Combustion Products in Fire

Poisoning from toxic combustion products. In chemical fires, particularly those involving mixtures, an extremely complex mixture of gases and particulates, e.g. smoke may be produced. The composition depends upon the initial compounds involved, the temperatures attained and the oxygen supply, and is hence often unpredictable. Some gaseous compounds may derive from thermal breakdown, i.e. pyrolysis, of the chemicals rather than oxidation as illustrated in Tables 3.9 and 3.10. 

Combustion reactions in fire involve oxygen for the most part represented as Fuel(F) + oxygen(02) —> products(P)... 

In practice, the efficiency of a fired heater is controlled by monitoring the oxygen concentration in the combustion products in addition to the stack gas temperature. Dampers are used to manipulate the air supply. By tying the measuring instruments into a feedback loop with the mechanical equipment, optimization of operations can take place in real time to account for variations in the fuel flow rate or heating value. 

Harrison FL, Bishop DJ, Mallon BJ. 1985. Comparison of organic combustion products in fly ash collected by a Venturi wet scrubber and an electrostatic precipitator at a coal-fired power station. Environ Sci Technol 19(2) 186-193. 

Hartzell GE, Packham SC, Flileman FD, et al. 1976. Physiological and behavioral responses to fire combustion products. In Proceedings 4th Conference SPI Int Cell Plast, 264-270. 

The data from Miletree Run Reservoir document the presence of nearly a century of input of atmospherically transmitted coal-combustion products. In contrast to the situation at Hinkel Reservoir, we cannot identify a nearby (<25 km) anthropogenic source for this material. The likely sources are bituminous coal-fired power plants located approximately 50 km to the south and 60-70 km to the west of the site, with the sites to the west being on-average upwind from the study area. 

Purser, P.A. 2002. Toxicity assessment of combustion products, In The SFPE handbook of fire protection engineering. Quincy, Massachusetts NFPA. 

Purser, D.A. (1995) Toxicity effects of combustion products, in SFPE Handbook of Fire Protection Engineering, 2nd edn (eds P.J. Di Nennoet al.). National Fire Protection Association, Quincy, MA, pp. 85-146. 

The corrosiveness of combustion products has been considered in a variety of ways [70-72] in relation to actual fire damage as well as large-scale experiments. Electric insulation studies have been carried out [70-72] using the combustion tube apparatus to provide the data necessary for standards work. DIN EN 50267 [73-76], Section 813, provides information concerning test and performance criteria for the determination of the corrosiveness of combustion products from fires of electric origin [73-76]. 

Smoke production in fires results from incomplete combustion. It is usually thought of as being a dispersion of solid or liquid particles in a carrier gas consisting of the combustion gases and hot air. The liquid particulates are tar-like droplets or mists composed of the liquid products arising from p5rrolysis, or their partially oxidized derivatives and, of course, water. The solid component of smoke often contains carbon flakes, soot, ash and sublimed pjrrolysis products. 

Secondary smoke is produced mosdy by the condensation of water in humid or cold air. The presence of hydrogen chloride or hydrogen fluoride in the combustion products increases the extent and rate of condensation. Composition modifications to reduce primary smoke may reduce secondary smoke to some extent, but complete elimination is unlikely. The relatively small amount of smoke produced in gun firings by modem nitrocellulose propellants, although undesirable, is acceptable (102—109). 

Formation of Airborne Emissions. Airborne emissions are formed from combustion of waste fuels as a function of certain physical and chemical reactions and mechanisms. In grate-fired systems, particulate emissions result from particles being swept through the furnace and boiler in the gaseous combustion products, and from incomplete oxidation of the soHd particles, with consequent char carryover. If pile burning is used, eg, the mass bum units employed for unprocessed MSW, typically only 20—25% of the unbumed soHds and inerts exit the combustion system as flyash. If spreader-stoker technologies are employed, between 75 and 90% of the unbumed soHds and inerts may exit the combustion system in the form of flyash. 

The high temperatures in the MHD combustion system mean that no complex organic compounds should be present in the combustion products. Gas chromatograph/mass spectrometer analysis of radiant furnace slag and ESP/baghouse composite, down to the part per biUion level, confirms this behef (53). With respect to inorganic priority pollutants, except for mercury, concentrations in MHD-derived fly-ash are expected to be lower than from conventional coal-fired plants. More complete discussion of this topic can be found in References 53 and 63. 

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