Helical Reactor Research Articles

TiO2-catalyzed photodegradation of methylene blue in a helical FEP tubing reactor: modeling and optimization using response surface methodology

A novel photocatalytic reactor was developed to degrade methylene blue in water using titanium dioxide (TiO2) as a catalyst and fluorinated ethylene propylene (FEP) tubing as a transmitter for ultraviolet (UV) radiation. The reactor was operated by continuously flowing the solution through narrow tubes that were exposed to UV radiation. The efficiency of the reactor was evaluated by comparing it to a previous study that used quartz glass tubing. The study also investigated the effects of flow rate, initial concentration, pH, TiO2 dose and UV radiation without a catalyst on the degradation of methylene blue. The results showed that the FEP tubing was a more efficient UV transmitter than quartz glass. The efficiency of the reactor was also affected by the flow rate and pH of the solution. The highest degradation efficiency was achieved at a flow rate of 10 mL/min and a pH of 7.0. The use of TiO2 as a catalyst also significantly improved the degradation efficiency, with an almost doubling of the degradation rate when compared to the case without a catalyst. This study demonstrates the potential of the FEP tubing-based photocatalytic reactor for the degradation of methylene blue in water. The reactor is easy to operate and can be scaled up for industrial applications.

Design of oscillatory helical baffled reactor and dual functional mesoporous catalyst for oxidative desulfurization of real diesel fuel

Enhancing real diesel fuel properties by expelling pollutants using a new design has received considerable interest in the present day. This work investigates the conversion of sulfur compounds via oxidation reaction with peracetic acid as an oxidant. For this purpose, a dual functional mesoporous catalyst was synthesized via loading active metal (iron oxide) nanoparticles over mesopore γ-alumina-anatase titanium oxide prepared via the impregnation procedure (IWI) and precipitation methods, respectively. The novel design of the mesoporous catalyst represents the dual functional catalyst in the oxidative desulfurization process (ODS). The mesoporous catalyst that was formulated underwent a comprehensive analysis using various characterization techniques such as physical adsorption-desorption under N2, X-ray diffraction-XRD, Fourier transforms infrared spectroscopy-FTIR, Field Emission Scanning Electron Microscopy-FESEM, Energy dispersive X-ray analyzer-EDX, and thermogravimetric analysis-TGA. A newly designed laboratory pilot plant for an oscillatory helical baffled reactor (OHBR) was developed and utilized for the ODS process to evaluate the performance of the synthesized mesopore catalyst. The investigated rapid conversion for sulfur removal was found to be 98.42 % under ambient operating conditions such as oscillation of frequency 2 Hz, oscillation of amplitude 8 mm, temperature of oxidation 80°C, and residence time of 9 min. It is clearly observed that the new design of OHBR and mesoporous catalyst highly affected sulfur removal, resulting in a clean diesel.

Continuous flow production of bioactive ceria quantum dots: New paradigms to the effect of process parameters on surface oxygen vacancy tuning

Precisely monitored nucleation-growth kinetics for governing the size, surface chemistry, and sought-after attributes of quantum dots (QDs) for large-scale manufacturing remains a formidable challenge. This study evinces the importance of ultrafast mixing and high heating rates for rapid nucleation, particularly in synthesizing monodispersed QDs with enriched surface defects. Recently, cerium oxide (CeO2) nanostructures have gained prominence in antioxidant therapy owing to the co-existence of Ce3+ and Ce4+. However, current batch processes lack scalability, reproducibility, and control over the reaction kinetics, key for fine-tuning the surface defect-driven properties of CeO2 nanostructures. Addressing this knowledge gap, we demonstrate a unique, sustainable, continuous flow platform that allows simultaneous engineering of surface oxygen vacancies (VO●) and regulates the size of L arginine functionalized CeO2 QDs (VO●-rich l-arg-CeO2 QDs). Introduction of the helical coil reactor regulated by dean vortices yields monodispersed QDs with enhanced Ce3+/Ce4+ratio and VO● at the surface. Through various experimental methodologies, we showed how adjusting temperature, flowrate, and pH enables achieving the desirable size (3 nm), thereby bestowing an optimal surface Ce3+ and VO● fractions, pivotal for size-dictated photo-response, physiochemical properties, and biofunctionality of the QDs. The abundant surface VO● (72 %) entails narrowing of the band gap (∼ 2.5 eV), resulting in unprecedented photothermal response (ΔT = 19.7 ± 0.6 °C) and photoluminescence, features not typically found in defect-free conventional CeO2 nanostructures. With a strategic combination of process parameters, the defect-rich material system displayed excellent biocompatibility (95.6 %), and antioxidant efficacy on human keratinocyte (HaCaT) cells, and long-term stability (ζ = -29±1.5 mV) in suspensions, even after 120 days. This economical, high throughput continuous flow platform for fabricating biofunctionalized VO●-rich l-arg-CeO2 QDs outperforms conventional batch processes, opening numerous possibilities for lab-to-clinic translation in the fight against oxidative stress-related disorders.

High potential of the vacuum UV-activated peracetic acid (VUV/PAA) process in eliminating recalcitrant contaminants and waterborne pathogens: Assessing the efficacy of annular and helical reactor configurations

The effectiveness of VUV/PAA in degrading Ciprofloxacin (CIP) and inactivating E. coli was studied. VUV was more efficient than UVC in activating PAA. The VUV/PAA process degraded CIP twice as fast as the VUV process under similar conditions and was more effective in acidic or neutral solutions than in alkaline solutions. The hydroxyl radicals formed were key to the degradation, whereas the R-C species played a lesser role. Furthermore, the VUV/PAA process achieved a satisfactory CIP degradation rate in spiked tap water. Operating the reactors in batch mode, completely degraded CIP in 30 min, and 86.5 % TOC removal was achieved in 120 min of a 40 mg/L CIP solution. In addition, VUV/PAA inactivated a 6.5-log of 1.2 × 109 CFU/mL of E. coli in only 5 min. Moreover, the VUV/PAA process was compared in a helical (HPR) and annular photoreactor (APR); the HPR led to approx. x3 higher ▪OH generation and superior CIP degradation rate. The VUV/PAA process improved CIP degradation in both the APR and HPR with longer hydraulic residence times, where the HPR outperformed the APR in degrading CIP. Overall, the VUV/PAA@HPR system is an effective method for enhancing the degradation of recalcitrant organics and waterborne pathogens in contaminated water, including in the flow-through mode, making it a promising process for water treatment.

Torrefaction of wood and garden wastes from municipal solid waste to enhanced solid fuel using helical screw rotation-induced fluidised bed reactor: Effect of particle size, helical screw speed and temperature

Using wood (WW) and garden (GW) wastes from municipal solid waste as renewable biofuel is hindered by their high moisture content, volatile matter (VM), and low calorific value (CV). This study aimed to evaluate the fuel properties of torrefied WW and GW in a helical screw rotation-induced fluidised bed reactor. The torrefaction process was conducted at 250–300 °C with sample particle size of 0.5, 1–2, and >2 mm, and helical screw speed of 0–100 rpm. The torrefied WW and GW grindability, thermal, and structural properties were analysed at different temperatures and compared with raw samples. The results showed that the mass and energy yields decreased by 32.71% and 22.04% for WW and 16.07% and 12.21% for GW as the temperature and speed increased, while particle size had no significant effect. Temperature had the most significant influence, followed by speed and particle size. The VM, oxygen, and hydrogen content decreased with increasing temperature, while fixed carbon, CV, and carbon content increased. These properties remained relatively constant with increasing particle size and speed, except at 50 rpm. Furthermore, the grindability, thermal, and structural properties improved with increased temperature.

Continuous synthesis of ruthenium nanoparticles with tuneable sizes using ruthenium nitrosyl nitrate precursor

Continuous synthesis of ruthenium nanoparticles with controllable sizes between 2–4 nm in the absence of organic capping ligands.

An efficient separation for fluoride-ions from water supplies by ion precipitate flotation: Pilot scale study with generation of coagulative bubbles

Bubble surface modification is a promising technique that enables to increase the efficiency of a treatment that aims to remove a certain particle with lower consumption of chemical inputs. In this study, the so-called coagulative bubbles were generated from a mixed system consisting of amphoteric surfactant (Cocamidopropyl betaine, CAPB) and inorganic polymer coagulants (aluminum sulfate and calcium chloride) for the removal of fluoride ions present in groundwater destined for human supply. The critical micellar concentration (CMC) of CAPB was 0.26 mmol L−1. The coagulant bubbles (CB) were generated from pressurizing the coagulant solution in distilled water and applied continuously in a helical tubular reactor. The CB treatment method provided higher fluoride removal compared to conventional treatment with simple coagulant application. The CBs generated with Al made it possible to remove approximately 98 % of the initial amount of fluoride measured (3.5 mg L−1) with a dosage of 31 mg L−1 of Al; feed flow rate of 20 L min−1; pH 6 ± 0.5; and saturation pressure of 3 atm. This same operation, but without generation of CBs (regular atmospheric pressure), allowed the removal of 67 % of the initial fluoride concentration.

Microwave assisted oxidative desulfurization in a helical coil reactor: CFD simulation and experimental validation

In the present work, the microwave assisted oxidative desulfurization (ODS) of model light fuel oil in a helical coil reactor was investigated experimentally and numerically. The main purpose of the study was to investigate the influence of the microwave irradiation power and reactor operating parameters on the sulfur removal in the ODS process. A coupled 0D-ODE and 3D-CFD model was developed to describe the two-phase flow, heat and mass transfer, and electromagnetic waves distribution inside the reactor and microwave box. Experimental tests were also conducted to validate the proposed model. In addition, a kinetic analysis was carried out by estimating the pre-exponential factors and activation energies of the reaction system using Levenberg-Marquardt algorithm. Based on the simulation results, the effects of various operating parameters including oxidant to sulfur molar ratio (nO/ns), formic acid to sulfur molar ratio (nacid/ns), microwave irradiation time, and microwave power on the sulfur removal and electromagnetic heat generation were discussed. Accordingly, more than 97% sulfur conversion was achieved under the optimal operating conditions namely no/ns=2, nacid/ns=30, irradiation time = 10 min, and microwave power = 800 W. The dielectric properties of different samples under the microwave irradiation were explained to show key contribution in the extent of the electromagnetic energy absorbed and the volumetric heat generated.

Continuous Hydrogenation of Cinnamaldehyde: Gas–Liquid–Liquid–Solid Helical Coil Reactor

Continuous Hydrogenation of Cinnamaldehyde: Gas–Liquid–Liquid–Solid Helical Coil Reactor

Bending and Twisting Characteristics of REBCO Lap Joint With Indium

Joint-winding of high-temperature superconducting (HTS) magnets has been proposed for an advanced helical reactor, the FFHR-d1 reactor. In the fabrication method, stacked tapes assembled in rigid structure (STARS) conductors—in which a simple stack of rare-earth barium copper oxide (REBCO) tapes within a metal casing—are connected using a bridge-type mechanical lap joint with indium foil inserted. Previous studies showed sufficiently low joint resistances in straight conductors, although curved joints would be necessary for the fabrication of helically-wound HTS coils. In this study, we devised joint, twist, and bend (JTB) and twist, bend and joint (TBJ) procedures for the curved-joint fabrication. We evaluated the joint resistance as a function of bending and torsional strain for the JTB procedure as well as the joint resistance as a function of bending radius or twist pitch for the TBJ procedure. Based on the experimental results and discussion, the JTB procedure could be applied to large-scale helical coils—such as those used in the FFHR-d1 reactor—whereas the TBJ procedure could be adopted for smaller-scale helical coils such as those used in the FFHR-a1 reactor.

Mixing effects on the gas flow and mass transfer in a vertical single helical ribbon agitated reactor for propylene polymerization

The gas–solid vertical single helical ribbon agitated reactor is widely used in the polypropylene industry. The gas flow and mass transfer determine the heat transfer capacity and product quality. In this work, the pressure drop was measured below and above minimum fluidization velocity (umf). Then, the axial and radial dispersion coefficients (DL and DR) were estimated below umf by measuring the step residence time distribution and the stationary radial tracer profiles, respectively. Pressure analysis show the agitation significantly reduces the bed pressure drop, changing the fixed bed below umf and bubbling bed above umf to an agitated bed with a periodic voidage. The DL was proportional to the gas velocity, with little influences of the stirring speed. The radial tracer profiles show the bed is divided by the inner diameter of the helical ribbon into the peripheral ascending region and the central descending region, without gas exchange between them. Furthermore. the tracer profiles in the descending region are classified into two types. For type I, the DR, calculated by the plug flow model with radial dispersion, is proportional to the gas velocity, with little effects of stirring speed. Type II shows uniform profiles due to the deflection of the gas flow toward the low pressure area at the inner diameter of helical ribbon. The causes of the two types are explained by the relative size of particle circulation and gas flux. These two flow regimes are quantitatively clarified with an empirical correlation of Re and Fr as flow regime transition boundary, namely dispersed plug flow and perfect mixing flow. With lower Re and higher Fr, it changes from dispersed plug flow to perfect mixing flow.

Production and Growth Performance of Nannochloropsis oculata (Droop) Hibberd in the Helical Photobioreactor

Phytoplankton species preferred in marine fish farming are the primary food source in the larval and young stages of bivalve mollusks, along with some fish and shellfish larvae. For this reason, selecting the appropriate phytoplankton and production technique for feeding marine fish larvae is crucial. Nannochloripsis oculata microalgae species, widely used in rearing sea bream and sea bass larvae and feeding rotifers, has an essential place in our country. N. oculata microalgae species, which is used in rearing sea bream and sea bass larvae and feeding rotifers, was produced in a helical photobioreactor by applying a continuous production technique at 30 ‰ salinity, and its growth performance was aimed to be investigated. In the study, N. oculata was grown in a helical photobioreactor at 30‰ salinity by applying the continuous production technique for two weeks, and the daily cell number and specific growth rate were determined. The study was repeated three times. The supply of live feed for marine fish fry and hatcheries established for this purpose is one of the most critical problems. The latest technology in the production of microalgae, which is the primary link of the live feed chain in this sector, is continuous algae production in helical tubular reactors. The helical tubular reactor used in the study consists of a transparent hose system consisting of a completely tubular helical reactor designed for microalgae production. The helical tubular continuous production system offers more efficient and economically more convenient alternatives than existing production systems. One of the most essential advantages of this system is that the system can be designed without requiring significant capital. The continuous culture technique allows the application of long-term and safe algae cultures. With this system, besides providing continuity in production, the negativities in batch production can be eliminated with adequate light. Since the algae production with the continuous method in the spiral photobioreactor remains in the maximum growth phase for a longer time than the batch production, it is a system with high production efficiency and quality, and production capacity is guaranteed. In addition, the algae product harvesting in the continuous system ensures the daily harvesting of algae as much as half of the system volume. A helical reactor enables automation in algae production and high-quality production over long periods. In the study, the sowing density of N. oculata was determined as 1.068x106 ±0.006 cells/mL. Algin cell growth increased logarithmically during the first five days. From the 5th day to the 15th day, the increase in the number of cells was determined as 12.35x106±0.165 cells/mL at the highest and 8.76x106±0.709 cells/mL at the lowest. However, on the 13th day, it was determined that the increase in algin cells was 12.35x106±0.165 cells/mL, and the specific growth rate decreased by 0.189±0.016 divisions/day. As a result of the study, the number of cells of N. oculata algae 5-15 increased. It was determined that it increased 10 times between days. In this context, it was possible to harvest half of the reactor volume of algae daily at maximum cell density for long periods in the helical reactor

Unleashing the Influence of High-Throughput Flow Process Optimization on Luminescent Behavior of Engineered ZnO Quantum Dots

Engineered ZnO quantum dots (E-QDs) are sought-after nanostructures in healthcare and optoelectronic industries, necessitating a paradigm shift toward high-throughput continuous flow platforms, the crux to whose successful design and performance lies in comprehending the nucleation-growth kinetics, defect engineering, and reaction dynamics. This work investigates the synergistic interplay of enhanced hydrodynamics and heat–mass transfer in the helical coil reactor, fostering rapid nucleation-growth-driven E-QDs fabrication. We integrated computational fluid dynamic modeling, and comprehensive experimentation for producing E-QDs with record-high photoluminescence quantum yield (PLQY) (∼89% in the yellow-green spectrum) by carefully creating oxygen vacancies via a novel reproducible protocol. Dean vortices formed due to the helical geometry facilitated ultrafast mixing and accelerated reaction kinetics, yielding colloidally stable E-QDs in gram-scales [ζ = −39.7 mV, polydispersity index (PDI) ∼0.22] with a narrow particle size distribution (average particle size ∼4.5 nm). Contrastingly, the conventional batch route produced less stable E-QDs with ζ value of −15.3 mV, PDI ∼0.41, and diminished PLQY (∼40%) because of inadequate process control, batch-to-batch variability due to poor mixing, and heat transfer. The simple, economical, in-house-fabricated flow reactor manifested ∼90% increment in yield and reduced product cost. Thus, this research demonstrated the benefits of simulation-driven process engineering and reactor design in catalyzing QDs-based innovations.

Development of steady-state fusion reactor by Helical Fusion

The Helical Fusion group (Helical Fusion Co., Ltd. in Japan and Helical Fusion USA, Inc.) is developing a 50 MWe-class steady-state helical fusion reactor, which is a kind of stellarator called heliotron composed of two continuous helical coils similar to the large helical device and is operated without plasma current. HESTIA plays the role of the fusion pilot plant. The first-of-a-kind fusion power plant that would follow HESTIA will be a 100 MWe-class steady-state helical fusion reactor. After more than one year of continuous operation, maintenance will be completed within 3 months, aiming for an availability larger than 80%. High-temperature superconducting magnet coils are adopted to generate 8 T of the magnetic field at the helical coil center. HESTIA is a deuterium-tritium fusion reactor, where tritium is self-produced using liquid metal blanket systems. The first wall of the liquid metal blanket including the divertor strike zone is covered and protected by liquid metal free-surface flow, and therefore, individual divertor systems are not required in HESTIA. Electron cyclotron heating is adopted for plasma heating. Since plasma current drive is not required, HESTIA can be operated at a low fusion gain of ∼13, and steady-state operation is principally possible on the order of a year. After a few years of individual development phases, a prototype device is planned to be constructed and operated for the integrated demonstration before starting the construction of HESTIA.

Multi-objective design optimization of hydride hydrogen storage reactor structured with finned helical tubes based on energetic and economic analyses

Hydride-based systems are a potential alternative to hydrogen storage technologies due to their simple structure and ambient operating conditions. The optimization of hydride reactor design factors is highly correlated to the targeted application. This research focuses on optimizing the thermal-static performance of LaNi5-holding helically coiled hydride reactors employing combined response surface methodology, computational modeling, and a desirability approach. The structural geometric design optimization factors include the diameter of the helical tubes and shell, the number of helical tubes, the pitch, and the distance between two adjacent helical tubes. Responses comprise a dimensionless characteristic response – weight ratio (static performance) and 90 % absorption time with maximal heat extraction rate (thermal performance). The quadratic regression model outperformed the linear regression models in terms of accuracy and reliability, effectively reducing the number of computational runs by 83 % compared to the standard parametric study-based technique. Combinatorically assessing the weight ratio and thermal power to be set to the maximum at the quickest absorption time resulted in selecting the best helical reactor design. The optimal base case was further improvised by integrating fins, which were optimized using the proposed methodology. The optimal base case and finned helical reactor subjected to sensitivity analysis revealed that the latter exhibited an average 18 % fall in complete saturation time and a 16 % rise in thermal power despite the 5.66 % loss in weight ratio. The Levelized cost of hydrogen storage was substantially reduced by 18–23 % when operated at higher supply pressures and fluid inlet temperatures. Besides, when the price of the finned reactor to its base case ratio was cut from 1.5 to 1.1, the optimized finned reactor turned economical. Furthermore, the outcomes of a systematic literature comparative study demonstrated that the constructed finned helical reactor was superior to its equivalent, accounting for a 60–75 % drop in 90 % saturation time. As an upshot, this study aids the researchers in designing accurate and apt objective-based hydride reactors using the proposed statistical method: coupled quadratic regression-thermal modeling-desirability approach-based design optimization.

Theoretical analysis of a solar membrane reactor with enhanced mass transfer by using helical inserts

Product separation Pd-based membrane can boost performance of conventional solar-driven thermochemical reactors by accelerating reaction processes. However, concentration polarization due to mass transfer resistance limits the conversion and efficiency of solar membrane reactor. In this work, the helical insert-enhanced solar membrane reactor is proposed to eliminate adverse impact of concentration polarization. The influence mechanism of radial mass transfer enhancement on reactor performance is analyzed. The number of helical inserts is optimized and the performance enhancement of proposed reactor under different operating conditions is explored. It is shown that enhancing radial mass transfer effectively alleviates concentration polarization and overall methane conversion can be maximally improved by about 29 %. By applying multi-helical inserts, the radial mass transfer in reaction bed is greatly enhanced, which achieves homogenous radial component distribution, improves the hydrogen separation performance and expands high-quality reaction zone. In comparison to the original membrane reactor, the optimized reactor with 5-helical inserts can increase methane conversion, fuel efficiency, and hydrogen recovery by 16.4 %, 18.7 %, and 21.4 %, respectively, in the operating temperature range of 673–823 K. Also, it is presented that the proposed helical insert-enhanced solar membrane reactor can deliver significant performance improvement under different operating conditions.

Toward the realization of a commercial Helical Small-Scale Steady-State Fusion Reactor

Toward the realization of a commercial Helical Small-Scale Steady-State Fusion Reactor

Design and assessment of a new helical fixed bed type CO2 methanation reactor

In the present study, new designs of helical methane/natural gas reactors are proposed. The reactor harnesses the Sabatier reaction, in which CO2 reacts with H2 gas to produce methane. The CO2 and H2 used within the reactor can be produced through biomass gasification and electrolysis, thereby making the process renewable. The study develops three models with three diameters (0.0254 m, 0.0318 m, and 0.0381 m) and the same volume (0.001 m3). The helical methane reactor design can be optimized by varying specific parameters, such as the reactor inlet temperature, cooling temperature and inlet pressure. Most notably, the reactor model with a diameter of 0.0381 m can produce a reactant conversion and a yield of 75% and 87%, respectively. Additionally, the model having a cross-sectional diameter of 0.0254 m is capable of being cooled most effectively when a coolant temperature of 200 °C is considered.

Seismic Analysis of Magnet Systems in Helical Fusion Reactors Designed With Topology Optimization

Superconducting magnets in fusion reactors are subjected to a huge electromagnetic force of >100 MN/m. The magnets have to be sustained with a strong-body structure to avoid high stress and deformation. The total weight of the magnet system in the fusion reactor is estimated to be more than 20,000 tons. We applied topology optimization technique to the magnet support structure to reduce the weight of fusion reactors. Compared with the conventional design, we achieved a weight reduction of >25%. Static and seismic analyses were carried out to validate the soundness of the topology-optimized design. Consequently, the stress against the electromagnetic force in the structure was within the permissible range. It was discovered that using seismic isolation structure can adequately prevent the damage to the magnet system even when directly subjected to a massive earthquake.

Numerical Optimization of Electromagnet Current Distribution in Superconducting Linear Acceleration System

An enhancement of the acceleration performance of a superconducting linear accelerator when injecting pellets into a helical fusion reactor has been investigated numerically. For this purpose, a numerical code using the finite element method was developed to analyze both the time evolution of a shielding current density in a high-temperature superconductor film and the dynamic motion of the film. In the present study, to optimize the shape of double magnets, a multi-objective optimization problem is solved using the non-dominated sorting genetic Algorithm-II. The results of the computations show that the optimization of the inner electromagnet is more effective in improving the pellet velocity than that of the outer electromagnet. In addition, we found that the pellet speed and energy efficiency have a trade-off relation. Therefore, it is possible to determine the preferred solution for the design of an acceleration magnet, whether focusing on the pellet speed or the energy efficiency. In other words, this relationship can be used to choose whether to emphasize velocity or efficiency in the design of SLA systems.