Effective Interfacial Area Research Articles

Novel rate-based modeling and mass transfer performance of CO2 absorption in rotating spiral contactor

For the process of CO2 absorption, existing gas-liquid contactors suffer from low mass transfer performance and low gas-liquid ratios. In this study, a rotating spiral contactor was developed to overcome these drawbacks and a novel rate-based model was developed to predict the CO2 absorption performance. The effective interfacial area (ae), overall volumetric mass transfer coefficient (KGae) and CO2 absorption efficiency (η) were investigated. The results showed that the ae was 913–1125 m2/m3 superior to the conventional contactor. In the range of gas–liquid ratio of 200–1800, the KGae and η were 1.4–10.1 kmol.m-3.h-1.kPa-1 and 40.5–99.6 %, respectively. The rate-based model predicted the KGae and η with the AARD of 6.71 % and 1.90 %, respectively. Also, it has better robustness even in highly nonlinear temperature and composition distributions. This study provides a potential contactor and a new modeling tool for CO2 capture and other gas-liquid separation.

Exploring MOF-Derived CuO/rGO Heterostructures for Highly Efficient Room Temperature CO2 Sensors.

In response to the urgent need for advanced climate change mitigation tools, this study introduces an innovative CO2 gas sensor based on p-p-type heterostructures designed for effective operation at room temperature. This sensor represents a significant step forward, utilizing the synergistic effects of p-p heterojunctions to enhance the effective interfacial area, thereby improving sensitivity. The incorporation of CuO nanoparticles and rGO sheets also optimizes gas transport channels, enhancing the sensor's performance. Our CuO/rGO heterostructures, with 5 wt % rGO, have shown a notable maximum response of 39.6-500 ppm of CO2 at 25 °C, and a low detection limit of 2 ppm, indicating their potential as high-performance, room-temperature CO2 sensors. The prepared sensor demonstrates long-term stability, maintaining 98% of its initial performance over a 30-day period when tested at 1-day intervals. Additionally, the sensor remains stable under conditions of over 40% relative humidity. Furthermore, a first-principles study provides insights into the interaction mechanisms with CO2 molecules, enhancing our understanding of the sensor's operation. This research contributes to the development of CO2 monitoring solutions, offering a practical and cost-effective approach to environmental monitoring in the context of global climate change efforts.

Evaluation of Effective Interfacial Area in a Rotating Packed Bed Equipped with Dual Gas Inlets

This study investigates the effective interfacial area in a novel rotating packed bed (RPB) equipped with dual gas inlets instead of the conventional single-gas-inlet RPB. The aim is to enhance the mass transfer efficiency of gas-liquid contacting processes in RPBs by increasing the number of gas inlets to improve the spread of gas supply into the packing. The RPB is a promising gas-liquid contactor configuration known for its intensified mass transfer characteristics. However, the impact of additional gas inlets on the effective interfacial area of the packing remains unexplored. An experimental method assessed the interfacial area under varying operational conditions which include a liquid flow rate of 0.30-0.60 m3/h, a gas flow rate of 100-300 Nm3/h, and a rotation speed of 600-1000 rpm. At operating conditions covering the maximum rotation speed of 1400 rpm, gas flow and liquid flow rates of 300 Nm3/h and 0.60 m3/h respectively, the results showed that on average, 55 to 97% of the 2400m2/m3 specific packing area can be effectively utilized for gas-liquid mass transfer during separation operations using the RPB. Compared to results reported for single-gas-inlet RPBs using similar packings, the RPB with double gas inlet proved to provide higher utilization of the packing. By simply doubling the number of gas inlets, the findings provide valuable insights into optimizing RPB designs and operations which could enhance mass transfer efficiency for various chemical and environmental applications.

Flow behavior and size characteristics of microbubble swarm in a HiGee-aided fixed bed reactor with different packed structures

A HiGee-aided fixed bed reactor (HFBR) has great potential for catalytic hydrogenation with hydrogen microbubble swarm for gas–liquid mass transfer intensification. However, the flow behavior and size characteristics of microbubble swarm in the catalyst bed of HFBR still remain unclear. In this work, the flow characteristics of microbubble swarm in different packed structures of catalysts and catalyst supports had been fully analyzed by the high-speed photography and image processing technology. The optimal ratio of packing heights for the bottom of the catalyst supports was Φ13 mm: Φ6 mm: Φ3 mm = 3: 1: 1, while the top of the catalyst supports was packed with single catalyst support of Φ6 mm. Furthermore, a dimensionless correlation based on the experimental results had been developed to predict (d32)o/(d32)i with deviations within ±15 %. The effective interfacial area of HFBR was 0.6 ∼ 6.1 × 103 m2/m3 under the experimental conditions.

Hydrodynamics, mass transfer, and hydrogenation performance of a HiGee‐aided fixed bed reactor

AbstractMicrobubble shows great potential for hydrogenation reaction in fixed bed reactors (FBRs). However, the lack of understanding of the hydrodynamic behaviors of microbubble swarm in FBR limits the reactor design. In this work, a pilot‐scale HiGee‐aided fixed bed reactor (HFBR), including a HiGee microbubble generator (HMG) and a catalyst bed, has been developed and then applied for poly alpha olefin 4 (PAO 4) hydrogenation. An empirical correlation of Sauter mean diameter (d32) of microbubbles at the inlet and outlet of catalyst bed was established. The gas holdup (φb) of catalyst bed with HMG was 5–10 times higher than that without HMG. Based on d32 and φb, the effective interfacial area in HFBR was calculated as 2000–6000 m2/m3. Compared with static mixer‐aided fixed bed reactor, the aromatic content of PAO 4 hydrogenated in the HFBR was 56%–69% lower, which shows bright future for industrial application.

Research on carbon dioxide capture and mass transfer in hydro-jet cyclone

Steel smelting has a large amount of flue gas emissions and high carbon capture costs, making it one of the “heavy disaster areas” for carbon dioxide (CO2) emissions. This article develops a hydro-jet cyclone (HJC) by coupling the gas phase swirling flow field with the liquid phase jet flow field, and proposes a carbon capture technology for smelting flue gas. During the dispersion process of liquid phase microelements, there was simultaneous rotation and revolution of droplets, which enhances the gas–liquid mass transfer process. The surface renewal effect increases the effective specific interface area, and the interface oscillation effect was beneficial for reducing the mass transfer resistance on the liquid side. A model for the effective phase interface area (ae) of HJC was first proposed for different jet hole, with a maximum ae of 5358.95 m2·m−3.In the CO2-NaOH system, the absorption efficiency of CO2 was 88.9 %. This article supplements HJC's research on carbon capture and gas–liquid mass transfer by optimizing the size of the jet hole, which was beneficial for the development of efficient carbon capture equipment in the steel industry and further promotes the sustainable development of the steel industry.

Construction of Co3O4/SnO2 yolk-shell nanofibers for acetone gas detection

In this work, Co3O4/SnO2 heterojunctions were proposed and fabricated by single-nozzle electrospinning. Interestingly, novel yolk-shell nanofibers could be formed in a proper doped content of Co3O4. The gas sensing properties of sensors based on Co3O4/SnO2 yolk-shell nanofibers were evaluated, and a superior response of ∼216–100 ppm acetone at 350 °C was obtained. Additionally, Our sensors have an ultrafast response time of ∼0.62 s, demonstrating remarkable selectivity for acetone and excellent stability for both humidity and long-term use. These exceptional performances are attributed to the synergistic effect of nano-heterojunctions that enhance the effective interfacial area, as well as the unique yolk-shell structure of SnO2/Co3O4, which increases gas transport channels. Our results demonstrate that constructing Co3O4/SnO2 yolk-shell nanofibers is an effective strategy for achieving high-performance acetone gas detection.

Study on effective phase interfacial area at different injection angles of hydro-jet cyclone

In contrast to conventional tower-type mass transfer equipment, the hydro-jet cyclone exhibits superior mass transfer capabilities. This study presents a novel investigation into the effective phase interfacial area (ae) of the hydro-jet cyclones across five unique injection angles. The investigation employs a combination of CFD simulations and experimental analysis utilizing a CO2-NaOH system. The results indicate that the 45° upward incidence angle yields the most favorable flow field characteristics for efficient mass transfer when liquid–gas ratio ranges from 0.18 to 0.27. The ae values of the hydro-jet cyclones range from 1846 to 5358 m2·m−3, representing an approximate fivefold increase compared to the rotating packed tower. Empirical formulas for ae are proposed for both vertical incidence and upward 45° incidence angles. This significant enhancement in ae offers the advantage of reducing the equipment volume of the hydro-jet cyclone, leading to substantial cost savings in terms of investment and auxiliary devices.

Enhancing NOx removal in a high-gravity rotating packed bed with gaseous ClO2 oxidation-absorption: Kinetic, mass transfer, and cost analysis

The application of ClO2(g) for NO oxidation presents a promising approach to improving air pollution control technology. In this study, an integration of ClO2(g) with absorption using a high-gravity rotating packed bed (HiGee RPB) was proposed for NOx removal. The results showed that ClO2(g) has a comparable oxidation efficiency (close to 100%) to O3 in converting NO to NO2, while the dosage of ClO2(g) required was two times smaller than that of O3. The gas-phase oxidation kinetic analysis between ClO2(g)-NOx, using an ideal plug flow model, simulated the potential amount of NOx species produced in a short reaction distance in the pipeline. Furthermore, at higher gas-liquid ratios and in high-gravity fields, the effective mass transfer interfacial area for NO2 absorption was mainly controlled by the liquid film rather than droplet behavior, resulting in decreased absorption capacity. The empirical model for predicting the gas-side mass transfer coefficient confirmed that the interaction between mass transfer performance and chemical absorption was independent. Therefore, selecting the appropriate absorbent is a key factor in achieving high-loading NO2 concentrations after oxidation by ClO2(g). Another interesting finding is that balancing system energy consumption and the target treated NOx concentration played a critical role in enhancing the NOx absorption capacity. The cost analysis showed that substituting existing scrubbers with RPB processes could facilitate NOx absorption capacity (g-NOx/kWh) with cost-effectiveness. Overall, this study provides valuable insights into the development of effective and efficient NOx removal technologies, and future research in this area can build on these findings.

Mass transfer under distillation of positive, neutral, and negative system in the I.D. 0.3 m column packed with structured packing

The distillation of three binary test systems differing in the surface tension gradient along the column, namely: cyclohexane/n-heptane (negative), cyclohexane/toluene (neutral), n-hexane/cyclohexane (positive), has been performed under total reflux in the i.d. 0.3 m distillation column packed with MellapakPlus 452. Y structured packing. Although all constituents are C6 – C7 hydrocarbons with close physical properties in the gas phase, the resulting HETP differ by up to 20 %. Further analysis suggests that system negativity causes the approx. 30 % decrease of the effective interfacial area with respect to positive and neutral systems, which behave comparably. Indeed, observation of the distillation on the inclined plate in the IR spectra shows breakage of the negative system liquid films into rivulets, supporting the result.

Mass transfer during surfactant-enhanced DNAPL remediation: Pore-scale experiments and new correlation

Surfactant-enhanced solubilization has been proven successful to remediate aquifers contaminated with non-aqueous phase liquids (DNAPLs). Understanding mass transfer from DNAPLs to the surfactant solution is highly important for improving remediation efficiency. However, the pore-scale mechanisms underlying the effect of surfactants on mass transfer behaviors have not been fully understood. Here we use microfluidic experiments to investigate the fundamental physical processes and quantify the impacts of surfactants on mass transfer rate at the pore scale. We find that surfactants can induce droplet breakup behaviors due to the interfacial disparity of mass transfer strength, resulting in the subsequent micro-movement of daughter blobs due to capillary force. Through image-based measurements, we find a significant inhibition of the mass transfer rates by surfactants at concentrations above the critical micelle concentration, and the inhibition becomes more pronounced as the concentration increases, which can be explained by an increase in stagnant film thickness. But the total mass transfer flux is improved because of the enhanced driving force caused by the surfactant-enhanced concentration gradient. In light of the observed physical processes and the behavior of mass transfer inhibition, we finally develop a new empirical model that explicitly considers the effects of surfactant concentration, DNAPL distribution, effective interface area, and flow rate to predict the mass transfer rate. This work provides pore-scale underpinnings of the mass transfer behaviors and a new mass transfer model considering the effect of surfactants, which improves the understanding of interphase mass transfer processes under the action of surfactants in subsurface hydrological and engineering systems.

Gas-liquid flow regimes and effective interfacial area in a solid foam block stirred tank

Recently, a solid foam block (SFB) stirred tank has attracted wide attention owing to its excellent mass transfer efficiency. However, more fundamental information is needed to deepen the understanding of the strengthening mechanism and application of this novel stirrer. Therefore, in this work, the flow regimes and the effective interfacial area as the crucial information for the mass transfer process in the SFB stirred tank are investigated by high-speed imaging and the Danckwerts-plot technique. Four typical flow regimes are revealed in the SFB stirred tank, which corresponds to the three changes in the effective interfacial area from 30 to 1490 m − 1 when adjusting the operating conditions. Correlations are respectively developed with the deviation of ±10% and ±15% to distinguish the flow regimes and predict the effective interfacial area in SFB stirred tank. Compared with the Rushton stirred tank, the SFB stirred tank is able to generate two times effective interfacial areas at fixed power input, showing superior performance and the promising prospect in some certain multiphase application fields.

Effect of triblock copolymers on the lipase catalytic behavior at the interface of conventional O/W emulsions

The ‘interfacial quality’ is the key influencing factor for lipase activities at interfaces, and thus, interfacial engineering has become an effective strategy to modulate lipase catalysis. In the current research, the triblock copolymers poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) (PEO-PPO-PEO) were adopted to form conventional oil-in-water (O/W) emulsion systems. The results showed the different effects of PEO-PPO-PEO molecules on the spatial barriers, emulsion particle size, and ultimately interfacial adsorption properties of lipases. Since the molecular weight of Candida antarctica lipase B (CALB) is approximately half that of Candida rugosa lipase (CRL), it can more easily pass through the triblock copolymer adsorption layer, resulting in a higher adsorption ratio. The results confirmed that the catalytic efficiency of CALB at the emulsion interfaces was much lower than that of CRL due to its lack of a typical ‘lid’ structure. Both the effective amount of lipase molecules at the interfaces (controlled by the interfacial adsorption ratio) and the effective catalytic interface area (influenced by the specific surface area controlled by the average particle size of the O/W emulsion) impacted the catalytic activities of CRL. Na+ ions were found to have a certain inhibitory effect on the catalytic activity of CRL.

Effects of inclined state and rolling motion on gas–liquid effective interfacial area in a rotating packed bed

Confined space and floating environment present high challenges for gas–liquid separation and purification processes on offshore platforms. Rotating packed beds (RPBs) have shown great potential in onshore application, but its performance under offshore conditions remains unclear. This study first investigates the effective interfacial area (ae) within an RPB under inclined and rolling conditions by using the CO2 chemisorption method. The inclined state and rolling motion significantly affect ae, which is determined jointly by the secondary axial distribution and gas flow direction. The adverse effects occur at low rotational speed (N) due to the liquid collection driven by the gravity component, and increasing N was found to effectively against the collection and improve ae. Furthermore, ae under different motion periods and operating conditions were also investigated, and its relative rates of change and fluctuation can reach up to 17.4% and 10.7%, respectively. These results suggest that RPBs are somewhat resistant to marine conditions, providing the basis for offshore applications.

Hydrodynamics and mass transfer enhancement of gas–liquid flow in micropacked bed reactors: Effect of contact angle

AbstractPressure drop, residence time distribution, dispersive behavior, liquid holdup, and mass transfer performance of gas–liquid flow in micropacked bed reactors (μPBRs) with different contact angles (CA) of particles are studied. The value of pressure drop for three types of beads can be obtained: copper beads (CA = 88.1°) > stainless steel beads (CA = 70.2°) > glass beads (CA = 47.1°). The liquid axial dispersion coefficient is 1.58 × 10−6 to 1.07 × 10−5 m2/s for glass beads and copper beads, which is smaller than those of trickle bed reactors. The liquid holdup of 400 μm copper beads is larger than that of 400 μm glass beads. The ratio of effective interfacial area enhancement is evaluated up to 55% for big contact angle beads compared with the hydrophilic glass beads. In addition, correlations of pressure drop, liquid holdup, and effective interfacial area in μPBRs with different wettability beads are developed and predicted values are in agreement with the experimental data.

Interface Formation of Medium-Thick AA6061 Al/AZ31B Mg Dissimilar Submerged Friction Stir Welding Joints.

The medium-thick Al/Mg dissimilar friction stir welding (FSW) joint has serious groove and cavity defects due to uneven thermal distribution in the thickness direction. The submerged friction stir welding (SFSW) was employed to decrease the peak temperature of the joint and control the thermal gradient of the thickness direction, which were beneficial in suppressing the coarsening of the intermetallic compounds (IMCs) layer and improving the weld formation. According to the SEM results, the thickness value of the IMC layer in the nugget zone and shoulder affect zone decreased from 0.78 μm and 1.31 μm in FSW process to 0.59 μm and 1.21 μm in SFSW process at the same parameter, respectively. Compared with the FSW process, SFSW improves the thermal accumulation during the process, which inhibits the formation of the IMCs and facilitates the material flow to form a mechanical interlocking structure. This firm interface formation elevates the effective contact area of the whole joint interface and provides a strong connection between the dissimilar metals. Thus, the ultimate strength of the 6 mm thick Al/Mg dissimilar SFSW joints was enhanced to 171 MPa, equivalent to 71.3% of AZ31B Mg alloys strength.

Influences of asphaltene subfractions with different polarities on hydrate growth at water/oil interface

As a kind of typical natural surface-active substance, asphaltenes can not only lead to deposition and plugging accidents, but also affect the formation and slurry flow of hydrate during deep-sea oil and gas transportation process. This paper investigates the polarity effects of the asphaltene subfractions on the growth process of hydrate particles at oil–water interface. First of all, four asphaltene subfractions with different polarities were extracted by the solvent precipitation method. Then, the dynamic interfacial tension and dilational viscoelastic properties were measured to characterize the oil–water interfacial films adsorbed with the different asphaltene subfractions. Following that, the hydrate growth experiment was carried out using a self-designed atmospheric visualization unit. Specifically, the transformation process of a single droplet into a hydrate particle in oil phase containing asphaltenes was studied to determine the influence of asphaltene subfractions on hydrate growth. The change degree of particle morphology and the growth rate of hydrate shells were used as two analysis indexes. The results show that the change degree of particle morphology and the growth rate of hydrate shells were both affected by the dispersion state and interfacial adsorption amount of the asphaltene subfractions. Under the combined action of migration and surface covering, the asphaltene subfractions have different effects on hydrate growth process at various concentrations. At the concentration of 0.01 mg/g and 0.1 mg/g, a looser interfacial adsorption layer will result in a large effective interfacial area, i.e., a weaker mass transfer hindrance. At this time, the structural strength of the interfacial film is low. At the concentration of 0.2 mg/g, however, the transformation rate of the hydrate shells is accelerated owing to the trapped oil phase, so the structural strength of the interfacial film is enhanced. Therefore, with the increase of the asphaltene concentration, the hydrate particles are easier to maintain their original state.

Helical Packing Columns for Preventing Foam Formation: Experimental and Numerical Investigations

AbstractUnwanted foaming and liquid bridging inside structured packings have a negative effect on the pressure drop during thermal separation processes. A novel helical design of a packing column for preventing foaming is presented. The effective interfacial area is calculated by numerical simulations. Different designs are analyzed by varying geometrical parameters such as helix pitch, channel opening angle, and number of channels. Different F‐factor values and liquid loads are evaluated. Packings with larger helix pitch exhibited lower pressure drop and reduced effective interfacial area. Smaller channel opening angles increased the pressure drop and promoted unstable flow conditions. The novel packings show lower effective interfacial area than existing structured packings, but no foaming was observed in a wide range of operating conditions.

A Two‐Step Thermomechanical Process for Improving High‐Angle Grain Boundary Proportion and Achieving Delamination Toughening in Hot‐Rolled Steel with a Limited Slab‐to‐Plate Ratio

A Two‐Step Thermomechanical Process for Improving High‐Angle Grain Boundary Proportion and Achieving Delamination Toughening in Hot‐Rolled Steel with a Limited Slab‐to‐Plate Ratio

Novel electrode design for energy harvesting devices based on liquid–solid contact and enhancement of effective interface area

Electrical double layer (EDL) modulation in liquid–solid interfaces has been extensively studied as an easy and effective approach to harvest triboelectric energy from micromechanical wasted energy. Owing to the fluidity of liquids, the liquid–solid contact area in an EDL-based device, for example, a liquid droplet sandwiched between two substrates, can be modulated to a large extent by simply squeezing or releasing the two substrates. However, conventional EDL-based technology cannot fully exploit this advantage, and the relevant devices suffer from poor efficiency. Herein, we demonstrate a simple yet highly effective EDL-based energy harvesting device with a novel electrode design composed of a hydrophilic inner circular electrode and hydrophobic outer ring electrode allowing the best use of the liquid–solid interface, i.e., large modulation of the contact area. The contact area variations in the top and bottom substrates contribute in an opposite manner to the electric generation in a conventional device. However, the new electrodes are designed to ensure that the contact area variations in the two substrates contribute cooperatively to the energy generation. The new device increases the output power by approximately 30-fold compared to that of conventional devices. Moreover, the optimal design for higher power generation considering internal resistance is systematically investigated and theoretically verified. The feasibility of these devices is demonstrated by the instantaneous lighting of LEDs and long-term stability tests. This new concept can expand the possibility of EDL-based energy-harvesting devices.