Reactor System Research Articles

Development of funnel-type fluidized bed reactor system using microcarriers for cultures of adherent cells

Development of funnel-type fluidized bed reactor system using microcarriers for cultures of adherent cells

Co-Pyrolysis Studies of Agricultural Residue and Plastics for Process Optimization in a Rotary Kiln Reactor System

Co-Pyrolysis Studies of Agricultural Residue and Plastics for Process Optimization in a Rotary Kiln Reactor System

CFD simulation of injection point design for emergency core cooling system of ALLEGRO

The Emergency Core Cooling System (ECCS) is one of the critical safety systems in the Gas-cooled Fast Reactor (GFR) demonstrator ALLEGRO. The ECCS design must be improved to enhance fundamental safety functions, particularly in removing heat from the core under postulated plant conditions. In this paper, we focused on exploring the effect of coolant injection point on the performance of ECCS, for more efficient core cooling under Loss Of Coolant Accident (LOCA) scenarios. We initially performed a 1D primary system loop thermal hydraulic simulation to determine appropriate boundary conditions in case of a LOCA. These conditions were then applied to a CFD model of the ALLEGRO reactor pressure vessel, including injection nozzles at two positions. Transient 3D CFD simulations of LOCA in ALLEGRO were carried out using Fluent to determine location of the most effective emergency coolant injection point. We simulated the flow distribution through the core up to around 30 s after both small- and large-break LOCA events. The results suggest that bottom injection of the emergency coolant is preferred in an updated ECCS design. It provides a more uniform flow distribution across the core and therefore more advantageous than the previously suggested location in the downcomer.

Photocatalytic water splitting for large-scale solar-to-chemical energy conversion and storage

Sunlight-driven water splitting allows renewable hydrogen to be produced from abundant and environmentally benign water. Large-scale societal implementation of this green fuel production technology within energy generation systems is essential for the establishment of sustainable future societies. Among various technologies, photocatalytic water splitting using particulate semiconductors has attracted increasing attention as a method to produce large amounts of green fuels at low cost. The key to making this technology practical is the development of photocatalysts capable of splitting water with high solar-to-fuel energy conversion efficiency. Furthermore, advances that enable the deployment of water-splitting photocatalysts over large areas are necessary, as is the ability to recover hydrogen safely and efficiently from the produced oxyhydrogen gas. This lead article describes the key discoveries and recent research trends in photosynthesis using particulate semiconductors and photocatalyst sheets for overall water splitting, via one-step excitation and two-step excitation (Z-scheme reactions), as well as for direct conversion of carbon dioxide into renewable fuels using water as an electron donor. We describe the latest advances in solar water-splitting and carbon dioxide reduction systems and pathways to improve their future performance, together with challenges and solutions in their practical application and scalability, including the fixation of particulate photocatalysts, hydrogen recovery, safety design of reactor systems, and approaches to separately generate hydrogen and oxygen from water.

Biobased ionic liquid solutions for an efficient post-combustion CO2 capture system

This study explores the use of ionic liquids (ILs) as a novel and efficient alternative to conventional monoethanolamine (MEA) for CO2 capture. While MEA scrubbing is well-known for carbon sequestration, it faces limitations such as high energy consumption, toxicity, and rapid degradation. In contrast, ILs offer advantages such as non-volatility, stability, and reduced corrosiveness. We focus on a biodegradable IL comprising choline ([Cho]) and proline ([Pro]) amino acids to create an eco-friendly solution. Dimethyl sulfoxide (DMSO) is introduced as a diluent to mitigate viscosity issues during CO2 uptake. Our research measures the thermo-physical properties, including density and viscosity of [Cho][Pro] in DMSO at different concentrations. The addition of DMSO resulted in a viscosity reduction of >97 % at a temperature of 303 K for the three virgin solutions compared to the pure IL. In addition, the CO2 capture performance was evaluated using a system of absorption and desorption reactors. The results show that the 25 % wt [Cho][Pro] solution excels, achieving over 90 % CO2 absorption, 0.66 molCO2/molIL in the first cycle, and demonstrating high reusability and regeneration efficiency over multiple cycles. Comparisons indicate that the IL solution outperforms traditional aqueous MEA solutions. Longer term testing confirms the solution's stability and minimal degradation, achieving a regeneration efficiency of >55 % over 30 cycles, suggesting the potential of [Cho][Pro] for sustainable long-term CO2 capture applications.

Coupled feldspar dissolution and secondary mineral precipitation in batch systems: 6. Labradorite dissolution, calcite growth, and clay precipitation at 60 °C and pH 8.2–8.4

We conducted experiments on concurrent labradorite dissolution, calcite precipitation, and clay precipitation in batch reactor systems and tracked reaction processes using multiple isotope tracers. Labradorite was chosen for its role as a major and reactive component in basalt; the experiments thus directly impact our understanding of CO2 storage in basalt aquifers and enhanced rock weathering. We doped initial solutions with 29Si, 43Ca, and Ca13CO3(s). Experiments were conducted at 60 °C and pH ∼ 8.3 for up to 840 h, with isotope ratios in the experimental aqueous solutions measured using MC-ICP-MS. Unidirectional rates of labradorite dissolution near equilibrium were approximately two orders of magnitude slower than far-from-equilibrium rates reported in the literature. Calcite growth occurred near equilibrium and the rates were limited by the labradorite dissolution rates.In the steady state phase, the interplay of these three heterogeneous reactions—labradorite dissolution, calcite growth, and clay precipitation—results in a coupled system that approaches a near-equilibrium state. The system does not reach true equilibrium because labradorite continues to dissolve, albeit at a much slower rate near equilibrium. The overall reaction can be approximated as,Na0.4Ca0.6Al1.6Si2.4O8 + 0.6HCO3- + 1·.7H2O + 0.4H+ → 0.4Na+ + 0.6CaCO3(s) + 0.5Al2Si2O5(OH)4(s) + 0.6Al(OH)4- + 1.4SiO2o(aq)The experimental results show that using short-term far-from-equilibrium rate constants would lead to an overestimation of feldspar weathering rates at the Earth’s surface (e.g., basalt weathering and enhanced rock weathering) and CO2 mineralization in basalt aquifers.

Small break LOCA studies for different layouts of passive safety systems in the IRIS reactor

IRIS (International Reactor Innovative and Secure) is an integral, medium power, light water reactor with advanced safety features. In the first decade of the 21st century, 22 institutions under the leadership of Westinghouse Electric Corporation were involved in its development. The University of Zagreb, along with the Polytechnic of Milan, was in charge of performing safety analyses. A detailed plant model is developed using the RELAP5 code for the analyses of thermal–hydraulic processes in the reactor vessel, the GOTHIC code for the analysis of the processes in the containment and, in addition, the ASYST code for the calculation of a severe accident. Some of the previous small break loss-of-coolant accident analyzes at the existing pipelines are repeated to test the improved plant model. However, the focus of the paper is on the new set of analyzes of hypothetical breaks along the reactor vessel with the aim of determining whether the passive safety systems can ensure successful core cooling. For this purpose, two models are developed with different configurations of the emergency heat removal system and the safety systems inside the containment that inject water into the reactor vessel. The results show the complex and rather ambiguous dependence of the reactor coolant system thermal–hydraulic behaviour on the selected boundary conditions. The scenarios analyzed vary from design basis events to severe accidents. The capabilities of specific safety systems in mitigating the consequences of an accident are determined, depending on the position and size of the break on the reactor vessel wall.

The Role of Micro Propulsion in Enabling Autonomous Operations of Nanosatellites

Micro-Electro-Mechanical Systems (MEMS)-based propulsion devices have significant potential for providing high specific power. The application of Micro Power Generation technology to space propulsion systems can enhance orbit and station-keeping capabilities, potentially at lower costs. New-generation spacecraft and satellites are becoming smaller and require micro-propulsion systems for all aspects of their operations. The development of micro-propulsion systems with associated combustors for micro-electricity generation, utilizing liquid fuel, presents major challenges in fuel injection, mixing, combustion, and chemical reactor systems. A micro-spacecraft with high-accuracy station-keeping and attitude control capabilities needs to have low mass and deliver small impulses. Each nanosatellite will weigh a maximum of 10 kg, including the propellant mass. Provisions for orbital manoeuvres, attitude control, multiple sensors, and instruments, along with full autonomy, will result in a highly capable miniaturized satellite. All onboard electronics will endure a total radiation dose of 100 k rads over a two-year mission lifetime. Nanosatellites designed for in-situ measurements will be spin-stabilized and equipped with a complement of particles and fields instruments. Nanosatellites intended for remote measurements will be three-axis stabilized and equipped with imaging and radio wave instruments. Key technologies under development include: advanced, miniaturized chemical propulsion systems; miniaturized sensors; highly integrated, compact electronics; autonomous onboard and ground operations; miniaturized onboard orbit determination methods; onboard RF communications capable of transmitting data to Earth from significant distances; lightweight and efficient solar array panels; lightweight, high-output battery cells; a miniaturized heat transport system; lightweight yet strong composite materials for nano-satellite and deployer-ship structures; and simple, reusable ground systems.

Performance analysis of heat pipe micro-reactor with Stirling engine based on full-scope multi-physics coupled simulation

Heat pipe micro-reactors (HPMRs) with Stirling engines for power conversion are emerging as a promising surface power technology. We developed a comprehensive multi-physics solver using the open-source finite-volume code OpenFOAM to perform high-fidelity analysis of HPMR systems’ steady-state and dynamic performance. The solver couples a 3D coarse-mesh multi-group neutron diffusion model with a 3D fine-mesh thermal conduction model using a mapping approach to accurately simulate multi-physics phenomena in the reactor core. Additionally, it integrates a 2D high-temperature heat pipe model as boundary conditions for heat transfer in the core, a 1D Stirling engine model for energy conversion, and a lumped parameter radiator model for heat dissipation. Applied to the HOMER-15 reactor system, the solver aided to identify the optimal working point of the system, achieving 3 kW of electric power with a conversion efficiency of 25.2 % under 20-Hz Stirling engine frequency and 3.34-MPa pressure. The transient full-scope simulation with the solver shows that the load-follow strategy based on gas charging and venting in Stirling engines is capable to accommodate 35 % step increase of external load. When the unexpected reactivity insertion is within 0.1$, the peak temperature in the reactor core is below the allowable limit temperature. Analysis of single failure of Stirling engines indicates that the system safety and reliability can be enhanced by either incorporating an appropriate number of engines or enhancing heat transfer between Stirling engine channels.

Investigation on thermal response of high temperature heat pipe under thermal mismatch conditions

As an efficient and reliable passive heat transfer equipment, high temperature heat pipes (HTHPs) plays an important role in HTHP solid state reactor system. HTHPs often encounter thermal mismatch in reactor applications, which will lead to capillary action, entrainment, and other characteristics, resulting in HTHP failure due to heat transfer limits. In this paper, the thermal response test of liquid metal HTHP under thermal mismatch conditions is studied, and the simulation test platform of HTHP mismatch is designed and built to measure the important physical parameters. The test results show that the heat transfer performance of the HTHP is the best under the condition of horizontal inclination of 60°, and the condenser power is 5.66 kW. This condition is selected as the reference condition for the transient condition test. When the HTHP experienced a transient power increase, the middle of the evaporator section, as the part with the largest heat flux of heating power, appeared a severe overheating phenomenon. The wall temperature of the evaporator section soared from 750 ℃ to 1050 ℃ in a short time, and the heating rate reached 18.9 ℃/min, which affected the smooth operation of the HTHP. When the HTHP encounters an inclination angle transient increase condition, the entrainment phenomenon is more severe, the temperature fluctuation of the condenser section is intensified, and the heat transfer of the HTHP is in an unstable state. When the HTHP encounters an inclination angle transient decrease condition, the temperature rise of the evaporator section is less than 10 ℃, the temperature at the end of the condenser section is increased, and the start-up performance of the HTHP is improved. In summary, this paper obtains the thermal response rule of HTHPs under thermal mismatch conditions through experimental research, which provides support for the safe application of HTHPs for special equipment.

Carbon black densified matrix graphite to enhance its anti-infiltration capability against molten salt

A novel graphite matrix was prepared by adding carbon black (CB) as a densification agent to traditional matrix A3-3 graphite preparation. The particle size of CB densifier we chose was approximately 50–150 nm, which was smaller than the pore diameter of densified matrix graphite (500-1000 nm). Five different mass fractions of CB were mixed and compared with as-received A3-3 by various characterization methods, which indicated that CB can effectively fill the pores of A3-3 and improve its anti-infiltration capability against molten salt (fluoride salt for molten salt reactor and heat storage salt). Meanwhile, considering the requirements for A3-3 graphite in scenarios of solid fuel molten salt reactor and thermal energy storage system, all the samples were compared as well before and after purification. The results showed that purification treatment resulted in slight increase of the pore size and open porosity of graphite and thus weakened its anti-infiltration capability against molten salt, but the thermal properties of graphite improved inversely. However, the addition of excessive CB could cause the significantly decline of thermal properties of A3-3. Comprehensively considering the anti-infiltration effect and requirements of thermal properties, adding 5 % CB was the most preferrable choice for the matrix graphite before and after purification.

Using phragmites australis biochar bio-augmented with actinomycetes for enhancing UASB reactor performance: A field study

Anaerobic processes are a cost-effective and sustainable method for wastewater treatment due to their lower energy demand and potential for biogas-high methane recovery. The up-flow anaerobic sludge blanket reactor system (UASB) is a commonly used technology. This study aimed to evaluate the performance of UASB reactors for handling the wash water from the buffalo shed, with a comparison of traditional UASB to UASB modified reactor by incorporation of immobilized biochar with and without bioaugmentation of a bacterial species with documented anaerobic capabilities. The investigation was conducted as a pilot project at the Suez Canal University Veterinary Experimental Farm in Ismailia, Egypt. Adding Streptomyces hydrogenans S11-immobilized Phragmites australis biochar to the USAB reactor increased removal efficiency, even at high influent loadings. The findings demonstrated that the traditional UASB reactor attained removal efficiency for COD, BOD5, TSS, TDS, color, and turbidity of 81.0 %, 75.0 %,80.0 %, 80.0 %, 70.0 %, and 70.0 % respectively, and biogas production of (0.025 mL biogas/mg COD removed).In comparison, the modified UASB reactor attained COD, BOD5, TSS, TDS, Color, and Turbidity removal efficiencies of 93.0 %, 91.5 %,90.3 %, 91.10 %, 85 %, and 80.0 %, respectively. The biogas production reached (0.037 mL biogas/mg COD removed). The removal efficiencies of the measured parameters were statistically analyzed, and this analysis indicated that the efficiency of the modified reactor was enhanced dramatically compared to the traditional system. Hence, this work demonstrates an efficient approach for treating buffalo wastewater.

Novel methodology for targeting the optimal reactor and operating parameters based on the chemical system’s overall performance within catalyst lifecycle

Catalyst deactivation affects chemical system performance and reactor operation. A systematic method is proposed for targeting the optimal reactor, operating parameters, system performance, and catalyst service life, considering the catalyst deactivation. Relations between reactor performance, operating parameters, and running time are clarified based on the coupling analysis of the reactions, catalyst deactivation kinetics, and mass/energy balance. The influence of reactor fluctuation on energy cost and product output is explored by topological analysis, pinch analysis, and algebraic reasoning. A reactor-separator-heat exchanger network coupling frame is established to predict system performance and guide the reactor selection, catalyst regeneration, and system adjustments. The proposed method is intuitive and efficient and can be applied in the preparatory/operation stage. For the studied benzene hydrogenation process, the Plug Flow Reactor is suitable; the catalyst’s optimal service life is 2.08 y, achieving 4.4 % and 4.8 % decreases in annual cost and energy demand/carbon emission by real-time adjustments.

Sustained energy generation from unusable waste steel through microbial assisted fuel cell systems

In the present study, a novel green energy generation process assisted with Microbial Fuel Cell (MFC) principle for generation of electricity from used or wasted steel is explored. Through a unique approach, unused and other steel waste are recast by simple re-melting with a flexible wide composition for generation of green energy. A microbial-assisted electron transfer derived from the degradation of the steel material is utilized for production of green energy in a microbial galvanic reactor system. A. ferrooxidans acts as biocatalysts, facilitating the oxidization of ferrous ion (Fe2+) to ferric ion (Fe3+). The reaction takes place on the biofilm matrix which results in oxidised reactive zones that endorses further degradation or dissolution of Fe anode. This consequently results in achieving the highest power density as high as 4.92 ± 0.03 mW/cm2 at a current density of 0.01 ± 9 mA/cm2. The total cost of the unusable steel anode and other accessories are roughly estimated to be 7.94 $/m2 and 178.54 $/m2 and the gain from unit power generation is estimated to be 3.79 $/W, assuming continuous operation of 4.92 ± 0.03 mW/cm2. The present study presents a potent methodology/strategy for the generation of sustainable bioenergy from low-cost, unusable steel materials, which cannot be anyway used as such in other battery systems, say iron air cells/batteries.

Improving in-situ biomethanation of sewage sludge under mesophilic conditions: Performance and microbial community analysis

This research investigated the application of in-situ biological hydrogen methanation within a continuous stirred tank reactor (CSTR) system under mesophilic conditions, with sewage sludge used as the substrate. Two CSTRs with an effective capacity of 5 L were installed and loaded with inoculum sludge with a volatile solid (VS) concentration of 1.2–1.5 %. They were fed mixed waste sludge with an organic loading rate (OLR) of 1.5 g VS/L and an average sludge retention time (SRT) of 19 days under mesophilic conditions at 37 °C. One of the reactors operated as a control, while the other was injected with H2 through a microceramic membrane diffuser with a H2:CO2 ratio of 4:1. The results of this study revealed that the addition of H2 and the recirculation of residual hydrogen in biogas led to a substantial increase in the production of methane from 157 L/kg VS to 275 L/kg VS. Increasing the methane content in biogas from 52 % to 78 % yielded an impressive 42.8 % higher methane production rate. Metataxonomic analysis of the microbial community via high-throughput sequencing techniques revealed that the dominant acetoclastic and hydrogenotrophic methanogens were Methanosaeta and Methanoregula, respectively, with greater abundances of both groups in the experimental bioreactor. The dynamics of their activity in both bioreactors were analyzed via qPCR, and the functional genes encoding methyl-coenzyme M reductase (mcrA gene) and hydrogenase Ni-Fe presented comparable changes between RI and RII. By optimizing key operational parameters and closely examining the dynamics of the microbial community, this approach can contribute significantly to sustainable bioenergy solutions while minimizing environmental impact.

Evaluating sustainable energy pathways: Economic perspective on advanced hydrogen production

This investigation seeks to evaluate hydrogen generation technologies in China with a focus on two commercial processes, namely hydrothermal oxidation and supercritical water gasification of organic waste from 2011 to 2021. This period witnessing major development, and highlight the key determinants of hydrogen production. The present study was mainly concerned with the enhancement of SCWG processes for hydrogen generation from microalgae and other potential feedstock. Some of the significant observations made in this period are the critical role of biomass composition, choice of catalyst, and operating conditions in increasing H-producing capabilities of reactor systems. The authors of research affirm that the feedstock with a high carbohydrate content and low levels of protein are the most suitable for hydrogen generation. Thus, expanding research on Supercritical Water Gasification, there is the development of HTO methods to consider various pathways of hydrogen production and their connection with existing energy networks. It also studied the effects that several types of catalysts embracing the heterogeneous transition metals and the homogeneous alkali metal compounds have on the efficiency of hydrogen production. These changes have rendered the hydrogen generation process to make more precise predictions and/or course corrections on the process. The studies that have been done between 2011 and 2021 show significant improvements in the ways that sustainable and efficient hydrogen generation technology can be created in China. The results provide a solid platform for future improvements and stress positive impacts that can be provided by these technologies for China's sustainability and energy transition progress.

Improved intelligent model predictive controller for the nuclear power reactor system

Abstract Over the last two decades, extensive research has been conducted to enhance the control performance of reactor power. Various methodologies have been suggested and implemented to achieve optimal power control in nuclear reactors. However, due to the diverse characteristics and inherent uncertainties in the models, devising optimal controllers for nuclear systems remains a complex task. To address this, numerous approaches have been adopted to ensure controllability and resilience, aiming for an optimal nuclear power reactor controller. The Model Predictive Control (MPC) algorithm has garnered significant attention as a viable approach to boost operational efficiency and overall system utility. In this research, Particle Swarm Optimization (PSO) method and MPC controller are combined together to form a novel algorithm termed PSO-MPC, aiming to amplify the system’s performance and overcomes the local minima problem that basically happens when using MPC controller. First, MPC controller is applied to the nuclear reactor model, then the suggested technique PSO-MPC also is applied to the system and a comparison of the outcomes using both techniques is done. The results demonstrate enhanced system response using the innovative technique.

A robust floating oxygen-doped graphitic carbon nitride sheet for efficient photocatalytic CO2 conversion

Photocatalytic CO2 reduction offers a promising approach for converting CO2 into valuable chemicals. However, typical conversion systems suffer from inefficient CO2 mass transfer and complex recycling processes. In this study, we developed a floating sheet as a robust photocatalytic CO2 conversion system by integrating graphitic carbon nitride (CN) nanosheets onto polytetrafluoroethylene (PTFE) fiber membrane, followed by oxygen (O) doping into the CN (CN-O) via oxygen-plasma treatment. The floatable CN-O/PTFE sheet exhibits slight wettability in water under 0.25 MPa of CO2 pressure in our reactor system, facilitating the delivery of dissolved CO2 to the CN-O photocatalyst surface. O-doping enhances the visible light absorption and improves the separation and transport efficiency of photogenerated electrons and holes due to O-doping-induced states in CN. Consequently, the floating CN-O/PTFE system achieves an exceptional photocatalytic CO2 conversion rate of 102.3 μmol g-1h-1, approximately 4.8 times higher than a conventional CN-powder dispersion system in water. Moreover, the sheet demonstrates excellent cycling durability, with no significant exfoliation of the catalytic layer or reduction in CO2 photoreduction activity after 20 consecutive cycles. This study presents a novel approach to designing photocatalytic systems for efficient CO2 conversion.

Enhanced Production of Furfural via Methanolysis of Wood Biomass with HCl Gas.

This study explores the production of furfural, xylose and methylxylosides through the methanolysis of wood flour using anhydrous HCl gas. The process involves methanolysis of wood flour with HCl gas under pressure to generate methylxylosides, which are subsequently converted to xylose and furfural via autohydrolysis in a Parr batch reactor system. The methanolysis was conducted in temperature-controlled HCl gas reactor employing 24 h reaction time and 50 % methanol content in wood flour. During the methanolysis step with HCl gas, 65 % of the available xylan in wood flour was converted to water-soluble methylxylosides, xylose, xylooligosaccharides (XO) and water-soluble methyl xylooligosaccharides (MXO). Methanolysis filtrates were then autohydrolyzed with Parr 50 mL batch reactor system to xylose and furfural in two different pH values at 180 °C. The highest furfural yield of 91 % from methanolysis filtrate was achieved with pH 1.2 and 25 min reaction time.

Adaptive Robust Control of Nonlinear Constrained Stirred‐Tank Reactors via Self‐Organizing Fuzzy Neural Network

ABSTRACTThis paper presents an adaptive robust constraint controller for a continuous stirred tank reactor (CSTR) system based on a self‐organizing fuzzy neural network (SOFNN). Due to the high complexity of the chemical reactions, the CSTR system contains many strong nonlinearities and uncertainties. This is the first time to introduce the SOFNN into the adaptive controller design of the CSTR system, which improves the adaptability to dynamic system changes through the adjustment of the fuzzy network structure. Meanwhile, the time‐varying integral barrier Lyapunov functions (TVIBLFs) are employed to ensure the dimensionless reactant concentration and mixture temperature within a reasonable scope, which can improve the stability and safety of the CSTR system. Based on Lyapunov stability analysis, all the signals in a closed‐loop system are ultimately bounded. Simulation results substantiate the efficacy of the proposed control scheme.