Multiple steady states in two-phase reactors under boiling conditions

In this paper, we analyze the nonlinear behavior of two–phase reactors under boiling conditions. First we focus on a simple nth-order reaction of the form A -> B, which allows a rigorous analytical treatment. Three necessary conditions for the existence of multiple steady states have been identified: the reactant A has to be the light–boiling component, the difference in boiling point temperatures between the reactant A and the product B has to be sufficiently large, and the order of the reaction has to be less than some physical parameter alpha. This parameter alpha can be interpreted as a measure for the phase–equilibrium–driven self–inhibition of the reaction mechanism. Thus, we have found an elegant explanation for the occurrence of multiplicities. Analytical and therefore general quantitative criteria identifying the regions of multiplicity for the model system are presented. Practical relevance of our results is demonstrated by means of two examples, the Monsanto process for the production of acetic acid and the ethylene glycol reactive distillation system. © 2003 Elsevier Science Ltd. All rights reserved. [accessed 2014 March 28th

Multiple steady states in two-phase reactors under boiling conditions

In this paper, we analyze the nonlinear behavior of two–phase reactors under boiling conditions. First we focus on a simple nth-order reaction of the form A -> B, which allows a rigorous analytical treatment. Three necessary conditions for the existence of multiple steady states have been identified: the reactant A has to be the light–boiling component, the difference in boiling point temperatures between the reactant A and the product B has to be sufficiently large, and the order of the reaction has to be less than some physical parameter alpha. This parameter alpha can be interpreted as a measure for the phase–equilibrium–driven self–inhibition of the reaction mechanism. Thus, we have found an elegant explanation for the occurrence of multiplicities. Analytical and therefore general quantitative criteria identifying the regions of multiplicity for the model system are presented. Practical relevance of our results is demonstrated by means of two examples, the Monsanto process for the production of acetic acid and the ethylene glycol reactive distillation system

Dynamic plantwide modelling, flowsheet simulation and nonlinear analysis of an industrial production plant

A detailed dynamic model of the Monsanto process for the production of acetic acid is presented. The nonlinear behaviour of the process is investigated and implications different control structures have on its dynamic behaviour are pointed out

Nonlinear analysis of reactor separator systems involving an evaporatively cooled reactor

The focus of this contribution is on the nonlinear analysis of a model reactor separator system. The first order reaction A to B is carried out in an adiabatic, evaporatively cooled reactor. The vapor leaving the reactor is completely recycled after total condensation in an overhead condenser. The liquid reaction mixture is separated in a flash separator, with the liquid being recycled to the reactor. For the case of a temperature-controlled flash, the control strategy relying on perfect reactor level control via manipulation of the reactor effluent stream is investigated. The existence of multiple steady states for this configuration is demonstrated, and stability issues are discussed. In particular, it is shown that the behavior of this integrated system with non-isothermal reactor is qualitatively different from both the corresponding system with isothermal operation of the reactor, and also from the behavior of the standalone evaporatively cooled reactor

Object-oriented modelling of large scale chemical engineering processes with ProMoT

The application of the process modelling tool ProMoT to large-scale chemical engineering processes is presented. Particular emphasis in on the flexibility of the tool in terms of creating flowsheet alternatives - a prerequisite for efficient plant design and control structure selection. The main concepts in this respect are the bottom-up development of an object-oriented knowledge base for the simplified implementation of submodels on the level of process units, the efficient aggregation on the flowsheet level and the flexibility to effectively perform top-down refinements for problem-specific applications. All concepts are illustrated on the basis of an industrial scale process

Dynamic plantwide modelling, flowsheet simulation and nonlinear analysis of an industrial production plant

A detailed dynamic model of the Monsanto process for the production of acetic acid is presented. The nonlinear behaviour of the process is investigated and implications different control structures have on its dynamic behaviour are pointed out. © 2002 Elsevier B.V. All rights reserved. [accessed 2014 March 31st

Application of the Process Modeling Tool ProMoT to large-scale chemical engineering processes

The application of the process modeling tool ProMoT to large-scale chemical engineering processes is presented. Particular emphasis is on the flexibility of the tool in terms of creating flowsheet alternatives - a prerequisite for efficient plant design and control structure selection. The main concepts in this respect are the bottom-up development of an object-oriented knowledge base for the simplified implementation of submodels on the level of process units, the efficient aggregation on the flowsheet level, and the flexibility to effectively perform top-down refinements for problem-specific applications. All concepts are illustrated on the basis of an industrial scale process