-The knowledge of the phase equilibrium is one of the most important factors to study the design of separation processes controlled by the equilibrium. Fatty acids are present in high concentration as byproducts in vegetable oils but the equilibrium data involving these components is scarce. The objective of this work is the experimental determination of the liquid-vapor equilibrium of five binary different systems formed by carbon dioxide and palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1), linoleic acid (C18:2) and linolenic acid (C18:3). The equilibrium experimental data was collected at 40, 60 and 80ºC at 60, 90 and 120 bar, at the extract and raffinate phases, using an experimental apparatus containing an extractor, a gas cylinder and pressure and temperature controllers. The data was modeled using the cubic equation of state of Peng-Robinson with the mixing rule of van der Waals with binary interaction parameters. The model was adequate to treat the experimental data at each temperature and at all the temperatures together. The best model that includes the van der Waals mixing rule with two parameters has maximum deviation of 17%. The distribution coefficients were also analyzed and it was concluded that the fractionation of the fatty acids is possible using supercritical carbon dioxide.
Este estudo constatou a possibilidade de extrairem-se ácidos graxos livres de óleos vegetais com CO2 supercrítico. Utilizou-se neste trabalho óleos de soja e de castanha do Pará. A pesquisa desenvolveu-se em duas etapas, inicialmente investigou-se a possibilidade de se extrairem os ácidos graxos destes óleos em condições de extração que variaram de 50-140 bar e de 40-80oC durante 40-160 minutos. Concluiu-se que é possível realizar a desacidificação de óleos vegetais. A eficiência da extração foi de aproximadamente 30% a 140 bar e 80oC para ambos os óleos. Após esta primeira etapa, o próximo passo foi a tentativa de obter-se um aumento na eficiência do processo promovendo a pré-degomagem nos óleos brutos como uma etapa anterior ao processo de desacidificação com CO2 supercrítico. A degomagem foi realizada através de dois métodos diferentes, um para extrair as gomas hidratáveis e outro para extrair tanto as hidratáveis como as não-hidratáveis. Os resultados experimentais foram obtidos a 140 bar e 80oC durante 40-160 minutos, mostrando que a pré-degomagem é realmente necessária, pois a eficiência da extração aumentou para 57% para o óleo de soja e 42% para o de castanha do Pará totalmente degomados, sendo que o método escolhido deve extrair tanto as gomas hidratáveis como as não-hidratáveis. Finalmente, utilizou-se cossolvente (etanol a 1-5% do peso do óleo) para auxiliar a extração, observando-se um aumento na eficiência para aproximadamente 65% para o óleo de soja e 56% para o de castanha do Pará totalmente degomados a 140 bar e 80oC por 40-160 minutos.
Purification of Vegetable Oils using Supercritical CO2. This work presents a study on the extraction of free fatty acids from crude soy and Brazil nut oils, using supercritical carbon dioxide. It was developed in two stages, at first moment we verified the possibility to extract free fatty acids from these oils and then the extraction conditions were evaluated at pressures changing between 50-140 bar and temperatures between 40-80oC during 40-160 minutes. It was concluded that it is possible to promote the deacidification of vegetable oils. Experimental data has shown that an increase in pressure produces a significant increase in extraction yield, but an increase in temperature is not so signifcant, and the extraction yield was not satisfactory, it was around 30% under 140 bar and 80oC to both oils. This process was optimized by degumming crude vegetable oils before the deacidification using supercritical carbon dioxide. The degumming was performed by through two different methods, one for hydratable gums and other for nonhydratable gums. Experimental data was obtained under 140 bar and 80oC during 40-160 minutes and showed that the degumming was really necessary before the deacidification in supercritical carbon dioxide. The extraction yield increased to around 57% for soy oil and 42% for Brazil nut oil. The best method of degumming must remove as much hydratables gums as nonhydratables gums. Finally we used cossolvent (ethanol 1-5% of oil weight) to aid in th...
Este estudo investiga os diferentes arranjos de equipamentos para o desenvolvimento de uma unidade industrial para purificação de óleos vegetais utilizando extração com CO2 sob condições supercríticas. Objetivando a concepção de uma planta comercial a partir da unidade de laboratório o estudo deve iniciar-se através da determinação de alguns parâmetros experimentais e um estudo energético do processo. Em trabalho anterior foram definidas as condições ótimas (T, P) para purificação de óleos vegetais por CO2 supercrítico [7]. A etapa de otimização energética envolve um número máximo de variações possíveis nas condições de operação, visando fornecer dados adequados para a definição do rendimento e qualidade do produto, assim como do tempo de extração. A representação do processo nos diagramas de estado do solvente são muito úteis para a determinação das propriedades termodinâmicas em cada estágio do processo. Os diagramas Temperatura-Entropia (TxS) são particularmente apropriados para determinação da energia requerida ou removida no processo reversível. Com a determinação das condições de operação e do tempo para cada etapa individual é possível plotar a variação da pressão e da temperatura versus tempo, assim como definir e dimensionar os equipamentos necessários para o processo de extração supercrítica.
This study examines the method to development of an industrial unity to purification of vegetable oils using extraction with CO2 under supercritical conditions. Aiming at the conception of a commercial plant from laboratory scale, the study must begin through determination of some experimental measurement and a study of energy required in the process. In previous work the optimum conditions (T, P) to purification of vegetable oil by supercritical CO2 were determined. It was possible to deacidify, deodorize e clarify degummed vegetable oils. The step of energy optimization involves a large number of variables in operational conditions seeking to supply suitable data for definition of yield and quality of product, such as the extraction time. The representation of the process in solvent phase diagrams is more convenient to determine the thermodynamics proprieties in each stage of process . The Temperature -Entropy (TxS) diagrams are particular suitable for determination of energy required or removed in a reversible process. After determination of the operational conditions and time to each individual stage, it is possible to plot the variation of pressure and temperature versus time , as well as to define and plan the necessary furnitures to supercritical extraction
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