An oil purifier is a device designed to remove harmful impurities (solid particles, water and gases) from oil.
Oil purifier: what was it like before?
At first large sedimentation tanks were used as oil purifiers. They stored contaminated oil for a period of time. Large impurities in oil under the influence of gravity gradually settled on the bottom of sedimentation tank. The top layer of oil was collected into another container. This method has a disadvantage, which is its duration and separation of only large particles.
Another oil purifier is a centrifuge. The principle of its operation is based on the effect of centrifugal forces. They remove only those particles whose specific gravity exceeds the specific gravity of oil; they also removed water in emulsion state. Centrifugation is powerless against dissolved gases and dissolved moisture, and other, more advanced methods of purification are used following it.
Filtration is another well known method for removing mechanical impurities and a portion of water from oil. Large volumes of matter are removed with so-called filter presses. They create pressure with the help of plates that push oil through filter media, which can be fabric or paper. There are also small stationary filters which are installed in different places in the oil system. The necessary oil flow in this case is created by oil pumps.
It is clear that it is practically impossible to achieve complete oil purification by only one method. Therefore, in practice, a combination of different approaches of oil purification is used in one equipment.
Oil adsorption purification system
The practice shows that purifying oil using adsorption removes products of aging and acid components. Adsorption purification passes the oil through a special adsorbent, which usually fills the cartridge.
There are continuous and periodic adsorption purifications. In the first case, an adsorption purifier is installed next to a transformer, forcing the circulation of the insulating liquid through an oil-water cooler. The oil flow is constant all the time. Continuous purification of oil on an energised transformer allows you to remove most of the oxidation products and slow down the aging process.
But in some situations a continuous purification does not provide the necessary oil parameters and the oil must be changed or processed with the help of special plants. Such situations are: replacement of the adsorbent, mechanical incidents, technical problems, etc. A periodic purification is achieved by the mobile and stationary plants, which use percolation treatment, and pump the transformer oil through a bed of fixed adsorbent.
Types of adsorbents used in oil purification
One of the adsorbents used for oil purification is silica gel, a granular substance that is a form of silicon dioxide. Its practical application in oil purification is based on its porous structure and a different pore size (can vary from 0.1 to 1 nm).
Zeolite is another adsorbent, which has found application in the energy industry. It has a crystalline structure and the same pore size which makes it a stronger adsorbent than silica gel. But zeolite can adsorb only strictly defined molecules. According to this zeolite is much more effective in drying the transformer oil than silica gel, because of its large adsorption capacity: the channels and cavities occupy almost half of the total volume of zeolite crystals.
A special place in oil purification is occupied by natural adsorbents, which are mined as minerals, for example, bauxites, opoka-clays, diatomites and bleaching clays.
To achieve maximum adsorption capacity of an adsorbent it is dried, to partially remove water. Complete dehydration is not recommended, since it significantly decreases the adsorption capacity and even destroys it. For each individual adsorbent, the optimum moisture index is determined only through practice.
Increasing the absorption capacity of natural adsorbents is done through chemical activation, for example, treatment with gaseous ammonia for 10-15 minutes. Another way is acid activation. The sorbent is heated for a long time and mixed with 20% sulfuric acid. It increases the pore size and a partially convert silicon dioxide from one form (crystalline) to another (colloidal).
Modern oil purifiers from GlobeCore
Oil purifiers produced by GlobeCore are an excellent example of modern equipment for cleaning contaminated oil. They combine the most effective methods to obtain the best results: oil treatment with high temperature under vacuum, multistage filtration and adsorption purification. GlobeCore uses Fuller’s earth adsorbent for cleaning transformer oil that is reactivated after saturation directly in the plant, and the process of oil treeatment is not interrupted.
Oil purifiers are available in various stationary and mobile designs, and are equipped with all necessary sensors for monitoring and controlling the process. The oil can be processed automatically just by pressing the “Start / Stop” button. Oil purification design is adapted for transportation by land, sea and air.
Other advantages of GlobeCore equipment are:
- safe, easily adjustable and easy-to-maintain heating tapes;
- easy to replace filter cartridges (filtration fineness 25, 5 and 1 μm);
- efficient coagulator-evaporator in a vacuum column;
- prevention of foam in oil;
- protection from oil leaks;
- remote control of equipment using mobile system