Oils cannot by just dumped into the environment, being a hazard for the environment and health. Disposal of oil is a costly process, so the ideal solution is to restore the oil and its future reuse. The following is a summary of the existing oil restoration methods.
Physical methods of oil reclamation allow to remove solid particles and droplets of water from the oil. Tar and coke can be partially removed.
The idea of the physical methods is self-explanatoty: the oil is subjected to various fields and filtered, washed, vacuumized and distilled (to remove volatile fractions).
One of the popular methods of oil reclamation is settling. Its attractiveness is due to its simplicity: solid particles settle naturally. Collecting the contaminant is quite simple. However, the disadvantages of the method (process duration and removal of only the largest particles) limit its use as an independent process. Settling is most often used as a preliminary stage before filtering or centrifuging.
Filtration allows to remove particulate matter and tar. It is dony by installing special porous or mesh filters into the system.
The most efficient way to remove particulate matter and water is centrifuging. Used oil fractions are separated in the centrifuges under the influence of centrifugal force. This approach also helps to restore the oil to the following parameters:
- removal of solid particles to 0.005% by weight
- removal of water down up 0.6% by weight.
Physical and chemical methods of oil reclamation – these are coagulation, adsorption and selective purification. Ion-exchange purification is a case of adsorption purification.
Coagulation – is a process of forced enlargement of colloid particles in the oil. It starts by adding coagulants to the oil. The efficiency of the process is defined by the amount of the coagulant, duration of contact with the oil, intensity of agitation, temperature etc.
Adsorption purification utilizes the ability of bleaching earths, natural zeolite, silica gel, alumina silicates etc to capture contaminants. These substances are cold adsorbents.
Ion-exchange is based on the ability of ion-exchange resins to capture contaminants, however, not all, but only those that can dissociate into ions in solved state. This method allows to restore the oil by removing acidic contaminants.
Selective purification is described in more detail here: selective oil reclamation.
Chemical methods are based on the ability of contaminants to reactor with special reagents. The result of the reaction is easy to remove from the product.