Análise dos aspectos energéticos e de transferência de calor em massa em processos de secagem de pasta leite-polpa de amora preta em leito de jorro.
Data
2019-11-22
Autores
Fujita, Vitor Kim 
Giannella, Rafael Luiz
Orientadores
Braga, Matheus Boeira
Tipo
Trabalho de conclusão de curso
Título da Revista
ISSN da Revista
Título de Volume
Resumo
O Processo de desidratação da polpa de amora preta por secagem em leito de jorro tem como objetivo aumentar a estabilidade do produto em pó, melhorando as condições de armazenamento e transporte. Devido à composição química e à alta concentração de água presente na polpa de amora preta, utilizou-se uma mistura leite-polpa de amora, já que a secagem da polpa sem a adição de adjuvantes pode resultar em níveis baixos de rendimento, inviabilizando o processo. O objetivo deste trabalho foi estudar a transferência de calor e massa durante o processo de secagem de mistura leite concentrado-polpa de amora preta em leito de jorro cônico cilíndrico. O estudo da transferência de calor e massa e dos aspectos energéticos (eficiência energética e consumo específico de energia), foi realizado para diversos ensaios de secagem reportados em Braga (2014). Os ensaios foram conduzidos sob condições fixas de massa de inerte de 1,4 kg e velocidade do ar de processo de 1,2.velocidade de jorro mínimo. As variáveis de processo foram a temperatura do ar de secagem (60 a 80 oC), o tipo de inerte (poliestireno ou polipropileno), a pressão de alimentação da pasta (10 a 20 psig), a vazão de alimentação da pasta (2 a 4 ml/min) e o modo de alimentação (atomizado ou gotejado). Com uma massa fixa de inerte polipropileno de 1,4 kg, obteve-se uma velocidade de jorro mínimo média de 0,463 m/s. Já para o poliestireno a velocidade de jorro mínimo média foi de 0,490 m/s. Em relação aos aspectos energéticos, observou-se um maior valor de eficiência energética e um menor valor de consumo específico de energia para o Ensaio 3, ou seja, quando se utilizou a maior vazão de alimentação da pasta de 4 ml/min e a menor temperatura de entrada do ar de 60 oC. Para os ensaios 8 e 9 (mesmas condições operacionais: vazão de alimentação da pasta de 2 ml/min, temperatura do ar de entrada de 60 oC, inerte poliestireno e alimentação por gotejamento), os quais apresentaram a maior eficiência na produção de pó segundo Braga (2014), calculou-se o número de Nusselt experimental, resultando em valores de 0,280 e 0,225, respectivamente. Os valores experimentais de número de Nusselt foram confrontados com os valores obtidos via correlações disponíveis na literatura, sendo a correlação de Rocha et al. (1996) a que melhor descreveu o processo. Analogamente, para a transferência de massa e para os Ensaios 8 e 9, obteve-se os valores experimentais do número de Sherwood de 0,026 e 0,023, respectivamente.
The process of blackberries dehydration using spouted bed aims to increase the powder stability and improve the storage and transportation conditions. Due to the chemical components and the high water concentration in blackberries, it was used a Milk-Blackberry mix paste, since the pulp drying without adjuvants could result in a low efficiency and affect the efficiency negatively. The objective was studying the heat and mass transfer during the drying process of Milk-Blackberry mix paste using a conventional spouted bed. The heat and mass transfer analysis (energy efficiency and specific energy consumption) were studied to different laboratory tests by Braga (2014). The tests were conducted under specific conditions, a specific polypropylene mass, 1,4 Kg and a air speed of 1.2 times the minimum spouting velocity. The process variables were the drying air temperature ( 60 to 80 o C), the sort of inert (polypropylene and polystyrene), the feed pressure (10 to 20 psig), the paste flow rate (2 to 4 mL/min) and feeding mode (drip or atomized). With a fixed mass of polypropylene of 1.4 Kg, it was obtained a minimum spouting velocity of 0.463 m/s. To the polystyrene the minimum spouting velocity was 0.490 m/s. Regarding the energetic aspects it was noticed a bigger energy efficiency and a smaller specific energy consumption value to the tes number 3, which means that when it was used the biggest feeding flow rate (4 mL/min) and the smallest air temperature (60 oC). To the tests 8 and 9 (same operational conditions: feeding paste flow rate of 2 mL/min, inlet air temperature of 60 oC, polystyrene and drip feeding), which showed a better efficiency in the powder production, concluded by Braga (2014), it was calculated the experimental Nusselt number, resulting in values between 0.280 and 0.225, respectively. The experiental Nusselt number values were compared with the ones obtained through correlations in literature and the Rocha et al (1996) was the one that best fitted the process. Similarly, to the mass transfer e to the tests 8 and 9, it was obtained the experimental Sherwood number, 0.026 and 0.023, respectively.
The process of blackberries dehydration using spouted bed aims to increase the powder stability and improve the storage and transportation conditions. Due to the chemical components and the high water concentration in blackberries, it was used a Milk-Blackberry mix paste, since the pulp drying without adjuvants could result in a low efficiency and affect the efficiency negatively. The objective was studying the heat and mass transfer during the drying process of Milk-Blackberry mix paste using a conventional spouted bed. The heat and mass transfer analysis (energy efficiency and specific energy consumption) were studied to different laboratory tests by Braga (2014). The tests were conducted under specific conditions, a specific polypropylene mass, 1,4 Kg and a air speed of 1.2 times the minimum spouting velocity. The process variables were the drying air temperature ( 60 to 80 o C), the sort of inert (polypropylene and polystyrene), the feed pressure (10 to 20 psig), the paste flow rate (2 to 4 mL/min) and feeding mode (drip or atomized). With a fixed mass of polypropylene of 1.4 Kg, it was obtained a minimum spouting velocity of 0.463 m/s. To the polystyrene the minimum spouting velocity was 0.490 m/s. Regarding the energetic aspects it was noticed a bigger energy efficiency and a smaller specific energy consumption value to the tes number 3, which means that when it was used the biggest feeding flow rate (4 mL/min) and the smallest air temperature (60 oC). To the tests 8 and 9 (same operational conditions: feeding paste flow rate of 2 mL/min, inlet air temperature of 60 oC, polystyrene and drip feeding), which showed a better efficiency in the powder production, concluded by Braga (2014), it was calculated the experimental Nusselt number, resulting in values between 0.280 and 0.225, respectively. The experiental Nusselt number values were compared with the ones obtained through correlations in literature and the Rocha et al (1996) was the one that best fitted the process. Similarly, to the mass transfer e to the tests 8 and 9, it was obtained the experimental Sherwood number, 0.026 and 0.023, respectively.