Читать книгу Biodiesel Production - Группа авторов - Страница 33

Purification to remove water, suspended solids, and FFAs is needed for optimal biodiesel synthesis from WCO. The glycerides in the oil are vulnerable to hydrolysis at elevated temperatures, which break these molecules into FFAs and glycerol [2]. Hence, the most common process of water removal is through drying in a hot air oven at 100 °C. During frying, polymerized oil and food residue are generated, which need filtration for removal. The repeated heating of the oil also results in breakdown of glycerides into FFAs, which can be esterified using acids.

The residual FFA in the product, which also affects its total acid number (TAN) must also be low to reduce its corrosiveness [15]. In order to determine TAN, m quantity of oil is dissolved in 2‐propanol along with phenolphthalein. Titration against KOH solution of N normality gives titer value t shown in Eqs. (2.1) and (2.2), where 56.1 = molar weight of KOH, 28.2 weight for 0.1 M oleic acid.

(2.1)

(2.2)

The oil is also tested for calorific value using a bomb calorimeter, which determines the energy content of a sample per mole. The kinematic viscosity of the sample is also measured using a standard viscometer (capillary glass, Saybolt, or Redwood), which gives us an idea about the flow properties of the oil [16].