Flame Inhibition by Ferrocene and Blends of Inert and Catalytic Agents.
Flame Inhibition by Ferrocene and Blends of Inert and
Catalytic Agents.
(207 K)
Linteris, G. T.; Rumminger, M. D.; Babushok, V. I.;
Tsang, W.
Combustion Institute, Symposium (International) on
Combustion, 28th. Proceedings. Volume 2. July
20-August 4, 2000, Edinburgh, Scotland, Combustion
Institute, Pittsburgh, PA, Candel, S.; Driscoll, J. F.;
Burgess, A. R.; Gore, J. P., Editor(s)(s), 2965-2972 pp,
2000.
Keywords:
combustion; flame extinguishment; ferrocene;
experiments; numerical models; flame chemistry; metal
oxides; halon alternatives; flame suppression
Abstract:
The production of the fire suppressant CF3Br has been
banned, and finding a replacement with all of its
desirable properties is proving difficult. Iron
pentacarbonyl has been found to be up to several orders
of magnitude more effective than CF3Br, but it is
flammable and highly toxic. The compound ferrocene
(Fe(C5H5)2), which is much less toxic and flammable than
Fe(CO)5, can also be used to introduce iron into a
flame. We present the first experimental data and
numerical modeling for the flame inhibition properties
of ferrocene, and find it to behave similarly to
Fe(CO)5. A ferrocene mole fraction of 200 ppm reduces
the burning velocity of slightly preheated premixed
methane-air flames by a factor of two, and the
effectiveness drops off sharply at higher mole
fractions. The burning velocity reduction is less with
an oxidizer stream having a higher oxygen mole fraction.
We also present experimental data and modeling for
flames with ferrocene blended with CO2 or CF3H. The
combination of the thermally acting agent CO2 with
ferrocene mitigates the loss of effectiveness
experienced by ferrocene alone at higher mole fractions.
An agent consisting of 1.5% ferrocene in 98.5% CO2
performs as effectively as CF3Br in achieving a 50%
reduction in burning velocity. Likewise, four times less
CO2 is required to achieve the 50% reduction if 0.35%
ferrocene is added to the CO2. In contrast, addition of
0.35% ferrocene to the hydrofluorocarbon CF3H only
reduces the CF3H required to achieve the 50% reduction
in burning velocity by only about 25%. Thermodynamic
equilibrium calculations predict that the formation of
iron-fluoride compounds can reduce the concentrations of
the iron-species oxide and hydroxide intermediates which
are believed to be responsible for the catalytic radical
recombination cycles.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899