M.R. Wolf-Maciel

Processing modelling development through artificial neural networks and hybrid models

Abstract Developing fully mechanistic models for bioprocess is expensive and time-consuming. On the other hand, using pure ‘black-box’ approaches can lead to a misuse of available information, because there are aspects of the process that can be accurately described by simple equations as, for example, mass balances. This work analyses the use of different types of ‘black-box’ and hybrid models to outline the dynamics of a batch beer production. The hybrid models, combine mechanistic equations with ‘black-box’ techniques (reserved only for the unclear parts of the system), in order to achieve an efficient use of the available information. The hybrid models can also be called ‘grey-box’ approaches. To generate the hybrid models, different level of information is introduced into the ‘black-box’ models, allowing for an interesting model performance comparison in the end. Results demonstrate that the ‘black-box’ models present a good performance in the range of process conditions used to develop them. However, the inclusion of mechanistic knowledge into the hybrid models increase the model extrapolative capability. In this work, artificial neural networks (ANN) are used as the main technique for both the ‘black-box’ models and the ‘black-box’ parts in the hybrid models.

Monoglycerides and Diglycerides Synthesis in a Solvent-Free System by Lipase-Catalyzed Glycerolysis

Five lipases were screened (Thermomyces lanuginosus free and immobilized forms, Candida antarctica B, Candida rugosa, Aspergillus niger, and Rhizomucor miehei) to study their ability to produce monoglycerides (MG) and diglycerides (DG) through enzymatic glycerolysis of soybean oil. Lipase from C. antarctica was further studied to verify the enzyme load (wt% of oil mass), the molar ratio glycerol/oil, and the water content (wt% of glycerol) on the glycerolysis reaction. The best DG and MG productions were in the range 45–48% and 28–30% (w/w, based on the total oil), respectively. Using immobilized lipases, the amount of free fatty acids (FFA) produced was about 5%. However, the amount of FFA produced when using free lipases, with 3.5% extra water in the system, is equivalent to the MG yield, about 23%. The extra water content provides a competition between hydrolysis and glycerolysis reactions, increasing the FFA production.

A cape of HDT industrial reactor for middle distillates

Abstract Hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) of middle distillates over a commercial Ni-Mo/γ-Al2O3 has been studied under wide operating conditions of 340–380°C and 38–98 atm. A power law model was presented to each one of those reactions. The parameters of kinetic equations were estimated solving the ordinary differential equations by the fourth order Runge—Kutta—Gill algorithm and Marquardt method for searching of kinetic parameters (kinetic constants as well as the orders of the reactions). An adiabatic diesel hydrotreating trickle-bed reactor packed with the same catalyst was simulated numerically in order to check up the behavior of this specific reaction system. One-dimensional pseudo-homogeneous model was used in this work. For each feed, the mass and energy balance equations were integrated along the length of the catalytic bed using the fourth Runge—Kutta—Gill method. The performance of two industrial reactors was checked. Alternative configurations are proposed in this work, which have advantages compared with conventional HDT commercial reactors.

Evaluation of liquid-liquid extraction process for separating acrylic acid produced from renewable sugars

In this article, the separation and the purification of the acrylic acid produced from renewable sugars were studied using the liquid-liquid extraction process. Nonrandom two-liquids and universal quasi-chemical models and the prediction method universal quasi-chemical functional activity coefficients were used for generating liquid-liquid equilibrium diagrams for systems made up of acrylic acid, water, and solvents (diisopropyl ether, isopropyl acetate, 2-ethyl hexanol, and methyl isobutyl ketone) and the results were compared with available liquid-liquid equilibrium experimental data. Aspen Plus (Aspen Technology, Inc., version 2004.1) software was used for equilibrium and process calculations. High concentration of acrylic acid was obtained in this article using diisopropyl ether as solvent.

Validations of the nonequilibrium stage model and of a new efficiency correlation for non ideal distillation process through simulated and experimental data

Publisher Summary This chapter discusses the robust software developed for distillation process involving the nonequilibrium stage model, the equilibrium stage model with Barros & Wolf correlation for efficiency calculation, the mass and heat transfer calculations, and the automatic procedure for the comparison of profiles calculated and obtained from experimental data. The case study is the system ethanol/water separation. The performance of the equilibrium stage model with the new correlation for efficiency is compared. An empirical efficiency equation is used to evaluate the behavior of temperature and composition profiles in a distillation column. Equation is obtained based on the techniques of factorial design, and it is dependent on the properties of the mixture, for the calculation of plate and component efficiency. The computing time of the nonequilibrium stage model is quite large for on-line control application; it is very important to carry out the evaluation of the equilibrium stage model using the new efficiency correlation in relation to the more realistic nonequilibrium stage model and also with experimental data.

Dynamic and control of high purity heterogeneous azeotropic distillation process

The three phase azeotropic distillation is a common separation process in chemical and petrochemical industries. This is a complex process, presenting high instabilities. In this work, it was used HYSYS. Plant commercial simulator for calculating the ethanol-water separation using different kiinds of entrainers. The following studies were carried out: steady state and dynamic simulations, which can lead to different process performance according to the liquid phase distribution in the decanter, optimization of the operating conditions in terms of energy consumption and entrainer selection taking into account economical aspects, environmental restrictions and column control.

Evaluation of the batch distillation process in the ethanol production

Abstract Experimental data and simulations in Aspen Plus® for the batch distillation process were obtained from an ethanol/water mixture. The simulation was carried out in order to verify the effectiveness of the calculations for the batch distillation process for recovering ethanol, using a plate column. The experimental data were taken from a packed batch distillation column. The separation of ethanol/water mixture was studied at different reflux ratios. The ethanol was quantified through a gas chromatography analyses. The simulation and the experimental data were performed considering the ethanol concentration in the wine that comes from the sugarcane fermentation. It was verified that the higher ethanol concentration was obtained in one hour of distillation and the accumulate ethanol concentration was above to 80% (mole) when operated at constant reflux. So, it is possible to obtain high yields and concentrations of ethanol in a short time.

On the dynamics of nonequilibrium simple batch distillation processes

Abstract The study of the dynamics of a simple batch distillation usually assumes the equilibrium between the liquid and vapour phases. In contrast to that approach, this work considers the analysis of the dynamic behaviour of a nonequilibrium simple batch distillation. A simple batch distillation device is similar to an evapouration unit because no reflux is employed. A mathematical model and their singular points are analysed through the usual technique of linearization followed by the eigenvalues analysis. The stability nature of those points is presented for ideal solutions. Phase plane plots are made to show the occurrence of some unexpected behaviours such as ‘dynamic azeotropic points’ and ‘inversion of the distillation order’. The dependence of these phenomena on the vapour withdrawal flowrate is established for simple batch distillation.

Evaluation of the Dynamic and Control Strategies of the Vapor Recovery Section of a FCC for a Plantwide Control Design

Abstract The goal of plantwide control studies is to design a control system that can achieve the operating requirements of the complete plant optimal conditions. The problem focuses on the whole plant and not only on single equipment. The size of plantwide control problems are larger than that for individual units, making the solution much more difficult. The main problem is the presence of recycle streams that provide interactions between different equipment. Disturbances that enter a process can propagate not only downstream from one unit operation to the next but upstream through material and energy recycle loops. In this work, the product recovery section of a fluid catalytic unit was used to discuss the optimization and the control of large plants. This unit was chosen because of the presence of four material recycle loops, which allow the observation of equipment coupling. The control system must be able to reject not only local disturbances at the unit level but also at the plant level.

Mathematical development for scaling-up of molecular distillators: Strategy and test with recovering carotenoids from palm oil

Abstract Studies for recovering carotenoids from palm oil were developed in the Separation Process Development Laboratory (LDPS-FEQ-UNICAMP) through molecular distillation process (modeling, simulation and experiments) ( Batistella and Maciel, 1998 ; Batistella et al., 2002 ). All the studies, however, have involved laboratory scale distillators, but due to the success of the developments, a lot of industrial applications are becoming possible. So, aiming to design molecular distillators with industrial dimensions, it is important to develop a methodology looking for an easy and fast form for scaling-up, which is the aim of this work. The procedure makes use of the knowledge obtained from the simulation and operational strategy developed for small scale equipment. Moreover, the nonideality condition of the vaplor phase was considered on the developments of the scale-up ( Batistella et al., 2000 ), since this an important macrobehaviour to be considered. The obtained results show that the developed methodology is robust.