Traditional natural ester insulating oils are mostly produced from edible vegetable oils, leading to high costs and competition with food supplies. China produces a huge amount of kitchen waste cooking oil annually. However, due to its high acid value and serious degradation, it is difficult to directly prepare high-performance insulating oil, and related research has long been lacking.
In this study, a multi-stage coupled refining process consisting of phosphoric acid degumming, alkali refining deacidification, activated carbon adsorption decolorization/deodorization and winterization was constructed. The high-acid-value waste cooking oil with an initial acid value of 21.04 mg KOH/g was deeply purified to 0.024 mg KOH/g; the dielectric dissipation factor at 90℃ decreased from 1.335 to 0.0197, and the power frequency breakdown voltage increased from 27.9 kV to 72 kV. All physical, chemical and electrical properties meet the requirements of DL/T 1811—2018 for natural ester insulating oil. By adding BHT antioxidant, the initial oxidation temperature of the oil was increased from 143.12℃ to 180.34℃, significantly enhancing the long-term stability.
This achievement realizes the resource conversion of waste cooking oil into high-performance insulating oil, balancing environmental protection, safety and the “dual carbon” goals, and provides a new eco-friendly insulation material solution for the construction of green power grids. The work entitled “Study on the Preparation of Natural Ester Insulating Oil from High-Acid-Value Waste Cooking Oil Based on Multi-Stage Coupled Refining Process” was published on Journal of Engineering Studies (published on Mar. 16, 2026).
DOI: 10.3724/j.issn.16744969.20250131