Aplicação da distribuição do tempo de residência para estimativa de conversão em um reator tubular operado em condições não ideais
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Data
2023-01-10
Autores
Ferreira, João Victor Panizza
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A análise da distribuição do tempo de residência (DTR) de reatores químicos é
de fundamental importância para a indústria química e para os estudos de cálculo de
reatores, pois pode fornecer informação do desvio da idealidade, ou seja, quanto esse
reator obedece às equações teóricas de projeto. Mesmo quando se projeta um reator
para funcionar em mistura perfeita ou com escoamento pistonado, na prática sempre
haverá algum desvio fluidodinâmico no escoamento dos reagentes. Neste estudo
analisamos a DTR de um reator tubular que é usado nas práticas de laboratório do
curso de engenharia química da Unesp Araraquara, realizando medidas de
concentrações de saída de cristal violeta como traçador, que por ter propriedades
físicas apropriadas, pode ser detectado por espectrofotometria. Com concentrações
padrões do cristal foi construída uma curva analítica, que foi utilizada na determinação
da DTR para diferentes vazões. Para as vazões utilizadas neste estudo, o número de
Reynolds esteve entre 800 e 1100, indicando que o reator opera sob regime laminar.
No entanto, a análise das curvas DTR mostrou que o perfil de escoamento do traçador
segue o modelo de dispersão. O cristal violeta, além de traçador, foi utilizado também
como reagente, já que na reação com uma base forte gera um produto incolor
chamado carbinol. Para avaliar o desempenho do reator tubular em condições reais
foi realizada então uma reação entre o cristal violeta e NaOH. Com o valor da
concentração na corrente de saída comparamos o seu desempenho, através de dados
cinéticos teóricos publicados na literatura e, desta forma, estimar o porcentual de
desvio. Através do método de segregação de Danckwerts e Zwietering, foi possível
prever a conversão de saída do reator real. O método utiliza os dados cinéticos e a
curva de DTR para prever a conversão de um reator real. O cálculo mostrou que o
reator opera próximo a condição ideal, indicando um desvio pequeno. Os resultados
mostraram que o procedimento experimental foi realizado de maneira correta e
mostraram que o método de segregação é útil para medir a conversão de reatores
reais.
The analysis of the residence time distribution (DTR) of chemical reactors is of fundamental importance for the chemical industry and for studies of reactor design, as it can provide information on the deviation from ideality, that is, how much this reactor obeys the theoretical equations of project. Even when a reactor is designed to work in perfect mixing or plug flow, in practice there will always be some fluid dynamic deviation in the flow of reactants. In this study, we analyzed the DTR of a tubular reactor that is used in the laboratory practices of the chemical engineering course at Unesp Araraquara, performing measurements of crystal violet output concentrations as a tracer, which, due to its appropriate physical properties, can be detected by spectrophotometry. With standard concentrations of the crystal, an analytical curve was constructed, which was used to determine the DTR for different flow rates. For the flow rates used in this study, the Reynolds number was between 800 and 1100, indicating that the reactor operates under a laminar regime. However, the analysis of the DTR curves showed that the flow profile of the tracer follows the dispersion model. Crystal violet, in addition to being a tracer, was also used as a reagent, since in the reaction with a strong base it generates a colorless product called carbinol. To evaluate the performance of the tubular reactor under real conditions, a reaction between crystal violet and NaOH was performed. With the value of the concentration in the output current we compare its performance, through theoretical kinetic data published in the literature and, in this way, estimate the percentage of deviation. Through the Danckwerts and Zwietering segregation method, it was possible to predict the output conversion of the real reactor. The method uses the kinetic data and the DTR curve to predict the conversion of a real reactor. The calculation showed that the reactor operates close to the ideal condition, indicating a small deviation. The results showed that the experimental procedure was performed correctly and showed that the segregation method is useful to measure the conversion of real reactors.
The analysis of the residence time distribution (DTR) of chemical reactors is of fundamental importance for the chemical industry and for studies of reactor design, as it can provide information on the deviation from ideality, that is, how much this reactor obeys the theoretical equations of project. Even when a reactor is designed to work in perfect mixing or plug flow, in practice there will always be some fluid dynamic deviation in the flow of reactants. In this study, we analyzed the DTR of a tubular reactor that is used in the laboratory practices of the chemical engineering course at Unesp Araraquara, performing measurements of crystal violet output concentrations as a tracer, which, due to its appropriate physical properties, can be detected by spectrophotometry. With standard concentrations of the crystal, an analytical curve was constructed, which was used to determine the DTR for different flow rates. For the flow rates used in this study, the Reynolds number was between 800 and 1100, indicating that the reactor operates under a laminar regime. However, the analysis of the DTR curves showed that the flow profile of the tracer follows the dispersion model. Crystal violet, in addition to being a tracer, was also used as a reagent, since in the reaction with a strong base it generates a colorless product called carbinol. To evaluate the performance of the tubular reactor under real conditions, a reaction between crystal violet and NaOH was performed. With the value of the concentration in the output current we compare its performance, through theoretical kinetic data published in the literature and, in this way, estimate the percentage of deviation. Through the Danckwerts and Zwietering segregation method, it was possible to predict the output conversion of the real reactor. The method uses the kinetic data and the DTR curve to predict the conversion of a real reactor. The calculation showed that the reactor operates close to the ideal condition, indicating a small deviation. The results showed that the experimental procedure was performed correctly and showed that the segregation method is useful to measure the conversion of real reactors.
Descrição
Palavras-chave
Dinâmica de fluidos, Reatores químicos, Mistura (Química), Fluxo laminar, Cinética química