Posted in Recycle Silicone

Recycling of Silicone Transformer Oil

1. Introduction

One of the strongest value points and least understood benefits of silicone fluid is the variety of options available to customers at end-of-use. Minimization and reuse or recycle are much preferred alternatives to product disposal.

For transformer manufacturers, service companies and large utility customers, minimization can take many forms. They include:

• Purchasing the proper quantity of material to reduce excess
• Minimizing the length of transfer piping that may require cleaning
• Reviewing the systems to ensure secure storage, transfer and usage
• Protecting the equipment against physical damage

Eco USA collects the oil for recycling and then processes it into a form suitable for re-use. Eco USA has various options for recycling silicone transformer oil.

2. Recycling*)

Recycling options include:

• Reusing the material in the same application
• Reprocessing of fluid contaminated with water,particulates or mineral oil
• Special reprocessing of fluids contaminated with PCB
• Fuel blending to recover energy

In some cases, the fluid can be reused in the same application without reconditioning.For instance, Dow Corning 561 Silicone Transformer Oil can also be reprocessed to remove contaminants and then reused in transformers in many cases.

The recycling program can be designed to accept fluids contaminated with water or particulates and that also meet certain other recycling criteria. Additionally, the program can reprocess fluid that has been contaminated with mineral oil.

This contamination may have resulted from different scenarios, but the most common one occurs when transformers originally filled with mineral oils are retrofillled with silicone fluid to improve fire safety and reduce long-term maintenance.

Silicone fluid used to flush the mineral oil transformer can also be recycled.

The returned fluid to Dow Corning is for instance completely restructured through chemical reprocessing and then used to rebuild other specific silicone products. Anyhow, Dow Corning program can not, under any circumstances, accept fluids from prior use of PCB fluids.

SunOhio Co. specializes in PCB-contaminated materials and is an option for those transformers that may contain PCB-contaminated fluids resulting from prior use of PCB fluids.

Fuel blending is another recycling alternative. Most non-PCB-contaminated silicone fluids are considered nonhazardous materials when disposed and can be compatibly blended with many organic solvents or other fuels. However, oxidizers and other incompatible materials as spelled out in the material safety data sheets should not be blended with silicones.

Silicones have two advantages when properly used in fuel-blending operations. Silicone fluids have a fuel value of approximately 8000 Btu per pound, providing a favorable heat balance for fuel-use applications. Further, when silicone fluids are burned in silica-demanding processes such as cement kilns, the resulting silica becomes a valuable component of the product.

Silicone-containing materials should not be burned in internal combustion engines or other operations in which ash generation may interfere with the operation of the equipment. Always the equipment specifications and/or local regulation have to be checked as appropriate prior to combusting silicone materials.

It is it important to have purified oil in a transformer because dissolved gasses in transformer oil can cause arcing, corona discharges, and overheating–reducing the electrical efficiency and lifetime of the transformer. Likewise, water contamination at levels as low as 30 ppm (parts per million) can adversely affect the insulating strength of the oil. With ever-increasing standards for energy efficiency of power distribution transformers, the need to effectively degas will become even more important in the future. particles contamination will also affect the function of insulating oil. So the used transformer oil has to be cleaned.

2.1. Application***)

The Zhongneng Oil regeneration system (Series ZYD) has been specially designed for on site use to completely regenerate insulating oils in energized or de-energized transformers. The ZYD system provides regular oil purification such as degassing, drying and particulate removal but also can remove acidity, sludge, other soluble oil decay products and discoloration.

This is accomplished by the use of high vacuum degasification technology and particulate filters combined with our special brand of earth. After treating, the oil can be reused as new. For special application, the system also can be mounted on a leak proof base and can be installed and operated on a trailer.

2.2. Features of the regeneration system

1. Besides the common vacuum oil purifier’s function of dewatering, degassing and eliminating particles, this machine can regenerate the seriously deteriorated oil by removing the polarity materials, such as the deep oxides, free carbon in the oil effectively. It can make the seriously deteriorated oil reach to the normal index like anti-oxides, acid-alkali water-solubility.
2. Operational can be P.L.C (Programmable Logic Controller).
3. Unique vacuum dehydration, degassifier, regeneration system, adopt stereo-evaporation technology, high efficiently remove water, gas, particles from transformer oil, improve oil quality and dielectric strength.
4. Duplex 3D stereo-evaporation, eliminating the liquid water quickly.
5. UK technology by which the trace water that is show chain, such as dissolved water, can be removed effectively.
6. Instinctive removing impurities system filtering through double FH trapezoidal network and absorbing by high polymer without the mechanical power.
7. Advanced infrared liquid-level automatic control system to accomplish fully automatic control.
8. Specially applied to vacuum oiling and drying for power transmission equipments.
9. The oil of any grades can be treated either on- or off-load.
10. Special oil pump design with lower noise.
11. Special additives for depolarization, can recover oil color of aged transformer oil to new, equipped with flexible unloading device of short time, good efficiency small quality. Discolor under vacuum can save cost of treatment, the impurities doesn’t pollute environment (it can be used to architecture and road pave)

2.3. Advantages of the system

Comparing with the single-stage vacuum oil purifier, this machine can dewater, degas and removes the impurities more quickly, more completely, and makes the oil BDV (Breakdown Voltage) of 70kV or higher. As the bridge-type vacuum linking system that can purify and also can be an independent vacuum power supply, this machine can treat the electric insulation devices.(oil purifier, oil purification, oil filtration, oil recycling, oil treatment, oil regeneration, oil restoration, oil filtering, oil disposal, oil reclaiming, oil management, energy saving, oil reconditioned, oil reconstituted, oil restituting, oil recovering ,oil filtration, oil filter, petroleum machine)

The amount of oil used in a transformer depends on the size of the transformer. A relatively small-sized (1 000 kV•A) transformer is assumed, which requires about 1.89 m3(500 gal) of fluid to cool. It is assumed that the use phase of the transformer oil lasts the lifetime of the transformer, approximately 30 years. Included in the modeling is the electricity required to recondition the oil when dissolved gas analysis tests indicate the need. Reconditioning is assumed to occur every five years.

2.4. End-of-life

With periodic reconditioning of silicone-based transformer oil during the 30-year life of the transformer, the oil is in good enough condition for half of it to be further reconditioned and reused in another transformer. The other half is sent back to the manufacturer for restructuring for production into other silicone-based products. End-of-life options for transformer oil do not include disposal, as it is generally a well-maintained product and can be used in other applications. Therefore, none of the product is assumed to be landfilled.

2.5. Environmental impact ****)

Notes about the end-of-life of the transformer are summarized below:

The copper and steel can be recycled for 100 %. For the moment, silicone oil is burned in incinerators at the same cost as mineral oil. However, an European recycling business for silicone liquid is already active since 2001. Mineral oil can also be recycled but is usually burned and used for production of electricity. The windings of the cast resin transformer have to be treated or need energy and high temperature burning.

A recycling company with factories in 4 European countries, recycles oil filled transformers at 75 – 100 EUR/ton. PCB contaminated transformers at 1200 EUR/ton and dry type transformers at 150-160 EUR/ton.

Silicone liquid will degenerate slowly into natural existing products and shows no harmful or contamination effects. If silicone liquid is spoiled in water (salt or not salt) it will not react with the water and sink to the bottom and degenerate slowly into carbon dioxide, water and other natural products. The liquid will not take oxygen out of the water.

Mineral oil will react with the environment and oxidize. It has to be mentioned that transformers can be considered as leak free. They leave the factory leak free and can only be damaged during transport or installation. Once in service, they remain closed for their lifetime.

3.Incineration and landfill

If other reuse and recycle methods have been thoroughly investigated, and destruction is the only remaining alternative, incineration of silicones fluids can be considered. As with fuel blending and other combustion activities, incineration must consider the heat content of silicones and the silica ash generated by the combustion process.

Absorbents or other solid materials contaminated with silicone oils that might have been generated during maintenance or clean up of minor leaks or spills ( assuming no PCB contamination is present ) can be landfilled if local regulations allow.
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*) Dow Corning Technical Brochure
**) National Renewable Energy Laboratory (NREL): U.S. Life-Cycle Inventory Database. 2005. Golden, CO. http://www.nrel.gov/lci/database.
***) Kingstone Oil Filtration Engineering Co. Brochure, Ltd,28-Jan-2011
***”) International Conference on Electricity Distribution Barcelona, 12-15 May 2003
PAU, Declercq,A1 Session 4 Paper No 25