A Simple Standardization Method for the Biodiesel Cold Soak Filtration Apparatus

Abstract

Commercially available refined vegetable oils were investigated as calibration standards for the filtration device and protocol specified by ASTM D7501 for conducting the biodiesel cold soak filtration test. Filtration time was determined to be a function of the amount of vacuum applied during filtration, with an 8 % change in the filtration time of soybean oil occurring across the vacuum range specified by ASTM D7501. At a constant vacuum of 57 cm Hg the mean filtration time of 150 mL of soybean oil was independent of operator, device, and oil lot number. Mean filtration time was also largely independent of brand: the average of the mean filtration times of replicate samples of seven brands of soybean oil was 396 s with a minimum significant difference (MSD) of 28 s, and the filtration times of seven of eight brands of soybean oil tested fell within this MSD. Refined edible-grade corn, canola, peanut, safflower and sunflower oils gave reliable filtration times and would be suitable standards. Each oil exhibited a characteristic filtration time, all greater than that for soy oil. Filtration times were an approximately linear function of kinematic viscosities, as predicted by Darcy’s Law. Edible vegetable oils can serve as reliable, affordable, consistent and generally available materials for confirming the operability of the filtration device used in the biodiesel cold soak filtration test.