Domingos Barbosa

A simulated annealing approach to the solution of minlp problems

An algorithm (M-SIMPSA) suitable for the optimization of mixed integer non-linear programming (MINLP) problems is presented. A recently proposed continuous non-linear solver (SIMPSA) is used to update the continuous parameters, and the Metropolis algorithm is used to update the complete solution vector of decision variables. The M-SIMPSA algorithm, which does not require feasible initial points or any problem decomposition, was tested with several functions published in the literature, and results were compared with those obtained with a robust adaptive random search method. For ill-conditioned problems, the proposed approach is shown to be more reliable and more efficient as regards the overcoming of difficulties associated with local optima and in the ability to reach feasibility. The results obtained reveal its adequacy for the optimization of MINLP problems encountered in chemical engineering practice.

The simple distillation of homogeneous reactive mixtures

Abstract The equations describing the simple distillation of homogeneous reactive mixtures are derived, and residue curve maps are computed for ideal and non-ideal systems. These maps show that, by allowing the components of a liquid mixture to react, we can either create or eliminate distillation boundaries. It is also shown that not all non-reactive azeotropes appear as products of the distillation process. Knowledge of these features is fundamental for the design and synthesis of sequences of reactive distillation columns.

Design and minimum-reflux calculations for single-feed multicomponent reactive distillation columns

Abstract A new set of transformed composition variables is introduced to simplify the design equations for single-feed, multicomponent reactive distillation columns. Based onthese equations, a general method of calculating minimum reflux ratios for reactive distillation columns is presented. The new composition variables are also used to derive simple relationships between the dependent design variables which are not evident when the design equations are written in terms of mole fractions.

The influence of equilibrium chemical reactions on vapor—liquid phase diagrams

Phase diagrams for simultaneous chemical reaction and phase equilibrium are presented for ideal and non-ideal systems. It is shown that reactive-azeotropes can occur even for ideal mixtures. The conditions for formation of reactive-azeotropes in constant-volatility systems are derived. These conditions show that for such systems reactive-azeotropes can occur only when the volatilities of the reactants are either all higher or all lower than the volatilities of the products.

Optimization of reactive distillation processes with simulated annealing

A simulated annealing-based algorithm (MSIMPSA) suitable for the optimization of mixed integer non-linear programming (MINLP) problems was applied to the synthesis of a non-equilibrium reactive distillation column. A simulation model based on an extension of conventional distillation is proposed for the simulation step of the optimization problem. In the case of ideal vapor}liquid equilibrium, the simulation results are similar to those obtained by Ciric and Gu (1994, AIChE Journal, 40(9), 1479) using the GAMS environment and to those obtained with the AspenPlus modular simulator. The optimization results are also similar to those previously reported and similar to those using an adaptive random search algorithm (MSGA). The optimizations were also performed with non-ideal vapor}liquid equilibrium, considering either distributed feed and reaction trays or single feed and reaction tray. The results show that the optimized objective function values are very similar, and mostly independent of the number of trays and of the reaction distribution. It is shown that the proposed simulation/optimization equation-oriented environments are capable of providing optimized solutions which are close to the global optimum, and reveal its adequacy for the optimization of reactive distillation problems encountered in chemical engineering practice. ( 2000 Elsevier Science Ltd. All rights reserved.

A new set of composition variables for the representation of reactive-phase diagrams

A set of transformed composition variables is introduced for the representation of reactive-phase diagrams. These variables are superior to mole fractions because in the new representation, the non-reactive limits are well defined, the equilibrium surfaces are tangent at azeotropic states, and the number of linearly independent transformed composition variables coincides with the number of independent variables that describe the chemical equilibrium problem. Some examples of reactive-phase diagrams, which emphasize these features, are given.

Theory of phase diagrams and azeotropic conditions for two-phase reactive systems

Expressions for the partial derivatives of the intensive properties that characterize the equilibrium states in two-phase systems, in which the components undergo one equilibrium chemical reaction, are derived. The necessary and sufficient conditions for an azeotropic transformation to occur are found. It is shown that whereas stationary points in the isobaric temperature-composition or isothermal pressure-composition equilibrium surfaces correspond to the formation of reactive azeotropes, reactive azeotropes do not necessarily correspond to stationary points in these equilibrium surfaces. The conditions under which reactive azeotropes are not equivalent to stationary points in the equilibrium surfaces are presented.

Remediation of soils contaminated with pesticides: a review.

The aim of this work is to address the problem of soil contamination with pesticides and present a review of the existing techniques for remediation of these types of soils. First, a brief discussion of the soil structure and complexity is presented, and the impact of its contamination by pesticides is examined. Then, the main existing and emerging techniques for soil remediation, particularly for the elimination of pesticides, is discussed, and their relative advantages and disadvantages presented. In order to choose the best remediation technology, one must take into consideration the soil and site characteristics, the technique suitability, the costs and the environmental footprint. The comparison of existing technologies will be a helpful tool for a preliminary selection of the most promising techniques to use for a particular soil decontamination problem.

High pressure vapor-liquid equilibrium data for the systems carbon dioxide/2-methyl-1-propanol and carbon dioxide/3-methyl-1-butanol at 288.2, 303.2 and 313.2 K

In this work, we report vapor–liquid equilibrium data for the systems carbon dioxide (CO2)/iso-butanol and CO2/iso-pentanol at 288.2, 303.2 and 313.2 K, and for pressures up to the critical point. The interaction parameters for the Soave–Redlich–Kwong (SRK) and Peng–Robinson (PR) equations of state (EOS) that best fit the experimental results are also given.

High pressure phase equilibrium data for the systems carbon dioxide/ethyl acetate and carbon dioxide/isoamyl acetate at 295.2, 303.2 and 313.2 K

Abstract Phase equilibrium data for the systems carbon dioxide/ethyl acetate and carbon dioxide/isoamyl acetate at the temperatures of 295.2, 303.2 and 313.2xa0K, and for pressures up to the critical point, is given. The experimental results are correlated by the Soave–Redlich–Kwong and Peng–Robinson equations of state, and the associated interaction parameters reported.