Search

Chemical reactors, heat exchangers, level-loops, and distillation columns are commonly encountered in the chemical process industry, and these are having a significant role in the functioning of any chemical process. For the smooth and efficient functioning of any such process, a robust control law design is an important work to be considered. In this paper, a modified 2DOF robust PID control law has been developed to ensure satisfactory performance in both the step and ramp type references and disturbances. Controller parameters are derived with Maximum sensitivity, Gain, and Phase margin specifications. Case studies with different chemical processes like CSTR, distillation column, heat exchangers, and boiler drum level-loop are included for both the nominal and perturbed cases. Lastly, a performance comparison of ISE (Integral of square error), ITAE (Integral time absolute error), IAE (Integral absolute error), and Total variation (TV) of the control signal is also included. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of determining achievable set‐points for artificial neural network (ANN)‐based model predictive control (MPC) designs. In particular, this work considers a case where a first‐principles model may not be readily available for a nonlinear process, while sufficient closed‐loop data containing possibly correlated outputs is available, such that an ANN‐based model that captures the nonlinear dynamics reasonably well can be identified. The paper addresses implementation aspects with such an ANN‐based MPC design—specifically that of ensuring that achievable set‐points are prescribed to the MPC. The key idea is to perform principal component analysis (PCA) on the training data in order to recognize existing collinearity and determine the upper confidence limit of squared prediction error (SPE) statistic. An optimization problem subject to the SPE constraint is then defined to calculate the achievable set‐points, that can in turn be provided to an MPC design. The efficacy of the proposed approach is illustrated via implementations on a chemical reactor example. The results reveal the superior tracking performance of MPC using the achievable set‐points over the case where arbitrarily prescribed set‐points are used in the MPC implementations. [ABSTRACT FROM AUTHOR]

As a kind of fast and efficient mixing equipment, micromixer has been applied to chemical reaction detection. Its application can not only save experimental samples but also reduce the experimental time. In micromixers, Tesla structure is widely used due to its simple structure and special flow mechanism. In this paper, CFD and response surface method are used to analyze and verify the flow field of the configuration of adding diamond obstacles in the Tesla mixer. The results show that the order of layout parameter weight from large to small is obstacle size > vertical offset > horizontal offset. And the Desirability was 0.806, the optimal diamond obstacle size is 46.35 μm and the optimal lateral offset is 18.78 μm. In addition, a constant value OF 20 μm is predicted as the optimal vertical offset of the micromixer. Compared with the Tesla-type micromixer without obstacles, the diamond-shaped barrier Tesla-type micromixer designed in this paper has higher mixing rate and lower pressure drop under the same conditions, which can be applied to chemical reactors, and can also help to improve the accuracy of chemical reaction. It can be demonstrated that the presented optimal design method of obstacles layout in Tesla mixer is a simple and effective technology to improve the liquid mixing in microfluidic devices, and it has a broad application prospect in chemical engineering. [ABSTRACT FROM AUTHOR]

This paper provides a simple methodology for the design of the air reactor of a chemical looping combustor to optimize its characteristics when it is employed connected to a turbo expander to produce power. The design process, given a certain objective (e.g., electric power) defines the reactor specifics, namely height and diameter, taking into account the following aspects: solids inventory of the air reactor; gas velocity; air reactor transport disengaging height (TDH); solids concentration profile along the reactor height, dense bed height; freeboard height; pressure drop depending on air reactor injectors design and configuration. The total air reactor height was about 9.5 m, while the diameter was about 1.8 m. The total inventory was about 10,880 kg; while the circulation rate in the air reactor was about 110 kg/s. The operating pressure and temperature were, respectively, 12 bar and 1200 °C. The average velocity of the gases inside the reactor was about 4 m/s. The fluidization regime resulted to be comprised between turbulent and fast fluidization. Further work must be directed into the estimate of the pressure drop of the reactor, which will affect the plant efficiency in a considerable way. [ABSTRACT FROM AUTHOR]

The main criteria to be kept in mind while designing any application using fuel cell is the Voltage Control under sudden load variations. As a standard practice the output voltage of a fuel cell is controlled and maintained to the reference by introducing Intelligent Controllers. This paper shows the performance analysis of various intelligent controllers that can track the output voltage of fuel cell. In this paper, the state space model of Proton Exchange Membrane Fuel cell is considered for analyzing various controllers. Additionally the transient response of the fuel cell is analyzed and compared for the different controllers. The performance of the controllers is evaluated by estimating the time response characteristics of the system and also by calculating the system errors. [ABSTRACT FROM AUTHOR]

The hydrogen carrier ammonia is considered a prominent carbon-free alternative fuel. This paper examines the impact of flue gas recirculation (FR) on combustion instability and emission behavior of premixed CH 4 /NH 3 /air swirl flame at different equivalence ratios (Φ) and ammonia mole fractions (χ NH 3 ). Experimental results show that FR is beneficial to suppressing the self-excited pulsating pressure and pulsating heat release rate of CH 4 /NH 3 /air flame, and the pulsating frequency decreases monotonically with the increase of FR. Under fuel-lean and stoichiometric conditions, FR is beneficial to suppressing NOx formation but will increase CO and NH 3 emissions. Under fuel-rich conditions, FR reduces CO emissions but increases NOx emissions. The NO emissions obtained from the chemical reactor network simulation are in qualitative agreement with the experimental results. The results show that the elementary reactions related to HNO and NHi radicals play a crucial role in the influence of FR on NO formation. • Flue gas recirculation (FR) suppresses combustion instability of CH 4 /NH 3 /air flame. • FR decreases NOx emission but increases CO emission under non-rich conditions. • FR increases NOx emission but decreases CO emission under fuel-rich conditions. • Chemical reactor network reveals the main reactions of FR affecting NO formation. [ABSTRACT FROM AUTHOR]

This paper proposes a particle swarm optimization (PSO) tuned novel proportional integral derivative (PID) like neural network (PSO-PID-NN), to control the temperature of a nonlinear jacketed continuous stirred tank reactor (CSTR). The nonlinear continuous stirred tank reactor (CSTR) plant is one of the most popular reactors in the chemical industry. The proposed structure is elegant in design, having only three neurons in the hidden layer and a single output neuron. The three weights in the neural network's output layer represent the PID controller's proportional, integral, and derivative gains. The suggested approach uses the PSO method to optimize the output layer weights, which corresponds to the PID gains. Mean square error is used as an objective function to optimize the weights. The performance of the proposed PSO-PID-NN controller is tested by comparing the time domain specifications of the output response, against the conventional Zeigler Nichols tuned PID controller and the back propagation-based NN-PID controller (BP-NN-PID). The overshoot in the proposed controller is 23.13%, while it is 26.33% in BP-NN-PID, and 44.13% in Zeigler Nichols tuned PID controller. In addition, the rise time is 0.1283 s, while it is 0.2727 s in the BP-NN-PID controller and 0.2813 s in Zeigler Nichols tuned PID controller. The proposed controller is also tested for disturbance rejection, it was found to be more efficient in rejecting disturbance signals as compared to BP-NN-PID and ZN-tuned PID controllers. [ABSTRACT FROM AUTHOR]

The paper develops a design feasibility study of a multi-tubular polytropic fixed bed reactor for the one-stage ethanol to 1,3-butadiene (ETB) process employing a modified MgO-SiO 2 catalyst. The analysis quantifies the effect of the internal diffusion on scaling up the catalyst activity and selectivity by considering a complex chemistry of seven parallel/series reactions described by detailed kinetic modelling. The efficient numerical solution takes advantage from the MATLAB™ function bvp5c. The simulation model allows scanning the catalytic process by profiles of species' concentrations, reaction rates and effectiveness factors, inside the catalyst particle and over the reactor. The butadiene yield is controlled by the accumulation in particle of ethanol and key intermediates, as acetaldehyde and crotonaldehyde, related to internal chemical reaction with diffusion and external mass and heat transport rates. The catalyst performance depends significantly on the pellet size that becomes optimization variable for catalyst selection and reactor design. Catalyst particles in the range 2 to 3 mm with tubes of to 25 to 40 mm diameters are the most efficient for achieving 80% butadiene carbon selectivity suitable for an industrial process. The modelling approach is generic for calculating the catalyst effectiveness and designing catalytic chemical reactors involving complex reactions. [Display omitted] • Design of multi-tubular reactor for one-stage bioethanol to 1,3-butadiene process, MgO/SiO 2 catalyst, particle modelling. • Generic method for computing porous catalyst effectiveness involving complex reactions by using MATLABTM bvp5c routine • Catalyst particles of 2 to 3 mm achieve 84 % carbon selectivity with 25 to 40 mm tube diameter at 1.5 bar and 390 °C. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) is regarded as a promising medium of hydrogen storage, due to its large hydrogen storage density, decent performance on safety and moderate storage conditions. On the user side, NH3 is generally required to decompose into hydrogen for utilization in fuel cells, and therefore it is vital for the NH3-based hydrogen storage technology development to study NH3 decomposition processes and improve the decomposition efficiency. Numerical simulation has become a powerful tool for analyzing the NH3 decomposition processes since it can provide a revealing insight into the heat and mass transfer phenomena and substantial guidance on further improving the decomposition efficiency. This paper reviews the numerical simulations of NH3 decomposition in various application scenarios, including NH3 decomposition in microreactors, coupled combustion chemical reactors, solid oxide fuel cells, and membrane reactors. The models of NH3 decomposition reactions in various scenarios and the heat and mass transport in the reactor are elaborated. The effects of reactor structure and operating conditions on the performance of NH3 decomposition reactor are analyzed. It can be found that NH3 decomposition in microchannel reactors is not limited by heat and mass transfer, and NH3 conversion can be improved by using membrane reactors under the same conditions. Finally, research prospects and opportunities are proposed in terms of model development and reactor performance improvement for NH3 decomposition. [ABSTRACT FROM AUTHOR]

To explore options for simple, safe, and compact chemical reactors that preserve wanted metastable initial products from sequential unwanted reactions, academic and industrial researchers have tried to repurpose reciprocating piston equipment or an "engine-like" design to be used as a chemical reactor. Piston reactors offer the benefit of achieving very high temperature and pressure conditions at very short and defined residence times. Such conditions offer promise for enhanced performance for several chemical conversions. This paper provides a review of the published literature and patents in the field of piston reactors to provide an overview of the current state-of-the-art. The review covers multiple aspects of piston reactors and their applications, reactor design options and their operation, catalyst and ignition placement, tested reactions, experimental setups as well as modeling and simulation. Several research gaps are highlighted as a motivation for future research in the field. To help interested readers into the topic, basic concepts and fundamentals of piston reactors are provided. [ABSTRACT FROM AUTHOR]

Heat recirculating reactors have many potential applications as thermal oxidizers, combustors, and fuel reformers due to their extensive operating range. Low emissions and fuel flexibility make such devices highly desirable as heat sources as well as chemical reactors. The dependence on the solid/gas heat transfer implies that wall characteristics and operating conditions significantly influence the stable range. In this paper, the importance of various combustor parameters is examined through an analytical model, and an experimental reactor is fabricated from a new ceramic-metal composite using additive manufacturing. A full range of possible operation modes, from flashback to blow-off, was observed together with characteristic temperature distributions at various firing rates. The new combustor showed improved operational flexibility as compared to a traditionally assembled counterpart. Low CO and NOx emission levels were observed together with an audible sound in the range between 825 Hz and 1000 Hz. The combustor operated for over 70 hours without visible damage to the material. The overall thermal performance, low emissions, and high power density make the heat recirculating reactor a viable solution for combustion applications. [ABSTRACT FROM AUTHOR]

AISI 316L, Ti2, and Zr1 are widely used in the selection of reaction still material, however, there is corrosion wear behavior in the use process. In this paper, the adsorption behavior of oxygen in Fe, Ti, and Zr is studied by the first principles method. Corrosion and wear behaviors of AISI 316L, Ti2 and Zr1 were studied by electrochemical corrosion and wear tests. The results show that AISI 316L can effectively resist the action of friction pair during wear by elastic modulus calculation. Oxygen is easily adsorbed at the top of the Fe(111) crystal plane and the bridge site of the Zr(110) crystal plane to form the most stable adsorption structure. The Ecorr of Zr1 (0.275 V) is greater than that of Ti2 (0.266 V) and AISI 316L (0.094 V), resulting in a ZrO2 passivated film with strong protection in the HNO3 solution. The wear rate of AISI 316L is higher than that of Zr1 and Ti2. In the selection of tin chemical reactor material, it is preferred that Zr1 can withstand corrosion and wear for a long time in a nitric acid system, which provides important guidance for corrosion and wear of reactor materials in the synthesis of tin acid. [ABSTRACT FROM AUTHOR]

Pham-Van et al. [[1]] numerically simulated the self-assembly of 2D clusters of colloidal particles assisted by the evaporation of an emulsion stabilized by nanoparticles (Pickering emulsions). Depending on the components' proportions, the microstructure of microemulsions ranges from tiny water droplets dispersed in the oil phase (W/O microemulsion) to oil droplets dispersed in the aqueous phase (O/W microemulsions). Microemulsions are known as thermodynamically stable nanodispersions driven by spontaneous emulsification and are commonly prepared as transparent mixtures composed of oil, water, a surfactant, and a cosurfactant. [Extracted from the article]

This paper studies the problem of event-triggered impulsive tracking control (ETITC) for uncertain strict-feedback nonlinear systems (USFNSs). In contrast to existing impulsive control schemes, this paper incorporates the neural-network (NN)-based backstepping technique into impulsive control design, such that stronger nonlinearities and uncertainties are allowed to be included in the concerned systems. The proposed state-feedback ETITC scheme guarantees that all the signals of the closed-loop system are bounded and the tracking error ultimately converges to an adjustable bounded region, while also avoiding the Zeno behavior. In addition, by constructing a NN-based observer, this paper further develops an output-feedback ETITC scheme to extend its investigation to the scenario where full states are not available for impulsive control design. Finally, an illustrative example involving a chemical reactor system is presented to demonstrate the effectiveness of our control schemes. [ABSTRACT FROM AUTHOR]

Liquid marbles are droplets with volume typically on the order of microliters coated with hydrophobic powder. Their versatility, ease of use and low cost make liquid marbles an attractive platform for digital microfluidics. This paper provides the state of the art of discoveries in the physics of liquid marbles and their practical applications. The paper first discusses the fundamental properties of liquid marbles, followed by the summary of different techniques for the synthesis of liquid marbles. Next, manipulation techniques for handling liquid marbles are discussed. Applications of liquid marbles are categorised according to their use as chemical and biological reactors. The paper concludes with perspectives on the future development of liquid marble-based digital microfluidics. [ABSTRACT FROM AUTHOR]

Reaction calorimetry is one of the main thermal analysis techniques in chemical industry, which can provide a large number of effective data for safety assessment of reaction process. In the process of measuring reaction heat Qr, it is crucial to obtain the heat transfer factor between reactor and jacket, the current common measurement method is to calibrate before and after the reaction, but the results can not represent the dynamic change of UA in the reaction process. More accurate calorimetric data can be obtained by studying the continuous estimation method of heat transfer factor, which can provide safer and more effective guidance for the development of reactor and process optimization. Temperature oscillation calorimetry (TOC) is an effective method for continuous estimation of UA and Qr in laboratory scale small reactors. This paper summarizes TOC in detail from research history, principle, parameter calculation, simulation study and method evaluation, and the simulation results illustrate the advancement and applicability of this method. For larger reactors, state estimation approaches is a more widely used method for continuous estimation of calorimetric parameters. In this paper, three state estimation techniques, namely adaptive calorimetry, cascade calorimetry and extended Kalman filter (EKF), are reviewed, and the simulation results of continuous estimation of UA and Qr by EKF in reactors with different volumes are presented. Finally, the advantages, disadvantages and applicability of temperature oscillation calorimetry and state estimation approaches are compared and analyzed. On this basis, the technology of reactor calorimetry is prospected. [ABSTRACT FROM AUTHOR]

This paper presents a macrokinetics-based mathematical model for the numerical simulation of the fuel self-ignition period in a local volume of a hydrogen diesel engine with high pressure fuel injection equipment. A detailed kinetic mechanism of hydrogen oxidation with a special software were used to simulate hydrogen self-ignition in homogeneous chemical reactors for operating conditions of a real hydrogen diesel engine at the moment of the start of hydrogen gas injection. From the results of these simulations for constant-volume and constant-pressure reactors, an equation for the macrokinetics of hydrogen oxidation at high pressures was derived. Using this equation, various operation modes of a hydrogen diesel engine with heating of air and hydrogen were investigated by numerical methods. Ways to reduce the induction period and increase the engine reliability are indicated. [ABSTRACT FROM AUTHOR]

This paper addresses the evaluation of linear controllers deployed for the unstable systems. A first-order time delayed unstable transfer function model is considered, which is subjected to ramp changes in the set-point. The performance of the controller is assessed by developing a theoretical minimum bound of the control signal, which is a measure of the total variation (TV). By considering this theoretical bound in terms of TV and also the output performance in terms of integral absolute error (IAE), a new benchmark index named IAE-TV is developed. Two control schemes are considered to investigate the proposed performance index for achieving the reasonable set-point tracking performance. Simulation studies are executed by considering the ramp changes in the set point on different examples such as control of a bioreactor, chemical reactor, to substantiate the benchmark and the significance of the proposed novel assessment technique. [ABSTRACT FROM AUTHOR]

This paper presents the magnetohydrodynamic (MHD) boundary layer stagnation point flow with diffusion of chemically reactive species undergoing first-order chemical reaction over a permeable stretching sheet in presence of partial slip. With the help of similarity transformations, the partial differential equations corresponding to momentum and the concentration equations are transformed into non-linear ordinary differential equations. Numerical solutions of these equations are obtained by shooting method. It is found that the horizontal velocity increases with the increasing value of the ratio of the free stream velocity and the stretching velocity. Velocity decreases with the increasing magnetic parameter when the free-stream velocity is less than the stretching velocity but the opposite behavior is noted when the free-stream velocity is greater than the stretching velocity. Due to suction, fluid velocity decreases at a particular point of the surface. With increasing velocity slip parameter, velocity increases when the free-stream velocity is greater than the stretching velocity. But the concentration decreases in this case. Concentration decreases with increasing mass slip parameter. [ABSTRACT FROM AUTHOR]

Decision-making is a key component of industrial control system (ICS) security. However, due to the stability and real-time requirements of ICSs, current decision-making approaches typically designed for IT systems are not entirely suitable for ICSs. In this paper, with consideration of the characteristics of ICSs, a risk-based multistep dynamic decision-making approach for protecting ICSs is proposed. Following this proposal, multiple models, including multilayer Bayesian network, process model, and attack-defense strategy model are built first. On this basis, a state controller is designed to ensure the safe degradation/upgradation of ICSs. Finally, a game theory-based optimal defense strategy generation approach is presented. To verify the effectiveness of the proposed approach, a simulation on a simplified chemical reactor control system is conducted in MATLAB. The simulation results clearly demonstrate that the proposed dynamic decision-making approach has the ability to generate the optimal defense strategy to minimize system loss. [ABSTRACT FROM AUTHOR]

Integrating systems are frequently encountered in power plants, paper-production plants, storage tanks, distillation columns, chemical reactors, and the oil industry. Due to the open-loop instability that leads to an unbounded output from a bounded input, the efficient control of integrating systems remains a challenging task. Many researchers have addressed the control of integrating processes: Some solutions are based on a single closed-loop controller, while others employ more complex control structures. However, it is difficult to find one solution requiring only a simple tuning procedure for the process. This is the advantage of the magnitude optimum multiple integration (MOMI) tuning method. In this paper, we propose an extension of the MOMI tuning method for integrating processes, controlled with a two-degrees-of-freedom (2-DOF) proportional–integral–derivative (PID) controller. This extension allows for calculations of the controller parameters from either time domain measurements or from a process transfer function of an arbitrary order with a time-delay, when both approaches are exactly equivalent. The user has the option to emphasise disturbance-rejection or tracking with the reference weighting factor b or apply two different reference filters for the best overall response. The proposed extension was also compared to other tuning methods for the control of integrating processes and tested on a charge-amplifier drift-compensation system. All closed-loop responses were relatively fast and stable, all in accordance with the magnitude optimum criteria. [ABSTRACT FROM AUTHOR]

This paper provided a numerical simulation of fluid dynamics in the chemical vapor reactor for nanoparticle synthesis. Standard k-e turbulence equation and eddy-dissipation model with standard wall function were used to investigate the reaction process of turbulent diffusion for alumina production. Here the temperature and the operating conditions are discussed. Numerical results show that the model can well describe synthesis of nanometer alumina. The chemical reactions for alumina by this reactor are mainly concentrated in the range of 200 mm after the nozzle. The materials are completely mixed after 400 mm in the reactor. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to review the applications of the chemical reactor network (CRN) approach for modeling the combustion in gas turbine combustors and classify the CRN construction methods that have been frequently used by researchers. Design/methodology/approach: This paper initiates with introducing the CRN approach as a practical tool for precisely predicting the species concentrations in the combustion process with lower computational costs. The structure of the CRN and its elements as the ideal reactors are reviewed in recent studies. Flow field modeling has been identified as the most important input for constructing the CRNs; thus, the flow field modeling methods have been extensively reviewed in previous studies. Network approach, component modeling approach and computational fluid dynamics (CFD), as the main flow field modeling methods, are investigated with a focus on the CRN applications. Then, the CRN construction approaches are reviewed and categorized based on extracting the flow field required data. Finally, the most used kinetics and CRN solvers are reviewed and reported in this paper. Findings: It is concluded that the CRN approach can be a useful tool in the entire process of combustion chamber design. One-dimensional and quasi-dimensional methods of flow field modeling are used in the construction of the simple CRNs without detailed geometry data. This approach requires fewer requirements and is used in the initial combustor designing process. In recent years, using the CFD approach in the construction of CRNs has been increased. The flow field results of the CFD codes processed to create the homogeneous regions based on construction criteria. Over the past years, several practical algorithms have been proposed to automatically extract reactor networks from CFD results. These algorithms have been developed to identify homogeneous regions with a high resolution based on the splitting criteria. Originality/value: This paper reviews the various flow modeling methods used in the construction of the CRNs, along with an overview of the studies carried out in this field. Also, the usual approaches for creating a CRN and the most significant achievements in this field are addressed in detail. [ABSTRACT FROM AUTHOR]

In this paper, a detailed mathematical optimization model of electrolyzer/fuel cell technology connected to the grid through limited rating converters is developed. The model is so defined that it can tackle voltage fluctuation and meet the power ramp rate limitations inflicted by integration of constant-speed wind turbines at the Point of Common Coupling. The flicker mitigation and power ramp rate control problem in the presence of wind generation and variable electrical loads is defined as a nonlinear constrained optimization problem, in which voltage fluctuation is minimized as the objective function and the power ramp rate limitations are respected by the defined real-time ramp rate constraint. The problem is solved using the sequential quadratic programming method, which is a fast solver, by adjusting suitable initial points to be appropriate for real-time applications. The simulation results validate the efficiency of the proposed method and show dramatic improvement in flicker mitigation, power ramp rate control, and system rating reduction in comparison with the proportional–integral control method that was developed in previous studies. [ABSTRACT FROM AUTHOR]

The article presents the author's experience of getting his research paper published in a journal. Several years ago the author submitted a paper to the journal "Management Science," that dealt with how to operate several parallel chemical reactors so as to meet a specified output while consuming the least total input. He submitted the paper to the journal "Management Science," specifically to Professor S. Eilon, the Production Management editor. His reply was prompt, polite and negative. He refused the paper on the grounds it discussed an application in an environment that was not of interest to the readership and did not report on an advance in the state-of-the-art. So he submitted the paper to "Chemical Engineering Progress," a journal of the AIChE, and was informed they publish only papers presented at national and regional meetings. He then submitted it to the journal "Chemical Engineering" and they thought it was great and published it in the June 14,1971 issue. He recommends that the editors actively seek out applications papers in specific areas and recognize that there has to be a real or potential incentive to get anyone to take the time to write up something they already know.

Low-fidelity, cost-effective, physics-based models are useful for assessing the environmental performance of novel combustion systems, especially those utilizing alternative fuels, like hydrogen and ammonia. However, these models require calibration and quantification of their limitations to be reliable predictive tools. This paper presents a framework for calibrating a simplified Chemical Reactor Network model using higher-fidelity Computational Fluid Dynamics data from a micro-gas-turbine-like combustor fuelled with pure ammonia. A Bayesian inference strategy that explicitly accounts for model error is used to calibrate the most relevant CRN parameters based on NO emissions data from CFD simulations and to estimate the model's structural uncertainty. The calibrated CRN model accurately predicts NO emissions within the design space and can extrapolate reasonably well to conditions outside the calibration range. By utilizing this framework, low-fidelity models can be employed to explore various operating conditions during the preliminary design of innovative combustion systems. • Bayesian calibration with model error embedding of Chemical Reactor Network (CRN) parameters is performed. • 15 RANS simulations of an ammonia-fuelled, multi-stage, mGT-like combustor are used as higher-fidelity samples. • Polynomial Chaos Expansion is used for likelihood construction and global sensitivity analysis. • Calibration enables quantifying parametric and model-form uncertainties in the CRN predictions of NO. • CRN allows performing optimisation under uncertainty to minimise NO at the combustor outlet. [ABSTRACT FROM AUTHOR]

Given the mechanism of reaction kinetics and the reaction rate equations, this paper presents a systematic approach to determine the optimum chemical reactor network to achieve the desired objective function. A general superstructure configuration is used to select the optimum combination of plug flow reactor (PFR) and continuous stirred tank reactor (CSTR) to get maximum yield of desired product (maximum concentration), minimum volume of the reactor, minimum operating temperature, or maximum selectivity and conversion. PFR is approximated as a series of CSTRs. The superstructure approach allows for series and parallel reactor network as it contains all possible sequences. This model can be formulated as nonlinear programming (NLP) problems, which can be solved using GAMS. Final decisions representing reactor types, sequence, and volume can be made using continuous parameters. Results obtained from GAMS are further optimized using fuzzy approach. Two literature examples are presented and solved to demonstrate the effectiveness of the approach. [ABSTRACT FROM AUTHOR]

n-Hexane (C6H14) removal and conversion are investigated in a filamentary plasma generated by a pulsed high-voltage Dielectric Barrier Discharge (DBD) at atmospheric pressure and room temperature in a dry N2/O2 (20%) mixture with C6H14. The degradation of n-hexane and the by-product formation are analyzed in real-time using a high-resolution Fourier Transform Ion Cyclotron Resonance (FT-ICR) mass spectrometer coupled with Chemical Ionization (CI). As alkanes are reacting slowly with H3O+ ions, two precursor ions were used: O2+ to follow the n-hexane mixing ratios and H3O+ to follow the mixing ratios of organic by-products. As the CI-FTICR technique can work at high mixing ratios, studies were made between 5 and 200 ppm of n-hexane. Absorption spectroscopy is also used to follow ozone and carbon dioxide molecules. We show that the DBD efficiency increases for lower n-hexane mixing ratios and a large number of by-products are identified, with the major compounds being: formaldehyde, acetaldehyde, propanal, carbon dioxide, and carbon monoxide along with nitrate compounds. Based on the nature of the by-products characterized, a mechanism accounting for their formation is proposed. [ABSTRACT FROM AUTHOR]

The use of heavy actinide targets, including 243Am, 240,242,244Pu, 245,248Cm, 249Bk, and 249Cf, irradiated by intense heavy ion beams of 48Ca has resulted in a significant expansion of the periodic table since 2000, including the discovery of five new heaviest elements and more than 50 new isotopes. These actinide materials can only be produced by intense neutron irradiation in very high flux reactors followed by chemical processing and purification in specialized hot cell facilities available in only a few locations worldwide. This paper reviews the reactor production of heavy actinides, the recovery and chemical separation of actinide materials, and the preparation of actinide targets for superheavy element experiments. The focus is on 248Cm, 249Bk, mixed 249−251Cf, and 254Es, including current availabilities and new production processes. The impacts of new facilities, including the Superheavy Element Factory at Dubna, accelerator and separator upgrades at RIKEN, and proposed upgrades to the High Flux Isotope Reactor at Oak Ridge are also described. Examples of recent superheavy element research are discussed as well as future opportunities for superheavy research using actinide targets. [ABSTRACT FROM AUTHOR]

Mathcad is a simple‐to‐use and intuitive mathematical software that helps students to minimize the mathematical difficulties involved in solving engineering problems. The design of nonisothermal plug flow reactors (PFR) is a fundamental issue within the field of chemical reaction engineering; however, its teaching–learning process is hindered by students' mathematical difficulties in solving ordinary differential equations. In this paper, the software Mathcad was conveniently integrated into an educational experience through the resolution of two real case studies. In the first one, a simple liquid‐phase reaction is considered in a PFR working at different operating conditions, whereas the second case evaluates a PFR taking place multiple reactions (parallel reactions) with a heat exchanger attached. The assessment of this experience, which was held into two 5‐h Mathcad workshops, revealed that Mathcad made the design of non‐isothermal PFR more appealing, facilitated the understanding of the design process, and brought another dimension to the way the students perform complex calculations. [ABSTRACT FROM AUTHOR]

This paper deals with the tracking of a prespecified profile temperature for exothermic chemical tubular reactor whose dynamics is described by a set of nonlinear partial differential equations where the state variables are the reactor temperature and the reactant concentration. The coolant temperature, the inlet temperature and the inlet concentration are considered as control actions. For practical reasons, it is preferable to consider a non distributed control law to achieve the control objective. In contrast to our previous work that considers fully distributed control actions where the three control inputs are assumed to be distributed along the reactor, here the last two control inputs are applied at the reactor inlet and only the coolant temperature is distributed along the reactor. We show that the temperature of the reactor tends asymptotically to a ball of arbitrary prescribed radius λ > 0 , centred at the given temperature profile. [ABSTRACT FROM AUTHOR]

This paper considers the exponential stabilization problem for a class of strict-feedback nonlinear systems with multiple time-varying delays, whose nonlinear terms satisfy the linear growth condition. The state feedback controller that relies on a positive parameter to be determined is constructed to deal with nonlinear terms. By tactfully introducing the Lyapunov–Krasovskii functional with an exponential function and selecting the applicable parameter to be determined, the implementable state feedback controller can be obtained to guarantee that the closed-loop system is exponentially stable. The proposed state feedback control scheme is finally applied to the control design of two-stage chemical reactor system, which illustrates the effectiveness of the control method. [ABSTRACT FROM AUTHOR]

Dispersion is the spreading of a solute while it is moved by a flowing medium. The study of dispersion in catalytic chemical reactors is fundamental to their design, since dispersion influences the reactant and product transport within the bed. In this paper, longitudinal and transverse dispersion of an inert tracer in slender packed beds of spheres and spherocylinders is studied using Computational Fluid Dynamics simulations. The focus is on the analysis of dispersion from full field data. The purpose is to develop a methodology that can later also be used to characterize dispersion from full field experimental data such as MRI measurements. Results obtained by means of particle-resolved CFD simulations are discussed. Spatial distributions and residence times are analyzed and the results are interpreted by comparison to results obtained from 1D and 2D convection-diffusion equations. [ABSTRACT FROM AUTHOR]

The application of neural networks can present some limitations for the control of strongly nonlinear systems. In this paper, a new control scheme based on a neural multicontroller (NMC) is proposed. Indeed, the developed strategy considers a set of local neural controllers which adapt their parameters thanks to an online adaptation algorithm. The instantaneous choice of the adequate local controller is based on a switching mechanism. The advantages of the proposed method are (1) to avoid the computational complexity issues due to the search for an optimal adapting rate when a single neural controller is used, and in presence of strongly nonlinear systems, and (2) to improve the control law by selecting the suitable controller which generates the most valid control law satisfying the desired closed-loop performances. Numerical examples are illustrated to evaluate the performance of the proposed control scheme compared to the classical one. An application of the new strategy on a chemical reactor model validates satisfactory results. [ABSTRACT FROM AUTHOR]

A refutation of the criticisms expressed in the paper entitled 'Evolution of Chain Microstructure and Kinetics of Reaching Equilibrium in Living Reversible Copolymerization' by R. Szymanski, S. Sosnowski, and M. Cypryk ( Macromol. Theory Simul. 2016, 25, 196) about the article entitled 'Kinetics and Thermodynamics of First-Order Markov Chain Copolymerization' ( J. Chem. Phys. 2014, 141, 044908) is presented here. With this aim, a comparison is made between reversible living copolymerization processes taking place in either closed or open reactors. [ABSTRACT FROM AUTHOR]

In this paper, implementation of deep neural networks applied in process control is presented. In our approach, training of the neural network is based on model predictive control, which is popular for its ability to be tuned by the weighting matrices and for it respecting the system constraints. A neural network that can approximate the MPC behavior by mimicking the control input trajectory while the constraints on states and control input remain unimpaired by the weighting matrices is introduced. This approach is demonstrated in a simulation case study involving a continuous stirred tank reactor where a multi-component chemical reaction takes place. [ABSTRACT FROM AUTHOR]

This paper proposes a novel data-based optimal control algorithm for continuous stirred tank reactor (CSTR) system based on adaptive dynamic programming (ADP). To overcome the challenge of establishing an accurate mathematical model for the CSTR system, neural networks are employed to reconstruct the dynamics of the CSTR system using the production data of the system. A new nonquadratic form performance index function is provided, where the control input is constrained in order not to exceed the bound of the actuator. Then, the operational optimal control problem of CSTR is formulated. Furthermore, an iterative ADP (IADP) algorithm is developed to obtain the optimal tracking controller for the CSTR system with control constraints. In particular, the convergence analysis of the IADP algorithm is developed. The proposed IADP algorithm is implemented via the dual heuristic dynamic programming structure. Finally, the proposed approach is applied to the real CSTR system to verify the effectiveness and performance. [ABSTRACT FROM AUTHOR]

Modelling and controlling of Continuous Stirred Tank Reactor (CSTR) is one of the significant problems in the process industry. Chemical reactions inside the CSTR depend on the reference value of the temperature. Design and implementation of suitable control device for such system is a challenge for researchers. This paper proposes the Model Reference Adaptive Control (MRAC) based control strategy as a solution to control problem of CSTR. An enhancement of Signal Synthesis MRAC scheme has been proposed in this study to improve the steady-state and transient-state performance of CSTR. Genetic Algorithm (GA) based controller parameter tuning method is employed to obtain the optimal performance of the controller. This paper presents the design and implementation of conventional Proportional–Integral–Derivative (PID) tuned with Ziegler–Nichols (ZN) tuning method, PID tuned with GA, MRAC, and GA-MRAC for CSTR. Detailed comparison based on simulation studies is also presented to show the improved transient and steady state response with GA-based improved MRAC scheme. [ABSTRACT FROM AUTHOR]

In this paper, we conduct the comparative analysis of two neural network approaches to the problem of constructing approximate neural network solutions of non-linear differential equations. The first approach is connected with building a neural network with one hidden layer by minimization of an error functional with regeneration of test points. The second approach is based on a new continuous analog of the shooting method. In the first step of the second method, we apply our modification of the corrected Euler method, and in the second and subsequent steps, we apply our modification of the Störmer method. We have tested our methods on a boundary value problem for an ODE which describes the processes in the chemical reactor. These methods allowed us to obtain simple formulas for the approximate solution of the problem, but the problem is special because it is highly non-linear and also has ambiguous solutions and vanishing solutions if we change the parameter value. [ABSTRACT FROM AUTHOR]

This paper reports a new method for studying stereoselective catalyzed reactions at a small scale. For this purpose, a micro‐sized chemical reactor and a chiral chromatographic column were integrated on a single microfluidic chip hyphenated to mass spectrometry. By running the integrated reactor in truly continuous‐flow operation with an automated injection strategy, catalytic processes and their stereoselectivity can be observed over an extended range of time with significantly small consumption of samples, solvents, and catalytic material. [ABSTRACT FROM AUTHOR]

The design of control methods for unstable plants is somewhat complex than that of stable plants. This is because unstable process models contain one or more poles lying on the right of the s-plane which yields unbounded closed-loop response. Further, the presence of the dead-time induces more complexity as it decreases the gain and phase margins which in turn deteriorates the closed-loop performance. The design of control strategies become more challenging for plants of unstable nature with positive zeros because they exhibit a phenomenon called inverse response. This paper suggests a method to design a double-loop scheme for unstable plants with/without inverse response. Accordingly, a proportional-derivative (PD)/proportional (P) controllers are used in the inner-loop for stabilizing the plant. A fractional order internal model controller (FOIMC) scheme is used to obtain the outer-loop controller using the stabilized plant model. The P/PD controller settings have been obtained by using the Routh-stability criteria and the maximum sensitivity approach. Procedure for selecting the outer-loop tuning parameter and fractional order is also given. Linear and nonlinear models of unstable plants including bioreactors and isothermal chemical reactors are used to demonstrate the merits of the suggested strategy. Robustness of the design and effect of measurement noise are also studied. Integrated absolute/squared error measures are also calculated. The suggested design is found to be more effective in controlling unstable processes than some reported works. [ABSTRACT FROM AUTHOR]

Chaos theory has wide applications in several branches of science and engineering. The discovery of novel chaotic systems in various applications, their qualitative properties and the control of such systems are active research areas. This paper derives new results for the analysis and adaptive control of a chemical chaotic attractor discovered by Haung (2005). This paper starts with a detailed description of the chemical reactor dynamics and the parameter values for which the chemical reactor exhibits chaotic behaviour. Next, adaptive control law is devised for the global chaos control of the chemical chaotic reactor with unknown parameters. Next, a circuit design of the Chaotic system and its adaptive lag synchronization are implemented in LabVIEW to validate the results for the theoretical chaotic model. Finally we used the synchronized system to transmit a message signal by masking the input signal with the Chaotic system. Secure communication between two parties (or systems) is done in such a way that the identity of the communicating party is confirmed and the confidentiality as well as the integrity of the message is maintained. The results of the proposed Secure communication system is derived in LabVIEW. [ABSTRACT FROM AUTHOR]