Tubular Electrochemical Reactor Research Articles

An Analytical Model for Electrochemical Tubular Flow Reactors

This paper introduces the first analytical model designed for tubular electrochemical flow reactor, enabling a detailed examination of how reactor geometry and material selection impact performance. The model revealed that certain conditions, such as high electrode resistance relative to charge transfer, electrolyte, and separator resistance, can lead to uneven current distributions and reduced electrode utilization. The model highlights a critical electrode radius, dependent on reactor geometry and material properties, that minimizes the Area Specific Resistance (ASR) while minimizing reactor size. Additionally, it was found that the ASR increases with reactor length, but this effect can be mitigated by using highly conductive electrodes, thus allowing for enhanced power output. These insights provide a foundation for future research and the development of more efficient tubular reactor designs.

Hybrid-process including electrocoagulation for the real carwash wastewater treatment using a new continuous undivided tubular reactor

A coagulation-based continuous tubular electrochemical reactor has been designed to treat real carwash wastewater in a flow rate of 100 mL/min. This reactor made of an ordinary iron tube cathode with a commercial aluminum rod anode at the center. Equipment and chemicals needed for this method can be easily and cheaply obtained through non-scientific commercial sources. The one-factor at a time approach was used to investigate the effects of operating variables. Current density, flow rate, electrolysis time and electrode material were selected as independent variables while COD removal was considered as the response function. The experimental results showed that the proposed method can remove 89 % of COD from 10 liters of carwash wastewater in a "single-pass" and more than 99 % in a "double-pass" through the flow reactor. This reactor has short treatment time, low energy consumption, favorable mass transfer and low ohmic drop and does not need to adjust the pH or add electrolyte additionally to save costs. Also, this approach is resistant to undesirable phenomena such as passivation of the electrode surface, cell polarization, electrode surface fouling and reduction of electrical conductivity that may occur during electrolysis. The treated wastewater can be reused in the carwash industry as well as for irrigated agriculture.

Performance evaluation of a new continuous flow tubular electrochemical reactor with ceramic membrane for the treatment of wastewater

Performance evaluation of a new continuous flow tubular electrochemical reactor with ceramic membrane for the treatment of wastewater

Treatment of petroleum refinery wastewater by electrofenton process using a low cost porous graphite air-diffusion cathode with a novel design

A low-cost micro porous graphite air diffusion cathode (MPGADC) has been utilized successfully for the in-situ hydrogen peroxide generation via O2 reduction in 0.05 M Na2SO4. Using a tubular electrochemical reactor with a novel design composed of MPGADC as a cathode and a hollow cylinder porous graphite as an anode, a maximum of 68 mg/ L of H2O2 was produced at a current density of 25 mA/cm2, an air flow rate of 3 L/min, and a pH value of 3. Electro-Fenton (EF) process was adopted to remove the chemical oxygen demand (COD) from the wastewater of Al-Dora petroleum refinery in Iraq using this new style of tubular electrochemical reactor. Based on the response surface methodology (RSM) with Box-Behnken design (BBD), the effect of EF operating parameters on the COD removal was investigated.The optimal conditions for maximizing COD removal efficiency (RE%) with lowering specific energy consumption (SEC) using EF process were determined to be a current density of 6.66 mA/cm2, Fe2+ concentration of 0.80 mM, and an electrolysis duration of 60 min, in which RE% of 94% with SEC of 3.75 kWh/kg COD were achieved. In addition, the results demonstrated that the current density has the greatest influence on the COD removal, followed by electrolysis duration and then Fe2+ concentration. Furthermore, current density has the greatest impact on the specific energy consumption, followed by time, while Fe2+ concentration has a negligible effect. The high R2 value (98.33%) confirmed the goodness of fitting the model equation. These results established the viability of employing the new cathode design for the EF process in treatment of petroleum refinery wastewaters.

Optimization of chemical oxygen demand removal from petroleum refinery wastewater by electrocoagulation using tubular electrochemical reactor with a novel design

In this study, removal of chemical oxygen demand (COD) from petroleum refinery effluent was investigated using a new tubular electrochemical reactor (TER) design which operated at a batch recycle model. The electrochemical reactor comprises of two concentric electrodes namely spiral aluminum rode anode and hollow cylindrical stainless steel cathode. Four parameters were investigated: current density, sodium chloride concentration (NaCl), pH, and flow rate on the COD removal efficiency, and optimized using response surface methodology. Results show that current density is the most influential parameter on removal percentage where increasing current density results in increasing the removal efficiency. Another effect of lowering flow rate resulted in high removal of COD due to the increased resistance time of effluent passing on the surface of the anode with the newly adopted design. Finding of laboratory work were obtained under optimal working conditions such as current density of 26 mA/cm2, pH of 7.9, NaCl concentration of 1.1 g/L, and flow rate of 2 L/min. These were resulting in a COD removal efficiency of 73.36% with specific energy consumption of 30.61 kWh/kg·COD. Operating cost of the present system was found to be $2.185 m3 which is considered low and acceptable. Experimental results prove that the new design of TER is more efficient than the traditional design that uses in electrocoagulation system to treat wastewater generated from petroleum refinery plants.

Modeling of Tubular Electrochemical Reactor with a Spiral Design of Anode for Treatment of Petroleum Refinery Wastewater

Petroleum effluent is often made up of a complex combination of metals and organic molecules. In the present work, modeling of a tubular electrochemical reactor (TER) with a novel design operated at batch recycle for petroleum refinery effluent treatment by anodic oxidation was investigated. The reactor is composed from a cylindrical stainless steel cathode and a spiral porous graphite anode at its center. The impact of flow rate on the COD reduction and mass transfer coefficient (k) was studied. Results showed that increasing flow rate led to higher removal efficiency of COD and higher mass transfer coefficient where COD removal of 70% and k with value of 6.283x10-4 cm/s were obtained at flow rate of 4l/min. A power low correlation was obtained between mass transfer coefficient(k) and Reynolds number (Re) with coefficient of determination (R2) equal to 0.994869.This relation can be described as k=1.906x10-6(Re) 0.545 with range of Re 10000≤Re≤ 40000 prevailing turbulent conditions.

A novel Tubular Electrochemical Reactor with a Spiral Design of Anode for Treatment of Petroleum Refinery Wastewater

A novel Tubular Electrochemical Reactor with a Spiral Design of Anode for Treatment of Petroleum Refinery Wastewater

A study on the degradation of synthetic dyes using tubular electrochemical reactor

A study on the degradation of synthetic dyes using tubular electrochemical reactor

Ecuaciones de diseño de un reactor electroquímico tubular con electrodos concéntricos de mallas expandidas a través de un análisis teórico del micro/macromezclado de curvas de DTR

In the present work, the liquid flow pattern in a Tubular Electrochemical Reactor (TC-ECR) with concentric cylindrical expanded meshes as electrodes and inlet/outlet distributors of shower‑sprinkler type was evaluated. It was found that the CFD theoretical results describe the experimental F(t)-curves obtained with the methodology of “step-signal input”. Later, the F(t)-curves estimated with CFD for each reactor zone were adequately approximated with global parametric models for the development of the TER design equations. The Stagnant Zone Model with mass exchange with the anodic zone turns out to be adequate for the reactor shell zone. However, for the cathode and anode meshes, the Axial Dispersion Model with mass exchange between them proves to be appropriate. For all liquid flow rates (0.37 to 4.0 L min-1), the dispersion numbers (Nd) are in a magnitude order of small dispersion. This confirms that the incorporation of inlet/outlet distributors in a T-ECR improve considerably the liquid flow pattern behaviour. This experimental methodology, coupled with micro/macromixing theoretical analysis of RTD curves with CFD, can be a good alternative for the reactor design.

Kinetic and residence time distribution modeling of tubular electrochemical reactor: analysis of results using Taguchi method

Abstract Decolorization of dye waste water is performed using a tubular electrochemical reactor. Stainless steel and oxide coated on titanium mesh acts as the cathode and anode respectively. Experiments were conducted in batch with recirculation mode. The effect of operating parameters such as current density, initial dye concentration, flow rate and supporting electrolyte concentration on decolorization of Acid red dye has been studied and the results were analysed using Taguchi method. A residence time distribution (RTD) study has been conducted in a tubular electrochemical reactor and an axial dispersion model has been developed to determine percentage decolorization. The model results are compared with experimental results and it was found that the model satisfactorily matches with the experimental results with high correlation coefficient.

Overcoming diffusion limitations in electrochemical microreactors using acoustic streaming

We provide a theoretical background on laminar flow electrochemical reactors and rationally map typically encountered operating regimes in literature. At the highest (mass transfer limited) current densities attainable, the Fourier number (Fo) and the Sherwood number (Sh) are identified as important dimensionless groups for design considerations. The critical Fourier number places a severe constriction on the production capacity of a microreactor, as it determines the maximum throughput for a reactor of fixed length and inter-electrode distance. This critical Fourier number indicates that the absence of convective mixing and the reliance on diffusion of the electroactive species is the key problem to address for further intensifying electrochemical microreactors. Computer simulations are then used to illustrate the steady-state as well as transient behavior of generic case studies. These simulations also show that the transient response to a voltage step can be used to experimentally verify that the absence of mixing is a major bottleneck of laminar flow reactors. A versatile tubular electrochemical reactor was developed and applied to an acetonitrile solution containing ferrocene and benzylbromide, which is a simple model system for investigating self-supported synthesis (i.e., electrosynthesis without intentionally added supporting electrolyte). The reactor was then fitted with piezoelectric elements that excite a resonating standing wave in the flow direction, resulting in pairs of counter-rotating vortices in the fluid (acoustic streaming). The sonicated experiments prove that ultrasound assisted mixing reduces the critical Fourier number, enabling self-supported synthesis at elevated flow rates and throughput.

Modeling the process of convective mass transfer in a tubular electrochemical reactor

The model, describing a processes of convective masstransfering in a tubular electrolytic cell with the much distinguishing sizes of electrodes is proposed suitable for practical calculations.The electrochemical reactor permitting to clearing of water with the help of chemical reactions in bulk of a solution at participation of electrogenerated reagent is created.

Characterization of a tubular electrochemical reactor for the degradation of the commercial diuron herbicide

ABSTRACTAfter designing and constructing an electrochemical reactor with concentric electrodes and tangential feed (RECT), it is necessary to characterize it and to study its performance. The experimental study of the residence time distribution (RTD) was conducted for flow rates of 2.78 × 10–6 m3 s–1, 8.33 × 10–6 m3 s–1 and 13.9 × 10–6 m3 s–1. According to the values obtained from the Pe number (0.67–1.52), the RECT fits as tubular with great dispersion. The determined empirical correlation (Sh = 18.16 Re0.50 Sc0.33) showed a laminar flow behavior in the range of Reynolds number (Re) between 23 and 117. In order to use RECT in effluent treatment, an electrochemical oxidation study of the Diuron model molecule (Nortox®) was performed to analyze reactor performance in a closed system with total reflux. A decay kinetics of pseudo-first order was associated with the decay of the concentration of diuron and 30% mineralization in 180 min of process were obtained, having a total volume of 4 × 10–3 m3 and an initial concentration of commercial Diuron in 215.83 mg dm–3. Eleven by-products were identified by HPLC–MS analysis and, from this, it was possible to propose a route of degradation of the diuron. From these observations, it can be inferred that the studied electrochemical reactor had applicability in the degradation of recalcitrant compounds, as is the case of commercial diuron. Make some changes in the electrochemical reactor studied and other advanced oxidative processes, such as electro-Fenton, can be associated with the studied system to achieve a better conversion efficiency.

Electrochemical Hydrogen Peroxide Production in Acidic Medium Using a Tubular Photo-reactor: Application in Advanced Oxidation Processes

This paper describes the results obtained in the design and characterization of a tubular electrochemical reactor. The set-up was employed for on-site hydrogen peroxide (H2O2) production in an acidic medium (pH 3) to promote three electrochemical advanced oxidation processes (EAOP): electro-Fenton (EF), photoelectro-Fenton (PEF) and photocatalysis treatment (PT). These processes were evaluated by their abilities to degrade a commercial dye, Orange-II (OGII), in solution using total organic carbon (TOC) removal and high performance liquid chromatography (HPLC). To have free solutions of iron in the EF and PEF systems, a NafionTM membrane with dispersed iron was prepared. For use in photocatalysis, electrodes with a large superficial area were prepared by coating carbon cloth fiber supports with titanium dioxide (TiO2) using the electrophoretic (EP) method. In this work, wastewater samples with a large number of microorganisms (coliform bacteria) were treated with this new reactor design.

Characterization of hydrodynamics and electrochemical treatment of dye wastewater in two types of tubular electrochemical reactors

Electrochemical treatment is an environmentally friendly method of removing pollutants from industrial wastewater, and tubular electrochemical reactor is one kind of electrochemical reactor. However, the flow field on the electrode surface in a traditional concentric tubular reactor is not homogeneous, leading to low treatment efficiency of the reactors. Therefore, a new tubular electrochemical reactor based on spiral flow caused by a turbulence promoter is presented. In this work, fluid flow and hydrodynamics of the new tubular electrochemical reactor using computational fluid dynamics (CFD) method are studied by comparing them to the traditional one. The electro-oxidation of methylene blue simulation wastewater treatment was developed to analyze the processing efficiency of the two types of electrochemical reactors. In the new tubular electrochemical reactor, due to the presence of spiral turbulence promoter, the mean flow rate and turbulent intensity were clearly increased by 500-700% and nearly 200% compared to that of the traditional one, respectively. Under the same inlet-velocity, the removal rates of wastewater in the new tubular electrochemical reactor were also improved.

Co3+ homogeneous mediator generation efficiency in a divided tubular electrochemical reactor with MFI-type zeolite membrane

Abstract In the present work a tubular electrochemical cell with MFI-type zeolite coated membrane (TZM) was engineered and evaluated using Co 2+ oxidation efficiency in high acid medium. Electrolysis of Co 2+ was carried out at room temperature (20 ± 3 °C) in 4 M H 2 SO 4 at anodic half-cell, and showed 42% Co 2+ oxidation with 0.3 V higher cell voltage than the commonly used Nafion324 membrane in planar arrangement. Further, the TZM membrane was robust when operated in the cell at different temperatures (10, 30 and 50 °C) as no noticeable change in surface morphology was observable by SEM analysis. Further testing showed Co 2+ oxidation efficiency decreased with temperature and increased with current density, suggesting stable operation of the TZM but structural change in cobalt precursor. The TZM membrane showed less resistance 0.91 Ω cm 2 (at 10 °C) than Nafion324, which is decreased with increasing temperature from 10 °C to 50 °C. A 72 h test of the TZM at slightly elevated current density (70 mA cm 2 ) showed increased oxidation efficiency of Co 2+ to 57% compared to the traditional planar cell with Nafion324 (43%). Therefore, the engineered tubular electrochemical reactor with TZM is robust for generation of homogeneous mediators towards environmental pollution removal.

Degradation of Painting Ink Wastewater in a Tubular Reactor with Electrochemical Treatment

In the present study, electrochemical treatment experiments were conducted to degrade water-based printing ink wastewater. It was performed with ruthenium oxide coated titanium acting as anode and stainless steel tube as cathode. Electrolyses carried out in batch under steady conditions and operating at constant flow velocity between 0.538×10-3 and 6.129×10-3m/s. The evolution of color and COD removal, the value of pH were found to be inter-related. The kinetics for the concentration decays of the wastewater pseudo first-order reaction that is characteristic for a mass transfer controlled operation. The mass transfer coefficient kc increased with increasing flow velocity and Reynolds number. The evolution of color and COD removal, the value of pH were found to be inter-related. The effect of the parameters on current efficiency and energy cost has also been investigated. The tubular electrochemical reactor could be considered a feasible and an effective alternative system for the electrochemical treatment of water-based printing ink wastewater.

Electro oxidation of dye effluent in a tubular electrochemical reactor using TiO2/RuO2 anode

The aim of the present investigation is to treat Evans blue dye effluent using tubular electrochemical reactor. The electrode is made of stainless steel and oxide coated expanded titanium as cathode and anode respectively. The cylindrical mesh type anode is fitted in the tubular electrochemical reactor. The effect of operating parameters such as current density; initial dye concentration; initial solution pH, recirculation flow rate and supporting electrolyte concentration has been studied on COD reduction. It can be observed from the present investigation that the electrode Ti/RuO0.3Ti0.7O2 effectively degrade the Evans blue dye effluent and the kinetics of Evans blue dye degradation follows the pseudo first order kinetics. Further, dispersion model has also been developed to determine the exit concentration of the effluent. The model simulation is compared with experimental value and it is observed that the model matches well with correlation coefficient of 0.98.

Characterization of hydrodynamics and mass transfer in two types of tubular electrochemical reactors

Electrochemical treatment is an environmentally friendly method of removing pollutants from industrial wastewater. The tubular electrochemical reactor is one kind of electrochemical reactor. The current density distribution on the electrode surface in a traditional concentric tubular reactor is not homogeneous and the working area of the anodes and cathodes is unequal. Therefore, a novel tubular electrochemical reactor based on plug flow fluid orthogonal with mesh plate electrodes is presented. In this work, fluid flow and hydrodynamics of the vertical-flow tubular electrochemical reactor, such as velocity distribution and turbulent intensity distribution using computational fluid dynamics (CFD) method, are studied by comparing them to the traditional one. The electro-oxidation of phenol simulation wastewater treatment was developed to analyze the mass transfer performance of the two types of electrochemical reactors. In the novel tubular electrochemical reactor, due to the presence of mesh electrodes, the velocity distribution tended to be more homogeneous. In fact, the turbulent intensity clearly increased by 200% around the electrode surface. The kinetics of organic compounds removal in the novel tubular electrochemical reactor was also improved. Under the same flow rate, the improvement of the mass transfer coefficient for the novel tubular electrochemical reactor was more than twice that of the traditional tubular electrochemical reactor.

The Synthesis of Hydrocarbons for Fuel and Lubricants via Ceramic Membrane Reactor

Recently the development of alternative feed stocks for fuels and chemicals has received growing interest to reduce greenhouse gas (GHG) emissions from a variety of sources. One large source of GHG emissions is long haul transportation of people and goods by ground, sea, and air. For the foreseeable future, long haul transportation will continue to depend on infrastructure compatible hydrocarbon fuels. The use of fuels synthesized from alternative renewable feed stocks such as biomass is one way to reduce the GHG emissions from these modes of transportation. Processes currently being commercialized to convert biomass into fuels and chemicals rely on high energy reactions that require catalysts and/or hydrogen. These restraints require centralized processes and result in high conversion cost. In order for biomass based fuel and chemicals to have a significant market penetration they need to compete economically with petroleum based streams, thus finding ways to reduce the cost of the biomass conversion is essential. As part of a project to produce infrastructure compatible fuel and chemicals Ceramatec is developing an electrochemical process, adapted from the Kolbe electrolysis. This process converts fatty acids from a biomass origin into long chain hydrocarbons, which can be further converted into lubricants and fuel using existing infrastructure. The conventional Kolbe electrolysis has been investigated since 1849 when Kolbe applied it to the synthesis of different hydrocarbons. The reaction pathway is generally considered to follow a mechanism in which a one electron oxidation at an electrode surface generates a radical and CO2. The radical can then undergo homo- or hetero- coupling with other radicals generated at the surface of the electrode.[1] While it has been extensively studied, the Kolbe electrolysis has never been widely commercialized because of low efficiency and yield caused by the high over potentials and reactivity of the electrolyte that are conventionally used. To circumvent these shortcomings, Ceramatec’s decarboxylation process uses a two compartment electrochemical reactor, where the compartments are separated by a ceramic membrane.[2] The separation afforded by the membrane (NaSelect®) is such that Na-ions are exclusively (>99% efficiency) transferred between the compartments, allowing different electrolytes to be used for the anolyte and catholyte. This affords: 1) the anolyte to be customized for the electrolysis of interest, and 2) the catholyte to be designed to have high conductivity and a low reduction potential. The latter helps reduce the overall cell potential, improving the energy efficiency of the process. The use of this membrane requires the anolyte to contain sodium salts of carboxylic acids, thus the anodic reaction can be represented generically by the reaction below. 2RCO2Na → R-R + 2CO2 + 2e -+ 2Na+ The Na-ions that are produced in the anolyte are then transferred across the membrane to the cathode compartment, where the corresponding reduction reaction occurs, as shown below using water as an example. 2H2O + 2e- +2Na+ → 2NaOH + H2 The sodium hydroxide produced in the cathode compartment can be used to saponify the fatty acid feed stock, making it a closed loop system for sodium. Also, the use of the two compartment reactor causes the distance between the anode and cathode to be separated into three regions: 1) the distance between the anode and the membrane, 2) the membrane thickness, and 3) the distance between the membrane and the cathode. This separation decreases the length of diffusion through the anolyte, permitting the anolyte conductivity to be sacrificed for improved oxidative stability. We have used these benefits to optimize the decarboxylation process, obtaining saturated hydrocarbons with yields and electrical efficiency over 80% while maintaining a low power consumption of 1.8 kWh/L ($0.18/L). These oxygen free hydrocarbons are produced using a modular process without the use of hydrogen. This process has also been scaled up in a self-contained portable pilot unit designed to produce over 1 L/day of saturated hydrocarbons from a tubular electrochemical reactor. The pilot unit is being used to address scale-up issues at a modular level and obtain data that is needed to help determine the economic feasibility of the process on an industrial scale. The results of this reactor optimization and scale-up will be discussed. Also, results using the membrane reactor to produce different high value chemicals will be shared. Acknowledgement This material is based upon research supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under Agreement No. 2012-10008-20263.