Production Process
Preparation- Utmost care must be taken to monitor the amount of water & free fatty acids in the biolipids (Oil or Fat) to be used in the process. If the free fatty acid level or water level is too high it may cause problem with soap formation & the separation of the glycerin by-product downstream.
Catalyst is dissolved in alcohol using a standard agitator. The alcohol/catalyst mix is then charged into a closed reaction vessel & the biolipid (vegetable or animal oil or fat) is added. The system from here on is totally closed to the atmosphere to prevent loss of alcohol. The reaction mix is kept just about the .boiling point of alcohol (around 70° C) to speed up the reaction though some systems recommend the reaction take place at room temperature. Recommended reaction time varies from 1-8 hours. Excess alcohol is normally used to ensure total conversion of the fat or oil to its esters.
The glycerin phase is much more dense than biodiesel phase & the two can be separated by gravity with glycerin simply taking out through the bottom of the settling vessel. In some cases a centrifuge is used to separate the two materials faster.
Once the glycerin & biodiesel phases have been separated, the excess alcohol in each phase is removed with a flash evaporation process or by distillation. In other systems the alcohol is removed and the mixture nutrilized before the glycerin & esters have been separated. In either case the alcohol is recovered using distillation equipments & is reused. Precautions must be taken to ensure no water accumulates in the recovered alcohol stream.
The glycerin by-product contains unused catalyst & soaps that are nutrilized with an acid & sent to storage as crude glycerin (water & alcohol are removed later generally by evaporation to produce a 80-88% pure glycerin).
Once separated from the glycerin the biodiesel is sometimes purified by washing gently
with warm water to remove residual catalyst or soaps, dried, and sent to storage.
