8.3. Production of Bitumen from Petroleum

The initial step in the production of bitumen is the fractional distillation of crude oil in a refinery. The process includes:

• Preheating of Crude Oil: Crude oil is first heated to around 400°C. • Atmospheric Distillation: The heated crude enters a distillation column where lighter hydrocarbons (like gasoline, kerosene, diesel) are separated by their boiling points. • Vacuum Distillation: The residue from atmospheric distillation, known as long residue, is further distilled under vacuum to avoid thermal cracking. This separates lubricating oils and leaves behind a heavy residue known as short residue or vacuum residue, which becomes feedstock for bitumen production.

The production of bitumen starts with crude oil distillation. First, crude oil is heated to about 400°C to separate various hydrocarbon compounds based on their boiling points. This process is called atmospheric distillation, where lighter components like gasoline and diesel are extracted. Next, the heavier leftover liquid, known as long residue, undergoes vacuum distillation. By applying a vacuum, the temperature is lowered to prevent thermal cracking of sensitive hydrocarbons, resulting in a heavier residue known as the short residue. This short residue is essential for producing bitumen.

Think of the distillation process like cooking pasta. When you boil water and add pasta, it cooks differently based on its size and thickness. The thinner spaghetti cooks faster and rises to the top when it's ready, similar to how lighter hydrocarbons separate first. The thicker pasta takes longer and requires a lower temperature to cook properly without falling apart, just like how vacuum distillation separates heavier oils at lower temperatures.

The vacuum residue may undergo air blowing to enhance specific properties of bitumen. In this process:

• Hot air (200–300°C) is blown through the residue. • The oxygen in the air reacts with the hydrocarbons, increasing viscosity and softening point. This process produces oxidized bitumen, which has higher softening points and is more suitable for industrial applications such as roofing and pipe coating.

After obtaining the vacuum residue, the next step is to enhance its properties through oxidation. Hot air at temperatures ranging from 200°C to 300°C is blown into the residue. During this process, the oxygen in the air chemically reacts with the hydrocarbons in the residue. This reaction increases the viscosity and softening point of the bitumen, producing oxidized bitumen. This type of bitumen is ideal for various industrial applications, especially in situations that require a stronger binding agent, such as roofing materials and pipe coatings.

Consider how cooking eggs changes their texture. When you add air and heat to egg whites, they become fluffy and thick, much like how blowing hot air into the vacuum residue changes its properties. Just like fluffy eggs are better for certain recipes, oxidized bitumen has traits that make it more effective for specific industrial tasks.

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