Εξέταση της λιπαντικής ικανότητας των ελαφρών και μεσαίων κλασμάτων του πετρελαίου: θεωρητικό και πειραματικό μέρος

Abstract

The objective of this doctoral thesis is the evaluation of the tribological properties of automotive gasoline and diesel fuel, as well as the improvement of the latter with the addition of bio-additives and biofuels. It is listed the physicochemical and tribological properties of automotive diesel fuels, heating diesel fuels and marine diesel fuels. What is typical for diesel fuel is the distinct separation between the values of the corrected wear diameter and the values of friction across the limit of 460 κm, which is noticeable difference in gradient of the linear dependence of the variance of these two values. There were samples of marine diesel that their lubricity was inappropriate and greater than the limit of 460 micrometers. It was examined the impact of biodiesel, vegetable oils and essential oils in the middle distillates fractions of oil. The methodology used to measure gasoline lubricity is the ASTM G133 standard test method for linearly reciprocating ball-on-flat sliding wear. Taking into account the experimental condition characteristics for the assessment of lubricity of refinery streams is noticed that they are characterized by worst anti-wear properties and lubricity in relation to diesel fuels. It was measured the gasoline lubricity of mixtures that emerged from the composition of the refinery streams and correspond to commercial gasolines. The increased wear scar diameter of the refinery streams contributes to larger diameter wear for the final commercial gasolines and therefore the value of the corrected wear scar diameter depends significantly from that of the constituent refinery streams. In particular, it is evident for all 36 mixtures, the wear mechanism taking place is that of the heavy adhesive wear and mild to heavy abrasive wear, and can coexist with that of the oxidative wear. The optimum addition rate is following the mixing rules that prevail in modern refineries and specifically an optimum rate of 35% for the stream of catalytic cracking FCC unit and 26% for the stream of catalytic reformer unit were observed. It was measured the lubricity of commercial gasolines. For sulfur content below 50 ppm and potassium content of less than 5 ppm was noticed increased wear and in particular greater than 700 κm for all commercial gasoline types. The chlorine content varies with an average of 10 ppm for commercial gasolines by potentiometric titration. The presence of chlorine is certified by elemental analysis performed by SEM.