Mass transfer coefficient

About: Mass transfer coefficient is a research topic. Over the lifetime, 7827 publications have been published within this topic receiving 168354 citations.

The effects of geometry and operational conditions on gas holdup, liquid circulation and mass transfer in an airlift reactor

Abstract: In airlift reactors transport phenomena are achieved by pneumatic agitation and circulation occurs in a defined cyclic pattern through a loop. In the present work, the effect of geometrical relations on gas holdup and liquid velocity, and consequently on the gas-liquid mass transfer coefficient, was studied in a 6-liter airlift bioreactor with AD/AR = 0.63; AD, downcomer cross-sectional area, and AR, riser cross-sectional area. Measurements of the volumetric oxygen transfer coefficient (kLa) were taken in a water-air system using a modified sulfite oxidation method. Different conditions were examined by varying parameters such as superficial air velocity in the riser (UGR), bottom clearance (d1) and top clearance (d2). It was observed from the experimental results that d1 and d2 have a remarkable effect on kLa values. The effect is due to their influence on gas holdup and liquid velocity, consequently affecting kLa. Superficial air velocity in the riser (UGR) ranged from 0.0126 to 0.0440 m.s-1 and kLa varied between 40 to 250 h-1, whereas gas holdup (e) reached values up to 0.2. The volumetric oxygen transfer coefficient (kLa), gas holdup in the riser (eR) and downcomer (eD) and superficial liquid velocity in the riser (ULR) for all the geometrical relations were successfully correlated with dimensionless numbers, namely, the Sherwood number (Sh) and the Froude number (Fr) as well as with geometrical relations such as the bottom space ratio (B = d1/DD) and top space ratio (T = (d2 + DD)/DD).

Liquid-to-particle mass transfer in fixed bed reactor with cocurrent gas-liquid downflow

Abstract: Mass transfer coefficient kls was measured over a range of flow rates of gas Ug= 0-100 cm.s-1 and liquid Ul=0.05-25 cm.s-1 in a column packed with spheres of three different diameters d=2.8-12.7 mm. The systems used were the dissolution of benzoic acid in water and diffusionlimited oxidation of brass with dichromate ion in sulfuric acid solution. The effect of Ug on kls is not found at all in gas continuous flow, is the greatest in pulse flow and becomes less significant again in dispersed bubble flow. The value of kls increases rapidly around the transition from gas continuous to pulse flow. The enhancement factor β (=kls in two-phase flow/kls in single-phase flow) increases from 1.2 to 2 with increasing d in gas continuous flow while it equals the reciprocal of liquid holdup in pulse and dispersed bubble flows. A liquid-film analogy in gas continuous flow and a single-phase analogy in pulse and dispersed bubble flows are proposed and the experimental results are examined in the light of them.

Transport Phenomena for Chemical Reactor Design

Abstract: Preface.PART I: ELEMENTARY TOPICS IN CHEMICAL REACTOR DESIGN.Multiple Chemical Reactions in Plug Flow Tubular Reactors and Continuous Stirred Tank Reactors.Start Up Behaviour of a Series Configuration of Continuous Stirred Tank Reactors.Adiabatic Plug-Flow Tubular Reactor That Produces Methanol Reversibly in the Gas Phase from Carbon Monoxide and Hydrogen.Coupled Heat and Mass Transfer in Nonisothermal Liquid-Phase Tubular Reactors with Strongly Exothermic Chemical Reactions.Multiple Stationary States in Continuous Stirred Tank Reactors.Coupled Heat and Mass Transfer with Chemical Reaction in Batch Reactors.Total Pressure Method of Reaction-Rate Data Analysis.PART II: TRANSPORT PHENOMENA: FUNDAMENTALS AND APPLICATIONS.Applications of the Equations of Change in Fluid Dynamics.Derivation of the Mass Transfer Equation.Dimensional Analysis of the Mass Transfer Equation.Laminar Boundary Layer Mass Transfer around Solid Spheres, Gas Bubbles, and Other Submerged Objects.Dimensional Analysis of the Equations of Change for Fluid Dynamic s Within the Mass Transfer Boundary Layer.Diffusion and Chemical Reaction Across Spherical Gas-Liquid Interfaces.PART III: KINETICS AND ELEMENTARY SURFACE SCIENCE.Kinetic Mechanisms and Rate Expressions for Heterogeneous Surface-Catalyzed Chemical Reactions.PART IV: MASS TRANSFER AND CHEMICAL REACTION IN ISOTHERMAL CATALYTIC PELLETS.Diffusion and Heterogeneous Chemical Reaction in Isothermal Catalytic Pellets.Complete Analytical Solutions for Diffusion and Zeroth-Order Chemical Reactions in Isothermal Catalytic Pellets.Complete Analytical Solutions for Diffusion and First-Order Chemical Reactions in Isothermal Catalytic Pellets.Numerical Solutions for Diffusion and nth-Order Chemical Reactions in Isothermal Catalytic Pellets.Numerical Solutions for Diffusion and Hougen-Watson Chemical Kinetics in Isothermal Catalytic Pellets.Internal Mass Transfer Limitations in Isothermal Catalytic Pellets.Diffusion Coefficients and Damkohler Numbers Within the Internal Pores of Catalytic Pellets.PART V: ISOTHERMAL CHEMICAL REACTOR DESIGN.Isothermal Design of Heterogeneous Packed Catalytic Reactors.Heterogeneous Catalytic Reactors with Metal Catalyst Coated on the Inner Walls of the Flow Channels.Designing a Multicomponent Isothermal Gas-Liquid CSTR for the Chlorination of Benzene to Produce Monochlorobenzene.PART VI: THERMODYNAMICS AND NONISOTHERMAL REACTOR DESIGN.Classical Irreversible Therodynamics of Multicomponent Mixtures.Molecular Flux of Thermal Energy in Binary and Multicomponent Mixtures Via the Formalism of Nonequilibrium Thermodynamics.Thermal Energy Balance in Multicomponent Mixtures and Nonisothermal Effectiveness Factors Via Coupled Heat and Mass Transfer in Porous Catalysts.Statistical Thermodynamics of Ideal Gases.Thermodynamic Stability Criteria for Single-Phase Homogeneous Mixtures.Coupled Heat and Mass Transfer in Packed Catalytic Tubular Reactors That Account for External Transport Limitations.References.Index.