Fuel sampling

The Institute of Petroleum (1996) recommends that sampling be done routinely every one to six months or more often (at least twice over a three to five day period) if there is a problem. 

Containers selected to transport fuel or the fuel/water bottom to a laboratory should be impervious to the fuel. If possible, sterile glass or plastic (i.e., high density polyethylene or polypropylene) containers are suggested. The Institute of Petroleum (1996) recommends using silicone rubber stoppers or plastic screw caps with inserts to cap these bottles. All samples should be properly labeled with the company name, the location of the tank, the location within the tank where the sample was taken, the type of sample collected (either fuel, water bottom or fuel/water bottom interface) and the date and time the sample was collected. 

A bottom-sampling device, such as the Thief Sampler, can be used to obtain samples from the bottom of the fuel tank. This device has a clear thermoplastic tube with a bottom foot valve, which is operated from the top by a knob connected to the foot valve by a stainless steel control rod that runs the length of the device. Graduations on the tube exterior enable the operator to record where microbial contamination is found and the fuel tank level (Melton et al., 1988). 

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Measuring the gross heating value (mass) is done in the laboratory using the ASTM D 240 procedure by combustion of the fuel sample under an oxygen atmosphere, in a bomb calorimeter surrounded by water. The thermal effects are calculated from the rise in temperature of the surrounding medium and the thermal characteristics of the apparatus. 

The octane value of an unknown fuel sample is determined by comparing its knocking tendency to various primary reference fuels. Its measured octane is equal to the octane of the PRE which has the same knocking intensity. Knock intensity is controlled to an average value by varying the compression ratio of the CER engine. In practice, the exact value of a fuel s octane number is determined to the nearest 0.1 octane number by interpolation from two PREs that are no more than two octane numbers apart. 

Carbon residue, pour point, and viseosity are important properties in relation to deposition and fouling. Carbon residue is found by burning a fuel sample and weighing the amount of earbon left. The earbon residue property shows the tendeney of a fuel to deposit earbon on the fuel nozzles and eombustion liner. Pour point is the lowest temperature at whieh a fuel ean be poured by gravitational aetion. Viseosity is related to the pressure loss in pipe flow. Both pour point and viseosity measure the tendeney of a fuel to foul the fuel system. Sometimes, heating of the fuel system and piping is neeessary to assure a proper flow. 

A. Trisciani and F. Munari, Characterization of fuel samples by on-line LC-GC with automatic group-type separation of hydrocarbons , J. High Resolut. Chromatogr. 17 452-456(1994). 

Fuel Sample Clean Dirty Water Other... 

Figure 5.4 Schematic of the geometrical configuration for hydrogen-air flame and sofid fuel. The geometry corresponds to the experimental setup. The initial shape of the HED fuel was a circular arc segment as shown above. The relevant material properties air density = 1.91 kg/m , hydrogen density = 0.0898 kg/m . For the turbulent quantities at the inlet k = (O.OSf/miet) = 9.59 (m/s), = C fc / /(0.03Liniet) = 6360 m /s , jjkt = Cfe = 0.00248 kg/ms. For the fuel sample, m.p. is 450 K, latent heat of fusion is 72.7 J/g. Dimensions in mm. Air inlet velocity 103.3 m/s, hydrogen injection velocity 800 m/s...

The fuel sample is cooled under the prescribed conditions and, at intervals of34°F (l°C),a vacuum of200 mm water gauge is applied to draw the fuel through a fine wire mesh filter. As the fuel cools below its cloud point, increasing amounts of wax crystals will be formed. These will cause the flow rate to decrease and eventually complete plugging of the filter will occur. 

Fig. 14. Ternary diagram similar to that in Figure 4 showing the distribution of compositions of corroded metallic particles from an LWR fuel sample. Corrosive loss of Mo makes the average composition more Pd-rich.

The results on gasoline and fuel oil are presented in Tables XII and XIII, respectively. The results on gasoline for six elements are based on six aliquots. These results show that sulfur content of gasoline can be determined by INAA. The fuel oil results for 16 elements are based on seven aliquots. The sulfur content reported, 2.04%, agreed well with the NBS true value of 2.035% for the round-robin fuel sample. 

Zahradnik, P. and Swietly, H., The robotized chemical treatment of diluted spent fuel samples prior to isotope dilution analysis, J. Radioanal. Nucl. Chem., 204, 145-157, 1996. 

Mixing is commonly considered to be a fast process when compared with heating of the solid fuel sample therefore, the fuel and oxygen mixture becomes flammable almost immediately after pyrolysis starts. Pyrolysis temperatures and times are thus commonly referred to as ignition temperature (Tig) and ignition delay time (Afig) [10], and Equation 3.7 finally simplifies to... 

The energy balance at the surface of the fuel sample under radiative heating is shown in Figure 3.3 and given by Equation 3.10 ... 

FIGURE 3.3 Energy flows at the surface of the solid fuel sample. 

This simplification allows an analytical solution of the one-dimensional heat conduction energy equation. By substituting Equation 3.11 into Equation 3.10, and assuming that the total heat-transfer coefficient (hT) is equal to the sum of the convective heat-transfer coefficient (hc) and the radiative heat-transfer coefficient (hT), the following expression (Equation 3.12) defines the net heat flux (q") at the surface of the solid fuel sample. 

As can be seen from Equation 3.20, the short-time solution for the pyrolysis time, tPi is independent of the total heat-transfer coefficient term, hT = (h, + h,). Thus, the pyrolysis time tp is only a function of the energy absorbed aq" due to radiation from the radiant panel and the properties (k, p, Cp) of the solid fuel sample. 

Solving Equations 3.20 and 3.21 for the pyrolysis time t will yield a theoretical value for the time at which the solid fuel sample begins to pyrolyze and produce fuel vapors. The use of the appropriate simplified solution will allow the evaluation of the pyrolysis time t over the entire domain of the imposed incident heat fluxes. 

Prior to GC analysis, the fuel samples were stored in sealed containers at -20°C. The gas chromatograms of the neat jet fuel samples were used as the training set (see Table 9.1). The prediction set consisted of 25 gas chromatograms of weathered jet fuels (see Table 9.2). Eleven of the 25 weathered jet fuel samples were collected from sampling wells as a neat oily phase floating on the top of well water 7 of the 25 fuel samples were recovered fuels extracted from the soil near various fuel spills. The other seven fuel samples had been subjected to weathering in the laboratory. 

To better understand the problems involved with classifying gas chromatograms of Jet-A and JP-5 fuels, it was necessary to focus attention on these two fuels. Figure 9.13 shows a plot of the two largest principal components of the 85 GC peaks obtained from the 110 Jet-A and JP-5 gas chromatograms. An examination of the principal component plot revealed that Jet-A and JP-5 fuel samples lie in different regions of the principal component map. However, the data points... 

FIGURE 9.13 Principal component map of the 110 neat Jet-A and JP-5 fuel samples developed from the 85 GC peaks. The map explains 80% of the total cumulative variance. The JP-5 fuels are divided into two distinct subgroups fuel samples that lie close to the Jet-A fuels and fuel samples located in a region of the map distant from Jet-A fuels 2 = Jet-A and 5 = JP-5. (From Lavine, B.K. et al., Anal. Chem., 67, 3846-3852, 1995. With permission.)... 

The high classification success rate obtained for the weathered fuel samples suggests that information about fuel type is present in the gas chromatograms of weathered jet fuels. This is a significant finding, since the changes in composition that occur after a jet fuel is released into the environment can be a serious problem in fuel spill identification. These changes arise from microbial... 

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