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Mass Transfer Processes (mass + transfer_process)
Selected AbstractsInfluence of transverse rotating magnetic field on enhancement of solid dissolution processAICHE JOURNAL, Issue 6 2010Rakoczy Abstract The main objective of this work is to study the effect of transverse rotating magnetic field (TRMF) on the enhancement of solid dissolution process in the novel type reactor (TRMFR). The application of magnetically driven fluidization (MDF with homogeneous and heterogeneous systems) on mass transfer process is presented. A study of the effect of ferromagnetic particles content on solid,liquid mass transfer has been made. The experimental investigations are provided for the explanation of the influence on the dissolution process of a solid body to surrounding its dilute solution in a novel type reactor with the ferromagnetic particles suspended. The mass transfer coefficient is calculated from a kinetic equation and correlated in the relationship including standard and magnetic dimensionless numbers. The overall enhancements due to TRMF and MDF were compared. Unique correlating relations were obtained to generalize the experimental database. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Intensification of liquid,liquid two-phase mass transfer by gas agitation in a microchannelAICHE JOURNAL, Issue 8 2009Yuanhai Su Abstract In this experiment, the inert gas is used to agitate two immiscible fluids in microchannels. The mass transfer performances with or without gas agitation are investigated. 30% TBP (in kerosene)-acetic acid-water is chosen as testing system, and nitrogen as agitating gas. The superficial velocities of the immiscible liquid,liquid two phases and gas phase are varied in the range from 0.02 to 1.2 m/s, and 0 to 3.0 m/s, respectively. In microchannels, with enough gas agitating intensity, high dispersion between two immiscible liquid phases can be obtained. The overall volumetric mean mass transfer coefficients are two-folds higher than those without gas agitating, which are in the range of 3.8,30.6 s,1. Some parameters which impact on the mass transfer process, such as the mixture superficial velocity of the immiscible liquid,liquid two phases, the gas superficial velocity, the microchannel structure, the gas inlet locations and the sampling time are experimentally investigated. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] The Effect of the Anode Loading and Method of MEA Fabrication on DMFC PerformanceFUEL CELLS, Issue 3 2007T. V. Reshetenko Abstract The influence of the Pt-Ru anode loading and MEA preparation techniques on direct methanol fuel cell (DMFC) performance is studied. Two different anode catalyst layer preparation techniques are employed. One is the direct coating of anode catalyst ink on a membrane to form a catalyst coated membrane, CCManode, and the other is the coating of the ink on the diffusion layers, which generates a catalyst coated substrate, CCSanode. The power density of a combined CCManode/CCScathode MEA is higher than for a CCSanode/CCScathode MEA. The main difference in the performance is observed in the high current density region, where two-phase flow is present and mass transfer processes govern the performance. The CCManode and CCSanode have different macroscopic structures, while showing the same microscopic morphology. Based on their morphological differences, it is expected that the combination of the CCManode and carbon paper provides the more homogeneous removal of CO2 at high currents. The authors suggest that the application of the CCManode with an optimal anode loading improves anode mass transfer, reduces methanol crossover, and enhances the electrochemical reactions. [source] Reaction-induced nucleation and growth v. grain coarsening in contact metamorphic, impure carbonatesJOURNAL OF METAMORPHIC GEOLOGY, Issue 8 2010A. BERGER Abstract The understanding of the evolution of microstructures in a metamorphic rock requires insights into the nucleation and growth history of individual grains, as well as the coarsening processes of the entire aggregate. These two processes are compared in impure carbonates from the contact metamorphic aureole of the Adamello pluton (N-Italy). As a function of increasing distance from the pluton contact, the investigated samples have peak metamorphic temperatures ranging from the stability field of diopside/tremolite down to diagenetic conditions. All samples consist of calcite as the dominant matrix phase, but additionally contain variable amounts of other minerals, the so-called second phases. These second phases are mostly silicate minerals and can be described in a KCMASHC system (K2O, CaO, MgO, Al2O3, SiO2, H2O, CO2), but with variable K/Mg ratios. The modelled and observed metamorphic evolution of these samples are combined with the quantification of the microstructures, i.e. mean grain sizes and crystal size distributions. Growth of the matrix phase and second phases strongly depends on each other owing to coupled grain coarsening. The matrix phase is controlled by the interparticle distances between the second phases, while the second phases need the matrix grain boundary network for mass transfer processes during both grain coarsening and mineral reactions. Interestingly, similar final mean grain sizes of primary second phase and second phases newly formed by nucleation are observed, although the latter formed later but at higher temperatures. Moreover, different kinetic processes, attributed to different driving forces for growth of the newly nucleated grains in comparison with coarsening processes of the pre-existing phases, must have been involved. Chemically induced driving forces of grain growth during reactions are orders of magnitudes larger compared to surface energy, allowing new reaction products subjected to fast growth rates to attain similar grain sizes as phases which underwent long-term grain coarsening. In contrast, observed variations in grain size of the same mineral in samples with a similar T,t history indicate that transport properties depend not only on the growth and coarsening kinetics of the second phases but also on the microstructure of the dominant matrix phase during coupled grain coarsening. Resulting microstructural phenomena such as overgrowth and therefore preservation of former stable minerals by the matrix phase may provide new constraints on the temporal variation of microstructures and provide a unique source for the interpretation of the evolution of metamorphic microstructures. [source] Efficiency of non-reactive isothermal bubble column based on mass transferASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2008Subrata Kumar Majumder Assistant Professor Abstract Bubble column reactor as a gas,liquid contactor is extensively used in the chemical and biochemical industries. Mass transfer coefficients governing the transport processes in bubble contactors are a growing concern in chemical and biotechnological processes whose rates are often limited by the mass transfer rate. The influences of different physical, dynamic and geometric variables affect the efficiency characterization of the equipment which are involved in gas/liquid mass transfer processes. This characterization has great importance to optimize the process plant design. In this article, efficiency of two-phase mass transfer in bubble column reactors has been analyzed based on dynamic, geometric and physical variables of the system. An empirical correlation for mass transfer efficiency has also been developed in terms of those variables. The present analysis on the gas,liquid mass transfer efficiency of bubble column may give insight into a further understanding and modeling of multiphase reactors in industrial applications. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | ||||||||||