Endre Nagy

Nonlinear, coupled mass transfer through a dense membrane

Concentration and/or space-dependent diffusional mass transport through a dense membrane were investigated. A quasi-analytical approach is given in order to calculate the concentration distribution in the membrane and the mass transfer rates in the case of a single component as well as of binary component diffusion transport. Both properties can be expressed by closed mathematical expressions independently of the concentration dependency function of the diffusion coefficient. The coupled binary diffusion was described by the Maxwell-Stefan theory. Two examples of mass transport, namely binary pervaporation of water/ethanol as well as binary separation of methane/ethane by a zeolite membrane, were calculated, which demonstrate the simplicity of the model equations.

Energy demand of biofuel production applying distillation and/or pervaporation

The energy used for distillation can reach the 40 % of the total energy demand in bioethanol production. The pervaporation is an important alternative membrane separation process to distillation that can be applied as a hybrid process or even as a single process to produce high quality of biofuel. It will be shown how the energy demand, MJ/kgEthanol energy, can be saved applying pervaporation process with different separation factors and operating modes. It is stated that relatively high separation factor is needed to lower the energy demand below that of a simple distillation column.

Analysis of mass transfer in hollow-fiber membranes☆

The mixing-cup concentration was investigated under different flow conditions (parabolic flow and plug flow in the lumen side of hollow fibers) and at different values of the concentration-dependent diffusion and solute distribution coefficient. The concentration dependency of both coefficients was defined by two different functions and integrated analytically as examples. The mixing cup concentration was calculated by the numerical method. The mixing cup concentration was plotted as a function of an axial coordinate under different conditions.

Three-phase mass transfer: Effect of the size distribution

The absorption of oxygen into the aqueous phase was measured in the presence of a dispersed silicone oil phase. In the most experiments, a thin, permeable membrane layer resulting from interface polymerization encapsulated the organic droplets. The size distribution and average droplet size, obtained at different stirrer speeds, were measured. Using a heterogeneous, multilayer mass-transfer model, enhancement was predicted as a function of mass-transfer coefficient without particles and average particle size. Enhancements measured and predicted were compared to each other as a function of the dispersed-phase hold-up and the average particle size. It was concluded that the particle size distribution can significantly alter the absorption rate; thus, its effect should take into consideration in the prediction of absorption rate enhancement.

Energy saving processes of biofuel production from fermentation broth

The energy used for distillation in bioethanol production reaches the 40 % of the total energy demand. The pervaporation is an important alternative process to distillation that can be applied as a hybrid process or even as a single process to produce high quality biofuel. It will be shown how the energy demand, MJ/kgEthanol energy, can be saved applying pervaporation process with different separation factors and operating modes. It is stated that relatively high separation factor is needed to lower the energy demand below a simple distillation column.

On Mass Transport Through a Membrane Layer

This chapter serves as a brief survey of the component transport through a solid, dense, or porous membrane both in dilute or concentrated solution, taking into account the independent or coupling diffusion of the components and the diffusion plus convection transport models. The basic mass transfer equations, under different membrane structures and component/membrane interaction, are listed in this chapter. Starting from the chemical potential, the connection between the thermodynamic and Fickian diffusion coefficients, as well as the mass transfer rates with coupling of diffusion, for binary mixture are given. The solution-diffusion model and the important expressions of the convective flow and the convective mass transport will be defined. Then, the Maxwell–Stefan approach is discussed in dense, polymeric, and inorganic (zeolite) membranes. The chemical potential and its associated mass transfer rate equations are given for the Flory–Huggins theory and for the UNIQUAC model. This chapter summarizes the important, most-often applied mass transfer equations for mass transport during membrane separation.

Diffusive Plus Convective Mass Transport Through a Plane Membrane Layer

Mass transport in the presence of convective mass flow is significant in order to predict the reaction process. On the other hand, the use of convective flow is rather rare because the aim is mostly to minimize the outlet rate of the reactant on the permeate side. This chapter gives an account of diffusive plus convective mass transport through a plane membrane layer. Convective mass transport takes place if the transmembrane pressure difference exists between two membrane sides. The investigation of the simultaneous effect of the diffusive and convective flows is important when the measures of two flows are comparable with each other. Several membrane processes are involved in the enlargement of the diffusive driving force by the pressure difference between the two sides of the membrane for mass transport, causing convection flow. The presence of convective flow improves the efficiency of the membrane reactor. In theoretical description of mass transport accompanied by zero-order reaction, the effect of the zero-order reaction is discussed for an intrinsically catalytic membrane layer only. Theoretical descriptions of mass transport with variable parameters and asymmetric catalytic membrane are also illustrated.

Mass Transport Through Biocatalytic Membrane Reactors

A mathematical model and its solution were developed to calculate the mass transport through catalytic membrane layer by means of explicit, closed expressions even in the case of the nonlinear Michaelis-Menten reaction kinetics and/or of variable mass transport — diffusion coefficient, convective velocity — parameters. Some typical examples on the Thiele modulus, applying the Michaelis-Menten kinetics and its limiting cases, namely the first-order kinetic (KM ≫cm ) and zero-order kinetic (cm ≫KM ) are shown for the prediction of the concentration distribution and the mass transfer rates as a function of the reaction modulus, namely first-order- and the zero-order reactions. It was shown the significant differences of the results obtained by the three different reaction orders.Copyright

2,4-Dichlorophenol Enzymatic Removal and Its Kinetic Study Using Horseradish Peroxidase Crosslinked to Nano Spray-Dried Poly(Lactic-Co-Glycolic Acid) Fine Particles

Horseradish peroxidase (HRP) catalyzes the oxidation of aromatic compounds by hydrogen peroxide via insoluble polymer formation, which can be precipitated from the wastewater. For HRP immobilization, poly(lactic-co-glycolic acid) (PLGA) fine carrier supports were produced by using the Nano Spray Dryer B-90. Immobilized HRP was used to remove the persistent 2,4-dichlorophenol from model wastewater. Both extracted (9-16 U/g) and purified HRP (11-25 U/g) retained their activity to a high extent after crosslinking to the PLGA particles. The immobilized enzyme activity was substantially higher in both the acidic and the alkaline pH regions compared with the free enzyme. Optimally, 98% of the 2,4-dichlorophenol could be eliminated using immobilized HRP due to catalytic removal and partly to adsorption on the carrier supports. Immobilized enzyme kinetics for 2,4-dichlorophenol elimination was studied for the first time, and it could be concluded that competitive product inhibition took place.

Second Generation Biofuels and Biorefinery Concepts Focusing on Central Europe

Utilization of the agricultural residues as lignocellulosic biomass should involve economical processes. Accordingly, it is not enough to produce biofuel from the agricultural residues but one should develop chemical/biochemical processes which produce valuable platform chemicals, as well. This paper gives a brief survey on the possible future processes focusing on the Central Europe. Such kind of technological processes should be developed in the next future in this region in order to make the utilization of lignocellulosic biomass profitable.