OXIDIZED BITUMEN / BLOWN BITUMEN

The properties of BITUMEN can be modified by air blowing in batch processes.

The Vacuum bottom (VB) in liquid form by BLENDING BITUMEN and BLOWING BITUMEN with a petroleum distillate fraction is customary and is generally accomplished in tanks equipped with coils for air agitation or with a mechanical stirrer or a vortex mixer. Air is heated up to 150–250°C and introduced at the bottom of a blowing production tower. It then migrates through the BITUMEN to the top of the blowing production tower. The chemical reactions result in bitumen with a different mixture of molecular structures. Catalysts can influence this process.

The producing operation of producing OXIDIZED BITUMEN mainly includes tank loading different steps, BITUMEN blowing, condenser external gases and packing. So in the beginning the loose BITUMEN shipped to the plant by tanker is transferred to the raw material store tanker.

In order to transfer the BITUMEN easily to the blowing tower the burner is contrived at the bottom of the store tanker to heat them. It is necessary to say that if the blowing towers are empty, hot BITUMEN can be uploaded directly to them and blowing operation start.

Since the volume of BITUMEN increases as a result of blowing and it may overflow, the blowing tower is filled up to 70 %.
Air injection is usually done when the temperature of material reach to 190-230 °C.

For gradual heating and also pipes filling with the air is entered from the top of the tower and at the bottom the BITUMEN dispread monotonously in phase via nozzel then oxidation is done accordingly and the light molecule, volatile gases and steam are emitted from the top of the tower.

Blowing operation is done in temperature range 215-290°C but the suitable temperature is between 265 to 270°C. The needed heat is provided by burner contrived at the bottom of the tower. The BITUMEN reaction is calorific so in order to prevent the explosion danger resulted from temperature increasing, the temperature can be controlled by water injection, burner extinguisher and air amount reducing.

Blowing end point is usually signified by sampling from tower and BITUMEN properties testing. The blowing operation stops when OXIDIZED BITUMEN reaches to specified properties. After this in order to fix the final point and depolymerization BITUMEN got in high temperature. It is necessary to be transferred to store after packing and presented to sale.

BLOWNED BITUMEN (OXYDE BITUMEN) has more and stronger molecular interactions than the original formula of BITUMEN and is therefore more cohesive. Blowing causes the softening point to increase and the penetration to decrease. However, the increase in softening point is usually more than the decrease in penetration. This means that blowing reduces the temperature susceptibility of bitumen. The effectiveness of blowing depends largely on the original bitumen (i.e. the original mixture of molecular structures).

It is necessary to say that the produced gas and steam entered the condansor through the pipe fixed at the top of the blowing tower. In this stage the bad smelling gases and oily and volatile parts are separated from then transfer to sewage accompanied with water. Other unseparated gas parts is emitted from top of the condenser then transfer to furnace and burned there. After cooling the blowing oven and reaching them to 150-160°C, all the content of blowing oven which is hard BITUMEN is able to be loaded and packed. Because of the liquid height in blowing tower, OXIDIZED BITUMEN is transferred by specific gravity and there is no need to use pump.

Packing is done in 20Kg & 25 kg carton Box, 20Kg & 25kg Meltable polyamide bags, 20Kg, 25 kg and 40Kg kraft Bags, 20Kg, 25Kg & 40Kg Blocks & keg and 20Kg, 25Kg drums. For fast operation (preventing from cooling & hardening) in every section several taps are fixed so that it can fill specific Packings with BLOWN BITUMEN (OXIDISED BITUMEN) in same time.