Constituents of the fuel

The question of the compatibility of metals and alloys with carbon and carbonaceous gases has assumed considerable importance in connection with the development of the gas-cooled nuclear reactor in which graphite is used as a moderator and a constituent of the fuel element, and carbon dioxide as the coolant. Tests of up to 1 000 h on a series of metals and nickel-containing alloys under pressure contact with graphite at 1 010°C" showed that only copper was more resistant than nickel to diffusion of carbon and that the high-nickel alloys were superior to those of lower nickel content. The more complex nickel-chromium alloys containing titanium, niobium and aluminium were better than the basic nickel-chromium materials. 

Riviere et al. (1999) used the isolated perfused porcine skin flap model to study absorption and disposition of JP-8. The percutaneous absorption and cutaneous disposition of topically applied neat Jet-A and JP-8 jet fuels were assessed by monitoring the absorptive flux of the marker components 14C naphthalene and 3H dodecane simultaneously. Absorption of 14C hexadecane was estimated from JP-8. Data were not reported in absolute amounts or concentrations. Instead, the objectives were to determine the relative absorption of the individual marker components from jet fuel, and the effect of a specific jet fuel s composition on the absorption of a specific marker. Having evaluated the absorption of only three of the 228 major nonadditive hydrocarbon constituents of the fuels, the authors stated that this is insufficient information to conduct risk assessments on jet fuels. However, the authors conclusions are informative. Naphthalene penetrated the skin more rapidly than dodecane or hexadecane, but the latter compounds had a larger fraction of the dose deposited in the skin. There were also differences in naphthalene and dodecane absorption and skin deposition between the fuels. These findings reinforce the difficulty of predicting risk for complex mixtures such as jet fuels. 

The chemical reactions occurring within an oil droplet subject to oxidising conditions at high temperatures are extremely complex. The extent of the reactions will depend not only on the chemical constituents of the fuel, but also on the droplet size as it affects the rate of diffusion of volatile components through the... 

The nonvolatile oxidation products of the inorganic constituents of the fuel (e.g., sodium and potassium) are left as ash and contribute to the formation of corrosive deposits (Argonne, 1990). When pulverized coal is used, a large proportion of the ash is carried out of the combustion chamber with the exhaust gas stream and has to be removed as completely as possible, usually by use of electrostatic precipitators. 

Oxides of nitrogen (primarily NO and NO2), also have a role in the generation of acid rain at low altitudes and play a crucial role in the ozone balance at higher altitudes . Production during combustion involves the high temperature reaction of N2 and O2 from air in the combustion chamber and from nitrogenous constituents of the fuel. NO is the main product and... 

Coating will form more easily in the preheating and in the calcining zone according as the feed material contains more alkali salt melt. Secondary constituents of the fuel, such as compounds of sulphur and chlorine, promote such coating formation. 

The fuel added to the reactor will have a high concentration of UF4 with respect to the process fuel,. so that additions to overcome burnup will require transfer of only a small volume similarly, thorium-bearing molten. salt may be added at any time to the fuel system. The thorium, in addition to being a design constituent of the fuel salt, may be added in amounts re( uired to serve as a nuclear poison. 

The molecular size of the product is limited insofar as the reaction is terrninated at the dimer or trimer stage. Thus the process is more properly termed oligomerization. The four- to twelve-carbon compounds required as the constituents of Hquid fuels are the prime products. 

As a hard, high melting carbide and possible constituent of UC-fueled reactors, zirconium carbide has been studied extensively. The preparation, behavior, and properties of zirconium and other carbides are reviewed in Reference 132, temperature-correlated engineering property data in Reference 133 (see also Carbides). 

Fuel system fouling is related to the amount of water and sediment in the fuel. A by-product of fuel washing is the desludging of the fuel. Washing rids the fuel of those undesirable constituents that cause clogging, deposition, and corrosion in the fuel system. The last part of treatment is filtration just prior to entering the turbine. Washed fuel should have less than. 025% bottom sediment and water. 

The constituents of residual fuels are more complex than those of gas oils. A major part of the polynuclear aromatic compounds, asphaltenes, and heavy metals found in crude oils is concentrated in the residue. 

The effectiveness of incineration has most commonly been estimated from the heating value of the fuel, a parameter that has little to do with the rate or mechanism of destraction. Alternative ways to assess the effectiveness of incineration destraction of various constituents of a hazardous waste stream have been proposed, such as assessment methods based on the kinetics of thermal decomposition of the constituents or on the susceptibility of individual constituents to free-radical attack. Laboratory studies of waste incineration have demonstrated that no single ranking procedure is appropriate for all incinerator conditions. For example, acceptably low levels of some test compounds, such as methylene chloride, have proved difficult to achieve because these compounds are formed in the flame from other chemical species. 

Hennig [40] has applied ultraviolet spectroscopy to the determination of aromatic constituents of residual fuel oil in hexane extracts of marine sediment samples. Examination of the ultraviolet spectra of samples of an oil pollutant from a beach and crude oil, at various concentrations, revealed strong absorption maxima at approximately 228nm and 256nm. The ratio of the peak heights at these wavelengths is constant for a particular oil, and is independent of concentration. These permit quantitative analysis of sediment samples many months after an oil spill. 

Wilson and Madsen [152] used the metabolic pathway for bacterial naphthalene oxidation as a guide for selecting l,2-dihydroxy-l,2-dihydronaphthalene as a unique transient intermediary metabolite whose presence in samples from a contaminated field site would indicate active in situ naphthalene biodegradation (Fig. 26). Naphthalene is a component of a variety of pollutant mixtures. It is the major constituent of coal tar [345], the pure compound was commonly used as a moth repellant and insecticide [345], and it is a predominant constituent of the fraction of crude oil used to produce diesel and jet fuels [346]. Prior studies at a coal tar-contaminated field site have focused upon contaminant transport [10,347], the presence of naphthalene catabolic genes [348, 349], and non-metabolite-based in situ contaminant biodegradation [343]. 

The character of fuel oil generally renders the usual test methods for total petroleum hydrocarbons (Chapters 7 and 8) ineffective since high proportions of the fuel oil (specifically, residual fuel oil) are insoluble in the usual solvents employed for the test. In particular, the asphaltene constituents are insoluble in hydrocarbon solvents and are only soluble in aromatic solvents and chlorinated hydrocarbons (chloroform, methylene dichloride, and the like). Residua and asphalt (Chapter 10) have high proportions of asphaltene constituents, which render any test for total petroleum hydrocarbons meaningless unless a suitable solvent is employed in the test method. 

Coke does not offer the same potential environmental issues as other petroleum products (Chapter 10 and above). It is used predominantly as a refinery fuel unless other uses for the production of a high-grade coke or carbon are desired. In the former case, the constituents of the coke that will release environmentally harmful gases such as nitrogen oxides, sulfur oxides, and particulate matter should be known. In addition, stockpiling coke on a site where it awaits use or transportation can lead to leachates as a result of rainfall (or acid rainfall) which are highly detrimental. In such a case, application of the toxicity characteristic leaching procedure... 

The coupling of these improvements needs to be proven to meet endurance goals operation at pressure will definitely require design changes. The studies described in the recent literature provide updated information on promising development of the electrodes, the electrolyte matrix, and the capability of the cell to tolerate trace constituents in the fuel supply. The objectives of these works are to increase the life of the cells, improve cell performance, and lower cell component costs. Descriptions of some of this work follow. 

Fuel oils are petroleum products that are used in many types of engines, lamps, heaters, furnaces, stoves, and as solvents. Fuel oils come from crude petroleum and are refined to meet specifications for each use. Fuel oils are mixtures of aliphatic (open chain and cyclic compounds that are similar to open chain compounds) and aromatic (benzene and compounds similar to benzene) petroleum hydrocarbons. In addition, they may contain small amounts of nitrogen, sulfur, and other elements as additives. The exact chemical composition (i.e., precise percentage of each constituent) of each of the fuel oils discussed in this profile may vary... 

Respiratory Effects. Pleural effusions and alveolar infiltrations were noted in a man who had washed his hair with an unknown amount of diesel fuel (Barrientos et al. 1977). The relative contributions from inhalation and dermal exposure could not be distinguished in this case. There was no throat irritation in six volunteers following a 15-minute exposure to a concentration reported to be 140 mg/m of deodorized kerosene vapor (Carpenter et al. 1976). The authors used a hot nichrome wire for the volatilization of their test material and reported that the concentration was probably the "highest attainable concentration at which vapor analysis is representative of liquid analysis." The air saturating concentration of kerosene is considered to approximate 100 mg/m (room temperature and 760 mmHg) and is dependent on the constituents of the mixture. 

The partitioning of fuel oil no. 2 and kerosene into drinking water after 17 hours of incubation resulted in only 1.0% of the fuel oil and 0.7% of the kerosene being dissolved in the water. Further analysis of these fuels indicated that although each compound contains approximately 50% aliphatic hydrocarbons (by weight percent), the water-soluble fractions contained primarily aromatic constituents (>93%) including benzenes and naphthalenes as shown below (Coleman et al. 1984) ... 

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