Kássia Graciele dos Santos

Pyrolysis of Sugarcane bagasse: A consecutive reactions kinetic model from TGA experiments

The pyrolysis kinetics of sugarcane bagasse in nitrogen flow was studied by thermogravimetric analysis from room temperature to 1173 K at different heating rates (1.5, 3, 5, 10, 15, 20, 30 and 50 K/min). As there are three distinct devolatilization peaks in the DTG curve, each peak was associated to thermal decomposition of an individual biomass subcomponent (hemicellulose, cellulose and lignin). The kinetic model adopted was a consecutive reactions model. The kinetic parameters of the pyrolysis process, such as activation energy and pre-exponential factor, were calculated by least squares non-linear method and Scilab are used as the simulation tool. The simulated results showed a good agreement with the experimental data and the parameters found are similar to reported by the literature.

Isoconversional Kinetic Analysis of Pyrolysis of Sugarcane Bagasse

This paper presents a kinetic study of pyrolysis of sugarcane bagasse from dynamic thermogravimetric experiments (TG). The methods of Kissinger, Ozawa, Starink, Kissinger-Akahira-Sunose and Friedman were used to estimate the activation energy. These methods consider the temperature shifts with increase of heating rate for a given conversion in dynamic TG tests. The activation energy values obtained by the isoconversional methods were in a range 182.8 192.4 kJ·mol-1, values very close to the other biomasses presented by literature.

Characteristics of the Milk Powder Particles Lecithinated

The process of adding soy lecithin to milk (lecithination), followed by the agglomeration stage and drying, are the goal to increase the powder dispersion in water. This work studies the physical characteristics of milk lecithinated by the addition of raw and clarified lecithins with hydrogen peroxide, which was dried by lyophilization. The main objective was to compare the behavior between the particles of powdered milk, added 0.4% (w/v), 0.8% (w/v) and 1.0% (w/v) lecithin raw and clarified. The amount of added soy lecithin was determined on the basis of dry matter content of the full UHT milk used in the experiment. Lecithinated of fluid milk samples were put on aluminum forms and frozen by contact with liquid nitrogen and were placed inside the lyophilizer chamber. The lyophilization stage was carried out for approximately 7 hours under vacuum of 460 mmHg and temperature of -38 ° C. Dried samples were fragmented in porcelain pestle and kept in oven at 40°C until analyses. The powder milk added with lecithin clarified had shorter wettability to the concentration of 1.0% (w/v), the lowest percentage of retained insoluble after solubilization in water and the micrographs of the powder showed that most adding more clarified formed lecithin agglomerates of the milk powder added lecithin raw. So, the lecithin clarified give improvements in the particles for the milk added.

CFD Simulation of Spouted Bed Working with a Size Distribution of Sand Particles: Segregation Aspects

Spouted bed simulations are usually performed using only one granular phase with a mean particle diameter representing the entire particle mixture, instead of a particle size distribution. In this study, the effect of the particle size distribution is accounted through the simulation of a mixture with five granular phases. The results showed that the particle segregation occurs. Larger particles are more concentrated in the upper region, while the smaller particles are preferably positioned in the lower region of the bed. Computational simulation using CFD method reproduced well the segregation experiments with different participle sizes of sand.

CFD Simulation of Different Flow Regimes of the Spout Fluidized Bed with Draft Plates

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.

Global Reaction Model to Describe the Kinetics of Catalytic Pyrolysis of Coffee Grounds Waste

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.

Bioproducts from the Slow and Fast Pyrolysis of Sugar Cane Bagasse

In this work, it was done a series of analysis in different conditions of the pyrolysis process to verify the difference of the composition in each one of the final products. In the case of the slow pyrolysis the heating ratio varied among 1.5, 20, 40 e 50 °C/min, and analyzed for each of these rates the composition of the final product. For the case of the fast pyrolysis, the temperature varied among 350, 400, 450, 500, 550 °C, maintaining the other conditions of the process constant, in the end of the process analyzed the composition of the final product for each temperature. For the verification of the composition of these products, they were classified and separate in categories according to the functional group, and after that, the ones who had the most relevant quantities were more deeply analyses to verify some important characteristics and the main industry applications. After this, it was determined the ideals conditions of slow and fast pyrolysis. The resulting products were analyzed by gas chromatography/mass spectrometry. For slow pyrolysis, the heating rate of 40°C/min produced a diversified product, composed by the heterocyclics, levoglucosan, phenols and hydrocarbons. The fast pyrolysis produced mainly the heterocyclic compounds, levoglucosan, phenols and carboxylic acids, in temperatures between 450°C and 500°C.

SIMULAÇÃO DO ÂNGULO DE REPOUSO ESTÁTICO DE RESÍDUO DE ACEROLA EMPREGANDO O MÉTODO DE ELEMENTOS DISCRETOS

RESUMO O ângulo de repouso estatico e uma caracteristica propria do material particulado e e uma funcao da densidade da particula, area superficial e forma, alem do coeficiente de atrito do material. Neste trabalho, o ângulo de repouso estatico de sementes de acerola foram obtidos experimentalmente e por simulacao simulados empregando o Metodo de Elementos Discretos, atraves do software EDEM. As forcas de contato entre as particulas foram representadas pelo Modelo Hertz-Mindlin. A fim de verificar como os parâmetros do modelo de forca de contato influenciavam o valor do ângulo de repouso, a tecnica de planejamento composto central foi empregada para delinear as simulacoes. Os resultados mostraram que quais os parâmetros que mais influenciam o comportamento granular da acerola. Tambem foi possivel encontrar um conjunto de valores para os parâmetros que produziram um resultado simulado muito proximo ao valor experimental.

DESIDRATADAÇÃO DE CEBOLA UTILIZANDO UM SECADOR SOLAR CONVECTIVO DO TIPO BANDEJA

RESUMO A insuficiencia de energia nos dias atuais compromete a seguranca alimentar, ja que tem implicacoes diretas na preparacao e conservacao dos alimentos. A energia solar vem destacando por representar uma das fontes nao poluente e inesgotavel da Terra. Nesse sentido o trabalho propoe o aperfeicoamento de um equipamento de secagem solar, construido por estudantes de Engenharia Quimica da UFTM, para a secagem de cebola. Foram realizados testes laboratoriais em infravermelho e estufa a fim de determinar as curvas de cinetica de secagem da cebola, nas temperaturas de 60, 80, 100 e 110 °C. Realizou-se tambem a caracterizacao da particula. Duas configuracoes do secados solar foram testadas e comparadas, realizando testes de secagem ao sol em duas condicoes, alta e baixa velocidade de rotacao do cooler, sendo a temperatura monitorada a cada 30 minutos. Os resultados da configuracao em que a bandeja encontra-se dentro do forno solar apresentou maior eficiencia de secagem, principalmente na maior velocidade de rotacao do cooler, que promove a conveccao forcada.

ESTUDO DOS REGIMES DE ESCOAMENTO DO LEITO DE JORRO FLUIDIZADO COM TUBO DRAFT EMPREGANDO FLUIDODINÂMICA COMPUTACIONAL

Os leitos de jorro fluidizado tem se mostrado promissores para operacoes de contato gas-solido com e sem reacoes quimicas, tais como secagem, revestimento, granulacao, gaseificacao, pirolise, entre outras. Isto decorre nao somente devido ao fato de ele reunir vantagens dos leitos de jorro e fluidizado, mas principalmente devido a sua eficacia em tratar transformacoes quimicas que envolvem simultaneamente transferencia de calor e massa em combinacao com particulas de diversos tamanhos. Portanto, e de fundamental importância o conhecimento detalhado da fluidodinâmica do leito, principalmente, para projetos de scale-up, o que torna a simulacao computacional uma ferramenta essencial. Estudos feitos utilizando a Fluidodinâmica Computacional (CFD) mostraram-se bastante eficientes na previsao da dinâmica das particulas neste tipo de leito. Na Fluidodinâmica Computacional as duas fases sao tratadas como continuas interpenetrantes, sendo que as fases sao descritas atraves de equacoes de conservacao de massa, momento e energia. O objetivo deste trabalho foi simular empregando a tecnica CFD os dados experimentais da fluidodinâmica de um leito de jorro fluidizado. Foram identificados oito regimes distintos de escoamento, os quais apresentaram-se em boa concordância com o mapa de regime apresentado por Sutkar et al. (2013). Os resultados mostraram que a tecnica foi eficiente para a simulacao da hidrodinâmica do leito apresentado.