ASTM D7060 Test Method for Determination of the Maximum Flocculation Ratio and Peptizing Power in Residual and Heavy Fuel Oils (Optical Detection Method)
4. Summary of Test Method
4.1 Six portions of the sample are diluted in various ratios with 1-methylnaphthalene. Each solution is inserted into the automatic apparatus, and titrated with cetane until flocculation of asphaltenes is detected by the optical probe. The first two solutions are titrated with cetane in coarse determinations in which the flocculation ratio is decreased in 5 % steps. The coarse determinations help to establish suitable starting values for the fine determinations, in which the flocculation ratio is decreased in 1 % steps. The four flocculation ratios at critical dilution, measured during the fine determinations, are used to calculate the maximum flocculation ratio of the sample's asphaltenes and the peptizing power of the sample's oil medium.
5. Significance and Use
5.1 Asphaltenes are naturally occurring materials in crude petroleum and petroleum products containing residual material. The asphaltenes are usually present in colloidal suspensions, but they may agglomerate and flocculate if the suspension of asphaltene molecules is disturbed through excess stress or incompatibility. This test method provides compatibility parameters, which can be used to assess stability reserve and compatibility.
5.2 A blend is considered stable when the blend's peptizing power is higher than the blend's maximum flocculation ratio; both of them can be calculated using empirical blend rules. Refineries and terminal owners can prevent the flocculation of asphaltenes due to incompatibility by assessing the compatibility of fuels beforehand.
NOTE 3 - See Appendix X1 for an example of prediction of compatibility.
6. Interferences
6.1 High content of insoluble inorganic matter (sediment) has some interference in this test method. In this case, the insoluble matter shall be removed by filtration according to Test Method D4870.
6.2 The presence of wax, present in paraffinic crudes or fuels from such crudes, does not interfere.
