Liquid Solid Mass Transfer Coefficient Research Articles

Solid–liquid mass transfer in a gas–liquid–solid three-phase reversed flow jet loop reactor

Solid–liquid mass transfer in gas–liquid–solid three-phase reversed flow jet loop reactors was experimentally investigated by means of an electrochemical method, and the effects of liquid jet flow rate, gas jet flow rate, particle size, particle density and nozzle diameter on the solid–liquid mass transfer coefficient were evaluated. The solid–liquid mass transfer coefficients in gas–liquid–solid three-phase reversed flow jet loop reactors are higher than those in the corresponding liquid–solid two-phase reversed flow jet loop reactors. A generalized correlation is developed which more accurately and conveniently predicts solid–liquid mass transfer in gas–liquid–solid three-phase reversed flow jet loop reactors.

Mass Transfer Characteristics during the Removal of Dissolved Heavy Metals from Waste Solutions in Gas Sparged Fluidized Beds of Ion Exchange Resins

The paper presents experimental results concerning the removal of cupric ions from a simulated wastewater effluent consisting of copper sulphate solution in a gas sparged fluidized bed of cation exchange resin. Variables investigated were: superficial gas velocity, particle diameter, bed height and the physical properties of the solution (adding glycerol). These variables were studied with respect to their effect on the solid-liquid mass transfer coefficient. The coefficient was found to increase with increasing superficial gas velocity. Increasing both particle diameter and bed height were found to reduce the mass transfer coefficient. The experimental data can be correlated by the equation J = 0.68 (Fr Re )–0.143 (dp/d)–0.62 (dp/L)0.55valid for the following conditions: 1430 < Sc < 2488; 0.017 < Fr Re < 1.41; 6.33 × 10–3 < dp/d < 0.021 and 9.5 × 10–3 < dp / L < 0.125.

Purification of alpha-glucosidae and invertase from bakers' yeast on modified polymeric supports.

In the present work Amberlite XAD-16 and Indion NPA-1, Polystyrene Divinylbenzene macroreticular spherical resins, have been evaluated quantitatively as supports for the adsorption and isolation of the yeast proteins and the enzymes, invertase and alpha-glucosidase. Modification of these supports has been carried out by surface grafting using acrylate polymers to reduce the hydrophobicity and nonspecific adsorption of proteins. Good grafting efficiency, in excess of 90%, has been obtained using ultrasonic irradiation for the surface activation of polystyrene resins. XAD-16 has higher adsorption capacities for the total yeast proteins as well as for both the enzymes, alpha-glucosidase and invertase, than NPA-1 in its respective native and grafted form. Adsorption capacities of XAD-16 and NPA-1 in their respective native and grafted forms for alpha-glucosidase are higher than the capacities for invertase. Nonspecific adsorption of total proteins has been reduced considerably after the grafting of acrylate polymers on hydrophobic supports. At the same time selectivity for the adsorption of both the enzymes has been enhanced on grafted supports. The overall solid-liquid adsorption mass transfer coefficient values (Kla) estimated for adsorption of invertase on XAD are lower than those for alpha-glucosidase. Native and grafted resins could be regenerated and reused for adsorption of alpha-glucosidase for two regeneration cycles studied. Storage stability of invertase and alpha-glucosidase is the same on native and grafted form of XAD-16 and is more than the enzymes in the free form.

Intensification of mass transfer in liquid fluidized beds with inert particles

The influence of inert particles on liquid/solid mass transfer is studied in fluidized beds by using a binary-mixture of solids of differing size and density. The addition of inert particles of higher density and smaller diameter, e.g. glass beads, exerts remarkable effects on mass transfer coefficients in comparison to that of mono-component active particles at the same liquid velocity. The extent of the effect on liquid–solid mass transfer coefficients increases with an increasing fraction of the small inert particles in the mixture. The liquid–solid mass transfer coefficients for binary-mixtures are well correlated in terms of dimensionless groups and the voidage parameter.

Mass transfer and reaction in a biofilm airlift suspension reactor

Mass transfer and reaction were studied in a lab-scale biofilm airlift suspension reactor. A new approach for the determination of liquid–solid mass transfer coefficients in biofilm systems under reacting conditions is presented. The method is based on the analysis of oxygen consumption in a biofilm airlift suspension reactor and a biological oxygen–monitoring system and allows the independent estimation of gas–liquid and liquid–solid mass transfer coefficient and biofilm reaction rate. The influence of some operating conditions (solid loading, particle size and gas flow rate) on the liquid–solid mass transfer coefficient in biofilm airlift suspension reactors was investigated and a correlation for the mass transfer to biofilm-coated particles is proposed. Liquid–solid mass transfer to biofilm particles was proven to be mainly influenced by gas velocity, whilst particle size and solid loading had minor effect. The liquid–solid mass transfer coefficient measured for biofilm-coated particles was found to be smaller (by a factor varying from 5 to 25%) than the values reported for rigid particles.

SOLID-LIQUID MASS TRANSFER AND WETTING FACTORS IN TRICKLE BED REACTORS: EFFECT OF THE TYPE OF SOLID PHASE AND THE PRESENCE OF CHEMICAL REACTION

The solid-liquid wetting factor, f, for solid dissolution in a liquid with and without chemical reaction was experimentally determined in a fixed bed three-phase reactor with downward concurrent gas and liquid flows (Trickle Bed Reactor). The method employed consisted of comparing the volumetric solid-liquid mass transfer coefficient obtained when two phases (liquid and gas) circulated through the bed, with those coefficients obtained at liquid full bed conditions, maintaining the intrinsic liquid velocity constant. The chemical system selected was benzoic acid and acetylsalicylic acid as solid phases, water and sodium hydroxide in aqueous solution, and atmospheric air. Experiments were carried out in which the flow of both phases was modified, obtaining a direct dependency of f with the flow and holdup of liquid. The gas flow effect over f was not important in the flow regime studied, defined as the low interaction regime. Furthermore, the wetting factor is not affected by the nature of the solute and by the presence of a chemical reaction.

Performance of a shaking vessel-type bioreactor with a current pole

The performance of a shaking vessel-type bioreactor with a current pole at its central axis was examined experimentally with respect to particle dispersion, power consumption, and solid-liquid mass transfer coefficient. The current pole improved the particle dispersion without an increase in power consumption and reduced the critical circulating frequency for complete suspension. The mass transfer coefficient with a current pole had the same value as that without a current pole above the critical circulating frequency for complete suspension. The shaking vessel-type bioreactor with a current pole was thus very suitable for the mass production of regenerated plantlets from fragmented horseradish hairy roots.

Empirical approach to solid-liquid mass transfer in a three-phase sparged reactor

Solid-liquid mass transfer coefficients were determined in three-phase sparged reactors (TPSRs) using benzoic acid dissolution. Experiments were performed in three acrylic column reactors of internal diameter 0.1, 0.2 and 0.3 m respectively. The superficial gas velocities were varied up to 0.35 m s −1. Using experimental data generated in this work and data reported in the literature for a 0.4-m diameter reactor, the effect of the reactor diameter on the solid-liquid mass transfer coefficient, k SL, was investigated. It is demonstrated that an empirical approach can be used to determine k SL from an appropriate mass transfer correlation useful for the design of TPSRs.

Study of mass transfer characteristics of a cocurrent downflow bubble column reactor using hydrogenation of itaconic acid

The performance of a cocurrent downflow contactor (CDC) bubble column reactor has been examined using a first order reaction involving the palladium catalyzed hydrogenation of itaconic acid. The reaction was carried out at ambient temperature and in the pressure range 110–290 kPa using 5% and 10% w/w Pd/charcoal catalysts in two solvents (water and 2-propanol). The quantitative evaluation of the mass transfer and kinetic parameters was achieved using the classical film model for a first-order reaction. Because of the large specific gas-liquid interfacial area generated in the CDC, k L a, the volumetric gas-liquid mass transfer coefficient, was large (0.4–6 s −1) and was comparable with that of a much smaller stirred reactor ( ∼1 10 in size) with only ∼10% limiting step for this type of reaction, the relative contribution of the gas-liquid mass transfer resistance in the CDC was low (1–50% of the total resistance) compared with the liquid-solid mass transfer and surface reaction resistances for the three-phase catalytic hydrogenation of itaconic acid. The liquid-solid mass transfer coefficient ( k s ) and first-order reaction rate constant ( k 1) in the CDC were similar to those obtained in the stirred reactor with both the liquid-solid mass transfer and surface reaction being important rate steps. However, the magnitude of k s and k 1 depends critically on the method of calculating k s and an independent evaluation of k s should be carried out to obtain more accurate k 1 values. These initial studies indicate that the CDC has good potential as a three phase catalytic reactor and unlike some bubble columns can be used for relatively fast reactions.

Hydrodynamics and mass transfer in a three-phase fixed-bed reactor with cocurrent gas—liquid downflow

The paper presents experimental results concerning dynamic liquid holdup, wetting efficiency and local mass transfer coefficients between the liquid and solid surface in a fixed-bed three-phase reactor, in which both the gas and liquid flow cocurrently downwards. The experiments were conducted for two basic regimes of operation of trickle-bed reactors, namely the gas continuous flow regime and the pulsing flow regime under atmospheric pressure. The measurements of dynamic liquid holdup have been performed for a wide range of gas and liquid flow rates, three different packing diameters, and for two systems of working media of different physical properties. The common correlation developed determines with good accuracy the holdup values in both regimes as well as in the transition region between the two hydrodynamic modes. In experiments concerning the wetting efficiency a dynamic tracer method has been employed, for which an original mathematical model has been formulated. The results are presented in the form of diagrams and appropriate correlating formulae. The experiments concerning local solid—liquid mass transfer coefficients were carried out for two diameters of spherical particles, with the flow rates of both phases and physicochemical properties of the liquid varied over a wide range. The experimental results are correlated and compared with the appropriate literature data. A mathematical model describing the time-varying solid—liquid mass transfer process is formulated for the pulsed flow regime. The time-averaged mass transfer coefficients calculated on the basis of the model developed are compared with the experimental values. A good agreement between these two sets of values fully confirms the assumptions of the model elaborated.

Fractal behaviour of local liquid—solid mass transfer fluctuations at the wall of a trickle-bed reactor

The technique of microelectrodes in a non-conducting wall of a trickle-bed reactor was used to measure the fluctuations of the local liquid-solid mass transfer coefficient (velocity gradient) for different gas and liquid flow rates. The signals obtained have been analysed in terms of fractional Brownian motion (FBM), or more specifically, in terms of Hurst's rescaled range (R/S) analysis, where S, related to the moment of second order of the signal, is supposed to keep, at least, an experimental meaning. This has yielded the estimates for the so-called Hurst exponent, H, of the time series

Solid-liquid mass transfer in the presence of micro-particles during dissolution of iron in a mechanically agitated contactor

Mass transfer between solid particles and liquids frequently occurs in the presence of inert micro-particles during iron removal by precipitation. In this investigation, the influence of inert micro-particles on mass transfer between a coarse active particle and liquid is simulated with the aid of a cementation reaction between cast iron particles and copper sulphate solution in a mechanically agitated contactor. Kaolin, silicon carbide, iron oxide and anatase were used as the inert micro-particles. The reaction was carried out under conditions of mass transfer control. The experimental data agreed well with Sano's semiempirical expression for a solid-liquid mass transfer coefficient based on the specific power group. The presence of inert micro-particles was found to reduce the solid-liquid mass transfer coefficient significantly, depending on volume fraction, size and density. The relative mass transfer factor, α, defined as the ratio of the solid-liquid mass transfer coefficient with and without the presence of inert micro-particles ( κ′ sl / κ′ sl ), was correlated by the expression (SD=8.66%). α = 1 + β ln θ ∗ θ mp where φ mp =the volume fraction of inert micro-particles, φ ∗= the threshold volume fraction below which the inert micro-particles do not influence the mass transfer coefficient; and β=a mass transfer attenuation factor. β and φ ∗ are functions of density and size of inert micro-particles and can be expressed as: β=4.33×10 −5 d mp −0.32 ϱ 1.05; φ ∗=0.17 d mp 0.12 ϱ mp −0.52 . The ranges of variables covered by the correlatiion are: 1.0< d mp<13 μm; 2600< ϱ mp<5300 kg/m 3; 0< φ mp<0.06. The relative mass transfer factor, α, was found to be independent of the coarse active solid phase hold-up up to a volume fraction of 0.04.

Study of pulsing flow in a trickle bed using the electrodiffusion technique

An electrochemical technique is employed for measuring local, instantaneous liquid-solid mass transfer coefficients in downward cocurrent gas-liquid flow through a packed bed under pulsing flow conditions. The technique involves specially designed electrodes of the same dimensions as the packing material. Also microelectrodes on the surface of a particle are tested for flow diagnostics in the microscale. The feasibility of the method is examined. Interpretation of measurements from various electrodes provides information on the pattern of mass transfer and liquid distribution in the packing.

Solid—liquid mass transfer in a non-newtonian liquid fluidized bed

Experiments were conducted to investigate the solid—liquid mass transfer behaviour in a non-newtonian liquid fluidized bed. The column diameter and height of the fluidized bed are 8 cm and 100 cm respectively. Carboxymethyl cellulose (CMC) solution was used as the non-newtonian fluid in this study. Dissolution of benzoic acid pellets into CMC solution was employed to obtain the solid—liquid mass transfer coefficient in the bed. The benzoic acid concentration in CMC solution was measured by titration. The in-bed benzoic acid concentration was examined to justify the use of an axial dispersion model in the evaluation of the mass transfer coefficient in this study. It was found that the mass transfer coefficient was essentially independent of the liquid velocity and particle size. However, it decreased as the CMC solution concentration was increased.

The use of microelectrodes for the determination of flow regimes in a trickle-bed reactor

The utilization of microelectrodes in a non-conducting wall with subsequent signal analysis allowed the determination of flow regime transitions: trickling/pulsing, trickling/dispersed bubble and dispersed bubble/pulsing in a trickle-bed reactor by the analysis of the rate of fluctuation of the liquid—solid mass transfer coefficient (velocity gradient) variations as a function of liquid and gas flow rates.

MULTIPHASE HYDRODYNAMICS AND SOLID-LIQUID MASS TRANSPORT IN AN EXTERNAL-LOOP AIRLIFT REACTOR—A COMPARATIVE STUDY

Abstract The solid-solid mass transfer performance of an external-loop airlift reactor was measured by dissolution of benzoic acid coated on nylon-6 particles, and the hydrodynamics of the gas-liquid-solid multiphase system in the airlift reactor were investigated. The solid-liquid system was designed to simulate the micro-carrier culture of animal cells, and some typical suspensions of immobilized enzyme particles. The solid-liquid mass transfer coefficient remained constant below a superficial air velocity of 0.04 ms−1 for the particles examined, but increased rapidly with further increase in gas velocity. Solids loading (0.3-3.5% w/w) did not affect the mass transfer coefficient in turbulent flow. The mass transfer coefficient was correlated with energy dissipation rate in the airlift reactor. The mass transfer coefficient in stirred vessels, bubble columns, fluidized beds, and airlift reactors was compared. Over an energy dissipation Reynolds number of 4-400, the solid-liquid mass transfer coefficient...

Dynamic response of an isothermal three-phase slurry reactor—II. The PM-PM-HS/ID model: analytical solutions for two kinds of batch operation

The dynamics of an isothermal batch, three-phase slurry reactor with a first-order reaction occurring in uniform spherical catalyst particles have been investigated. Two kinds of batch operation were considered: variable and constant reactant concentrations in the gas phase. Analytical solutions were presented in both cases. The solutions are based on the PM-PM-HS/ID model, which considers perfect mixing (PM) in both gas and liquid phases, homogeneous suspension (HS) of the catalyst particles, and intraparticle diffusion (ID). The solutions are valid for any mode of input perturbation with non-negative and constant initial conditions. For an input perturbation with which the catalyst particles are suddenly introduced into the reactor after the gas and liquid are in equilibrium, the gas reactant in the liquid phase reveals two responses for both kinds of batch operation. In the case of constant gas reactant in the gas phase, the critical condition which distinguishes two responses can be expressed explicitly, and is independent of liquid—solid mass transfer coefficient and intraparticle diffusion coefficient. This makes it possible to determine experimentally the rate constant from the critical condition without evaluating these two mass transfer processes simultaneously.

Dynamic response and parameter estimation in a two-phase continuous flow stirred tank reactor

Based on a three-parameter model, the dynamic response of an isothermal two-phase continuous flow stirred tank reactor with a first-order chemical reaction occurring in uniform spherical catalyst particles was obtained analytically by using the method of Laplace transforms. Three modes of input perturbation are specifically considered in the solution: step change, impulse, and the sudden introduction of catalyst into the reactor. In all cases, it was found that the time domain solution can be divided into three cases by a critical Thiele modulus. This critical Thiele modulus also divides the reactor dynamics into two different responses when the catalyst particles, which are filled with inert liquid initially, are introduced into the reactor at time zero. In terms of the dimensional form, this critical Thiele modulus relates the rate constant with the inlet liquid flow rate and other parameters except for the liquid—solid mass transfer coefficient and intraparticle coefficient. This makes it possible to determine the rate constant directly from the experiments, even though mass transfer resistances are coexistent, by simply manipulating the inlet liquid flow rate.

LIQUID-SOLID MASS TRANSFER IN A THREE PHASE DRAFT TUBE FLUIDIZED BED REACTOR

Abstract Liquid-solid mass transfer coefficients in a three phase draft tube fluidized bed reactor have been measured using spherical ion exchange particles. The particle diameters ranged from 655 to 1119μm and solids volume fractions of approximately 5 and 10% were employed in water at 28°C. The experimental data can be successfully correlated using a Reynolds number derived using Kolmogoroffs theory of isotropic turbulence, although it is doubtful whether isotropic turbulence actually prevails in the fluidized bed over the range of conditions employed. Comparison with correlations determined for bubble columns and gas-liquid fluidized beds is performed. A model which considers the draft tube reactor as comprising two distinct fluid mechanical regions is developed to explain the apparently lower values of mass transfer coefficients obtained in a draft tube as opposed to conventional fluidized bed reactor.

Mass Transfer between Particles and Liquid in Gas-Liquid-Solid Three-Phase Upflow through a Vertical Tube

Solid-liquid mass transfer coefficients have been obtained by measuring the ion-exchange rate in a gas-liquid-solid three-phase upflow through a vertical tube. The three phase is composed of nitrogen gas, an electrolyte solution, and cation-exchange resin beads of 941μm in diameter. Other experimental variables are slurry velocity, gas velocity, and temperature. The mass transfer coefficients increased according to increases in the slurry velocity, gas velocity, and temperature. The experimental results have been correlated by the following equation, previously proposed for a solid-liquid two-phase tube flow:Sh=2+0.47(e1/3Dp4/3/υ)0.63Sc1/360<(e1/3Dp4/3/υ)<400, 269<Sc<641, md<0.01where e, Dp, ν, and md are energy dissipation rate per unit mass of liquid, particle diameter, kinematic viscosity, and delivered concentration of particles, respectively.