Irreversible Exothermic Reaction Research Articles

METHODOLOGY FOR EXPERIMENTAL RESEARCH OF THE FIRE HAZARD OF POWER LITHIUM-ION BATTERIES OF ELECTRIC VEHICLES UNDER THE INFLUENCE OF A HEATING PANEL

Even though lithium-ion batteries (LIBs) are the subject of various tests and research at the production stage, there are no isolated cases of electric vehicle fires, and the development dynamics are unpredictable. The particular danger of such fires lies in the oxygen release during an irreversible exothermic reaction in LIBs, which creates new challenges for fire and rescue services when extinguishing such fires. The study aims to develop the main provisions of the methodology for experimental studies of electric vehicle power batteries in terms of fire hazards using an electric heating panel. The ultimate goal of the study is to determine the temperatures at which an irreversible exothermic reaction, the opening of ventilation holes, and the combustion (explosion) of electric vehicle power batteries begin, as well as the time parameters at which such processes occur. Taking into account the peculiarities of the occurrence and course of the irreversible exothermic reaction, we have developed a methodology, the essence of which is to determine the temperatures of the onset of the irreversible exothermic reaction of the electric vehicle power battery, the opening of ventilation holes, and the combustion (explosion) of electric vehicle power batteries, the combustion temperatures of ventilation gases, as well as the time parameters at which these processes occur, which may change during battery operation and not correspond to the declared parameters of the manufacturer. For this purpose, we exposed LIBs to thermal energy from an electric heating panel and recorded the temperature and time during which an irreversible exothermic reaction occurs from the moment of an internal short circuit to a fire or explosion. The use of the proposed methodology of experimental studies of the elements of power batteries of electric vehicles regarding the fire hazard of an electric heating panel will make it possible to determine the temperature limits of the occurrence of irreversible exothermic reactions in LIBs, as well as the time parameters under which these processes occur. Keywords: electric vehicle fire, irreversible exothermic reaction, lithium-ion battery.

Thermal runaway chain reaction determination and mechanism model establishment of NCA-graphite battery based on the internal temperature

The measurement of battery internal temperature directly affects the determination of the sequence of thermal runaway chain reaction and the choice of model heat sources, and the optimal combination identification of kinetic parameters corresponding to each heat source is the premise of establishing model. This paper focuses on the Lix(Ni0.8Co0.15Al0.05)O2-graphite pouch battery with built-in thermocouple. Based on the stage division of thermal runaway behavior and the decoupling of irreversible exothermic reaction between battery components, the thermal runaway mechanism is determined. Then, the optimal combination of kinetic parameters is determined by combining the DSC tests under variant heating rates, the Kissinger's method and the genetic algorithm. Furthermore, a thermal runaway model considering hierarchical properties is established, and the thermal contribution of six exothermic reactions at each stage of thermal runaway is quantified. Anode+electrolyte and cathode+anode contribute 53.8% and 18.7% respectively to the heat accumulation before thermal runaway. Internal short circuit accounts for 27.5%, and the heat is released instantaneously, directly triggering thermal runaway. This work has important reference significance for the design of battery safety warning system and the battery modification strategy.

An Effective Numerical Technique for Boundary Value Problems Arising from an Adiabatic Tubular Chemical Reactor Theory

Mathematical models for an adiabatic tubular chemical reactor which forms an irreversible exothermic reaction are investigated by an efficient numerical technique, Fibonacci Collocation method in this study. The reaction's steady-state temperature is calculated for several values of three parameters, namely, Peclet and Damkohler numbers and the dimensionless adiabatic temperature increment. When the generated outcomes are compared with the other numerical approaches, it has been sighted that the presented method produces reliable results for this type of problems.

A Proposal of Fuzzy Rule Partition and Its Application to Controller Design Based on Affine T‐S Fuzzy Model

When designing a controller based on a fuzzy model composed of fuzzy rules, in most cases controllers are designed only based on the consequent parts of the fuzzy rules, equally meaning the information of the antecedent parts is merely ignored. This paper first partitions all of the rules into two groups based on the information of the antecedent parts, in which one contains certain rules around the origin, and the other is a group of rules away from the origin. While being able to make the former arbitrarily small, each rule of the latter leads to a favorable quadratic inequality, which will be useful in controller design by the help of the S‐procedure. On the other hand, while the affine T‐S fuzzy model is much more effective for describing the dynamics of the system concerned in comparison with the regular T‐S fuzzy model, it encounters some difficulties when designing a controller based on the model because of the affine terms within. This paper makes clear that the difficulties can be overcame by using the quadratic inequalities based on the fuzzy rule partition. In addition, the effectiveness of the approach is demonstrated by applying it to the CSTR for an exothermic irreversible reaction. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Design of Optimal Fractional Order Lyapunov Based Model Reference Adaptive Control Scheme for CSTR

When a first-order irreversible exothermic reaction takes place in a continuously stirred tank reactor (CSTR), the plant model relating the reactor and jacket temperatures along with a measurement delay is of second-order unstable type. Such plants are very challenging to control. Hence, this article focuses on developing an optimal fractional order Lyapunov (FOL) based model reference adaptive control (MRAC) scheme. The optimal values of adaptive gain, as well as extra degree of freedom, are obtained using a modified particle swarm optimization (PSO) algorithm. The closed-loop responses and control efforts are compared with that of FOL based MRAC scheme by using an artificial bee colony (ABC) algorithm to optimize adaptive gain and extra degree of freedom. Moreover, the aforementioned optimization methods are also employed to develop respective optimal fractional order Massachusetts institute of technology (FOMIT) based MRAC schemes for comparison purposes. In both these algorithms, a multi-objective function involving minimization of rise-time, settling-time, integrated absolute error, integrated square error, integrated time-weighted absolute error is used. Simulation studies validate the effectiveness of the proposed particle swarm optimized FOL-based MRAC scheme.

ANALYSIS OF STUDENTS' ABILITY TO IDENTIFY SYMBOLIC REPRESENTATIONS IN CHEMISTRY

To describe the behavior of matter and energy, chemists classify them in three distinct domains: macroscopic, microscopic, and symbolic. The ability to use these three representations is the basis for understanding concepts in chemistry. This study aims to analyze students' ability to identify symbolic representations in chemistry. The research design uses a one shot case study. The subjects of this study were students of prospective science teachers as many as 85 students. Data collection techniques using tests and rubrics. The results showed that of the ten symbolic representation statements, only three statements achieved the highest percentage of correct answers, namely statements about writing ionization reactions and writing electron symbols. There are two statements where almost 90 percent of students answered incorrectly. The statement is about reversible or irreversible reaction equations and exothermic reaction equations. From this research, it can be concluded that students' ability to identify symbolic representations in chemistry still needs to be improved, because the average score is still low.

РАЗРАБОТКА ТЕХНОЛОГИЧЕСКИХ РЕКОМЕНДАЦИЙ ПО ОБЕСПЕЧЕНИЮ ПОЖАРОВЗРЫВОБЕЗОПАСНОСТИ ПРИ ПОДЗЕМНОЙ РАЗРАБОТКЕ МЕСТОРОЖДЕНИЙ КОЛЧЕДАННЫХ РУД

The urgency of the problem of reducing the risks associated with spontaneous com-bustion of coal ores and sulfide dust explosions has now increased not only in Russia, but al-so abroad, as there have been significant changes in the mineral resource base of the world's leading metal producers. The oxidation of sulfide ores and rocks with air oxygen is an irre-versible and characteristic exothermic reaction that should be taken into account during the extraction and processing of sulfide-containing minerals to prevent spontaneous combustion of ores and explosions of sulfide dust. The article presents the developed technological measures and recommendations aimed at preventing the processes of oxidation and sponta-neous combustion of coal ores and sulfide dust explosions.

Rarefied reactive gas flow in T-shape microreactors

The present study investigates the reactive gas flows in T-shape microreactors by means of a 3D direct simulation Monte-Carlo method (DSMC). The reactive process is modeled by incorporating a single step irreversible exothermic reaction of gas species A and B. The energy released in each reaction is added to the system by increasing the kinetic energy of the product gas specie C. The reactive collisions are modeled by means of a momentum preserving hard sphere collision model in 3D DSMC. We analyzed several process and gas parameters to observe their extent of influence on the characteristics of the reactive flow. The T-microreactor with thermal walls showed much higher mass carrying capacity as compared to the specular walls. The reaction front, which initially for maximum reaction rate was close to the inlet of gas specie of higher mass density, moved towards the center of the inlet part of the T-channel and eventually dissolved with decreasing reaction rates. This transition was smooth in the T-channel with thermal walls, whereas, quite abrupt in case of specular walls. Moreover, in T-microreactors with thermal walls, the amount of A and B converted to C follows an exponential decrease especially in moderate to low reaction rates. Further, with a clear separation between high and low reactive regimes, a piece-wise exponential decay in concentration of C with respect to decreasing reaction rates was also observed in the T-channel with specular walls.

New wavelet method for solving boundary value problems arising from an adiabatic tubular chemical reactor theory

This paper displays an efficient numerical technique of realizing mathematical models for an adiabatic tubular chemical reactor which forms an irreversible exothermic chemical reaction. At a steady-state solution for an adiabatic rounded reactor, the model can be diminished to a conventional nonlinear differential equation which converts into a system of the nonlinear equation that can proceed numerically utilizing Newton’s iterative method. An operational matrix of coordination is derived and is utilized to decrease the model for an adiabatic tubular chemical reactor to an arrangement of algebraic equations. Simple execution, basic activities, and precise arrangements are the fundamental highlights of the proposed wavelet technique. The numerical solutions attained by the present technique have been contrasted and compared with other techniques.

B-spline Wavelet Method for Solving Fredholm Hammerstein Integral Equation Arising from Chemical Reactor Theory

AbstractMathematical model for an adiabatic tubular chemical reactor which processes an irreversible exothermic chemical reaction has been considered. For steady state solution for an adiabatic tubular chemical reactor, the model can be reduced to ordinary differential equation with a parameter in the boundary conditions. Again the ordinary differential equation has been converted into a Hammerstein integral equation which can be solved numerically. B-spline wavelet method has been developed to approximate the solution of Hammerstein integral equation. This method reduces the integral equation to a system of algebraic equations. The numerical results obtained by the present method have been compared with the available results.

Fuzzy modelling and model reference neural adaptive control of the concentration in a chemical reactor (CSTR)

This simulation study is a fuzzy model-based neural network control method. The basic idea is to consider the application of a special type of neural networks based on radial basis function, which belongs to a class of associative memory neural networks. The novelty of this approach is the use of an RBF neural network controller in a model reference adaptive control architecture, based on a one-step-ahead Takagi–Sugeno fuzzy model. The objective is to control the concentration in a continuous stirred-tank reactor highly non-linear system and to assure its stability by limiting the temperature rise generated from the irreversible exothermic reaction. This contribution will help to reduce environmental impact of chemical waste.

Effect of coolant flow rate on the dynamics of delayed recycle continuous stirred tank reactor

Abstract Numerical bifurcation analysis of delayed recycle stream in a continuous stirred tank reactor was studied using DDE-BIFTOOL. A first-order irreversible exothermic reaction s 1 → k 2 , 1 s 2 was considered for analyzing effect of delay on the stability of the delayed recycle system. The non-isothermal CSTR was operated at both infinite and finite coolant inlet flowrates. A constant delay was considered in the recycle stream of CSTR for concentration of reactant, and temperature. DDE-BIFTOOL solver was used for finding dependency of delays on the bifurcation parameters, and its stability characteristics. The bifurcation parameters considered were: (i) fresh feed flowrate, (ii) coolant temperature, and (iii) coolant inlet flowrate. In the absence of delay, the system exhibits the region of dynamic instability for both infinite and finite coolant inlet flowrates. For infinite coolant flowrate, the region of dynamic instability on the reactor temperature was modified as a result of delay by varying either fresh feed flowrate or coolant temperature. The steady-state multiplicity was observed on the coolant temperature by varying fresh feed flowrate at finite coolant inlet flowrate. In the absence of delay, the fold and Hopf bifurcations were observed on the multiple steady-states of coolant temperature. The concentration and temperature delays do not alter substantially the dynamic characteristics of coolant temperature at Tc,in = 298 K. However, delays can alter the region of dynamic instability for coolant temperature when coolant inlet temperature is higher than 298 K. These are the main result of present work.

State estimation of chemical engineering systems tending to multiple solutions

A well-evaluated state covariance matrix avoids error propagation due to divergence issues and, thereby, it is crucial for a successful state estimator design. In this paper we investigate the performance of the state covariance matrices used in three unconstrained Extended Kalman Filter (EKF) formulations and one constrained EKF formulation (CEKF). As benchmark case studies we have chosen: a) a batch chemical reactor with reversible reactions whose system model and measurement are such that multiple states satisfy the equilibrium condition and b) a CSTR with exothermic irreversible reactions and cooling jacket energy balance whose nonlinear behavior includes multiple steady-states and limit cycles. The results have shown that CEKF is in general the best choice of EKF formulations (even if they are constrained with an ad hoc clipping strategy which avoids undesired states) for such case studies. Contrary to a clipped EKF formulation, CEKF incorporates constraints into an optimization problem, which minimizes the noise in a least square sense preventing a bad noise distribution. It is also shown that, although the Moving Horizon Estimation (MHE) provides greater robustness to a poor guess of the initial state, converging in less steps to the actual states, it is not justified for our examples due to the high additional computational effort.

Impact of delay on robust stable optimization of a CSTR with recycle stream

We demonstrate that the normal vector method for robust optimization of nonlinear systems with uncertain parameters can be extended to systems with delays. A first-order exothermic irreversible reaction carried out in a CSTR with recycle stream serves as example for the broad class of nonlinear delay differential equations (DDE) with uncertain parameters. The stability boundaries that must be taken into account in the robust optimization consist of Hopf bifurcation points in this case. We show that (i) an unstable steady state of operation results if stability boundaries are neglected and (ii) a conservative optimal steady state results if the delay is ignored.

Oxidation Reaction of Polyether-Based Material and Its Suppression in Lithium Rechargeable Battery Using 4 V Class Cathode, LiNi1/3Mn1/3Co1/3O2

The all solid-state lithium battery with polyether-based solid polymer electrolyte (SPE) is regarded as one of next-generation lithium batteries, and has potential for sufficient safety because of the flammable-electrolyte-free system. It has been believed that polyether-based SPE is oxidized at the polymer/electrode interface with 4 V class cathodes. Therefore, it has been used for electric devices such as organic transistor, and lithium battery under 3 V. We estimated decomposition reaction of polyether used as SPE of all solid-state lithium battery. We first identified the decomposed parts of polyether-based SPE and the conservation of most main chain framework, considering the results of SPE analysis after long cycle operations. The oxidation reaction was found to occur slightly at the ether bond in the main chain with the branched side chain. Moreover, we resolved the issue by introducing a self-sacrificing buffer layer at the interface. The introduction of sodium carboxymethyl cellulose (CMC) to the 4 V class cathode surface led to the suppression of SPE decomposition at the interface as a result of the preformation of a buffer layer from CMC, which was confirmed by the irreversible exothermic reaction during the first charge, using electrochemical calorimetry. The attained 1500 cycle operation is 1 order of magnitude longer than those of previously reported polymer systems, and compatible with those of reported commercial liquid systems. The above results indicate to proceed to an intensive research toward the realization of 4 V class "safe" lithium polymer batteries without flammable liquid electrolyte.

Temperature wave trains of the loop reactor: The effect of thermal dispersion

Networks of catalytic reactors with periodically rotated inlet and outlet ports are studied. A first order irreversible exothermic reaction is considered and the influence of thermal dispersion on the stability limits of periodic regimes corresponding to trains of traveling temperature waves is examined. The dependence of the minimum adiabatic temperature rise sustaining the emergence of temperature wave trains on the enthalpy Peclet number, and on the structure of the spatiotemporal temperature pattern (number of waves and average wave width) is described. The mechanisms determining the evolution of the maximum temperature with the adiabatic temperature rise, the enthalpy Peclet number, the switch time, and the structure of the spatiotemporal temperature pattern are identified. The results provide indications on how to design and operate the network so as to generate temperature wave trains with prescribed structure, maximum temperature and stability limits.

Temperature control of a pilot plant reactor system using a genetic algorithm model‐based control approach

AbstractThe work described in this paper aims at exploring the use of an artificial intelligence technique, i.e. genetic algorithm (GA), for designing an optimal model‐based controller to regulate the temperature of a reactor. GA is utilized to identify the best control action for the system by creating possible solutions and thereby to propose the correct control action to the reactor system. This value is then used as the set point for the closed loop control system of the heat exchanger. A continuous stirred tank reactor is chosen as a case study, where the controller is then tested with multiple set‐point tracking and changes in its parameters. The GA model‐based control (GAMBC) is then implemented experimentally to control the reactor temperature of a pilot plant, where an irreversible exothermic chemical reaction is simulated by using the calculated steam flow rate. The dynamic behavior of the pilot plant reactor during the online control studies is highlighted, and comparison with the conventional tuned proportional integral derivative (PID) is presented. It is found that both controllers are able to control the process with comparable performance. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd.

Effect of the Switch Strategy on the Stability of Reactor Networks

The dynamics of a three-catalytic-reactor network, where an exothermic irreversible reaction occurs, is studied. The network is operated by periodically switching feed and discharge positions (with the period being T). We analyzed the effect of two different switch strategies and observed different spatio-temporal patterns. Such differences result from the different spatio-temporal symmetry that is induced by the switch strategies. Their effect on the stability is studied by comparing the stability range of T-periodic regimes as the switch time is varied for different values of the feed temperature. This analysis is conducted by a numerical continuation technique based on the spatio-temporal symmetry of the forced system. For low (ambient) feed temperature, the stability ranges of a diabatic reactor conform to criteria previously proposed for adiabatic reactors [Sheintuch, M; Nekhamkina, O. AIChE J. 2005, 51, 224]. We observe that these criteria cannot be applied at higher feed temperatures, as a consequence of the external heat losses. One of the examined switch strategies is used to determine a significant widening of the operability conditions.

Quantitative Comparison of Temperature Control of Reactors with Jacket Cooling or Internal Cooling Coils

This paper presents a quantitative comparison of the effectiveness of two alternative heat-removal schemes in the control of continuous stirred tank reactors (CSTRs). The chemistry features an exothermic irreversible reaction A → B, and different design levels of conversion are explored. Two mechanisms for removing the heat of reaction are studied: (1) a cooling jacket surrounding the vessel or (2) an internal cooling coil. Controllability is shown to become more difficult as the design conversion decreases. Results demonstrate that internal coil cooling provides better dynamic controllability than jacket cooling in terms of being able to handle larger disturbances. A generic “reactor controllability index” (RCI) is proposed that can be used to assess the dynamic robustness of any CSTR. The RCI is the dimensionless ratio of the temperature difference between the reactor and jacket (or the log-mean temperature difference for coil cooling) and the maximum available temperature difference (reactor temperatu...

Enabling stability analysis of tubular reactor models using PDE/PDAE integrators

We discuss the construction of computational superstructures enabling time-dependent process simulation codes to perform stability, continuation and bifurcation calculations—tasks in principle not accessible to them—directly. The basis of the approach is the so-called Recursive Projection Method of Shroff and Keller (SIAM Journal of Numerical Analysis 31). We discuss its implementation and performance for the detection of different types of bifurcations (with emphasis on Hopf bifurcations) as well as slight modifications appropriate for index 1 partial differential/algebraic equations (PDAE) simulators. Tests that help discriminate between physical and numerical (spurious) bifurcations detected in the process are discussed and illustrated through the standard example of a tubular reactor with a single irreversible exothermic reaction.