Chemical Reactor Research Articles

Modeling of wavy water film by application of artificial neural network - a state of art study

Nowadays, artificial intelligence (AI) tools have attained a state of maturity and have advanced at a quick rate of achievement in various fields of study. Thus, the predictive and classification of artificial intelligence AI capabilities in manufacturing, commercial, and scientific research applications have resulted in remarkable success. It is widely known that two-phase flow is such a complex problem, and it has a vital state of study due to its importance and wide range of applications. Such as water film phenomena are critical for various industries, including nuclear protection, energy generation, absorption processes, internal combustion engines, chemical reactors, and spray cooling. The present study presented a realistic model for a particular two-phase flow problem of water film thickness. Also, we used neurotic networks for prediction and classification, such as the conventional neural network (CNN) and Long Short-Term Memory (LSTM). The proposed model was evaluated using various raw data, including the input liquid Reynolds number, the Reynolds gas number, the angle of inclination, and the thickness of the water film. The water film thickness was determined using a planar laser-induced fluorescence (PLIF) technique on the various inclination platforms. The current experimental work's inclination angle varied between 0 and 50 degrees. However, when the Reynolds number of the input water changed from 175 to 435, the thickness of the water film was determined; Reynolds gas numbers range from 6950 to 34800.The current study findings indicate an effective alternative method for detecting and forecasting water films on a sloping plate. Nash-Sutcliffe Efficiency (NSE) affected 99 %, 97 %, and 94 % of forecasts, respectively. The findings show tremendous improvement when deep learning uses both LSTM and CNN. The gravitational pressure and air share tension push the water film.

A reduced order sulfuric acid decomposition model for a nuclear-powered hybrid sulfur cycle

A reduced order model of sulfuric acid decomposition within a bayonet chemical reactor was developed to support the U. S. Department of Energy Integrated Energy System program, and address the lack of knowledge in scaling and integration for joint chemical and nuclear processes. Sulfuric acid decomposition within a bayonet reactor was modeled to provide chemical and thermodynamic data relevant to advanced nuclear reactor-driven integrated energy systems based on desired operational scale and operational conditions. The temperature range required for high-temperature advanced nuclear reactor integrated energy systems, 750-850 °C, was shown to produce reasonable agreement (within a few percent relative error) with past models and experimental data, and yielded good efficiency results for bayonet reactor operations. The results of the reduced order model agreed with previous work from Savannah River National Labs within a maximum of 3.4% error on the decomposition of sulfur trioxide, and on previous Hybrid Sulfur flowsheets from Gorensek and Summers that showed operational temperature, pressure, and composition ranges for efficiency which made the Hybrid Sulfur cycle competitive with water electrolysis. The agreement with previous high-fidelity models provided a framework for future Integrated Energy System grid evaluations with an advanced nuclear reactor and large-scale hydrogen production using a mathematical model to represent chemical operations.

Design of sustainable reactor based on key performance indicators

The design of chemical reactors has been largely considered primarily related to techno-economic evaluations. However, the recent need for sustainable solutions and processes has promoted the inclusion of environmental and safety parameters to identify the most suitable solution. In this sense, an innovative procedure has been developed in this work to identify and design a reactive section in chemical processes. To this aim, different key performance indicators have been defined and quantified for each domain considered within the analysis, namely technological, economic, environmental, and safety domains. In addition, the safety aspects have been quantified by integrating Semenov’s theory and Varma, Morbidelli and Wu's theory. The validity and potentiality of the proposed procedure have been tested and shown by applying it to a case study representative for the scale-up of pharmaceutical processes: the industrial synthesis of a Vitamin A intermediate. A preliminary design has been performed for different configurations based on apparent kinetics determined from experimental data and ab initio coefficients available in the current literature. Among the analysed solutions, a single reactor with a volume of 15.90 m3 has been indicated as the most suitable for the process requirements regarding overall sustainability. Hence, the developed procedure can be intended as a powerful tool for screening among available configurations, enabling a more informed decision by simplifying and optimising the scale-up and the detailed design.

Tandem Electro‐Thermo‐Catalysis for the Oxidative Aminocarbonylation of Arylboronic Acids to Amides from CO2 and Water

AbstractDirect CO2 electroreduction to valuable chemicals is critical for carbon neutrality, while its main products are limited to simple C1/C2 compounds, and traditionally, the anodic O2 byproduct is not utilized. We herein report a tandem electrothermo‐catalytic system that fully utilizes both cathodic (i.e., CO) and anodic (i.e., O2) products during overall CO2 electrolysis to produce valuable organic amides from arylboronic acids and amines in a separate chemical reactor, following the Pd(II)‐catalyzed oxidative aminocarbonylation mechanism. Hexamethylenetetramine (HMT)‐incorporated silver and nickel hydroxide carbonate electrocatalysts were prepared for efficient coproduction of CO and O2 with Faradaic efficiencies of 99.3 % and 100 %, respectively. Systematic experiments, operando attenuated total reflection surface‐enhanced Fourier transform infrared spectroscopy characterizations and theoretical studies reveal that HMT promotes *CO2 hydrogenation/*CO desorption for accelerated CO2‐to‐CO conversion, and O2 inhibits reductive deactivation of the Pd(II) catalyst for enhanced oxidative aminocarbonylation, collectively leading to efficient synthesis of 10 organic amides with high yields of above 81 %. This work demonstrates the effectiveness of a tandem electrothermo‐catalytic strategy for economically attractive CO2 conversion and amide synthesis, representing a new avenue to explore the full potential of CO2 utilization.

A Nobel Variation of 16th-Order Iterative Scheme for Models in Blood Stream, Chemical Reactor, and Its Dynamics

A Nobel Variation of 16th-Order Iterative Scheme for Models in Blood Stream, Chemical Reactor, and Its Dynamics

Revealing the origins of vortex cavitation in a Venturi tube by high speed X-ray imaging

Hydrodynamic cavitation is useful in many processing applications, for example, in chemical reactors, water treatment and biochemical engineering. An important type of hydrodynamic cavitation that occurs in a Venturi tube is vortex cavitation known to cause luminescence whose intensity is closely related to the size and number of cavitation events. However, the mechanistic origins of bubbles constituting vortex cavitation remains unclear, although it has been concluded that the pressure fields generated by the cavitation collapse strongly depends on the bubble geometry. The common view is that vortex cavitation consists of numerous small spherical bubbles. In the present paper, aspects of vortex cavitation arising in a Venturi tube were visualized using high-speed X-ray imaging at SPring-8 and European XFEL. It was discovered that vortex cavitation in a Venturi tube consisted of angulated rather than spherical bubbles. The tangential velocity of the surface of vortex cavitation was assessed considering the Rankine vortex model.

Electrochemical Residence Time Distribution as a Diagnostic Tool for Redox Flow Batteries

The fluid dynamic and electrochemical performance of redox flow batteries (RFBs) stems from the relationship between the flow field and the porous electrode, whose interplay determines how active species move and react during device operation. While characterization techniques, such as residence time distribution, offer insights into species mobility within a reactive volume for a traditional chemical reactor, electrochemical reactors also enable simultaneous measurement of the redox reactions, unlocking another dimension of analysis. Herein, we demonstrate how potentiodynamic measurements, using injections of electrolyte examined through moment analysis, can provide electrode-specific performance scaling relationships across a matrix of carbon paper and cloth electrodes with flow through and interdigitated flow fields. We further combine experimental campaigns with multiphysics simulations to demonstrate how electrode surface area can be estimated with this technique, which we then validate with activated and unactivated commercial carbon cloth electrodes. These studies reveal the multiscale observations that potentiodynamic measurements afford, augmenting existing electrochemical techniques for holistic electrochemical reactor diagnostics.

Numerical Insights Into Gas Mixing System Design for Energy Conversion Processes

Abstract Uniform gas mixing is important in various scientific and engineering domains, particularly in a chemical reactor design employing pre-mixed gases for processes. Assessing the performance of different mixer designs through physical prototypes can be resource-intensive and time-consuming. Consequently, this study underscores the significance of numerical simulations to optimize gas mixing and distribution systems in energy conversion applications. The research primarily focuses on varying the base mixer geometry by modifying the configuration of cross-flow inlets alongside the chambers. By employing numerical simulations, critical factors influencing mixing uniformity are identified, and innovative solutions are proposed to enhance system performance. Additionally, this work extends its application to improving the operational conditions of an industrial biomass gasifier, underlining the practicality of numerical modelling in addressing complex engineering challenges.

Fuzzy-based adaptive event-triggered control for nonlinear cyber-physical systems against deception attacks via a single parameter learning method

This paper investigates the adaptive fuzzy control issue of cyber-physical systems (CPSs) against unknown deception attacks and external disturbance. Based on the backstepping design framework, the uncertainty term composed of the approximation error term generated by the fuzzy logic system, the external disturbance and the deception attack signals are regarded as a whole in the recursive design process. Then, by combining the single parameter learning method with the adaptive fuzzy technique, the uncertain terms containing approximation error, disturbance and injection attacks can be transformed into the form of linear parameterization with only one unknown scalar parameter, which greatly reduce the calculation process. In addition, the dynamic event-triggered adaptive control technology can be integrated into the control design to reduce the amount of data transmission. Theoretical analysis shows that all the signals in the closed-loop system are bounded under the proposed control scheme, and the Zeno behavior is excluded. Finally, the two-stage chemical reactor and mass-spring-damper systems are employed to demonstrate the validity of the proposed adaptive fuzzy control solution.

Application of Smart Overpressure Protection Devices to batch and semi-batch processes: The zero-emission mode

Chemical reactors in batch- and semi-batch processes are mainly protected by mechanical safety devices or safety integrity systems against critical runaway reactions. Both devices have in common, to limit with their fixed set conditions and discharge areas the productivity and flexibility of chemical plants. Besides, the trend in the industry is to reduce/avoid toxic and explosives to be discharges trough safety devices due to the increased requirements for climate- and environmental protection. A new idea in that regard is to connect the advantages of mechanical safety devices and safety integrated systems in so called smart overpressure protection devices (SmOP). Here, a predictive CSE conversion model (PreCoM) is online tracking the hazard potential of a chemical reaction and defines individual shutoff limits for the reaction. Its zero-emission mode ensures flexible, reaction independent application without fluid discharge. The smart relief mode is maximizing the plant utilization with individual shutoff limits and is minimizing the pollution with controlled discharge areas. In this article, the SmOP concept and the utilization of the PreCoM model for two different reactions and three industrial use cases for zero-emission application is being presented.

Fluid Flow in Helically Coiled Pipes

Helically coiled pipes are widely used in many industrial and engineering applications because of their compactness, larger heat transfer area per unit volume and higher efficiency in heat and mass transfer compared to other pipe geometries. They are commonly encountered in heat exchangers, steam generators in power plants and chemical reactors. The most notable feature of flow in helical pipes is the secondary flow (i.e., the cross-sectional circulatory motion) caused by centrifugal forces due to the curvature. Other important features are the stabilization effects of turbulent flow and the higher Reynolds number at which the transition from a laminar to a turbulent state occurs compared to straight pipes. A survey of the open literature on helical pipe flows shows that a good deal of experimental and theoretical work has been conducted to derive appropriate correlations to predict frictional pressure losses under laminar and turbulent conditions as well as to study the dependence of the flow characteristics and heat transfer capabilities on the Reynolds number, the Nusselt number and the geometrical parameters of the helical pipe. Despite the progress made so far in understanding the flow and heat transfer characteristics of helical pipe flow, there is still much work to be completed to address the more complex problem of multiphase flows and the impact of pipe deformation and corrugation on single- and multiphase flow. The aim of this paper is to provide a review on the state-of-the-art experimental and theoretical research concerning the flow in helically coiled pipes.

Detailed numerical investigations of the in operando adjustable flow field in a diamond unit cell-based interpenetrating periodic open cellular structure (interPOCS)

In the field of heterogeneous catalysis, additively manufactured so-called Periodic Open Cellular Structures (POCS) applied as catalyst supports have demonstrated their advantages over conventional randomly packed bed reactors in terms of heat management and pressure drop (Busse et al., 2018; Inayat et al., 2016). Since the internal flow field and the pressure drop are mainly influenced by the geometrical properties of the unit cell (unit cell type, strut diameter and cell size), the resulting transport characteristics of the structure is already determined during the design phase of the unit cell (Horneber, 2015). By inserting one POCS based on a diamond unit cell (offset structure) into the cavities of a second diamond cell structure (fix structure), a completely new type of so-called interpenetrating Periodic Open Cellular Structures (interPOCS) is formed which allows for an in operando adjustment of the global and local morphological properties of the structure (Do et al., 2017; Do et al., 2020). With detailed, spatially resolved computational fluid dynamics (CFD) simulations using the open source toolbox OpenFOAM® (Weller et al., 1998) and an additional in-house random-walk particle tracking implementation called disTrackFoam (Trunk et al., 2021), we systematically investigated the local and global flow characteristics within the interPOCS in dependency of the relative positioning of the fixed and offset structure. The obtained results show that this highly adjustable structure allows for a broad variation of flow characteristics in a chemical reactor without changing the system’s periphery. This study demonstrates that interPOCS represent a completely new application of additively manufactured catalyst support structures enabling highly flexible in operando tuning of the flow field and mass transport in a heterogeneously catalyzed reactor system.

A practically implementable reinforcement learning control approach by leveraging offset-free model predictive control

This work addresses the problem of designing an offset-free implementable reinforcement learning (RL) controller for nonlinear processes. RL-based controllers can update the control policy using observed data obtained online based on the controller-process interactions. This allows to alleviate the regular model maintenance step that is essential in advanced control techniques such as model predictive control (MPC). However, random explorations are required for an RL agent to find optimal state–action regions so as to finally reach the optimal policy. This is not implementable in practical situations due to safety concerns and economic objectives. To address this issue, a pre-training strategy is proposed to provide a secure platform for online implementations of the RL controllers. To this end, an offset-free MPC (representative industrial MPC) optimization problem is leveraged to train the RL agent offline. Having obtained similar performance to the offset-free MPC, the RL agent is utilized for online control to interact with the actual process. The efficacy of the proposed approach to handle nonlinearity and changes in plant operating conditions (due to unmeasured disturbances) are demonstrated through simulations on a chemical reactor example for a pH neutralization process. The results show that the proposed RL controller can significantly improve the oscillatory closed-loop responses, obtained by running the offset-free MPC due to the plant-model mismatch and unmeasured disturbances.

Effective diffusional limitation modeling of a heterogeneous reaction system for computational fluid dynamics application

Diffusional limitation of heterogeneous reaction catalysts is typically fitted or over-generalized without considering the catalyst’s physical parameters upon conducting computational fluid dynamics (CFD) analysis of an industrial-scale chemical reactor. Fitting and over-generalization are done to meet computational cost constraints. However, this reduces the reliability of local thermodynamic state analysis and application of calculated results. This study proposes an effective catalytic diffusion-limited model for reliable and cost-effective three-dimensional CFD simulations to overcome such difficulties. The proposed model utilizes simplified equations to compute the diffusional limitation by incorporating the physical parameters of the catalyst. The model is validated using Ni-based cylindrical catalyst pellets for steam–methane reforming and ammonia decomposition reactions, with in-house experiments supporting the fidelity of the model. For practical implementation, the model is applied to three-dimensional CFD simulations of a commercial-scale solid oxide fuel cell (SOFC) hotbox housing a large-scale reformer. Furthermore, a parametric study for inlet gas temperatures and catalyst size is carried out, which provides useful insights into how operating conditions and catalysts affect the transport phenomena and local thermodynamic state of the SOFC hotbox. Consequently, the practicality and versatility of the presented model are established through experiments and simulations.

Mitigation of PWR fuel assembly vibrations using bio-inspired nozzles

Jet flows injected in a transverse flow need rapid and effective mixing for various applications ranging from medicine injection into bloodstreams to nuclear pressurized water reactors (PWRs). Inspired by marine organisms, spiral snails, and sharks, bio-inspired nozzles are proposed and experimentally investigated to explore their advantages in suppressing nuclear fuel assembly vibrations. It has been observed that a combination of axial flow and jet cross-flow causes vibrations of fuel rods and potential wear at spacer grid supports. Marine biomimetics is used to improve the mixing between the jet flow and surrounding fluid flows. Inspired by the structure of gastropod shells, a variable whorl spacing nozzle is proposed to induce a swirling jet flow to enhance the mixing rate with the flow inside the reactor cores. In addition, the smooth maneuverability of the sharks highlights the importance to include gill slits structure into nozzles. This work focuses on mitigating PWR fuel assembly vibrations using two biomimetic nozzles, a snail nozzle and a shark nozzle. These two nozzles are proposed to improve the mixing rate between the injected flow and the primary coolant flow, resulting in a reduced jet flow effect on fuel rods. A single-span mock-up PWR array is designed, fabricated, and instrumented to mimic the real nuclear fuel assembly. The array is experimentally tested under combined axial flow and jet cross-flow to investigate its dynamical behavior. Three different nozzles, a basic circular nozzle, a snail nozzle, and a shark nozzle, are tested. The research investigates the ability of the proposed marine biomimetic nozzles to suppress the vibration of the rod bundle by comparing the results from the three tested nozzles. The obtained results suggest that the proposed snail-inspired biomimetic nozzle is significantly better than the circular nozzle since it reduces rod bundle vibration by increasing flow mixing. A 50% reduction was achieved by implementing it instead of the circular nozzle. More importantly, the shark-inspired nozzle delays the critical jet flow rate, at which the unstable vibration occurs in the rod bundle, by 20%. In addition to delaying instability, a vibration amplitude reduction of 87.5% was obtained using the proposed shark-inspired nozzle compared to the circular nozzle. The results are promising for various applications including gas burners, combustion chambers, and chemical reactors for providing efficient and rapid mixing between two fluid streams.

Исследование устойчивости химического реактора полимеризации этилена

The chemical reactor is the main and most complex object in the management of the technological process of polymerization. When designing chemical reactors, it is necessary to select design and operating parameters that will be able to provide the only or most stable state with the specified process characteristics. To study the stability of the ethylene polymerization process in an autoclave reactor with a stirrer, it is necessary to build a mathematical model based on the analysis of the physico-chemical laws of the process and search for the necessary steady-state conditions for the reactor. A solution based on a deterministic mathematical model of ethylene polymerization is proposed. The description of the process of polymer molecule formation, which includes the stages of initiation, growth and chain breakage; the mechanism of chemical kinetics of ethylene polymerization; a system of assumptions to simplify the construction of a mathematical model. The mathematical model of an ethylene polymerization reactor in an autoclave reactor with a stirrer is a system of differential equations. When calculating the static reactor mode, the mathematical description contains a system of nonlinear algebraic equations, the solution of which is implemented using numerical methods. It is noted that chemical reactors can have not one, but several stationary states at the same values of variables and parameters. Knowing the coordinates of the stationary states of the chemical process, you can choose the one that is more preferable from the point of view of productivity or the quality of the products produced. As a result of the simulation, the existence of a single solution under the conditions found that ensure a stable stationary state of the chemical ethylene polymerization reactor is confirmed.

A method of suppressing chaos in a chemical reactor and the use of chaos for identifying the reactor model

A method of suppressing chaos in a chemical reactor and the use of chaos for identifying the reactor model

Determination of Hopf bifurcation sets of a chemical reactors by two-parameter continuation method

Determination of Hopf bifurcation sets of a chemical reactors by two-parameter continuation method

Bottom up anatase monodisperse nanoparticles grown on sepiolite showing high thermal stability and optimal optical properties for self-cleaning applications

Powder samples of anatase monodisperse nanoparticles (np's) have been in-situ synthesized from sepiolite microparticles doped with TiIV. The role of this clay is double, by one hand, it acts as a chemical reactor, and on the other hand, it becomes a solid substrate for particles, which pin them up avoiding Ostwald ripening process on heating. In this work we show the high thermal stability of these metastable anatase particles up to 850 °C, around 200 °C above the anatase/rutile transformation for ordinary powder particles. Relevant information about the electron bandstructure has been obtained both, by optical diffuse reflectance and emission spectroscopy, which revealed the nature of photon absorption and recombination around the band-gap which determine the utility of this materials as a self-cleaning agent for solid materials.

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.