Used oil is a valuable resource that can be recycled and refined into high-quality lubricants and fuels. Unfortunately, most of the used oil is burned or disposed of in landfills, posing environmental risks. The used oil re-refining process involves several stages that use different technologies to remove impurities and contaminants. The final products include base oils, fuel oils, and asphalt. In this article, we will discuss the main processing steps of waste oil re-refining, their benefits, and the importance of recycling used oil. By the end, you will have a better understanding of the process and its contribution to sustainability.
Sources of Used Oil for Refining Process
Used oil is generated from a variety of sources, including automotive oils, industrial oils, and hydraulic fluids. The improper disposal of used oil can cause environmental damage, as it can contaminate soil and water resources. Therefore, recycling and waste oil re-refining used oil is important in reducing pollution and conserving natural resources.
According to the Environmental Protection Agency (EPA), about 1.3 billion gallons of used oil are generated in the United States each year. Of this amount, only 10% is recycled and re-refined. The rest is either burned for energy recovery or disposed of in landfills.
| Source of Used Oil for used oil re-refining | Characteristics |
| Automotive oils | Generated from cars, trucks, and other vehicles |
| Industrial oils | Generated from machinery, turbines, and hydraulic systems |
| Hydraulic fluids | Used in industrial and transportation equipment |
| Marine oils | Used in marine engines and hydraulic systems |
| Transformer oils | Used in electrical transformers and other equipment |
| Cooking oils | Used in restaurants and households |
As shown in Table, automotive and industrial oils are the main sources of used oil. These oils contain contaminants such as water, dirt, and metals that can affect their performance and lead to equipment failure. Therefore, it is important to recycle and re-refine used oil to remove these contaminants and extend the lifespan of the oil.
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5 Steps of waste oil re-refining
There are some steps to process and refining of used oil. In continue, we read about some main steps:
1-Pre-treatment for used oil re-refining
The first step in used oil re-refining is pre-treatment, which involves removing any large particles, such as dirt or metal, from the used oil. This is typically done through a filtering process, which separates the larger particles from the oil.
a. Dewatering
The first step in the pre-treatment stage is dewatering, which involves removing any water from the used oil. This is usually achieved through the use of settling tanks or centrifuges. Removing water is important as it can cause corrosion and reduce the efficiency of the refining process.
b. Solvent Extraction
Solvent extraction is another method used in the pre-treatment stage. This process involves the use of solvents to remove any contaminants, such as heavy metals or sulfur, from the used oil. The solvent used is typically a polar solvent, such as methanol or ethanol, which helps to dissolve the contaminants and separate them from the oil.
c. Filtration
Filtration is also used in the pre-treatment stage to remove any solid particles that may be present in the used oil. The oil is passed through a series of filters, which remove any particles larger than the filter’s pore size. Filtration is essential as it ensures that the oil is clean and free from any contaminants that may interfere with the distillation process.
2-Distillation
After pre-treatment of used oil re-refining process, the used oil is heated and put through a distillation process. During this process, the oil is separated into different fractions based on their boiling points. The lighter fractions, such as gasoline, are distilled first, while the heavier fractions, such as diesel fuel, are distilled later.
a. Vacuum Distillation
Vacuum distillation is a common method used in the distillation stage. This process involves heating the used oil in a vacuum to reduce the boiling point of the components. This allows for the separation of the components without causing thermal degradation. Vacuum distillation is particularly useful for separating heavy components, such as waxes and asphalt.
b. Atmospheric Distillation
Atmospheric distillation is another method used in the distillation stage. This process involves heating the used oil under atmospheric pressure to separate the different components. The components are then collected in different trays, depending on their boiling points. Atmospheric distillation is particularly useful for separating lighter components, such as gasoline and diesel fuel.
c. Solvent Deasphalting
Solvent deasphalting is a method used to remove asphaltenes from the used oil. This process involves adding a solvent to the used oil, which dissolves the asphaltenes. The asphaltenes are then removed from the solvent using filtration. Solvent deasphalting is particularly useful for producing base oils and lubricating oils.
3-Hydrotreating in waste oil re-refining
Hydrotreating is a process that uses hydrogen gas and a catalyst to remove sulfur, nitrogen, and other impurities from the oil to have best results in used oil re-refining process. The oil is heated and mixed with hydrogen gas under high pressure, and the catalyst helps to break down the impurities. This process is essential in improving the quality of the oil and meeting environmental standards.
a. Hydrogenation
Hydrogenation is a process used in the hydrotreating stage to improve the viscosity index of the refined oil. The process involves adding hydrogen to the refined oil in the presence of a catalyst. The hydrogen reacts with the impurities in the oil, such as sulfur, nitrogen, and oxygen, to form hydrogen sulfide, ammonia, and water. These impurities are then removed, resulting in a higher quality oil.
b. Hydrofinishing
Hydrofinishing is a process used in the hydrotreating stage to improve the color and odor of the refined oil. The process involves adding hydrogen to the refined oil in the presence of a catalyst. The hydrogen reacts with the impurities in the oil, such as unsaturated compounds and aromatics, to form saturated compounds. These impurities are then removed, resulting in a higher quality oil with improved color and odor.
c. Hydrocracking
Hydrocracking is a process used in the hydrotreating stage to break down heavy components in the refined oil into lighter components. The process involves adding hydrogen to the refined oil in the presence of a catalyst. The hydrogen breaks down the heavy components, such as waxes and asphaltenes, into lighter components, such as gasoline and diesel fuel. This process results in a higher yield of valuable products from the refined oil.
4-Post-treatment process of used oil re-refining
After hydrotreating, the oil is put through a post-treatment process, which involves removing any remaining impurities and improving its stability. This is typically done through a combination of filtering and chemical treatments, which help to remove any remaining contaminants and stabilize the oil.
a. Hydrogenation
Hydrogenation is a common method used in the post-treatment stage of waste oil re-refining. The process involves adding hydrogen to the refined oil in the presence of a catalyst. The hydrogen reacts with any remaining impurities, such as unsaturated compounds, to form saturated compounds. This process further improves the stability and quality of the refined oil.
b. Solvent Extraction
Solvent extraction is another method used in the post-treatment stage. The process involves using a solvent to extract any remaining impurities from the refined oil. The solvent is added to the oil and the mixture is agitated. The impurities dissolve into the solvent, which is then separated from the oil. This process is particularly effective at removing heavy metals and other contaminants from the oil.
c. Adsorption
Adsorption is a process to remove any remaining impurities that could not be removed through other methods. The process involves using adsorbent materials, such as activated carbon or clay, to attract and remove impurities from the refined oil. This process is particularly effective at removing color and odor compounds from the oil.
5-Product Recovery of waste oil re-refining
Finally, the refined oil is ready for product recovery. The oil can be used to produce a variety of products, including base oils, fuel oils, and asphalt. Base oils are used in the production of lubricants, while fuel oils are used for heating and powering industrial processes. Asphalt is used in the construction of roads and other infrastructure.
a. Separation
The separation process involves separating the refined oil into different products based on their properties. For example, light fractions such as gasoline and diesel are separated from heavier fractions such as lubricating oil. This process is typically carried out using distillation columns, which separate the different fractions based on their boiling points.
b. Purification
The purification process is used to further refine the separated products and remove any remaining impurities. This process is part of used oil re-refining and it’s typically carried out using methods such as hydrogenation and solvent extraction, which were also used in earlier stages of the refining process.
c. Filtration
The final step in the product recovery stage is filtration, which involves removing any remaining impurities from the purified products. This process is critical to ensuring that the refined oil meets industry standards for purity and quality.
Uses and Benefits of Refining Used Oil
Recycling and refining used oil has numerous benefits, including reducing pollution, conserving natural resources, and generating revenue. Refined used oil can be used in various applications, including lubricants, hydraulic fluids, and fuels.
Base oils are one of the main products of used oil re-refining. These oils can be further processed to create high-quality lubricants that meet industry standards. Refined base oils have excellent thermal and oxidative stability, low volatility, and high viscosity index. These properties make them ideal for use in automotive and industrial applications.
Fuel oils are another product of waste oil re-refining. These oils can be blended with other fuels to create products such as marine diesel and home heating oil. Refined fuel oils have lower sulfur content, reducing their environmental impact.
| Application | Benefits |
| Lubricants | High-quality base oils can be used to make lubricants |
| Hydraulic fluids | Can be used in hydraulic systems and other applications |
| Fuels | Can be blended with other fuels to create marine diesel and heating oil |
| Asphalt | Can be used to make paving materials and roofing products |
In order to this table, refined used oil can be used in a variety of applications, including lubricants, hydraulic fluids, fuels, and asphalt. By recycling and refining used oil, we can reduce our dependence on virgin oil, conserve natural resources, and reduce pollution. It is estimated that for every gallon of used oil that is re-refined, one less gallon of crude oil is needed. This makes used oil recycling and refining an important aspect of creating a sustainable future.
Conclusion
used oil re-refining is an essential process that offers significant benefits to the environment, the economy, and society as a whole. By waste oil re-refining and recycling, we can reduce pollution, conserve natural resources, and generate revenue. The main processing steps of used oil re-refining include collection and pre-treatment, distillation, hydrotreating, and product finishing. These steps ensure that the refined used oil meets industry standards and can be used in various applications, including lubricants, hydraulic fluids, fuels, and asphalt.
Refined used oil offers a range of advantages, including high-quality base oils that meet industry standards, lower sulfur content in fuel oils, and reduced greenhouse gas emissions in asphalt production. By using refined used oil, we can reduce our dependence on virgin oil, conserve natural resources, and create a more sustainable future.
Overall, used oil re-refining is a crucial process that offers many benefits to society. By continuing to improve and promote this process, we can create a more sustainable future for generations to come.