Distillation Residue 

The distillation residue, also known as the bottom product, is a heavy, viscous, dark-colored material that remains at the bottom of the crude oil distillation column. It consists of high-boiling hydrocarbons and is typically used as feedstock for advanced refinery units or for producing various products such as bitumen, fuel oil, vacuum bottoms, and petroleum coke.

Distillation residue is mainly classified into two types: Atmospheric Residue and Vacuum Residue.

1. Types of Distillation Residue

1-1. Atmospheric Residue

Also referred to as fuel oil or mazut in some cases, this is the heaviest fraction remaining after crude oil distillation at atmospheric pressure.

Production Process: Crude oil is heated under ambient pressure and lighter fractions such as gases, gasoline, and kerosene are separated. The thick, sticky material left at the bottom is the atmospheric residue.

Characteristics: Dark color, high viscosity, high density, very high boiling point.

Applications:

• Fuel for industrial boilers and power plants
• Feedstock for further processing units such as vacuum distillation towers or catalytic crackers

1-2. Vacuum Residue (Vacuum Bottom)

This product is obtained from the distillation of atmospheric residue under vacuum conditions.

Production Process: By lowering the pressure inside the tower (creating a vacuum), heavy materials can be separated without excessive heating, preventing thermal cracking.

Characteristics: Very viscous, dark, rich in asphaltenes and heavy metals.

Applications:

• Production of paving bitumen
• Feedstock for coker or hydrocracker units to produce lighter products
• Raw material in manufacturing carbon black or industrial lubricants

2. Physical and Chemical Properties

• Appearance: Viscous liquid or semi-solid
• Color: Dark brown to black
• Density: High (greater than water)
• Viscosity: Very high
• Boiling Point: Very high
• Main Composition: Heavy hydrocarbons, asphaltenes, resins, sulfur compounds, and heavy metals

3. Applications

a) Oil and Petrochemical Industry

• Production of various grades of bitumen for road paving and waterproofing
• Fuel for factories and power plants (mazut)
• Feedstock for cracking units to produce lighter fuels

b) Other Industries

• Production of carbon black for tire manufacturing and inks
• Manufacture of industrial lubricants
• Use in anti-corrosion coatings

4. Packaging and Transportation

• Bulk Transport: In insulated tankers equipped with heating systems
• Storage: In large heated storage tanks
• Small-Volume Packaging: In robust steel or plastic drums

5. Safety and Environmental Considerations

• Flammability: Low, but can ignite at high temperatures
• Inhalation Risks: Heavy vapors; use of personal protective equipment (PPE) is essential
• Environmental Impact: Non-biodegradable and polluting; requires careful waste management

Summary

Distillation residue is an important by-product of crude oil refining, categorized into atmospheric residue and vacuum residue based on process conditions. Due to its heavy hydrocarbon composition and unique physical properties, it has widespread uses — from bitumen, fuel oil, and vacuum bottoms to petroleum coke production, as well as serving as feedstock for advanced refining units. Its applications range from powering furnaces to producing carbon black and protective coatings. Despite its significant economic value, its viscous and pollutant nature requires safe, controlled handling, storage, and transportation.