Moises Teles dos Santos

Exergy and Sustainable Development for Chemical Industry Revisited

Abstract It becomes necessary the standardization of environmental sustainability indicators for energy conversion systems as well as the measurement of the impact of their emissions on the environment. The exergy concept has been evaluated as a useful tool for this purpose. It is based on thermodynamic criteria and reveals the transformation capacity of a given energy carrier in the environment and the consumption and depletion flows of the useful resources available on nature. Natural and artificial systems are supported by energy useful potential (exergy) and the evaluation of this exergy consumption in relation to natural resources is an indication of process sustainability. The aim of this work is review the environmental sustainability concepts from the perspective of exergy analysis, show the contribution of exergy to the Life Cycle Analysis and clarify the relations between exergy and environmental impacts measurements. In the final section, we illustrate with two real industrial examples.

Computer-Aided Lipid Design: phase equilibrium modeling for product design

Abstract The aim of this work is to use phase equilibrium modeling as an auxiliary tool for product design, especially for lipids whose desired final properties are directly related to solid fat content (SFC) and melting behaviour through Solid-liquid equilibrium (SLE) modeling. This has been implemented for triacylglycerols mixtures, the main components of vegetable oils, a renewable raw-material for a wide variety of products. Excess Gibbs energy models were used to model the solid phases. Optimization of Gibbs free energy using Generalized Reduced Gradient was performed aiming to compute the number of molecules in each phase at the whole range of melting. As a result, the computed phase diagram was compared with experimental data from literature as well as a DSC curve. The model was also used to simulate a four-component DSC curve as a predictive tool.

Beyond biofuels: economic opportunities, recent advances and challenges in property modeling for vegetable oils

Abstract Despite the greater attention given to biofuels application in the literature, there are many economic and environmental drivers to use vegetables oils (VOs) as a renewable feedstock for other applications. These drivers are discussed in the present work and the technological challenges imposed by this shift towards new VOs uses are also discussed. They are mainly associated to the reaction routes issues, the performance regarding end-user properties, experimental procedures and property prediction models. The need for more holistic approaches (life cycle analysis) is briefly discussed and the potential benefits arising from new computer-aided tools are highlighted as well.

Solid-liquid Equilibrium Modelling and Stability Tests for Triacylglycerols Mixtures

Abstract Computer-Aided Mixture Design for product development can take advantage from equilibrium modelling. Systems composed by triacylglycerols (TAG) mixtures are widely used for many applications (foods, cosmetics, pharmaceutical and lubricants) and their end-use properties are very close related to phase behaviour (melting and crystallization). Such molecules can have different polymorphisms in solid state, leading to a lack of intersolubility and consequently formation of multiple solid phases. This work has implemented the solid-liquid equilibrium for TAG mixtures in a two step approach: stability tests and equilibrium compositions computations for two phase mixtures. The Michelsens method for stability analysis was adapted to cope with polymorphisms and was successful for phase-split detection. Melting curves for mixtures composed by 9 TAGs in different compositions and molecular structures were simulated revealing good agreement with physical background for such systems. Further implementations of other initialization independents stability tests and robust optimization techniques show, therefore, a great potential for use as auxiliary computational framework for match improved mixtures in structured lipids research.

Ternary Blends of Vegetable Oils: Thermal Profile Predictions for Product Design

This work deals with Product Design by means of theoretical predictions of the Solid Fat Content of different formulations using 3 vegetable oils. A Soli-Liquid Equilibrium (SLE) model was implemented and integrated into an optimization algorithm based on the Generalized Reduced Gradient method. A total of 3,696 SLE problems are solved, covering 57 binary blends, 3 pure vegetable oils and 171 ternary blends problems, before and after chemical interesterification reaction and at 8 different temperatures. A combinatorial random distribution of fatty acids in the glycerol structure is used to simulate the effect of the reaction. The results were compared with 256 experimental points, giving an average absolute error of 5.4 and 4.4 in Solid Fat Content for systems before and after reaction, respectively. Computer-aided tools can be useful to deal with the large combinatorial problem faced by product design, especially when desired product performance is related to a phase behavior in multicomponent mixtures.