Development of nonequilibrium models for characterization and application in simulation of complex distillation columns

Orientador : Maria Regina Wolf MacielTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia QuimicaResumo: A destilação é, certamente, o processo mais aplicado na separação de misturas líquidas. Embora esta seja uma operação unitária conhecida de longa data, ainda, nos dias de hoje persistem algumas dificuldades na proposição de esquemas de destilação apropriados. Sendo assim, o objetivo deste trabalho de tese foi aplicar modelos mais realistas na caracterização de misturas e na simulação de processos de destilação, em regimes estacionários e dinâmicos. Para tanto, foram avaliados dois softawes, desenvolvidos no Laboratório de Desenvolvimentos de Processos de Separação, para simulações de colunas de destilação considerando os modelos de estágios de equilíbrio e de não equilíbrio. Os resultados obtidos mostraram que, geralmente, os perfis obtidos com as duas modelagens são diferentes, em ambos os regimes. A modelagem de estágios de não equilíbrio foi aplicada também para a caracterização de sistemas, utilizando mapas de curvas residuais. Avaliou-se, ainda, a influência das correlações de eficiência de Barros & Wolf em mapas de curvas residuais. Os perfis obtidos com as correlações de eficiência de Barros & Wolf mostram grande concordância com os calculados pelo modelo de estágios de não equilíbrio. Com os mapas de curvas residuais calculados concluiu-se que as trajetórias líquidas de composição não cruzam as fronteiras de destilação, sendo esta um questão de polêmica na atualidade, no entanto, nossos resultados mostram os perfis corretos. Além disso, desenvolveu-se, neste trabalho de tese, um programa computacional para a caracterização de sistemas reativos. A vantagem do novo algoritmo proposto está, principalmente, no fato do programa não depender de estimativas inicias e ser de fácil convergência. O programa é, também, capaz de predizer todos os azeótropos presentes na mistura, quando existam um ou mais de um, ou ainda de afirmar que a mistura é zeotrópica. Os resultados obtidos são concordantes com valores experimentais ou calculados por outros métodos. Na linha do processo de destilação reativa, sendo este um processo inovador, foi proposta a separação da mistura fenol + água. A separação desta mistura é de grande interesse, por questões econômicas e ambientais. Preliminarmente, fez-se um estudo na busca de uma reação apropriada para o consumo de fenol. O processo proposto atende completamente às questões ambientais, visto que gera somente correntes limpas e é, portanto, uma nova alternativa para o tratamento de correntes fenólicas. Por fim, desenvolveu-se neste trabalho um conjunto completo para caracterização de sistemas e simulação de processos, envolvendo desde o modelo de estágios de equilíbrio até o modelo de estágios de não equilíbrio. Propôs-se, ainda, um eficiente processo para o tratamento de águas fenólicasAbstract: Distillation is, certainly, the most applied process in the separation of liquid mixtures. Although this is a very known unit operation, still nowadays some difficulties persist in the proposal of appropriate distillation schemes. Thus, the objective of this work was to apply more realistic models in the characterization of mixtures and in the simulation of distillation process in, both, steady state and dynamic regime. In this way, two softwares developed in the Laboratory of Separation Processes Development were evaluated. These softwares consider the equilibrium and the nonequilibrium stage models in steady state and dynamic regime. The results show that, generally, the profiles obtained with the two models are different, in both regimes. The nonequilibrium stage model was also applied for the systems characterization, in residue curve maps. It was evaluated, still, the influence of Barros & Wolf correlations for efficiencies on residue curve maps. The profiles obtained with the Barros & Wolf correlations show good agreement with the calculated with the nonequilibrium stage model. The calculated residue curve maps showed that residue curves do not cross distillation boundaries. Nowadays, this is a question of controversy, however our results show the correct behavior. Moreover, it was developed in this work a computational program for the characterization of reactive systems. The advantage of the new proposed algorithm is mainly because the program does not depend on initial estimates and it is of easy convergence. The program is, also, able to predict all the azeotropes present in the mixture, when one or more than one exist, or still to affirm that the mixture is zeotropic. The obtained results are in agreement with experimental values or values calculated by other methods. Regarding to reactive distillation, being an innovative process, it was proposed the separation of the mixture phenol + water. The separation of this mixture is of great interest, for economic and environmental issues. Preliminarily, it was carried out a study of an appropriate reaction for the phenol consumption. The considered process takes care of environmental questions, since it only generates current clean and it is, therefore, an alternative process for the phenolic wastewater treatment. Finally, in this work, it was developed a complete set for characterization of systems and simulation of processes, involving the equilibrium and the nonequilibrium stage modes, in steady state and dynamic regime. It was considered, still, an efficient process for the phenolic wastewater treatmentDoutoradoDesenvolvimento de Processos QuímicosDoutor em Engenharia Químic

Desenvolvimento de um programa para geração de mapas de curvas residuais e aplicação a processos de destilação azeotropica e extrativa

Orientador: Maria Regina Wolf MacielDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia QuimicaMestrad

Effects of coconut granular activated carbon pretreatment on membrane filtration in a gravitational driven process to improve drinking water quality

This study evaluates the performance of a polymeric microfiltration membrane, as well as its combination with a coconut granular activated carbon (GAC) pretreatment, in a gravitational filtration module, to improve the quality of water destined to human consumption. The proposed membrane and adsorbent were thoroughly characterized using instrumental techniques, such as contact angle, Brunauer–Emmett–Teller) and Fourier transform infrared spectroscopy analyses. The applied processes (membrane and GAC + membrane) were evaluated regarding permeate flux, fouling percentage, pH and removal of Escherichia coli, colour, turbidity and free chlorine. The obtained results for filtrations with and without GAC pretreatment were similar in terms of water quality. GAC pretreatment ensured higher chlorine removals, as well as higher initial permeate fluxes. This system, applying GAC as a pretreatment and a gravitational driven membrane filtration, could be considered as an alternative point-of-use treatment for water destined for human consumption.Fundação Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Stabilization of açaí (Euterpe oleracea Mart.) juice by the microfiltration process

Açaí berry, a Brazilian palm fruit widely distributed in northern South America, is acknowledged for its functional properties such as high antioxidant capacity and anti-inflammatory activities. Although the açaí juice is highly appreciated in Brazil and even worldwide, its commercialization is still limited. Microfiltration process is largely applied in juice processing, eliminating many of the traditional processing steps and reducing time, energy and addition of clarifying agents. Furthermore, microfiltration process may eliminate microorganisms and compounds responsible for turbidity in the juice. Current assay applies a microfiltration process to obtain a stabilized açaí permeate pulp. Microfiltrations of açaí pulp were carried out in a dead end configuration with a flat membrane of 0.22 μm pore size. Permeate pulp was characterized according to its turbidity, lipid concentration and microbiological analysis. Initial permeate flux was 103 kg m-2 h-1. After an initial flux decline during 30 min., due to membrane compaction and fouling occurrences, flux was stabilized at 20 kg m-2 h-1. The microfiltration process reduced the initial açaí pulp turbidity by 99.98% and lipids were not identified in the permeate. Microbiological analysis showed that the contamination by microorganism decreased in the permeate pulp when compared to that in raw açaí pulp.Açaí berry, a Brazilian palm fruit widely distributed in northern South America, is acknowledged for its functional properties such as high antioxidant capacity and anti-inflammatory activities. Although the açaí juice is highly appreciated in Brazil and even worldwide, its commercialization is still limited. Microfiltration process is largely applied in juice processing, eliminating many of the traditional processing steps and reducing time, energy and addition of clarifying agents. Furthermore, microfiltration process may eliminate microorganisms and compounds responsible for turbidity in the juice. Current assay applies a microfiltration process to obtain a stabilized açaí permeate pulp. Microfiltrations of açaí pulp were carried out in a dead end configuration with a flat membrane of 0.22 μm pore size. Permeate pulp was characterized according to its turbidity, lipid concentration and microbiological analysis. Initial permeate flux was 103 kg m-2 h-1. After an initial flux decline during 30 min., due to membrane compaction and fouling occurrences, flux was stabilized at 20 kg m-2 h-1. The microfiltration process reduced the initial açaí pulp turbidity by 99.98% and lipids were not identified in the permeate. Microbiological analysis showed that the contamination by microorganism decreased in the permeate pulp when compared to that in raw açaí pulp.

Determination of Enthalpies of Formation of Fatty Acids and Esters by Density Functional Theory Calculations with an Empirical Correction

Scarcity of reliable thermochemical data of biodiesel molecules motivated the use of computational calculations to accurately predict standard enthalpies of formation of fatty acids and esters by combining B3LYP/6-311+G­(d,p) calculations with an empirical correction. This correction is based on information on the molecular structure and is optimized by using the least-squares method to minimize the deviation between theoretical and experimental enthalpies for some fatty acids and esters. The mean absolute deviation between calculated and experimental enthalpies decreased from 122.3 to 5.3 kJ mol^–1 when the parametric correction equation was applied to the B3LYP/6-311+G­(d,p) results for fatty acid molecules. The calculated data were used to estimate thermochemical properties of the esterification reactions of oleic and linoleic acids with methanol. Results confirmed the endothermic and the nonspontaneous characteristics of these reactions. Thus, the proposed correction is a suitable alternative to calculate thermodynamic properties of fatty acids and esters, with remarkable accuracy and low computational cost