Wspólnotowy Serwis Informacyjny Badan i Rozwoju - CORDIS

Physical/mechanical tests - particle size distribution and dimension

For an unobstructed biofuel use (i.e. fuel handling, storage, transhipment and energetic conversion) particle size dimensions and their distributions in a bulk have often been identified as a key quality parameter.

The results revealed that the analysis of biofuels particle size is associated with high measuring uncertainties. This is basically due to the fact, that the tested major measuring principles (i.e. horizontal and rotary screening as well as image analysis) produced results that were largely incompatible. Results acquired from the image analysis system showed highest conformity to the reference values (standard samples). For all horizontal and vertical screening machines the median value of the size distribution (according to particle length) was only between one third to half of the reference median value.

This is attributed to the high particle misplacement particularly found in larger fractions. For rotary screening the median particle length is between the results of image analysis and horizontal screening. Based on this, comparable measurements must consistently be made using only one of the three principles, while for the same principle modifications of the equipment type (e.g. different dimensional shaking operations) are usually acceptable.

With regard to influencing factors, for horizontal screening a critical shaking frequency (~ 190 rpm) was identified, while the chosen initial sample volume was found to be less important. For the screening duration a larger effect was observed; a fixed minimum time requirement of about 15min was identified to be meaningful. For rotary screening the influencing factors are mainly the rotation speed and the inclination angle of the rotating drum. Also the feeding rate and the moisture content of the sample play an important role, as reflected by the measured differences in the calculated median particle size. Generally, it should be attend to sample preparation due to the possible inhomogeneous moisture content within the sample. Coupled with this, the fixation of a tolerable moisture range is required if results from different fuels and test methods shall be compatible.

However, high reproducibility is only given, when all relevant measuring variables and the influencing factors are carefully considered and standardised accordingly.

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TFZ - Technologie- und Förderzentrum Nachwachsende Rohstoffe
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