Features of thermal explosion in systems with strong self-retardation

2012

KEM

A new approach to the consideration of the thermal explosion macrokinetic features for monomolecular reactions in homogeneous systems based on a strict accounting of burnout during the reaction process is proposed. It is established, that the qualitative changes of the phase trajectory structure (phase portrait) on the plane: heating rate-temperature determine the characteristic modes of reaction. This approach makes it possible to go beyond the Semenov theory and allows us to consider the variety of the reaction modes. From this point of view, the theory of Semenov is a special case which is valid only for reactions of zero order. The phase trajectories analyze on the parametrical plane Semenov criterion – Todes criterion gives an opportunity to define the regions of the thermal explosion degeneration, the transition regions and the region of the thermal explosion realization. With the use of such consideration, the necessary and sufficient conditions of the thermal explosion are found.

“…From the consideration (7), (8) we can conclude that the minimum on the inflection isoclines disappears under condition:…”

Section: Quantitative Analyze First Order Reactionsmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Nonstationary Theory of the Thermal Explosion for Monomolecular Exothermic Reactions

2012

KEM

“…determined by the particular features of the phase diagram of the system. In this aspect, the use of effective kinetic functions [6,9], being universal to a certain extent, provides only a schematic description of the real process, because the specific features of interaction of a particular system are ignored, and these features, in turn, are determined by the structure of the phase diagram. In the present paper, we consider interactions in heterogeneous systems characterized by the phase diagram with a congruently melting intermediate phase with weak solubility of the highmelting component in the melt of the low-melting component.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of phase-formation processes during self-propagating high-temperature synthesis in the thermal explosion regime

Combust Explos Shock Waves

Кошелев

2008

Specific features of formation of temperature and concentration fields during selfpropagating high-temperature synthesis in the thermal explosion regime in a cylindrical reactor are studied by methods of mathematical modeling. The calculations are performed with allowance for melting of one (chemically active) component in the approximation with the high-melting component being non-soluble in the melt of the low-melting component. It is shown that the conditions of complete conversion of the original components in the volume of the reacting mixture depend on relations between the Biot criterion of the system, the ambient temperature, and the thermal effect of the reaction. After the thermal explosion, which occurs when the melting front reaches the geometric center of the reactor, a front of complete conversion is formed. This front moves from the cylinder centerline to the periphery with a gradually decreasing velocity. The diagram of the critical values of the Biot criterion at which the components burn down completely in the entire reaction volume is calculated.

“…It follows that, gener ally, we must analyze both thermal balance and chem ical kinetics equations. Because of this complication, thermal explosion theory was developed using approx imate analytic [4,5] and (mainly) numerical simula tion methods [6][7][8]. A detailed analysis of works on thermal explosion theory is given in [1].…”

Section: Introductionmentioning

confidence: 99%

The method of phase trajectories in nonstationary thermal explosion theory

2012

Russ. J. Phys. Chem. B

It is shown that consideration of the heating rate-temperature dependence, an analysis of self heating for first order exothermic reactions, and strict inclusion of kinetic deceleration puts forward fresh ideas about the diversity of reaction regimes on the Todes criterion-Semenov criterion parameter plane. From this point of view, classic Semenov theory is a particular case of the projection of two dimensional regions onto the direction of Semenov criterion changes. An analysis of the mutual arrangement of reaction region boundaries with different kinetics and the shape of the representation point movement trajectory when the initial temperature of the system changed allowed us to determine the thermal explosion degeneration region, transition region, and regions of possible explosive reaction modes.