Channel Reactor Research Articles

Microfluidic cultivation and analysis of productive biofilms.

We here report the application of a machine-based microfluidic biofilm cultivation and analysis platform for studying the performance of biocatalytically active biofilms. By using robotic sampling, we succeeded in spatially resolving the productivity of three microfluidic reactors containing biocatalytically active biofilms that inducibly overexpress recombinant enzymes. Escherichia coli biofilms expressing two stereoselective oxidoreductases, the (R)-selective alcohol dehydrogenase LbADH and the (S)-selective ketoreductase Gre2p, as well as the phenolic acid decarboxylase EsPAD were used. The excellent reproducibility of the cultivation and analysis methods observed for all three systems underlines the usefulness of the new technical platform for the investigation of biofilms. In addition, we demonstrated that the analytical platform also opens up new opportunities to perform in-depth spatially resolved studies on the biomass growth in a reactor channel and its biochemical productivity. Since the platform not only offers the detailed biochemical characterization but also broad capabilities for the morphological study of living biofilms, we believe that our approach can also be performed on many other natural and artificial biofilms to systematically investigate a wide range of process parameters in a highly parallel manner using miniaturized model systems, thus advancing the harnessing of microbial communities for technical purposes.

EXPERIMENTAL TECHNIQUES

-There may be several aspects in any experiment conducted to achieve a well defined goal. It is considered more useful to cite number of experimental techniques employed in a single large scale experiment. For the rewetting of vertical cylindrical surface under bottom flooding conditions, it is reasonable to assume uniformity of temperature in the peripheral coordinate. Code RAMM (Rewetting Analysis using Moving Mesh) has been developed by the author of this paper [1] to calculate rewetting velocity. Experiments were also conducted for determination of rewetting velocities [2], the rewetting velocity in mm/s is100.0 by [3]; 33.3 by [4] ;51.0 by [5]. This paper is aimed to cover experimental techniques employed in the determination of rewetting velocity (RV) in Nuclear Reactor Channel under the scenario of Loss Of Coolant Accident (LOCA). For determining RV, many experimental methodology and techniques were employed. Experimental simulation of nuclear fuel pin clad named as fuel pin simulator, was carried out by taking hot vertical annular channel where rewetting of outer surface was studied. Experimental rewetting studies requires multidisciplinary approach namely (i) selection of material for the fuel pin simulator. (ii) Installation of thermocouple wires at many locations into wall of a long and narrow tube (iii) Electrical resistance Joules heating of S. S. tube of 3.03m long, 0.015m outer and 0.012m inner diameters (iv) selection of power source for heating (v) Instrumentation required to capture parameters and (vi) Programming and connecting the Data Acquisition System (DAS) for recording the temperature transients.

Continuous Preparation of Precious Metal Nanoparticles from Plant Biomass and CFD Simulation

Precious metal nanomaterials have broad application prospects in many fields. However, most of the existing synthesis processes of precious metal nanomaterials are carried out in a batch reactor. Recently, the technology of batch preparation of noble metal nanoparticles by chemical method has become mature, but with the increase of reactor volume, the problems of heat and mass transfer of the system are prominent. In this paper, the technology of reducing plant biomass with green characteristics to prepare precious metal nanoparticles was introduced into the continuous operation of micro channel reactor and reactor to investigate the influence of reactor structure parameters and reaction conditions on the formation and particle size distribution of precious metal nanoparticles, and combined with computational fluid dynamics (CFD) simulation technology to explore its influence mechanism. In this paper, it is found that the AgNPs (4.7 ± 1.9 nm) prepared by ETFE tube has a larger average particle size and a wider particle size distribution than the AgNPs (4.24 ± 0.9 nm) prepared by PTFE tube.

Biogenic sulfur attack in a reinforced concrete sewage treatment plant. Re-visited mechanism and rehabilitation proposal

Sewage treatment plants are examples of structures subjected to highly aggressive industrial environments. Given this, the objective of the present work is to evaluate the degree of degradation of the concrete structure of a sewage treatment plant located in Curitiba, Brazil. This plant was exposed to an environment within the process of wastewater treatment for nearly 20 years. Samples were collected from four slabs and four walls of the drainage channels of the sewage treatment plant reactor. Tests of the corrosion potential of the reinforcement, depth of neutralization, SEM/EDS, XRD, optical microscopy and uniaxial compressive strength were performed. Several exposed and heavily corroded reinforcement extensions were identified. The pH inside the slabs was found to be alkaline (over 10). With the analysis of SEM/EDS and XRD, it was possible to identify the predominance of gypsum in samples of the external part of the core and surface of the channel walls. The mechanical properties were preserved, with compressive strength even greater than that observed in the last inspection, which was 6 years ago. Finally, the results indicate that the attack on concrete initially occurred on the surface, advancing in depth over time. This attack was caused by the decalcification of C-S-H and resulted in the formation of gypsum as the final product of the degradation mechanism.

Non-equilibrium solvent extraction in milliflow reactors: Precious and base metal separations with undiluted ionic liquids

Milliflow devices operating under slug flow (Taylor-flow) conditions provide an efficient mass transfer, a highly uniform droplet morphology and a narrow residence time distribution i.e. characteristics which are excellent for the performance of reactions under kinetic control. Milliflow devices have also been proposed in combination with ionic liquids, due to their ability to intensify the solvent use of these rather expensive and viscous liquids. In present research, the solvent extraction separation of a mixture of Au(III), Pd(II), Cu(II) and Fe(III) was studied using the chloride and bromide forms of the undiluted quaternary ammonium ionic liquid Aliquat 336 in a slug flow reactor channel with an internal diameter of 1.0 mm. The extraction of Au(III) and Pd(II) was found to be faster than that of Cu(II) and Fe(III), allowing the precious/base metal separation to be improved by modification of the contact time between both phases. An apparent correlation between the observed extraction rates and the equilibrium distribution ratio D was found. The most significant separation improvement was achieved at those conditions where the equilibrium separation was best i.e. low halide and metal concentrations and low organic-to-aqueous flow rate ratios. At a residence time of 25 s, quantitative Au(III) and Pd(II) recovery was achieved and decontamination factors increased by a factor up to 2, which corresponds to an increase in product purity of up to 14%. Upon substituting the chloride system for a bromide extraction medium, similar observations were made, except for a reversed Cu(II)/Fe(III) selectivity. Experiments were also conducted on the separation of Pt(IV), Pd(II) and Rh(III), where a reduced Rh(III) extraction rate was observed, allowing to suppress its co-extraction by up to 20%. A hydrodynamic analysis of the obtained flow regime of the ionic liquids revealed a stable and uniform slug flow characterized by a decreasing plug length and width with increasing flow rates. A comparison of the applied and observed phase ratio revealed a stagnant ionic liquid excess (i.e. hold-up) inside the reactor of up to 40% which effectively reduced the reactor diameter and consequently plug residence time.

Reconstructing the conductivity profile of a graphite block using inductance spectroscopy with data-driven techniques

The radial depth profile of the electrical conductivity of the graphite channels in the UK's advanced gas-cooled reactors (AGRs) can be reconstructed and estimated by solving a non-linear optimisation problem using the mutual inductance spectra of a set of coils. This process is slow, as it requires many iterations of a forward solver. Alternatively, a data-driven approach can be used to provide an initial estimate for the optimisation algorithm, reducing the amount of time it takes to solve the ill-posed inverse problem. Two data-driven approaches are compared: multi-variable polynomial regression (MVPR) and a convolutional neural network (CNN). The training data are generated using a finite element (FE) model and superimposed on a noise floor in the interval [20, 60] dB of the weakest amplitude point in the corresponding spectrum. A total of 5000 simulated datasets are generated for training. The results on smoothed test data show that the two models have a comparable mean percentage error norm of 17.8% for the convolutional neural network and 17.3% for multivariable polynomial regression. A further 500 unsmoothed profiles are tested in order to assess the performance of each algorithm on conductivity distributions where the conductivity of each layer is independent of another. The performance of both algorithms is then assessed on reactor-type test data. The results show that the two data-driven algorithms have a comparable performance when estimating the electrical conductivity depth profile of a typical reactor-type distribution, as well as vast deviations. More generally, it is thought that data-driven approaches for depth profiling of some electromagnetic quantity have the potential to be applied to other ill-posed inverse problems where speed is a priority.

Sensitivity Studies to Assess the Impact of Geometry and Operating/Boundary Condition Perturbations on Thermal-Hydraulic Behavior of Advanced Fuel Channels in Pressure Tube Heavy Water Reactors with Uranium and Thorium-Based Fuels

This paper reports the results of subchannel thermal-hydraulic studies (using the ASSERT-PV code) of the effects of variations and uncertainties in operating/boundary conditions and geometry on the predictions of pressure drop, dryout power, and dryout location for two types of advanced, nonconventional fuels in a pressure tube heavy water reactor (PT-HWR) fuel channel with 12 fuel bundles. The fuel bundles tested include a 37-element fuel bundle made with SEUO2 (1.2 wt% 235U/U), with a central fuel element made of ThO2, and 35-element fuel bundle made with (LEU,Th)O2, using 5 wt% 235U/U low-enriched uranium (LEU), 50 wt% LEUO2, and 50 wt% ThO2. Results indicate that for a range of flow conditions, the dryout power for the thorium-based 35-element fuel bundle is 10% to 26% higher than that for the uranium-based 37-element fuel bundle. Variation/uncertainty in the pressure tube diameter has the most significant impact on the pressure drop, dryout power, and dryout location. Results from these studies may have implications for the operations of PT-HWRs with advanced fuels, and further modifications may be desirable to further enhance thermal-hydraulic margins.

Corrosion tests in heavy water of aluminium alloys for experimental channels of the PIK reactor

Corrosion tests in heavy water of aluminium alloys for experimental channels of the PIK reactor

An insight into the heat-management for the CO2 methanation based on free convection

This article presents a novel heat-management approach for CO2 valorization to synthetic natural gas based on free convection to the environment, without requirements of heat-exchange services. With this aim, a reactor channel was built (d = 4.6 mm, L = 250 mm) and tested at different conditions of inlet temperatures, gas hourly space velocities and pressures using an active nickel/ceria-based catalyst. After experimentation, a CFD model was developed, validated and employed for an efficient sensitive analysis of the most suitable reaction conditions. The simulation criteria were obtaining high CO2 conversion level and restricting overheating to avoid catalyst and reactor degradation. Then, the optimal conditions found by CFD modelling were successfully validated at lab-scale. The CO2 conversion level experimentally obtained was 93%, by using a decreasing temperature profile in the range of 830–495 K, operating at a pressure of 5 atm and a gas hourly space velocity of 11,520 h−1. The proposed reactor configuration guarantees an efficient heat management along the reactor channel by using feasible conditions of pressure, temperature and flowrate for its implementation in small-scale applications, where the use of the exothermic heat is less profitable.

Spatially and Temporally Resolved Measurements of NO Adsorption/Desorption over NOx-Storage Catalyst.

The two‐dimensional (2D) temporal evolution of the NO‐concentration over a NOx‐storage catalyst is investigated in situ with planar laser‐induced fluorescence (PLIF) in an optically accessible parallel wall channel reactor. Signal accumulated phase‐correlated 2D‐recordings of repetitive adsorption/desorption cycles are obtained by synchronizing the switching of the NO gas flow (on/off) with the laser and detection system, thereby significantly increasing the signal‐to‐noise ratio. The gas compositions at the reactor outlet are additionally monitored by ex‐situ analytics. The impacts of varying feed concentration, temperature and flow velocities are investigated in an unsteady state. Transient kinetics and the mass transfer limitations can be interpreted in terms of the NO concentration gradient changes. The technique presented here is a very useful tool to investigate the interaction between surface kinetics and the surrounding gas flow, especially for transient catalytic processes.

Intensification of ozone generation and degradation of azo dye in non-thermal hybrid corona-DBD plasma micro-reactor

A novel corona-dielectric barrier discharge hybrid non-thermal plasma micro-reactor was investigated for ozone generation and pollutant degradation. It was hypothesized that creating a submicron channel inside the micro-reactor would increase ozone generation efficiency. Therefore, the plasma micro-reactor was packed with dielectric glass beads. The plasma micro-reactor operating conditions were investigated for ozone formation. The efficiency of the empty channel plasma reactor was compared with the packed-bed plasma reactor which was 24 % higher than the former at optimized conditions-5 kV peak voltage, 36 mA peak current, 26.02 kHz frequency, 1 Lmin−1 air flow rate, and 4 cm electrode length. The performance of the reactor was evaluated for the degradation of Reactive black-5. The plasma micro-reactor operating conditions and the dye operational parameters- pH of the solution, initial dye concentration, and volume of solution were also investigated to see the efficiency of reactive black-5 removal in the plasma reactor. The dye degradation efficiency increased by 50 % in the packed-bed plasma micro-reactor as compared to the empty channel reactor. In the empty channel reactor, 98 % reactive-black-5 was removed with 87 % COD reduction in 16 min, and in the packed-bed reactor, 98.3 % was removed with 89 % COD reduction in 8 min of the plasma treatment.

Facile High Throughput Wet-Chemical Synthesis Approach Using a Microfluidic-Based Composition and Temperature Controlling Platform.

The wet-chemical technique has been widely applied in material synthesis. In recent years, high throughput (HT) technique has shown its potential in parallel synthesis and the investigation of synthesis parameters. However, traditional ways of HT parallel synthesis require costly equipment and complex operating procedures, restricting their further applications. In this paper, we prepared a cost-effective and timesaving microfluidic-based composition and temperature controlling platform to carry out HT wet-chemical synthesis in a facile and automated workflow. The platform uses a microfluidic chip to generate 20–level concentration gradients of the two reagents and uses 100–channel reactor arrays for wet-chemical synthesis with 5–level temperature gradients. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were applied to characterize Co–Ni bimetallic powder materials synthesized under 100 different reaction conditions. X-ray photoelectron spectroscopy (XPS) was conducted to confirm the oxidation state of the products. This platform not only enables one-step determination of the minimum reaction temperature required for a wet-chemical system but also provides a significant increase in efficiency compared with the traditional wet-chemical approach. The microfluidic-based composition and temperature controlling platform shows promise in facile, efficient, and low-cost HT wet-chemical synthesis of materials.

The experimental and numerical study of the vertical gas movement in the cylindrical channel

The detailed experimental and theoretical studies of the vertical gas movement through a layer of liquid (water, molten tin) placed in a cylindrical channel (10 cm diameter) were performed. It was shown that during the gas passage through a single opening (the diameter of 8 mm) its movement at a small flow takes place as single bubbles, whose diameter becomes greater as they move towards the free surface of the liquid. Increase in the diameter at identical gas and liquid temperatures is explained by the decreasing liquid pressure in the upstream direction. If the gas temperature is lower than the liquid temperature, the diameter of bubbles increases also due to gas heating, thus resulting in the increase of its pressure in the bubble. As the gas flow increases, the number of bubbles which then merge into the uniform mass in the upper part of the channel without reducing their diameter, becomes greater. When passing the gas though the diaphragm with a high number of openings (80 openings of 1 mm in diameter), the amount of bubbles becomes higher, however their diameter in the upper part of the channel practically does not increase. When using multiple strainer diaphragms arranged at small distances from each other along the channel height, the diameters of bubbles become considerably reduced, which is connected with their periodic fragmentation when passing through each subsequent strainer. Furthermore, the bubbles get the smallest diameter when they pass through the last strainer, after which the liquid and the gas make a uniform gas and liquid emulsion in the form of a mist. The analysis of the results of air passage thought the molten tin (at a temperature of 300°C) allows concluding on considerable increase in the bubble diameter as compared to the experiments with water, which is explained by gas heating in the bubbles due to a sufficiently high temperature of tin and, as a result, the increase of pressure in them. Experimental studies applicable to small-diameter cylindrical channel (2 cm) were also performed. Their analysis allows concluding about a considerable divergence of the obtained results as compared to the greater diameter channel (10 cm) at the same gas flow. For the small-diameter channel, numerical calculations were also performed (e.g. tin) in a vertical cylindrical channel (reactor) [5 – 8]. The amount of hydrogen obtained at the reactor outlet depends on the intensity of methane heating to the pyrolysis temperature. It is known that methane passes through the molten tin in the form of bubbles, whose diameter increases as they move towards the upper part of the reactor, which is connected with the reduction of upstream pressure of liquid metal as well as the increase of gas pressure in bubbles resulted from its heating. The increase in the bubble diameter makes it heating to the pyrolysis temperature difficult as a result of low heat conductivity of methane. In this regard, measures should be taken to decrease their diameter.

Mathematical model of the distribution of the coolant flow rate in the group distribution header and its use to determine the flow rate in the RBMK reactor channel

The paper proposes an elementary mathematical model of the distribution of coolant flows through water communications in the group distributing header (GDH) of a power unit with an RBMK reactor. This model used to determine the flow rate in the channel with a “forbidden” flow meter. An equation is given based on the mass balance of the coolant in the allocated volume. The results of the solution are used to construct an algorithm for determining the flow rate of the coolant in the channel. The results of the application of the technique on the measurement data from the power unit are presented. It is shown that the relative discrepancy with the measured value of the flow rate at a constant position of the flow control valve is on the order of several percent.

Effectiveness of using two-stage anaerobic digestion to recover bio-energy from high strength palm oil mill effluents with simultaneous treatment

This study aimed to investigate the biohydrogen and biomethane potential of palm oil mill effluent (POME) in a two-stage anaerobic digestion (AD) system under thermophilic (55 ± 3 °C) and mesophilic (30 ± 3 °C) conditions, respectively. Among the initial loadings of 0.5 g-COD, 1.0 g-COD, or 1.5 g-COD, the best production potentials of 106.13 mL-H2/g-COD and 334.56 m L-CH4/g-CODadded, corresponding to the total energy production of 13.61 kJ/g-CODadded, were obtained from POME with an initial 0.5 g-COD loading. The investigation also revealed that the energy yield (CH4+H2) achieved from two-stage AD was approximately 38.95 % higher than single-stage anaerobic digestion (single-stage AD), where only methane energy carrier was produced. Continuous hydrogen and methane production were subsequently performed in a series of continuous stirred tank reactor (CSTR) and anaerobic horizontal baffled channel (AHBC) reactor to treat POME without external supplement. The results revealed that the highest hydrogen yield of 86 m L-H2/g-CODadded was generated at 3-day HRT, while the highest methane production was obtained from HRT over 35 days with a yield of 250.33 m L-CH4/g-CODadded. Additionally, the overall COD removal in the continuous process was approximately 66.27 %. As a highly efficient organic matter removal and higher energy recovery, the continuous two-stage AD can be further developed to industrial-scale mixed hydrogen and methane production from POME.

A microfluidic reactor application for the continuous-flow photocatalytic selective synthesis of aromatic aldehydes

Benzyl alcohol and a set of para-substituted derivatives (–NO2, –Cl, −CH3, −OCH3 and −OH) were converted to the corresponding aldehydes in a commercial continuous-flow microfluidic reactor. Due to the dimension and the rigidity of the commercial microfluidic reactor channels, a stable suspension with few-layer graphitic carbon nitride nanoparticles (GCN-TS) was used to avoid the blockage of the photocatalyst in the channels of the reactor. Preliminary photocatalytic batch experiments revealed that different reaction yields were obtained depending on the aromatic ring activating/deactivating nature of the substituent groups. Regarding the experiments under continuous-flow, the highest aldehyde production was obtained for the reactions with 4-methoxybenzyl alcohol as starting molecule, corresponding to 0.19 mM at a retention time of merely 0.75 min. The results show the possibility of employing microfluidic reactors for the selective photocatalytic conversion of aromatic alcohols for both process intensification and screening applications due to the drastic decrease of reaction time.

Preparation and Characterization of Nb-1Zr-0.1C Alloy Suitable for Liquid Metal Coolant Channels of High Temperature Reactors

Abstract A novel process comprising of aluminothermic coreduction of mixed oxides followed by arc and electron beam melt refining was developed for preparation of Nb-1Zr-0.1C alloy. The parameters of the process were optimized by considering the thermodynamic (heat) and mass balance phenomenon. The ingots of the homogenized alloy produced after electron beam melt consolidation were further extruded into tubes. The alloy was vacuum annealed at 1350–1800 °C to study the stability of Nb2C and Nb(Zr)C carbide precipitates in the microstructure. Compression creep tests conducted at 900 and 1000 °C revealed a stress exponent value of 2 and activation energy of 508 kJ/mol. NbSi2-based coatings were developed on the Nb-1Zr-0.1C alloy tubes using pack siliconizing process. The coated alloy was tested for oxidation at 1250 °C, and corrosion in liquid lead-bismuth eutectic (LBE) alloy at 875 °C for prolonged duration. The silicide-coated alloy showed superior oxidation and LBE corrosion resistance at high temperatures. The alloy was found to be a promising material for coolant channels of high temperature reactors.

Characteristic of methanol steam reforming in fan-shaped channel reactor for efficient hydrogen production

ABSTRACT On-board methanol steam reforming fan-shaped channel micro-reactor heated by engine exhaust (simulated by hot wind) for hydrogen production was designed and analyzed in this study. Effects of the reactor material and structural parameters were investigated. The optimal size of reactor structure, using the stainless steel as the reactor material, are predicted to be 26 mm and 35 mm for the hot wind side radius and total radius, respectively. Additionally, the optimal angle of the fan shaped reactor unit is 10°, while the thickness of the intermediate between the hot wind and reaction sides as well as side and top walls are 1 mm. Under these structure parameters, the methanol conversion rate is 73.48%, the engine exhaust heat efficiency is 36.50%, and the hydrogen production rate of the whole reactor is 78439.30 mm3/s. These results can be utilized as reference for the comprehensive utilization of engine exhaust heat and engine hydrogen-mixed combustion.

Monitoring stratification of anode biofilms in bioelectrochemical laminar flow reactors using flow cytometry

A laminar flow bioelectrochemical systems (BES) was designed and benchmarked using microbial anodes dominated with Geobacter spp. The reactor architecture was based on modeled flow fields, the resulting structure was 3D printed and used for BES manufacturing. Stratification of the substrate availability within the reactor channels led to heterogeneous biomass distribution, with the maximum biomass found mainly in the initial/middle channels. The anode performance was assessed for different hydraulic retention times while coulombic efficiencies of up to 100% (including also hydrogen recycling from the cathode) and current densities of up to 75 μA cm−2 at an anode surface to volume ratio of 1770 cm2 L−1 after 35 days were achieved. This low current density can be clearly attributed to the heterogeneous distributions of biomass and the stratification of the microbial community structure. Further, it was shown that time and space resolved analysis of the reactor microbiomes per channel is feasible using flow cytometry.

Linking performance and microbial ecology in a biological sulphate reducing reactor system with biomass retention developed for the treatment of acid rock drainage

Biological sulphate reduction (BSR) represents a sustainable process option for the remediation of low-flow acid rock drainage (ARD) effluents. The linear flow channel reactor (LFCR) was developed as a semi-passive bioreactor facilitating sulphate reduction and sulphide removal, through the action of sulphate-reducing bacterial (SRB) and sulphur oxidising bacterial consortia, within a single reactor unit. A consensus on key microorganism(s) required within BSR bioreactor consortia for successful operation is still to be reached. In this study next-generation gene amplicon sequencing was used to assess the microbial communities within an anaerobic LFCR supplemented with acetate as the primary electron donor. The performance of this reactor was monitored for over 1000 days throughout a hydraulic retention time (HRT) study and the composition of the microbial communities within this system assessed at several time points. The reactor exhibited a maximum volumetric sulphate reduction rate of 17.8 mg/L.h at a dilution rate of 0.042 h−1. Microbial biofilm communities formed on the incorporated carbon microfibres, as well as planktonic communities showed marked changes in community composition over the course of the study. The presence and shifting abundance of SRBs in the biofilm and planktonic communities that had been identified in previous studies to dominate under defined operating conditions allowed the functional role of individual microorganisms to be elucidated. A Desulfatitalea, whose presence had been previously linked to sulphate scavenging at low sulphate concentrations, was found at high abundance at long residence times. Conversely, a Desulfobacter which was previously shown to dominate under conditions of high sulphate loadings and associated high reaction rates and high substrate concentrations was found at a high dilution rate and low residence time in both the planktonic and biofilm communities. Assessment of the microbial communities and overlaying of performance within this system has enabled us to provide a preliminary link between the structure of the microbial community and the performance of this BSR reactor system. These findings provide considerable insights into the improved design and operation of acetate-supplemented BSR reactors to ensure successful performance.