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Time：2025-04-23 11:04:25 Reading volume：
Oil purification and treatment refers to the removal of pollutants (such as moisture, solid particles, colloids, acidic substances, etc.) in oil through physical, chemical or combined processes to restore its performance or meet environmental emission standards. Different types of oil (lubricating oil, hydraulic oil, transformer oil, fuel oil, etc.) require targeted purification methods.
| Types of pollutants | Main sources | Hazards |
|----------------|-------------------------------|--------------------------------------------------------------------------|
| Solid particles | Metal wear debris, dust, carbon residue | Cause equipment wear, block oil circuits, and affect lubrication performance |
| Water | Condensate, leakage, emulsification | Accelerate oil oxidation, corrode metal parts, and reduce lubricity (hydraulic oil/transformer oil is particularly sensitive) |
| Air/gas | Dissolved air, foam | Reduce oil compressibility (hydraulic system), promote oxidation |
| Gum/asphalt | Oil oxidation products | Form sludge, block filter elements, and reduce fluidity |
| Acidic substances | Oxidation to generate carboxylic acids and sulfides | Corrode metals and accelerate oil degradation |
| Additive loss | Long-term use, high-temperature decomposition | Reduce anti-wear, anti-oxidation and other properties |
1. Physical purification method
It is mainly used to remove mechanical impurities, moisture and gas without changing the chemical composition of the oil.
| Method | Principle | Applicable scenarios | Treatment effect |
|------------------|--------------------------------------------------------------------------|------------------------------------------|------------------------------------------|
| Filtration | Intercept particles (1~50μm) through filter element, filter cloth, filter screen | Lubricating oil, hydraulic oil, gear oil | Remove solid impurities (metal chips, dust) |
| Centrifugal separation | Use centrifugal force to separate substances of different densities (water, solids, oil) | High water content waste oil (ship fuel, rolling mill oil) | Rapid dehydration, slag removal |
| Vacuum dehydration | Heating and evaporating water and light volatiles under negative pressure | Transformer oil, turbine oil | Water content can be reduced to below 50ppm |
| Coalescing separation | Coalescing filter element makes tiny water droplets merge into large water droplets, and then settle and separate | Emulsified oil (cutting fluid, turbine oil) | Demulsification, water content ≤100ppm |
| Electrostatic purification | High-voltage electrostatic field adsorbs colloidal particles and tiny impurities | Precision oil (aviation hydraulic oil) | Removal of particles larger than 0.1μm |
2. Chemical purification method
Mainly used to remove acidic substances, colloids and deep oxidation products, which may change the chemical properties of the oil.
| Method | Principle | Applicable scenarios | Treatment effect |
|------------------|--------------------------------------------------------------------------|------------------------------------------|------------------------------------------|
| White clay adsorption | Activated white clay adsorbs colloids, pigments and acidic compounds | Waste oil regeneration, transformer oil | Reduce acid value and improve color |
| Pickling-alkali neutralization | Sulfuric acid removes impurities, and then uses alkali to neutralize residual acid | Deep regeneration of waste lubricating oil | Removal of heavy metals and sulfides |
| Solvent extraction | Use propane, NMP and other solvents to separate harmful components in oil | Refine base oil from waste oil | Recover high-purity base oil |
| Hydrogenation refining | Hydrogenation under high temperature and high pressure to remove impurities such as sulfur, nitrogen, and oxygen | High-end oil regeneration (synthetic oil) | Close to new oil standards |
3. Combined process (physical + chemical)
Applicable to severely polluted waste oil, such as waste engine oil, industrial waste oil, etc.
Typical process:
1. Pretreatment: centrifugation/filtration to remove large particles of impurities.
2. Dehydration and degassing: vacuum distillation or coalescence separation to remove water and air.
3. Chemical treatment: white clay adsorption or solvent extraction to remove colloids and acidic substances.
4. Post-refining: hydrogenation or supplementation of additives to restore performance.
| Oil type | Main pollutants | Recommended purification method |
|------------------|----------------------------|------------------------------------------|
| Transformer oil | Water, gas, particles | Vacuum dehydration + precision filtration |
| Hydraulic oil | Particles, water, oxidation products | Coagulation dehydration + electrostatic purification |
| Engine oil | Carbon slag, metal chips, acidic substances | Centrifugal separation + white clay adsorption |
| Gear oil | Metal wear particles, water | Magnetic filtration + vacuum dehydration |
| Cutting fluid | Emulsified water, metal powder | Demulsification + centrifugal separation |
1. Economic analysis
- Regeneration cost: The regeneration cost of lightly contaminated oil (such as hydraulic oil) is about 30%~50% of new oil, and the regeneration cost of heavily contaminated oil (such as waste oil) may reach 70%.
- Recovery rate: Generally, 80% to 95% can be recovered, and deep treatment (such as hydrogenation) can reach 98%.
2. Environmental protection requirements
- Emission standards: must comply with the "Pollution Control Standards for Waste Mineral Oil Recycling" (GB 17145).
- Hazardous waste: Waste oil belongs to the HW08 category, and illegal discharge may face penalties.
1. Intelligent purification equipment: online monitoring of oil quality and automatic adjustment of purification parameters.
2. Green chemical process: reduce the environmental impact of pickling and solvent extraction.
3. Nanofiltration technology: higher precision impurity separation (such as graphene filter membrane).
Oil purification and treatment need to choose the appropriate method according to the type of oil, degree of pollution and use requirements. Physical methods are suitable for daily maintenance, chemical methods are used for deep regeneration, and combined processes can maximize the recovery rate. As environmental regulations become stricter, efficient and low-pollution oil purification technology will become the mainstream of the industry.
