Reactor Mode Research Articles

Root cause analysis for shunt reactor failure in 500 kV power system

Error has been long recognized as ubiquitous to the practice of electrical engineering for failure analysis, however, the correct methodology for decision science is necessary, especially with more statistical data analysis, in this research a new methodology proposal for update the international standard IEC 60076, by using the root cause analysis, with traditional methods, principal components analysis, data mining and causal map, it is possible to eliminate the error, in this analysis an update for the standards have been discovered, they need to improve to avoid critical failures in the power system, for the shunt reactors. This research explores the failure mode and root cause analysis of shunt reactors in high voltage through examination of the design and implementation in Latin American. The case study has been evaluated for a shunt reactor in the 500 kV power system, and a discussion is considered for 279 shunt reactors, they were located in Latin America, finally the principal component analysis, cluster and causal mapping for the strategy correction is done. In this research, a real case study has discovered with twelve failures modes and fourteen activities to avoid the design and construction mistakes, they should be considered to improve the international standards in the design of this important equipment for the power system. Furthermore, if in the analysis, the shunt reactor is full loading, all the fatigue fractures occur for a vibration in the shunt reactor with a partial discharge in the bushing connection and the spring closure of the equipotential devices. It results in a larger investigation with the new proposal, it is the root cause of one of the most critical points. These results indicated that re-evaluating shunt reactor design to ensure an optimal behavior with the components for this equipment in a full load stage.

Catalytic Performance of NiMoS Supported on (Zr)SBA-15 for Hydrodesulfurization of Diesel: Insight into a One-Step Calcination and Reduction Strategy during Sulfidation

We report, herein, the catalytic efficiency and activity of a facilely synthesized sulfided NiMo hydrodesulfurization (HDS) catalyst supported on (Zr)-SBA-15 by one-step calcination and reduction heat treatment prior to sulfidation. Zr-SBA-15-Mo is prepared by a direct synthesis approach, followed by the confinement of Ni into the as-synthesized Zr-SBA-15-Mo without calcination, to generate more dispersion and active sites of metal oxides for an efficient sulfidation process. The HDS performance of these catalysts was evaluated and compared to that of the catalysts prepared by the sequential calcination and reduction approach prior to sulfidation for HDS of dibenzothiophene (DBT) and dimethyldibenzothiophene (DMDBT) in commercial diesel at 350 °C in batch reactor mode. Structural and morphological properties related to catalytic activity have been obtained by means of spectroscopy (X-ray diffraction (XRD), Raman, pyridine-Fourier transform infrared (FTIR), temperature-programmed desorption (TPD), microsco...

Modification of a tri-reforming reactor based on the feeding policy to couple with methanol and GTL units

The main idea of this research is the modification of methane tri-reforming reactor to increase syngas production capacity. Since methane tri-reforming is an integration of steam reforming, dry reforming, and partial oxidation, the feeding policy is a key solution to shift reaction network toward the desired condition. In this regard, the conventional fixed bed reactor is divided into three equal beds in series, and the optimal distribution of steam, carbon dioxide and oxygen between beds is calculated to maximize hydrogen production. The conventional and proposed configurations are heterogeneously modeled based on the mass and energy conservation laws at steady state condition. Then, the accuracy of the developed model and considered assumptions is proved. To calculate the optimal condition of the proposed multi-bed tri-reformer, a single objective optimization problem is formulated considering process limitations. Based on the optimization results steam and carbon dioxide injection between beds increases hydrogen production about 2.93% at the same catalyst loading. The main advantages of the proposed configuration are higher hydrogen production, adequate hydrogen to carbon monoxide ratio, and higher carbon dioxide conversion. The results shows that carbon dioxide conversion in the proposed multi-bed configuration is about 16%.

Diversity and metabolism of xylose and glucose fermenting microbial communities in sequencing batch or continuous culturing.

A mechanistic understanding of microbial community establishment and product formation in open fermentative systems can aid the development of bioprocesses utilising organic waste. Kinetically, a single rate-limiting substrate is expected to result in one dominant species. Four enrichment cultures were operated to ferment either xylose or glucose in a sequencing batch reactor (SBR) or a continuous-flow stirred tank reactor (CSTR) mode. The combination of 16S rRNA gene-based analysis and fluorescence in situ hybridisation revealed no complete dominance of one species in the community. The glucose-fed and xylose-fed SBR enrichments were dominated >80% by one species. Enterobacteriaceae dominated the SBRs enrichments, with Citrobacter freundii dominant for xylose and Enterobacter cloacae for glucose. Clostridium, Enterobacteriaceae and Lachnospiraceae affiliates dominated the CSTRs enrichments. Independent of substrate, SBR communities displayed 2-3times higher biomass-specific rate of substrate uptake (qsmax) and 50% lower biomass yield on ATP, to CSTR communities. Butyrate production was linked to dominance of Clostridium and low qsmax (1.06Cmols Cmolx-1 h-1), while acetate and ethanol production was linked to dominance of Enterobacteriaceae and Lachnospiraceae and high qsmax (1.72Cmols Cmolx-1 h-1 and higher). Overall, more diversity than expected through competition was observed, indicating mutualistic mechanisms might shape microbial diversity.

Development of a 5kWth internally circulating fluidized bed reactor containing quartz sand for continuously-fed coal-coke gasification and a beam-down solar concentrating system

The operational mode of a batch-type fluidized bed reactor containing quartz sand and coal-coke particles was tested under xenon arc lamp (Xe-light) illumination to develop processes for the continuous feeding and gasification of coke particles in the quartz sand fluidized bed. This paper focuses on the fluidizing, heating, and steam gasification performances of a windowed internally circulating fluidized bed reactor. The operational modes explored in this study were: (1) elevated temperature processes associated with the use of Xe-light radiation to reach gasification temperatures, and, (2) the gasification process driving steam gasification at high-temperatures, working with stream gasification of continuously-fed coal-coke. The gasification performances were used to evaluate the performance of quartz sand as a thermal-transfer/sensible heat-storage medium. The peak rate of gas production was greatly enhanced for the high volume fraction of coal-coke. In addition, the light-to-energy conversion rate of 11.0–13.2% and carbon conversion rate up to 80% were reached in the simplified distributor structure of gasification reactor.

Hydrothermal Liquefaction Studies for Desalination Membrane Management

Background: Membrane technology using Spiral Wound Reverse Osmosis (SWRO) is long established as a large scale industrial membrane process for desalination. Membranes need to be managed after their life cycle. Aim: The present study involves the AOP studies for liquefaction and depolymerization of desalination membranes under batch reactor mode. Method: Advanced Oxidation Process (AOP) based hydrothermal liquefaction process techniques have been carried out for Ultra Filtration (UF) membranes; permeate spacer and RO membranes at different stirring rates, temperatures, concentrations and reaction durations. Result: The comparison of process techniques under dynamic conditions for liquefaction and depolymerization of permeate spacer/UF & RO membranes are presented with an objective for facilitating chemical recycling or disposal of the same. Conclusion: The synergistic effect of radiation with concentration of reaction media is established. Keywords: Desalination membranes, depolymerization, advanced oxidation process, liquefaction, chemical recycling, ultra filtration.

Hydrogenation of non-polar Fraction of Bio-oil from Co-pyrolysis of Corn Cobs and Polypropylene for Bio-diesel Production

Bio-diesel was synthesized by hydrogenating the non-polar fraction of the bio-oil produced from the co-pyrolysis between corncobs and polypropylene. Co-pyrolysis of corn cobs and polypropylene was conducted in a stirred tank reactor at heating rate of 5°C/min and maximum temperature of 500°C to attain synergetic effect in non-polar fraction yield where polypropylene served as a hydrogen donor and oxygen sequester so that the oxygenate content in the biofuel product reduced. Stirred tank reactor configuration allowed phase separation between non-polar and polar (oxygenate) compounds in the bio-oil. Hydrogenation reaction of the separated non-polar phase, which contained alkenes, was carried out in a pressured stirred tank reactor using a NiMo/C catalyst in order to reduce the alkene content in the bio-oil. The aim of the present work is to reduce the alkene content in the separated non-polar fraction of bio-oil by catalytic hydrogenation to obtain biofuel with low alkene content and viscosity approaching to that of diesel fuel. To quantify effect of the pressure on the alkene composition, the experiment was done at H2 initial pressures of 4, 7, 10, and 13 bar and at corresponding saturation temperatures of octane. The biofuel products were characterized using GC-MS, LC-MS, FTIR spectroscopy, H-NMR, Higher heating values (HHV) and viscometer for comparison with those of commercial diesel fuel. Analysis of the lower molecular weight fractions of biofuels by GC-MS found that the hydrogenation reactor at pressures at 4 and 7 bar produced biofuels with predominant hydrocarbon contents of cycloalkanes and alkanes, while that at 10 and 13 bar produced biofuels with predominant contents of alkanes and alkenes. In comparison, diesel fuel contains mostly alkanes and aromatics. However, analysis over the whole content of bio-oil by H-NMR found that different pressures of reactor hydrogenation did not reduce alkene compositions in biofuels appreciably from alkene composition in bio-oil feed. In comparison, diesel fuel contained mostly alkanes with aromatic composition about 4% and no alkene content. Various data suggest that alkene content in the biofuels be reduced to approach their viscosity to that of diesel fuel. Modification of the hydrogenation reactor is required by improving convective momentum of hydrogen gas into the bio-oil to enhance contact of solid catalyst, hydrogen gas and bio-oil.

Modification of UASB reactor by using CFD simulations for enhanced treatment of municipal sewage.

Up-flow anaerobic sludge blanket (UASB) has been in use since last few decades for the treatment of organic wastewaters. However, the performance of UASB reactor is quite low for treatment of low strength wastewaters (LSWs) due to less biogas production leading to poor mixing. In the present research work, a modification was done in the design of UASB to improve mixing of reactor liquid which is important to enhance the reactor performance. The modified UASB (MUASB) reactor was designed by providing a slanted baffle along the height of the reactor having an angle of 5.7° with the vertical wall. A two-dimensional computational fluid dynamics (CFD) simulation of three phase gas-liquid-solid flow in MUASB reactor was performed and compared with conventional UASB reactor. The CFD study indicated better mixing in terms of vorticity magnitude in MUASB reactor as compared to conventional UASB, which was reflected in the reactor performance. The performance of MUASB was compared with conventional UASB reactor for the onsite treatment of domestic sewage as LSW. Around 16% higher total chemical oxygen demand removal efficiency was observed in MUASB reactor as compared to conventional UASB during this study. Therefore, this MUASB model demonstrates a qualitative relationship between mixing and performance during the treatment of LSW. From the study, it seems that MUASB holds promise for field applications.

Performance of the water gas shift process with a ruthenium catalyst for hydrogen production in a membrane reactor

The water gas shift process (WGS) was developed in the presence of a ruthenium catalyst (Ru 2 wt%/TiO2), identified in anatase form (2θ 25.31°, 37.67°, 47.95°) and having the textural characteristics 82 m2 g−1 and 0.37 cm3 g−1. Prior to the reaction operations, independent experiments with hydrogen-argon fluxes indicated permeation selectivity for hydrogen in the Pd–Ag membrane, which increased when the H2/Ar ratio and temperature were higher. The catalytic processing was performed in a membrane reactor (MR) at moderate temperatures (453–573 K) under atmospheric pressure. The operations were initially performed in a fixed bed reactor mode, without hydrogen permeation, and then improved due to membrane operation, when higher carbon monoxide conversions were obtained at all temperatures. At 573 K, with and without permeation, 90 and 75% of the carbon monoxide conversions were obtained. The higher conversions reached the maximum conversion predicted by the thermodynamic equilibrium. In the operations performed with permeation (MR), hydrogen recovery (75–96%) was 4–6 times higher than that obtained without permeation.

New operational mode of an electrochemical reactor and its application to the degradation of levofloxacin

The flow-by electrochemical reactor is generally used in batch mode with extended process time in order to achieve high efficiency in the removal of organic contaminant from aqueous solution. Moreover, the batch mode system is inappropriate for the treatment of wastewater in high volume or as a continuous stream. This paper presents a new operational mode for the electrochemical reactor in which the electrolyte passes over the electrodes just once at a reduced flow rate and with high hydraulic retention time. The concentration of hydrogen peroxide generated in the reactor running in the single-pass flow mode attained 10.2mgL−1cm−2 in acid medium, a value similar to that obtained previously with the same type of reactor operating in batch mode. In the single-pass mode, the electrochemical reactor showed high rates of removal of the antibiotic levofloxacin (initial 50mgL−1) and organic load (initial 130mgL−1) up to 99 and 86%, respectively, when operated under electro- or photo-Fenton degradation conditions (acid medium with Fe2+ ions; absence or presence of UV irradiation). Degradation of levofloxacin generated high levels of nitrate (up to 4.5mgL−1) and various by-products that could be identified by liquid chromatography-mass spectrometry.

ZnO Nanoparticle Fortified Highly Permeable Carbon/Silica Monoliths as a Flow-Through Media.

We demonstrate a facile one-pot synthesis of porous "flow-through" ZnO nanoparticle impregnated carbon/silica monoliths with high mechanical strength and interconnected end-to-end pores decorated with functional and catalytic nanoparticles. The materials and conditions for the synthesis were tailored to achieve the desired properties of high mechanical strength, good flow-through permeability, and crack-free morphology. Monoliths were prepared from a resorcinol formaldehyde rout but with the addition of tetraethyl-orthosilicate and a metal oxide precursor, ZnCl2. The monoliths were ambient dried and carbonized under optimized conditions to suppress cracks. Compressive tests of both the resin and carbonized monoliths were performed to examine the effect of the metal oxide precursor on the mechanical properties. The permeability of the monoliths was determined to verify their utility as a flow-through material. The monoliths exhibited a high compressive modulus of ∼30 MPa compared with conventional carbon aerogels and a permeability of ∼10-12 m2. Various characterization techniques were used to analyze the surface morphology, pore texture, and chemical composition of the monoliths. Finally, Ag nanoparticles were incorporated in the monoliths to demonstrate an example of a "flow-through" catalysis application where controlled catalytic conversion of para-nitrophenol into para-aminophenol could be achieved in a continuous flow reactor mode.

Development of correlations for predicting hydrodesulfurization of straight-run gasoil by factorial model

The application of factorial experimental design is reported in order to evaluate the effect of operating conditions on hydrodesulfurization (HDS) activity evaluated at micro-reaction scale. Reaction temperature, liquid hourly space-velocity (LHSV), amount of catalyst loaded to the reactor, reactor mode of operation (down-flow and up-flow), and catalytic bed dilution with inert material were studied as operating variables. Percentage of sulfur removal was selected as response variable. Experimental results were analyzed by considering main effects of variables and their interactions, as well as analysis of variance, regression analysis, and analysis of residuals. For the case studies, the variables that have greater effect on the HDS activity are the temperature and LHSV, followed by the catalyst amount and the dilution of the catalytic bed. Experimental HDS activity tests of straight-run gasoil (SRGO) were performed in down-flow mode (case study A), up-flow mode (case study B), and up-flow mode with dilution of catalytic bed (case study C). The maximum HDS obtained was 98.30%, 97.49%, and 95.60%, respectively. The regression models developed in this work allows for the prediction of HDS activity of SRGO at certain conditions, with correlation coefficient higher than 0.98 and error less than 0.7%. The proposed methodology can be extended to other situations aiming at defining optimal operating conditions to achieve desired levels of sulfur content in the product.

Chromium(VI) Removal from Aqueous Solution by Magnetite Coated by a Polymeric Ionic Liquid-Based Adsorbent.

An evaluation of the chromium(VI) adsorption capacity of four magnetite sorbents coated with a polymer phase containing polymethacrylic acid or polyallyl-3-methylimidazolium is presented. Factors that influence the chromium(VI) removal such as solution pH and contact time were investigated in batch experiments and in stirred tank reactor mode. Affinity and rate constants increased with the molar ratio of the imidazolium. The highest adsorption was obtained at pH 2.0 due to the contribution of electrostatic interactions.

Case studies with mathematical modeling of free-radical multi-component bulk/solution polymerizations: Part 2

ABSTRACTIn Part 2 of this series of two extensive overviews of multi-component polymerization case studies, we again present mathematical modeling results with experimental confirmations. Part 2 represents a refinement and expansion of the detailed and extensive mathematical model presented in Part 1 for free-radical, bulk and/or solution multi-component polymerizations. The expansion is mainly with respect to depropagation, thus making the model more fluent at elevated polymerization temperatures and, in parallel, with additional features as backbiting (with systems involving butyl acrylate). The model considers up to six monomers (unique in the literature), for either batch or semi-batch reactor modes. As the simulator database contains several monomers, initiators, solvents, chain transfer agents and inhibitors, all tested over a wide range of polymerization conditions, from data in both academic and industrial laboratories, several hundred combinations of ingredients can be modeled. The many outputs generated by the model include conversion, molecular weight, polymer composition, branching indicators, sequence length, as well as many other polymerization characteristics related to both production rate and polymer quality. Although the only literature data found to date contain a maximum of four monomers, model predictions for homo-, co-, ter- and tetra-polymerizations show reasonable agreement against the data at both regular and elevated temperatures. With these expansions, this model is directed towards becoming a complete free-radical polymerization tool for training and educational uses both in industry and academia.

Modeling the design and operational mode of a continuous membrane reactor for enzymatic lignin modification

The modification of lignin-derived compounds such as technical lignins, which are highly aromatic and therefore valuable as renewable feedstocks for the biobased product industry, is still a challenging and multidisciplinary task. An enzyme membrane reactor system (EMRS) featuring a continuous stirred-tank reactor and an external ceramic crossflow ultrafiltration membrane is a promising configuration, particularly when combined with ligninolytic heme peroxidases (PODs) as biocatalysts, such as the new versatile peroxidases (VP) described herein. However, time-dependent irreversible enzyme inactivation caused by the co-substrate H2O2 and the fouling of the filtration membrane are limiting factors. To facilitate rational bioprocess development and reactor design, we present an overall modeling concept for a continuous operating mode that addresses both limitations. When including H2O2-related VP inactivation dynamic model analyses showed that two H2O2 molecules were required to convert one molecule of the reducing substrate (here, adlerol). In this context, an (initial) enzyme inactivation rate ki0 caused by factors other than H2O2 (e.g. the used buffer system) was introduced. Because oxygen utilization is characteristic of normal POD actions, the continuous online measurement of dissolved oxygen concentration was useful to monitor enzyme inactivation and therefore an excess of H2O2.

An experimental parametric study on natural circulation BWRs stability

A parametric study on the stability performance of a prototypical natural circulation BWR is performed with the downscaled GENESIS facility. The GENESIS design is based on fluid-to-fluid modeling and includes an artificial void reactivity feedback (VRF) system for simulating the neutronic-thermal-hydraulic coupling. In this work a more sophisticated VRF system than its predecessors is developed and implemented. The VRF allowed investigating different configurations relevant for the reactor design. The experiments show that changing the fuel rods diameter to a half (doubling) decreases (increases) the stability performance of the system while the resonance frequency increases (decreases). In addition, it is found that the use of MOX fuels in a BWR slightly decreases the stability performance of the reactor. On top of this, it is clearly observed that at least two oscillatory modes exists in the system, the thermal-hydraulic mode (associated to density waves traveling thorough the core plus chimney section) and the so-called reactor mode (related to density waves travelling thorough the core). It is observed that the last one is amplified by increasing (in an absolute sense) the void reactivity feedback coefficient. Details regarding the interplay between these oscillatory modes is also given.

Comprehensive assessment of the L-lysine production process from fermentation of sugarcane molasses.

L-Lysine is an essential amino acid that can be produced by chemical processes from fossil raw materials, as well as by microbial fermentation, the latter being a more efficient and environmentally friendly procedure. In this work, the production process of L-lysine-HCl is studied using a systematic approach based on modeling and simulation, which supports decision making in the early stage of process design. The study considers two analysis stages: first, the dynamic analysis of the fermentation reactor, where the conversion of sugars from sugarcane molasses to L-lysine with a strain of Corynebacterium glutamicum is carried out. In this stage, the operation mode (either batch or fed batch) and operating conditions of the fermentation reactor are defined to reach the maximum technical criteria. Afterwards, the second analysis stage relates to the industrial production process of L-lysine-HCl, where the fermentation reactor, upstream processing, and downstream processing are included. In this stage, the influence of key parameters on the overall process performance is scrutinized through the evaluation of several technical, economic, and environmental criteria, to determine a profitable and sustainable design of the L-lysine production process. The main results show how the operating conditions, process design, and selection of evaluation criteria can influence in the conceptual design. The best plant design shows maximum product yield (0.31gL-lysine/g glucose) and productivity (1.99g/L/h), achieving 26.5% return on investment (ROI) with a payback period (PBP) of 3.8years, decreasing water and energy consumption, and with a low potential environmental impact (PEI) index.

A universal method of sample preparation for liquid, solid, and gaseous samples based on a conversion solid-electrolyte reactor for measuring the isotope composition of light elements

A universal conversion solid-electrolyte reactor (SER) based on zirconium dioxide stabilized by yttrium oxide is developed. It ensures the complete oxidation of organic compounds of complex molecular structure in different physical states or the complete reduction of water and organic oxygen-containing substances in a flow of helium carrier gas. The optimum oxidation operation mode of the solid-electrolyte reactor is the mode ensuring the complete oxidation of organic compounds at the boundary line of the oxidation of organic compounds and, at the same time, prevents the inflow of oxygen from the environment to the carrier gas. The potential of the working electrode selected for carrying out experiments was equal to–175 mV (oxidation operation mode). The temperature of the reactor was 940–950oC. The standard deviations δ13СVPDB for organic substances oxidized by SER varied from 0.11 to 0.57‰ and were smaller than standard deviations in the oxidation of corresponding compounds in a commercial reactor. In using the SER–IRMS method (isotope ratio mass spectrometry combined with the solid-electrolyte reactor), a minimum amount of water (60–100 ng) was required. Standard deviations δDVSMOW attained using SER and using a commercial pyrolytic reactor were close to each other. Because of the simplicity and reliability of the design, the developed SER can successfully replace commercial oxidation and reduction reactors in isotope ratio mass spectrometry. In addition, the solid-electrolyte reactor can serve as a chromatographic detector, requiring no calibration in contrast to other detectors.

Denitrification of high strength nitrate bearing acidic waters in granular sludge sequencing batch reactors

Nitrate containing acidic wastewaters are generated in nuclear fuel cycle operations. These waters are often neutralized prior to either storage or biological treatment. In this study, treatment of high strength nitrate bearing acidic waters was investigated in a sequencing batch reactor. A six liter reactor was inoculated with activated sludge and operated in sequencing batch reactor mode by feeding simulated nitrate wastewater at pH 7.5. After establishing denitrifying microbial consortia in the form of compact granules, the pH of the feed was gradually decreased to 5.0 and then to 4.0. The in situ neutralization of the feed in the reactor by the denitrification-driven alkalinity and the acclimatization strategy helped to achieve complete and stable denitrification during long term operation. The denitrifying microbial community developed in the sequencing batch reactor predominantly consisted of rod- and cocci-shaped microorganisms. This study showed that nitrate bearing acidic effluents can be directly denitrified in granular sludge sequencing batch reactors without a prior treatment. Thus, in situ neutralization and acclimatization strategy can be a potential approach to be considered for treating nitrate contaminated acidic waters.

Aerobic granulation of protein-rich granules from nitrogen-lean wastewaters

Proteins (PN)-rich granules are stable in structure in long-term reactor operations. This study proposed to cultivate PN-rich granules with PN/polysaccharides (PS) >20 from nitrogen lean wastewater, with ammonia-nitrogen as sole nitrogen source at chemical oxygen demand (COD)/N of 153.8. The yielded granules can sustain their structural stability in sequencing batch reactor mode for sufficient treatment of wastewaters up to 7000mg/L COD and with COD/N<500 and in continuous-flow reactor for successful 216-d treatment of wastewaters up to organic loading rate (OLR) of 39kg/m3-d. The produced granules were enriched with Firmicutes and β-proteobacteria as dominating strains. More than 58% of the nitrogen fed in the nitrogen-lean wastewater is converted to the PN in the granules. The replacement of ammonia by nitrate as sole nitrogen source led to granules enriched with γ-proteobacteria which are easily deteriorated at low OLR.