•Mass transfer behaviour of a rotating tubular packed bed of spheres was studied.•Parameters studied are rotation speed, physical properties of the solution, and bed thickness.•A dimensionless ...equation was obtained and can be used to design and scale up of the reactor.•Various environmental applications of the suggested reactor were discussed.
The mass transfer behaviour of a rotating tubular packed bed of spheres was studied using an electrochemical technique which involved measuring the limiting current of the cathodic reduction of potassium ferricyanide in a large excess of supporting electrolyte. Variables studied were bed rotation speed, physical properties of the solution, and bed thickness (L). The mass transfer coefficient was found to increase with increasing bed rotation speed and decreases with increasing bed thickness. The mass transfer data were correlated by the equation:
Sh=0.126Sc0.33Re0.52LdP-0.8
Importance of the present study in the design and operation of high space – time yield heterogeneous reactors such as electrochemical reactors, catalytic reactors, photocatalytic reactors and immobilized enzyme biochemical reactors suitable for conducting diffusion controlled liquid – solid reactions was highlighted. Advantages of the present reactor in conducting small scale production compared to other reactors were pointed out.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
For the computational support of innovative projects it is necessary to use high-fidelity codes, which must be verified and validated. In Russia, MCU and SERPENT codes are widely used. The MCU code ...was previously chosen as the 'Proryv' project code. Both of these codes are used for calculation of fast reactors, although they are certified for thermal reactors. Therefore, there is a need to show how accurately they allow calculating the characteristics of fast reactors. For cross-verification of these codes, the main characteristics of the benchmark of BN-600 reactor with a hybrid core were calculated: neutron multiplication factors, reactivity coefficients, distribution of energy release over zones, reaction rates. The values of the neutron multiplication factors for various states of the model obtained with the MCU-PTR are systematically higher than the values obtained with the SERPENT 2 (for majority of the states by 0.4%). The values of the reactivity coefficients have the same sign, however, difference between both codes can reach 160% and if compared with the benchmark - 181%. For the majority of reactivity coefficients this compares with the distribution of the results presented in the benchmark. The MCU results are closer to the benchmark than the Serpent ones.
This study was devoted to an exergetically investigation and optimization of the operating conditions of an easy-to-scale-up continuous reactor applied for solketalacetin synthesis as a green fuel ...additive from glycerol-derived monoacetin in the presence of Purolite PD 206 catalyst. The process consisted of two steps, i.e., monoacetin synthesis by glycerol esterification with acetic acid followed by solketalacetin synthesis through reaction of the produced monoacetin with acetone. The main goal of this research was to assess the effects of reaction temperature (20–80 °C), acetone to monoacetin molar ratio (1–5), catalyst loading (0.5–2.5 g), feed flow rate (0.2–1 mL/min), and pressure (0–120 bar) on the exergetic performance parameters of the second stage of the process. Response surface methodology (RSM) was also used to optimize the operating conditions of the reactor by maximizing functional exergetic efficiency (FEE) and minimizing normalized exergy destruction (NED), simultaneously. Overall, feed flow rate had the highest impact on the exergetic performance parameters of the reactor while these indicators were not significantly influenced by pressure. RSM successfully modeled both exergetic parameters with an R2 higher than 0.99. Reaction temperature of 30.8 °C, acetone to monoacetin molar ratio of 2.7, catalyst loading of 1.6 g, feed flow rate of 1.0 mL/min, and pressure of 14.5 bar yielding FEE of 20.39% and NED of 0.90 were determined as the best operating conditions of the reactor. According to the results archived, process yield alone could not stand as the primary objective for making decisions on the optimal operating conditions of the chemical reactors, further highlighting the significance of taking energetic parameters into account in parallel.
•Solketalacetin synthesis from glycerol-derived monoacetin was exergetically studied.•RSM approach satisfactorily modeled the exergetic parameters of the process.•The optimal functional exergetic efficiency of the process was found to be 20.39%.•The optimal normalized exergy destruction of the reactor was determined as 0.90.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
There are around twenty branches in a Nuclear Power Plant that operate to maintain the plant and one of the most important branches of them is 'Safety and Reliability'. Approximately forty percent of ...the investment is paid to ensure the safety and reliability of the plant. Goal of this research work is to estimate reliability of a mechanical system which is chosen as Hydroaccumulator System of VVER type reactor. Getting the reliability, we will be trying to improve the system and enhance its reliability. To do so, firstly, reliability is calculated from a 'prototype reactor's' hot loop which is located at Obninsk Institute for Nuclear Power Engineering (INPE). Thus, calculations were done and its applications being known, then finally these formulas and experiences are being used to calculate and improve the Hydroaccumulator System's design along with its reliability to increase the safety of the NPP.
•Recent challenges in MBR and electrochemical processes are discussed.•New configurations of MBR and electrochemical reactors are examined.•Removal of organics, heavy metal ions, micropollutants, and ...dyes are analyzed.•Low-voltage electrically-enhanced MBRs address the drawbacks of standalone units.•Future prospects are discussed.
Research and development activities on standalone systems of membrane bioreactors and electrochemical reactors for wastewater treatment have been intensified recently. However, several challenges are still being faced during the operation of these reactors. The current challenges associated with the operation of standalone MBR and electrochemical reactors include: membrane fouling in MBR, set-backs from operational errors and conditions, energy consumption in electrochemical systems, high cost requirement, and the need for simplified models. The advantage of this review is to present the most critical challenges and opportunities. These challenges have necessitated the design of MBR derivatives such as anaerobic MBR (AnMBR), osmotic MBR (OMBR), biofilm MBR (BF-MBR), membrane aerated biofilm reactor (MABR), and magnetically-enhanced systems. Likewise, electrochemical reactors with different configurations such as parallel, cylindrical, rotating impeller-electrode, packed bed, and moving particle configurations have emerged. One of the most effective approaches towards reducing energy consumption and membrane fouling rate is the integration of MBR with low-voltage electrochemical processes in an electrically-enhanced membrane bioreactor (eMBR). Meanwhile, research on eMBR modeling and sludge reuse is limited. Future trends should focus on novel/fresh concepts such as electrically-enhanced AnMBRs, electrically-enhanced OMBRs, and coupled systems with microbial fuel cells to further improve energy efficiency and effluent quality.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Innovative reactor concepts show evidence to significantly improve the reaction performance in comparison to conventional reactor systems. To evaluate the reactor concepts, experimental investigation ...of the process behavior is indispensable. In this contribution, a reactor tandem comprising a repeatedly operated semibatch reactor (RSBR) followed by a continuously stirred tank reactor (CSTR) is analyzed for the hydroformylation of 1-dodecene. This reactor tandem was suggested by N. M. Kaiser et al. Ind. Eng. Chem. Res. 2017, 56, 11507–11518 to increase the selectivity toward the linear aldehyde at high conversion levels of 1-dodecene. An additional degree of freedom is gained because of the combined utilization of a batchwise and continuously operated reactor. By using a dynamic process model for planning of the experiments, comparability is ensured with studies of a single CSTR from literature. The experiments confirm an increase in conversion and target product yield applying the RSBR + CSTR tandem, so that up to 90% selectivity is achieved with closed byproduct recycle.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Display omitted
Magnetite particles were synthesized using iron oxide waste by reverse coprecipitation method.
The specific surface area and the crystalline size for magnetite were determined as ...75.77m2g−1 and 11.64nm, respectively.
The maximum phosphate adsorption capacity of magnetite is determined 11.78mgg−1.
The magnetite particles were synthesized by reverse coprecipitation of mill scale (iron oxide waste). The particle characterization was done and confirmed by SEM, EDS, BET, XRF, FTIR and XRD. Scherrer equation determined 11.64nm single crystalline size of the magnetite and the BET surface area was found nearly 75.77m2g−1. The expected stoichiometry (3:4) of Fe:O was confirmed by elemental analysis. The magnetite particles were proven as effective adsorbent for phosphate ions from the contaminated water. The phosphate removal efficiency was inspected with several experimental setups including column reactor fed from top to bottom, from bottom to top and sequencing batch reactor. The maximum P-adsorption capacity of magnetite was determined 11.78mgg−1. The P-carrying adsorbent is regenerated with different concentrations of NaOH and NH4OH solutions for 1, 2 and 5 days. Though both solutions were appeared effective for regeneration of used particles, NaOH was appeared more efficacious than that of NH4OH. The regeneration competence of magnetite particles is also evaluated with repetitive regeneration of used particles with 0.1N NaOH. As compared with initial value, almost 20% of the adsorption capacity was reduced after 12 successive rounds of phosphate adsorption and desorption onto the surface of magnetite. The obtained results have established fine potentiality for the magnetite particles synthesized by reverse coprecipitation to be applied as phosphate adsorbent in wastewater treatment.
Full text
Available for:
GEOZS, IJS, IMTLJ, IZUM, KILJ, KISLJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this work, a high-performance catalytic membrane, composed of ultrasmall gold nanoclusters (AuNCs) and high aspect-ratio carbon nanotubes (CNTs), was designed for the continuous-flow catalytic ...reactions. In this hybrid catalytic membrane, the Au core of the NCs serves as high-performance catalyst, and the ligand of the NCs plays two key roles: (1) as a well-defined surfactant assembly to effectively dissolve CNTs in aqueous solution and (2) as an efficient protecting ligand for Au core to avoid agglomeration. Due to the above-mentioned features, a homogeneous 3D self-support catalytic membrane can be readily fabricated by vacuum filtration of the hybrid AuNCs/CNTs. The catalytic activity of the as-designed catalytic membrane was evaluated using 4-nitrophenol hydrogenation as a model catalytic reaction. The data suggest that the continuous flow catalytic reactor could achieve complete conversion of the substrate (i.e., 4-nitrophenol) within a single flow through the membrane with a hydraulic residence time (τ) of 3.0 s. The catalytic membrane also showed enhanced catalytic kinetics as compared to the conventional batch reactor due to the convectively enhanced mass transfer. In addition, three important parameters, including the Au loading amount, substrate concentration, and flow rate, were identified as key factors that could affect the performance of the catalytic membrane.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Display omitted
•Highly conductive open-cell foams enhance heat transfer in packed-bed FTS reactors.•Packed-foams enable running the FTS under severe conditions with excellent T-control.•Thermal ...runaway occurs under mild conditions in conventional packed-bed reactor.•Packed-foams provide an innovative solution to increase the catalyst inventory.•Conductive packed foams are an efficient strategy for compact tubular reactor units.
The low-temperature Fischer-Tropsch synthesis is a strongly exothermic process wherein the temperature control is a crucial issue. In this work, we demonstrate experimentally for the first time the adoption of a Fischer-Tropsch tubular reactor (2.78 cm I.D.) loaded with a highly conductive open-cell aluminum foam packed with catalyst microspheres to enhance heat exchange. Accordingly, the performances of a highly active Co/Pt/Al2O3 catalyst packed into the metallic structure are assessed at industrially relevant operating conditions and compared with those obtained in a conventional randomly packed fixed-bed reactor. The structured catalyst reaches outstanding performances (duties in excess of 1300 kW/m3 with CO conversions >65%) with a remarkable temperature control. Almost flat axial temperature profiles are measured along the catalytic bed even under the most severe process conditions, showing the excellent ability of the “highly conductive packed-foam reactor” concept to manage the strong exothermicity of the reaction. In contrast, when the same experiment is carried out over the same Co/Pt/Al2O3 catalyst just randomly packed in the reactor, an abrupt increase of the catalyst temperature occurs already at low temperature, eventually leading to thermal runaway. The results herein collected prove the potential of conductive metal foams as enhanced reactor internals for the intensification of strongly exothermic processes in nonadiabatic tubular reactors. Furthermore, the “packed-foam” configuration also demonstrates the possibility to overcome the inherently limited catalyst inventory of the washcoated conductive structured reactors proposed so far, thus boosting the productivity per reactor volume.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
A CSTR reactor was operated for 30 days. It was fed with raw cheese whey with an organic loading rate of 30 gCOD/Ld. Hydrogen production varied significantly with a maximum of 0.9 LH2/Ld and ...decreased after 17 days of operation. The causes of production instability were analysed using different microbiological tools. It was concluded that this decrease was not due to the incapacity to select hydrogen-producing organisms, as shown by the persistence of the Fe-hydrogenase genes in the reactor. Using a molar balance, it was estimated that more than 30% of the acetic production can be due to the homoacetogenesis pathway, although genes from homoacetogenic microorganisms were detected at a very low concentration. The different effects of enhancement and inhibition of hydrogen production by the lactic acid bacteria and their high abundance variation could explain the instability of hydrogen production in this reactor.
•A CSTR reactor fed with raw cheese whey was operated for 30 days and a very variable hydrogen production was obtained.•A maximum of 0.9 LH2/Ld was obtained and decreased after 17 days of operation.•Fe-hydrogenase genes persist in the reactor so, this was not the cause of the decrease in H2 production.•More than 30% of the acetic production could be due to the homoacetogenesis pathway.•High abundance of lactic acid bacteria could explain the instability of hydrogen production in this reactor.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
PDF
