The most common process being the Batch process. Care is taken to monitor the amount of water and free fatty acids in the incoming biolipid. If the free fatty acid level or water level is too high it may cause problems with soap formation and the separation of the glycerin by-product downstream. The Catalyst is then dissolved in the alcohol. This is done by the use of a standard agitator or mixer. The alcohol/catalyst mix is then charged into a closed reaction vessel and the biolipid (vegetable or animal oil or fat) is added. The system from here on is totally closed to the atmosphere to prevent the loss of alcohol. The reaction mix is kept just above the boiling point of the alcohol to speed up the reaction. Under normal conditions the reaction rate will double with every 10 °C increase in reaction temperature. Excess alcohol is normally used to ensure total conversion of the fat or oil to its esters.
The glycerin phase is much denser than biodiesel phase and the two can be gravity separated with the help of a centrifuge. Once the glycerin and biodiesel phases have been separated, the excess alcohol in each phase is removed with a flash evaporation process or by distillation. Care must be taken to ensure no water accumulates in the recovered alcohol stream. 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.
An alternative, catalyst-free method for transesterification uses supercritical methanol at high temperatures and pressures in a continuous process. In the supercritical state, the oil and methanol are in a single phase, and reaction occurs spontaneously and rapidly.
Ultra- and High Shear in-line or batch reactors allow production of biodiesel continuously, semi- continuously, and in batch-mode. This drastically reduces production time and increases production volume. Ultra – Shear, up to three sets of rotor and stator which converts mechanical energy to high tip speed, high shear stress, high shear-frequencies. The reaction takes place in the high-energetic shear zone of the Ultra- and High Shear mixer by reducing the droplet size of the immiscible liquids such as oil or fats and methanol.
In the ultrasonic reactor method, the ultrasonic waves cause the reaction mixture to produce and collapse bubbles constantly. This cavitation provides simultaneously the mixing and heating required to carry out the transesterification process.
The Microwave method is one in which microwave ovens are used to provide the heat needed in the transesterification process. The microwaves provide intense localized heating that may be higher than the recorded temperature of the reaction vessel.
These are basically how the Biodiesel systems work to produce the alternative energy source such as Biodiesel which might prove to be very crucial in the near future.
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