Liquid-solid Mass Transfer Research Articles

Hydrogenation process intensification of 2-nitro-4-acetylamino anisole by HiGee technology

The catalytic hydrogenation of 2-nitro-4-acetylamino anisole (NMA) is the main path to synthesize 2-amino-4-acetylamino anisole (AMA), belonging to a typical gas-liquid-solid system. However, the small mass transfer rate of traditional hydrogenation reactor can't match its intrinsic fast reaction rate, resulting in the low hydrogenation efficiency. In this work, a rotating packed bed (RPB) reactor with excellent mass transfer performance was applied for the hydrogenation process intensification of NMA. The characterization analysis of the commercial Raney-Ni catalyst shows that the liquid-solid mass transfer resistance during the reaction process can be ignored, and improving the gas-liquid mass transfer rate is the key to improve the macroscopic reaction rate. The effects of operating conditions (solvent, rotational speed, hydrogen pressure, temperature, and catalyst dosage) on NMA conversion and AMA selectivity were investigated. A macro-kinetic equation of NMA catalytic hydrogenation in the RPB reactor was proposed. Under optimized conditions, the NMA was completely converted in the RPB reactor within 30 min, while it took 4 h in the stirred tank reactor. The overall reaction efficiency of RPB reactor was increased by 87.5 % in comparison with STR. This study provides practical guidance for the industrial application of RPB reactor for gas-liquid-solid hydrogenation.

Investigation on solid-liquid mass transfer and particle suspension of jet-flow high shear mixers

The jet-flow high shear mixer exhibits foreseeable advantages in intensifying diffusion-controlled solid-liquid reactions by its high-frequency mechanical impact. This study systematically investigated the influence of operational and structural parameters on solid-liquid mass transfer performance in JF-HSM. Combining experimental and simulation methods, suspension effect of solid particles in JF-HSM were assessed, and flow characteristics of particle two-phase flows were also analyzed. The results indicated that Njs was significantly influenced by rotor blade angle and stator bottom opening diameter, which increased by 1.77 and 1.47 times, respectively. The stator off-bottom clearance had a pronounced effect on kSLaSL, which increased by 90%. Furthermore, altering stator side opening ratio had minimal impact on both kSLaSL and Njs. Interestingly, acid concentration substantially affected kSLaSL, resulting in a maximum decrease of 24%, whereas Njs changed by only 3%. Correlations for kSL and Njs were established, providing theoretical guidance for applying and scaling JF-HSM in solid-liquid operations.

Mass and heat transfer behavior of a bubble column fitted with horizontal spiral tubes in bubbly-flow regime

Slurry bubble columns are commonly used for gas-liquid-solid diffusion-controlled reactions. However, they have some shortcomings, such as the high cost of separating the final product from the catalyst particles. This study proposes the use of spiral tubes as catalyst support to address these shortcomings. The liquid-solid mass transfer behavior of spiral tubes under different conditions of gas superficial velocity, spiral tube diameter, and pitch was studied using the electrochemical technique. The mass transfer coefficient was found to increase with increasing superficial gas velocity but decrease with increasing tube diameter and pitch. The data were correlated by a dimensionless equation suitable for the design and scale-up of the reactor. In addition to serving as catalyst support, the internal surface of the spiral tube can be used as a supplementary built-in cooler in conjunction with a cooling jacket for exothermic reactions. This is beneficial for catalytic reactions and biochemical reactions, which are prone to catalyst deactivation and thermal degradation, respectively. A study of the mass transfer behavior of a bubble column fitted with multi-spiral tubes revealed a deviation from the single spiral tube behavior by an amount ranging from 10% to 20%, depending on the operating conditions. Calculation of the ratio between the volumetric mass transfer coefficient and the specific energy consumption (performance indicator for the reactor under different conditions) revealed that the reactor has a high energy utilization efficiency.

Heat and mass transfer induced by alternating current during desorption of PAHs from soil using electrical resistance heating.

The transfer of heat and contaminants by alternating current (AC) and the removal mechanism of polycyclic aromatic hydrocarbons (PAHs) in electrical resistance heating (ERH) need further study. The main factors affecting heat transfer and water evaporation in the ERH experiment were studied, and the desorption efficiency, temporal and spatial distribution and kinetic behavior under various conditions were analyzed. The results suggested that moisture content was a necessary condition to ensure effective heating of soil, and soil moisture content above 30% was recommended. Higher voltage intensity and/or ion concentration meant stronger input power, resulting in the rapider heating process and the shorter the boiling time. At a low desorption temperature (about 100°C), the Phe desorption mainly depended on the volatilization of surface Phe and the co-boiling of Phe-water. In ERH, the participation of AC would accelerate the diffusion of pollutants from the internal pores of soil particles and their redistribution with water phase, thus improving the Phe removed by co-boiling. It was noteworthy that AC just greatly promoted solid-liquid mass transfer, but it hardly promoted desorption directly, and the removal still depended on Phe-water co-boiling. The Phe desorption efficiency could be significantly improved from 14.0~18.4% to 59.6~70.8% under the combined action of current strengthening Phe diffusion and co-boiling. Thermogravimetric and product analysis confirmed that no new organic matter was generated, but only Phe entered the gas phase through phase change.

Intensification of the rate of heat and mass transfer at the wall of a stirred tank reactor by integrating a helical coil turbulence promoter with the tank wall

ABSTRACT The influence of a helical coil turbulence promoter on liquid-solid mass transfer rates in a stirred tank was investigated using a technique that involved measuring the rate of diffusion-controlled copper dissolution in acidified dichromate. The study examined the effects of helical coil tube diameter (d), helical coil pitch (p), impeller rotation speed, impeller geometry (axial and radial), the presence of baffles, and solution physical properties. The presence of the helical coil near the reactor wall significantly enhanced mass transfer rates, with a factor ranging from 1.01 to 2.48. This improvement was accompanied by a corresponding increase in the volumetric mass transfer coefficient (kA), ranging from 2.68 to 4.55, depending on operating conditions. Further analysis revealed that the average mass transfer coefficient increased with decreasing coil tube diameter, while coil pitch had a minimal impact. Additionally, radial flow turbines demonstrated superior mass transfer performance compared to axial flow turbines. The presence of baffles also promoted higher mass transfer rates compared to unbaffled reactors. The experimental data were successfully correlated using dimensionless correlations, emphasizing the significance of these correlations in scaleup and design optimization of catalytic stirred tank reactors with efficient cooling systems.

Novel Correlation for the Solid–Liquid Mass Transfer Coefficient in Stirred Tanks Developed by Interpreting Machine Learning Models Trained on Literature Data

Novel Correlation for the Solid–Liquid Mass Transfer Coefficient in Stirred Tanks Developed by Interpreting Machine Learning Models Trained on Literature Data

Turbulent flow-driven liquid-solid mass transfer in serpentine tube heat exchanger/reactors: applications and implications

ABSTRACT This study examines liquid-solid mass and heat transfer rates in serpentine tube heat exchangers/reactors under turbulent flow using the copper dissolution technique. Key factors include solution flow rate, properties, tube diameter, U-bend curvature, and drag-reducing polymers. An empirical correlation predicts mass transfer coefficients, which are 4.12–5.36 times higher than straight tubes. Serpentine tubes show potential for economically viable diffusion-controlled reactions. Drag-reducing polymer (Polyox WSR-301) reduces corrosion rates by up to 23.3%. The study highlights serpentine tubes’ applicability in catalytic continuous reactors and membrane processes, emphasizing their significance in heat exchanger design and corrosion allowance prediction.

Quantifying Liquid-Solid Mass Transfer in a Trickle Bed Using {T}_{2}-{T}_{2} Relaxation Exchange NMR

Measurement of the liquid-solid mass transfer coefficient within a trickle bed (i.e. gas-liquid flow within a packed bed) of porous silica pellets is achieved through the use of {T}_{2}-{T}_{2} relaxation exchange nuclear magnetic resonance (NMR). Compared to many conventional measurement techniques, the NMR method enables measurement of mass transport using pellets of real commercial interest. Mass transfer coefficients measured using the NMR technique over a range of liquid Reynolds number, 0.2 le R{e}_{mathrm{L}}le 1.4, are compared to a number of literature correlations, with values measured using the NMR method falling within the range predicted by the correlations. The results demonstrate the importance of considering both the flow conditions and the type of pellets used to develop mass transport correlations in trickle beds. This novel NMR application may be utilized in the future to screen catalyst pellets in trickle beds for optimal mass transport properties.

Sustainable extraction of rice bran Oil: Assessing renewable solvents, kinetics, and thermodynamics

Rice bran (RB) oil extraction was performed by applying renewable solvents like ethanol and ethyl acetate. To assess the interaction of these solvents with the oil, the UNIFAC model was chosen to determine the infinite dilution activity coefficient. Soxhlet extraction was utilized to determine the maximum possible yield. The adequacy of the experimental data to mass transfer kinetic and thermodynamic models was investigated with response surface methodology. By the theoretical adjustment, statistical parameters (R²adj of 0.9398 for ethanol and 0.8525 for ethyl acetate) showed that the temperature and solvent/RB ratio have a notable influence on oil extraction. The experimental data agreed with the kinetic model based on solid-liquid mass transfer. The thermodynamic study showed that both solvents have endothermic, spontaneous, and irreversible processes. Interestingly, ethyl acetate had higher extraction yields at the beginning and reached its highest yield in a shorter time interval due to better compatibility with oily compounds present in rice bran and its lower viscosity.

Experimental study on the addition of pulsating flow to enhance liquid-solid mass transfer in the circulating fluidized bed

The addition of pulsating flow in the conventional liquid-solid circulating fluidized bed (CLSCFB) to enhance liquid-solid mass transfer efficiency has been proposed. A pulsating continuous liquid-solid circulating fluidized bed (PCLSCFB) experimental system was designed and constructed. The liquid-solid mass transfer coefficient (kSL) in the PCLSCFB was measured by the experimental method of dissolving the insoluble benzoic acid particles. The effects of superficial liquid velocity, superficial solids velocity and pulsation property on the liquid-solid mass transfer coefficient (kSL) in the PCLSCFB were thus determined. It was concluded that the liquid-solid mass transfer coefficient (kSL) increases with the increasing pulsation amplitude and frequency in the experimental range. The addition of pulsating flow significantly strengthens the liquid-solid interphase transfer efficiency in comparison with the CLSCFB. The correlation of the mass transfer coefficient (kSL) for the PCLSCFB has been proposed based on experimental data and main parameters.

Confined water–encapsulated activated carbon for capturing short-chain perfluoroalkyl and polyfluoroalkyl substances from drinking water

The global ecological crisis of perfluoroalkyl and polyfluoroalkyl substances (PFASs) in drinking water has gradually shifted from long-chain to short-chain PFASs; however, the widespread established PFAS adsorption technology cannot cope with the impact of such hydrophilic pollutants given the inherent defects of solid-liquid mass transfer. Herein, we describe a reagent-free and low-cost strategy to reduce the energy state of short-chain PFASs in hydrophobic nanopores by employing an in situ constructed confined water structure in activated carbon (AC). Through direct (driving force) and indirect (assisted slip) effects, the confined water introduced a dual-drive mode in the confined water-encapsulated activated carbon (CW-AC) and completely eliminated the mass transfer barrier (3.27 to 5.66 kcal/mol), which caused the CW-AC to exhibit the highest adsorption capacity for various short-chain PFASs (C-F number: 3-6) among parent AC and other adsorbents reported. Meanwhile, benefiting from the chain length- and functional group-dependent confined water-binding pattern, the affinity of the CW-AC surpassed the traditional hydrophobicity dominance and shifted toward hydrophilic short-chain PFASs that easily escaped treatment. Importantly, the ability of CW-AC functionality to directly transfer to existing adsorption devices was verified, which could treat 21,000 bed volumes of environment-related high-load (~350 ng/L short-chain PFAS each) real drinking water to below the World Health Organization's standard. Overall, our results provide a green and cost-effective in situ upgrade scheme for existing adsorption devices to address the short-chain PFAS crisis.

Modelling particle dissolution in stirred vessels

Particle dissolution in stirred vessels is a unit operation commonly encountered in several production sectors, such as the mineral, pharma and chemical industries. It is commonly conducted batch-wise under time-dependent conditions, a circumstance that complicates model set-up. This paper presents a set of models for simulating batch dissolution of polydisperse particles in stirred vessels. These models cover all scenarios of particle batch dissolution, regardless of whether the initial particle quantity exceeds or falls short of achieving solution saturation. Consequently, they address cases where particles are either completely dissolved or remain partially undissolved. The models also account for both single-sized and multi-sized particles. Convenient model simplifications are also provided for the cases of final solute concentration much smaller than saturation (low final concentration models). All models are successfully experimentally validated. The single-size large final concentration model is employed to set up experimental runs that, apart from their use in predictive simulations, may be employed for simultaneously measuring mass transfer coefficient and interfacial solute concentration using suitable experimental runs. The ability to measure interfacial solute concentration is also exploited for assessing whether it coincides, or not, with the solute saturation concentration, a common assumption when dealing with solid-liquid mass transfer, which in the present case is found to hold true. The simpler single-size low-final-concentration model is very convenient for measuring the mass transfer coefficient alone. Finally, the multi-size model is utilised to evaluate the sensitivity of the estimated mass transfer coefficient in the single-size model to the particle size range employed during experimental measurements of mass transfer coefficients.

Influencing factors of bioaugmentation treatment of PAH-contaminated soils in slurry bioreactors

Polycyclic aromatic hydrocarbons (PAHs) are a group of contaminants with low bioavailability and biodegradability. As a result, removing PAHs from contaminated soils is often inefficient. In this study, soils spiked with fluoranthene and pyrene were inoculated with Aeromonas sp. BCP-3, a newly isolated strain from coke-plant sludge, and treated in slurry bioreactors. The removal of PAHs was significantly affected by aeration rate, slurry water-soil mass ratio, stirring rate, temperature, and the concentration of Tween-80. Such effects were attributed to changes in BCP-3 growth, PAHs solid-liquid mass transfer, and slurry particle size. Notably, under optimal conditions (i.e., aeration rate of 1.5 L/min, temperature of 30 °C, stirring rate of 200 rpm, water-soil mass ratio of 1.5:1, and Tween-80 concentration of 1.3 %), 96.3 % and 97.2 % of initially spiked fluoranthene and pyrene were removed within 12 days, respectively. A PAH-contaminated soil was collected from a local coking plant and treated under the same conditions, except for the Tween-80 concentration. For the real soil, the Tween-80 concentration was 4 % to ensure a significant proportion of PAHs released into the liquid phase. Twenty-one days after inoculation of BCP-3, the removal efficiencies of low molecular weight PAHs and high molecular weight PAHs were 82.2 % and 51.8 %, respectively. The removal efficiencies of PAHs were significantly higher than the slurry without BCP-3 or HgCl2-sterilized slurry. BCP-3 improved the bioavailability and biodegradability of PAHs, resulting in effective PAH removal in slurry bioreactors. Overall, successful bioaugmentation was achieved with the addition of Tween-80 and the optimization of operating conditions.

Reaction of Carbon Dioxide Gas Absorption with Suspension of Calcium Hydroxide in Slurry Reactor

Chemical phenomena involving three phases (solid, liquid, and gas) are often found in the industry. Carbonate (CaCO3) is widely used in industries as a powder-making material in the cosmetic industry, a pigment in the paint industry, and filler in the paper and rubber industry. This research aim to study the ordering process carbonate deposits (CaCO3) from the absorption process of CO2 gas with Ca(OH)2 suspension. The absorption reaction of CO2 gas with Ca(OH)2 suspension was carried out in a stirred slurry tank reactor. Initially, the reactor containing water was heated to a certain temperature, then Ca(OH)2 was added to the reactor. Furthermore, CO2 gas with a certain flow rate and temperature (according to the reactor temperature) is flown with the help of a gas distributor. Samples were taken every 1 min until the concentration of Ca(OH)2 could not be detected (completely reacted). The variables in this study were: stirrer rotation speed (5.66711.067 rps), CO2 gas flow rate (34.0127–60.5503 c/s), and temperature (30–50°C). The mass transfer coefficient and the reaction rate coefficient were determined by minimizing Sum of Squares of Errors (SSE). This experimental process follows a dynamic regime. A dimensionless number relationship for the gas-liquid mass transfer for the value range is Re1 = 18928.76-38217.20, Sh = 0.07928 Reg0.4383 Rel0.4399 Sc0.6415 with an error of 5.19%. The dimensionless number relationship for solid-liquid mass transfer is Sh = 0.0001179 Reg0.4674 Rel0.5403 Sc1.444 with an error of 7.31%. The relationship between the reaction rate constant and the temperature in the 30-50 °C range can be approximated by the Arrhenius equation, namely kr = 1771000 e-2321.4/T cm3/mgmol/s with an error of 3.63%. Doi: 10.28991/ESJ-2023-07-02-02 Full Text: PDF

Liquid Fluidization of Short Hollow Cylinders

We perform numerical simulations on fluidized dense suspensions of solid spheres, solid cylinders, and hollow cylinders in a Newtonian liquid. The simulations are three-dimensional and time-dependent and aim to resolve the flow around and─for the hollow particles─inside individual particles. We use a lattice-Boltzmann scheme that includes an immersed boundary approach for imposing no-slip at solid surfaces. The overall solids volume fraction is 0.5 for the solid particles and 0.375 for hollow cylinders. The latter have a length over outer diameter aspect ratio in the range of 0.56–1.58, while the ratio of outer to inner diameter is 2. Archimedes numbers of the order 103–104 are such that we expect inhomogeneous fluidization with wave-type voidage instabilities. We have a particular interest in the flow through the inner diameter of the hollow cylinders and the extent to which it could contribute to liquid–solid mass transfer.

CO2 sequestration by direct mineral carbonation of municipal solid waste incinerator fly ash in ammonium salt solution: Performance evaluation and reaction kinetics

In this study, we investigated CO2 mineral sequestration by municipal solid waste incineration fly ash (MSWI-FA) in both pure water and ammonium salt solutions [NH4Cl, (NH4)2SO4 and CH3COONH4]. The introduction of NH4+ significantly promoted the solid–liquid mass transfer of the active calcium on the MSWI-FA particles and the generation of free ammonia in the solution, which enhanced the carbonation kinetics and crystallization of the calcium carbonate product. Changes to the mineralogy, morphology, and surface properties of the MSWI-FA particles before and after carbonation confirmed the reaction mechanism. A novel kinetic model based on the two-film theory was developed to evaluate the mass transfer and chemical reaction of heterogeneous carbonation in both pure water and ammonium salt solutions. To optimize the carbonation rate and efficiency, the complex effects of various operating parameters on the CO2 sequestration characteristics were systematically investigated. Maximum carbonation kinetics was achieved at 60 °C, an ammonium salt concentration of 1.0 mol/L, and a gas flow rate of 1.0 L/min, resulting in a carbonation efficiency and CO2 sequestration capacity of 78.49 % and 0.236 g CO2/g MSWI-FA, respectively. A comparison of the present results with those of other studies suggests that direct aqueous carbonation in ammonium salt solutions is feasible owing to its higher carbonation kinetics and CO2 sequestration capacity.

Preparation of Mn-FeOX/ZSM-5 by high-gravity method for heterogeneous catalytic ozonation of nitrobenzene

Mn-FeOX/ZSM-5 is a good catalyst for wastewater treatment, but the conventional methods for preparing Mn-FeOX/ZSM-5 have the problems of non-uniform dispersion of active components and long preparation time. As the liquid-solid mass transfer process could be effectively increased in a high-gravity field, Mn-FeOX/ZSM-5 was prepared by high-gravity method in this study, and its properties were characterized by XRD, FTIR and SEM. The stability of Mn-FeOX/ZSM-5 and the loss of active components were investigated, and the mechanism of Mn-FeOX/ZSM-5 catalyzed the ozonation of nitrobenzene (NB) was also discussed. The results show that the specific surface area of Mn-FeOX/ZSM-5-h is 292.103 m2/g and the active components are well dispersed. Mn-FeOX/ZSM-5-h has the best catalytic activity under the conditions of precursor solution concentration = 0.3 mol/L, liquid flow rate = 60 L/h, and high gravity factor β = 30, and the removal efficiency of TOC reaches 87.5% within 25 min. The catalyst has good stability and only 1.10% of Mn and 0.63% of Fe are lost on average after 5 cycles. However, the removal rate of NB is significantly reduced with the addition of tert-butyl alcohol (TBA), implying that ·OH plays a dominant role in catalytic ozonation of NB by Mn-FeOX/ZSM-5. The electron paramagnetic resonance results confirm that ·OH is produced in the degradation process. In conclusion, Mn-FeOX/ZSM-5-h prepared by high-gravity method is a good catalyst for catalytic ozonation of NB because of its high catalytic activity and stability.

Experimental Solid–Liquid Mass Transfer around Free-Moving Particles in an Air-Lift Membrane Bioreactor with Optical Techniques

This article focuses on the study of the mass transfer involved in the application of a bacterial antifouling technique for membrane bioreactors (MBR), via the addition of solid media. These alginate objects can contain a biological system capable of producing an enzyme that degrades the signal molecules responsible for membrane fouling. The objective of this article is to quantify the mass transfer by distinguishing two main types: the transfer from the liquid to the solid media and the transfer from solid media to the liquid phase. For this purpose, a model molecule was chosen, and experiments were specifically developed with an optical device to track the concentration of the dye in the liquid phase, considering three different shapes for the particles (beads, hollow cylinders, and flat sheets). The experiments were first performed in jar tests and then in a lab-scale reactor. The results of this study revealed that the total amount of dye transferred into the sheets was greater than that transferred into the cylinders or the beads, which was attributed to the sheets having a larger exchange area for the same volume. When the dyed media were implemented in the MBR (loading rate of solid media: 0.45% v/v—no biomass), the global transfer coefficient from the sheets to the liquid was found to be greater than for the other shapes, indicating a faster transfer phenomenon. The effect of aeration in the MBR was investigated and an optimal air flowrate for fostering the transfer was found, based on the highest transfer coefficient that was obtained. This study provided key information about mass transfer in MBRs and how it is affected by the particle shapes and the MBR operating conditions.

Mass and Heat Transfer at the Bottom of Cylindrical Unbaffled Stirred Tank Reactor and Possible Applications

Liquid-solid mass and heat (by analogy) transfer at the bottom of a cylindrical stirred vessel were studied by using the well-known electrochemical technique. Variables studied included the impeller geometry and its rotational speed. Results revealed that the radial flow impeller is preferable over the axial flow one in terms of mass transfer enhancement, additionally, increasing the impeller rotational speed led to an increase in the mass transfer coefficient. Results were correlated by dimensionless equations. Application of these equations in the design and operation of an improved catalytic biochemical reactor suitable for conducting diffusion-controlled immobilized cell (or enzyme) reactions was highlighted. These equations can serve in predicting the corrosion rate and corrosion allowance required to calculate the bottom thickness of the agitated vessel in its design stage. Furthermore, these equations can be used in estimating the heat lost from the tank bottom, accordingly, design an effective cooling jacket surrounding the agitated vessel bottom in case of exothermic biochemical reactions to avoid thermal degradation of the biomass.

A readily available and efficient Pt/P25 (TiO2) catalyst for glycerol selective oxidation

AbstractIn this work, a commercial P25 (TiO2) with phase junctions between (101) and (110) faces supported Pt catalyst was prepared for glycerol selective oxidation, giving a decent 76.8% glyceric acid (GLYA) yield, and good stability. The kinetic experiments calculated apparent activation energy, turnover frequency (TOF), and reaction rates, demonstrating Pt/P25 could facilitate glyceraldehyde (GLYAD) formation and inhibit GLYA over‐oxidation. Series of structural techniques confirmed the 101/110 junctions in P25 contributed electronic effect on Pt through metal‐support interface, which improved the oxygen activation ability and optimized the GLYAD/GLYA adsorption modes. Furthermore, progressive scale‐up reactions were tested and the mass transfer limitations under different conditions were thoroughly studied. The obtained mass transfer factors suggested the gas–liquid and liquid–solid mass transfer were severely limited. Finally, through optimizing the conditions, Pt/P25 catalyst achieved 75.8% GLYA yield at 300 ml‐scale reaction, realizing equivalent magnification with the 5 ml‐scale experiment.