Fuel oils suspended sediments

Testing for suspended water and sediment (ASTM D96) is used primarily with fuel oils, where appreciable amounts of water and sediment may cause fouling... 

Addition of fuel oil no. 2 to a laboratory marine ecosystem showed that the insoluble, saturated hydrocarbons in the oil were slowly transported to the sediment on suspended particulate material. The particulate material contained 40-50% of the total amount of aliphatics added to the system and only 3-21% of the aromatic fraction (Oviatt et al. 1982). This indicates that most aromatic hydrocarbons are dissolved in the water (Coleman et al. 1984), whereas the aliphatic hydrocarbons are not (Gearing et al. 1980 Oviatt et al. 1982). In a similar experiment, when fuel oil no. 2 was added continuously to a marine ecosystem for 24 weeks, oil concentrations in the sediment remained low until 135 days after the additions began, but then increased dramatically to levels that were 9% of the total fuel oil added (108 g/tank) and 12% of the total fuel oil saturated hydrocarbons. The fuel oil concentrations in the sediment began to decrease quite rapidly after the maximum levels were reached. The highest sediment concentrations of saturated hydrocarbons (106-527 g/g) were found in the surface flocculent layer, with concentrations decreasing with sediment depth from 22 g/g to not detectable at 2-3 cm below the sediment surface. 

Gearing PJ, Gearing IN, Pruell RJ, et al. 1980. Partitioning of no. 2 fuel oil in controlled estuarine ecosystems Sediments and suspended particulate matter. Environ Sci Technol 14(9) 1129-1136. 

Further sources of trouble with the oil produced is water and sediment present in the oil, when it is used as a fuel oil. Water causes sparking, spitting and flashback of the flame, which result in loss of heat as a result of improper combustion. Sediments such as sand and carbon, etc. cause the erosion of burner tips, pump parts and sensitive control valves, etc. Also, some chemical compounds present in an oil will absorb oxygen from air or water, to form new compounds. Unfortunately, some of these chemical compounds are insoluble in the oil, with the result that they will either remain suspended in the oil or will drop to the bottom of the tank. They must not reach the suction lines in a storage tank. 

In general, the volume received or delivered is calculated from the observed gauge readings. Corrections are made for any free water and sediment as determined by the gauge of the water level in the tank. The resultant volume is then corrected to the equivalent volume at 15.6°C (60°F) by use of the observed average temperature and the appropriate volume correction table (ASTM D-1250). When necessary, a further correction is made for any suspended water and sediment that may be present in materials such as crude petroleum and heavy fuel oils. 

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