Abstract
As opposed to gasoline, diesel oil has a lower limit temperature for its use in internal combustion engines (ICEs), which ranges between -7 ºC and -20 ºC for the summer/winter formulation: it is therefore close to the average winter temperature typical of some European countries. In approaching such temperature, the formation of paraffins alters the physical characteristics of diesel oil (viscosity in particular) and makes it impossible to be used in ICEs. The same, aggravated problem is presented also by biodiesel and diesel-biodiesel blends, which are very interesting given their benefits in terms of performance and pollutant reduction in conventional compression-ignition engines (e.g., agricultural and operating machinery, cogeneration systems). Some varieties of biodiesel, such as biodiesel from palm oil, solidify at 13 ºC, whilst others, more suitable for winter temperatures, solidify at -10 ºC (biodiesel from canola seeds), which is nevertheless a higher temperature than that of diesel oil. In this work, a simple industrial freezer set at -21 ºC was used to assess the freezing temperatures of many solutions of multiple components with different freezing points (diesel-biodiesel blends). The illustrated procedure use slow-cost and simple equipment thus allowing to reproduce similar experiments in industrial environments. The elaborations carried out have included the use of polynomial functions to fit the data and the identification of temperature tangency traits. Although the results are not in the form of the usual significant temperatures indicated by standards as cold-flow properties for fuels (i.e., pour point, cloud point, cold filter plugging point), they are substantially aligned with the literature data. However, the outcomes in the form of upper and lower liquid-to-solid temperatures are very interesting and useful to give the experimenters/users practical indications about the opportunity of using diesel-biodiesel blends with different compositions.