Three-phase Catalytic Slurry Reactor Research Articles

Intensification principle of a new three-phase catalytic slurry reactor. Part I: Performance characterisation

This paper presents the concept and the performances of a mini horizontal stirred tank reactor, used for hydrogenation reaction. A simple analytical model based on characteristic times of heat and mass transfer illustrates the intensification principle and shows that the relevant intensification parameter is the mass to heat transfer characteristics times ratio. The proof of concept is made through a small scale reactor named RAPTOR® (French acronym for Reactor with Polyvalent Rectilinear Stirred Reactor with Optimised Transfer). The mass transfer performances are measured and compared to conventional stirred tank reactor and other multiple impeller continuous reactors. In a following second paper, a comparative study is proposed to evaluate the eco-efficiency and the techno-economic advantages of a continuous process involving a RAPTOR® versus a classical batch process based on a stirred reactor.

Intensification principle of a new three-phase catalytic slurry reactor. Part II: Eco-efficiency and techno-economic performances

In two papers, the concept and the performances of a new continuous intensified reactor named RAPTOR® (French acronym for Reactor with Polyvalent Rectilinear Stirred Reactor with Optimised Transfer) are presented.Based on flow, heat and mass transfer characterisations and real hydrogenation experiments, Paper I presented a simple analytical model based on characteristic times that enables to explain the intensified performances compared with a semi-batch stirred reactor and to generalise the operability, rapidity and the flexibility of this minireactor. In Paper II (this article), the model is used to evaluate in a comparative study the eco-efficiency and the techno-economical advantages of a continuous process involving a RAPTOR® versus a classical batch process equipped with a stirred reactor. Economical, environmental aspects are considered as well as productivity, safety and process control.

Optimization of a Three-Phase Catalytic Slurry Reactor Using Reduced Statistical Models

The main contribution of this work is to propose the use of a statistical procedure to generate simplified models from a detailed deterministic one for Real Time Optimization. Such models are also used as a tool to map the optimal and feasible region. These simplified models are useful in online optimization coupled to control implementations, since detailed rigorous models may demand time and high computational burden for their solution, which hampers the success of online purposes. In order to illustrate the application of the procedure, a three-phase catalytic reactor was considered. A dynamic heterogeneous mathematical model formulation of the o-cresol hydrogenation reaction was used to simulate the reactor steady-state response to different inlet conditions. The proposed statistical procedure (factorial design) generated simplified models for the reactor exit temperature and the reactant conversion, two useful pieces of process information. The use of these models in an optimization problem is then presented as an illustration of their application in an online real time optimization in a two-layer fashion. The simplified models turn possible the identification of the range of optimal solutions as well as the mapping of the region of optimal solutions very quickly compared to the use of full models, allowing the system to be flexibly operated at high level of performance.

Development of Rigorous and Reduced Heterogeneous Dynamic Models for Fixed Bed Catalytic Reactor and Three-Phase Catalytic Slurry Reactor

In this work, the dynamic behavior of two chemical reactors (Fixed Bed Catalytic Reactor and the Three-Phase Reactor), in which different reactions of great industrial interest take place, is presented. Rigorous and reduced models were developed and their capabilities to adequately predict the dynamic behavior of these reactors were compared, indicating which model is more suitable for a specific application (design, optimization and control). Different approaches [Classic, Hermite, Finlayson, Pirkle, Dixion, Generic and Orthogonal collocation (one point)] were used to obtain the reduced models. With these techniques, a mathematical order reduction was carried out, which eliminates the spatial co-ordinate (of the catalyst particle or of the reactor) and promotes radially lumped-differential formulations. The proposed rigorous models were able to predict the main characteristics of the dynamic behavior of the fixed bed catalytic reactor as well as of the three-phase reactor, including the inverse response phenomena and the hot spot present in the former. This knowledge is essential to design and control these reactors. The computational time demanded for the solution of the rigorous models is high in comparison to the reduced ones, which restricts the use of the rigorous models to cases where time is not a limiting factor. Otherwise, when on-line applications are required, the reduced models are more adequate. The models based on reduction techniques overcame computational burden with a faster and easier numerical solution, as well as other difficulties found in rigorous heterogeneous models, especially related to the large number of parameters and sophisticated numerical procedures required by the solution.

AN APPROACH TO OPTIMIZATION OF A THREE PHASE CATALYTIC SLURRY REACTOR BY EVOLUTIONARY OPTIMIZATION WITH GENETIC ALGORITHMS

The present work introduces an investigation study about the optimization of a three-phase catalytic slurry reactor with phase changes. The study aims to determine the optimal operational conditions and, in a second stage, advanced control algorithms will be evaluated. A dynamic heterogeneous mathematical model formulation was used and genetic algorithms (GA) were employed to solve a nonlinear quadratic problem subject to bounds on the variables. The solutions obtained using the genetic algorithms gave suitable results to optimize the process by adjusting parameters as the reactor feed temperature and the flow rate of one of the reactants. It was possible to reach operation conditions that ensured a suitable profit and an acceptable compromise with the specifications of the desired product.

Off-line optimization and control for real time integration of a three-phase hydrogenation catalytic reactor

In order to develop and test the integration procedure, in this paper a real time process integration involving the optimization and control of the process is presented, in this case, with the two-layer approach. The used optimization algorithms were Levenberg–Marquardt and SQP that solve a non-linear least square problem subject to bounds on the variables. The two-layer approach is a hierarchical control structure where an optimization layer calculates the set points and manipulated variables to the advanced controller, which is based on the dynamic matrix control with constraints (QDMC). The non-isothermal dynamic model of the three-phase slurry catalytic reactor with appropriate solution procedure was utilized in this work (Vasco de Toledo, E. C., Santana, P. L., Maciel, M. R. W., & Maciel Filho, R. (2001). Dynamic modeling of a three-phase catalytic slurry reactor. Chemical Engineering Science, 56, 6055–6061). The model consists on mass and heat balance equations for the catalyst particles as well as for the bulk phases of gas and liquid. The model was used to describe the dynamic behavior of hydrogenation reaction of o-cresol to obtain 2-methil-cyclohexanol, in the presence of a catalyst Ni/SiO 2.

Development of a software for simulation analysis of the phenomenon of phase change of three-phase catalytic slurry reactor

The principal aim of this work was the development of a software capable to simulate, via deterministic modelling, the phenomenon of phase change observed in three-phase catalytic slurry reactors, that occurs in the reacting medium and in the refrigerant fluid. Intending to achieve a realistic representation of the system, a detailed dynamic model was formulated. The model was applied to describe the reactor dynamic behaviour during the hydrogenation of o-cresol on Ni/SiO2 catalyst. However, other reactions can easily be incorporated to the software due to the generality adopted during the development of the model. The model allowed to reproduce the main dynamic characteristics of the reactor, in face of several changes in operational parameters of the reactor, and the developed software allows the user to simulate different possibilities introduced in the model, with the aim of a better reproduction of chemical plant data.

Simulation and response surface analysis for the optimization of a three-phase catalytic slurry reactor

Simulation and response surface analysis for the optimization of a three-phase catalytic slurry reactor

Simulation and response surface analysis for the optimization of a three-phase catalytic slurry reactor

Factorial design and response surface analysis techniques were used in combination with modeling and simulation to optimize an industrial hydrogenation process. A three-phase reactor for the production of cyclohexanol by hydrogenation of phenol in the presence of the catalyst Ni/SiO 2, with a six-stage cooling system for temperature control was considered. The model equations form a system of ordinary differential equations derived from kinetic laws and steady-state balances for mass and energy for both reactants and coolant system. Initially, screening design was used to evaluate the process variables which were relevant to the cyclohexanol yield. Two statistically significant parameters (rates of hydrogen- Q H and catalyst- Q Ni) were selected and used in response surface methodology for process optimization. An improvement of 5.5% in cyclohexanol yield was observed for the optimized variables ( Q H = 259 kg/h, Q Ni = 53 kg/h).

Optimization strategy for maximizing production of cyclohexanol

The main issue objective of this work is to implement an optimIzation strategy through a two-layer structure where the search for optimal operational variables is made through of the algorithms optimization - Successive quadratic programming - SQP. The considered process is based on the hydrogenation of phenol for production of cyclo-hexanol in the presence of a nickel catalyst. The objective function to be considered for the optimization is to maximize production of cyclo-hexanol, through a steady-state model while maintaining the conversion of phenol at the exit of the reactor under environmental constraints. Factorial design and response surface analysis in a simulation study of a three-phase catalytic slurry reactor is used to identify the impact that each variable has on the system as well as the interaction among then. An improvement of 5.5% in cyclo-hexanol conversion was observed for the optimized variables (OH = 259 kg/h, ONi = 53 kg/h).The resulted model for the response surface was used as a flrst objective function for the SQP optimization. Theoptimization results can be then used as set-point values to the advanced controller

Dynamic modelling of a three-phase catalytic slurry reactor

Two dynamic models for a three-phase catalytic slurry reactor with appropriate solution procedures were developed in this work. The models consist of mass and heat balance equations for the catalyst particles, for the gas and liquid bulk phases as well as for the heat exchange through the jacket of the reactor. The models of the tubular reactor were applied to describe the dynamic behaviour of the reactor during the hydrogenation of o-cresol on Ni/SiO 2 catalyst. These models differ in solid phase modelling, which allows to evaluate the reactor dynamic behaviour prediction capacity. The models successfully reproduce the main characteristics of the reactor dynamic behaviour.

Temperature effects on separate values of adsorption and surface reaction rates by dynamic studies

The study of a three-phase catalytic slurry reactor for SO2 oxidation on activated carbon has been conducted with a dynamic response technique. The analysis of zero and first temporal moments of the gas for temperatures between 10 and 26°C provides individual measurements of the adsorption, desorption and surface reaction rate constants and their energies of activation. A parallel first-moment analysis was carried out for O2 adsorption onto carbon to obtain the necessary equilibrium constants for temperatures used in the SO2-oxidation calculations. With second moment analysis of adsorption data, we find the adsorption kinetic constants with and without reaction are in quantitative agreement. By evaluating the separate temperatu effect on the adsorption/desorption, and surface reaction rates, we conclude that neither step is controlling at temperatures up to 26°C. The values the several kinetic and equilibrium constants agree well with those found by other authors.