Plug Flow Reactor Research Articles

Isomerization of Cis-2-Butene to Trans-2-Butene in a Plug Flow Reactor: A Simulation Study Using Aspen HYSYS V14

Abstract—This study investigates the isomerization of cis-2-butene to trans-2-butene in a single-tube Plug Flow Reactor (PFR) using Aspen HYSYS V14 for process simulation. The reaction is modeled as a homogeneous, irreversible isomerization with first-order kinetics (rate constant k=0.003833 s−1). The objective was to determine the optimal reactor volume and channel diameter to achieve 95% conversion of cis-2-butene under specified conditions: 1 meter reactor length, 100 kgmol/h feed rate, 12 bar pressure, and 25°C. The Peng-Robinson fluid package was employed for thermodynamic calculations. Simulation results indicate that a reactor volume of 2.268 m³ and channel diameter of 1.699 m are required to achieve the target conversion. This study demonstrates the efficacy of Aspen HYSYS in reactor design optimization and provides valuable insights for industrial applications of butene isomerization. The methodology presented offers a robust framework for addressing similar chemical engineering challenges. Keywords: aspen HYSYS, butene, isomerization, plug flow reactor, process simulation. Abstrak—Penelitian ini menyelidiki isomerisasi cis-2-butena menjadi trans-2-butena dalam Reaktor Aliran Sumbat (PFR) tabung tunggal dengan menggunakan Aspen HYSYS V14 untuk simulasi proses. Reaksi dimodelkan sebagai isomerisasi homogen irreversible, dengan kinetika orde pertama (konstanta kecepatan reaksi k = 0,003833 s−1). Tujuan penelitian ini adalah menentukan volume reaktor dan diameter saluran yang optimal untuk mencapai konversi cis-2-butena sebesar 95% di bawah kondisi yang telah ditentukan: panjang reaktor 1 meter, laju umpan 100 kgmol/jam, tekanan 12 bar, dan suhu 25°C. Paket fluida Peng-Robinson digunakan untuk perhitungan termodinamika. Hasil simulasi menunjukkan bahwa volume reaktor sebesar 2,268 m³ dan diameter saluran sebesar 1,699 m diperlukan untuk mencapai konversi yang ditargetkan. Penelitian ini menunjukkan efektivitas Aspen HYSYS dalam optimasi desain reaktor dan memberikan wawasan berharga untuk aplikasi industri isomerisasi butena. Metodologi yang dipresentasikan menawarkan kerangka kerja yang kuat untuk mengatasi tantangan rekayasa kimia serupa. Kata kunci: aspen HYSYS, butena, isomerisasi, plug flow reaktor, simulasi proses

Design of A PFR For the Production of 1,000,000 Tons Per Year of Ethyl Acetate from Esterification of Acetic Acid and Ethyl Alcohol

The research considered the design or size of a plug flow reactor for the production of 1,000,000 tons of ethyl acetate per year from the esterification of acetic acid and ethyl alcohol in the presence of an acid catalyst. The PFR design models for volume, height, diameter, space time, space velocity, quantity of heat generated, quantity of heat generated per unit volume of the reactor as well as the temperature effect models were developed using the conservation principle of mass and energy at steady state operation of the reactor. The developed models were simulated using MATLAB at initial feed and operating temperature of 299.830k and 343.15k respectively and fractional conversion variation between 0 to 0.95 at an interval of 0.05. At a maximum conversion of 0.95, the PFR size specification for volume, height, diameter, space time, space velocity, quantity of heat generated and the quantity of heat generated per unit volume of the reactor was 15.2774m3, 4.2691m, 2.1346m, 2.9956sec., 0.3338sec-1, 12821.5800j/s and 839.2536j/sm3 respectively. The effect of the operating parameters on the performance or functional parameters of the reactor are presented in profiles as shown in figure 2 to 12 and the profile behaviour or trend were in agreement with process behaviour of PFR steady state operation in various literatures. The research have shown that in order to ensure sustainability and continuous production of ethyl acetate to meet the global demand of the economic and viable product, the plug flow reactor have demonstrated a good performance characteristics as a reacting media for the esterification process especially in the energy efficiency of the process as well as the product yield.

Genome reduction improves octanoic acid production in scale down bioreactors.

Microorganisms in large-scale bioreactors are exposed to heterogeneous environmental conditions due to physical mixing constraints. Nutritional gradients can lead to transient expression of energetically wasteful stress responses and as a result, can reduce the titres, rates and yields of a bioprocess at larger scales. To what extent these process parameters are impacted is often unknown and therefore bioprocess scale-up comes with major risk. Designing platform strains to account for these intermittent stresses before introducing synthesis pathways is one strategy for de-risking bioprocess development. For example, Escherichia coli strain RM214 is a derivative of wild-type MG1655 that has had several genes and whole operons removed from its genome based on their metabolic cost. In this study, we engineered E. coli strain RM214 (referred to as WG02) to produce octanoic acid from glycerol in batch-flask and fed-batch bioreactor cultivations and compared it to an octanoic acid-producing E. coli MG1655 (WG01). In batch flask cultivations, the two strains performed similarly. However, in carbon limited fed-batch bioreactor cultivations, WG02 provided a greater than 22% boost to biomass compared to WG01 while maintaining similar titres of octanoic acid. Reducing the biomass accumulation of WG02 with nitrogen limited fed-batch cultivation resulted in a 16% improvement in octanoic acid titre over WG01. Finally, in a scale-down system consisting of a stirred tank reactor (representing a well-mixed zone) and plug flow reactor (representing an intermittent carbon starvation zone), WG02 again improved octanoic acid titre by almost 18% while maintaining similar biomass concentrations as WG01.

Optimization and modeling of biodiesel production from oleic acid in plug flow reactor

In recent years, biodiesel has been preferable to fossil fuels because of its renewability, biodegradability, and producibility from various wastes. In this study, the esterification reaction between oleic acid and methanol was carried out in the presence of sulfuric acid, which is a homogeneous acid catalyst, to produce biodiesel. Experiments were carried out in a plug flow reactor (PFR) and a batch reactor. The experimental conditions with the highest conversion obtained in the PFR were determined and applied to the batch reactor and results were compared. The effects of temperature (45, 55, 65 in Celsius), catalyst concentration (2%, 4%, 6% by weight), and methanol/oleic acid mole ratio (3, 6, 9) on oleic acid conversion were examined in the PFR. Retention times at different flow rates were calculated to determine the reaction time in the PFR and reactions were carried out between 2 and 6 minutes. In the reactions carried out in the PFR, the highest conversion value was obtained as 97.33% under conditions where the catalyst concentration was 6% by weight, the temperature value was 55oC and the alcohol/acid mole ratio was 6:1. These conditions were applied to the batch reactor and the conversion value was found to be 50%. When the experimental results were examined, it was seen that the effect of temperature and alcohol/acid ratio on the conversion was greater than the effect of the catalyst concentration on the conversion. The modeling of oleic acid/methanol esterification, i.e., biodiesel production, at specific boundary values was found to follow a cubic dependence in the general dependence equation via Response Surface Methodology.

Simulation of Acetylene Formation from Methane in a Plasma Jet

This work is devoted to the numerical modeling of the reaction of methane conversion to acetylene under plasma-jet pyrolysis conditions and a comparison of the obtained results with the available experimental data. The calculations were performed within the framework of the ideal plug-flow reactor model for atmospheric pressure. The analysis of the main processes of methane decomposition and acetylene formation was carried out in cases where either hydrogen or methane was used as a plasma-forming gas. The results of calculations of the main products of methane decomposition (hydrogen and acetylene) agree quite well with the experimental data.

Performance of a RuCs/MgO catalyst coated on additive manufactured support structures via electrophoretic deposition for ammonia synthesis

This work investigates the electrophoretic deposition of a catalytic coating on so-called fluid guiding elements (FGE) with a ruthenium-based catalyst for use in ammonia synthesis reactors. FGE are additive manufactured metallic pipe inserts that have shown to enhance the heat transfer compared to empty pipes by dividing the fluid flow and alternately guiding the partial flows to the wall. Consequently, they could improve the performance of temperature sensitive structured catalytic systems. To be able to demonstrate the degree of process intensification, the required steps to enable the deposition of a reference catalyst for ammonia synthesis are developed. Further, the distribution of catalytically active compounds is characterized. The catalytic activity is assessed in a plug flow reactor under pressures up to 5MPa and compared against a fixed bed from the same batch. The expected activity from the reference catalyst is calculated by a kinetic rate expression. The coating process does not affect catalytic activity, but a steady deactivation and high sensitivity to feed gas impurities are observed. Possible mechanisms for the deactivation are examined and discussed.

Optimization of Power to Gas system with cooled reactor for CO2 methanation: Start-up and shut-down tests with Ru-based and Ni-based kinetics

The dynamic behavior of a methanation process is analyzed in the context of Power to Gas (PtG) technology, to convert carbon dioxide from different sources and hydrogen produced via electrolysis with renewable energy to synthetic methane. The process configuration consists of a single cooled plug flow reactor (PFR) where both ruthenium and nickel-based kinetic models are tested in the Aspen Dynamics simulation environment. In particular, dynamic analyses are performed to study the start-up and shut-down phases and respect injection parameters in the existing gas network. The process consists of three main sections: conditioning, reaction and separation. After the development and optimization of the control system, the start-up and shut-down tests are carried out, to study the trend of composition for the injection in the gas network. The plant size is set according to the following values: 700 Nm3/h of hydrogen and 175 Nm3/h of carbon dioxide, which correspond to the methanation reaction stochiometric ratio. Different cases are considered in both the start-up and shut-down tests, by changing the GHSV values and the catalyst adopted. Moreover, in the shut-down test two different rates are considered to evaluate the behavior of the system.

Investigating the formation of soot in CH4 pyrolysis reactor: A numerical, experimental, and characterization study

Methane pyrolysis is a promising method for eco-friendly hydrogen production, but soot formation and carbon interaction pose challenges for scaling up. Therefore, understanding the dynamics of soot formation and carbon deposition is crucial. This study delves into the intricacies of soot formation in methane pyrolysis under industrially relevant conditions, namely operations at atmospheric pressure, employing a H2:CH4 ratio of 2 and exploring a range of hot zone temperatures (1473 K, 1573 K, 1673 K, and 1773 K) with a 5 s residence time. Utilizing a detailed gas-phase kinetic model with direct carbon deposition reactions, the research adopts the method of moments coupled with a one-dimensional plug flow reactor model to simulate soot formation. The model is validated by characterizing soot particles that were produced in a pyrolysis reactor by means of transmission electron microscopy, Dynamic light scattering (DLS), and Raman spectroscopy. Results show that lower temperatures lead to nucleation-dominated growth, whereas higher temperatures significantly restrain particle growth due to carbon deposition. DLS data indicate a complex balance between particle growth and deposition processes. These findings provide insights into operational parameters that can enhance reactor performance and sustainability in hydrogen production processes by mitigating soot and carbon deposition.

A multistage biogas slurry reflux and spray anaerobic digestion reactor for high solid anaerobic digestion: Performance and application evaluation

In this study, a new vertical plug-flow continuous dry anaerobic digestion reactor equipped with a spray percolation system was designed for rice straw and cow manure in dry AD. The findings indicated that the methane yield was 290.63 ± 19.16 mL/g VS when the optimal spray time (9 times/d) was used in batch AD. In addition, the results of continuous experiments under optimal spray time conditions showed that the volumetric methane production rate of the system was 1.55 L/(L·d) when the organic loading rate was 20 g VS/(L·d). In addition, hydrolysis and acidification steps were enhanced. This study demonstrated the potential of the new reactor for stable operation of high OLR dry AD. Digestate is already used as a substitute for synthetic fertilizers precisely because of the environmental benefits associated with its agronomic use.

Rate expression model from thermodynamics application and optimal kinetic parameters determination for urea synthesis and production process

Urea, an essential organic fertilizer, enhances soil fertility by providing 0.466 nitrogen for maximum crop yield. In this study, urea is synthesized from NH3 and CO2 in an equilibrium reaction process adhering to Le Chatelier's principle, maintained under process conditions: flow rate of 63.5 kg/s, temperature of 184 °C, and pressure of 160 kg/cm2. A new rate expression model, formulated in terms of extent of reaction and mole fraction, was developed based on mass action relations and thermodynamic models. Two industrial reactors were considered: a plug flow reactor (PFR) at Notore and a continuous stirred tank reactor (CSTR) at Indorama plants. Transient reactor models, based on material and energy balance conservation principles, were numerically resolved using MATLAB version 2020 with specified input conditions. A non-linear regression statistical optimization model was employed to refine kinetic parameter values, ensuring optimal and high-quality urea yield. Model validations were conducted using literature data, revealing higher urea yields of 0.726 and 0.7032 for the CSTR and PFR, respectively. Deviations (0.134, 0.10 to 1.135 and 0.635, 0.326 to 0.850) and root mean square errors (RMSE) (0.043, 0.033 to 0.193 and 0.137, 0.087 to 0.162) were observed when validated against plant and literature values for the CSTR and PFR respectively. The refined kinetic parameters (activation energies, Arrhenius constants, and rate constants) exhibited negligible deviations (0.0004–0.0466 and 0.0004 to 0.0491) and RMSE (0.0228, 0.0055, and 0.0256 and 0.0241, 0.0096, and 0.0269) when validated against plant data, significantly enhancing urea yield in CSTR and PFR reactors respectively.

Impact of random packing on residence time distribution of particles in bubbling fluidized beds: Part 1–cross-current flow reactors

In this work, the influence of employing random packings on the residence time distribution in a bubbling fluidized bed is investigated. The bubbling fluidized bed cold-flow reactor setup allows for continuous cross-current flow of particles. Expanded clay aggregate (ECA) is employed in the packed-fluidized bed experiments as the packing. The effects of different parameters such as packing type (ECA or no packing), Fluidization number (4.4, 6.6, and 8.8), and solid throughflow rates (92, 133, and 164 g/s) are investigated. The axial dispersion and tank-in-series models are used to categorize flow patterns of particles in the packed-fluidized beds and compared to beds using no packing. Results show that the vessel’s dispersion number for solids decreases in the presence of ECA packings up to fourfold compared to unpacked beds. Furthermore, tank-in-series model shows that the number of tanks for experiments utilizing packing increases by up to threefold compared to unpacked beds. The experimental results are also compared to a model known as a hybrid model. The hybrid model considers a continuous-stirred-tank-reactor in series with a plug-flow-reactor. Comparison of the model to the measured data shows a clear shift of the relative size or residence time from the stirred tank reactor towards the plug flow reactor with axial dispersion in the packed-fluidized bed compared to a bed with no packing. Also the vessel dispersion number of the plug flow reactor model with axial dispersion is significantly decreased in the case of packed-fluidized bed.

Elaboration of Yttrium Aluminum Garnet (YAG) nanopowders and ceramics: Comparison between batch and plug-flow reactor

In this study YAG (Y3Al5O12) nanopowders have been synthetized by a reverse co-precipitation method with two different designs of reactors: batch and plug-flow. The impact of both the reactor design and the synthesis temperature on the features of nanopowders so-synthetized was studied. The reactor design governs the pH evolution and precipitation kinetics during synthesis. Correlations were found between the reactor design and nanopowders stoichiometry and morphology. The plug-flow reactor allows obtaining homogeneous, well-crystallized and single-phased YAG nanopowders after calcination. Then, the sintering ability of as-obtained nanopowders was investigated. Fully dense YAG-based ceramics were obtained with the nanopowders made from the plug-flow reactor by combining uniaxial pressing and sintering at 1700 °C. Finally, a plug-flow reactor with very simple and inexpensive design would allow easier upscale of the synthesis process of YAG-based nanopowders with well-controlled morphology and stoichiometry. As a result, YAG based transparent ceramic were obtained without sintering additive.

Solving crystallization/precipitation population balance models in CADET, Part II: Size-based Smoluchowski coagulation and fragmentation equations in batch and continuous modes

A particle size-based Smoluchowski coagulation and fragmentation equation was solved in the free and open source process modeling package CADET. The WFV and MCNP schemes were selected to discretize the internal particle size coordinate. Weights in these schemes were modified to preserve and conserve the zeroth and third moments for size-based equations. Modified propositions and proofs for the scheme are provided. Analytical Jacobians were derived and implemented to reduce the solver’s runtime. A two-dimensional Smoluchowski coagulation and fragmentation equation with axial position as external coordinate was formulated and discretized to support simulations of continuous particulate processes in dispersive plug flow reactors. Five 1D and four 2D test cases were used to validate the implementation and benchmark the solver’s performance. The runtime, L1 error norm, L1 error rate, particle size distribution moments up to sixth order and several scalar metrics were analyzed in detail.

Mini Bubble Columns for Miniaturizing Scale‐Down

ABSTRACTThe successful scale‐up of biotechnological processes from laboratory to industrial scale is crucial for translating innovation to practice. Scale‐down simulators have emerged as indispensable tools in this endeavor, enabling the evaluation of potential hosts’ adaptability to the dynamic conditions encountered in large‐scale fermenters. By simulating these real‐world scenarios, scale‐down simulators facilitate more accurate estimations of host productivity, thereby improving the process of selecting optimal strains for industrial production. Conventional scale‐down systems for detailed intracellular analysis necessitate an elaborate setup comprising interconnected lab‐scale reactors such as stirred tank reactors (STRs) and plug‐flow reactors (PFRs), often proving time‐consuming and resource‐intensive. This work introduces a miniaturized bubble column reactor setup (60 mL working volume), enabling individual and parallel carbon‐limited chemostat fermentations, offering a more efficient and streamlined approach. The industrially relevant organism Escherichia coli, chosen as a model organism, is continuously grown and subjected to carbon starvation for 150 s, followed by a return to carbon excess for another 150 s. The cellular response is characterized by the accumulation of the alarmone guanosine pentaphosphate (ppGpp) accompanied by a significant reduction in energy charge, from 0.8 to 0.7, which is rapidly replenished upon reintroduction of carbon availability. Transcriptomic analysis reveals a two‐phase response pattern, with over 200 genes upregulated and downregulated. The initial phase is dominated by the CRP–cAMP‐ and ppGpp‐mediated response to carbon limitation, followed by a shift to stationary phase‐inducing gene expression under the control of stress sigma factors. The system's validity is confirmed through a thorough comparison with a conventional STR/PFR setup. The analysis reveals the potential of the system to effectively reproduce data gathered from conventional STR/PFR setups, showcasing its potential use as a scale‐down simulator integrated in the process of strain development.

High-solid digestion – A comparison of completely stirred and plug-flow reactor systems

High-solid digestion (HSD) for biogas production is a resource-efficient and sustainable method to treat organic wastes with high total solids content and obtain renewable energy and an organic fertiliser, using a lower dilution rate than in the more common wet digestion process. This study examined the effect of reactor type on the performance of an HSD process, comparing plug-flow (PFR) type reactors developed for continuous HSD processes, and completely stirred-tank reactors (CSTRs) commonly used for wet digestion. The HSD process was operated in thermophilic conditions (52 °C), with a mixture of household waste, garden waste and agricultural residues (total solids content 27–28 %). The PFRs showed slightly better performance, with higher specific methane production and nitrogen mineralisation than the CSTRs, while the reduction of volatile solids was the same in both reactor types. Results from 16S rRNA gene sequencing showed a significant difference in the microbial population, potentially related to large differences in stirring speed between the reactor types (1 rpm in PFRs and 70–150 rpm in CSTRs, respectively). The bacterial community was dominated by the genus Defluviitoga in the PFRs and order MBA03 in the CSTRs. For the archaeal community, there was a predominance of the genus Methanoculleus in the PFRs, and of the genera Methanosarcina and Methanothermobacter in the CSTRs. Despite these shifts in microbiology, the results showed that stable digestion of substrates with high total solids content can be achieved in both reactor types, indicating flexibility in the choice of technique for HSD processes.

Dynamic decarburisation model of AOD process: Based upon the FactSage-Macro Programme

Improving the quality of stainless-steel hinges significantly on precisely managing decarburisation within the argon-oxygen decarburisation (AOD) process. This study introduces a dynamic model capable of accurately predicting the composition and weight of steel and slag. To thoroughly investigate the refining processes, a systematic analysis was conducted, integrating three essential adiabatic zones within the AOD converter: the continuous stirred-tank reactor, slag bath and plug flow reactor, supported by circulation and recirculation streams. FactSageTM software and its macro facility were utilised to identify the different phases present in steel and slag. This dynamic model not only forecasts critical process parameters like temperature, composition and volume of multiple phases but also enables the prediction of the final chromium content for different initial carbon inputs, specifically at 2%, 1.5% and 1 wt.%. By comparing the model's predictions with actual plant data, it was observed that the transient compositions of steel and slag exhibited consistency, confirming the model's validity and reliability in simulating AOD refining processes.

A comprehensive kinetic modeling study on NH3/H2, NH3/CO and NH3/CH4 blended fuels

Ammonia (NH3), as an ideal zero-carbon fuel, plays a positive role in mitigating global warming. By cofiring NH3 with highly reactive small molecule fuels such as hydrogen (H2), carbon monoxide (CO) and methane (CH4), the reactivity of NH3 combustion can be significantly enhanced. In this work, a detailed kinetic mechanism for NH3/CH4/H2/CO containing 146 species and 1099 reactions was developed and extensively validated with selected experimental data from the literature on laminar burning velocity (LBV), ignition delay time (IDT), and species concentrations measured in burner-stabilized flames (BSF), plug flow reactors (PFR) and jet-stirred reactors (JSR), covering temperatures of 273–2000 K, pressures of 0.053–40 atm and equivalence ratios of 0.1–2. In addition, the detailed mechanism was simplified to include 53 species and 353 reactions using three simplification methods. Kinetic modeling analysis showed that the chemical and transport effects of H2, CO and CH4 are the main factors enhancing NH3 combustion, which rising with the increasing initial temperature and decreasing ammonia blending ratio. Among the four reactants, H2 is consumed first, followed by CH4 and NH3, with CO reacting last. By modifying the Metghalchi-Kech power law equation, it was found that a clear linear relationship exists between LBV and the sum of the maximum mole fractions of O, H, OH, and NH2 radicals.

Chromium removal from concentrated ammonium-nitrate solution: Electrocoagulation with iron in a plug-flow reactor

Highly concentrated ammonium nitrate (AN) solutions are characteristic of explosives manufacturing wastewaters and liquid fertilizer commodities, but chromium (Cr) contamination from corroding metal infrastructure or source impurities can pose problems. Technologies are needed to decontaminate AN from Cr without chemical alterations if AN is to be recovered as a resource. Iron-based electrocoagulation is a proven way to produce Fe(II) for reducing dissolved Cr(VI) to the less soluble and less toxic form of Cr(III), but is an untested technology for AN brines. This work examined Cr removal from synthetic wastewater with high concentrations of AN (400 g/L) by electrocoagulation in a flow-through reactor, where the effects of time, solution flow rate, applied current, and coexisting ions were analyzed. This method not only reduces Cr(VI) to Cr(III) using the produced Fe(II), but also promotes complete Cr removal from solution with the formation of insoluble Fe-Cr precipitates. A slower flow rate and higher applied current increased the removal efficiency of the reactor; furthermore, the reactor took up to one hour to reach steady state conditions, depending on the flow rate. Cr concentrations along the anode length were modeled using a simplified advection–dispersion-reaction model, providing reaction rate coefficients for various flow rates and currents. Overall, the results of this work showed that electrocoagulation with iron can be used for treatment of AN solution contaminated with Cr(VI). This work also provides design guidelines with a corresponding model for field applications in future work.

Optimizing ozone treatment for pathogen removal and disinfection by-product control for potable reuse at pilot-scale

Reclaimed water poses environmental and human health risks due to residual organic micropollutants and pathogens. Ozonation of reclaimed water to control pathogens and trace organics is an important step in advanced water treatment systems for potable reuse of reclaimed water. Ensuring efficient pathogen reduction while controlling disinfection byproducts remains a significant challenge to implementing ozonation in reclaimed water reuse applications. This study aimed to investigate ozonation conditions using a plug flow reactor (PFR) to achieve effective pathogen removal/inactivation while minimizing bromate and N-Nitrosodimethylamine (NDMA) formation. The pilot scale study was conducted using three doses of ozone (0.7, 1.0 and 1.4 ozone/total organic carbon (O3/TOC) ratio) to determine the disinfection performance using actual reclaimed water. The disinfection efficiency was assessed by measuring total coliforms, Escherichia coli (E. coli), Pepper Mild Mottle Virus (PMMoV), Tomato Brown Rugose Fruit Virus (ToBRFV) and Norovirus (HNoV). The ozone CT values ranged from 1.60 to 13.62 mg min L−1, resulting in significant reductions in pathogens and indicators. Specifically, ozone treatment led to concentration reductions of 2.46–2.89, 2.03–2.18, 0.46–1.63, 2.23–2.64 and > 4 log for total coliforms, E. coli, PMMoV, ToBRFV, and HNoV, respectively. After ozonation, concentrations of bromate and NDMA increased, reaching levels between 2.8 and 12.0 μg L−1, and 28–40.0 ng L−1, respectively, for average feed water bromide levels of 86.7 ± 1.8 μg L−1 and TOC levels of 7.2 ± 0.1 mg L−1. The increases in DBP formation were pronounced with higher ozone dosages, possibly requiring removal/control in subsequent treatment steps in some potable reuse applications.

Multiphysics Modeling of Electrode Dissolution Under Hydrodynamic Conditions in Low Conductivity Water

Efficient plug-flow electrochemical reactors are characterized by their ability to effectively convert species with significant ionic strength and/or with the assistance of a well-behaved electrolyte. Because of the classic electroconductivity requirement, electrochemical reactors are not particularly attractive options for applications with low-conductivity conditions, especially for low-pressure feeds. However, these reactors can still find application in dedicated processes such as ultra-clean water conditioning and biological-coupled separation systems. Consequently, a multi-physics model was developed using COMSOL Multiphysics to characterize different reactor-design conditions based on the Tertiary Current Distribution which accounts for the effects of expected variations in electrolyte composition and ionic strength on the electrochemical process, as well as solution resistance and electrode kinetics. The modelling framework presented here employs single-phase laminar fluid flow, the Nernst-Planck equation, the water-based electroneutrality condition, and concentration-dependent overpotentials. This investigation particularly explores the electrolysis process of “anodic dissolution,” in which elemental species dissociate from the solid matrix of the electrode and enter the liquid phase of the electrolyte as soluble ions. The reactor configuration of interest has a rectangular parallel-electrode design and is operated galvanostatically. A series of parametric studies are carried out to inspect the response of the system when hydrodynamic, kinetic, and geometric conditions are changed. The parametric sweep resulted in variable effluent concentrations and system voltage, which reveal underlaying optimization patterns for electrode dissolution in low conductivity water.