Carbon Monoxide Formation in Fires by High-Temperature Anaerobic Wood Pyrolysis.
Carbon Monoxide Formation in Fires by High-Temperature
Anaerobic Wood Pyrolysis.
(733 K)
Pitts, W. M.; Johnsson, E. L.; Bryner, N. P.
Combustion Institute. Symposium (International) on
Combustion, 25th. Proceedings. Abstracts of Symposium
Papers. Session 07-B: Fire Hazards. July 31-August 5,
1994, Irvine, CA, Combustion Institute, Pittsburgh, PA,
69-70 pp, 1994.
Keywords:
combustion; fire hazards; carbon monoxide; high
temperature; wood; pyrolysis
Abstract:
Building fire fatalities often occur at locations remote
from the room where the fire is actually burning. The
majority of these fire deaths are the result of smoke
inhalation, primarily due to exposure to carbon monoxide
(CO). Although causing nearly 2500 deaths per year in
the United States, the mechanisms for the formation of
CO in building or enclosure fires remain poorly
characterized. In order to test the hypothesis that
high concentrations of CO can be generated by pyrolysis
of wood in high temperature, vitiated environment, a
series of natural-gas fires, ranging rom 40-600 kW in
heat release rate, were burned inside a reduced-scale
enclosure (RSE). The ceiling and upper walls of the RSE
were lined with 6.4 mm thick plywood. During each burn,
the concentrations of CO CO2, and O2 were monitored at
two locations within the upper layer. Oxygen
calorimetry was used to monitor the total heat release
rate for each fire. Verticle temperature profiles for
two positions within the enclosure were also recorded.
Much higher levels of CO were generated with the
wood-lined upper layer than with comparable fires fueled
only by natural gas. Volume concentrations as high as
14% were observed. The fires with wood in the upper
layer had higher heat release rates and deparessed
upper-layer temperatures. The major conclusions of this
work based on the experimental findings are: 1) the
pyrolysis of wood in a highly vitiated, high temperature
environment can lead to the generation of very high
concentrations of CO in enclosure fires; 2) the overall
wood pyrolysis is endothermic for the experimental
conditions studies; and 3) the maximum mass loss rate of
wood under the experimental conditions is on the order
of 10 gs-1m-2 with the majority of released carbon being
converted to a roughly 1:1 mixture of CO and CO2.
