Silvio A.B. Vieira de Melo

Liposomes Size Engineering by Combination of Ethanol Injection and Supercritical Processing

Supercritical fluid extraction using a high-pressure packed tower is proposed not only to remove the ethanol residue from liposome suspensions but also to affect their size and distribution leading the production of nanosomes. Different operating pressures, temperatures, and gas to liquid ratios were explored and ethanol was successfully extracted up to a value of 400 ppm; liposome size and distribution were also reduced by the supercritical processing preserving their integrity, as confirmed by Z-potential data and Trasmission Electron Microscopy observations. Operating at 120 bar and 38°C, nanosomes with a mean diameter of about 180 ± 40 nm and good storage stability were obtained. The supercritical processing did not interfere on drug encapsulation, and no loss of entrapped drug was observed when the water-soluble fluorescein was loaded as a model compound. Fluorescein encapsulation efficiency was 30% if pure water was used during the supercritical extraction as processing fluid; whereas an encapsulation efficiency of 90% was obtained if the liposome suspension was processed in water/fluorescein solution. The described technology is easy to scale up to an industrial production and merge in one step the solvent extraction, liposome size engineering, and an excellent drug encapsulation in a single operation unit.

Supercritical CO2 recovery of caffeine from green coffee oil: new experimental solubility data and modeling

The caffeine solubility in supercritical CO2 was studied by assessing the effects of pressure and temperature on the extraction of green coffee oil (GCO). The Peng-Robinson1 equation of state was used to correlate the solubility of caffeine with a thermodynamic model and two mixing rules were evaluated: the classical mixing rule of van der Waals with two adjustable parameters (PR-VDW) and a density dependent one, proposed by Mohamed and Holder2 with two (PR-MH, two parameters adjusted to the attractive term) and three (PR-MH3 two parameters adjusted to the attractive and one to the repulsive term) adjustable parameters. The best results were obtained with the mixing rule of Mohamed and Holder2 with three parameters.

Critical Analysis of Kinetic Modeling Procedures

In this work, issues related to the mathematical modeling and statistical analyses of kinetic data are discussed. Firstly, problems related to the combinatorial explosion of the number of plausible kinetic models are analyzed, when complex reaction mechanisms are taken into consideration and distinct rate determining steps are assumed. Although modeling procedures based on rate-determining steps can lead to oversimplification of kinetic models, these procedures are still very popular because the existence of multiple rate-determining steps usually renders the analytical derivation of kinetic rate expressions impossible. However, if the derived kinetic models are too simple, one can face serious difficulties to fit the proposed models to available experimental data. Secondly, problems related to the statistical analyses of experimental data are discussed. Particularly, very often statistical tools are used even when some of the fundamental assumptions required for their validity are violated. For this reason, the fundamental grounds that support some of the most popular statistical tools are discussed in the framework of the kinetic analysis.

Failure analysis and design of a front bumper using finite element method along with durability and rig tests

This work presents a case study that comprises the application of the Finite Element Method (FEM) to the design of a front bumper to predict possible failures caused by fatigue. Stress distribution and damage estimates were obtained by using FEM together with rig tests results. Vehicle durability tests were also performed, and geometric changes were proposed in the design of the component analysed based on the simulation results obtained from FEM. A good agreement between experimental data and FEM predictions was found. The case study and results demonstrate that time and cost can be reduced in the course of the product development phase in the automotive industry. FEM also can be used to support decision-making during the design phase of the product.

Valuation of Clean Technology Projects: An Application of Real Options Theory

Abstract The valuation of investment in technologies that minimize the environmental impacts is not an easy task. Investment and environmental damages are partially or totally irreversible, the forecast period for the analysis of such investment is usually long and there are economic and environmental uncertainties which are still enhanced by the fact that environmental damages is not a linear function of the impacts. A better understanding of the behavior of these uncertainties and of the strategies to incorporate these uncertainties in the design valuation would be useful in the decision making associated to the investment with relevant environmental impacts. This work presents an extensive review about the application of the Real Options Analysis in the investment decision associated to the environmental problems and discusses the potential of this technique in the investment analysis of these cases. The aspects discussed denote that the approach of Real Options Analysis is better than the traditional methods and possibly is capable of predicting the benefit obtained with the reduction of the environmental risks provided by the use of clean technology.

Computational Aspects for Optimization of High Pressure Phase Equilibrium for Polymer Industrial Systems

Abstract Many computational problems occur during optimization of high-pressure phase equilibrium of polymer systems due to the existence of critical points and to the possibility of there being more than two equilibrium phases. In this work the main numerical aspects related to high-pressure flash simulation with the Soave-Redlich-Kwong (SRK) and the Sanchez and Lacombe (SL) equations of state are examined. A LDPE (low-density polyethylene) high pressure flash industrial separator is used to case study of 8 resins. The results show that Sanchez-Lacombe equation of state is more appropriate to overcome the numerical difficulties associated with the complexity of polymer systems.

Process integration for industrial water reuse: A case study from a Brazilian biodiesel commercial plant

This paper presents a case study of process integration for a Brazilian biodiesel commercial plant water reuse by using the P+WATER method coupled with Water Sources Diagram (WSD). The process flow diagram of biodiesel plant was simulated considering different operation conditions for transesterification unit, the biodiesel refining unit, and the glycerol recovery unit. WSD was employed to select the main scenarios of waste stream reuse. Statistical techniques were applied to assess the operation cost of each scenario and the respective opportunity to reduce the water consumption by water reuse. The most promising scenarios of waste stream reuse were compared using the P+WATER method to evaluate the opportunity of being really introduced in the industrial plant.

Stress analysis using BEM as support for fatigue life prediction in the automotive industry

Fractures prediction of automotive components through the application of dynamic loads is used to estimate the fatigue life of these components. Numerical methods together with experimental data can provide accurate predictions and also support changes in the component design. The boundary element method (BEM) is a consolidated numerical technique used in the analysis of structural problems in several applications but its use in the automotive industry is not widespread. This work presents a procedure for estimating the fatigue life of automotive components under dynamic loads while considering the effect of geometric changes on them. BEM was applied as an efficient simulation tool to support the design change proposed for the part analysed and also provided an alternative for predicting stresses distribution. Fatigue life prediction obtained from the strain gauge signals was consistent with the results provided by the durability tests performed to verify component functionality including the appearance of fractures.

Computation of Crossover Pressure for Synthesis of Supercritical Fluid Separation Systems

Abstract The crossover region is a phenomenological observation which may be used to synthesize supercritical fluid extraction process (SCFEP) and is supported by a number of experimental studies. This phenomenon means that there may be regions of temperature and pressure in the near critical fluid state where the solute solubility decreases with an isobaric increase in temperature. Accurate calculation of solid solubility in supercritical fluid does not imply that crossover pressure calculation has also good accuracy. In this paper, a new method to predict crossover pressure based on cubic equations of state is developed and applied to systems containing supercritical CO2 and bixin. Peng-Robinson-LCVM-UNIFAC equation of state is used in a predictive way and crossover pressure is determined for several conditions. The method described here can in principle be applied to any solid-fluid system used in supercritical fluid extraction process synthesis.