Processing raw oil, or crude oil, involves a series of separation processes primarily based on boiling points to create various petroleum products. Here's a breakdown of the process:
1. Heating and Distillation:
-
The initial step involves heating the crude oil in a furnace to extremely high temperatures (typically between 700 and 1112 degrees Fahrenheit or 370 and 600 degrees Celsius). This vaporizes most of the hydrocarbons present.
-
The resulting hot vapors and liquids are then channeled into a distillation column or fractionating tower. These towers are designed with a temperature gradient: hot at the bottom and cooler at the top.
2. Separation by Boiling Point:
-
As the hot vapors rise through the distillation column, they cool. Different hydrocarbons condense back into liquids at different temperatures based on their boiling points.
-
Heavier, larger hydrocarbons with high boiling points (like asphalt and lubricating oils) condense lower in the column where it's hotter. Lighter, smaller hydrocarbons with low boiling points (like gasoline, butane, and propane) condense higher in the column where it's cooler.
3. Collection of Fractions:
-
At various levels within the distillation column, trays or outlets are positioned to collect these condensed liquid fractions.
-
The different fractions, ranging from gases at the top to heavy residues at the bottom, are then drawn off. These fractions are commonly known as "cuts" and include:
- Gases: Propane, butane
- Naphtha: A key component of gasoline
- Kerosene: Used in jet fuel and lighting
- Diesel fuel and Gas Oil: Fuels for diesel engines and heating oil
- Lubricating Oil: Used for lubrication purposes
- Residue: Asphalt, tar, and heavier components
4. Further Processing (Optional):
- The fractions obtained from atmospheric distillation can undergo further processing to improve their quality or increase the yield of valuable products like gasoline. This often includes processes like:
- Cracking: Breaking down large hydrocarbon molecules into smaller, more desirable ones (like gasoline). This can be done thermally (using heat) or catalytically (using catalysts).
- Reforming: Rearranging the structure of hydrocarbon molecules to improve their octane rating for gasoline.
- Alkylation: Combining small hydrocarbon molecules into larger ones suitable for gasoline blending.
- Treating: Removing impurities like sulfur and nitrogen compounds.
5. Vacuum Distillation (For Heavy Residues):
- For the heavy residues that remain after atmospheric distillation, a vacuum distillation unit may be used. This process lowers the pressure, which reduces the boiling points of the remaining components, allowing them to be separated without excessive heating that could cause decomposition. Vacuum distillation recovers valuable lubricating oils and waxes.
Summary:
In essence, processing raw oil involves heating it to separate its components based on their boiling points through distillation. The resulting fractions are then further processed and refined to produce a wide array of petroleum products used in fuels, plastics, and other industries.
