In view of the constant search for new sources of renewable energy, the particulate agro-industrial waste reuse emerges as an advantageous alternative. However, despite the advantages of using the biomass as an energy source, there is still strong resistance as the large-scale replacement of petroleum products due to the lack of scientifically proven efficient conversion technologies. In this context, the pyrolysis is presented as one of the most widely used thermal decomposition processes. The knowledge of aspects of chemical kinetics, thermodynamics these will, heat and mass transfer, are so important, since influence the quality of the product. This paper presents a kinetic study of slow pyrolysis of coffee grounds waste from dynamic thermogravimetric experiments (TG), using different powder catalysts. The primary thermal decomposition was described by the one-step reaction model, which considers a single global reaction. The kinetic parameters were estimated using nonlinear regression and the differential evolution method. The coffee ground waste was dried at 105°C for 24 hours. The sample in nature was analyzed at different heating rates, being 10, 15, 20, 30 and 50 K/min. In the catalytic pyrolysis, about 5% (w/w) of catalyst were added to the sample, at a heating rate of 30 K/min. The results show that the one-step model does not accurately represent the data of weight loss (TG) and its derivative (DTG), but can do an estimative of the activation energy reaction, and can show the differences caused by the catalysts. Although no one can say anything about the products formed with the addition of the catalyst, it would be necessary to micro-pyrolysis analysis, we can say the influence of the catalyst in the samples, based on the data obtained in thermogravimetric tests.
Spout fluidized bed has shown promising for gas-solid contact operations with and without chemical reactions, such as drying, coating, granulation, gasification, pyrolysis, etc. This is because these beds combine features from both spouted and fluidized beds. The other point is the ability to treat chemical transformations involving both heat and mass transfer in combination with particles of various sizes. Therefore, it is extremely important the knowledge of fluid dynamic of the bed, mainly for scale-up projects, which makes computer simulation an essential tool. Researches using the Computation Fluid Dynamics (CFD) proved to be very effective in predicting of particles dynamic in this type of bed. In Computation Fluid Dynamics, the two phases are treated as interpenetration continuous, and these phases are described by equations of conservation of mass, momentum and energy. The goal of the present work was to simulate using CFD experimental fluid dynamics data of a spout fluidized bed. Eight distinct flow regimes were identified which showed up in good agreement with the regime map presented in literature. The results showed that the technique was efficient for the simulation of the hydrodynamic of the bed presented.
RESUMOAtualmente, uma significativa parcela da população mundial sofre com a escassez de água. Uma alternativa à este problema é o consumo de água provinda de processos de dessalinização, como, a destilação solar, que destaca-se por usar como fonte energética a radiação solar. A proposta do trabalho é a construção de um destilador solar com cobertura piramidal utilizando materiais de baixo custo, composto por uma cobertura de vidro, assadeira de alumínio como a base da bacia, garrafas PET para coleta da água destilada. Foi construído assim, um destilador de 0,2025 m². Para efeitos de melhoria no equipamento, identificou-se a partir da análise estatística as variáveis mais significativas na produção de destilado, realizando testes no destilador a partir de um planejamento composto central. A eficiência do equipamento foi medida através da produção e qualidade da água. Ao se analisar a água destilada final, constatou-se que os valores de pH e condutividade classificam-na como apropriada ao consumo humano. De acordo com o planejamento de experimentos, obteve-se que a variável que mais influente sobre a produção de água destilada foi a profundidade da bacia, seguida da salinidade da água e espessura do isolamento. A maior produção de destilado obtida foi de 580 mL de água atingindo-se a temperatura máxima de 66 °C, na condição de mínima profundidade da bacia. Os testes mostraram que o destilador solar construído funciona adequadamente.
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