Estrella Alvarez

Application of the Danckwerts method in a bubble column: Effects of surfactants on mass transfer coefficient and interfacial area

Abstract We determined interfacial areas, A, and individual mass transfer coefficients, kL, for the absorption of CO2 in a bubble column, with an anionic surfactant in the absorbent liquid. The results of experiments to determine the dependence of kL on surface tension of the liquid phase and the superficial velocity of the gas were fitted to within a 10% error by expressions of the form k L =K 4 σ 1.35 u G 0.5 where K4 depends exclusively on the kind of bubbling device. Likewise, the experimental values of specific area, a, were correlated with the column diameter dc and the physical properties by means the following equation: ad c =K· Re 0.98 · Sc 0.57 · Fr 0.09 · Bo −0.70 d p d c −0.19 that reproduces satisfactorily the experimental values.

Influence of surfactants on absorption of CO2 in a stirred tank with and without bubbling

We determined volumetric mass transfer coefficients kLa for the absorption of bubbled and unbubbled CO2 in a stirred tank, with and without surfactants in the absorbent liquid. In the absence of surfactants, results obtained under continuous liquid flow regimes agreed closely with batch results; accordingly, for convenience, subsequent experiments with surfactant additives were performed only with continuous liquid flow. The results of experiments to determine the dependence of kLa on stirring rate and the kind of bubbling device were fitted to within a 4% error by expressions of the form kLa = K(PeN)0.4 where Pe is the effective power supplied to the tank, V is the volume of liquid in the tank and K depends on surfactant concentration and the bubbling device and increases linearly with the liquid flow rate. Surfactant reduced kLa by an amount that, to within a 3% error, was proportional to both the corresponding value of kLa in the absence of surfactant and the surface concentration of surfactant.

Effect of Temperature on Rheological Properties of Different Jams

The rheological behavior of selected jams was analyzed at different temperatures, from 20 to 40°C in a rotational viscosimeter (HAAKE VT550). The rheograms were fitted with Power-Law, Carreau, Herschel-Bulkley, and Cross models. It was observed that the jams presented a pseudoplastic behavior, and the suspended solids influenced the consistency index.

Model based in neural networks for the prediction of the mass transfer coefficients in bubble columns. Study in Newtonian and non-Newtonianian fluids

Numerical simulation is being recognized as a primary tool for improving the performance of process equipment. In particular, for scale-up of chemical reactors a reliable fluid dynamic of bubble column model is of great benefit. Here, comprehensive study for the prediction of the volumetric transfer coefficient K{sub L}a with Newtonian and non-Newtonian fluids in bubble columns is the objective of this work. The evaluation of the hydrodynamic characteristics of the bubble columns and delineated the different hydrodynamic regimes considering column geometry, gas flow, liquid height and type of fluid (Newtonian and non-Newtonian) suggest a general applicability of the proposed model. A new learning pattern based in the design parameters of the bubble columns is proposed.

Comparison of Rheological Behavior of Sweet and Salad Sauces

Abstract A comparative study of different commercial sauces was carried out from a rheological point of view. The different sauces were divided into sweet and salad, and for each sausage the behavior was studied at different temperatures. The power-law parameters, n and k, for sauces were calculated and their variation with the temperature was studied. On the other hand, the activation energy was calculated for the sweet sauces.

Injection of steam into the mashing process as alternative method for the temperature control and low-cost of production

Steam may offer several advantages for commercial brewers as well. For those mashing in unheated tuns, direct steam injection might be a low-cost method of adding heating capability to the tuns for stepped mashes. This might be especially economical for those breweries that already use steam as a source of heat for the kettle. Furthermore, direct injection of steam offers certain advantages over steam jacketed tuns. The heat transfer rate will be higher, because of the absence of an intervening wall between the steam and the mash. Also, because the steam is injected directly into the bulk of the mash rather than at the periphery, the heat distribution will tend to be more even and require less stirring. This method was tested and the results are reported in this paper.

Rheological Characterization of Commercial Baby Fruit Purees

The rheological behaviour of fruit purees was measured at different temperatures (20°C–40°C) in a rotational viscometer. The rheograms were fitted with the Power Law or Ostwald de Waele model, the Herschel-Bulkley model, the Casson model, and the Cross model. The best adjustment was obtained with the Cross model, except for systems fruit purees 2 and 4, which were fitted satisfactorily with Power Law model. Flow curves exhibited at all temperatures a pseudoplastic character after applying a shear stress higher than a critical value.

Fuzzy logic control for the isomerized hop pellets production

Abstract This paper presents an application of fuzzy logic control to isomerized hop pellet production. The hop is very important in the brewing industries because a hop of high quality provides a good aroma to the beer and gives consistency to the foam. The isomerized pellets in this case study, are produced by warming stabilized pellets to approximately 50°C and holding them for one–two weeks. The alpha acids are almost completely isomerized under these conditions. The fuzzy controller was shown to have a high degree of robustness producing good results such that the quality of the product is guaranteed. A comparison with other control approaches widely used in the industry is performed using a nonlinear computer model.

Control of chemical processes using neural networks: implementation in a plant for xylose production

Abstract This work demonstrates the use of artificial intelligence for control of xylose reactor performance in a paper factory. Two types of neural networks are used, a perceptron for the temperature controller and an adaptive formulation for the noise filter. The results show an improvement in the temperature stabilization time with respect to a classic PID control.

Rheological Behavior of Powdered Baby Foods

The rheological properties of four types of powdered baby foods have been investigated. Density and apparent viscosity have been measured at different temperatures. The values of the both properties decrease with the temperature. The experimental data belonging to apparent viscosity are represented by a power law. The relationship between the power law parameters and temperature has been analyzed.