Mass Transfer Intensification Research Articles

Reactor optimization and process intensification of photocatalysis for capillary-based PMMA LSC-photomicroreactors

As a novel solar reactor, LSC-PhotoMicroreactor (LSC-PM, where LSC denotes luminescent solar concentrator) has shown great potential in efficient, safe and scalable solar production. However, the light-to-chemical energy conversion efficiency is still to be promoted to make LSC-PMs win over the conventional way of chemical production in industry. To this end, intensification of photon transfer and mass transfer was conducted for the present capillary-based PMMA (Polymethyl methacrylate) LSC-PM. A plate-capillary-plate bonding method was used to construct the capillary-based LSC-PM and the material of the capillary was optimized, so as to eliminate photon transfer loss as much as possible inside the photomicroreactor. Moreover, mass transfer was dramatically enhanced by packing microspheres into the capillary of the LSC-PM as indicated by residence time distribution measurement. When the packing (glass bead) size was 850 µm with the capillary inner diameter 2 mm, near plug-flow performance was achieved and the reaction rate was accelerated by 2 times with the high reaction productivity maintained for the model photoreaction. The results obtained in this study not only help LSC-PM advance in respects of energy efficiency and reactor efficiency, but also offer a potential new direction towards the simultaneous intensification of mass and photon transfer for photocatalysis via a single method.

Intensification of the ozone-water mass transfer in an oscillatory flow reactor with innovative design of periodic constrictions: Optimization and application in ozonation water treatment

Ozone-water mass transfer was investigated in continuous mode using a macroscale oscillatory flow reactor provided with smooth periodic constrictions (OFR-SPC). The effects of oscillation amplitude (x0) and frequency (f) on the mass transfer coefficient (kLa) were assessed through a Doehlert experimental design. Different gas and liquid flow rates were also studied. The results show that kLa increases with f (up to 4 Hz), x0 (up to 15 mm), and the gas flow rate (up to 150 Ncm3 min−1). No significant changes in kLa were observed over a wide range of liquid flow rates (up to 180 mL min−1) and for Re0 < 1000. In all conditions studied, and among different reactor configurations tested, the higher kLa values were observed with the OFR-SPC, achieving kLa values up to 35 times higher than those obtained in a conventional bubble column. Moreover, the enhancement on the mass transfer efficiency (MTE) promoted by the oscillatory movement was more pronounced as the gas (ozone) flow rate decreases and liquid (water) flow rate increases, which is another advantage of this system when looking for large-scale implementation of the ozonation process in water treatment. Ozonation experiments using a mixture of fluoroquinolones in different matrices (distilled water, surface water and urban wastewater) were also performed, the results demonstrating that OFR-SPC is an interesting reactor alternative for ozone-driven water treatment.

Construction of a Microchannel Electrochemical Reactor with a Monolithic Porous-Carbon Cathode for Adsorption and Degradation of Organic Pollutants in Several Minutes of Retention Time

A monolithic porous-carbon (MPC) electrode was fabricated to simultaneously intensify mass transfer and enhance reaction activity. The MPC involved channel arrays (about 50 μm of diameter for each channel) with mesopores and micropores in channel walls. The abundant surface pores may improve the reaction efficiency of the reduction of O2 to produce H2O2 and •OH. The function of channel arrays was to shorten the mass-transfer distance not only from O2 to the electrode surface but also from pollutants to the electrode surface and •OH. A microchannel electrochemical reactor was assembled to evaluate the performance of the MPC cathode. For 20 mg/L of phenol, sulfamethoxazole or atrazine, effluent concentration and total organic carbon (TOC) decreased down to 1.5 and 3 mg/L, respectively, in a retention time of only 100-300 s. Phenol removal was dominated by the MPC cathode, and the contribution of cathodic adsorption, cathodic degradation, and anodic reaction was 46, 33, and 8%, respectively. The proper working potential for the MPC cathode was +0.26 to +0.6 V versus reversible hydrogen electrode; in this potential range, no scaling was observed. For the real surface water (the initial TOC was 41.5 mg/L), TOC in effluent (the retention time was 335 s) was stable at 31.0 mg/L.

Towards Enhancing Ozone Diffusion for Water Disinfection—Short Notes

Thanks to its performance in eliminating color, UV absorbance, trace organic compounds, and microorganisms, ozone application in treating water has acquired vogue. The intensification of mass transfer and mixing in ozone-founded disinfection methods stays so crucial to attaining the desired disinfection level at an acceptable price. This work discusses the growing tendency of improving ozone diffusion for better water disinfection. Researchers suggested a new procedure of ozonation supported by a liquid whistle reactor (LWR), which produces hydrodynamic cavitation, for disinfecting water. This integration has been observed to be a cost-efficient method for attaining extreme disinfection paralleled to the solo running of hydrodynamic cavitation (lower magnitude of disinfection) and ozonation (higher prices of treatment frequently attributed to higher cost of ozone production). Further, juxtaposed to the traditional bubble reactor, the achievement of high disinfection performance at a small Ct estimate in a rotating packed bed (RPB) depicted that RPB is an efficacious ozone disinfection contactor for killing microorganisms in water. Finally, electrogenerated ozonation could be a surpassed technique confronted with chlorination in terms of disinfection and poisoning reduction.

Nanoparticle cages as microreactors for producing acrolein from glycerol in the liquid phase

A highly viscous oil phase forms a smaller Pickering emulsion, increasing the acrolein yield from glycerol by intensified mass transfer.

МОДЕЛИРОВАНИЕ КИНЕТИКИ И ДИНАМИКИ ПРОТЕКАНИЯ МАССОПЕРЕНОСА ПРИ РАЗЛИЧНЫХ ВИДАХ КОРРОЗИИ ЦЕМЕНТНЫХ БЕТОНОВ

The article describes the features of various types of cement concrete corrosion: liquid, acid and biological corrosion, which are most often detected at the stage of inspection of concrete and reinforced concrete building struc-tures. The authors consider the possibility of using methods of mathematical modeling appli-cable to corrosion processes, which will deter-mine the intensity of mass transfer and predict the service life of concrete and reinforced con-crete structures. Mathematical models for cor-rosion of the 1st and 2nd types are given, which allow calculating the concentration of “free” calcium hydroxide depending on the thickness of the concrete structure. These mathematical models also allow us to determine the concen-tration of the transferred target component in a liquid acid-salt medium and find the average value of the concentration at any time. One of the important differences of the considered mathematical model for acid corrosion is its dependence on the concentration of the target component in the liquid phase...

Using modeling to select catalyst dilution methods for mass transfer intensification in lab gas–liquid fixed-bed reactors

Heterogeneous catalyst testing methodology at the lab scale must provide intrinsic kinetics data for reactor design purposes as well as the intrinsic activity ranking during catalyst screening in the field of refining and petrochemistry. The significant downscaling of the past century coupled with the increasingly active catalytic formulations may introduce considerable momentum, mass and heat effects in experiments at small scale. Catalyst dilution has emerged as one versatile and robust way to reduce the impact of momentum and heat effects on heterogeneous catalyst testing. This paper presents a methodology based on global phenomena and catalyst dilution modeling to assess and optimize reactor loading techniques for specific problems. More particularly, the aim is to provide catalysts developers and kinetics experts with concrete guidelines for intensifying gas-liquid mass transfer in lab gas–liquid fixed-bed reactors through catalyst dilution. The methodology is applied to the kinetics determination of the oil residue Hydrodemetallation (HDM) and to the screening of catalysts for benzene hydrogenation. Layered dilution, consisting on the split of the catalyst in two beds separated by an intermediate bed containing an inert material of the same size as the catalyst, poorly improves gas–liquid mass transfer. Uniform dilution, based on the direct mixture of catalyst and inert material of the same size, significantly enhances gas–liquid mass transfer as the reactant local consumption per reactor unit volume is strongly reduced. Combinations of both abovementioned dilution techniques can be used with fast and/or high stoichiometric factor chemical systems operated at conversions higher than 70%. A new criterion is proposed to calculate the minimum dilution factor to guarantee negligible gas–liquid mass transfer limitations as a function of conversion, external mass transfer and global pseudo second-order kinetics.

The structure of the confined swirling flow under different phase boundary conditions at the fixed end of the cylinder

The paper analyzes the complex topology of swirling flows generated in the cylinder by its rotating end face. Using the flow visualization for different parameters of swirl of the upper end of the cylinder, the general laws of the evolution of the region with a counter flow (bubble-like vortex decay) are shown regardless of the contact of the studied vortex flow with various liquids or gas at the free end. The research has found for the first time that the scenario for the appearance of the bubble-like breakdown region depends weakly on the properties of the medium that restricts the circulation of the working fluid, but differs significantly from the dynamics of vortex flows limited by the “solid” second wall - the fixed end of the cylinder. For example, during the axial vortex breakdown, the modes of stationary vortex motion with the appearance of the recirculation zone contact with the interface surface of two media have been revealed, which is not typical for closed flows. The results obtained are of interest for further development of vortex devices and reactors that provide complex vortex motion of ingredients for mass transfer intensification, both in terms of optimizing the operation of existing setups and for designing new devices.

Измерение растворимости веществ в сверхкритических флюидных средах динамическим методом

The study of currently known methods and devices for processing plant materials has shown that during the study period, the greatest interest (about 31%) of patent holders is manifested in increasing the yield of extractive substances. If we take as an example a tea leaf, then indeed, the formation of conditions for a more complete release of the target components into the aqueous phase during brewing can provide a more profitable and economical consumption of tea raw materials. The study of the thermodynamic principles of the use of supercritical fluid media and carbon dioxide, in particular, in the processing of plant materials and the processing of tea raw materials, as well as the development of methods for intensifying mass transfer to the aqueous phase when “brewing” tea leaves, are uniquely relevant tasks. An important section of thermodynamics is the concept of phase equilibria in systems of different composition. And one of the key characteristics of phase equilibria is such a thing as the solubility of a substance, including in supercritical fluid media. Since solutions of substances in supercritical fluids are diluted, the dependence of the solubility of substances on temperature, pressure, and density of a pure solvent near its critical point is of practical interest. The results of experimental studies of measuring the solubility of tannin in supercritical carbon dioxide by the dynamic method at a temperature of 308 and 333 K, in the pressure range from 8 to 26 MPa, are presented. The data obtained, firstly, indicate a low solubility of tannin in supercritical carbon dioxide, which is a positive moment for the implementation of the tea leaf pretreatment process in order to improve its biological potential, and secondly, a clear suppression of isolines is observed, which in turn indicates the presence of crossover behavior on solubility isotherms. Based on the results of the obtained experimental data on the solubility of tannin in supercritical carbon dioxide, a mathematical description of the solubility of tannin was carried out by the Peng-Robinson equation of state.

TECHNOLOGY OF CYCLIC DISTILLATION IN ALCOHOL PRODUCTION

Alternate changing of the steaming periods and liquid overflow allows to intensify mass transfer between liquid and steam and to reduce the specific consumption of heating steam in the process of separation of multicomponent mixtures. Known methods and models have not found widespread practical use due to the lack of mass transfer in the steam period, fluctuations in steam pressure in the collector, the complexity of constructive solutions to ensure cyclic mode, etc. The authors propose a technology for rectification, which involves the cyclic motion of the liquid without interrupting of the supply of heating steam and the construction of a rectification column for its implementation. The purpose of the work was to research the effectiveness of the proposed technology in the process of rectification of alcohol-containing fractions and to establish the specific flow rate of steam in the impurity concentration column. To ensure a cyclic mode, the column was equipped with movable liquid transfer devices connected to actuating mechanismes, which acted according to the controller program, and perforated (scale-shaped) trays. The primary task was to determine the hydrodynamic mode of operation of the contact devices - the lower and upper the critical vapor velocity of at which the liquid is retained on the plates and there is its entrainment. It is established that the vapor velocity in the free section of the column can reach 1.2 m/s or more, and in the openings of the scales must exceed the first critical velocity of 6.5-7.5 m/s. The weeping of the tray occurs at the vapor velocity in the holes of 1.5-1 m/s. The investigations were carried out in the production conditions of the Chudniv branch of SE “Zhytomyr liquor producer ”. It is experimentally proved that in the process of rectification of alcohol-containing fractions, the main impurities are removed completely, the degree of extraction of higher fusel alcohols is increased by 38%, methanol - by 15.6 %, the multiplicity of concentration of the main impurities is increased by 25 %, the higher alcohols - by 40 %, methanol – by 34 %, acrolein – by 36 %. The costs of heating steam are reduced by 30 % compared to typical installations and do not exceed 13 kg/dal of absolute alcohol introduced with feed. Exempted from the key impurities the bottom liquid of the impurity concentration column should be used for hydroselection in the purifying column.

Wetting Behavior of the Stainless Steel Wire Mesh with Al2O3 Coatings and Mass Transfer Intensification in a Rotating Packed Bed

An Al2O3-coated stainless steel wire mesh packing was prepared, aiming to serve as the monolithic catalyst support applied in a rotating packed bed (RPB) reactor. Before the application, the wetting behavior and gas–liquid mass transfer performance of Al2O3-coated wire mesh packing were investigated in this work. The results showed that the Al2O3-coated stainless steel fiber had on average 18.8% longer liquid spreading length compared with the uncoated stainless steel fiber. The gas–liquid effective interfacial area (ae) and the volumetric liquid-side mass transfer coefficient (kLae) of the RPB with Al2O3-coated wire mesh packing were on average 25.9 and 45.7% higher than those with uncoated wire mesh packing, respectively. The Al2O3-coated wire mesh packing has great prospects for the catalytic reactions in the RPB reactor by providing double functions of mass transfer intensification and the monolithic catalyst support.

Intensification of CO₂ capture by monoethanolamine solution containing TiO2 nanoparticles in a rotating packed bed

This study investigates the mass transfer intensification in the absorption of carbon dioxide (CO₂) into a monoethanolamine (MEA) solution enhanced by TiO2 nanoparticles in a typical rotating packed bed (RPB). The overall volumetric gas phase mass transfer coefficients (KGa) were investigated in a counter-current RPB with blade packings. The effects of TiO2 and MEA concentrations, rotational speed, initial concentration of CO₂, gas and liquid flow rates on KGa were specified. The rotational speed had positive effects on KGa. It is deduced that TiO2 nanoparticles led to enhanced CO₂ capture efficiency of over 26.9 % and enhancement in KGa from 7.5%–96.1% for MEA based TiO2 suspension in comparison with MEA solution without nanoparticles. Therefore, TiO2 nanoparticles can augment the mass transfer coefficient and intensify the CO₂ absorption, even in a high-efficiency equipment like a high gravity RPB.

Droplet evaporation on a structured surface: The role of near wall vortexes in heat and mass transfer

Experimental studies on the evaporation of a drop located on a horizontal hot wall with cavities of different diameters of 0.5–2.5 mm were carried out. The wall temperature Tw was constant (74 °C and 83 °C). The evaporation behavior on a structured surface was compared with that on a smooth wall. Instantaneous velocity profiles have been obtained over a single cavity and in the vicinity of several cavities using the Micro Particle Image Velocity method (Micro PIV). It has been established that a hotter liquid is periodically ejected from the cavity, which increases convection inside the drop. The strongest intensification of mass transfer is specific for the largest cavities with a diameter of 2.5 mm. The behavior of the droplet evaporation on a smooth wall coincides with that on a structured surface with a cavity diameter of 0.5 mm. Until now, there have been no data that would link the convection in the drop with the vortexes in the cavity at non-isothermal evaporation and at high heat fluxes. The strongest influence of cavities is manifested in the initial period of evaporation, when a cold drop is placed on a hot wall. Over time, the evaporation rate on a structured wall approaches evaporation on a smooth (unstructured) surface. The article considers the influence of several key factors on the convection in a drop.

P.713 Enantiomers of deschloroketamine, a novel ketamine analogue, inhibit dopamine transporter (DAT) expressed in rat striatum

Implementation of resource-saving technologies can be based on improving the qualitative characteristics of heat and mass transfer equipment, which is widely used in power engineering, chemical, petrochemical, gas and food industries.One of the most effective ways of interaction between the coolant and the working medium is the direct contact of a gravitationally flowing liquid film and a gas. A promising method for passive intensification of heat and mass transfer between the liquid film and gas is the use of contact surfaces with regular roughness, with capillary-porous or mesh coating of channel walls.The launch and emergency stop of the heat and mass transfer device may generate a transition in the cooling mode of liquid from forced to natural convection. This leads to a change in the conditions of heat and mass transfer, and, consequently, to a change in the parameters of the coolant at the output of the device. In this case, using the dependences obtained for forced convection in the channel leads to a significant error in determining the parameters of the heat carrier. Therefore, in order to design and manufacture heat-mass-transfer units of contact type, one would need the information on the patterns of heat and mass transfer under different operating conditions.An important condition for ensuring the efficiency of contact-type devices is to know the features of the interaction between the liquid and gas mediums. The development of boundary layers in the film and gas leads to the need to allocate the initial thermal region and the stabilized heat and mass transfer region. These factors are not taken into account in the engineering calculation methods that exist today.

Determining experimental applicability limits of Spalart-Almares turbulent model and Reynolds stresses transfer model at mass transfer intensification in rotary-divergent controlled flows

This problem can arise in mechanics, chemistry and catalysis in the mass transfer intensification. The mass transfer characteristics were experimentally analyzed in a controlled rotary-divergent flow. The laser Doppler anemometer was used for turbulent mass transfer diagnostics. The experimental investigation was used to verify the numerical calculations. The numerical simulation has shown the presence of a near-wall jet after a rotary device and the reverse flow zones formation. The model of Reynolds stress transfer adequately describes the flow in range of flow rates from 50 to 250 n.m3/h. The Spallart-Almares turbulence model fails to adequately describe the flow at all flow rates.

Investigation of applicability area for turbulence models in the problems of mass transfer intensification by the control of a rotary divergent flow

The fundamental scientific problem of this kind arises in mechanics, chemistry and catalysis in the intensification of mass transfer. The turbulent mass transfer characteristics were analyzed experimentally in a controlled rotational-divergent flow. The laser Doppler anemometry was used for turbulent mass transfer diagnostic. The verification of numerical calculations by computational hydrodynamics has been carried out according to the results of experimental studies. Calculation of turbulent kinematic is build on solving of a system of continuity and the Navier-Stokes equations. The fluid is incompressible and isothermal. For averaged equations closure, semi-empirical turbulence models were used: the k-ε model of turbulence and the Reynolds stresses transfer model. The calculation has showed the existanceof a near-wall jet after a rotating device and the generation of reverse flow zones. Comparison with experimental data has shown that all models of turbulence adequately model the rotational-divergent flow only until the formation of flow gaps and the formation of reverse flow zones. The discrepancy with the experiment occurs while controlling the flow to equalize the velocity profiles.

Oil displacement by aqueous solutions of surfactants at various temperatures

To generalize the experimental data on the displacement of oil by aqueous solutions of surface-active substances (surfactants) at temperatures of 40, 60, 80 °C, we studied the influence of an additional parameter of the ratio of the work of adhesion during the displacement of oil by water to oil adhesion during the displacement of an aqueous solution of surfactant W = Ww/W. This parameter characterizes the intensity of mass transfer of oil particles from the surface of the rock using surfactants at different temperatures. The parameter W in combination with the capillary number Ca characterizes the value of residual oil saturation in oil reservoirs. A criterion equation is obtained that allows one to calculate the displacement coefficient from two dimensionless parameters: the capillary number and the relative work of oil adhesion.

Passage of a Taylor Bubble through a Stratified Liquid–Liquid Interface

The bypass of an air bubble through a liquid–liquid interface may produce rich fluidic physics. Air injection is a passive technique to mix the contents of the two separated fluids and provides an effective heat and mass transfer intensification by increasing the interfacial area between them. Entrainment of heavier fluid into the lighter fluid at atmospheric and isothermal conditions has been simulated by using the VOF (volume of fluid) technique mimicking a Taylor bubble bypass through a horizontal liquid–liquid interface of water and polydimethylsiloxane (PDMS) solution. The migration of a Taylor bubble across the interface is completed through five different stages, namely, approach, encapsulation, de-encapsulation, entrainment, and detrainment. The bubble kinematics, entrained water volume, microdroplets formation, and film thinning characteristics have been studied in detail. The marginal pinch-off mechanism for the rupturing of the entrapped water film has been observed due to the presence of the s...

Mathematical modelling of turbulent gas flow with particles based on eulerian approach

In Eulerian variables the mathematical model for calculating the hydrodynamic and thermal parameters of the dispersed mixture are presented. The mathematical model is based on the use of Eulerian description of mass conservation, the amount of motion for liquid and solid, recorded in the framework of the theory of interacting continuums. The turbulent characteristics of the gas are calculated using a modified transport model of the Reynolds stress tensor components, taking into account the presence of solid phase in the medium. The model allows to investigate the effect of non-isotropy of turbulent fluctuations of particle velocities, the ratio of the thermal properties of the particle material and the carrier gas on the intensity of momentum, heat and mass transfer in the dispersed phase.

Evaluation of Lipophilic Properties of Thermoplastic Granule in Formulation of Sustained Release Matrix in Solid Dosage Forms

This study was aimed at developing a new, technically simple method for the preparation of a once-daily sustained release matrix formulations, which would enable reproducible release of the active ingredient. Thermoplastic granulation is a new technique in pharmaceutical formulation. Coated particles of an active pharmaceutical ingredient (API) in sustained release matrix are prepared by thermoplastic granulation technique via heating (50 – 75°C) in fluid-bed dryer (FBD) granulator. The FBD creates ideal conditions for the most intense heat and mass transfer by spraying melted liquids onto the granular API. A variety of innovative processes such as granulation, agglomeration, coating and microencapsulation can be realized. Melted mixture of cetyl alcohol, glyceryl monostearate, and polyethylene glycol 4000 (PEG 4000) was used for fluid-bed coating. The present article deals with assessing the influence of rheological properties and hydrophile-lipophile balance (HLB) parameter of thermoplastic granules on the mechanism of drug delivery from sustained release matrix in solid dosage forms. The drug release kinetics model is affected by rheology, HLB of cetyl alcohol, and physicochemical properties of API granules.