Adiabatic Batch Reactor Research Articles

Effect of Mixing and Reaction on a fast Step Growth Polymerization**

Abstract A polyurethane reaction under different mixing rates and reaction rates are studied in an adiabatic batch reactor. Results are explained by using a slab model and dimensional analysis. Four characteristic times are used to describe the interactions of mixing, diffusion and chemical reaction, which may serve as conceptual guidelines in determining the proper reaction rate and mixing power for a specific reaction system.

Entropy production and timescales

Spatially homogeneous reactive systems are characterised by the simultaneous presence of a wide range of timescales. When the dynamics of such reactive systems develop very slow and very fast timescales separated by a range of active timescales, with large gaps in the fast/active and slow/active timescales, then it is possible to attain a multi-scale adaptive model reduction along with the integration of the governing ordinary differential equations using the G-Scheme framework. The G-Scheme assumes that the dynamics is decomposed into active, slow, fast, and when applicable, invariant subspaces. We derive expressions that reveal the direct link between timescales and entropy production by resorting to the estimates of the contributions of the fast and slow subspaces provided by the G-Scheme. With reference to a constant pressure adiabatic batch reactor, we compute the contribution to entropy production by the four subspaces. These numerical experiments show that, as indicated by the theoretical derivation, the contribution to entropy production of the fast subspace is of the same magnitude as the error threshold chosen for the numerical integration, and that the contribution of the slow subspace is generally much smaller than that of the active subspace. We explicitly exploit this property to identify the slow and fast subspace dimensions differently from the method adopted in the G-Scheme, where the dimensions of the subspaces are defined on the basis of the asymptotic approximations of the contributions of the fast and slow subspaces. Comparison of the outcome of the analyses performed using two types of criteria underlines the substantial equivalence of the two. This property opens the door to a number of possible applications that will be explored in future work. For example, it is possible to utilise the information on entropy production associated with reactions within each subspace to define an entropy participation index that can be utilised for model reduction.

Analysis of Adiabatic Batch Reactor

A mixture of acetic anhydride is reacted with excess water in an adiabatic batch reactor to form an exothermic reaction. The concentration of acetic anhydride and the temperature inside the adiabatic batch reactor are calculated with an initial temperature of 20°C, an initial temperature of 30°C, and with a cooling jacket maintaining the temperature at a constant of 20°C. The graphs of the three different scenarios show that the highest temperatures will cause the reaction to occur faster.

Experimental Simulation of Three-Dimensional Attainable Region for the Synthesis of Exothermic Reversible Reaction: Ethyl Acetate Synthesis Case Study

Exothermic reversible reactions are an industrially important class of processes, and many have complex kinetics associated with them. This article shows how experimentally measured variables such as residence time, temperature, and conversion can be used to construct a three-dimensional attainable region for a typical exothermic reversible reaction without taking into consideration the kinetics associated with the reaction. The experiments were conducted using an adiabatic batch reactor fitted with a thermistor for temperature measurement. The article also shows how the two-dimensional conversion–temperature plot was obtained from the three-dimensional residence time–temperature–conversion plot. The two-dimensional plot was then used to propose the optimal process configuration for the process where preheating, reaction, and mixing are allowed. Examination of the boundary of the two-dimensional attainable region of the conversion–temperature plot provided the optimal combination of reaction and mixing an...

Geometry and reactor synthesis: maximizing conversion of the ethyl acetate process

This paper describes how experimentally generated results were used to optimize conversion of a process using adiabatic batch reactor systems. The process used in the experiment was exothermic reversible process. The experiments were conducted using Dewar Thermos-flask operating under adiabatic conditions. Equilibrium conversions were determined from temperature–time information. Temperatures were determined using negative temperature coefficient thermistor. For a single batch process, the equilibrium conversion determined experimentally was shown to be 0.55 and 0.21 with respect to acetic acid using two initial temperatures of 283 K and 295 K, respectively. It is shown by a simple geometrical approach that without the knowledge of the kinetics of the process, by increasing the number of reactors and considering internal cooling systems, the reaction equilibrium lines were crossed and conversion improved significantly. The paper also shows that one can attain the maximum possible conversion of 0.72, thus increasing equilibrium conversions by 31 % by adding a single adiabatic reactor to the single-stage adiabatic reactor by this geometrical technique, and hence proposes the optimal reactor configuration with interstage cooling system to achieve this optimal conversion.

Kinetic Study on Sodium Sulfate Synthesis by Reactive Crystallization

In this work, the kinetics of the reaction between sodium chloride and sulfuric acid, in aqueous solution and in the presence of ethanol as antisolvent, was studied as a function of each reactant concentration and temperature. The thermometric method was implemented to fit the experimental data obtained in an adiabatic batch reactor. The initial reaction rate methodology was applied to determine the order of reaction as well as the specific reaction rate constants. The reaction rate corresponded to an elementary reaction. Good agreement between experimental and simulation temperature profiles was achieved (absolute average deviation (AAD) of ∼1.15%). The reactive crystallization process was found to be very selective to anhydrous Na2SO4, with yields higher than 95 wt %.

Experimental Simulation of a Two-Dimensional Attainable Region and Its Application in the Optimization of Production Rate and Process Time of an Adiabatic Batch Reactor

Attainable region analysis is a graphical optimization technique which enables design engineers to synthesize optimal reactor networks to achieve a given objective. This is accomplished if a given system of reactions with known reaction kinetic models and feedstock is available. This paper shows experimentally how the geometry of a two-dimensional attainable region can be generated by reaction and mixing as the only fundamental processes occurring in the reactor of a hydrolysis process without taking the reaction kinetic model of the process into consideration. The experiment was conducted using an adiabatic batch reactor fitted with a thermistor for temperature measurement. The results were used to develop a novel technique to run the adiabatic batch reactor by applying the attainable region analysis. From the analysis the production rate of the product and the process time of the adiabatic batch reactor were optimized by graphical techniques, and it is shown that the maximum production rate increased by 72% as compared with the standard method of operating the batch reactor and the corresponding minimized process time was reduced to 0.36 h compared with 1.26 h of the standard batch operation. It is also shown that the limit of the optimization process generated the optimal process configuration required for a continuous operation to achieve the highest production rate in a minimum time possible.

Software sensors for monitoring of a solid waste composting process

AbstractProcess identification for composting of tobacco solid waste in an aerobic, adiabatic batch reactor was carried out using neural network-based models which utilized the nonlinear finite impulse response and nonlinear autoregressive model with exogenous inputs identification methods. Two soft sensors were developed for the estimation of conversion. The neural networks were trained by the adaptive gradient method using cascade learning. The developed models showed that the neural networks could be applied as intelligent software sensors giving a possibility of continuous process monitoring. The models have a potential to be used for inferential control of composting process in batch reactors.

Fused Chemical Reactions. 2. Encapsulation: Application to Remediation of Paraffin Plugged Pipelines

Fused chemical reactions are reactions that undergo a delay before significant amounts of product are produced. One class of fused chemical reactions is the class of reactions triggered by an abrupt release of a catalyst. Fused chemical reactions have the potential of solving the problem of organic deposition in sub-sea pipelines which is a problem with enormous economic consequence (Singh, P.; Fogler, H. S. Ind. Eng. Chem. Res. 1998, 37 (6), 2203). The reaction between ammonium chloride and sodium nitrite catalyzed by citric acid was chosen as an example of a fused chemical reaction system where the acid was encapsulated in polymer-coated gelatin capsules. The timed release of the acid catalyst was achieved by putting an additional polymeric coating on the gelatin capsules. The reaction kinetics and the polymer dissolution kinetics were investigated in an adiabatic batch reactor. An excellent agreement between simulation and experimental results in the batch reactor was achieved. Experimental results in a flow-loop reactor demonstrated that the fused chemical reaction could provide a substantial amount of heat in situ. This amount of heat is sufficient to overcome the high heat loss to the surroundings and to raise the temperature of the fluid above the effective temperature to soften and melt the wax deposit. The delay in heat release was found to depend on the thickness of the polymeric coating, while the amount and rate of heat release depended on the in situ reactant and acid concentrations.

Obtention of the Optimal Feeding Profile in a Fed-Batch Reactor Using Genetic Algorithms

Thermal and kinetic studies were carried out in a previous work using an adiabatic batch reactor. In this work a very exothermic reaction has been chosen. The reaction is performed by feeding H2O2 to a solution of Na2S2O3. Several experiments have been carried out at different operating conditions (addition flow, initial temperature, initial concentration of reagents, etc.) in semibatch mode of operation with heat transfer. An algorithm describing the mathematical model has been developed and implemented in Matlab software. The mathematical model has been validated with experiments at different addition flows of H2O2, while concentration and heat profiles have been obtained by simulation. Then, an optimization program has been developed to obtain the best combination of inlet flow and addition time, to maintain the reactor temperature at the selected temperature setpoint, and to minimize the reaction time. The optimization method used is based on genetic algorithms (GA). The GA technique is shown to be the most appropriate multivariable method that avoids falling in local maxima and shows satisfactory results in all cases tested.

Batch and semibatch reactor performance for an exothermic reaction

In this work, a study of a batch and semibatch reactor has been carried out based on a very exothermic reaction between thiosulfate and hydrogen peroxide. The experiments were carried out in a glass-jacketed reactor of 5 l, provided with different sensors and a data acquisition system. Thermal and kinetic studies were carried out previously using an adiabatic batch reactor. Then, these results have been used for experiments in semibatch mode of operation with heat transfer. Several experiments have been carried out at different operating conditions (addition flow, initial temperature, initial concentration of reagents…). In batch and adiabatic mode of operation, experimental measures of the reaction mass temperature provided concentration profiles of reagents and products which have been compared to those determined by simulation. In semibatch mode of operation, temperature profiles have also been simulated and validated with experimental results. An algorithm describing the mathematical model has been developed and implemented in a software module written in FORTRAN 77 language. With this mathematical model it has been possible to obtain concentration and heat profiles for the semibatch mode of operation.

Effect of Mixing and Reaction on a fast Step Growth Polymerization**

Abstract A polyurethane reaction under different mixing rates and reaction rates are studied in an adiabatic batch reactor. Results are explained by using a slab model and dimensional analysis. Four characteristic times are used to describe the interactions of mixing, diffusion and chemical reaction, which may serve as conceptual guidelines in determining the proper reaction rate and mixing power for a specific reaction system.

Automatically Controlled Adiabatic Reactor for Reaction Rate Studies

An apparatus is described for the measurement of the kinetics of fairly fast (half times 1–5 min), homogeneous, liquid chemical reactions, by recording the temperature-time curve in an adiabatic batch reactor. Adiabatic conditions are maintained by keeping the metal reactor as closely as possible at the same temperature as the reacting species by passing a heating current directly through the walls. Allowance is made for controller set point changes which accompany a temperature increase of the system. Specific heat determinations were carried out on water to test the ability of the control system to maintain adiabatic conditions. The operation of the apparatus is illustrated with kinetic measurements of the hydrolysis of acetic anhydride in dilute aqueous solutions.