Reaction Engineering Research Articles

THE INFLUENCE OF THE CATALYST ON THE RATE CONSTANT OF THE CHEMICAL REACTION OF ESTERIFICATION OF OLEIC ACID WITH METHANOL

Catalysis and catalysts play an important role in modern technology. Catalysis means a change in the rate of a chemical reaction under the influence of a substance that does not change chemically as a result of the reaction. This substance is called a catalyst. The catalyzed reaction proceeds on a different reaction path than the uncatalyzed reaction, thanks to the participation of the catalyst. The reactants are absorbed on the surface of the catalyst, and then a mutual reaction of the adsorbed species occurs. The reaction produc- es a product that is desorbed from the surface, while the catalyst remains unchanged and ready for a new reaction cycle. An important piece of information for evaluating the quality of a catalyst is the rate of the reaction in which it participates. The subject of kinetic research is the study of the influence of process pa- rameters on the reaction rate. It is safe to say that the study of reaction kinetics is a central part of chemical reaction engineering. Therefore, the study of the kinetics of real heterogeneous catalysts is of particular im- portance, both for the improvement of existing catalysts and for the development of new ones. These tests involve determining the influence of process parameters such as the type of catalyst present, temperature, pressure, and concentration of reactants and products on the reaction rate. In this work, the influence of the mass of the catalyst at a certain temperature on the rate constant of the chemical reaction of esterification of oleic acid with methanol was studied. The catalyst used was mesoporous silica, an amorphous solid that can be obtained by drying hydrogels. It was found that as the mass of the catalyst increases, the rate of the chemical reaction constant also increases, i.e. the rate of the esterification reaction increases.

Development and validation of Loss of Coolant Accident (LOCA) simulation capability in the ENIGMA fuel performance code for zirconium-based cladding materials

Loss-of-coolant accident (LOCA) modelling forms a pivotal element in the licensing of light water reactor technologies. Within this context, the National Nuclear Laboratory has further developed its ENIGMA fuel performance code to accurately simulate fuel behaviour during limiting design-basis accidents. The enhanced ENIGMA code now incorporates models for high-temperature cladding creep, cladding oxidation and hydriding at elevated temperatures, cladding phase change, and cladding failure. A detailed examination of existing LOCA-capable models relevant to industrial-standard fuel performance codes was conducted, which led to the introduction of an industrial state-of-the-art capability within ENIGMA for modelling uranium dioxide fuel in various zirconium alloy cladding materials. The efficacy of the enhanced ENIGMA code was validated using data from the IFA-650.10 LOCA experiment carried out as part of the OECD Halden Reactor Project. ENIGMA’s predictions were compared with both the experimental data and predictions of other fuel performance codes from the International Atomic Energy Agency’s Fuel Modelling in Accident Conditions (FUMAC) coordinated research project. The comparison generally showed good agreement, highlighting the effectiveness of the improved ENIGMA code.

Activated carbon supported Ni, Fe, and bimetallic NiFe catalysts for COx-free H2 production by microwave methane pyrolysis

The goal of this study was to test the effect of metal-impregnated carbon-based catalysts on the conversion of methane to hydrogen gas and solid carbon using microwave reactor technology. Monometallic and bimetallic catalysts on activated carbon supports (Ni/AC, Fe/AC, NiFe/AC) are compared during methane pyrolysis testing. Catalytic methane pyrolysis was carried out in a microwave reactor at reaction temperatures of 600 °C and 800 °C. For comparison, one of the catalysts (NiFe/AC) was tested in a conventionally heated reactor at 800 °C. The prepared catalysts were characterized by X-ray diffraction (XRD), while post-reaction catalysts were characterized by XRD and SEM. During reaction testing, the monometallic Ni/AC catalyst exhibited the best catalytic activity (CH4 conversion: 46.0 and H2 yield: 46.9 %) when reacted in the microwave reactor, however, it suffered from rapid deactivation from carbon deposition (carbon yield: 0.39 g C/g catalyst). The bimetallic NiFe/AC catalyst was slightly less active (CH4 conversion: 36.9 and H2 yield: 40.5 %) but it was more resistant to carbon formation (carbon yield: 0.27 g C/g catalyst) suggesting it may have greater long-term stability. The NiFe/AC catalyst was also the most energy efficient as it required the least microwave power to maintain the 800 °C reaction temperature compared to the other catalysts tested. Methane conversion of the bimetallic NiFe/AC at 800 °C under microwave irradiation was three times the conversion under conventional heating at the same reaction temperature. This work demonstrates the use of microwave-specific catalysts for catalytic methane pyrolysis in a microwave reactor, and can be used as a foundation for further methane pyrolysis process and catalyst optimization for COx-free H2 production.

An Approach for Integration of User Requirement and Anthropometry Data in The Process Design of Reactor Main Control Room

The construction of a Nuclear Power Plant (NPP) using Small Modular Reactor (SMR) technology is an interesting scheme to support Net-Zero Carbon Emission. The SMR design is an advanced generation reactor with high safety and utilization features, especially the electricity needed and industry. Its modular size can also be applied to remote areas with lower construction costs compared to other types of power plants. Considering the geographical location and territory of Indonesia which is an archipelagic country, this type of reactor is suitable for application in Indonesia. To ensure safety and increase mastery of technology, it is necessary to create a simulator to support this program. Nonetheless, specific regulations govern human-machine interactions (HMI) which is covering the nuclear reactor simulators in Indonesia is not yet available. The research carried out is a review of the regulations that have been implemented in other countries, then provides a choice of operator condition designs, which are adjusted to the average size of Indonesian by considering anthropometric aspects and ergonomic aspects.

Solving boundary value problems in heterogeneous catalysis with orthogonal collocation and arc‐length continuation

AbstractAn important part of the education of chemical engineers involves the design and assessment of heterogeneous catalytic reactions. They pose fundamental phenomena and constitute invaluable industrial processes. Progressing in this field, especially in graduate‐level courses, entails solving nonlinear differential equations systems, which can only be achieved by using efficient and reliable numerical techniques. In this work, we solve nonisothermal one‐dimensional reaction‐diffusion BVP considering convection in the boundary conditions, by applying orthogonal collocation and arc‐length continuation. Particularly, we predict the effectiveness factor as a function of the Thiele modulus for the main three particle geometries: plane slab, cylinder, and sphere. For chemical engineering students, such problems are at the zenith of the discipline, and the results of such calculations can elucidate basic and advanced concepts of mass and heat transfer as well as chemical reaction engineering. Both Chebyshev and shifted Legendre polynomials were used to transform the boundary value problem into a set of algebraic nonlinear equations. In addition, we also compare our findings against the available analytic solutions whenever possible. Codes in Scilab, Matlab®, and Mathematica© were developed for the solution of such problems and are available in the Supporting Information. There are two possible approaches to compute effectiveness factors: (a) integration as per definition versus (b) differentiation and nonlinear system. It is demonstrable that software performance is dependent on the approach, and that the differentiation approach yields better results.

Comparative study of energy performance and water savings between hygroscopic and rankine cycle in a nuclear power plant. Case study of the HTR-10 reactor

The use of nuclear energy can contribute to achieving positive socio-economic and environmental benefits, but nuclear power plants are one of the most water-intensive industries in the world. The use of Small Modular Reactor (SMR) technologies is increasing due to their interesting advantages such as reduction of construction costs and use in remote areas, which favors distributed generation. Hygroscopic Cycle Technology (HCT) can be of great interest for power generation in nuclear power plants, due to the potential improvement in terms of energy efficiency and water savings. This study presents the benefits of implementing HCT in an existing SMR, the HTR-10, based on the classical Regenerative Rankine Cycle (RRC). The HTR-10 is used to produce electricity and thermal energy for District Heating (DH). Analytical models of both cycles have been developed to compare them in terms of energy production and water consumption. Sensitivity analyses of the influence of the main variables have been performed. The results show that by varying the condensing pressures, the thermal power for DH and the net mechanical power production of the HCT increase up to 2.5 % and 1 %, respectively, with respect to the RRC. The maximum tolerable ambient temperature for the plant with the HCT is 43.12 °C, increasing the availability of the plant and avoiding water consumption between 70000 and 88000 m3/year, depending on the operating conditions. Extrapolation of the results suggests that HCT can improve the energy production of nuclear power plants in a more sustainable way, contributing significantly to the energy transition.

Theoretical Kinetic Study on Hydrogen Abstraction Reactions from n-Pentane by NO2.

The interaction of fuel with NOx chemistry is important for the construction of the reaction mechanism and engine application. In this work, the reaction pathways of nC5H12 + NO2 were studied by high-level electronic structure calculations (DLPNO-CCSD(T)-F12/cc-pVTZ-F12//B2PLYPD3/cc-pVTZ). The rate constants were calculated by using the multistructural canonical transition-state theory with the Eckart tunneling method (TST/MS-T/ET). The studied condition is in a wide temperature range of 298-2400 K. The influence of MS-T anharmonicity and tunneling effect will be clarified for these site-specific H-abstraction pathways. The result reflects the large deviation introduced by the treatment of MS-T anharmonicity, especially at a high temperature. For the same type of reactions, the rate constants of H-abstraction both occurring at the secondary carbon are not almost identical. The branching ratios show that abstraction from the secondary site forming cis-HONO (R2c) contributes 36-78% to nC5H12 consumption in the temperature range of 298-2400 K. The current results show that the multistructural torsional anharmonicity has a crucial influence on the accurate estimation of branching ratios.

Bionic leaf-inspired catalyst bed structure for solar membrane reactor aiming at efficient hydrogen production and separation

Membrane reactor technology permits efficient solar thermochemical conversion at low temperatures, but the performance is often limited by concentration polarization. To cope with the hydrogen (H2) concentration polarization in solar membrane reactors, this study proposes a bionic solar membrane reactor (BSMR) inspired by the excellent production-transport management ability of leaves. Designing the structural parameters of the bionic catalyst bed obtains the efficient BSMR, and mechanistically analyzes its reaction and separation performance enhancement. The results show that the BSMR achieves a synergistic reinforcement pattern of ordered H2 separation driving reaction and reaction providing H2 separation pressure at >90° pore block tilt angle, while large porosity differences and small pore block lengths can further amplify this synergy. Currently, the BSMR with pore blocks of 140° tilt angle, 20 mm length and 0.3 low porosity has the optimal performance, which improves methane conversion and hydrogen recovery by 13.4–99.0% and 13.7–99.0%, respectively, relative to the conventional solar membrane reactor under different operating conditions. Also, it is shown that optimal performance enhancement is achieved at high steam-to-methane ratios, low inlet temperatures and high inlet flow rates. In general, the design referring to leaves makes BSMR well inherit the consistently superior performance of leaves, providing new ideas for efficient hydrogen production and separation.

Advanced development and future of jet engines

An aerodynamic reaction engine, a jet engine, is an internal combustion engine that produces thrust through jet thrust. A jet engine is an important power unit used in aviation and spaceflight, which generates thrust by pushing air in reverse. In recent decades, various developments and improvements have significantly enhanced the efficiency and performance of jet engines. These engines are divided into turbojets, turbojets, turboprops, turboshafts, and ramjets. This article will begin with an introduction to the different types of jet engines and then detail the design, benefits, and issues of the CFM International CFM56/LEAP engine. Finally, there is some description of the future of jet engines, including materials, greater efficiency, and applications in space exploration. The development of the jet engine dates back to the 1930s. British inventor Frank Whittle and German inventor Hans von Ohain developed the first jet engines independently. Jet engines were widely used during World War II and have been continuously improved and developed. The modern jet engine has become the main power unit of commercial and military aviation, and its structure and performance have also been greatly improved.

Simulation of SN transport equation for hexagonal-z reactor using the COMSOL Multiphysics software

Detailed neutron transport simulation has undergone much investigation in advanced reactor engineering, where the adaptability of complex geometrics and the simplicity of computational implementation are of great significance. In this paper, a detailed neutron transport module (DNTM) based on the COMSOL Multiphysics platform is developed for hexagonal-z reactor conditions. The multi-group, multidimensional neutron transport SN equation is discretized using the least-squares finite element method and is embedded in COMSOL using the weak form partial differential equation interface without the necessity for additional coding. The proposed DNTM’s feasibility and accuracy are demonstrated through the analysis of three neutron transport benchmarks, encompassing various energy groups, dimensions, and scales. All the numerical results show good agreement with the reference values, indicating that the proposed DNTM in COMSOL can be used to solve the neutron transport process in the hexagonal-z reactor accurately and reliably. This approach may contribute a simple and practical high-fidelity neutronics solving tool and an effective direction to realize multi-physics tight coupling simulations.

Scope of conceptual development of Resilient supercritical Light water-cooled reactor (SCWR-R)

The research and development (R&D) of Supercritical Light Water-cooled Reactor (SCWR) has been based on the matured Generation III light water-cooled reactor (LWR) technology and the supercritical fossil fuel-fired power plant (SC-FPP) technology. The plant concept has unique features such as the simple and compact plant system and the high thermal efficiency. Currently, the Japanese concepts are being further developed at Waseda University with focuses on improving resilience of SCWR. This study proposes and presents the overall scope of the new Resilient SCWR (SCWR-R) concept with focuses on two viewpoints: (1) SCWR can utilize variety of different core designs ranging from thermal to fast spectrum for multi purposes (e.g., Pu breeding, Minor Actinide burning) with the same plant system to respond to different fuel cycle needs; (2) severe accident management of SCWR-R can be developed with the combination of IVR and PCV with S/C to minimize the PCV internal contamination by radioactive materials, which should greatly reduce post-severe accident management. To establish the SCWR-R concept, the multi-level physics simulation methodology is currently being developed to evaluate the debris criticality, cooling and radioactive aerosol management during the severe accident.

Reaction Engineering and Comparison of Electroenzymatic and Enzymatic ATP Regeneration Systems

AbstractInvited for this issue's Front Cover are the group of Bioprocess Engineering at TU Dortmund University, Department of Chemistry at Johannes Gutenberg University Mainz, and the Biotechnology Group at Constructor University. The front cover illustrates the electroenzymatic regeneration of ATP. The electrons of an enzymatically catalyzed redox reaction necessary for the ATP regeneration cascade are transferred to an electrode mediated by ferrocenyl‐methanol. Regenerative and green energy can therefore be used to drive the reaction. Cover design by Tobias Prenzel and Finn Moeller. Read the full text of the Research Article at 10.1002/celc.202300332.

Front Cover: Reaction Engineering and Comparison of Electroenzymatic and Enzymatic ATP Regeneration Systems (ChemElectroChem 22/2023)

Front Cover: Reaction Engineering and Comparison of Electroenzymatic and Enzymatic ATP Regeneration Systems (ChemElectroChem 22/2023)

A Signal‐To‐Noise‐Ratio‐Based Automated Algorithm to accelerate Kinetic Monte Carlo Convergence in Basic Polymerizations

AbstractKinetic Monte Carlo (kMC) modelling is ubiquitous to simulate the time evolution of (bio)chemical processes, specifically if populations are involved. A recurring task is the selection of the smallest control volume that leads to convergence, which means that the model outputs are accurate and sufficiently free from stochastic noise and do not significantly change upon further increasing this volume. Selecting a too high (safe) control volume leads to an excessive simulation time, while many small incremental control volume increases are inefficient. This work therefore presents an automated tool to determine the smallest control volume leading to convergence. The tool is illustrated for (intrinsic) free radical and nitroxide mediated polymerization (FRP/NMP), in which the chain length distribution (CLD) is a crucial output. The algorithm starts with a very low volume to then check if the desired (monomer) conversion can be reached, the number average chain length is accurate, and finally the signal‐to‐noise (SNR) ratio at the CLD level is below a threshold. The execution time of the algorithm is less than twice the time of running the converged simulation directly, hence, saving tremendous time in setting up a kMC simulation and facilitating benchmark studies even beyond polymer reaction engineering applications.

Product Metrics for the Manufacturability of Single-Crystal Gold Nanorods via Reaction Engineering.

Colloidal gold nanorods (AuNRs) are integral to a diverse array of technologies, ranging from plasmonic imaging, therapeutics, and sensors to large-area coatings, catalysts, filters, and optical attenuators. Different lab-scale strategies are available to fabricate AuNRs with a broad range of physiochemical properties; however, this is achieved at the cost of synthetic robustness and scalability, which limit broad adoption in these technologies. To address this, Product Metrics (Structural Precision, Shape Yield, and Reagent Utilization), measurable with UV-vis-NIR spectroscopy, are defined to evaluate the efficiency of AuNR production. The dependency of these metrics on reaction formulation (reagent concentrations, pH, and T) is established and used to develop a two-step method based on optimizing symmetry breaking of seed particles, followed by the controlled extension of AuNR length and volume. Reagent concentrations and their relative molar ratios with respect to HAuCl4 are adjusted for each step to optimize these adversarial processes. Based on these correlations, we successfully demonstrate the production of highly concentrated AuNRs with targeted volume and aspect ratio while reducing particle impurities and shape dispersity to less than 4 and 10%, respectively, by employing a rationalized formulation that maximizes both product quality and Reagent Utilization. This results in a product density of 1.6 mg/mL, which is 20 times higher than that of conventional literature methods, with commensurate reduction in environmental waste products.

Assessment of Reactor Physics Characteristics of Prismatic Fuel Concepts With a Hydrogen-Based Moderator for Use in a Fluoride Salt-Cooled Small Modular Reactor

Abstract Fluoride-salt-cooled high temperature reactor (FHR) effectively combines the solid fuel and moderator design of high-temperature gas-cooled reactor (HTGR) technology with the fluoride salt coolant (LiF-BeF2, FLiBe) of molten salt reactor (MSR) technology, enabling low-pressure (∼1 atm, 101.325 kPa), and high-temperature (∼700 °C) operations. The design and operational features of the FHR make it a potentially attractive option for a small modular reactor (SMR), provided that it can be modified and made physically small and operate at a low-enough power level (<350 MWth/<150 MWel). Most FHR-SMR designs use high-assay low enriched uranium (HALEU) fuel in the form of tri-structural isotropic (TRISO) fuel particles, combined with the use of a graphite moderator. However, there are alternative design concepts for an FHR-SMR that may offer superior performance characteristics, while utilizing an alternative fissile fuel supply option. In this exploratory study, lattice physics calculations were performed with Serpent to evaluate an alternative FHR-SMR prismatic fuel block design concept using coated annular fuel pellets instead of TRISO-particle fuel compacts, along with the use of hydrogen-based solid moderator rods made of 7LiH. In initial studies, it was found that fuel blocks with 120 moderator rods made of 7LiH tended to have large positive temperature reactivity coefficients (TRCs), which is undesirable for safety reasons. However, reducing the number of moderator rods to 90 or 54, while increasing the number of fuel rods and coolant holes led to low or negative temperature coefficients. For a prismatic fuel block design with 54-7LiH moderator rods, the isothermal temperature coefficient of reactivity (Isothermal TRC), with simultaneous changes in the fuel (F), graphite (G), hydrogen (H), and coolant (C) temperatures, ranges between −0.159 mk/K and −0.054 mk/K, depending on the operating temperature and fuel burnup. Such alternative FHR-SMR fuels could achieve a single-batch core life of ∼10 years with low enriched uranium (LEU) fuel, and ∼45 years with HALEU, in a 350-MWth reactor core.

Application prospect of reaction engineering approach in studying drying behavior of single droplet during spray drying of traditional Chinese medicine

Spray drying technology is one of the most commonly used unit operations in the production of traditional Chinese medicine(TCM) preparations, offering advantages such as short drying time and uniform product quality. However, due to the properties of TCM extracts, such as high viscosity, strong hygroscopicity, and poor flowability, there is limited scope to solve the problems of wall adhesion and clumping in spray drying from the macroscopic perspective of pharmaceutical production. Therefore, it has become a trend to study and optimize the spray drying process from the microscopic point of view by investigating single droplet evaporation behavior. Based on the reaction engineering approach(REA), the single droplet drying system, as a novel method for studying droplets, collects parameter data on individual TCM droplets during the drying process and uses the REA to process the data and establish predictive models. This approach is crucial for understanding the mechanism of TCM spray drying. This paper summarized and analyzed the cha-racteristics of various single droplet systems, the application of REA in single droplet drying systems, and its significance in optimizing the process, predicting drying states, and shortening the development cycle in the field of TCM spray drying, and looked ahead to the prospects of this method, including the introduction of new parameters and imaging techniques, aiming to provide a reference for further research in the field of TCM spray drying.

Simulating the Moisture Diffusion and Evaporation of Sawdust during Convective Drying using the Spatial Reaction Engineering Approach

AbstractThe spatial reaction engineering approach (S‐REA) was used to simulate hot air drying of sawdust. The studies extended the previous work reported in literature where the sawdusts were dried using hot air at 70 °C, 80 °C, and 90 °C. The simulated results were found to agree well with the experimental moisture content (R2 > 0.98) and temperature (R2 > 0.82) profiles. In a further analysis using S‐REA, the spatial profiles of moisture content and vapor concentration were generated to understand better the physics behind. Simulation also revealed that the external mass transfer resistance was more dominant as compared to the internal diffusion resistance. The vapor concentrations were observed peaked at time range of about 10 800– 18 000 s and dropped thereafter upon further heating. This observation could be supported by the variation in the vapor effective diffusivities where peak diffusivity values typically occur after most of the moisture evaporates towards the end of drying.

Thermodynamic Assessment of the NaCl-CrCl2, NaCl-CrCl3, and FeCl2-CrCl2 Pseudo-Binary Systems for Describing the Corrosion Chemistry Between Molten Salt Fuel and Steel

A thorough understanding of the corrosion chemistry between molten salt fuel and structural materials (e.g., steel) is key for the advancement of Molten Salt Reactor technology. In this work, we consider more specifically the case of a chloride fuel salt mixture and the thermochemistry of a salt mixture such as (NaCl-MgCl2-PuCl3) in interaction with (Fe, Cr, Ni). The present work aims at the development of a thermodynamic model of the key subsystems NaCl-CrCl2, NaCl-CrCl3, and FeCl2-CrCl2 to predict corrosion products that may form between molten salt and structural materials. The Modified Quasichemical Model in the quadruplet approximation is used to describe the Gibbs energy of the liquid phase. A critical review of the existing phase diagram and thermodynamic data on theses systems is first presented. To alleviate the lack of data, ab initio calculations coupled with a quasi-harmonic approach are performed to estimate the thermodynamic properties for the intermediate solid compounds Na2CrCl4 and Na3CrCl6, which exist in the NaCl-CrCl2 and NaCl-CrCl3 systems, respectively. These atomistic simulation data together with selected experimental data are then used as input for the thermodynamic assessment of the three subsystems.

Chemical looping process for hydrogen and electricity co-production: Design and operational consideration for moving-bed-reducer-based circulating fluidized bed systems

Chemical looping is an economically advantageous technology for reducing carbon emission from energy, fuels, and chemicals conversion systems utilizing a variety of feedstocks including fossil fuels, renewable materials, and industrial and municipal wastes. Its development relies on two key areas of core competency, i.e., metal oxide reaction engineering, and particle science and technology. The reaction kinetics and the transport phenomena in chemical looping reactors are intrinsically twined with the specific system operational conditions, configuration, and their integration. The optimal design and successful operation of chemical looping systems necessitate a comprehensive consideration of both the reaction rates and multiphase flow characteristics within each reactor. In this article, we analyze the impact of particle hydrodynamic characteristics on optimizing the operational conditions of a syngas-fueled chemical looping (SCL) process, which aims to co-produce hydrogen and electricity. Using this SCL process as an illustrative example, we examine how the particle hydrodynamics influence the system performance and efficiency. The outcome of these effects on the system performance is discussed.