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From page 9... ... CHEMICAL THERMODYNAMICS AND FIRE PROBLEMS DANIEL R STULL Thermal Research Laboratory, The Dow Chemical Company Introduction Throughout history there has been a contmuing struggle to subordinate fire to the service of man, but the mastery is mcomplete The usual concept of a fire is the umon of a fuel with oxygen, but m its most general aspect, we must regard fire as a chemical reaction The study of chemical reactions is a relatively recent activity of man that has provided many benefits, but agam the mastery is mcomplete, smce we still expenence reactions that rage out of control A fire is a special kind of reaction; it is spontaneous, it evolves heat, it is not reversible, and the reaction products are generally smaller molecules and of greater number than are the reactant molecules. Read the entire page →
From page 10... ... 162 PIBE RESEARCH The Significance of Thermochemistry The word THERMODYNAMICS denotes the dynamic or mechamcal action of heat, while the word THERMOCHEMISTRY expresses the relations existmg between chemical action and heat The laws of thermodynamics and thermochemistry are Imked together and govem the behavior of all the tangible matenal m the umverse The first and second laws of thermodynamics were developed and proven dunng the nmeteenth century while the laws of thermochemistry are a development of the twentieth century' which partially accounts for the fact that they have not been as widely apphed as is fully warranted. Thermochemistry is a quantitative science m which a man of action can have the satisfaction of domg somethmg no one else has done, and of makmg a tme contnbution to world knowledge. Read the entire page →
From page 11... ... ABSTRACTS AND REVIEWS 163 This equihbrium constant K for the reaction is related to the standard Gibbs energy change by -RT] Read the entire page →
From page 12... ... 1 6 4 FIRE RESEARCH the most stable products at T m a x and balances the stoichiometry of the reactants and products. Once the product composition is established, the enthalpy of the products from 2 9 8 ° K to T m a x is compared with the enthalpy of the reaction. Read the entire page →
From page 13... ... ABSTRACTS AND REVIEWS 165 L J 60 > 50 a = Stoichiometric for combustion to CO2 and b= Minimum flammable oxygen concentration c = Lower flammable limit in oir d = Upper flammable limit in air F R O M : M Read the entire page →
From page 14... ... 166 FIRE RESEARCH TABLE I Temperature and enthalpy generated by flammable compositions in the methane-mtrogen-oxygen system CHi N, 0, Enthalpy CH, N, 0, Enthalpy (mole) (mole) Read the entire page →
From page 15... ... ABSTRACTS AND REVIEWS 167 3000 h T ' K 2800 2600 2400 2200 2000 1800 1600 1400 1200 1000 800 80 70 60 50 40 30 20 10 0 MOLE % NITROGEN I 1 I I I I L _ 10 20 30 40 50 60 70 MOLE % METHANE F I G 2 Flame temperatures for the system CH<-Nj-Oj Read the entire page →
From page 16... ... 168 FIRE RESEARCH hydrogen chloride decomposes to HCl H-fCl, formmg atomic hydrogen and chlorine. These relationships are shown graphically in Figure 4 Note that at no time is free diatomic chlorme formed m the presence of hydrogen Atomic chlorme and atomic hydrogen are formed m equal amoimts from the decomposition of hydrogen chlonde and -reach 1 ppm at 1000°C, 10 ppm at 1200°C. Read the entire page →
From page 18... ... 170 FIRE RESEARCH and carbon monoxide (1 to 30 ppm) below 800°C, which increase in concentration as the temperature is raised; at higher temperatures, there are trace amounts of atomic chlorme (1 to 1000 ppm) Read the entire page →
From page 20... ... 172 F I R E RESEARCH is increased. With stoichiometric air, the graphite is all oxidized to carbon dioxide and there is no soot. Read the entire page →
From page 23... ... ABSTRACTS AND REVIEWS 175 IS present in the 0.25 and 0 50 air calculations At stoichiometnc air, mtnc oxide is also formed. Figure 11 shows the concentrations of both atomic and diatomic hydrogen, and how they decrease as the au- rises m concentration Figure 12 shows the concentrations of hydrogen chloride, and how they decrease as air is added. Read the entire page →
From page 25... ... ABSTRACTS AND REVIEWS 177 calculated equilibria between phosgene, carbon monoxide, and chlorine, according to the equation COCI2 5=i CO+CI2. The plot shows that phosgene is stable below about 200°C and, as the temperature is raised above 200°C, the phosgene begins to decompose to chlorine and carbon monoxide, and is all substantially decomposed by about 1000°C. Read the entire page →
From page 27... ... ABSTRACTS AND REVIEWS 179 presence of air, an almost quantitative yield of hydrogen chlonde is obtained. The only other combustion products of any consequence are carbon monoxide, carbon dioxide, and water. Read the entire page →
From page 31... ... ABSTRACTS AND REVIEWS 183 produce. The secondary hazard is the difference between the self decomposition (denoted by subscnpt d) Read the entire page →
From page 32... ... 184 FIBE BESEABCH T A B L E I I I Calculated decomposition and complete oxidation temperatures for NFPA Chemical Reactivity rated compounds State NFPA To-Ti ^1. Acetone 0) Read the entire page →
From page 33... ... ABSTRACTS AND REVIEWS 185 relatively long times to achieve. I t is for this reason that these calculations are spoken of m the potential sense. Read the entire page →
From page 34... ... 186 FIRE RESEARCH References 1 G N L E W I S AND M RANDALI., revised by K S P I T Z E R AND L B R E W E R Thennodynamics, 2nd ed , McGraw-Hill Book Company (1961) 2 D R S T U L L The American Scientist, 59, 734^743 (1971) Read the entire page →

From page 9...

... CHEMICAL THERMODYNAMICS AND FIRE PROBLEMS DANIEL R STULL Thermal Research Laboratory, The Dow Chemical Company Introduction Throughout history there has been a contmuing struggle to subordinate fire to the service of man, but the mastery is mcomplete The usual concept of a fire is the umon of a fuel with oxygen, but m its most general aspect, we must regard fire as a chemical reaction The study of chemical reactions is a relatively recent activity of man that has provided many benefits, but agam the mastery is mcomplete, smce we still expenence reactions that rage out of control A fire is a special kind of reaction; it is spontaneous, it evolves heat, it is not reversible, and the reaction products are generally smaller molecules and of greater number than are the reactant molecules.