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Gas scrubbers are important equipment for air pollution removal. Among the scrubbers we can highlight the spray tower, which has several advantages, such as low pressure drop, easy maintenance and low operational costs. However, the velocity profile inside this equipment is complex, making its analysis and design very difficult. Therefore, the present work aims to perform numerical simulations using CFD (Computational Fluid Dynamics) using Euler-Lagrange approach applied to a spray tower for SO2 absorption. The simulations evaluated the influence of the following variables on velocity and SO2 profiles, as gas and liquid flow rates, size droplet distribution and spray nozzles with different orifice diameters. The results obtained by CFD simulations showed the main absorption zones in the column and the influence of gas velocity, particle trajectories and droplet diameter in the sulfur dioxide absorption process. Furthermore, the experimental efficiencies were compared with the simulated for two conditions, the first condition with an experimental efficiency of 89% presented a simulated efficiency of 79.6% and the second condition with an experimental efficiency of 98.27% presented a simulated efficiency of 100%. This shows a good approximation between the simulated and experimental results

One of the most common methods for controlling SO2 is the process of desulfurization using spray tower. Due to the large number of parameters to be evaluated and the process complexity, there are difficulties in the proposal of mathematical models to predict the removal efficiency and the gas phase volumetric mass transfer coefficient (kga). The aim of this study was to obtain an artificial neural network (ANN) to predict the removal efficiency and the kga in a spray tower for SO2 removal. The results showed that the choosing of the best model from the training and validation steps did not generate reliable results. The best structure was defined by analyzing the results of a simulation step, which used independent data. The best model was obtained with the structure 5-9-2, trained using the Levenberg–Marquardt algorithm with Bayesian Regularization and having the softmax and linear transfer functions in the hidden and output layers, respectively. This network presented an average error of 8.44% for the outlet SO2 concentration and 4.53% for the kga. This work showed that the use of neural networks is promising in the prediction of important variables in the processes of removal of air pollutants in spray towers.

The blackberry fruit ( Rubus spp.) presents an attractive color ranging from purple red to blue, due to the high content of bioactive compounds, such as anthocyanins. Bioactive compounds have antioxidant properties, acting as free radical scavengers and are also frequently linked to the prevention of cardiovascular and other chronic diseases. Due to native-form anthocyanins instability against environmental stress, bioactive compounds are not always as effective in improving human health as they could be. Therefore, the production of powders using adjuvants is a promising approach for encapsulating anthocyanins-rich pastes, in order to improve their stability and application. Thus, the aim of the present study was to evaluate the influence of adjuvants on the physical properties of the powder, and on anthocyanin content and antioxidant activity of the pastes and freeze-dried milk-blackberry pulp mixtures. The pastes formulated were of milk-blackberry pulp (25%:75%, (weight/weight ( w /w)) and of milk-blackberry pulp-adjuvant (25%:70%:5%, (w/w/w)), and the adjuvants employed were maltodextrins 10DE and 20DE and Capsul®. The addition of maltodextrin 20DE and Capsul® resulted in pastes with high anthocyanins content (451.6 ± 80.0 μg/g and 453.1 ± 26.0 μg/g, respectively), similar to the paste without adjuvants (568.6 ± 3.4 μg/g). Also, maltodextrin 20DE and Capsul® showed a high protection capacity of the anthocyanins present on the powders (around 96% of anthocyanins retention). When no adjuvants were used, the anthocyanins retention was very low (40.1%). The freeze-drying process maintained the antioxidant capacity of the bioactive compounds and the powders obtained showed good quality with low moisture content and hygroscopicity.

Spray towers allow for controlling air pollution in which a liquid is sprayed in small droplets to produce a large interfacial area for mass transfer between a gas and a liquid phase. An experimental study of a spray tower for removing SO2 is described. The experiments were carried out under different operating conditions by varying the gas velocity, liquid flow rate, and SO2 concentration. SO2 removal efficiency, volumetric mass transfer coefficient, and liquid-film formation as a result of the collision of droplets against the tower wall are investigated. Removal efficiency and volumetric mass transfer coefficient are analyzed as a function of gas velocity, liquid flow rate, and SO2 concentration, while liquid-film formation is evaluated as a function of tower height. The results indicate high removal efficiency. Correlations to predict the volumetric mass transfer coefficient are also proposed.

Orientador: Waldir Antônio Bizzo Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica Resumo: Este trabalho apresenta uma avaliação experimental da absorção de SO2 e um estudo preliminar da absorção de NO em uma torre de nebulização. O estudo experimental de absorção de SO2 foi realizado com solução de NaOH em diferentes condições de operação, variando a vazão de solução, vazão de gás e bicos pulverizadores de pressão. Assim, foi possível avaliar a influencia do tempo de residência do gás, da relação L/G e dos bicos pulverizadores de pressão. Além disso, analisa a absorção de SO2 ao longo da coluna, retirando amostras do interior da torre. O estudo experimental de absorção de NO na torre de nebulização avalia o desempenho de uma torre projetada para absorção de SO2 na absorção de NO. Os ensaios de absorção de NO foram realizados em meio ácido com soluções de peróxido de hidrogênio (H2O2) e de peróxido de hidrogênio (H2O2) com sulfato ferroso (FeSO4), em diferentes condições de operação, a fim de avaliar a influência do tempo de residência do gás, da relação L/G, da concentração de peróxido de hidrogênio e da presença de sulfato ferroso na solução. Além do estudo experimental, este trabalho apresenta um estudo teórico da absorção de SO2, utilizando dados provenientes do estudo experimental. As simulações realizadas mostraram a importância do diâmetro de gota, a influência da vazão de gás e a evolução da velocidade e desaceleração das gotas ao longo da torre Abstract: This work presents an experimental evaluation of SO2 absorption and a preliminary study of NO absorption into a spray tower. The experimental study of the absorption of SO2 was carried out with NaOH solution in different operation conditions, varying the liquid flow rate, the gas flow rate and pressure spray nozzles. Therefore, it was possible evaluate the influence of gás residence time, L/G ratio and pressure spray nozzles. Besides, it analyses the SO2 absorption along the column, taking samples from inside of the tower. The experimental study of NO absorption in the spray tower evaluates the performance of a designed tower for SO2 absorption in the NO absorption. The NO absorption tests were carried out in acid environment, with hydrogen peroxide solutions and hydrogen peroxide (H2O2) solutions with ferrous sulfate (FeSO4), in different operation conditions, in order to evaluate the influence of gas residence time, L/G ratio, hydrogen peroxide concentration and the presence of ferrous sulfate in the solution. Besides the experimental study, this work presents a theoretical study of SO2 absorption, using data from experimental study. The performed simulations showed the importance of the diameter of the droplet, the influence of gas flow rate and the evolution of velocity and deceleration of the droplets along the tower Doutorado Térmica e Fluídos Doutor em Engenharia Mecânica

Orientador: Waldir Antonio Bizzo Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica Resumo: Este trabalho estuda a absorção de SO2 em uma torre de nebulização contra-corrente. Um estudo experimental foi realizado, a fim de determinar a influencia das variáveis do processo de absorção. As variáveis estudadas foram: velocidade do gás, vazão de líquido, concentração de SO2 no gás na entrada e a relação líquido/gás. Também foi analisada a formação do filme de líquido ao longo da torre, proveniente da colisão das gotas com a parede do equipamento. A análise do filme de líquido foi importante para determinar a vazão das gotas ao longo da torre. Além do estudo experimental foi desenvolvido neste trabalho um modelo para simular a transferência de massa em uma torre de nebulização para remoção de SO2. Foi analisada a transferência de massa tanto nas gotas quanto no filme de líquido. O modelo foi desenvolvido para prever a concentração de SO2 no gás na entrada da torre, pois a concentração de SO2 na saída foi imposta. O modelo mostra a principal área de absorção na torre, a influência do diâmetro da torre, a influência da velocidade da gota na absorção de SO2 e dados do modelo foram comparados com dados experimentais Abstract: This work studies the absorption of sulfur dioxide in a counter-current spray tower. An experimental study was carried out to analyzer the process parameters of the absorption of sulfur dioxide. The parameters studied were: gas velocity, liquid flow, sulfur dioxide concentrations in the gas feed and liquid/gas rate. It was also analyzed the formation of liquid film, from the collision of drops on the wall tower. The analyzed liquid film was used to determined de liquid flow as drops along the spray tower. Besides an experimental study it was developed in this work a model to simulate the mass transfer in a spray tower to removal sulfur dioxide. Both mass transfer in the drops and mass transfer in the liquid film were analyzed. The model has been developed to predict the SO2 concentrations in the gas feed, therefore the SO2 concentrations in the gas exit was determined. The model shows the main area of absorption, the influence drop diameter, the influence of drop velocity in the absorption of SO2 and data from model were compared with experimental data Mestrado Térmica e Fluídos Mestre em Engenharia Mecânica

O volume total de emissão de particulados produzidos a serem tratados, aumenta cada vez mais enquanto os limites de emissão estipulados vem em constante redução. Portanto, é necessário aprimorar os conhecimentos sobre eficiência de captura nos sistemas de lavagem de gases, avaliando seu comportamento hidrodinâmico. Foi realizada medição de dados operacionais em condição controlada e medição isocinética em condições normais de operação. Os resultados foram comparados com a avaliação dos modelos existentes de desempenho e de perda de carga. Finalmente, avaliou-se o modelo em CFD (fluidodinâmica computacional) para elucidar o comportamento no interior da unidade industrial. Um lavador industrial Venturi não é apenas a parte convergente, garganta e divergente de um Venturi, e sim todo o conjunto, desde a entrada de gases e de água até a parte de captura de gotas em separador ciclônico. A eficiência de coleta das partículas obtida experimentalmente é de 93.2%, ao passo que a eficiência teórica está entre 98,2% e 100%. Isso se explica pelas condições não ideais de operação em unidade industrial do qual os modelos foram incapazes de modelar. A perda de carga total no lavador, dada como o valor da perda de pressão do escoamento entre as seções convergente, garganta e divergente, foi superior no lavador industrial em estudo. Uma vez que a diferença entre a perda de carga somente com ar é muito diferente de quando se tem sistema ar+água, explica-se a diferença entre o perfil de pressão teórica, por simulação e por medição experimental, onde a curva de recuperação de pressão é mais acentuada nos experimentos. As medições experimentais, as elucidações de mecanismos por modelos teóricos e a simulação por CFD para verificação formam um tripé de ferramentas que devem ser utilizadas em conjunto por se tratar de operação industrial. A maioria da literatura trata de experimentos em pilotos com condições controladas, com proposição de modelos teóricos, ou trata de modelagem CFD comparada com a literatura de modelos teóricos. Aqui se apresenta a aplicação das três abordagens. The total particulate matter volume emission produced to be treated are progressively increasing, while the emission limits are in the opposite direction. Therefore, it is necessary to improve the knowledge about wet scrubber collection efficiency through its hydrodynamic behavior. Operacional data measurements in controlled conditions, and isokinetic sampling in normal operational conditions were made. The data was compared with performance and pressure drop mathematical models. Finally, the CFD (computacional fluidynamics) models were evaluated to elucidate the internal industrial equipment behavior. An industrial Venturi scrubber is not composed basically only by convergent, throught and divergent sections, but rather the whole machinery, since the inlet of gases and water and the water droplets removal in a cyclonic vessel. The experimental collection efficiency obtained was 93.2%, whereas the theorical values range from 98.2% to 100%. These results are explained by non-ideal conditions in the industrial unit. The Venturi scrubber total pressure drop, known as pressure difference between the convergent, throught and divergent sections, is higher in the industrial unit. Since the pressure drop in no water conditions is very different with the presence of water, it is explained the profile difference between theorical, simulated and experimental runs, where the recovery profile pressure is sharper in experimental data. The water fluid flow and the droplets distribution are slightly different in industrial conditions, even so with similar trends. The experimental measurements, the theorical models mechanism elucidation and the CFD simulation forms a tools tripod which must be used together since it is about an industrial operation. In the literature, is found basically of pilot scale experiments in controlled conditions, with theorical models proposition, or CFD simulation compared with theorical models. In the present study, for the first time ever, the tree aprroachs combined.