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.

Review on the mass transfer performance of CO2 absorption by amine-based solvents in low- and high-pressure absorption packed columns

Abstract: The gas-phase volumetric overall mass transfer coefficient (KGaV) plays a key role in the assessment of an absorption packed column's performance since it determines the height of an absorber column. The effective and useable data provided by KGaV is necessary for designing and scaling up absorption packed columns. This study provides the first comprehensive review of mass transfer performance in terms of KGaV for CO2 (KGCO2aV) absorption into amine solutions for absorber columns with random and structured packing. To date, researchers associated with the KGCO2aV parameter have focused on two main fields: experimental works and developing empirical correlations. For experimental works, KGCO2aV has been evaluated in the literature for a large number of conventional and improved amines over a range of operating parameters in laboratory-scale packed columns. In addition, researchers have developed empirical correlations for KGCO2aV based on operating parameters affecting KGCO2aV and physical properties. The details of research determining the KGCO2aV have been reviewed for low- and high-pressure absorption packed columns. Finally, directions for future research of the mass transfer performance for absorber packed columns in the CO2 capture process have been discussed.

Liquid-phase volumetric and mass-transfer coefficient, and boundary of hydrodynamic flow region in packed column with cocurrent downward flow.

Abstract: Liquid-phase volumetric coefficients and Peclet numbers in liquid mixing were measured in packed columns with cocurrent downwardflow. The empirical equations of liquid-phase volumetric coefficient are distinctly different in spray, pulse and dispersed bubble flow regions. The boundaries for the respective flow regions, obtained by combining two of these equations of volumetric coefficient, are in good agreement with the boundaries which have previously been given from the equations of interfacial area in the same fashion. The foam flow region, which gives the maximumvalue of liquid-phase mass-transfer coefficient, was found at higher gas Reynolds number in comparison with pulse and dispersed bubble flow regions. Taking the ratio of packing to column diameter dp/T and surface shape factor of packing into consideration, the empirical equation of mass-transfer coefficient is presented in respective flow regions as

Using a Multiregion Model to Study the Effects of Advective and Diffusive Mass Transfer on Local Physical Nonequilibrium and Solute Mobility in a Structured Soil

Abstract: Waste management problems for shallow land burial facilities in the humid eastern United States are usually complicated by slow but continuous movement of wastes through the soil matrix and discrete but rapid pulses of wastes through macropores and fractures. Multiple-pore-region models employed to describe flow and solute transport in the soils usually consist of multiple mass transfer coefficients that cannot be measured experimentally, and their effects on subsurface mass transport are poorly understood. The objective of this research was to study the individual and concurrent effects of interaggregate advection and diffusion on mass transport in a structured soil. The interactions of these two mass transfer processes and local solute concentration equilibrium are examined for a heterogeneous soil. Pore region water retention, hydraulic conductivity, and dispersivities, obtained from independent measurements and published calibration results, were used to test a novel three-pore-region, one-dimensional numerical model. Advective and diffusive mass transfer coefficients were estimated using mass transfer equations and fracture spacings published in the literature. The mass transfer coefficients were then varied systematically, and the sensitivity of local fluid pressure and solute concentration nonequilibrium to interregion mass transfer were analyzed. Our results indicated that time-dependent interaggregate advection and diffusion were important processes controlling solute mobility in heterogeneous media. Under transient flow conditions, interaggregate advection may reduce the significance of interaggregate diffusion that otherwise dominates interaggregate mass transfer under steady state conditions. Nonetheless, the equilibrium of local solute concentrations was 20 times more sensitive to diffusive mass transfer than to advective mass transfer, which suggests that site characterization efforts should be directed more toward the former process. Unfortunately, characterization efforts of this type are not commonplace and if available are frequently ignored because they add a difficult reality to complex waste management problems. Since advective and diffusive mass transfer may be important processes limiting the efficiency of cleanup activities such as pump and treat, it is perhaps time to include the characterization of these processes and quantification of the timescale of physical nonequilibrium in site remediation efforts.