Residual fuel analyses

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. 

Detailed analysis of residual products, such as residual fuel oil, is more complex than the analysis of lower-molecular-weight liquid products. As with other products, there are a variety of physical property measurements that are required to determine that residnal fnel oil meets specifications. But the range of molecular types present in petrolenm prodncts increases significantly with an increase in the molecular weight (i.e., an increase in the number of carbon atoms per molecule). Therefore, characterization measurements or studies cannot, and do not, focus on the identification of specific molecular structures. The focus tends to be on molecular classes (paraffins, naphthenes, aromatics, polycyclic compounds, and polar compounds). 

Elemental analysis of fuel oil often plays a more major role that it may appear to do in lower-boiling products. Aromaticity (through the atomic hydrogen/carbon ratio), sulfur content, nitrogen content, oxygen content, and metals content are all important features that can influence the use of residual fuel oil. 

A variety of miscellaneous elements can also occur in a residual fuel oil fraction. For example, chlorine is present as a chlorinated hydrocarbon and can be determined (ASTM D808, D1317, D6160). A rapid test method suitable for analysis of samples by nontechnical personnel is also available (ASTM D5384) and uses a commercial test kit where the oil sample is reacted with metallic sodium to convert organic halogens to halide, which is titrated with mercuric nitrate using diphenyl carbazone indicator. Iodides and bromides are reported as chloride. 

The pour point of residual fuel is not the best measure of the low-temperature handling properties of the fuel. Viscosity measurements are considered more reliable. Nevertheless, residual fuels are classed as high pour and low pour fuels. Low-pour-point fuels have a maximum pour point of 60°F (15.5°C). There is no maximum pour point specified for high-pour-point residual fuels. A residual oil paraffin carbon number analysis is provided in FIGURE 3-1. 

In an analysis of airborne coal fly ash, Natusch and co-workers (50) found that 12 elements, i.e., Pb, Tl, Sb, Cd, Se, Zn, As, Ni, Cr, S, Be, and Mn, were concentrated in the smallest diameter particles. Mercury, although not studied, was expected to follow suit because of its high volatility and probable deposition on small particles. Toca and Berry reported similar findings for lead and cadmium (5). Atmospheric vanadium (59, 60) as well as selenium, antimony, and zinc (61) arising principally from residual fuel combustion also showed a similar pattern. The health risk of this concentration phenomenon is enhanced because of the magnitude of fine particulate emissions and the ease with which these particles bypass particle collection devices, resist fallout, and readily disseminate (50). 

Some general applications of TG-FTIR are evolved gas analysis, identification of polymeric materials, additive analysis, determination of residual solvents, degradation of polymers, sulphur components from oil shale and rubber, contaminants in catalysts, hydrocarbons in source rock, nitrogen species from waste oil, aldehydes in wood and lignins, nicotine in tobacco and related products, moisture in pharmaceuticals, characterisation of minerals and coal, determination of kinetic parameters and solid fuel analysis. 

The experimental furnace is a vertically oriented laminar flow drop tube furnace having a 30 cm long uniformly hot test section with optical access. The fuel droplet array is introduced on the logitudinal axis concurrently with the ambient gas. The droplet stream is interrupted at several points in its trajectory by a sampling probe inserted axially from the base of the furnace. The probe quenches and transports the entire flow to a sampling train which recovers the fuel droplet residue for analysis. The above process is repeated at several furnace temperatures for each fuel. A detailed description of the system is to be found in references (3) and (4). 

Two methods are given here for the determination of metals in crude and residual fuel oils the dilution—flame analysis method and an ashing procedure. Because of the nature of these oils simple dilution with solvent may leave undissolved solids in the solvent to be presented to the spectrometer. This could give rise to a decrease in the precision of the method. The ashing procedure overcomes this difficulty but is more time consuming. The method of choice will depend on whetiier the analytical emphasis is placed on speed of analysis or precision. Where very low levels of Ni or V are important it may be possible to modify the melhod given under fuel oils (Section IV.B.2.). 

The determination of metals in crude and residual fuel oil by dilution and flame analysis... 

Test methods of interest for hydrocarbon analysis of residual fuel oil include tests that measure physical properties such as elemental analysis, density, refractive index, molecular weight, and boiling range. There may also be some emphasis on methods that are used to measure chemical composition and structural analysis, but these methods may not be as definitive as they are for other petroleum products. 

Testing residual fuel oil does not suffer from the issues that are associated with sample volatility, but the test methods are often sensitive to the presence of gas bubbles in the fuel oil. An air release test is available for application to lubricating oil (ASTM D-3427, IP 313) and may be applied, with modification, to residual fuel oil. However, with dark-colored samples, it may be difficult to determine whether all air bubbles have been eUmi-nated. And, as with the analysis and testing of other petroleum products, the importance of correct sampling of fuel oil cannot be overemphasized, because no proper assessment of quality can be made unless the data are obtained on truly representative samples (ASTM D-270, IP 51). 

High ionizing voltage mass spectrometry (ASTM D-2786, ASTM D-3239) is also employed for compositional analysis of residual fuel oil. These methods require preliminary separation with elution chromatography (ASTM D-2549). A third method (ASTM D-2425) may be applicable to some residual fuel oil samples in the lower molecular weight range. 

In an attempt to provide a trace element standard for use in petroleum analysis the National Bureau of Standards and the Environmental Protection Agency recently distributed a Residual Fuel Oil (and other materials) for analysis to more than 40 laboratories. The results obtained and a discussion of the results has been presented by La Fleur and Van Lehmden. ... 

The data present a disturbing picture of the state of trace analysis of petroleum. Tables 5.9 and 5.10 show the results of the interlaboratory comparison of Ni and V in the Residual Fuel Oil (RFO). The largest range (13.6-52.4 yg/g) of Ni values was obtained by atomic absorption. Smaller ranges were shown by other methods. 

With modem methods of analysis of atmospheric particulate matter, especially neutron activation, one can determine atmospheric concentrations of vanadium in remote locations. Comparisons of vanadium concentrations with those of other elements in remote areas suggest that much of the observed vanadium orignates from mans activities. Atmospheric vanadium concentrations in most United States cities are less than 20 ngrams/meter, but many cities in the northeastern United States have up to several figrams/meter. A study of Boston shows that residual fuel combustion is the only source of vanadium of sufficient magnitude to produce the concentrations observed. Because of the high sensitivity for its analysis, vanadium can serve as an indicator of wide-scale movement of particulates from this identified anthropogenic source. 

The problem is that the analysis of petrochemical samples can be extremely difficult because of the complex nature of crude oils, distUlates, residues, fuel oils, petroleum products, organic solvents, and all the varions by-products from refining crude oil. These complex oil-based samples pose major problems for any analytical technique, owing to the difficulty of introducing them directly into the instrument. So, the analytical challenge for any trace element technique being used in the... 

The above TGA and elemental analysis studies are consistent with Van Krevelen s two step model for polymer charring (2) in which a polymer first rapidly decomposes at 500°C to fuel gases and a primary char residue characterized by modestly high hydrogen content. On further heating above 550°C, this primary char is slowly converted in a second step to a nearly pure carbon residue by the loss of this hydrogen. 

The potential of ultrahigh-resolution mass spectrometry for the analysis of complex chemical mixtures is particularly illustrated by FT-ICR-MS which definitely sets a new standard. For example, ultrahigh-resolution was applied to separate several thousand components in crude oil, [85,86] fuels, [87,88] or explosion residues. [89]... 

Cost. Bat telle Columbus ( 5) recently estimated the 1980 cost of readying timber residue, cull and dead trees for fuel conversion in the state of Vermont. The analysis considered procurement (stumping), harvesting, chipping and transportation over 40 kilometres, but omitted fertilization costs. Based on green wood (45% moisture, 10.9 GJ/green tonne), the wood cost was estimated as 16.40/green tonne. 

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