How to purify industrial waste oil?

Purifying industrial waste oil involves removing contaminants such as water, solid particles, and chemical impurities to make the oil reusable or safer for disposal. Here’s a common approach to purifying industrial waste oil:

 1. Pre-Treatment

   - Settling and Separation: Allow the waste oil to settle in a tank to separate water and large solid particles. Water and heavier particles will settle at the bottom, while oil floats above.

   - Filtration: Use coarse filters or strainers to remove large debris and sediment. This step helps protect downstream purification equipment.

 2. Heating

   - Heat the Oil: Heating the oil reduces its viscosity, making it easier to filter. Typically, waste oil is heated to about 60–80°C (140–176°F) to aid in the separation of contaminants.

   - Dehydration: Heating also helps evaporate some water content in the oil.

 3. Filtration and Centrifugation

   - Centrifugation: Use a centrifuge to separate water, sludge, and fine particles from the oil. The centrifugal force separates heavier contaminants from the lighter oil.

   - Fine Filtration: Filter the oil using progressively finer filters (e.g., 5–10 microns, then down to 1 micron if possible). This helps remove smaller particulates and improves oil purity.

 4. Vacuum Dehydration (Optional but Effective)

   - Vacuum Dehydration Unit: If water content is still high, vacuum dehydration can remove dissolved and emulsified water. The process involves heating the oil under a vacuum, which lowers the boiling point of water, allowing moisture to evaporate.

 5. Adsorption and Chemical Treatment

   - Clay or Activated Carbon Treatment: Pass the oil through columns containing adsorbent materials like clay, activated carbon, or silica gel. This step removes color, acids, and polar contaminants.

   - Chemical Additives: In some cases, chemicals like coagulants or neutralizing agents are added to further clean and stabilize the oil.

 6. Polishing and Quality Testing

   - Final Filtration (Polishing): Perform a final filtration stage to ensure all residual particles are removed.

   - Testing: Test the purified oil for parameters like viscosity, water content, particle count, and acid number to ensure it meets the desired standards.

 7. Optional: Re-refining (for High-Quality Base Oil)

   - Distillation and Hydrogenation: If a high-quality base oil is needed, additional steps such as vacuum distillation, hydrogenation, or solvent extraction are used to remove all impurities. These processes are more complex and typically require specialized industrial re-refining facilities.

This process can vary depending on the type of oil and level of contamination, and equipment such as filtration systems, centrifuges, vacuum dehydrators, and adsorption units are often used in combination to achieve the best results.