Corresponding States Method for Estimation of Upper Flammability Limit Temperature of Chemical Compounds
The accuracy and predictability of predictive methods to determine the flammability characteristics of chemical compounds are of drastic significance in the chemical industry. This work aims at continuing application of the gene expression programming (GEP) mathematical strategy to modify the existing thermophysical properties correlations available in the literature to pursue the following objectives: optimization of the number of independent parameters, amplification of the generality, and improvement of the accuracy and predictability. This work deals with presenting a simple corresponding states model to predict the upper flammability limit temperature of 1462 organic compounds from 76 chemical families. The parameters of the correlation include the critical temperature and the acentric factor of the compounds. The obtained statistical parameters including average absolute relative deviation of the results from DIPPR 801 database values (1.7, 1.8, 1.7% for training, optimization, and prediction sets, ...
Extended Adiabatic Flame Temperature Method for Lower Flammability Limits Prediction of Fuel-Air-Diluent Mixture by Nonstoichiometric Equation and Nitrogen Equivalent Coefficients
The extended adiabatic flame temperature method aims at predicting the lower flammability limits of fuel-air-diluent mixtures (including fuel mixtures and diluent mixtures) by nonstoichiometric equation and nitrogen equivalent coefficients. A cubic function is introduced to describe the relation between the critical adiabatic flame temperature and inert volume concentration. This method applies to ten compounds including methane, propane, iso-octane, ethylene, acetylene, benzene, methanol, dimethyl ether, methyl formate, and acetone for validation. A good agreement is obtained between the predicted and measured values that the average relative deviations are all below 3.6%. The sources of error are mainly attributed to three causes: First, the adiabatic flame temperature method does not take into account the heat losses from flame front to surroundings. Second, the test method and determined criterion both have a significant impact on the experimental data. Third, the functional relationship between adiab...
Chemosymbiotic bivalves and stable carbon isotopes indicate hydrocarbon seepage at four unusual Cenozoic fossil localities
Four unusual Cenozoic fossil localities are identified here as ancient hydrocarbon seep sites using palaeontological, petrological, and stable carbon isotope data. Late Eocene carbonate-cemented sandstone bodies in the Wagonwheel Mountains in California were previously suspected to represent ancient hydrocarbon seep sites, but the relatively high δ13Ccarbonate values (−12.2 to −5.0‰) suggest oil rather than methane seepage. The Oligocene fauna of the Elmira asphalt mine, Cuba, was previously interpreted as a mix of freshwater and marine taxa, but all species are here identified as belonging to marine groups, including the bivalve families Lucinidae and Vesicomyidae, whose extant members live largely in symbiosis with chemoautotrophic endosymbionts. A carbonate concretion from this site showed δ13Ccarbonate values as low as −32.2‰, which most likely indicates methane seepage. A previously unpublished Oligocene fossil locality in Atlantico, northern Colombia, is dominated by large solemyid, mytilid, lucinid, and vesicomyid bivalves, which most likely lived with chemotrophic endosymbionts. Seepage of biogenic methane without a significant contribution of thermogenic methane is indicated by δ13Ccarbonate values as low as −51.3‰. We confirm that the Pleurophopsis-dominated sites of the Heath Shale and Lomitos Chert in northern Peru are ancient seep sites, although the previous identification of Pleurophopsis peruviana as a vesicomyid is doubtful.