Ways to Improve the Effectiveness of Depressant Additives for the Production of Winter and Arctic Diesel Fuels

Abstract

Diesel fuel is the main fuel for transport and power generation for remote areas, especially the Arctic. For these territories, it is important to produce low-freezing fuel grades. The most effective way to improve the low-temperature properties of diesel fuels (cloud point, pour point, and cold filter plugging point) is the use of depressant additives. Existing research shows that the depressant additives’ effectiveness is influenced by many factors. The most important factors are diesel fuel composition, additive concentration, and the temperature of additive introduction into the fuel (adding temperature). The purpose of this work is to find ways to increase the efficiency of depressant additives for the production of low-freezing diesel fuels by choosing the most effective additive concentration and adding temperature for fuels of various compositions. During the work, low-temperature properties were determined and the effectiveness of three depressant additives was assessed on four samples of diesel fuel at four concentrations (0.5, 1.0, 2.0, and 5.0 c.u., where c.u. (conditional unit) is the concentration recommended by the manufacturer of the additives). In addition, low-temperature properties for blends of six depressant additives and two samples of diesel fuel at five adding temperatures (15, 25, 35, 45, and 55 °C) were determined. In this work, in contrast to existing works, it was established for the first time that the composition of the fuel affects not only the depressant additives effectiveness, but also the dependence of the additive effectiveness on the concentration in which it is used. It is shown that the higher the content of paraffins in the composition of the diesel fuel, the less the depressant additive’s effectiveness in relation to cold filter plugging point depends on the concentration and the more the depressant additive’s effectiveness in relation to the power point depends on the concentration. An inverse relationship was revealed for the content of aromatic hydrocarbons in diesel fuel. It was also found for the first time that an increase in the adding temperature of depressant additives up to 35–55 °C enhances the effectiveness of their action in relation to the cold filter plugging point (maximum at 6–7 °C). It is shown that the greater additive effect on the cold filter plugging point of the diesel fuel, the more strongly the depressant effectiveness depends on the adding temperature. The work provides recommendations for obtaining the most low-freezing classes of fuel based on the samples considered. The regularities identified in the work will make it possible, depending on the composition of the fuel, to select the optimal concentration of the additive and the temperature of its adding, which will increase the efficiency of the additives, as well as the volume of low-freezing grades of diesel fuel production.