Planar Reactor Research Articles

A platinum-coated staggered reactor to intensify lean hydrogen/air combustion: A large eddy simulation study

Catalytic-aided combustion has been proven effective for premixed hydrogen/air mixtures, particularly under lean to ultra-lean conditions. However, minimising the required catalyst sets a significant challenge because noble metals with high catalytic activity are rare and expensive. Therefore, this study aims to intensify the catalytic combustion process by investigating a non-planar reactor comprising an array of platinum-coated half- and full-cylinders through large eddy simulation. A premixed mixture with a fuel-lean equivalence ratio of 0.15 and an incoming Reynolds number of 3500 based on hydraulic diameter is used. For comparison, a planar reactor without cylinders is also studied under the same operating conditions and with the same amount of platinum-coated surface area. The simulation employs the turbulent kinetic energy sub-grid model and the eddy dissipation concept to model the turbulent catalytic reacting flow. The discrete ordinate model is used to account for radiation heat transfer in the catalytic process. Numerical simulations are validated against experimental results prior to analysis. The findings indicate that the placement of cylinders along the reactor length enhances convective mass transfer and intensifies catalytic combustion, resulting in effective combustion over a smaller catalytic surface. Compared to planar models, non-planar reactors demonstrate a much better H2 conversion efficiency throughout the reactor length, saving nearly 62.5 % of the catalyst.

Enhancing the performance of catalysts in turbulent premixed fuel-lean hydrogen/air combustion

Catalytic-aided combustion is a proven technique for burning highly lean and ultra-lean mixtures of hydrogen and air. However, the noble catalyst required for combustion is naturally scarce and therefore expensive. In this study, we focus on a numerical investigation to determine the best way of coating a platinum catalyst inside a catalytic hydrogen reactor. We study various planar and non-planar reactors and find that the reactor with a combination of half and full cylinders is the most effective in H2 conversion. Compared to an equivalent catalytic planar reactor, the non-planar configuration increases the H2 conversion by 30.7 %. The results show that enhancing mass and heat convection can significantly increase the H2 conversion. Furthermore, in a non-planar reactor, surfaces with an enhanced mass and heat transfer can achieve up to 50 % catalyst savings when coated with a catalyst, while still maintaining a conversion rate of 2 kg/s per unit of catalytically-coated surface area.

CFD—ANN study on axial dispersion in helical and serpentine millimetric coils

CFD simulations are reported to compare hydrodynamic/axial dispersion in a classical helical-shaped and planar serpentine-shaped tubular reactor at a millimetric scale (1-5 mm) for the first time. A two-step simulation approach is validated against experimental data on residence time distribution in serpentine coils. The method is then used for parametric analysis to explore the impact of geometric parameters on the coiling factor and axial dispersion coefficient. Dean vortices in the coiling region are visualized. The findings from the parametric analysis are utilized to develop empirical correlations and Artificial Neural Network (ANN) models for estimating coiling factors and axial dispersion coefficients in both serpentine and helical coils. The absolute average relative error (AERR) in predicting the coiling factor is 3.5% for helical coils and 4.6% for serpentine coils. The AERR of the ANN model for predicting the axial dispersion coefficient is 14% for helical coils and 10% for serpentine coils. The study reveals that both axial dispersion coefficient and pressure drop are higher in serpentine coils compared to helical coils. Axial dispersion is found to be relatively unaffected by pitch (helical) or bend diameter (serpentine) and tube diameter but shows significant reduction with a decrease in pitch circle diameter (helical) or gap between bends (serpentine). The developed correlations and ANN models can aid in the precise sizing of tubular reactors designed as helical or serpentine coils. This is exemplified through a case study involving the synthesis of an ionic liquid, where the helical configuration demonstrated a performance advantage of approximately 6% over the serpentine configuration.

The integrated microfluidic photocatalytic planar reactor under continuous operation

An integrated microfluidic planar reactor is essential for achieving efficient and enhanced photocatalytic water treatment. Optimization of catalysts is an area of intense study owing to the need to enhance the performances of microreactors. A high-efficiency photocatalytic microreactor is presented here by combining a planar microreactor with a high-efficiency photocatalyst. TiO2 nanoparticles doped with Y and Yb were prepared to improve the photocatalytic reaction efficiency. First, better performance is achieved with the Y, Yb/TiO2 and TiO2 microreactors than conventional bulk reactors because of good photodegradation and a high reaction rate. Then, the Y, Yb/TiO2 film microreactor exhibits not only efficient catalytic activity with UV light but also higher photocatalytic activity under visible light irradiation than that achieved by a TiO2 film microreactor. The reaction rate constant of the Y, Yb/TiO2 film microreactor is approximately 0.530 s–1, which is twice that of the TiO2 film microreactor. Moreover, the performances under continuous and intermittent reactions are compared to evaluate the stability of the microreactor, thereby building the foundation for practical application of continuous water treatment in the microreactor.The planar microreactor provides a convenient platform for studying photodegradation under various conditions, such as different temperatures, flow rates, light irradiation (UV and Vis), and reaction modes (continuous and intermittent).

Simulated solar light-driven degradation of micropollutant in water by biochar-based metal-free catalyst: Regulation strategies for electronic structure and morphology engineering

The biochar/h-BN/g-C3N4 (BNC) composite photocatalyst with a spherical sheet cluster structure, was successfully synthesized. Under simulated solar light irradiation, the photocatalytic degradation rate of reactive red 120 by BNC was 87.94 % within 90 min, corresponding to a 3.57-fold higher kinetic constant than that of g-C3N4. The band structure and electron transfer path in BNC were determined using characterizations and density functional theory (DFT) calculations, confirming a type II heterojunction forming. The attraction of h-BN to h+ by electrostatic interaction and biochar's capacity for both electron transfer and storage were confirmed. Doping of biochar was also found to enhance light absorption and provide O vacancy. The existence of piezoelectric effect assisted the movement of photogenerated carriers to the material surface. In the system, the main active oxidation species were h+ and ·O2–. By calculating optical characteristics, the practical activity of photocatalysts is evaluated. Results indicated that the optimal dosage of BNC was 0.5 g/L in the planar reactor, corresponding to an optical thickness of 2.61 calculated by the six-flux radiation absorption–scattering model (SFM). Biochar doping was found to enhance light absorption. A novel photocatalytic mechanism was proposed for promising matel-free BNC.

Production of Novel Tubular Electrochemical Hydrogen Compressor

For most applications, especially transport, hydrogen needs to be compressed due to its low volumetric density. Conventionally, mechanical compressors are used for hydrogen compression, but they possess disadvantages such as high maintenance due to moving parts and a limited one-stage compression ratio. A promising technology to overcome those obstacles is electrochemical hydrogen compression, in which hydrogen is compressed in an electrochemical membrane reactor.To date, only planar electrochemical reactors for hydrogen compression have been investigated although tubular designs offer advantages in membrane area to reactor volume ratio, sealing options, pressure stability and reactor complexity. However, high contact and membrane resistances and scalable manufacturing processes are still challenges to be addressed for the advent of tubular electrochemical compressors in application.Herein we introduce a manufacturing process for tubular electrochemical hydrogen compression reactors. The developed cell comprises a catalyst coated porous tubular anode covered by a tubular proton exchange membrane, which was subsequently coated with the cathode catalyst layer. The porous anode was prepared via metal 3D printing. 3D printing enables tailored porosity and geometry by which mass transport is enhanced. The catalyst layer was applied by manual spray coating. Constant current experiments and electrochemical impedance spectroscopy were performed to characterize the as prepared tubular electrochemical compressor. The results revealed the importance of tailored contacting concepts and the optimization of components regarding water transport, as the efficiency of the process is dominated by contact and membrane resistances.

Fabrication of Fe-Based Nanocrystalline Powder-Pressed Magnetic Core and Application to Planar Reactor for Hundreds of kHz or Beyond

In this study, to decrease coercivity and iron loss for the Fe-Si-B-Nb-Cu-C nanocrystalline powder-pressed magnetic core for hundreds kHz or beyond, a post annealing after pressing the Fe-Si-B-Nb-Cu-C amorphous powder was executed for nanocrytallization and release of the residual strain induced through the pressing the powder. In addition, novel fabrication procedure for obtaining the small coercivity powdered magnetic core was proposed. It was found that the fabricated Fe-Si-B-Nb-Cu-C nanocrystalline powdered magnetic core exhibited a saturation magnetization of 0.91 T, coercvity of 123 A/m, relative permeability of 32.5 and iron losses of 105 kW/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> at 100kHz, 50mT and 2194 kW/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> at 1MHz, 50mT. From the iron loss break-down for the fabricated Fe-Si-B-Nb-Cu-C nanocrystalline powdered magnetic core, its hysteresis and eddy current losses were smaller than those of Fe-Si-B-C-Cr powder-pressed magnetic core. In addition, a planar reactor was fabricated using the powder-pressed magnetic core, which had a size of 47×44×16 mm, DC coil resistance of 7.3mΩ, inductance of 12.1 μH, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> -factor of about 127 at 1MHz and inductance drop of 4.1% at a superimposed DC current of 30A.

Effect of UV-C LED arrangement on the sterilization of Escherichia coli in planar water disinfection reactors

In this study, a planar UV reactor with five distinct UV-C LED arrangements was proposed to treat drinking water. The particle tracing method combined with computational fluid dynamics were used to simulate water velocity field, microbial trajectory and residence time. The ray tracing method was used to determine the irradiance distribution in water. The simulated variables were then integrated to determine the distribution of fluence in water. Both experimental and theoretical results among the five distinct UV light modules used in this study, turn-enhanced emission exhibited the highest efficiency in sterilizing Escherichia coli owning to the synergic effect of hydrodynamics and UV radiation. Turn-enhanced emission combined with turn-induced secondary flow effectively improved the reactor performance. At a flow rate of 300 mL/min, turn-enhanced emission resulted in an inactivation value of 4.56 log, which was approximately 0.90, 0.82, 0.84, and 2.41 log higher than the values obtained with top, staggered, lined, and side emission, respectively. According to the particle count and cumulative count of the fluid particles, turn-enhanced emission effectively enhanced the UV fluence to which microbes in water were subjected. In conclusion, optimal combinations of LED arrangements and channel configurations effectively improve the sterilization efficiency of UV reactors.

Experimental study of the effect of dielectric materials on the decomposition of carbon dioxide in a dielectric barrier discharge

The low-temperature nonequilibrium characteristics of dielectric barrier discharge (DBD) make it an important candidate for the decomposition and conversion of CO2. In this study, quartz, alumina and zirconia are selected as the dielectrics to investigate the effect of dielectric materials of planar DBD reactor on the discharge and conversion characteristics of CO2. It is shown that under the same input power conditions, zirconia has the highest CO2 conversion rate when used as a dielectric, followed by alumina, and quartz has the lowest. Combined with the analysis of the measured electrical characteristics, it is shown that zirconia has the highest transferred charge, thus further increasing the discharge efficiency. Experimental results of the single dielectric barrier layer-metal mesh electrode reactor show that the CO2 discharge can operate in the lower power range and the CO2 conversion rate is higher than that of the double dielectric barrier layer reactor. Spectroscopic measurements show that the emission intensity of the discharge in the reactor with high relative permittivity materials is higher than that in the case of low relative permittivity materials, and the emission intensity of the single dielectric layer reactor is also higher than that in the case of the double dielectric layer reactor.

Analysis of ozone generation in a planar atmospheric pressure air dielectric barrier discharge reactor

This work investigates O3 production in a planar atmospheric pressure air dielectric barrier discharge reactor numerically and experimentally. The surface temperature of the reactor is measured by an infrared (IR) thermal imager, and the O3 densities of cases in the reactive zone are measured by ultraviolet absorption spectroscopy. The 1.5D plasma fluid model (PFM) with transverse convection is employed to capture the average properties of a single microdischarge (MD) generated in the reactor. The concept of equivalent reaction is proposed to calculate spatial-cyclic average species sources obtained by the 1.5D PFM and provided to the chemical model of a 3D gas flow model (GFM) for obtaining density distributions of reactive species generated by MDs in the reactive zone. The simulated temperature distribution of the reactor surface is validated by that measured with the IR thermal imager since the gas temperature was reported as a critical discharge parameter for O3 generation. The simulated O3 densities show the same trend as the flow rate changes, which demonstrates the proposed model captures the average discharge dynamics in different operating conditions. In the 1.5D PFM, the simulated results show that the O3 molecules produced in the case of 4 SLM are much more than those produced in the case of 1 SLM though the O atoms produced in the case of 1 SLM are around 20% more than those produced in the case of 4 SLM. In the case of 1 SLM, more than 48% of O3 molecular generated are destructed, while only around 14% of O3 molecules are destructed in the case of 4 SLM. The analysis shows that around 73% of O atoms generated in the 1.5D PFM are consumed in the formation of O3 molecules in the case of 4 SLM, while only 18% of O atoms generated in the case of 1 SLM are consumed in the formation of O3 molecules. In the 3D GFM, the O3 destructed is around 24% of that destructed in the 1.5D PFM in the case of 4 SLM due to the oxidation reaction of NO, while only 11% of O3 molecules destructed as that destructed in the 1.5D PFM in the case of 1 SLM. The amounts of O3 molecules generated in the 3D GFM are minor if they are compared with those generated in the 1.5D PFM in all cases. The overall O3 yield efficiency reaches 97 g kWh−1 with the O3 concentration increasing up to 2700 ppm in the case of 4 SLM, while the O3 yield efficiency decreases to 10 g kWh−1 and O3 concentration drops to 1400 ppm in the case of 1 SLM.

Dissolvable alginate hydrogel-based biofilm microreactors for antibiotic susceptibility assays

Biofilms are found in many infections in the forms of surface-adhering aggregates on medical devices, small clumps in tissues, or even in synovial fluid. Although antibiotic resistance genes are studied and monitored in the clinic, the structural and phenotypic changes that take place in biofilms can also lead to significant changes in how bacteria respond to antibiotics. Therefore, it is important to better understand the relationship between biofilm phenotypes and resistance and develop approaches that are compatible with clinical testing. Current methods for studying antimicrobial susceptibility are mostly planktonic or planar biofilm reactors. In this work, we develop a new type of biofilm reactor—three-dimensional (3D) microreactors—to recreate biofilms in a microenvironment that better mimics those in vivo where bacteria tend to form surface-independent biofilms in living tissues. The microreactors are formed on microplates, treated with antibiotics of 1000 times of the corresponding minimal inhibitory concentrations (1000 × MIC), and monitored spectroscopically with a microplate reader in a high-throughput manner. The hydrogels are dissolvable on demand without the need for manual scraping, thus enabling measurements of phenotypic changes. Bacteria inside the biofilm microreactors are found to survive exposure to 1000 × MIC of antibiotics, and subsequent comparison with plating results reveals no antibiotic resistance-associated phenotypes. The presented microreactor offers an attractive platform to study the tolerance and antibiotic resistance of surface-independent biofilms such as those found in tissues.

Highly efficient solar-driven CO2 reforming of methane via concave foam reactors

Solar-driven CO2 reforming of methane into value-added syngas is promising to solve global climate change and energy crisis problems simultaneously. However, there remains a large gap between currently reported solar-to-fuel efficiency and the theoretical limit. Here, we proposed an alternative way to enhance solar-driven CO2 reforming of methane performances by shaping foam reactors into concave geometries. By coupling solar radiation transport, fluid-solid coupling heat transfer, thermochemical kinetics, non-isothermal flow and mass transfer, a numerical analysis model is built. For the uniform planar reactor, multi-parameter optimization of porosity, pore diameter, and reactor length is conducted through a multi-island genetic algorithm, and the optimized solar-to-fuel efficiency achieves as high as 50.4%. By shaping planar foam reactors into parabolic concave geometries, the solar-to-fuel efficiency further increases 53.3%, the efficiency is increased by 21.97% compared with the reactor without multi-parameter optimization. This superior performance can be attributed to more uniform and appropriate temperature distribution, which makes major reactant components react within a higher temperature range above 1000 K. This work provides alternative routes for designing high-performance porous foam reactors and achieving highly efficient solar-driven CO2 reforming of methane.

Planar reactor with a serpentine channel for water disinfection by using ultraviolet C light-emitting diodes

Water sterilization efficiency is affected by water flow patterns and irradiance distribution, which in turn are affected by reactor design. In this study, a planar flow reactor with a serpentine channel was used to treat drinking water by using 278-nm ultraviolet (UV)-C light-emitting diodes. The effects of various water flow rates, channel widths, and baffle lengths were investigated to understand their effects on fluid mixing and flow trajectory. The experimental results revealed that the UV reactor with a channel width of 13 mm exhibited the highest log inactivation value for Escherichia coli among the reactors with three different channel widths. This is because this width maximized the exposure time and increased the secondary flow at the turn regions in the serpentine channel. Furthermore, the baffle length dramatically affected the flow trajectory, circulation zones, and microbial exposure time. This length was optimized at 22 mm for all the investigated flow rates. The developed UV reactor achieved an inactivation value of 4.0 log for E. coli at a maximum water flow rate of 80 mL/min.

Planar water disinfection reactor with parallel-channel configurations

A novel planar water disinfection reactor is proposed to treat potable water with UV-C LED. Parallel-channel configurations are employed to increase the flow uniformity, microbial exposure time and UV fluence for microorganisms. The effects of flow rate, baffle width and number of flow channels (n) are examined to elevate the efficiency of sterilizing Escherichia coli (E. coli). Experimental results indicate that the four-channel reactor exhibited the highest inactivation efficiency owing to high flow uniformity, sufficient exposure time and circulation elimination in the flow channel. The reactor achieved 4.0 log at a flow rate of 29 mL/min and a total radiative power of 80 mW. The disinfection flow rate was 45% higher than that of the reactor without channel configuration. Increasing the number of channels helps eliminate circulations and achieve uniform flow distribution. However, microbial exposure time and UV fluence decrease with increased number of channels. Additionally, when the baffle width was less than 6 mm, the log inactivation increased with baffle width due to the increase in the degree of flow uniformity. The flow reactor achieves optimal disinfection efficiency at baffle width 6 mm due to an optimal combination of flow variation and water velocity.

Mathematical modeling of the electric field in the planar and coaxial dielectric barrier discharge reactor in water treatment application

PurposeTo design a pulse power water treatment system, it is necessary to design a reactor optimally. One of the most essential types of reactors used in water treatment is the dielectric barrier discharge (DBD) reactor. The purpose of this paper is to model the electric field in the two types of planar and coaxial reactors to have an accurate analytical formula for using in the optimal design according to the required electric field of the treatment.Design/methodology/approachThe method proposed in this paper focuses on the voltage of different areas in the reactor and different boundary conditions to obtain the surface charge density. In this regard, parameters of the dielectric and treated material, as well as the reactor dimension, have been affected in the equations. To confirm the analytical results, the finite element method simulation has been performed, and it shows the accuracy of this method.FindingsThe exact analytical equation of the electric field is found within the discharge zone of the planar and coaxial DBD reactors. These equations can predict the values of different parameters of the reactor required to purify the material before each design and it does not even require simulation.Originality/valueThe electric field formula presented in this paper can allow the manufacturers of pulse power water treatment systems to optimize their design easily, cost-effectively and in less time. Also, the formulas provided are completely general and remain effective for all materials.

Modeling of indoor air treatment using an innovative photocatalytic luminous textile: Reactor compactness and mass transfer enhancement

Indoor air pollution is a complex problem that involves a wide range and diversity of pollutants that threaten human health. In this context, significant efforts must be made to improve the quality of indoor air. It is therefore important to start controlling the sources of indoor pollution. However, where eliminating or minimizing sources of emissions is not technically feasible, technologies to reduce them should be used. The present work deals with the photocatalytic depollution of hospitals indoor air, using a continuous photocatalytic process. In order to get closer to real conditions, two model pollutants representing the indoor air of hospitals were chosen as targets; chloroform (CHCl3) and glutaraldehyde (C5H8O2). The photocatalytic oxidation of VOCs alone and their mixture (binary mixing system) has been studied on a pilot scale. Indeed, the experiments were carried out in a continuous planar reactor using a new technology based on the TiO2/optical fiber photocatalyst.The effects of experimental conditions such as air flow rate (4–12 m3.h−1), VOCs inlet concentration (4–40 mg.m−3) and humidity levels (5–90%) were pointed out. The photocatalytic effect of the OF-TiO2 composite was found to be improved under UV irradiation as compared to TiO2. The presence of water molecules in small amounts (less than RH = 30%) can promote the degradation process due to the formation of •OH radicals. Biomolecular Langmuir-Hinshelwood model including mass transfer step has been developed to represent the process behavior. Reusability test show that the optical fiber -based photocatalysts presented good photocatalytic activities towards CHCl3/C5H8O2 removal.

Electrochemically Engineered, Highly Energy-Efficient Conversion of Ethane to Ethylene and Hydrogen below 550 °C in a Protonic Ceramic Electrochemical Cell

Ethylene is one of the largest building blocks in the petrochemical industry, mainly produced by steam cracking of ethane derived from naphtha or shale gas at high temperatures (>800 °C). Despite its technical maturity and economic competitiveness, the thermal steam cracking of ethane is highly energy-intensive. Herein, an electrochemically engineered direct conversion process of ethane to produce hydrogen and ethylene using a planar protonic ceramic membrane reactor with a bi-functional three-dimensional catalytic electrode is reported, with a single-pass ethane conversion of 40% and ethylene yield of 26.7% at 550 °C. Compared with the industrial ethane steam cracking, this method saves process energy input by 45.1% and improves process energy efficiency by 50.6%, based on comprehensive process simulation using Aspen Plus software. Further, steam electrolysis treatment under the solid oxide electrolysis cell mode can regenerate the system’s catalytic performance and significantly alleviate catalytic degradation by 74%, demonstrating high techno-economic viability.

Mixing Performance of Planar Oscillatory Flow Reactors with Liquid Solutions and Solid Suspensions

The mixing performance of planar oscillatory flow reactors (planar-OFRs) with liquid solutions and solid suspensions was investigated. The planar-OFR is a relatively new variant of the OFR where th...

Innovative photocatalytic reactor for the degradation of VOCs and microorganism under simulated indoor air conditions: Cu-Ag/TiO2-based optical fibers at a pilot scale

This study deals with photocatalytic application for indoor air pollution remediation. Two target compounds were selected: Butane-2,3-dione (C4H6O2) and Heptan-2-one (C7H14O). Escherichia coli (E. coli) were used as bacteria strain. Photocatalytic removal of VOCs alone, E. coli alone and their mixture (VOCs/E. coli) were evaluated, at pilot scale. Indeed, a series of experiments were carried out in a continuous planar reactor using a novel photocatalyst/TiO2 technology with metal wires e.g. Copper (Cu)/Silver (Ag)-woven in optical fiber. Effects of experimental conditions such as flow rate (2–12 m3.h−1), VOCs inlet concentration (5–20 mg.m−3) and humidity levels (5–70%) on removal efficiency were investigated to properly appraise the oxidation performance in real conditions. All textile fiber photo-catalysts (TiO2, TiO2-Cu and TiO2-Ag) showed good photocatalytic activities towards C4H6O2/C7H14O removal. As for simultaneous application with VOCs and E. coli: (i) in terms of VOCs removal efficiency, the same trend of performance was observed compared to VOCs experiments alone: 63% of removal efficiency by TiO2 alone, 46% by TiO2-Ag and 52% by TiO2-Cu, (ii) in terms of E. coli inactivation, only experiments with TiO2-Cu and TiO2-Ag revealed a good performance.

A Tubular Electrochemical Reactor for Slurry Electrodes.

The research on electrochemical reactors is mostly limited to planarly designed modules. In this study, we compare a tubular and a planar electrochemical reactor for the utilization of the slurry electrodes. Cylindrical formed geometries demonstrate a higher surface‐to‐volume ratio, which may be favorable in terms of current density and volumetric power density. A tubular shaped electrochemical reactor is designed with conductive static mixers to promote the slurry particle mixing, and the vanadium redox flow battery is selected as a showcase application. The new tubular design presents similar cell resistances to the previously designed planar battery and shows increased discharge polarization behavior up to 100 mA cm−2. The volumetric power density reaches up to 30 mW cm−3, which is two times higher than that of the planar one. The battery performance is further investigated and 85 % coulombic, 70 % voltage and 60 % energy efficiency is found at 15 mA cm−2 with 15 wt.% slurry content.