Reactors In Series Research Articles

Petrochemical condensate treatment by membrane aerated biofilm reactors: A pilot study

An OxyMem membrane aerated biofilm reactor (MABR) pilot of two ~ 54 L reactors in series with a hydraulic retention time (HRT) of 10 h each was successfully applied for the treatment of real petrochemical condensate with a total organic carbon (TOC) concentration of ~ 100 mg/L. The main aim was to (i) evaluate the removal efficiency (RE) of main petrochemical pollutants and (ii) to examine the operational performance of the two on-site pilot-scale MABR units. The start-up/inoculation of the reactors in batch mode, followed by continuous pilot operation on synthetic feed, and the transition from synthetic to an actual petrochemical feed were covered. At stable operational conditions on the actual feed, the pilot in series achieved an overall RE for TOC, biological oxygen demand (BOD5), organic acids, phenol, and ammonia of 80–85%, ~95%, >98%, ~98%, and 70–90%. The system in series demonstrated high resilience to process fluctuations, high treatment efficiency of the complex feed, and the ability to develop a diverse biofilm. In terms of oxygen transfer rate (OTR), oxygen transfer efficiency (OTE), and specific aeration efficiency (SAE) values of > 1.5 g/m2/day, > 21%, and > 6.5 kg O2/kWh were achieved. Such values outcompete the aeration efficiency (AE) of conventional activated sludge (CAS) processes and demonstrate the potential of MABRs to achieve higher OTE. Based on the collected data, the MABR concept in series can be considered highly effective for treatment of petrochemical streams.

Theoretical framework for mixer design for noise reduction and gradient fidelity

The mixing of two or more solvent streams to deliver a stable and accurate solvent composition is crucial to the performance, repeatability and reproducibility of a liquid chromatographic separation. We provide a theoretical treatment of axial mixing of a sequence of solvent packets with the framework of continuous stirred tank reactors (CSTRs) in series and investigate the tradeoffs presented between the primary goal of mixers (noise reduction) and it's necessary side-effects of gradient deformation and asymmetry. An experimental setup to mimic CSTR conditions was created using a stop-flow setup where the fluid flow was periodically paused and sonicated within pods of a certain volume. The effects of mixer volume relative to the volume of pump strokes and gradient volumes were investigated and discussed.A total mixer volume that is six-fold the pump stroke volume was found to be necessary to achieve sufficient (95%) noise reduction necessary for certain applications. A series of two or more CSTR elements was found to outperform a single CSTR element for larger mixer-to-pump stroke volume ratio in dampening baseline noise. For linear gradients, a gradient volume that is ten times larger than the mixer volume was found to sufficiently maintain gradient fidelity. For very small gradient volumes relative to the mixer volume, deformation of linear gradients was found to be significantly greater than predicted by the analytical solution. Furthermore, the nature of the solvent gradient deformation was asymmetric, with the latter half of the solvent gradient deforming significantly more than the first half.Combining analytically and numerically derived solutions for multiple CSTRs connected in series with experimental data, several suggestions can be made on mixer dimensions and design for a certain pump system and method transfer, given a pump stroke volume and gradient time.

Design and Implementation of a Parallel-Connected Fault Current Attenuator for Power Distribution Systems

Parallel-connected fault current attenuator (PFCA) is a novel concept for active reduction of short-circuit currents (SCCs) through circuit breakers (CBs) in power distribution grids. The sustained increase in the SCCs could exceed the rating of the CBs, dangerously spreading the fault. Several series-connected schemes, such as fault current limiters and series reactors, have been proposed in recent decades to reduce these high currents. This article designs and experimentally verifies the feasibility of a parallel-connected power converter to reduce the SCCs, operating as a controlled current source by absorbing current from the fault point. This new configuration reduces the SCCs in all CBs of an electrical substation. The proposed PFCA is implemented using a single-phase neutral-point clamped (NPC) converter and tested using a predictive current control scheme for short-circuits in a scaled-down power system. The experimental results prove the effectiveness of the proposed scheme, reducing significantly the first SCC peak, even when the ac bus voltage is close to zero.

Free-radical polymerization of methacrylic acid: From batch to continuous using a stirred tank reactor

In the last years important efforts have been made to convert the traditional batch polymer production to continuous. This transition allows to overcome most of the limitations of discontinuous or semi-continuous processes, such as environmental and safety issues and inadequate product quality. In this work we propose a model–based strategy to convert the solution free-radical polymerization of non-ionized methacrylic acid (MAA) from semibatch to continuous while preserving the product average molecular weight and polymer content. First, a purely kinetic model for the polymerization of MAA was validated for batch, semibatch and continuous stirred tank reactors (CSTR). Then, a basic optimization approach was applied to guide the transition of a selected semibatch process to a CSTR. This strategy results in a substantial productivity increase (5.1 times higher than in the original semibatch) while preserving the selected polymer average molecular weight and dry content. Finally, in order to reduce the residual monomer in the product leaving the CSTR, we simulated the addition of a tubular reactor. This was modelled introducing a small plug flow reactor in series to the CSTR. This approach represents an effective and robust tool for polymer manufacturers to assist switching their productions to continuous preserving their product portfolio.

Two moving bed biofilm reactors in series for carbon, nitrogen, and phosphorous removal from high organic wastewaters

Government regulations require on-site treatment of industrial wastewater prior to sewage discharge to prevent environmental degradation of receiving waterbodies. The sequencing batch moving bed biofilm reactor (SB-MBBR) can permit on-site treatment of high organic and nutrient content of cheese production wastewater. However, the critical challenge exists of maintaining both an active heterotrophic and an autotrophic population in a single biofilm system treating carbon and ammonia to low discharge levels from cheese production wastewater. Two SB-MBBRs in series separate the heterotrophic and autotrophic communities, circumventing the competition between the heterotrophic and autotrophic populations in a single biofilm system treating wastewater with high carbon to nitrogen ratios. The first reactor (AN/AE) was operated by cycling between anaerobic and aerobic stages to select for polyphosphate accumulating organisms, and the AN/AE reactor degraded carbon and phosphorous. The second reactor (NIT) was operated with aerobic conditions to promote nitrifying bacteria and treat total ammonia nitrogen. The performance of this system for carbonaceous constituents and ammonia was evaluated by quantifying the kinetics, biofilm morphology, thickness, dry-mass, and dry-density of the two SB-MBBR in series technology. The AN/AE reactor achieved 97.5 ± 1.7%, 58.8 ± 5%, and 49 ± 1% soluble chemical oxygen demand, total nitrogen, and total phosphorous removal efficiencies respectively. The NIT reactor achieved 98.7 ± 2.4 % total ammonia nitrogen removal, though partial nitritation at rates of 1.09 ± 0.03 g-N·m-2d-1, indicating this system can be incorporated in an anammox system. The study demonstrates that enhanced biological phosphorous removal, and potentially anaerobic removal of ammonia can be achieved for on-site treatment of cheese production wastewater.

Experimental and theoretical investigations of a new cascaded reactor for ammonia as a renewable fuel

Although there has been the commercially employed and widely used Haber-Bosch ammonia synthesis process which requires the high operating pressure and temperature in addition to the relatively low conversion rates, there is a need for a more compact and modular, but more efficient and effective approach. In conjunction with this, the present study develops, tests and investigates a cascaded ammonia synthesis system to explore the room for improvement in the ammonia conversion efficiencies. A lab-scale prototype is developed to investigate the effect of cascading two ammonia synthesis reactors in series employing pre-reduced KMR catalyst and the experimental investigations revealed the improved ammonia synthesis rates using cascaded configuration. The scanning electron microscopy (SEM) results of the KMR catalyst are also presented at different magnifications of 2.00 kx and 50.0 kx. The Aspen Plus simulation results of the cascaded ammonia synthesis system have also been validated using the experimental results and validation shows the percentage difference ranging from 1.62–6.61%. The experimentally developed cascaded ammonia synthesis system is investigated under different operating temperatures and pressures. The experimental results revealed that the ammonia conversion efficiencies that range from 4.58–7.88% using the single reactor with pressure rise from 6 to 12 bar at the temperature of 370 °C, increase to the conversion efficiencies of 5.42–9.16% by employing cascaded ammonia synthesis design.

DC-Saturated Continuously Variable Series Reactors (CVSRs) for Power Flow Control in Power Transmission Systems

This paper proposes a novel continuously variable series reactor (CVSR) based on a dc current controller (DCC) to manage power flow in transmission systems. There are three major contributions. First, the three-dimensional electromagnetic interaction has been comprehensively analyzed to extend the understanding beyond the conventional 2D relationship. Second, a high-fidelity reluctance model of the CVSR with an improved DCC model is proposed and implemented. To overcome the fundamental concern for the system modeling, the DCC has been modeled as an ideal current source in parallel with an output impedance. The induced back-EMF can be precisely projected which provides critical design guidelines for the DCC. Third, inspired by the theoretical analysis and modeling, a reliable high power DCC converter is designed accordingly to interface with kV-level back-EMF and supply kA-level dc current for a 115 kV/1500 A CVSR. Experiments are conducted in a practical transmission demonstration system. When the ac current in the transmission system varies from zero to 1500 A, experimental results show that the proposed CVSR can continuously regulate the reactance from 1.6 Ω to 5 Ω, validating the effectiveness of the proposed system design and modeling methodology.

A novel CO2 utilization technology for the synergistic co-production of multi-walled carbon nanotubes and syngas

Dry reforming of methane (DRM) is a well-known process in which CH4 and CO2 catalytically react to produce syngas. Solid carbon is a well-known byproduct of the DRM but is undesirable as it leads to catalyst deactivation. However, converting CO2 and CH4 into solid carbon serves as a promising carbon capture and sequestration technique that has been demonstrated in this study by two patented processes. In the first process, known as CARGEN technology (CARbon GENerator), a novel concept of two reactors in series is developed that separately convert the greenhouse gases (GHGs) into multi-walled carbon nanotubes (MWCNTs) and syngas. CARGEN enables at least a 50% reduction in energy requirement with at least 65% CO2 conversion compared to the DRM process. The second process presents an alternative pathway for the regeneration/reactivation of the spent DRM/CARGEN catalyst using CO2. Provided herein is the first report on an experimental demonstration of a 'switching' technology in which CO2 is utilized in both the operation and the regeneration cycles and thus, finally contributing to the overall goal of CO2 fixation. The following studies support all the results in this work: physisorption, chemisorption, XRD, XPS, SEM, TEM, TGA, ICP, and Raman analysis.

Trace organic contaminants removal from municipal wastewater using the FluHelik reactor: From laboratory-scale to pre-pilot scale

The main goal of this study is to evaluate the feasibility of the innovative FluHelik photoreactor for the removal of antimicrobial drugs at residual concentrations using a photochemical UVC/H2O2 process. Experiment studies were performed using either pure water (PW) or secondary effluent from municipal wastewater treatment plant (EW) fortified with gatifloxacin (GAT) (100 µg L−1) as a model antimicrobial contaminant. Initially, the efficiency of the UVC/H2O2 process towards GAT removal as a function of UVC lamp power (4–11 W), H2O2 dose (25–200 mg L−1), flow rate (20–180 L h−1), flow mode (single vs multiple pass) and matrix (PW or EW) was assessed. Afterwards, the system efficiency was evaluated according to engineering features such as association of reactors in series and scale-up design. The performance of the FluHelik reactor was quantitatively measured through the use of a figure-of-merit, photochemical space-time yield (PSTY), that encompasses the three main contributing factors in UVC/H2O2 systems (i.e. throughput, energy efficiency and photochemical oxidation). In this context, FluHelik scale-up to pre-pilot scale proved to be feasible as similar PSTY values were obtained at both scales for assays performed with EW. In addition, the pre-pilot scale system was able to degrade all pharmaceutical compounds originally detectable in the EW matrix, reducing their concentrations to values below limit of detection. Finally, in order to test whether the treated solution might develop antibiotic resistance when in the environment, antimicrobial activity assays using bacterial cultures of Bacillus subtilis and Escherichia coli were investigated. The antimicrobial activity in the solutions dropped as the reaction time increased.

Модели ядерного реактора BBEP-1000 с разбиением на зоны по вертикальной оси для информационной технологии управления

Разработаны математические модели энергетического ядерного реактора ВВЭР-1000 с разбиением на зоны по вертикальной осью в виде нелинейных систем дифференциальных уравнений с безразмерными относительными переменными состояниями. Модели в заданном количестве зон по вертикальной осью представляют нейтронную кинетику, постепенное тепловыделение, тепловые процессы в топливе, оболочках и теплоносители, изменения концентрации йода, ксенона и бора. По конструктивным и технологическим параметрам ядерного реактора серии В-320 вычислены параметры математических моделей. Получена общая модель реактора как объекта управления с разбиением на зоны за вертикальной осью, а также модели с управлением поглощающими стержнями и борной кислотой. Интегрирование полученных систем дифференциальных уравнений при заданных начальных условиях позволяет получить изменения всех переменных состояний в зонах реактора по вертикальной осью. В частности, по изменению мощности в зонах по вертикальной осью вычисляется аксиальный офсет как относительное значение разности мощностей верхней и нижней половин активной зоны реактора. Разработанные модели реактора с безразмерными относительными переменными состояниями используют минимальное количество вычислений, позволяющие вычислить изменение аксиального офсета реактора и включенные в информационную технологию управления энергоблоками атомных электрических станций для оптимизации маневренных режимов реактора ВВЭР-1000 серии В-320.

Design and Analysis of Fault Current Limiter Based on Air Core Variable Series Reactor

Design and Analysis of Fault Current Limiter Based on Air Core Variable Series Reactor

Modelling of the Acetification Stage in the Production of Wine Vinegar by Use of Two Serial Bioreactors

In the scope of a broader study about modelling wine acetification, the use of polynomial black-box models seems to be the best choice. Additionally, the use of two serially arranged bioreactors was expected to result in increased overall acetic acid productivity. This paper describes the experiments needed to obtain enough data for modelling the process and the use of second-order polynomials for this task. A fractional experimental design with central points was used with the ethanol concentrations during loading of the bioreactors, their operation temperatures, the ethanol concentrations at unloading time, and the unloaded volume in the first one as factors. Because using two serial reactors imposed some constraints on the operating ranges for the process, an exhaustive combinatorial analysis was used to identify a working combination of such ranges. The obtained models provided highly accurate predictions of the mean overall rate of acetic acid formation, the mean total production of acetic acid of the two-reactor system, and ethanol concentration at the time the second reactor is unloaded. The operational variables associated with the first bioreactor were the more strongly influential to the process, particularly the ethanol concentration at the time the first reactor was unloaded, the unloaded volume, and the ethanol concentration when loading.

Process Configuration Studies of Methanol Production via Carbon Dioxide Hydrogenation: Process Simulation-Based Optimization Using Artificial Neural Networks

Methanol production via carbon dioxide (CO2) hydrogenation is a green chemical process, which can reduce CO2 emission. The operating conditions for minimum methanol production cost of three configurations were investigated in this work. An artificial neural network with Latin hypercube sampling technique was applied to construct model-represented methanol production. Price sensitivity was performed to study the impacts of the raw materials price on methanol production cost. Price sensitivity results showed that the hydrogen price has a large impact on the methanol production cost. In mathematical modeling using feedforward artificial neural networks, four different numbers of nodes were used to train artificial neural networks. The artificial neural network with eight numbers of nodes showed the most suitable configuration, which yielded the lowest percent error between the actual and predicted methanol production cost. The optimization results showed that the recommended process design among the three studied configurations was the process of methanol production with two reactors in series. The minimum methanol production cost obtained from this configuration was $888.85 per ton produced methanol, which was the lowest methanol production cost among all configurations.

Evaluation of continuous ethyl ester synthesis from acid soybean oil using a dual immobilized enzyme system

The use of non-edible oils, waste oils, and animal fats have been investigated as a low-cost feedstock for biodiesel (fatty acid alkyl esters) synthesis. However, these alternative raw materials have some drawbacks due to the high content of free fatty acid (FFA). This work aimed to study the continuous enzymatic ethyl esters synthesis, in a solvent-free system, from the reaction of acid soybean oil (acid value, AV, of 0.5, 8.5, 50, and 90) and ethanol using a dual commercial immobilized lipase system (Novozym 435®, Lipozyme TL IM®, Lipozyme RM IM®). Initially, a dual lipase system was used in a single packed-bed reactor (PBR). The blend of Lipozyme TL IM and Novozym 435 had a positive synergistic effect on biodiesel synthesis: an increase of 76% in ethyl ester content was observed after 2 h using refined soybean oil. However, a reduction in the yield was observed in longer reaction times (25 h). Therefore, a continuous reaction system, operated with two different catalytic beds, was investigated. The use of two series reactors allowed high ethyl ester yield (>90%) and high acid conversion (>90%). The reaction using acid soybean oil (50 AV), and Lipozyme RM IM and Novozym 435 reached an ethyl ester content of 95% and 70% after 2 and 25 h, respectively. The results showed that using two different commercial immobilized lipases in intercalated packed-bed reactors enhanced biodiesel synthesis from acid soybean oil. The enzymatic system allows a high fatty acid conversion present in the acidic oil into ethyl ester.

Parametric Sensitivity Analysis of the Separation Process for N-Butanol Production

n-butanol and iso-butanol are commonly produced by the hydrogenation of n-butyraldehyde and iso-butyraldehyde employing the patented copper catalyst accommodated in the reactors in series. The main cause of the lower n-butanol and iso-butanol yield was due to the catalyst blockage rendering a pressure build-up that could lead to a plant shut down. Bypassing the last reactor from the series could be a potential solution to continue running the plant until the next shutdown plan to replace catalyst. The study adopted simulation approach using Aspen Plus V10 to investigate the effect of bypassing the last reactor in the series to the product purity of the downstream separation processes. The iso-butanol and n-butanol with the desired purity were produced from the distillate and bottom product when the column was operated at the RR of 8.03 and DF of 0.328. The reaction conversion of R-102 was varied from 0.1-0.995 but the variation did not significantly change the composition of the main product. Hence, the present study affirmed that the bypassing of third reactor from the reactor train would not affect the product purity of the main product, n-butanol.

활선상태의 전력용 콘덴서 및 직렬 리액터 용량 측정방법

As the static condenser used to improve the power system power factor is installed, a voltage distortion due to inflow of harmonics occurs. In order to reduce harmonics, a series reactor is installed and operated. However, the fault countermeasures due to the burnout of the serial reactor is insufficient. In this paper, a method for measuring the condenser capacity of a live wire status and a series reactor capacity was proposed. In this paper, we propose a method of measuring the capacity of the condenser in the live wire state and the capacity of the series reactor, and provide the basis data for predicting the deterioration state and the degree of performance degradation of the condenser and the series reactor. also, to verify the proposed capacitor capacity measurement method, the capacity measurement method and the effectiveness of the measurement equipment were verified by conducting a demonstration test in connection with the capacity measurement equipment at a demonstration site where L and C values of live wires.

Dynamic response of aerobic granular sludge to feast and famine conditions in plug flow reactors fed with real domestic wastewater

Plug flow reactors (PFRs) approximated by the connection of multiple completely stirred tank reactors (CSTRs) in series were used to achieve continuous flow aerobic granulation in real domestic wastewater. This study revealed, possibly for the first time, that the morphology and characteristics of aerobic granular sludge transformed in the course of a mixed liquor flow through a PFR. The feast zone, located at the front end of the PFR, can quickly develop filamentous structure on the surface of aerobic granular sludge which later disappeared in the famine zone at the back end of the PFR. Detention time from the front to the back end of the PFR was only 6.5 h. During this period the observed sludge morphological change led to sludge settleability fluctuation as much as 66% in zone settling velocity, 16% in specific gravity, and 40% in settled sludge volume. Further analysis revealed these types of sludge morphologies and characteristics were closely related to the specific substrate removal rate profiles of the PFR, i.e., the feast zone might have encouraged filamentous bacteria to extend outward into the bulk solution for soluble substrate, and the famine zone appeared to play an essential role in solidifying the structure of granular sludge structure prior to subjecting it to the gravity selection pressure. It can be inferred from this study that the lack of a famine zone in aerobic granulation reactors can loosen the granule structure and in turn deteriorate granule settleability. For a PFR, a famine zone following the feast zone is essential for maintaining the structural integrity of aerobic granular sludge in a continuous flow wastewater treatment system.

The power of molten salt in methane dry reforming: Conceptual design with a CFD study

A numerical study of the dry reforming of methane is discussed by applying molten salt as the heat source. A tortuous array of reactors, a reactor with frustum shape and a change in the number of reformer beds immersed in the molten salt are studied. The first observation is that the temperature of the heat source does not drop significantly between the inlet and outlet. This property naturally leads to a methane conversion that is proportional to the length when the catalyst volume is fixed. For a tortuous shape with 12 reactors in series, 0.4 m long each, neither the molten salt temperature nor the methane conversion differed significantly between the first and last reactors. Compared to the gas-type heat source, the molten salt turns out to be a very powerful energy carrier. In addition, we briefly discuss the frustum reactor and the variation in the number of reformer beds immersed in molten salt keeping the amount of catalyst fixed. In general, for the frustum reactor the conversion increases as the radius of the feed input becomes smaller. Finally, the CH4 conversion decreases as the number of reformer bed increases for the variation of the number of reformer beds.

Simulating Trambouze reaction for a series reactor

Simulating the existing data on Trambouze reaction is compiled in this article. The objective of the work is to present the change of volumetric flow rate and the inlet concentration of key reactant A in a series continuous stirred tank reactor-plug flow reactor (CSTR-PFR) configurations. The volumetric flow rate does not affect selectivity and conversion for a constant volumetric flow rate operating condition, entering CSTR and PFR, at a specific concentration of reactant. The CSTR-PFR series reactor configuration is proposed for the aim of maximizing the selectivity of the desired product B in comparison to the undesired products X and Y. CSTR as the first reactor is capable to achieve the maximum conversion at the highest selectivity of A. PFR is then proposed after CSTR in a configuration of CSTR-PFR, to allow higher conversion value to be achieved for the resulted outlet stream conditions coming out of the first reactor, CSTR. Both reactors commonly encounter a decrease in the initial concentration of A and an increase to the formation of other products. The CSTR entering volumetric flow rate influence the volume sizes needed in achieving the maximum selectivity and conversion

A Comparative Study of Series Compensation, TCPAR and TCSR FACTS Controllers for Mitigation of Congestion

Power engineers face many challenges while designing and operating a power system. While operating a power grid, mitigation of congestion is one of the major issues. Congestion can take place in one or more transmission lines of a grid when outage of one or more lines takes place due to the fault. Current of a faulty line is transferred to other lines of the grid, and it may result in congestion in some of the healthy lines of a power system. Congestion may cause overloading and overheating of such lines. In this paper, authors have applied different techniques/FACTS Controllers to mitigate congestion in IEEE 5-bus transmission system and presented a comparative study. These are series compensation technique, Thyristor Controlled Phase Angle Regulator (TCPAR) FACTS Controller and Thyristor Controlled Series Reactor (TCSR) FACTS Controller. Analytical study was performed to find the efficacy of each controller, and it has been found that TCSR FACTS Controller provides the desired result.