Reclamation of Aged Transformer Oil Using Thermally Activated Sludge Derived from Drinking Water Treatment | ||||
| Egyptian Journal of Chemistry | ||||
| Volume 68, Issue 11, November 2025, Page 51-71 PDF (588.96 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/ejchem.2025.384309.11768 | ||||
 View on SCiNiTO | ||||
| Authors | ||||
Ahmed M. El Deeb1; Ashraf I. Hafez2; Ibrahim E. El-Sayed3; Abdel Aleem H. Abdel Aleem3; Ahmed I. Hashem4; Ahmed A. I. Khalil  5
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| 1Central Chemical Labs, Egyptian Electricity Transmission Company, Ministry of Electricity, Cairo, Egypt | ||||
| 2Egyptian Electricity Holding Company, Ministry of Electricity, Cairo, Egypt | ||||
| 3Department of Chemistry, Faculty of Science, Menoufia University, Menoufia, Egypt | ||||
| 4Department of Chemistry, Faculty of Science, Ain Shams University, Cairo, Egypt | ||||
| 5Chairman of Laser Sciences and Interactions Department, National Institute of Laser Enhanced Sciences, NILES, Cairo University, 12613, Giza, Egypt | ||||
| Abstract | ||||
| For electrical equipment (transformer) to last a long time, insulating oils are essential. The lifespan of a transformer is impacted by the ageing and degradation process of insulating oils under operating conditions. Since insulating oils are costly, regeneration is preferable to replacement. The most common materials used in this manner are aluminium oxides and silicates. In this work, aluminium oxides and silicates are obtained from the sludge produced from drinking water treatment. When water is treated with aluminium sulphate (alum), the produced sludge is enriched with silicon and aluminium oxides, as well as traces of Fe, Ca, Mg, Na, and K oxides. The produced sludges were thoroughly examined both quantitatively and qualitatively using different spectroscopic techniques. The performance of the extracted sludges is attributed to the large surface area. After the grinding method, the sludge was preheated at temperatures of 200°C, 400°C, 600°C, and 800°C for 2 hours to yield particles with high adsorption capacity, which increases with increasing activation temperature. Thus, a three-step lab-scale refining process was exactly applied. First, a physical oil refining process without a sludge refining cycle was performed to reduce water, gases, and sediments. Second, the sludge was used at varying doses with continuous stirring at different temperatures for 30 minutes to remove the aging products in the oil. Finally, three additional physical oils without sludge refining cycles were conducted. The optimum conditions were verified at 65°C with continuous stirring for 30 minutes using sludge dose 32% preheated at 800°C, under which the oil properties were improved significantly such as breakdown voltage, water content, colour, acidity, interfacial tension, dielectrically dissipation factor, Furanic compounds content, total dissolved gases, and sulphur content were dark with suspended matter as follow 23 k.v./2.5 mm, 64 ppm, 6.5, 0.38 mg KOH/g oil, 19.3 mN/m, 0.44, 3818 ppb, 4247 ppm, and 0.39 % while after treatment process, the values were changed and became clear, free from sediment and suspended matter as follow 71 k.v./2.5 mm, 7 ppm, 1.5, 0.01 mg KOH/g oil, 40.2 mN/m, 0.0006, 109 ppb, 888 ppm, and 0.01 % respectively. It was found that the parameter values after the treatment process meet the IEC 60296-2020 standard for evaluating unused mineral insulating oils for transformers and switchgear. | ||||
| Keywords | ||||
| Insulating oils; Adsorbent material; water treatment sludge; transformer oil quality | ||||
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