Comparison Of Mass Transfer Coefficients Research Articles

Comparison of mass transfer coefficients and desorption rates of CO2 absorption into aqueous MEA + ionic liquids solution

The mixed solvent of ionic liquids and ethanolamine (MEA) was used to absorb CO2 from mixed gases using a packed column. The density and viscosity of aqueous MEA+ionic liquids solution were determined at temperatures ranging from 303.15 to 323.15K and ionic liquids mass concentrations from 20% to 30%, respectively. A comparison among the mass transfer of CO2 absorption into MEA+ionic liquids ([Bmim][Br], [Emim][Br]) and MEA was performed at 303.15–323.15K. Meanwhile, the effects of the temperature, liquid flow rate and gas flow rate on the KGav value were discussed in this paper, respectively. At last, the desorption rates of rich solution were calculated by determining the volume of CO2 released from rich solution. The result showed that aqueous MEA+20% [Emim][Br] solution had superior performance for CO2 capture. Moreover, as CO2 was absorbed by the mixture of MEA and ionic liquids, the catalytic action of ionic liquids was not obvious.

A comparison of mass transfer coefficients between trickle-bed, hollow fiber membrane and stirred tank reactors

Trickle-bed reactor (TBR), hollow fiber membrane reactor (HFR) and stirred tank reactor (STR) can be used in fermentation of sparingly soluble gasses such as CO and H2 to produce biofuels and bio-based chemicals. Gas fermenting reactors must provide high mass transfer capabilities that match the kinetic requirements of the microorganisms used. The present study compared the volumetric mass transfer coefficient (KtotA/VL) of three reactor types; the TBR with 3mm and 6mm beads, five different modules of HFRs, and the STR. The analysis was performed using O2 as the gaseous mass transfer agent. The non-porous polydimethylsiloxane (PDMS) HFR provided the highest KtotA/VL (1062h−1), followed by the TBR with 6mm beads (421h−1), and then the STR (114h−1). The mass transfer characteristics in each reactor were affected by agitation speed, and gas and liquid flow rates. Furthermore, issues regarding the comparison of mass transfer coefficients are discussed.

Experimental determination of mass transfer coefficients of volatile sulfur odorants in biofilter media measured by Proton-Transfer-Reaction Mass Spectrometry (PTR-MS)

Mass transfer from air to the liquid phase is an important process that may limit the efficiency of biological air filters used for abatement of odor from livestock production facilities. Mass transfer limitation is especially important for volatile sulfur compounds with relatively low aqueous solubility. A better understanding of limitations of mass transfer is therefore important in order to enhance the performance and design of biofilters. In this study, a method based on Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) has been developed in combination with a developed model to determine the mass transfer coefficients of volatile sulfur compounds for selected packing material used in biofilters. PTR-MS was used to measure breakthrough curves for sulfur compounds with adequate sensitivity, time resolution and reproducibility. The overall mass transfer coefficient for the selected biofilter media was then estimated by fitting an advection–dispersion equation modified for mass transfer between the gas and liquid phases to the measured profile of individual sulfur compound. Different injection strategies were evaluated and an optimal measurement procedure was developed. The method was validated by comparison of mass transfer coefficients to literature values for toluene, which was used as a reference compound in this study. By applying the method to compounds with different Henry’s law constants, the application range of the method was demonstrated regarding solubility in water. This study demonstrates a method for determination of mass transfer coefficients of sparingly soluble gaseous compounds for selected biofilter media by applying PTR-MS in combination with modeling.

Interfacial mass transfer in stripping of phenylalanine in a liquid-liquid extraction process

Stripping of L-phenylalanine from organic phase containing ALIQUAT 336 (tri-octyl-methyl-ammonium chloride) as complexing agent was studied using a stirred transfer cell. The study investigated the effects of concentration of the stripping agent, potassium chloride, in strip solution and temperature on mass transfer rates. A two-film model based on organic and aqueous phases mass transfer resistances was proposed to estimate mass transfer coefficients and it predicted adequately the experimental time-concentration data at different conditions studied. A comparison of mass transfer coefficients for stripping and previously published results on extraction for the same system was made.

Film Cooling Downstream of a Row of Discrete Holes With Compound Angle

A special naphthalene sublimation technique is used to study the film cooling performance downstream of one row of holes of 35 deg inclination angle and 45 deg compound angle with 3d hole spacing and relatively small hole length to diameter ratio (6.3). Both film cooling effectiveness and mass/heat transfer coefficients are determined for blowing rates from 0.5 to 2.0 with density ratio of unity. The mass transfer coefficient is measured using pure air film injection, while the film cooling effectiveness is derived from comparison of mass transfer coefficients obtained following injection of naphthalene-vapor-saturated air with that of pure air injection. This technique enables one to obtain detailed local information on film cooling performance. General agreement is found in local film cooling effectiveness when compared with previous experiments. The laterally averaged effectiveness with compound angle injection is higher than that with inclined holes immediately downstream of injection at a blowing rate of 0.5 and is higher at all locations downstream of injection at larger blowing rates. A large variation of mass transfer coefficients in the lateral direction is observed in the present study. At low blowing rates of 0.5 and 1.0, the laterally averaged mass transfer coefficient is close to that of injection without compound angle. At the highest blowing rate used (2.0), the asymmetric vortex motion under the jets increases the mass transfer coefficient drastically ten diameters downstream of injection.

Film Cooling Effectiveness and Mass/Heat Transfer Coefficient Downstream of One Row of Discrete Holes

A special naphthalene sublimation technique is used to study the film cooling performance downstream of one row of holes of 35 deg inclination angle with 3d hole spacing and relatively small hole length to diameter ratio (L/d = 6.3). Both film cooling effectiveness and mass/heat transfer coefficient are determined for blowing rates from 0.5 to 2.0 with density ratio of 1.0. The mass transfer coefficient is measured using pure air film injection, while the film cooling effectiveness is derived from comparison of mass transfer coefficients obtained following injection of naphthalene-vapor-saturated air with those from pure air injection. This technique enables one to obtain detailed local information on film cooling performance. The laterally averaged and local film cooling effectiveness agree with previous experiments. The difference between mass/heat transfer coefficients and previous heat transfer results indicates that conduction error may play an important role in the earlier heat transfer measurements.

Modeling and application of a semibatch coaxial two‐impinging‐stream contactor for dissolution of solids

AbstractA semibatch, coaxial, two‐impinging‐stream (TIS) contactor was developed and tested for dissolving solid particles of sodium‐nitrate, sodium‐nitrite and urea in water. The feature of the contractor lies in the possibility of increasing and controlling the mean residence time of the particles in the reactor.The mass transfer coefficients determined in the semibatch device, where the water was in a continuous flow and the particles remained in the reactor for a certain period of time, can also be applied to a continuous TIS device. The comparison of mass transfer coefficients with values of other well‐known devices indicated that they are among the highest and that the present contactor is very effective.A physical model was established for the behaviour of the dissolving particles which yielded a two‐parameter correlation for predicting the Sherwood number as a function of the operational parameters.