CFD Analysis of Turbulence Models to Achieve the Digester Mixing Process

Mixing efficiency defines the features of physicochemical and biological reactions carried out in reactors or digesters. The reason for this influence is because it conditions the heat and mass transfer. That is why the mixing level and intensity become important aspects to study to know the effects they have on the processes. Furthermore, it should be noted that most of the mixing processes are carried out under turbulent conditions. Mixing enhancement evaluation is achieved in two ways, that is, experimentally and performing simulations. Simulations are based on numerical methods approximating solutions to results in line with reality. In this context, turbulence models applied in systems have great influence on the final numerical solution and, therefore, on the interpretation of improved mixing in reactors. It is also necessary to consider the influence of rheology in these simulations, since the working fluid does not always have a linear stress-strain relationship. In this way, an analysis of turbulence models and their applications in mixing characterization and the adequacy of these models to the reactor configuration and operating conditions is carried out. Mention is also made of the experiences around the study of turbulence in mixing tanks

Postharvest respiration of fruits and environmental factors interaction: An approach by dynamic regression models

The respiratory metabolism of fruits is affected by multiple internal (product) and external (environmental) factors that often interact with each other. Among the external factors that have the greatest influence on respiration are temperature, air composition, moisture content and illumination. The aim of this paper is to elucidate the influence of environmental factors on the respiration rate of peach fruits based on transfer models obtained by dynamic regression modelling (ARIMAX). The fitted ARIMA models met the criteria of parsimony and white noise in residuals. The estimated coefficients of each model were statistically significant under the Durbin-Watson (DW), Akaike (AIC) and Schwarz (SBC) criteria. Transfer functions revealed 0.15% and 1.9% increase, and 0.001% decrease in the respiration rate of the peach fruit for each unit of change in temperature, relative humidity and illumination of the storage environment, respectively. The respiration rate response took place 1-8 minutes after the change in environmental variables had occurred. It was concluded that the dynamic regression modelling is reliable for predicting the physiological response of fruits the effect of external factors imposed continuously during postharvest handling

Biodrying under Greenhouse Conditions as Pretreatment for Horticultural Waste

The biodrying process was studied as an alternative technology to reduce the mass and volume of horticultural waste. Four static piles were prepared inside a greenhouse: two containing whole waste and two consisting of shredded waste. All the piles were compared with a test pile containing whole waste and placed outside the greenhouse. In two cases, ventilation ducts were installed to improve aeration. Each greenhouse was 2.0 m wide, 3.5 m long and 1.16 m high. The air temperature and relative humidity were monitored both inside and outside the greenhouse. Mass, humidity, organic matter and total nitrogen in the waste were measured. Piles inside the greenhouse showed decreases of 80% and 75% in weight and volume, respectively, during the first 16 days. The data obtained in this work suggest that biodrying could improve the handling and transport of horticultural waste while also minimizing the impact of pollutants

Influencia del cultivar y de la fecha de cosecha en el beneficiado industrial de granos de café

Conversion of cherry and parchment coffee (Coffea arabica L.) to green coffee was determined during two consecutive years of harvest for eight different coffee cultivars grown in Mexico. 'Mass balance' was useful to adjust the fruit humidity to 0.12 g/g for coffee bean raw processing. Univariate and multivariate analyses showed significant differences (P ≤ 0.05) among the cultivars. A linear discriminant function based on twelve variables measured on several dates in two consecutive harvest years showed that 'Typica' and 'Mundo Novo' had high efficiencies in conversions from cherry to green coffee on three harvest dates in 1999 and one in 2000. In contrast, 'Bourbon' and 'Yellow Caturra' required greater amount of fresh fruit to obtain 46 kg (1 quintal) of green coffee. The cultivar effects on the parchment to green coffee bean yield were not clearly identified. Harvest dates studied did not significantly influence the conversion of cherry or parchment to green coffee bean yields in the two years evaluated. Se estudiaron conversiones de café cereza y café pergamino a granos de café verde o pilado (Coffea arabicaL.) en ocho cultivares de cafeto, durante dos años consecutivos de cosecha en México. Un 'balance de masas' fue útil en ajusfar la humedad del fruto a 0.12 g/g para granos de café a procesar. Análisis univariados y multivariados mostraron diferencias significativas (P ≤  0.05) entre los cultivares. Una función lineal discriminante basada en doce variables medidas en varias fechas durante dos años consecutivos de cosecha mostró que 'Typica' y 'Mundo Novo' tuvieron una alta eficiencia en conversiones de café cereza a granos de café verde en tres épocas de cosecha en 1999 y una en el 2000. En contraste, 'Bourbon' y 'Caturra Amarillo' requirieron una mayor cantidad de fruto fresco o café cereza para obtener 46 kg (1 Qq) de granos de café verde. La influencia de los cultivares en el rendimiento industrial de café pergamino a granos de café verde no se identificó claramente. Las fechas de corte estudiadas no influyeron significativamente en la conversión de café cereza o café pergamino a granos de café verde en dos años de estudio

Antioxidant capacity of capulin (Prunus serotina subsp. capuli (Cav). McVaugh) fruit at different stages of ripening

Prunus serotina is a species that grows wild or under cultivated conditions in several regions of the Americas, and is considered as a potential source of antioxidants. The study aimed to evaluate the concentration changes in compounds that contribute to the antioxidant capacity in capulin (Prunus serotina) fruit during the ripening process, in order to define when the maximum concentration is reached and thus establish a harvest index for the fruit. Antioxidant capacity was evaluated by spectroscopic methods. A completely randomized simple factor design was used for the statistical analysis. It was found that the content of total phenols and flavonoids decreased significantly at the S3 ripening stage (93 days after anthesis, DAA). Total anthocyanins increased significantly to 1.4 mg Cyanidin-3-glucoside gdb−1.The antioxidant capacity of the fruit had a maximum value of 63.7 µmol TE gdb−1 at the S3 ripening stage (93 DAA). Results indicated that the antioxidant capacity of the fruit is related to the content of total flavonoids and is higher before reaching the characteristic purple coloration, which is a consumption indicator.Prunus serotina es una especie que crece silvestre o en condiciones de cultivo en diversas regiones de América, y es considerada como una fuente potencial de antioxidantes. El objetivo de esta investigación fue evaluar los cambios de concentración en los compuestos que contribuyen a la capacidad antioxidante en frutos de capulin (Prunus serotina) durante el proceso de maduración, para definir el momento en que se alcanza la máxima concentración y así establecer el índice de cosecha de los frutos. La capacidad antioxidante se evaluó mediante métodos espectroscópicos. Para el análisis estadístico se utilizó un diseño de factor simple completamente aleatorizado. Se encontró que el contenido de fenoles y flavonoides disminuyó significativamente en la etapa de maduración S3 (93 DDA). Las antocianinas totales incrementaron significativamente hasta 1.4 mg Cyanidin-3-glucosido gbs−1 La capacidad antioxidante de los frutos tuvo un valor máximo de 63.7 µmol ET gbs−1 en la etapa de maduración S3. Los resultados indicaron que la capacidad antioxidante de los frutos está relacionada con el contenido de flavonoides totales y es mayor antes de alcanzar la coloración purpura característica, que es un indicador de consumo

Potencial bioquímico de metano de pollinaza adicionada con propionato en condiciones mesofílicas

El objetivo del trabajo fue determinar el potencial bioquímico de metano de pollinaza en combinación con una alta concentración de propionato, empleando un consorcio microbiano previamente adaptado a elevadas cantidades de este metabolito. La pollinaza al 3 % de sólidos totales (ST) con 4895 ppm de propionato fue degradada en condiciones mesofílicas empleando microcosmos con un volumen de trabajo de 250 mL. Los resultados del rendimiento de metano acumulado indicaron un comportamiento triple sigmoidal; lo cual podría atribuirse a la diferencia en las velocidades de degradación de los componentes, tales como macromoléculas y ácidos grasos volátiles. El potencial bioquímico de metano fue de 364,52 mL CH4 gSValimentados-1.

La agroindustria láctea en el Valle de México: un ensayo de categorización

Milk industry companies located in the metropolitan area of Mexico City show very different development dynamics, presenting different technological levels. In the present study, a technological grading proposal for the milk industry enterprises of the Valley of Mexico, based on their technological status, is uncovered. The methodology includes analysis of technological indicators through the use of multivariate analysis techniques. The sample employed in this study included 14 % of the regional firms, chosen at random. Results permitted setting up four groups of processing enterprises: leaders, growing, fossil, and decaying. The particular characteristics of each group, considering a highly competitive environment, were analyzed.Las empresas transformadoras de leche localizadas en el área metropolitana de la ciudad de México presentan dinámicas de desarrollo muy diferentes, lo cual se manifiesta en diversos niveles tecnológicos. En este trabajo se presenta una propuesta de clasificación tecnológica de las agroindustrias lácteas del Valle de México, con base en su estatus tecnológico. La metodología empleada incluye el análisis de indicadores tecnológicos por medio de técnicas de análisis multivariado. La muestra empleada para el estudio incluyó al 14 % de las empresas de la región, elegidas aleatoriamente. Los resultados permitieron diferenciar cuatro grupos de firmas: empresas líderes, en expansión, fósiles y en decadencia. Se analizaron las características peculiares de cada uno de los tipos de empresas, considerando el entorno altamente competitivo