Classification and analysis of integrating frameworks in multiscale modelling

A generalized criterion for parametric sensitivity: Application to thermal explosion theory

This paper presents a new approach for sensor location for state and parameter estimation for stable nonlinear systems. The unique feature of this technique is that sensor locations for state estimation and measurement locations for parameter estimation can be determined within the same framework. To compute optimal sensor locations, information derived from observability covariance matrices is combined with already existing measures, which were proposed either for state or parameter estimation, to compute the degree of observability of a nonlinear system over an operating region. The optimal sensor locations then correspond to the configuration that returns the highest value of the measure for the degree of observability of a system. The proposed method is illustrated in case studies where optimal sensor locations for state and parameter estimation for a binary distillation column and a fixed-bed reactor are computed. The results obtained from the presented approach are compared with a technique based up...

Determining Optimal Sensor Locations for State and Parameter Estimation for Stable Nonlinear Systems

A general runaway criterion valid for single as well as for multiple reaction types, i.e. consecutive, parallel, equilibrium, and mixed kinetics reactions, and for several types of reactors, i.e. batch reactor (BR), semibatch reactor (SBR) and continuous stirred tank reactor (CSTR) has been developed. Furthermore, different types of operating conditions, i.e. isoperibolic and isothermal (control system), have been analysed. The criterion says that we are in a runaway situation when the divergence of the system becomes positive (div>0) on a segment of the reaction path. The results show that this is a general runaway criterion than can be used to calculate the runaway limits for chemical reactors. The runaway limits have been compared with previous criteria. A considerable advantage, over existing criteria, is that it can be calculated on-line using only temperature measurements and, hence, it constitutes the core of an early warning runaway detection system we are developing.

A general criterion to define runaway limits in chemical reactors

In this paper a review of recent developments on safety and runaway prevention in batch and semibatch reactors is given. To prevent thermal runaways in chemical reactors usually three lines of defense have to be considered: choice of the right operating conditions, early warning detection system and system to handle running away reactions. Because of its too specific nature, the last line of defense is not discussed in this review, while the former two are considered in detail. Firstly the capability and applicability of the reaction calorimeter for safety assessments are reviewed, then fundamental safety criteria for safe operation of batch and semibatch reactors are reported and discussed. A review of the most useful and efficient methods for a correct choice of safe operating conditions is split into two cases: one, when the reaction kinetics are known, and when kinetic information is not available. Also several promising recent developments of an early warning detection system for the on-line detection of unexpected situations leading to a thermal runaway are presented.

G.F. Froment

Papers

Parametric sensitivity and runaway in fixed bed catalytic reactors