Recycling and Oil Regeneration

Waste oils are collected and processed through oil regeneration technologies to preserve valuable resources, offering significant economic and environmental benefits. Over time, oils accumulate oxidation products, impurities, and contaminants that degrade their quality. These degraded oils can no longer meet operational requirements and must either be replaced or regenerated. Regeneration restores the performance of the oils, allowing them to be reused effectively.

Factors Contributing to Oil Degradation

The aging process of industrial oils is influenced by various factors during operation. Over time, oils become contaminated with impurities, moisture, and oxidation products. These changes degrade the chemical and electrophysical properties of the oil, leading to an irreversible aging process. Aging products, often appearing as sludge, accumulate on the active components of transformers, impeding effective heat dissipation.

One primary cause of oil aging is the combined effect of oxygen exposure and the presence of an electric field. Oxygen reactivity increases significantly in the presence of moisture, which often originates from external sources. Elevated operating temperatures, sunlight, and the presence of metals — especially copper and its alloys, which act as oxidation catalysts — further exacerbate the aging process. Additionally, contamination with mechanical impurities and water accelerates this degradation. In the presence of an electric field, the oil tends to retain higher moisture levels, with water droplets and contaminant particles aligning along the field lines, causing a sharp reduction in dielectric strength.

The oxidation of transformer oils is a gradual process that accelerates under certain conditions, such as non-compliance with standard oil quality requirements, elevated temperatures, and the presence of sediment in the transformer tank prior to filling it with new oil. High-voltage equipment often has extensive copper surfaces, which act as active catalysts for oil aging. However, in the absence of oxygen, metals have minimal impact on oil aging.

Changes in physical and chemical properties caused by oxidation generally deteriorate oil performance. A critical indicator of these properties is the resistance of oil to oxidation, which depends on the chemical composition of base oil and the methods used in its purification. Research shows that oils with higher oxidation stability contain a maximum amount of naphthenic and aromatic hydrocarbons with long side chains and a minimal content of cyclic structures. Some resins naturally present in oils can slow down oxidation reactions, while deep purification with sulfuric acid reduces oxidation stability more significantly than resin removal through adsorption.

The rate of oxidation processes in oil is temperature-dependent. Starting at 140 °F, the oxidation rate doubles for every subsequent 18 °F increase in temperature. In a near-vacuum environment, where oxygen is almost entirely absent, oil does not oxidize. Similarly, nitrogen blanketing in transformers prevents contact between oil, oxygen, and moisture, thereby inhibiting oxidation.

Metals vary in their catalytic impact on transformer oil oxidation. Copper, brass, nickel, iron, zinc, tin, and aluminum are ranked in descending order of catalytic activity. This activity ceases when metals develop a protective film formed by oxidation products. Furthermore, organic compounds may also catalyze oil oxidation to varying degrees. A primary indicator of oil aging is the increase in its acid number, which serves as a key criterion for oil usability. However, both the acid number and the type of acids formed should be considered. Low-molecular-weight acids, especially when dissolved in oil containing moisture, are highly corrosive to metals. In contrast, these acids pose less risk in dehydrated oil.

Water is the most harmful impurity in oil, significantly reducing its dielectric strength even in small quantities. Water can exist in oil as dissolved molecules or as emulsified droplets. In the presence of water and an electric field, chemical reactions occur more vigorously. In addition, water accelerates oil oxidation and the degradation of cellulose insulation, particularly cotton-based windings in transformers. It also increases the corrosive effect of oil on steel parts of transformers and related equipment.

Transformer oil has an average service life of 7 to 10 years. However, the products of its degradation and external impurities constitute only a small fraction of its total mass and can be removed through regeneration, restoring the original properties of the oil. Regenerated oil can often be reused together with new oil or with additives, which highlights the importance of proper oil maintenance.

The Difference Between Oil Regeneration and Oil Purification

The terms "oil regeneration" and "oil purification" are often used interchangeably, but they refer to different processes, especially when applied to mineral oils. Oil purification is a process designed to remove contaminants such as gases, water, and other impurities, typically performed either inside or outside the transformer. This process helps maintain the oil in a functional state, but does not restore its original properties.

On the other hand, oil regeneration is a more complex process that not only purifies the oil, but also restores its key characteristics, such as oxidation resistance, viscosity, and clarity. The major difference is that regeneration does not dry out solid insulation materials inside the transformer, but instead restores the balance between the oil and the insulation, thereby improving their interaction.

Regeneration also involves the removal of accumulated contaminants that form in the oil and in the cellulose insulation fibers. After regeneration, the oil becomes significantly cleaner and exhibits improved properties, extending the service life of both the oil and the transformer. Thus, oil regeneration is a more comprehensive process compared to simple oil purification, as it both purifies the oil and restores its important physical and chemical properties.

Methods of Oil Regeneration

Several methods are used for oil regeneration, similar to those applied for refining of base oils. These include distillation, acid-alkaline treatment, selective solvent purification, adsorptive purification, and hydropurification. Adsorptive treatment with the use of natural or activated bleaching clays is one of the most efficient and technologically simple methods. Some common methods are listed below:

• Leaching: oils are treated with alkaline solutions (e.g., NaOH) to neutralize organic acids. However, this method does not remove polymerized oxidation products.
• Acid-Alkaline Treatment: sulfuric acid is the primary reagent, added in varying concentrations depending on the type of oil. While effective, this method generates significant amounts of acidic waste, which makes disposal more difficult.
• Selective Solvent Purification: this method uses solvents to extract undesirable constituents from the oil while preserving valuable hydrocarbons.
• Adsorption Treatment: adsorbents such as bleaching clays remove dissolved aging products, offering a straightforward and environmentally friendly purification solution.

Modern approaches to oil regeneration often focus on minimizing waste generation and maximizing the reuse of treated oils, contributing to both economic efficiency and environmental sustainability.

Fluidex Oil Regeneration Technology

The FLD 12R Oil Regeneration System is designed for regeneration of transformer oils, turbine oils, synthetic and industrial oils, as well as heavy fuel oils, diesel fuels, and dark gas condensates. With a flow rate of 2 to 4.5 gallons per minute (gpm), the system effectively restores transformer oils by removing oil degradation products and acidic components. This regeneration process also clarifies the oil, enhances its resistance to oxidation, and reduces its ability to dissolve gases.

A distinctive feature of the FLD 12R is that it uses a specialized sorbent known as "Fuller’s Earth" for purification and regeneration of oils. The system can handle a variety of oil types, which makes it highly versatile.

The FLD 12R plant is a multipurpose system capable of processing and regenerating various petroleum products. It purifies and clarifies oils and removes aromatic compounds, making the oils suitable for use in various industries. The plant does not require special installation conditions, is easy to transport, and operates with low noise levels, which makes it suitable for businesses with different operational needs.

Regeneration of transformer oils using the FLD 12R system addresses multiple issues:

• Resource conservation: by reusing oils, the demand for new resources is reduced.
• Environmental protection: the regeneration process minimizes the need for waste oil disposal, thereby reducing environmental contamination.
• Reduction of waste disposal costs: less oil needs to be discarded, which significantly reduces waste disposal costs.

Choosing a cost-effective and efficient oil regeneration technology provides a promising solution to these challenges. Regeneration extends the service life of oil and offers significant environmental and economic advantages. The regeneration process requires up to 70% less energy compared to producing oil from raw petroleum, making it a sustainable and cost-effective option for businesses.