Processo de pirólise da torta de linhaça: efeito dos parâmetros operacionais no rendimento e caracterização dos produtos

Abstract

The aim of this work was to evaluate the thermochemical conversion of flaxseed cake as an alternative for agro industrial waste utilization, in order to obtain biofuels and compounds of higher added value. Thus, the biomass was characterized by different methodologies: the kinetic parameters of decomposition were identified by means of four isoconversional models (Friedman, FWO, KAS e Starink); the effects of temperature, heating rate e granulometry were analyzed according to the products yield; and the products characterization was also performed. The thermogravimetric tests were performed applying heating rates from 5 to 25°C min-1 on N2 atmosphere. The activation energy obtained for the activation models presented values between 171,96 kJ mol-1 e 195,69 kJ mol-1. For the tests in the fixed bed reactor, a complete factorial design (2k) utilized in order to evaluate the effects of the parameters temperature, heating rate and granulometry in the products yield. The minimum and maximum levels, respectively, for the reaction temperature were 400°C and 500°C; for the heating rate were 5°C min-1 and 15°C min-1; and for the granulometry were 0,106 – 0,250 mm and 0,355 – 0,425 mm. A matrix with 11 tests were generated, with 8 factorial points and 3 central points. The higher biofuel yield (41.90%) were identified at a temperature of 450 °C, heating rate of 10°C min-1 and granulometry of 0,250 – 0,355 mm. The compounds present in the biofuel were identified by gas chromatography coupled to mass spectrometer (GS/MS) and mainly acids and heterocyclic were observed, besides nitrogen compounds. The biochar was characterized by proximate composition presenting a high fixed carbon content. The flaxseed cake pyrolysis has generated liquid products that can be considered as important renewable sources of energy and chemical products.