engleski

Determination of biogenic component in liquid fuels by the 14C method and direct LSC measurement

Biogenic materials itself or as blends to fossil fuels are presently often used for energy production and/or transport. One of the methods for determination of the fraction of the biogenic component in any type of fuel is the 14C method, which is based on different content of 14C in biogenic and in fossil component: while the biogenic component reflects the modern atmospheric 14C activity, no 14C is present in fossil fuels. A technique of direct LSC measurement of the 14C content in liquid fuels is simple and fast because it does not require any sample pre-treatment. However, its main disadvantage is caused by different liquid colours that change quenching properties and measurement efficiency. Recently we proposed a new evaluation technique that takes advantage of different quenching properties of various liquids of different colours. By utilizing various modern organic liquids (various brands of domestic oils, benzene, ethylene) we constructed the modern calibration curve that relates their count rates and SQP (standard quench parameter) values. A background calibration curve was constructed by using various 14C-free liquids. All samples were prepared in low-potassium glass vials with the UltimaGold F scintillator (10 mL of a sample and 10 mL of UGF). Measurement was performed by LSC Quantulus 1220 and spectra were evaluated in the window 124 – 570 channels. We suggest that the data evaluation method could be used for determining the biogenic fraction in various types of organic liquids, including liquid fuels of unknown chemical composition. Here we present further studies of the applicability of the proposed method. We have prepared mixtures of fossil fuels and some biogenic liquids in a nominal concentration range of the biogenic component from 0 % to 100 %. Test will be made to check if the proposed method depends on the qualitative composition of the mixture, i.e., on the fossil matrix or the biogenic additive type. The sensitivity and limitations of the method will be discussed.

liquid fuels ; 14C ; biogenic component

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