Carmen Riverol

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.

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.

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.

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.

Nonlinear control of an evaporator using an error trajectory technique

This paper outlines the successful application of an adaptive control method in an industrial environment. The control strategy incorporated MRAC (Model Reference Adaptive Control) using an adaptive PID where the adaptive parameter was estimated using a macroscopic energy balance over the control zone based on the concept of a tracking error trajectory. Success is demonstrated in a plant for sugar production where the formation of candy, due to incorrect management, the steam flow to the evaporators prevented the sugar syrups leaving the system to pass to the centrifugal screens. This stopped production three or four times a day for 30min, leading to serious problems in relation to cost and quality, the evaporators being very sensitive to temperature changes.

An approach to control of bioreactors. Application of the gain-scheduling method

A control system based on a combination of the gain-scheduling control method and an adaptive PID controller was designed for the production of xylose from hardwood hemicellulose using a stirring tank reactor. Different operating conditions have been considered for estimating the adjustable parameter (θ) to take into account the changes of energy of the system. The performance of the control system was studied first by numerical simulation, and after implementation in the stirred tank reactor where the controller actually works.