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Carbon Monoxide Formation in Fires by High-Temperature Anaerobic Wood Pyrolysis.


pdf icon 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.