Bitumen Production Process

Bitumen is produced by partial distillation of crude oil. Distillation is usually done in two stages. First, the crude oil is heated to a temperature of 300-350 degrees Celsius and enters the atmospheric distillation column. Lighter parts such as kerosene and gas oil are separated from crude oil at different heights of the column. The heaviest fraction that remains at the bottom of the column is called the heavy residue. The long residue is heated to 350-400°C and fed into a vacuum distillation column. By using reduced pressure, lighter products can be further distilled from the residue because the equivalent temperature (atmospheric temperature) is much higher. If the second distillation is carried out in atmospheric conditions and with an increase in temperature above 400 ° C, thermal decomposition, cracking of the heavy residue occurs. The residue at the end of the column is called short residue and is the raw material for bitumen production. A second distillation, at reduced pressure, may be used to remove excess amounts of more volatile products and create a vacuum residue of the desired consistency. These single-stage and two-stage distilled asphalt fractions are known as straight bitumen because the bitumen is separated from the crude oil while retaining its chemical properties. Different crude oils contain different amounts of vacuum foam and require specific refining techniques to produce the desired straight bitumen. The oxidized bitumen is sent from the bottom of the reactor to the separator, where the bitumen vapors are separated and returned to the reactor, and then the direct bitumen is stored. Since oxidized bitumen is a viscous, semi-solid material, it is difficult to mix it with other materials at ambient temperature. By heating it, oxidized bitumen may become more fluid and can mix aggregates to produce hot pavement materials. Other methods to reduce the viscosity of oxidized bitumen are dispersing its particles in water (emulsified bitumen) or dissolving it in petroleum solvents (cutback bitumen). Volatility of petroleum solvent determines the curing speed of cutback bitumen. Bitumen may be modified by exposure to air while the bitumen is at high temperature. The resulting dehydrogenation and polymerization yields a substance called blown or oxidized bitumen. Blown bitumen shows more flexibility, less brittleness and less sensitivity to weather changes. They are commonly used in roofing applications because the process increases the softening temperature of the asphalt and reduces the infiltration rate. There are different types of bitumen, such as penetrating bitumen, oxidized bitumen 115-15, emulsion bitumen, Gilsonite. Faragam Company is a supplier of Iranian bitumen to the whole world