There are four different ways to produce bitumen from crude oil. Bitumen production processes vary depending on feed conditions and product specifications.
Distillation (Straight Run), Air Blowing , Blending , and Solvent De-asphalting are bitumen production methods.
In this article, we are going to introduce bitumen production methods to you.
1. Distillation (Straight Run)
Bitumen is primarily obtained by the distillation of crude oil. Atmospheric and vacuum distillation towers are used in this process.
First, crude oil is heated to a temperature of 350 degrees Celsius. As the temperature rises, light components with low boiling points are removed from the upper parts of the atmospheric distillation tower.
The residual of the end of the tower is known as Atmospheric Residue. To remove the last trace of the light fractions and also to prevent the thermal cracking of the molecules , the atmospheric residue is transferred into a vacuum distillation tower.
In vacuum conditions, the pressure is reduced and this causes the boiling temperature to decrease and separate any light component.
The residue of this tower is called the vacuum bottom. Vacuum bottom is usually a hard material that can be used directly. For this reason, it is called straight run bitumen.
But sometimes the bitumen coming out of the vacuum tower does not have proper physical properties and its properties must be modified., which is called straight-run bitumen.
2. Air Blowing
The main way to produce bitumen is the air blowing method. In this process, the air is blown into bitumen feedstock with a certain flow rate in bitumen at a high temperature (280°C on average).
The main purpose of blowing air is to harden the bitumen. Air blowing also causes changes in some physical properties of the final products.
Infinity Galaxy, as an international bitumen supplier and bitumen analyst, has prepared the following infographic for you to learn more about the air blowing process. It is recommended to read the following infographic before reading further.
Blowing air is done in two ways, Air Rectification and Fully Air.
2.1 Air Rectification
In the air rectification method, the air is blown to a mild degree. Usually, this method is used to adjust the physical properties of bitumen, such as reducing penetration and increasing viscosity.
Air rectification is performed in two ways : Batch Blowing and Continuous Blowing.
The difference between the two batch and continuous methods is in the way of blowing air.
In the continuous process, the vacuum bottom enters the blowing tower with a constant flow rate. After blowing the air, the bitumen is continuously discharged from the air blowing tower.
Meanwhile, in the batch blowing method, the blowing tower is filled with a certain volume of feedstock. Blowing air occurs under certain conditions. When the product reaches the desired specifications, the tower is discharged.
In a continuous process, more bitumen is produced per unit of time than in the batch method.
2.2 Fully Air Blowing
In the fully air blowing method, also known as oxidation, more air is passed through the feedstock than in the air rectification method. By increasing oxidation, final products with different penetration and viscosity is produced.
In this process, by controlling the reaction variables, oxidized bitumen with specific physical and chemical properties can be prepared.
For example, chemical reactions lead to an increase in the apparent molecular weight and polarity of bitumen which can affect the adhesion property of bitumen in bonding the aggregates to each other. This bitumen can be widely used in roofing applications.
Bitumen is produced to meet specifications either directly in the refining process, or by blending with bitumen having different physical properties.
In this method, specific ratios of bitumen with higher viscosity are mixed with bitumen of lower viscosity to produce bitumen with specific characteristics.
4. Solvent De-asphalting
Another method of bitumen production is to separate bitumen from crude oil by using propane or butane solvents.
In this method, the vacuum bottom is mixed with propane (butane) and then de-asphaltene oil is extracted from it.
The residual products produced by the solvent de-asphalting unit are asphaltenes and petroleum resins depending on the process used.
It should be noted that the type of crude oil processed and the operational technique used in the de- asphalt unit plays an important role in determining the properties of the produced bitumen.
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