change of mechanism. The values of E(alpha) for 15% CO2 were 378.7 kJ mol(-1) for the CI, and 299.8 kJ mol(-1) (first decomposition) and 453.4 kJ mol(-1) (second decomposition) for the DP, showing that the determination of E(alpha) for DP should in this case be considered separately in those two distinct regions. The results obtained in this study are relevant to understanding the behaviour changes in the thermal decomposition of limestones with CO2 partial pressure when applied to technologies, such as carbon capture and storage (CCS), in which carbon dioxide is present in high concentrations.
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