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Safety and Flammability Analysis for Fuel–Air–Diluent Mixtures Plant
Published in Mihir Kumar Purkait, Piyal Mondal, Murchana Changmai, Vikranth Volli, Chi-Min Shu, Hazards and Safety in Process Industries, 2021
Mihir Kumar Purkait, Piyal Mondal, Murchana Changmai, Vikranth Volli, Chi-Min Shu
A series of explosions blamed on propylene leaks from underground pipelines killed 32 people and injured more than 300in the southern Taiwanese city of Kaohsiung in 2014. The explosions resulted in a series of major fires and significantly damaged property and roads. Flammability limits are key characteristics applied to determine the fire and explosion (F&E) dangers of gases and vapors. The lowest and highest concentrations capable of sustaining the propagating flame are the lower (LFL) and upper flammability limits (UFL), respectively (Mannan, 2005; Crowl and Louvar, 2011). The flammability limits of a given fuel depend on several factors, including initial temperature, initial pressure, system scale and configuration, ignition energy, flame stretch, radiation reabsorption, the presence of inert gases, and others (Mannan, 2005; Ju et al., 2001). In industrial processes, an inert gas is often added to combustible mixtures to prevent the F&E hazard, especially in oxidation processes. Nonetheless, much more flammability limit data is published for pure fuel substances than for fuel/inert gas mixtures. Deriving such data in Taiwan is costly. Therefore, a process to estimate the flammability limits of fuel/inert gas mixtures would provide practical benefits.
Fundamentals of Source Assessment
Published in Jack Daugherty, Assessment of Chemical Exposures, 2020
To sustain combustion of vapors over a liquid, the bulk temperature of the liquid must be raised to the point where the vapor generation by evaporation is equal to the vapor consumption by combustion. This higher temperature is called the fire point. Definitions of hazardous by EPA, OSHA, and DOT are based on the flash point, but, it is the fire point that interests the modeling engineer. Vapor-air mixtures only ignite and burn if both the temperature and the concentration is right. In fact, for a given fuel vapor-air mixture, only a specific range of compositions will burn. Anything beneath that range is called fuel lean or air rich and any composition beyond the range is called fuel rich or air lean. The range itself is called the flammability limits. The point at which the mixture becomes fuel lean is called the lower flammability limit (LFL). The upper flammability limit (UFL) is the upper end of the range where the mixture is too rich in fuel.
Combustion hazards
Published in J. F. Griffiths, J. A. Barnard, Flame and Combustion, 2019
J. F. Griffiths, J. A. Barnard
The flammability limit is defined as the composition of fuel + air at which a flame just fails to propagate from a spark (or similar ignition source). As discussed in Chapter 3, flammable mixtures exhibit a lean (or lower) and rich (or upper) limit, which fall either side of the stoichiometric composition. It is important to measure the flammability limit in a sufficently large vessel that a self-sustained flame can be established. The EEC test requires a tube of minimum diameter 50 mm and minimum height 300 mm. The spark electrodes are located 60 mm from the bottom, with a spark gap of 3–5 mm. A standard induction spark, 0.5 s duration, is generated at 10–15 kV with maximum power input of 300 W. The test is performed at room temperature on mixtures that are successively enriched in fuel (in steps of 1% by volume) until ignition is obtained at the lean limit. The lean flammability limit (or LEL, lower explosion limit) is of greater practical importance than the rich limit, since it is leakage of a gas or vapour into the atmosphere that normally presents the ignition hazard. The LEL for the alkanes is at a molar volume in air which is approximately 60% of that in the stoichiometric mixture (Table 3.1 [23]).
Equivalence Ratio Influence on the Flame Suppressant Concentration of 2-BTP and Novec 1230
Published in Combustion Science and Technology, 2020
V. I. Babushok, V. R. Katta, F. Takahashi
A decrease in the fuel concentration in the air/fuel mixture or increase in the inhibitor concentration leads to the flame extinguishment. The conditions corresponding to the flame extinguishment determine the flammability limits: the lower flammability limit (LFL, lean mixtures) and upper flammability limit, rich mixtures. Under normal conditions, the heat losses from the reaction zone and fluid dynamic disturbances extinguish flames at the flammability limits. For typical ambient conditions, it is difficult to observe flames with burning velocities below 1–4 cm/s (Ju, Masuya, Ronney 1998; Rozlovski 1980; Spalding 1957). The burning velocity of 5 cm/s was considered as the burning velocity at the flammability limit (Egerton and Powling 1948; Westbrook 1982). This value is, to some extent, device dependent. Nonetheless, it can be used as a metric for flammability limits, and it was used earlier for the estimation of flammability limits (Babushok, Linteris, Meier 2012; Westbrook 1982). The assumed level of burning velocity at the flammability limit actually defines the level of the heat release rate which becomes comparable with the heat losses at the flammability limits.
Prediction of upper flammability limits for fuel mixtures using quantitative structure–property relationship models
Published in Chemical Engineering Communications, 2019
Beibei Wang, Kaili Xu, Qingsheng Wang
The upper flammability limit (UFL) is the highest concentration of a combustible chemical in a gaseous mixture with air which can propagate flame with the presence of an ignition source (High and Danner, 1987) and it is an important parameter in handling and storing of combustible chemicals. For the determination of UFLs, experimental tests are the main sources and experimental values are always desirable (Kondo et al., 2008). However, experimental UFLs are very expensive to obtain thus they are extremely scarce. Even more, for flammable and explosive chemicals, experimental tests are dangerous. When it is not practical to determine this property by experimental means, developing a reliable alternative method can be very helpful (High and Danner, 1987; Lazzús, 2010).