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Purification of Glycerin from Biodiesel Manufacturing

Biodiesel producers are challenged by the decision of how to handle the crude glycerin by–product stream from their plant. Should it be simply disposed of as a waste stream? Purified so that it can be sold, as technical or pharmaceutical grade? Burned for energy to help power the plant?

2-stage glycerin purification

If you choose to purify the glycerin, then Artisan has developed a special purification process, utilizing the Rototherm® E evaporator technology, which offers tremendous advantages over other traditional methods.

Artisan’s Glycerin Purification Process uses two stages of continuous vacuum evaporation to first remove the “light-end” contaminants, such as methanol and water, and then evaporate the glycerin away from the heavier contaminants.

The feed enters the Artisan Rototherm® mechanically aided thin film evaporator, where the centrifugal force generated by the spinning rotor maintains a thin film of material on the heated wall, evaporating essentially all the volatile contaminants. The vapors are condensed in a condenser, from which they are sent to recovery or waste treatment. The remaining material discharges from the first stage Rototherm and is pumped to the second stage Rototherm.

The second stage Rototherm operates at a higher temperature and a deeper vacuum, to evaporate the glycerin from the heavy contaminants. Turbulence created by the rotor blades constantly renews the film, aiding in both heat and mass transfer, and enabling nearly complete evaporation of the glycerin, while the heavies discharge and are pumped away for disposal. The glycerin vapor exits the Rototherm and enters the condensing system.

The use of Artisan’s Rototherm E Evaporator allows for very high concentration in one pass, which maximizes product yield and minimizes waste by recovering nearly all the glycerin, leaving behind a relatively small sludge/ash waste stream for disposal. The combination of low absolute pressure (allowing lower operating temperatures) and very low residence time also minimizes product degradation. The rugged Rototherm agitated thin film evaporator is able to handle dirty, fouling, viscous feeds, thick slurries, and pasty materials much better than any other type of evaporator and is easy to clean; this allows our process to operate longer between cleaning cycles.