Globecore GmbH, a German company, manufactures oil purifier which extends power transformer service life by 20 years.
Globecore protects and saves millions of dollars of investments in power transformers. This is achieved by transformer oil purification, which can be performed on site, with the transformer energized. Old oil is reused. Transformer oil is used in power and instrument transformers, as well as oil-filled switchgear. The oil insulates energized parts of the equipment, dissipates heat and extinguishes the arc in switches.
Transformer oil is used in power and instrument transformers, as well as oil-filled switchgear. The oil insulates energized parts of the equipment, dissipates heat and extinguishes arcs in switches.
What are the hazards of transformer oil contamination?
The transformer lives as long as its insulation system. Transformer gradually accumulates oxidation products, contaminants and other impurities over time when used. Oxygen and water in the insulating fluid provokes oxidation even under ideal operating conditions. Particles originating from the construction materials of the transformer are also a problem.
The process of oxidation results in formation of acids, which act on carbon and metals, forming aldehydes, alcohols and soap metals. These substances deposit on solid insulation. Contaminants increase oil viscosity, hampering circulation and cooling.
Therefore, aging of transformer oil is a consequence of combined effects of high temperature, oxygen, and electric field in the presence of the transformer construction materials. Important operational parameters of the insulating fluid (acidity, dissipation factor and dielectric strength) are very sensitive to its aging. The higher the intensity of the process, the sooner they reach critical levels, and the oil becomes impossible to use. Using such oil is also dangerous to the transformer: the risk of failures and power outages increases significantly.
What to do with used transformer oil?
Accumulation of waste transformer oil is a serious environmental concern. Consider this: over 40% of waterways in the world are contaminated and covered with a film of waste oil. One liter of waste oil makes a million liters of groundwater unusable! Plants and animals die due to massive pollution with oil products. Besides, waste oil contains carcinogenic substances. Dumping of waste oil into the environment is entirely unacceptable. So what is the solution and how to preserve the planet for future generations?
There is a solution: restoration of transformer oil to its initial condition and reusing the oil. Beside the pronounced environmental benefits, this solution allows to save on purchasing new and disposing of used oil, as well as to extend transformer lifetime by 20 years or more. At this time, the cost of one power transformer reaches, on average, hundreds of thousand US dollars. The number can easily reach into the millions, if the costs of disassembling the oil unit, transporting and installing a new transformer are factored in.
Transformer Oil Filtration Unit Globecore CMM-12R at electricity substation.
Methods of transformer oil purification
Let us consider several techniques used in filtration of used transformer oil.
Centrifuges. These devices are large drums in sealed cases. The drum consists of a number of conical plates with orifices. Centrifuges are used for removal of moisture and solid particles. At one time centrifuges were widely used in oil processing facilities despite their limitations, such as low capacity, complex design, intensive mixing of the processed oil with air and large footprint. With time, compact mobile units for oil treatment were developed, and the number of centrifuges operated is now on decline.
Electric purification. Electric purification is based on the uneven influence of the electromagnetic field on contaminants in transformer oil, which causes the impurities to settle on electrodes. The biggest limitation of this method is the complexity of cleaning the deposits from the electrodes. Also, electric purification cannot remove water. Due to these reasons, this approach has not been widely implemented
Adsorption. This technique involves percolation of oil through a layer of adsorbent (silica gel in most cases), loaded into a vertical cylinder. Silica gel is produced by a series of chemical reactions, making the material rather expensive. Besides, there is a problem of silica gel disposal, since oil-contaminated materials must not be released into the environment.
The alternative is purification of transformer oil with Fuller’s earth, a natural adsorbent. Due to its porous structure, this material has good adsorptive qualities and can be used both for continuous regeneration of transformer oil from dehydrating breather filters, and also for restoration of oil drained from a transformer.
Generally, Fuller’s earth must somehow be disposed of, just like silica gel. However, GlobeCore process allows to reactivate and reuse the sorbent for transformer oil purification many times over.
Transformer Oil Degassing Cart
Thermovacuum dehydration and high vacuum degassing. The GlobeCore process using heat and high vacuum ensures the best parameters of transformer oil. Operation of these units is environmentally safe and does not involve special disposal or storage.
GlobeCore environmental solutions
For many years, GlobeCore has been developing and implementing technologies for restoration of used transformer oil.
The company has successful experience in servicing power transformers of land based and offshore wind farms. We offer a range of units specifically tailored for these purposes.
The UVM type units degas oil and remove particulate matter by a combination of heat, vacuum and filtration. This unit reduces moisture content to 5 ppm and gas content to 0.1% or less and increases dielectric strength to 70 kV.
The CMM-R oil purification plants extend transformer lifetime by restoring the dielectric strength and chemical composition of transformer oil. This equipment allows to maintenance oil directly in an energized transformer. Connecting a CMM-R to an operating transformer allows to remove sludge from the windings and extract it from the oil by the sorbent. These units are loaded with Fuller’s earth.
Adsorbent Fuller’s Earth for Industrial Oil Purifier
The GlobeCore oil purification process has the capability of continuous processing of transformer oil, saving on new oil and disposal of saturated sorbents. Fuller’s earth can be reactivated up to 300 times, the equivalent of 1.5 – 2 years of operation or purification of 1000 tons of oil.
Zeolite drying cabinet GlobeCore ZSC-15
GlobeCore also cares about environmental safety of other machines which use adsorbents. The SSZ-15 zeolite drying cabinet can pre-dry zeolite to improve adsorption and the quality of oil dehydration. The CMM-4RP, one of GlobeCore latest developments, allows reactivation of saturated sorbents used in transformer oil filtration systems. The technology can reactivate the same sorbent at least 10 times. The reactivated sorbents contain no residual oil and, if necessary, can be disposed of a regular household waste without harm to the environment.
GlobeCore CMM-4-RP unit restores waste absorbent
Therefore, GlobeCore transformer oil filtration technologies allow to:
save on purchasing new and disposing of used oil;
significantly lower industrial load on the environment;
extend transformer life by at least 20 years.
In conclusion, we would like to show some numbers to emphasize the economic feasibility of used transformer oil restoration:
average market price of restoring one liter of transformer oil is $0.7-0.8;
average price of one liter of new transformer oil is $1.5-2.
Globecore Oil Purifier CMM-12R
GlobeCore is a manufacturing company researching, developing and producing various oil and fluid processing systems for use in several different industries worldwide and is the developer of the Power Transformer Service Life Extension Program and the GlobeCore Oil Filtration Process for servicing oil filled electric power transformers.
Power transformers are the most expensive part of electric networks equipment. Perhaps this is why a large amount of such equipment has already exceeded its estimated service life. Not every electric power company can afford spending lots of money on transformer replacement. Therefore, the task of improving reliability of the existing fleet of power transformers comes to the fore.
Analysis of causes of power transformer (35-110 kV) failures shows that most of the damage is caused by moisture, contamination of transformer oil and solid insulation with oxidation products, as well as a variety of mechanical impurities. It is solid insulation that is the basic determinant of real service life of power transformers. In turn, its condition is determined by the quality of transformer oil and the processes occurring in it.
Representatives of energy sector share the opinion that timely assessment of the quality of insulating oil and implementation of activities aimed at removing aging products from oil make it possible to improve the reliability of power transformers.
Aging of insulating oil is a result of exposure to high temperatures, as well as the joint effect of atmospheric oxygen and electric field on transformer construction materials.
In general, the oxidation process can be divided into four periods.
At the initial stage there are no visible changes of oil quality. This period is called the induction stage. Its duration is not a fixed value and is highly dependent on the characteristics of chemical composition and application.
The second period (autocatalytic) is characterized by self-acceleration of reactions which is caused by disintegration of the formed hydroperoxides into radicals.
Next comes the constant speed of the process in which the rate of appearance and disappearance of free radicals is equal. This is due to the products of phenolic oxidation, which can slow down the process.
The final period is called the period of self-stifling. It is preceded by a large concentration of phenolic oxidation products in the oil. This stage is characterized by the fact that the oxidation kinetic curve is almost parallel to the abscissa.
Such parameters of transformer oil as its acid value, dielectric loss tangent, water-soluble acids and alkali content, antioxidant additives content are most commonly used as indicators of the processes. They are most sensitive at different stages of aging of insulating oil.
To ensure the reliability of power transformers at least two conditions need to be performed. Firstly, using only high quality oil. Secondly, ensuring the preservation of its performance properties throughout its service life. The latter problem is solved by the use of oil filtration, oil purification and oil reclaiming techniques.
GlobeCore company is one of the leading manufacturers and suppliers of equipment for complex processing of transformer oil: filtration, purification, drying, degassing and reclaiming. The use of a combination of classical technologies and innovative solutions, developed by GlobeCoreengineering department, allows to completely restore the operating parameters of transformer oil to standardized values. The benefits of this approach are obvious: extension of insulating oil service life, reduction of the amount of oil requiring disposal, saving on storage space for waste oil, and, finally, improving the reliability of power transformers.
GlobeCore plants are distinguished by their environmental friendliness and energy efficiency. Thanks to their mobile design, transformer oil treatment can be carried out even in remote places. Oil processing is also possible without draining it from the transformer under voltage.
Transformer oil aging is a process of profound changes accompanied by performance degradation, loss of dielectric strength and accumulated sediment. These processes obstruct heat transfer from the hot parts and speed up the aging of cellulose insulation.
Increase of temperature, contact with atmospheric oxygen, exposure to electric field and presence of mechanical impurities influence aging of insulating oil. Chemical reactions of hydrocarbons and sulfur contribute to it too.
Transformer oils aging have several stages. First there is an inductive stage, with no noticeable changes occurring in transformer oil. The duration of induction period depends on chemical composition of the oil-product and can vary. At the end of this phase low-molecular acids and phenols are formed in oil. Acidic compounds leads to formation of deep oxidation products like insoluble sludge.
But even in the oxidized transformer oil not all hydrocarbons manage to react with oxygen. Such oil needs to be purified before further use.
Today various methods (both separately and combined) are used for transformer oils purification. They demonstrate different levels of effectiveness which depends on initial degree of contamination, the type of oil, etc.
Thermal vacuum purification is one of the most cost efficient and safe methods of transformer oil filtration. The combined effect of high temperature and vacuum remove water and dissolved gases from dielectric fluid.
GlobeCore CMM-C oil recycling plants remove mechanical impurities. They can be used for refilling high-voltage equipment.
This equipment proved itself in more than 70 countries worldwide and is successfully used for installation, repair and operation of power transformers, high voltage switches and other oil-filled equipment.
GlobeCore thermal vacuum purification plants are easy to use, environmentally friendly and cost effective. Quality filtration of transformer oils extends its service life and protects equipment from failures and emergencies.
During operation dielectric oil loses its insulating characteristics, it ages. It is caused by dirt, moisture, air, high temperature, sunlight, presence of oil-soluble metal salts acting as oxidation process catalysts also stimulating oxidation.
Viscosity is one of the most important features of dielectric oil. It decreases when temperature goes up and increases when it the temperature drops. If viscosity is too high, it leads to deterioration of the cooling system of mechanisms.
In the presence of electric field the quantity of moisture in oil is significantly higher than without electric field. Particles of water and contaminants localize along field lines of the electric field. This dramatically reduces electric strength of oil.
Centrifugation and filtration are used for oil purification from water and mechanical impurities. They are more effective – combined. And more often they are used for treatment of dielectric oil in 110 kV voltage transformers. Higher quality oil is used for 220 kV voltage transformers. This requirement relates to gas content primarily, demanding oil drying, filtration and degassing processes.
GlobeCore is one of the leading world manufacturers of purification equipment for dielectric, turbine, industrial and other types of oils. GlobeCore mobile oil stations combine both classical and innovative approaches purifying oils containing water and gases, and mechanical impurities. After being processed, the oil conforms to the high standard and can be used for its intended purpose.
GlobeCore successfully provides equipment for more than 70 countries around the world; being easy to operate, environmentally friendly and inexpensive.
Each of the transformer oil purification methods has its advantages and disadvantages. Best results are achieved when using the combination of classic and innovative GlobeCore approaches.
All transformer oil purification methods can be divided into chemical, physical and physicochemical.
Chemical purification methods include acid and alkaline purification, restoring of oil with metal hydroxides. They remove asphaltenic compounds, resins, acid, compounds, some heteroorganic compounds and water from oil.
Transformer Oil Purification Methods
Acid purification processes oil with concentrated sulfuric acid. This method is based on different interactions of sulfuric acid with hydrocarbons and impurities. Normal temperature does not give a reaction. When the temperature is increased, there is only a partial dissolution. Therefore, during the purification, the oil products must be heated to 40-50 °C. It decreases oil viscosity and improves its mixing with sulfuric acid, which reacts with unsaturated hydrocarbons most intensively
The effectiveness of such treatment depends on the amount and concentration of acid, the time of its contact with oil and the temperature and the process.
In practice, 96% of sulfuric acid is used. Its expenditure is on average 3-5% of the oil mass, and the time of mixing is 25-30 minutes.
During alkaline purification oil is treated with sodium hydroxide, sodium carbonate and trisodium phosphate. Alkali can affect organic, naphthenic and carboxylic acids. As a result of this reaction water-soluble sodium salts (soaps) are formed. They are removed along with the water alkali solution after sedimentation.
Metal hydride regeneration involves oil treatment of oil with calcium, lithium and aluminum compounds. It removes not only water, but also carboxylic acids. The disadvantage of this method is a high cost of reagents, and necessity to clean the oil from solids and neutralizing gaseous substances that escape during the reaction.
Physico-chemical method is based on the use of special substances – coagulants, ion-exchange resins or adsorbents.
Coagulation is coarsening and precipitation of asphalt-resinous substances that are contained in oil in fine particles. Organic and inorganic electrolytes, surfactants, non-electrolytes, colloidal structures in surfactant solutions and hydrophilic macromolecule compounds may act as coagulants.
Adsorption – is another method of oil purification, based on the properties of certain substances (adsorbents) to retain contaminants on the outer surface of the granules and the inner surface of the capillaries. Both natural (bleaching clay) and synthetic (silica gel, alumina, zeolites) substances may perform the function of adsorbents.
The ion exchange purification precipitates into sediment acids, metal salts of calcium, aluminium and magnesium but retains additives.
The main distinguishing feature of physical methods is removing mechanical impurities, fuel, water, tarry asphalt-like and coke-like substances.
Most commonly used in practice is filtration and use of force fields.
Gravitational cleaning is considered the simplest approach, where suspended solid contaminants and water microdroplets are precipitated by gravity. The deposition rate of the particles depends on the height of the oil column, the size of the impurities as well as on the density and viscosity ratio of the deposited substances and the oil. To increase deposition rate – the oil temperature is increased. The highest temperature is 90 °C. If oil temperature goes above this mark, oil begins to boil, which is unacceptable.
Centrifugal force field is used to increase the efficiency of oil purification from mechanical particles. But only if density of particles exceeds the density of oil.
Magnetic field is used to remove solid ferromagnetic particles from transformer oil. It is created by means of either permanent electric current or electromagnets. Apart from particles with magnetic properties the magnets can also draw some other contaminants. This effect is achieved by electrification of non-magnetic bodies.
Vibration cleaning removes solids, with the amplitude of vibration causing coagulation. Electrostatic cleaning can also be applied as one of purification methods for transformer oil. In this conditions – contaminants, moving together with liquid, rub against surroundings under the influence of friction forces and receive a charge of a certain sign. In the electric field the contaminants that received a charge are drawn to the oppositely charged electrodes.
Filtration is separation of suspended solids from oil by means of porous filter material. This method is quite common due to the relative technical simplicity and reliability.
Integration of different methods is necessary in order to restore properties (for oil purification) of transformer oil. The accuracy of its combination determines the final result.
GlobeCore offers versatile oil purification equipment. The operation is based on both classical and innovative purification methods. GlobeCore uses authentic oil purification technologies making their plants most effective. GlobeCore technology is three in one: environmentally friendly, profitable and saves fuel and energy resources!
The service life of an electric power transformer is defined by four main factors:
aging caused by heat;
electrical insulation wear;
mechanical wear; and
Heat aging is the process during which the cellulose insulation can become critically damaged and the mechanical performance of the insulating paper can become degraded to the point of failure. When discussing electric power transformers, the terms “transformer service life” and “cellulose insulation service life” are often interchangeable.
Electrical insulation wear is the process in which a critical reduction of the dielectric strength of the liquid insulation, caused by moisture and contamination by aging products, can occur.
Mechanical wear is the disruption and degradation of the core windings due to the cumulative effects of short circuit current, vibration, power surges and other harmful environmental conditions
Since most transformers in service today are relatively old (most were commissioned towards the end of the previous century), and buying new electrical equipment is very costly, maximizing your current equipment’s service life and capability is essential. Extension of the service life of your transformers is especially important for the power transformers used in nuclear power plants.
Dielectric insultaing oil, also known as transformer oil, performs the most important function of insulating the current-conducting parts of the transformer, and dissipating the heat from the core and the windings. The condition of the transformer’s insulating oil in many ways defines and determines the reliability of the transformer itself.
GlobeCore is one of the world’s leading manufacturers and supplier of transformer oil purification equipment. The GlobeCore process of oil purificaton and regeneration offers the capability to restore the performance of transformer oil to the specifications of the oil when it was new. The GlobeCore process will extend the service life of both the oil and the equipment making the process the most cost effective in the industry.
Processing transformer oil at nuclear power plants has its own specific requiements. Oil processing equipment is often required to be operated in what are known “explosion hazard” environments. Fires and explosions in nuclear power plants may be caused by neglecting the correct procedures, carelessness, and operator errors.
Nuclear power plants can be vulnerable to explosion and fire hazards due to the following factors:
use of flammable oils in turbine systems, hydrogen in turbine colling systems;
the use of diesel fuel and fuel oil for diesel power generation;
short circuit of power cables;
oil coming into contact with hot parts;
use of flammable materials in electrical equipment; and
human error during repairs and system checks.
In anticipating the risks posed in modern poer plants, GlobeCore now offers special explosion proof equipment designs for its most popular oil processing equipment. The explosion proof units feature multi-tier explosion protection that can guarantee safety and reliability while performing a high quality level of oil purification the modern nuclear power plant.
A method removes corrosive sulfur compounds from transformer oil. By adding a mixture of rare earths containing aluminum oxide and aluminum silicate to the transformer oil, and enriching the same with an aqueous solution of soluble metal salts, the corrosive sulfur compounds in the transformer oil are neutralized with defined heating and cooling phases. Advantageously, no additional chemical components, such as passivators, are added to the transformer oil. When using a tank for receiving the mixture of the rare earths containing aluminum oxide and aluminum silicate, the reaction can run in the tank. Any aging products that may be present, and the bonded corrosive sulfur compounds are effectively retained within the tank by a filter system, and can be disposed of with the tank.
The invention relates to a method for removing corrosive sulfur compounds from a transformer oil.
Transformers frequently use as insulation and cooling media transformer oils which, due to their long-term chemical characteristics, have for many years been used for operating transformers. One problem associated with using transformer oils is, however, the presence of natural or added sulfur compounds which contribute to the oxidation stability of the oil itself, in particular in the case of uninhibited transformer oils. Conductive copper sulfide compounds are consequently formed which are preferentially deposited in the paper insulation and impair its insulating properties. This phenomenon is promoted in particular at elevated operating and ambient temperatures.
When unlacquered, paper-insulated copper conductors are used within a transformer and under conditions of limited oxygen content, for example when a transformer is operated with exclusion of air, transformer oils comprising corrosive sulfur-containing constituents form layers of copper sulfate on the paper insulation. Starting from the copper conductor, copper sulfide layers form within the paper layers surrounding the copper conductor. As a result, the insulation properties of the paper insulation are sometimes durably impaired, such that partial discharges and voltage flashovers may occur between the live copper conductors due to the reduced insulation properties of the paper insulation.
These corrosive sulfur compounds, in particular mercaptans and disulfides, form above all in transformers, chokes or passages under specific operating and temperature conditions and reduce the insulation properties of the paper insulation to a considerable extent; sometimes down to just 20 percent of the original electric strength of the paper insulation.
The attempt has accordingly been made in the prior art to suppress the reaction of the corrosive sulfur compounds within the transformer oils with the copper conductor and simultaneously to improve oxidation resistance by “passivating” the transformer oils, in particular by means of metal passivators comprising benzotriazole-based compounds. A problem in this case is in particular that the metal passivator may be consumed during the ongoing operation of the transformer and the quantity of passivator available must thus be permanently monitored. Moreover, the extent to which long-term passivation modifies the properties of the transformer oils is as yet unknown.
WO 2005/117031 A2, for example, accordingly describes a method and a device for adding a passivator to a conductor. The above-stated patent application proposes winding the passivator directly around the conductor and then sheathing it with a further layer of an electrical insulator and so providing overall electrical insulation for the conductor with the passivator layer.
WO 2007/096709 A2 moreover describes a method for permanently removing corrosive components from a transformer oil. The above-stated patent application proposes removing the transformer oil from a transformer tank and, after heating and addition of an acid-containing liquid, bringing it into contact by means of a sulfide free-radical scavenger and then filtering it. After filtration, the transformer oil purified in this manner is reintroduced into the transformer tank.
The same applies to WO 2007/144696 A2 as a method for deactivating corrosive sulfur in transformer oils. According to the invention, the above-stated patent application proposes adding a sulfide-forming chemical component to the transformer oil comprising corrosive sulfur compounds, such that said chemical component reacts with the sulfur compound and the corrosive sulfur compounds are thus removed from the transformer oil.
DE 10 2005 006 271 A1 moreover describes a method for purifying transformer oil, the transformer oil initially being subjected to a pretreatment by filtration, before it is passed through a packing of an inert inorganic support coated with a reactive metal. The transformer oil is then filtered through a bleaching earth bed and then returned to the transformer.
The object of the present invention is accordingly to avoid the disadvantages in the prior art and to provide a method for removing corrosive sulfur compounds from a transformer oil which easy to handle and ensures virtually complete removal of corrosive sulfur compounds from the transformer oil.
Said object is achieved by the features of the method as claimed in claim 1. According to the invention, a method is proposed for removing corrosive sulfur compounds from a transformer oil, in which, with addition of a mixture of rare earths containing aluminum oxide/aluminum silicate to the transformer oil, said transformer oil enriched in this manner is heated to up to 300 degrees Celsius and then, with enrichment with an aqueous solution of soluble metal salts, is cooled.
The transformer oil enriched with the rare earth mixture containing aluminum oxide/aluminum silicate is then once more heated to up to 200 degrees Celsius for at least two hours and then cooled to room temperature.
Heating of the mixture of rare earths containing aluminum oxide/aluminum silicate activates the adsorption centers of the matrix by removing water fractions. The heavy metal salts present in the mixture of the rare earths containing aluminum oxide/aluminum silicate are thereafter dispersed in a little water and the mixture is slowly heated. This gives rise to heavy metal oxides which are insoluble and firmly bound to the fuller’s earth matrix of the mixture of rare earths containing aluminum oxide/aluminum silicate.
In this manner, the adsorbent is prepared. The solution presented here is based on removing the reactive corrosive sulfur compounds present in the transformer oil by using a mixture of inorganic adsorbents with a wide range of applications. It mainly comprises a mixture of rare earths containing aluminum oxide/aluminum silicate and are optionally enriched with silver, copper, zinc and/or iron in metallic or oxide form. In particular, the metal oxides formed by means of the rare earth mixture containing aluminum oxide/aluminum silicate bind the corrosive sulfur compounds and may be collected at a suitable point and removed from the transformer oil, optionally together with simultaneous removal of oil ageing products.
The advantage of this method is that no additional foreign substances, such as for example passivators, are added to the transformer oil. Ageing products and corrosive sulfur compounds are simultaneously eliminated from the transformer oil. Oxidation capacity is consequently increased and the fraction of corrosive sulfur compounds within the transformer oil is greatly reduced, so durably increasing the service life of the transformer.
It is considered advantageous according to the present method for the ratio between the fraction comprising aluminum oxide and the fraction of aluminum silicate in the rare earth mixture containing aluminum oxide/aluminum silicate to be in a ratio of 20:80 to 80:20, preferably of 50:50. The catalytic action of the rare earth mixture containing aluminum oxide/aluminum silicate is best ensured within the preferred ratio range of the fractions.
A bulk density of 50 to 80 g/l is advantageously used in order to provide the greatest possible surface area of the rare earth mixture containing aluminum oxide/aluminum silicate. In this bulk density range, an in particular granular rare earth mixture containing aluminum oxide/aluminum silicate has an effective surface area for binding the corrosive sulfur compounds present in the transformer oil. The aqueous solution advantageously has a solution fraction of up to 40% of in particular soluble metal salts. Adding copper and silver salts in particular leads to improved binding of the corrosive sulfur compounds onto the metal salts present in the aqueous solution. This precisely prevents the corrosive sulfur compounds present in the transformer oil from reacting chemically with the copper conductor. The pH value of the rare earth mixture containing aluminum oxide/aluminum silicate is advantageously 6.5 to 9.0. The metal oxides formed react with the corrosive sulfur compounds at the highest possible rate of reaction in the above-stated pH range.
An advantageous development of the method provides that the ratio of the rare earth mixture containing aluminum oxide/aluminum silicate to transformer oil, relative to their respective weights, is in a ratio of 0.01:100 to 40:100, preferably of 10:100. The highest possible rate of reaction is ensured in particular at the preferred weight ratio of 10:100 of rare earth mixture containing aluminum oxide/aluminum silicate to transformer oil due to their respective concentrations. Advantageously, the rare earth metals of group 3 of the periodic table of elements including the lanthanoids are a constituent of the rare earth mixture containing aluminum oxide/aluminum silicate. In an advantageous development of the method, silver, copper, zinc and/or iron are admixed with the rare earth mixture containing aluminum oxide/aluminum silicate. Moreover, silver nitrate to form silver oxides and/or copper salts to form copper oxides and/or iron oxides is/are admixed with the rare earth mixture containing aluminum oxide/aluminum silicate. The metal oxides present in this manner within the rare earth mixture containing aluminum oxide/aluminum silicate are highly reactive and combine with the corrosive sulfur compounds within the transformer oils and neutralize the corrosive sulfur compounds.
An advantageous development of the method provides that the rare earth mixture containing aluminum oxide/aluminum silicate is arranged in a container, in which the container may be fitted on a transformer housing and the transformer oil is passed into the container and purified, and the sulfides bound in the rare earth mixture containing aluminum oxide/aluminum silicate as reaction products of the corrosive sulfur compounds remain in the container. Thanks to the reaction of the corrosive sulfur compounds of the transformer oils within the container and the accumulation of the bound sulfides in the container, these waste products may be disposed of on removal of the container. At the same time, any further contamination of the transformer oils with the bound sulfides in the container is ruled out, such that corrosive sulfur compounds may virtually completely be removed from the transformer oil by the above-stated method.
In the event of complete consumption of the rare earth mixture containing aluminum oxide/aluminum silicate, the container is advantageously removed from the transformer housing. In an advantageous development of the method, the container comprises an indication of the reactive rare earth mixture containing aluminum oxide/aluminum silicate which is present. In the context of servicing, this indication may be used to establish whether sufficient reactive rare earth mixture fractions containing aluminum oxide/aluminum silicate are present and proper performance of the method is ensured.
A filter system is advantageously introduced within the container, the filter system comprising the rare earth mixture containing aluminum oxide/aluminum silicate, and the transformer oil is introduced into the filter system. By means of the filter system, the bound sulfides and the transformer oil end-of-life products may in particular more readily be retained within the filter system and so collected within the container.
An advantageous development of the method provides that the container may be connected with a purifying device, in which the purifying device may be connected with the transformer housing and the transformer oil may be transferred out of the transformer housing for purification in the purifying device and thus the corrosive sulfur compounds are removed in the container outside the transformer housing.
Further advantageous developments are revealed by the subclaims.
A rare earth mixture containing aluminum oxide/aluminum silicate has a bulk density of 600 g/l with a ratio of aluminum oxide to aluminum silicate of 50:50. The pH value is 7.0. One kilogram of the rare earth mixture containing aluminum oxide/aluminum silicate is activated at 150° C. and, after cooling, treated in portions with 400 ml of a 20% aqueous solution of soluble salts of silver, copper, zinc or iron. The mixture is homogenized and heated stepwise to 120° C. within five hours. This temperature is maintained for 15 to 20 hours. After cooling, the mixture is kept in a closed vessel. The ratio relating to the weights of the active rare earth mixture containing aluminum oxide/aluminum silicate to treated transformer oil is 0.5:100 to 10:100, depending on the state of ageing and corrosiveness of the transformer oil.
A method for removing corrosive sulfur compounds from transformer oil, which comprises the steps of:
adding a mixture of rare earths containing aluminum oxide/aluminum silicate to the transformer oil;
heating the transformer oil enriched with the rare earth mixture containing the aluminum oxide/aluminum silicate to up to 300 degrees Celsius;
cooling the transformer oil enriched with the rare earth mixture containing the aluminum oxide/aluminum silicate;
enriching the transformer oil with an aqueous solution of soluble metal salts; and
heating the transformer oil to up to 200 degrees Celsius for at least two hours and subsequent cooling to room temperature.
The method according to claim 16, which further comprises setting a ratio between a fraction containing the aluminum oxide and a fraction of the aluminum silicate in the rare earth mixture containing the aluminum oxide/aluminum silicate to be in a range of 20:80 to 80:20.
The method according to claim 16, which further comprises setting a bulk density of the mixture of rare earths containing the aluminum oxide/aluminum silicate to be 50 to 800 g/l.
The method according to claim 16, wherein the aqueous solution has a solution fraction of up to 40% of the soluble metal salts.
The method according to claim 16, which further comprises setting a pH value of the mixture of rare earths containing the aluminum oxide/aluminum silicate to be 6.5 to 9.0.
The method according to claim 16, which further comprises setting a ratio of the mixture of rare earths containing the aluminum oxide/aluminum silicate to the transformer oil, relative to their respective weights, to be in a range of 0.01:100 to 40:100.
The method according to claim 16, which further comprises using rare earth metals of group 3 of the periodic table of elements and lanthanoids.
The method according to claim 16, which further comprises admixing at least one of silver, copper, zinc or iron with the mixture of rare earths containing the aluminum oxide/aluminum silicate.
The method according to claim 16, which further comprises admixing at least one of silver nitrate to form silver oxides, copper salts to form copper oxides, zinc oxides or iron oxides with the mixture of rare earths containing the aluminum oxide/aluminum silicate.
The method according to claim 16, which further comprises disposing the mixture of rare earths containing the aluminum oxide/aluminum silicate in a container, and the container is connected with a transformer housing and the transformer oil is passed into the container and purified, and sulfides bound in the mixture of rare earths containing the aluminum oxide/aluminum silicate remain in the container.
The method according to claim 25, which further comprises in an event of a complete consumption of the mixture of rare earths containing the aluminum oxide/aluminum silicate, removing the container from the transformer housing.
The method according to claim 25, wherein the container contains an indication of the reactive mixture of rare earths containing the aluminum oxide/aluminum silicate which is still present.
The method according to claim 25, wherein the container has a heating unit for heating the transformer oil enriched with the mixture of rare earths containing the aluminum oxide/aluminum silicate.
The method according to claim 25, wherein a filter system within the container contains the mixture of rare earths containing the aluminum oxide/aluminum silicate and the transformer oil is introduced into the filter system.
The method according to claim 25, which further comprises connecting the container with a purifying device, the purifying device being connected with the transformer housing and the transformer oil may be transferred out of the transformer housing for purification in the purifying device and thus the corrosive sulfur compounds are removed in the container outside the transformer housing.
The method according to claim 16, which further comprises setting a ratio between a fraction containing the aluminum oxide and a fraction of the aluminum silicate in the mixture of rare earths containing the aluminum oxide/aluminum silicate to be 50:50.
The method according to claim 16, which further comprises setting a ratio of the mixture of rare earth containing the aluminum oxide/aluminum silicate to transformer oil, relative to their respective weights, to be 10:100.
A prosperous oil and gas industry is one of the factors that has contributed to the sustainable development of the world economy. It includes objects where the geophysical research is performed and operational and extension wells are drilled.
In recent years, the extraction of oil and gas has had a potential to grow which requires the exploration and development of new deposits of mineral resources since the old ones have been depleted.
It should be mentioned that drilling operations are considered to be a basis for oil and gas production since about 70% of the world investments in this field will potentially accrue to them.
The table 1 shows the major sectors and its percentage in the oilfield services market.
The percentage of major sectors in the world market for oil services
Name of a sector
Enhanced Oil Recovery
Oilfield casing and tubular goods
Oil and gas equipment
The table shows that one of the major sectors of the oil industry is marine offshore drilling. This is due to the fact that onshore oil and gas deposits are becoming depleted and the development of the sea shelf will render it possible to provide the world economy with hydrocarbon crude for many years.
The first records of offshore drilling date back to 1869 when the first patent for an offshore drilling rig was granted to T. F. Rowland. This invention was designed to perform shallow water drilling operations in approximately 50 feet of water.
The first offshore drilling of any consequence was carried out in the USA as early as 1891. Since then, offshore drilling rigs have evolved from fixed shallow water unit to the mobile units that can simultaneously serve several dozen wells and store thousands of tons of fuel on board.
In general, marine offshore platforms consist of machines for well drilling, oil and gas extraction, worker accommodations, and power supply systems. Besides daily needs, electric power is required for drilling rig drive systems.
The voltage distribution and supply lines are regulated by transformers. An uninterrupted supply of electricity to an offshore drilling platform greatly depends on the operational reliability of the electric power transformers.
Research performed by The International Association of Engineering Insurers (IAEI) has shown that the majority of electric power transformer breakdowns are caused by liquid and solid insulation failures.
Transformer oil is used to insulate conducting parts of the transformer and to transfer heat from the heated parts of the transformer.
During the operational service life of the transformer, the insulating oil has the potential to degrade badly by being exposed to moisture, temperature extremes, and mechanical impurities. All of these factors can cause transformer failures and adversely affect the whole drilling platform.
In some cases, they may lead to the failure of the expensive equipment and/or unscheduled downtimes of the whole drilling platform and will involve considerable cost for the drilling rig operators.
The above mentioned consequences however, may be prevented if the operator performs regularly scheduled transformer oil purification and regeneration in the marine environment.
GlobeCore has developed and is still producing equipment for transformer oil reclamation in the marine environment that has the following characteristics:
(1) compact in size; (2) explosion-proof design; (3) protection from moisture; (4) vibration dampening; and (5) protection from salt-water corrosion issues.
GlobeCore’s Clean Marine Offshore Oil Processing Systems provide vacuumizing of transformers as well as the purification of transformer oils by removing mechanical impurities, water, gasses, and unwanted contaminants.
The following is a list of benefits of the GlobeCore Clean Marine Oil Processing Equipment:
(1) oil is restored to new like condition (the breakdown voltage is increased and the acidity is reduced);
(2) reduced need to buy and transport oil;
(3) oil’s service life is extended and the transformer’s service life is extended; and
(4) no hazardous waste and and risk of damage to the environment.
GlobeCore Clean Marine Oil Processing equipment may be operated in the following modes:
transformer heat up (oil is heated and filtered);
oil degassing (oil is filtered, dried and degassed); and
GlobeCore is the best solution to the problems of transformer oil processing in the marine environment.
Transformer oil is used in electric power transformers, high-voltage bushings and oil circuit breakers to transfer heat from the heated parts of the transformer. Additionally, the oil is used as a liquid insulation to help insulate internal conducting parts of the transformer’s windings and core. Transformer oil protects the solid insulation from moisture by filling all the space inside the transformer’s oil storage tank and serves as a diagnostic tool in determining the condition of the transformer. In switching devices, oil is necessary to quench an unwanted and dangerous arc.
Since oil filled electric devices are usually operated under heavy load conditions, transformer oil is exposed to a wide range of unfavourable factors such as: (1) temperature extremes; (2) atmospheric oxygen; and (3) flooding. All these factors, either separately or together, will lead to the degradation of the performance characteristics of the insulating fluid and the solid insulation.
Transformer oil can degrade quickly based on adverse conditions and consequently will become unable to perform its intended functions. All this may result in serious consequences: (1) accidents; (2) expensive equipment failures; and (3) unplanned outages. Transformer oil samples therefore, should be taken regularly and analyzed to prevent such consequences. The degradation of the rated values of transformer oil requires the oil to be dried, purified, and degassed to remove mechanical impurities, water, gasses and sludge.
One of the most effective methods of transformer oil purification is through the use of adsorbents. They are substances that are able to absorb the products of aging and moisture from insulating fluids. Such natural materials as silica clay, bleaching clays, amorphous coal and activated carbon, silica gels, aluminum oxides and zeolites serve as adsorbents. Natural adsorbents are eco-friendly and they are less expensive to obtain than artificial ones. They have a high specific porosity and a high ability to perform adsorption. Due to these characteristics, natural adsorbents are widely used in the industry.
Silica clay is a natural material with high stability and high porosity. Additionally, it does not swell when wet and is resistant to acids and alkalis. Silica clay includes finely grained amorphous silica (76-88%) and a mixture of clay, sand and glauconite. This rock may be of white, grey or even black color. Microscopic studies have shown that silica clay is formed from opal grains and the remnants of silicon skeletons of organisms, consolidated by siliceous substances.
One of the hypotheses of silica clay origin states that this material resulted from the structural transformations of diatomites and other suchlike materials. Usually, a natural sorbent derives its name from the location of its deposits. The bleaching characteristic of silica clay depends on the silica/alumina ratio: the higher the ratio, the higher the adsorption characteristics.
Silica clay is recommended to be stored only in special dry rooms when humidity is controlled. Prior to shipment, the substance grits are exposed to a thermal activation at between 150ºС and 200ºС with a subsequent sieving of small grains with a size of 3 mm on a special sieve. The latter has 16 holes on 1 cm2 of the surface.
Silica clay used for transformer oil purification should meet the following requirements:
the amount of calcium and magnesium in dry silica clay should be no more than 2.2% and the amount of silic acid should be no less than 32.5%;
the apparent density of dry grits should be no more than 0.65g/cm3;
adsorption activity should be no less than 45%;
the size of the main grit grains should be between 3 and 7 mm and the content of grit grains with a size of 3 mm should not exceed more than 5% of the total volume;
no foreign impurities; and
humidity should not exceed 10%.
GlobeCore is one of the leading manufacturers and suppliers of technological equipment for purification and restoration of dielectric transformer oil and other oils. The operation of GlobeCore equipment is based on separate purification methods as well as by combination. The highest value is placed on the adsorption technologies through the use of bleaching clays, silica gels, and zeolite.
GlobeCore mobile oil processing stations have obtained a wide use and acceptance in more than 80 countries around the world. This is due in part to its innovative technologies that allows for sorbent reactivation rather than disposal of large volumes of hazardous waste. Fully automated equipment can perform operations 24 hours a days without interruption on energized transformers.
GlobeCore ensures high quality purification of transformer oils with no losses of raw material.
A regular processing of insulating fluids on the GlobeCore mobile purification plants extends the service life of the transformer, reduces the financial expenditures for new oil, and eliminates the risks of accidents and equipment downtimes.