Blown Bitumen

If in the oil refining process in the vacuum distillation tower, the separation of light cuts from heavy cuts at the end of the tower is not done completely, the product at the end of the vacuum distillation tower (Vacuum Bottom or V.B) is sent as feed to the aeration unit for bitumen production.

Bitumen was produced for the first time in 1890 from the reaction of this product with oxygen. And after that, a lot of research was done on process variables, device design and control of chemical reactions. V.B aeration is a process in which the residue of the vacuum distillation tower is exposed to air. As a result of this contact, V.B is hardened and its thermal sensitivity decreases.

The amount of modification and improvement of bitumen properties that takes place in this process depends on the type of feed and temperature variables, feed viscosity, feed aeration time and feed retention, aeration ratio and type of equipment. Blown bitumen is used in asphalt mixes, waterproofing layers, asphalt blocks, and more.

The aeration process is the result of dehydrogenation, polymerization and oxidation. In this process, some of the oils turn into resin and some of the resin turns into asphaltene. These changes result in a colloidal and rubbery structure that is characteristic of blown bitumen.

Only 5 to 25 percent of combined oxygen remains in the form of bonding (reacted) in blown bitumen, and the rest is released as water vapor, carbon dioxide, sulfur dioxide, etc. The amount of oxygen in the product increases by increasing the amount of feed aromatics, increasing the amount of aeration and decreasing the temperature of the process. The aeration process is exothermic, so it is necessary to control the temperature of this process and adjust the ratio of air to feed.

The aeration process can be done continuously or discontinuously.

Blown bitumens are divided into different classifications according to international standards:

The main bitumen products are in the following two categories:


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