Molecular modeling for physical property prediction

Multiscale modeling is becoming the standard approach for process study in a broader framework that promotes computer aided integrated product and process design. In addition to usual purity requirements, end products must meet new constraints in terms of environmental impact, safety of goods and people, specific properties. This chapter adresses the use of molecular modeling tools for the prediction of physical property usefull for chemical engineering practice

Generalised model for heteroazeotropic batch distillation with variable decanter hold-up

A general model of batch heteroazeotropic distillation is proposed. Both liquid phases present in the decanter can be refluxed or withdrawn as distillate, their hold-up can be increased, decreased or kept constant, as well. By assuming maximal separation, that is, that the composition of the condensate always equals to that of the heteroazeotrope, the still path equation was derived. The still path directions are determined for all the 16 possible operational policies. It is possible to steer the still path in a desired direction by changing the operational parameters, which allows the recovery of a pure component in the still. The still path directions are validated by rigorous simulations for three policies not published yet using the mixture water – formaldehyde – propyl formate. From the 16 operational policies, 11 can be considered as useful in practice. To demonstrate the advantage of using a non-traditional policy, the separation of the mixture aniline – ethylene glycol – water was investigated, as well. By using a non-traditional operational policy with hold-up reduction in the decanter a higher purity of ethylene glycol was obtained in the still

Extending Batch Extractive Distillation Thermodynamic Feasibility Insights to Continuous for Class 1.0-2 Case A

The feasibility of batch and continuous extractive distillation analysis for the separation azeotropic mixtures is addressed. Based on batch feasibility knowledge, batch and continuous separation feasibility is studied under reflux ratio and entrainer flow-rate for a working example ternary system acetone-chloroform-benzene, which belonging to the 1.0-2 class case (a). Possible feasible regions are determined by finding the feasible points based on continuous methodology, they show minimum and maximum feed ratio as a function of the reflux, and a lower bound for the reflux ratio. Later on, simulations verified the feasibility of calculating results based on theoretical methodolog

Effect of operating conditions and physico–chemical properties on the wet granulation kinetics in high shear mixer

The wet granulation process is sensitive to changes in product properties and process variables. The optimal process and formulation are based on the knowledge of the granule growth mechanisms and of the effects of product properties and process variables. This paper presents the study of wet granulation of microcrystalline cellulose powder, MCC (Avicel PH101) using high-shear mixer granulator. It aims at understanding the effect of operating parameters (impeller rotational speed, liquid binder flow ate) and of physicochemical properties (viscosity, wettability) of a binder solution on solid particles surfaces, on the agglomeration kinetics. The experiments are carried out with water, aqueous solutions of sodium carboxymethylcellulose, polyvinylpyrrolidone, hydroxypropylméthylcellulose or a non ionic surfactant oxo-C10C6 at a critical micellar concentration. Concerning the process variables the experimental results show that an optimal interval of impeller speed operation exists ranging from 150 to 200 rpm for granule growth. Below, an uncontrollable agglomerate size and localised over-wetting occur, and above granule breakage occurs. Increasing the liquid binder flow rate reduces the extension of the non growth regime, but does not affect the granule mean size. The effect of the physicochemical properties is evaluated using a modified capillary viscous number, Ca′, that we define as the ratio between the viscous forces (μLU) and the work of adhesion Wa=γL(1+cosθ). For Ca′b1, the viscosity of the solution does not significantly affect the granulation process. The dominant forces in the granulation process are the interfacial forces since increasing the work of adhesion enhances the growth kinetics. For Ca′N1.6, the viscous forces predominate and control the granule growth

From batch to continuous extractive distillation using thermodynamic insight: class 1.0-2 case B

A systematic feasibility analysis is presented for the separation azeotropic mixtures by batch and continuous extractive distillation. Based on batch feasibility knowledge, batch and continuous separation feasibility is studied under reflux ratio and entrainer flow-rate for the ternary system chloroform-vinyl acetate-butyl acetate, which belongs to the class 1.0-2 separating maximum boiling temperature azeotropes using a heavy entrainer. How information on feasibility of batch mode could be extended to the feasibility of continuous mode is then studied, possible feasible regions are determined by finding the feasible points based on continuous methodology, they show minimum and maximum feed ratio as a function of the reflux, and a lower bound for the reflux ratio. Results are validated by simulation

Virtual Environments for Training: From Individual Learning to Collaboration with Humanoids

The next generation of virtual environments for training is oriented towards collaborative aspects. Therefore, we have decided to enhance our platform for virtual training environments, adding collaboration opportunities and integrating humanoids. In this paper we put forward a model of humanoid that suits both virtual humans and representations of real users, according to collaborative training activities. We suggest adaptations to the scenario model of our platform making it possible to write collaborative procedures. We introduce a mechanism of action selection made up of a global repartition and an individual choice. These models are currently being integrated and validated in GVT, a virtual training tool for maintenance of military equipments, developed in collaboration with the French company NEXTER-Group

Crossover soft-SAFT modelling of the CO2+NO2/N2O4 mixture

Accurate thermo-physical properties are mandatory for all industrial applications. However, experimental data are often scarce and models are needed for the estimation of properties. Such is the case in supercritical processes like the selective oxidation of vegetal macromolecules in mixture NO2/N2O4 – supercritical CO2 aiming at producing body-degradable polymers readily usable for inside body surgery. The so-called crossover soft-SAFT equation of state is used to model the pure compounds and the mixture. The quadrupolar effect is explicitly considered when modeling carbon dioxide, obtaining excellent agreement for the whole phase equilibrium diagram. NO2 is modeled as a self associating molecule with a single association site. Finally, CO2 and NO2 pure compound parameters are used to predict the vapor – liquid coexistence of the CO2 + NO2 / N2O4 mixture at different temperatures. Experimental pressure – CO2 mass fraction isotherms recently measured are used for comparison. Good agreement is obtained with the use of a unique binary parameter, independent of thermodynamic conditions, although more experimental data would be useful to conclude about the accuracy of the calculation

Flash-Point prediction for binary partially miscible aqueous-organic mixtures

Flash point is the most important variable used to characterize fire and explosion hazard of liquids. Herein, partially miscible mixtures are presented within the context of liquid-liquid extraction processes and heterogeneous distillation processes. This paper describes development of a model for predicting the flash point of binary partially miscible mixtures of aqueous-organic system. To confirm the predictive efficiency of the derived flash points, the model was verified by comparing the predicted values with the experimental data for the studied mixtures: water + 1-butanol; water + 2-butanol; water + isobutanol; water + 1-pentanol; and, water + octane. Results reveal that immiscibility in the two liquid phases should not be ignored in the prediction of flash point. Overall, the predictive results of this proposed model describe the experimental data well when using the LLE and VLE parameters to estimate sequentially the span of two liquid phases and the flash point, respectively. Potential application for the model concerns the assessment of fire and explosion hazards, and the development of inherently safer designs for chemical processes containing binary partially miscible mixtures of aqueous-organic system

Flash Point Measurements and Modeling for Ternary Partially Miscible Aqueous­Organic Mixtures

Flash point is the most important variable used to characterize the fire and explosion hazard of liquids. This paper presents the first partially miscible aqueousorganic mixtures flash point measurements and modeling for the ternary type-I mixtures, water + ethanol + 1-butanol, water + ethanol + 2-butanol, and the type-II mixture, water + 1-butanol + 2-butanol. Results reveal that the flash points are constant in each tie line. Handling the non-ideality of the liquid phase through the use of activity coefficient models, the general flash-point model of Liaw et al. extended to partially miscible mixtures predicts the experimental data well when using literature LLE and the VLE activity coefficient model binary parameters to estimate sequentially the span and flash point in each tie line and the flash point in the mutual solubility region, respectively. The constant flash-point behavior in a tie line is also observed and predicted, in agreement with the VLLE tie line property that a single vapor is in equilibrium with all liquid composition on a tie line. For the aqueousorganic mixtures here studied, a deviation between prediction and measurements is observed, arising from the failure of the constant lower flammable limit assumption in the mutual solubility inert-rich region. Potential application for the model concerns the assessment of fire and explosion hazards and the development of inherently safer designs for chemical processes containing partially miscible aqueousorganic mixtures

Close-packing transitions in clusters of Lennard-Jones spheres

The structures of clusters of spherical and homogeneous particles are investigated using a combination of global optimization methods. The pairwise potential between particles is integrated exactly from elementary Lennard-Jones interactions, and the use of reduced units allows us to get insight into the effects of the particle diameter. As the diameter increases, the potential becomes very sharp, and the cluster structure generally changes from icosahedral (small radius) to close-packed cubic (large radius), possibly through intermediate decahedral shapes. The results are interpreted in terms of the effective range of the potential