Maria Regina Wolf Maciel

Optimization of biodiesel production from castor oil.

The transesterification of castor oil with ethanol in the presence of sodium ethoxide as catalyst is an exceptional option for the Brazilian biodiesel production, because the castor nut is quite available in the country. Chemically, its oil contains about 90% of ricinoleic acid that gives to the oil some beneficial characteristics such as its alcohol solubility at 30°C. The transesterification variables studied in this work were reaction temperature, catalyst concentration and alcohol oil molar ratio. Through a star configuration experimental design with central points, this study shows that it is possible to achieve the same conversion of esters carrying out the transesterification reaction with a smaller alcohol quantity, and a new methodology was developed to obtain high purity biodiesel.

Considerations on the crystallization modeling: Population balance solution

In crystallization processes, the need to improve the product quality and to minimize production cost requires understanding and optimization on how to obtain an appropriate particle-size distribution. In order to achieve this goal, a model of the process is necessary and the distribution of particles must be represented, which is made through the population balance. This latter constitutes a strongly nonlinear hyperbolic partial differential equation and, in most cases, an analytical solution is not possible, requiring the development and adaptation of numerical techniques. In the present work, it is proposed to analyze the positive and negative aspects of some methods chosen as a tool in the treatment of the population balance equation in crystallization processes. Numerical problems arising from transformation of the partial differential equation, computational effort, as well as the incorrect prediction of the total number of particles and/or no mass conservation of the dispersed phase are discussed.

Dynamic modelling of a three-phase catalytic slurry reactor

Two dynamic models for a three-phase catalytic slurry reactor with appropriate solution procedures were developed in this work. The models consist of mass and heat balance equations for the catalyst particles, for the gas and liquid bulk phases as well as for the heat exchange through the jacket of the reactor. The models of the tubular reactor were applied to describe the dynamic behaviour of the reactor during the hydrogenation of o-cresol on Ni/SiO2 catalyst. These models differ in solid phase modelling, which allows to evaluate the reactor dynamic behaviour prediction capacity. The models successfully reproduce the main characteristics of the reactor dynamic behaviour.

Rigorous modeling and simulation of molecular distillators: development of a simulator under conditions of non ideality of the vapor phase

Abstract In this work, a more rigorous model of the vapor phase was considered in characterizing the molecular distillation more realistically. The model used here tries to predict the behavior of the molecular distillation in terms of several factors that, in a considerable way, influence the evaporation efficiency, e.g. design of the molecular distillators in relation to the distance between the evaporator and the condenser and their geometries, pressure of the system, and condensation temperature. This model was developed in the literature by several authors. The objective here is to consider it in the dismol software (developed by the authors of this work) taking into account the main contributions available.

An alternative process for butanol production: Continuous flash fermentation

The objective of this work is to introduce and demonstrate the technical feasibility of the continuous flash fermentation for the production of butanol. The evaluation was carried out through mathematical modeling and computer simulation which is a good approach in such a process development stage. The process consists of three interconnected units, as follows: the fermentor, the cell retention system (tangential microfiltration) and the vacuum flash vessel (responsible for the continuous recovery of butanol from the broth). The efficiency of this process was experimentally validated for the ethanol fermentation, whose main results are also shown. With the proposed design the concentration of butanol in the fermentor was lowered from 11.3 to 7.8 g/l, which represented a significant reduction in the inhibitory effect. As a result, the final concentration of butanol was 28.2 g/l for a broth with 140 g/l of glucose. Solvents productivity and yield were, respectively, 11.7 g/l.h and 33.5 % for a sugar conversion of 95.6 %. Positive aspects about the flash fermentation process are the solvents productivity, the use of concentrated sugar solution and the final butanol concentration. The last two features can be responsible for a meaningful reduction in the distillation costs and result in environmental benefits due to lower quantities of wastewater generated by the process.

Factorial design technique applied to genetic algorithm parameters in a batch cooling crystallization optimisation

An original approach is proposed in this work for the evaluation of genetic algorithm (GA) applied to a batch cooling crystallization optimisation. Since a lot of parameters must be set in a GA in order to perform an optimisation study, factorial design, a well-known technique for the selection of the variables with the most meaningful effects on a response, is applied in an optimisation problem solved through GA. No systematic approach to establish the best set of parameters for GA was found in literature and a relatively easy to use and meaningful approach is proposed. The results show that the parameters with significant (95% confidence) effect are initial population, the population size and the jump and creep mutation probabilities, being the ones in which alterations should be made during a GA study of optimisation, in the search for the optimum.

Anhydrous bioethanol production using bioglycerol – simulation of extractive distillation processes

Bioethanol has been increasingly used as fuel in the anhydrous form, mixed with gasoline. In this work, two configurations of the extractive distillation process using bioglycerol as a solvent for anhydrous bioethanol production were investigated. Simulations results show that bioglycerol is a suitable agent for the separation of ethanol-water mixtures, with low energy consumption on the column reboilers and the production of high quality anhydrous bioethanol.

Optimization Strategies Based on Sequential Quadratic Programming Applied for a Fermentation Process for Butanol Production

In this work, the mathematical optimization of a continuous flash fermentation process for the production of biobutanol was studied. The process consists of three interconnected units, as follows: fermentor, cell-retention system (tangential microfiltration), and vacuum flash vessel (responsible for the continuous recovery of butanol from the broth). The objective of the optimization was to maximize butanol productivity for a desired substrate conversion. Two strategies were compared for the optimization of the process. In one of them, the process was represented by a deterministic model with kinetic parameters determined experimentally and, in the other, by a statistical model obtained using the factorial design technique combined with simulation. For both strategies, the problem was written as a nonlinear programming problem and was solved with the sequential quadratic programming technique. The results showed that despite the very similar solutions obtained with both strategies, the problems found with the strategy using the deterministic model, such as lack of convergence and high computational time, make the use of the optimization strategy with the statistical model, which showed to be robust and fast, more suitable for the flash fermentation process, being recommended for real-time applications coupling optimization and control.

Excess Gibbs free energies of (n-hexane + propan-1-ol) at 338.15 and 348.15 K and of (n-hexane + propan-2-ol) at 323.15, 338.15, and 348.15 K

The (vapor + liquid) phase equilibria of (n-hexane + propan-1-ol) at 338.15 and 348.15 K and of (n-hexane + propan-2-ol) at 323.15, 338.15, and 348.15 K have been measured using a Fischer recirculating still. Excess molar Gibbs energies GmE were calculated. Thermodynamic consistency was tested by two methods and the results were correlated by use of the Wilson equation. Both mixtures exhibit positive GmE values in the temperature range studied.

Use of experimental design to investigate biodiesel production by multiple-stage Ultra-Shear reactor

This work presents biodiesel production from soybean oil and bioethanol by multiple-stage Ultra-Shear reactor (USR). The experiments were carried out in the following conditions: reaction time from 6 to 12 min; catalyst concentration from 0.5% to 1.5% by weight of soybean oil; ethanol: soybean oil molar ratio from 6:1 to 10:1. The experimental design was used to investigate the influence of process variables on the conversion in biodiesel. The best ethyl ester conversion obtained was 99.26 wt.%, with ethanol:soybean oil molar ratio of 6:1, catalyst concentration of 1.35% and with 12 min of reaction time.