Otimização dos parâmetros do processo de tratamento hidrotérmico para obtenção de hydrochar como fonte de biocombustível sólido

Abstract

The initiative to use renewable energy sources has been promoted throughout the world, certified under the Zero Carbon policy. Therefore, there is growing interest in the development of alternative sources for the production of renewable energy, such as biomass. In this context, hydrothermal carbonization (HTC) is a promising conversion method to valorize biomass constituents. Thus, the main objective of the study was to verify the performance of Eucalyptus grandis sawdust in the production of hydrochar through HTC in simplified reactors, improving the effects of production parameters to maximize solid and energy yields. The HTC process was carried out in laboratory stainless steel reactors, where the biomass was inserted together with different solutions in a ratio of 1:10 (solid/liquid). Thus, HTC was conducted at all possible temperatures between temperatures of 150, 170, 190 and 220 °C, occurrence times of 30, 60 and 90 minutes and water solutions and concentrations of 0.1 and 0.2 mol L -1 sulfuric acid (H 2 SO 4 ). The different hydrochars produced were thoroughly evaluated, through immediate chemical, elementary and structural analyses, as well as investigations into combustion behavior and potential emissions. The optimization of process conditions was carried out using response surface methodology (RSM). This thesis was divided into two papers. The first presents the potential of the methodology used and investigates the properties of hydrochars in three different experiments, in which the concentration of H 2 SO 4 was introduced in each of them, in an occurrence time of 60 minutes and at the four temperatures mentioned above. The second investigated the influence of the three scientific variations (temperature, time and H 2 SO 4 solutions) on the characteristics of the hydrochar, in addition to proposing and validating the optimized treatment based on solid and energy yields. In general, the results indicated a reduction in solid yield from 90.72 to 43.21 %, as the temperature increased and H 2 SO 4 was added. Hydrochar produced at high temperature (190 °C) was responsible for the largest share in the increase in higher calorific value (PCS), 33 %, in relation to the PCS of raw biomass. The surface struture of the hydrochars was modified and presented abundant carbon microspheres, especially at the highest concentration of H 2 SO 4 . The optimized treatment conditions were: temperature of 185 °C, occurrence time of 30 minutes and 0.038 mol L -1 of H 2 SO 4 . These results highlight the effectiveness of the simplified methodology and reactor system, emphasizing the crucial roles of H 2 SO 4 and temperature in defining the characteristics and performance of hydrochars.