Carlos Zambra has his expertise in develop of mathematical models applied in computational mechanic to describe in two and three dimensional the transfer of momentum, heat and mass in porous medium. The main interest are the problems that involve chemical and biochemical reactions and new process such as membrane perstraction, pervaporation and membrane distillation.
Osmotic distillation (OD) is a membrane process used to evaporate water from a feed flow at ambient temperature. The most of the current mathematical models are based on phenomenological equations for boundary conditions and an equation for the transmembrane flux regardless the geometry of the membrane. These models are unable of describe the local variation which are product of geometric variables. If these variations were known this would allow improve predictions that can deliver information to build membrane modules with optimal geometries which is very important for efficiency, scalability and durability of them. A general 2D mathematical diffusion model adapted to one cylindrical hollow fiber was solved with the classical finite volume method proposed by Patankar. The boundary conditions consider the effective water activity in the boundary layer which is calculated using the UNIFAC and ASOG models. The accuracy of the solutions obtained with finite volume method are very good for diffusion problems. This is checked comparing the numerical results of a simple case with analytical results. Based on this an algorithm is developed to calculate the diffusion coefficient of gas phase through the membrane as function of feed concentration. In the commercial hollow fiber models the flow at the surfaces it is not the same. Three boundary zones for the mass distribution are clearly defined in studies of the fluid mechanics of hollow fiber modules. This is consider to describe the total mass transfer flow in a complete module used to concentrate cranberry juice. The numerical results allowed to reproduce experimental data of volume decrease of the juice and the augment of its concentration. These studies may be used to find the diffusion coefficient of a gas in a hollow fiber membrane as a function of the feed concentration and to optimize the mass transfer in membrane modules.
Irene Rapone graduated in industrial chemistry at La Sapienza University of Rome. She works in Eni, an Italian oil company, in Renewable Energy & Environmental R&D Center in Novara. She deals with process simulation in the department of process technologies.
The simulation of the FT synthesis section with iron catalyst is the aim of this work: Eni implemented the simulation of the FT reactor using kinetic data from experimental tests performed under kinetic-control and changing the type and design of the reactor. A model for the FT reactor has been developed with uniform and non uniform distribution of catalysts: state-of-the-art and FASTCARD alternative. A first sizing of the reactor has been performed. Moreover, the simulation developed in Eni include the complete FT section, with gas/liquid separation, recycle of not converted gas and purification of products, with the aim of enhancing the fuels recovery. FASTCARD aims to develop nano-designed iron based catalysts specifically for Biomass to Liquid (BTL) applications based on a fundamental understanding of the active sites for CO-hydrogenation and forward and reverse WGS. Eni used the experimental data obtained from its European partners to simulate the FT reactor. The work has included several activities: • Implementation of the correlations found in literature for FT and WGS (water gas shift) reactions in the Eni's proprietary software, called CheOpe (Chemical Operation). • Comparison between the results from different kinetics models (by the process simulator) and the data supplied from European partner (Johnson Matthey) in term of conversion and WGS has allowed to choose the two correlations having the best fit. • Regression of the kinetic model parameters to fit a set of experimental data and use these new modified parameters for the interpretation of new experimental data (all experimental data by Johnson Matthey). • Modelling of FT reactor using the new kinetic model (Figure1): the simulations have taken in to account the problem of heat removal. So the catalyst distribution has been studied in two cases: uniform and not uniform along the reactor. The impact on productivity has been underlined for the two cases. Acknowledgements. The investigation was carried out under the large scale collaborative project FASTCARD ("FAST Industrialisation by Catalysts Research and Development"), European Union 7th Framework Programme, Grant Agreement No 604277”.