Fuel Oils

Development of a method for the characterization of the oxidation stability of domestic heating oil and domestic heating oil with alternative components using chemiluminescence

Modern burner systems for heating oils have a complex mixture preparation that is adapted specifically to a fuel according to DIN 51603 – Part 1. The focus of the domestic heating market lies – right after the introduction of heating oil low-sulphur – on the development of liquid fuels regarding their substitution with alternative and biogenic components. The quality and stability of the fuel has to be secured over long storage periods and represents a criterion for the operation safety of heating oil burner systems. Under the influence of atmospheric oxygen, temperature, light and further influencing factors a thermo-oxidative degradation of fuels can occur during the storage of fuels in the tank units of heating oil burner systems. In this case a formation of oil ageing products takes place and leads to changes of the chemical- physical characteristics of the fuels. The oxidation stability represents a parameter that serves to evaluate the stability of fuels. Several analysis methodologies exist for the determination of the oxidation stability of mineral oil based products. These standardized testing methodologies have been adapted to the respective application (lubricants, thermal oils, pure mineral oil based products, etc.). In recent years several methodologies have been developed in the fuel sector. Primarily they are applicable for the stability determination of pure products (diesel, heating oil, biodiesel, vegetable oil). But none of these methodologies have turned out to be suitable for blends of mineral oil based and biogenic, regenerative products without restrictions yet. Therefore, the project’s aim was to develop a process that serves to determine the oxidation stability of heating oil – FAME-/ heating oil – vegetable oil-blends clearly. Due to a directed energy input by means of the process of chemiluminescence, statements about the storage stability and the thermal stability of blends can be made. During the process the ageing of blend components and of the heating oil are taken into consideration. As a result, ageing processes and products of pure heating oil as well as biogenic components can be determined. It was shown that the process is applicable to blends up to an admixture of at least 20 %(V/V) of biogenic components, whereby blends with higher admixture shares can be analyzed as well. According to DIN SPEC 51603 – 6 “Heating Oil Alternative” the admixture of FAME is limited to 20 %(V/V) and the admixture of vegetable oil to 5 %(V/V) because of the distillation range. On the basis of these investigations it could be shown how oxidation products influence the signal process of the chemiluminescence radiation and how they can be correlated by a measurable physical value. Moreover, a new evaluation criterion has been developed. By means of this criterion a good reproducibility – regarding the determination of the oxidation stability according to the chemiluminescence methodology for non-aged fuels – can be achieved. The fuel characteristic decrease in the stability of the tested fuels can be represented only partially by the chemiluminescence process, as the measured values are subject to fluctuations.

The IGF project (16342 N) of the Research Association for Petroleum, Natural Gas and Coal was funded by the Federal Ministry of Economics and Technology via the AiF within the framework of the programme for the promotion of joint industrial research and development (IGF) on the basis of a resolution of the German Bundestag.