How to filter and purify industrial waste oil?

Purifying industrial waste oil involves several processes aimed at removing contaminants such as dirt, water, metals, carbon, and other impurities that degrade the oil’s quality. Proper purification of industrial waste oil not only extends the lifespan of the oil but also helps in reducing environmental impact by recycling the oil for reuse in machinery or other applications.

There are several methods and technologies used to purify industrial waste oil. Below are the steps and techniques involved in purifying waste oil:

 1. Preliminary Filtration

   - Purpose: Remove large particles such as debris, metal shavings, dirt, and sludge that may be present in the used oil.

   - Method:

     - Mechanical Filtration: This is the first step in the purification process. Mechanical filters (such as mesh or paper filters) are used to filter out large particles from the oil.

     - Strainers: These can be used to remove any coarse debris before the oil moves into further purification processes.

 2. Dehydration / Water Removal

   - Purpose: Eliminate any water content in the waste oil. Water is one of the main contaminants that can cause emulsification, corrosion, and degradation of oil.

   - Method:

     - Vacuum Dehydration: This method uses vacuum distillation to lower the boiling point of water, enabling it to evaporate at lower temperatures. The water vapor is then separated from the oil and collected.

     - Centrifugal Separation: In this method, centrifugal force is used to separate water droplets from the oil. The oil is rapidly spun, causing water, which has a higher density than oil, to move outward and be collected separately.

     - Heating: Mild heating can also be used to evaporate water, which is then condensed and removed.

 3. Degassing (Optional)

   - Purpose: Remove dissolved gases, air, and light volatile compounds that may be in the oil. These can cause oxidation and degradation.

   - Method:

     - Vacuum Degassing: Similar to dehydration, vacuum degassing reduces the pressure in the oil tank, causing dissolved gases and light oils to escape from the waste oil.

     - Thermal Degassing: In some cases, heating the oil to a moderate temperature (usually between 50-80°C) helps to release dissolved gases from the oil.

 4. Filtration / Fine Particle Removal

   - Purpose: Remove fine particles like soot, carbon, and other microscopic impurities that can cause wear and tear on machinery.

   - Method:

     - Activated Carbon Filtration: Activated carbon is used to adsorb fine particles and dissolved impurities. It is highly effective in removing particulate matter and small organic contaminants.

     - Microfilters: Fine mesh filters or paper filters are used for removing smaller particles from the oil. These filters can capture particles down to microns in size, ensuring that only clean oil passes through.

     - Clay Filtration: A process that uses clay or other adsorbents to remove solid contaminants and also some harmful chemicals like sulfur compounds and acidic residues.

 5. Distillation / Vacuum Distillation

   - Purpose: Separate heavier contaminants such as metals and carbon particles from the base oil. It also helps to remove lighter oils and impurities.

   - Method:

     - Vacuum Distillation: This process involves heating the waste oil to high temperatures in a vacuum distillation column. The oil is separated into different components based on their boiling points. Lighter oils and contaminants (such as gasoline or diesel residues) will vaporize at lower temperatures and can be separated from the cleaner, heavier oils.

     - Fractional Distillation: If required, distillation can be done in stages to separate different fractions of the oil and remove unwanted impurities efficiently.

 6. Regeneration / Chemical Treatment

   - Purpose: Remove or neutralize harmful chemicals and breakdown products formed during the oil’s usage, such as acidic components, oxidation by-products, or metals.

   - Method:

     - Acid-Clay Treatment: The oil is treated with acid and clay to neutralize acidic contaminants, remove sulfur and nitrogen compounds, and purify the oil. The acid reacts with the contaminants, and the clay adsorbs them, leaving cleaner oil behind.

     - Alkaline Treatment: Sometimes, alkaline solutions are added to neutralize acidic contaminants and remove acidic oils.

     - Chemical Additives: Some purifiers use special additives that help to neutralize contaminants or improve the properties of the oil, such as antioxidant additives or de-emulsifiers to break up water-oil emulsions.

 7. Decontamination Using Centrifugation

   - Purpose: Further separate solid particles (like metals, sludge, and carbon) from the oil by using centrifugal force.

   - Method:

     - Centrifugal Separators: These machines use high-speed spinning to separate contaminants based on their densities. Heavier particles, including metals, dirt, and carbon, are forced to the outer walls, where they are collected, while cleaner oil remains in the center and is extracted for further use.

8. Polishing and Final Filtration

Purpose: Remove any remaining trace amounts of contaminants to produce purified, high-quality oil.

Method:

Polishing Filters: These are fine filters used in the final stage of the purification process. They ensure that no fine particles or microscopic contaminants are left in the oil.

Micron Filters: These filters have very fine mesh sizes (often in the micron range) and ensure that even small particles are removed from the oil.

9. Reconditioning or Additive Addition (Optional)

Purpose: Restore the oil’s properties and improve its performance.

Method:

After the waste oil has been purified, oil reconditioning can include the addition of fresh additives such as antioxidants, anti-wear agents, corrosion inhibitors, or anti-foaming agents to restore the oil’s chemical properties and enhance its performance in machinery.

10. Final Quality Control

Purpose: Ensure the oil meets the required specifications for reuse.

Method:

Testing: The purified oil should be tested for viscosity, acidity, water content, and particle contamination levels. If the oil meets the required standards, it can be reused in industrial machinery or as a base oil for new lubricants.

Common Types of Oil Purification Systems

Offline Oil Purifiers: These systems work by circulating the oil through a purification unit after it has been drained from the equipment. The oil is filtered, heated, and treated externally before being returned.

Online Oil Purifiers: These units are directly connected to the machinery and continuously purify the oil as it circulates through the system. This is more convenient for continuous operations, such as in turbines or large industrial engines.

Portable Oil Purifiers: These are smaller, mobile units that can be used in the field or for specific, localized cleaning tasks.

Key Benefits of Waste Oil Purification

Cost Savings: Reusing purified oil reduces the need for purchasing new oil.

Environmental Protection: Proper waste oil treatment reduces the impact of oil disposal on the environment.

Machinery Longevity: Clean oil helps reduce wear and tear on machinery, improving performance and extending lifespan.

Sustainability: Recycling and reusing waste oil conserves resources and reduces the need for new oil production.

In summary, purifying industrial waste oil involves a combination of filtration, dehydration, distillation, and chemical treatments to remove contaminants and restore the oil to a usable state. The purification method chosen will depend on the type of waste oil, its contaminants, and the desired end-use for the oil.