The most debatable and discrepant viewpoints of non-isothermal kinetics are discussed in the form of twelve questions and answers. The reputation of non-isothermal kinetics when carried out by thermoanalysts; the consequences of simplified concepts transferred from the kinetics of homogeneous reactions; the physical meaning of basic kinetic parameters in solid-state processes; the kinetic compensative effect and interdependence of kinetic parameters using the Arrhenius rate constant; the mutual usefulness of differential and integral methods of kinetic data evaluation; their accuracy and correctness; the reliability of DTA measurements; non-isothermal versus isothermal investigations; equilibrium and kinetic data and their mutual effect; the extended discussion initiated by MacCallum and Tanner; non-isothermal data publication policy; and finally the use of computers.

Philosophy of non-isothermal kinetics

The assessment, control, and mitigation of reaction hazards is primarily based on the use of kinetic models. These kinetic models are used for the assessment of reaction hazards, the operation and control of the reactor, the design of emergency relief systems, estimation of the consequences of a reaction runaway, etc. The validity of these assessments depends highly on the validity of the kinetic model employed.



Several steps are required to identify a suitable kinetic model. This includes: 



Selection of the model type.




Estimation of the model's parameters using available data.




Validation of the model.






This article discusses each of these steps in detail and identifies problems associated with each step. Several practical examples are used to demonstrate these problems.



The results show that (1) the results are sensitive to a number of assumptions, (2) mistakes may originate from misinterpretation of the thermal data, and (3) computational methods do exist to provide suitable kinetic models for hazard assessment.



The analysis employed assumes a batch-reaction system, since most of the kinetic data available is derived from batch calorimetric equipment. © 2007 American Institute of Chemical Engineers Process Saf Prog, 2007

Identification of kinetic models for the assessment of reaction hazards

Various manifestations of the kinetic compensation effect are considered in reactions involving the participation of solid substances under isothermal and nonisothermal conditions, as well as manifestations of other isoparametric correlations. It is shown that isoparametric correlations can be used for the analysis of solid-phase reactions and the exclusion of artefacts in nonisothermal kinetics.

Isoparametric kinetic relations for chemical transformations in condensed substances (Analytical survey). II. Reactions involving the participation of solid substances

Comparison of crystallization kinetics determined by isothermal and non-isothermal methods

The effects of self cooling on the apparent kinetics of the nonisothermal dehydration of crushed crystals of lithium sulfate monohydrate were investigated using TG accompanied by DTA and power-compensation type DSC. Linearity of the sample heating rate on the TG-DSC system is much better than that on the TG-DTA. Kinetic obedience and Arrhenius parameters obtained from the TG-DTA deviate considerably from those obtained from the TG-DSC; the latter are the more accurate due to the better linearity of the sample heating rate.

Self-cooling effect on the kinetics of nonisothermal dehydration of lithium sulfate monohydrate

Methodological Principles in studying chemical reaction kinetics under conditions of programmed heating

Theory of thermal explosion of self-accelerating reactions

: An analysis was made and a solution was found with the aid of an electronic computer for a system of equations for thermal explosions; it is given in partial derivatives for reactions of the zero and first order with heat transfer by conduction in the zone of the reaction and a Newton heat exchange at the boundary. The basic characteristics of thermal explosions are exactly determined. The obtained results are presented in the form of approximate expressions connecting the characteristics of the thermal explosion with all parameters of the problem for a wide range of changes. A criterion is given for the applicability of the averaged volume of the equation for calculating the period of induction, in case the heat transfer in the reacting volume takes place by conduction. A method is offered for averaging the system of equations of thermal explosions. (Author)

V. T. Gontkovskaya

Papers

Methodological Principles in studying chemical reaction kinetics under conditions of programmed heating

Theory of thermal explosion of self-accelerating reactions

Concerning the theory of unsteady thermal explosions