Addition of a steel pre-filter to improve plate filter-press performance in olive oil filtration

Olive oil is a turbid colloidal dispersion. The most common technique used to clear the oil is filtration. Among filter systems, plate filter-presses are used by small companies because the filters are cheap, and the technique does not impair the sensory and chemical traits of the olive oil. However, plate filter-presses have some disadvantages: their operating capacity is low, they require a lot of man power, and filter sheets trap part of the processed oil. It has been argued in the literature that they can retain minor compounds. Furthermore, there is a cost associated with their disposal. The impact of all of these issues could be reduced by the optimization of filtration cycles. Hence, a new processing arrangement was proposed and tested. This consisted of the insertion of a steel pre-filter into the system, which retained part of the suspension. Consequently, the plate filter-press only retained residual solids and water. The plate filter press with the added pre-filter was able to process about 1.8 times the amount of oil normally processed in a batch. Operative capacity was improved and the amount of oil trapped in the sheets was reduced. Furthermore, the number of the filter sheets required was almost halved, which also halves their purchase and disposal costs. A surface fouling mechanism is seen in the traditional filter press configuration, while in the new configuration particle retention is due to depth fouling. This change in the fouling mechanism demonstrates that the addition of a pre-filtration step leads to the more effective use of filter sheets.