Ignition kinetics

Gaseous products in milligram scale (using TGA/FTIR/MS for toxicity and ignition kinetics)... 

J.A. Mulholland, A.F. Sarofim and J.M. Beer, On the Derivation of Global Ignition Kinetics from a Detailed Mechanism for Simple Hydrocarbon Oxidation, Comb. Sci. Tech. 87 (1992) 139-156. 

Combustion and ignition kinetics for hydrogen and different hydrocarbons is well known and facilitates the numerical analysis of plasma stimulation, assuminig that the major contribution of plasma is limited to the generation of radicals. Such an efficiency analysis... 

The development of combustion theory has led to the appearance of several specialized asymptotic concepts and mathematical methods. An extremely strong temperature dependence for the reaction rate is typical of the theory. This makes direct numerical solution of the equations difficult but at the same time accurate. The basic concept of combustion theory, the idea of a flame moving at a constant velocity independent of the ignition conditions and determined solely by the properties and state of the fuel mixture, is the product of the asymptotic approach (18,19). Theoretical understanding of turbulent combustion involves combining the theory of turbulence and the kinetics of chemical reactions (19—23). 

From the heat generation alone the maximum tolerable temperature difference between catalyst and gas can be evaluated, as will be shown in a later chapter. This is never done in pollution control catalyst testing. Due to the simple conditions at very low concentration, the Ignition Curve can be evaluated for first order kinetics. 

These equations hold if an Ignition Curve test consists of measuring conversion (X) as the unique function of temperature (T). This is done by a series of short, steady-state experiments at various temperature levels. Since this is done in a tubular, isothermal reactor at very low concentration of pollutant, the first order kinetic applies. In this case, results should be listed as pairs of corresponding X and T values. (The first order approximation was not needed in the previous ethylene oxide example, because reaction rates were measured directly as the total function of temperature, whereas all other concentrations changed with the temperature.) The example is from Appendix A, in Berty (1997). In the Ignition Curve measurement a graph is made to plot the temperature needed for the conversion achieved. 

Igniter(s) design, 21-24 pyrotechnic, 23-24 rocket exhaust, 21-23 aft end, 23, 28 heat end, 21-23 Ignition approaches kinetic, 9 thermodynamic, 9 chamber-pressure transient, 7-8 delay time, 20, 24-25 hot-wire, 11-12 hypergolic, 24 pressure transients, 29-30 theory... 

For processes under development, the most cost-effective means of avoiding potential risk is to eliminate those materials that are inherently unsafe that is, those materials whose physical or physico-chemical properties lead to them being highly reactive or unstable. This is somewhat difficult to achieve for several reasons. First, without a full battery of tests to determine, for example, flammability, upper/lower explosivity limits and their variation with scale, minimum ignition temperatures, and so on, it is almost impossible to tell how a particular chemical will behave in a given process. Second, chemical instability may make a compound attractive to use because its inherent reactivity ensures a reaction proceeds to completion at a rapid enough rate to be useful that is, the reaction is kinetically and thermodynamically favoured. 

Figure 6.2. Typical ignition delay of an alkane fuel as a function of the initial mixture s temperature. Three different kinetic models are shown (a) High temperature chemistry only that is, no peroxy radical chemistry, (b) Same as (a), but the Q OOH chain-branching channel of the peroxy radicals has been considered, (c) Same as (b), bnt the concerted elimination of RO2 to alkene + HO2 has been considered. (Figure courtesy of Timothy Barckholtz, ExxonMobil Research and Engineering.)...

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