Self-ignition point

Table 3.8. Flash point, self-ignition point, ignitability limit and explosion limits in air of some precursors [56]...

Flash point (°C) Self -ignition point (°C) Ignitability volume limit (%) lower upper Ignitability temperature limit (°C) lower upper Explosion limit in air (%) lower upper ... 

Saw dust, 75, 82, 89, 106 Saw dust, 75 cost, 106 particle size, 106 Scona, 165, 166, 171 Graft level, 171 Scona TPPP 8112, 171 Secant modulus at 2% strain, 71, 72 Secondary antioxidants, 526, 527 Secondary aromatic amines, 526 Secondary macroalkyl radical, 497 Seed fibers, 110 Seed husks fiber, 88 Self-ignition point, 59... 

If the initial pressure is increased to some value P2, the heat release curve shifts to higher values, which are proportional to P" (or p"). The assumption is made that h is not affected by this pressure increase. The value of P2 is selected so that the ql becomes tangent to the qr curve at some point c. If the value of h is lowered, qr is everywhere greater than ql and all initial temperatures give explosive conditions. It is therefore obvious that when the ifo line is tangent to the qr curve, the critical condition for mixture self-ignition exists. 

Whether we are dealing with the occurrence of adiabatic extinction and ignition (see Fig. la,6) or with self-ignition and extinction which are essentially related to the heat transfer, as in Fig. 1 c,d, obviously depends on the sign of the third derivative, d3r/d(3, at the inflection point. 

The problem of self-ignition of a gas confined in a vessel with two plane-parallel walls of identical temperature was solved by Frank-Kamenetskii by investigating a steady regime which preserves equality between the released and evacuated heat at all points of the gas mixture, and by considering the limit of existence of this steady regime [1]. 

We note that the envelopes of the family (see Fig. 1) of curves yield the limits of self-ignition, and thus serve as an illustration of Frank-Kamenet-skii s theory. Indeed, if we place two walls of temperature 60 at the points A and Ax, we find two steady regimes. No steady regime corresponds to a distance C — Cx between the walls. Finally, B — Bx is a limiting distance, the limiting diameter of a plane-parallel vessel at the given temperature 80, with B and B1 located on the envelopes of the integral curves of the family under consideration. 

EUem (Ref 4) points out that Th, when alloyed with Ag, Cu. or Au, becomes much more ignitable, bursting into flame on rubbing. Th—Ag alloys in approx 1 1 proportions are actually self-igniting (Ref 5). M. Jacobson et al (Ref 2) indexed the explosibility of both Th and Th hydride dusts based on ign temp, spark energy for ign, min expin concn, expln press and rate of press rise as compared with Pittsburgh seam coal, and report that both of these dusts have severe explosibility indices of >10... 

Between 140° and 160° C m oxygen and 200° to 270° C. in air oxidation becomes autogenous or self-propellant, and as soon as this point is reached the temperature rises rapidly to the ignition-point.8... 

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