Processing waste oil involves several key stages to transform used oil into usable products or make it suitable for disposal or further refining. This multi-step approach ensures contaminants are removed and valuable components are recovered.
The typical process involves a series of pre-treatment and refining steps.
Stages of Waste Oil Processing
Based on standard practices, the processing of used oil often follows a specific sequence of operations designed to remove impurities and separate different components.
Here are the primary stages involved in processing waste oil, according to common methods:
1. Dewatering
- Purpose: To remove free water from the collected used oil.
- Process: After collecting used oil, the material goes through initial pre-treatment stages. One crucial step is dewatering, which separates water that isn't chemically bound to the oil. This is often done using gravity separation or heating.
2. Demulsification
- Purpose: To break down oil-water emulsions and remove bound water.
- Process: For oil emulsions where water is tightly mixed with the oil, simply separating by gravity or heat isn't enough. These mixtures require more specialized separation techniques, often involving the addition of a demulsifier chemical that helps break the emulsion, allowing the water to separate more easily.
3. Filtration and Demineralization
- Purpose: To remove solid particles and dissolved minerals.
- Process: After water removal, the oil is typically filtered to remove suspended solids, sludge, and other particulate matter. Demineralization may also be performed to remove dissolved metallic compounds and other inorganic contaminants that can be harmful in subsequent refining steps or final products.
4. De-Asphalting With Propane
- Purpose: To remove heavy asphaltic components and residues.
- Process: This stage targets the heavier, tar-like substances (asphaltenes) present in the waste oil. Using propane as a solvent can help precipitate these heavy fractions, separating them from the lighter, more valuable oil components.
5. Fractionation
- Purpose: To separate the refined oil into different products based on their boiling points.
- Process: The final major step is often fractionation (distillation). The pre-treated and de-asphalted oil is heated, and different hydrocarbon fractions (like lubricating oil base stocks, fuels, etc.) vaporize at different temperatures. These vapors are then condensed and collected separately, yielding various products.
These stages work together to purify waste oil, reducing its environmental impact and recovering valuable resources that can be reused.
