Cinética da pirólise do caroço de açaí e efeito da presença de óxido de cálcio na reação

Abstract

Supplying the growing demand for energy and ensuring the maintenance of resources and the environment is the current research proposal around the world. In Brazil, diversifying the energy matrix through renewable sources is an increasingly evident need in the country. Lignocellulosic biomasses are sources with low representation in the Brazilian matrix and are an important alternative in this search for renewable resources since their bioenergetic potential is already known. The açaí seed is a waste generated through the production of açaí pulp, which has grown considerably in recent years, generating more waste that does not have a correct final destination. The thermal treatment of this biomass for the generation of biofuels is understudied, as well as the effect of this process using metallic oxides. In this work, the study of the açaí seed (CA) biomass was done by its characterization through proximate analysis, ultimate analysis, bulk density, and calorific value in order to identify the potential for bioenergy production. The pyrolysis of the acai seed was conducted in a thermogravimetric analyzer at four different heating rates up to 900°C in order to generate data for the calculation of the activation energy (Ea) by two isoconversional methods, Flyyn-Wall-Osawa (FWO) and Kissinger-Akahira-Sunose (KAS). Pyrolysis of three mixtures of CA and CaO was performed on a thermogravimetric analyzer for one heating rate of up to 600°C in order to identify the effect of the presence of this oxide (both as a reaction catalyst and adsorbent in CO2 capture). The characterization of the açaí seed demonstrates that the biomass presents satisfactory bioenergetic potential when compared to biomasses already studied, especially when observing the value of HHV (17,403 MJ kg-1). The kinetic study showed a suitable fit of the models to the experimental data, generating good adjustments over a large conversion range. For the FWO method, the average Ea calculated was 242,41 kJ mol-1 and for KAS was 247,12 kJ mol-1, values that are close to the range found for lignocellulosic biomass in the literature. For the mixtures, it was possible to identify the mechanism of CO2 capture by CaO through qualitative comparison between the TG curves of the mixtures and pure CaO. The presence of large amounts of CaO in the mixtures negatively impacted the degradation of the sample, increasing the resistance to mass and heat transfer and masking a possible catalytic effect of CaO on the reaction kinetics.