The essence of chemical methods is introduction of special reagents into the oil. These materials them react with the contaminants in the oil. The result of the chemical reactions is formation of such materials which can then be easily removed from the oil.
Chemical methods include acidic or alkaline purification, hydrogenation, drying and removal of contaminates using oxides, carbides and hydrides of metals.
The following is a more in-depth look into the most used chemical oil purification methods.
Sulfuric acid purification is the most widely used process, judging from the number of plants in the world and the volume of processed oil. The drawback of this process is its inability to remove polycyclic arenes and highly toxic chlorine compounds. It also leaves a lot of acidic sludge, which is difficult to dispose of and poses environmental hazards.
Hydrofining is much better in terms of the environment. This method allows high quality oil production with increased yield. The drawbacks of this method is the requirement for significant amounts of hydrogen.
To purify processed oils from the toxic chlorine substances, tar, oxidation products and additives, metallic sodium is used. The results of this reaction are polymers and salts of sodium with high boiling point, making possible distillation of oil.
In practice, oil regeneration systems usually combine various methods, therefore, oils of various types and different specifications may be regenerated.
It is important to understand that regeneration produces basic oils, which are identical to new oil in terms of quality. Product yield is 80 – 90% depending on the quality of incoming oil. Regeneration of base oil can be performed at least twice. This, however, is only true in case of modern technology process and corresponding equipment.