Oxidized Asphalt is a solid or semi-black solid material and gradually liquid when heated, oxidized asphalt is predominant content bitumen, asphalten , malten (oils) and aromatic resins. The oxidized asphalt or blown asphalt is producing in different softening point and penetration like as 115/15 90/40 85/25 85/25 90/15 95/25 75/25 150/5 105/30
How to produce Oxidized Asphalt?
- Bitumen heating to 265-270 °C
- Transferring melted bitumen to blowing towers
- Blowing air to bitumen
- Cooling melted bitumen with water
The procedures of producing Asphalt are as follows:
- Continuous blowing procedure
- Discontinuous blowing procedure
These two procedures are done by other two procedures named catalysis and anticatalysis. Catalysis means adding some chemical material during the process In order to decrease blowing reaction time.
These are advantages of the discontinuous producing procedure:
- Ease and simplicity in changing blowing condition and have production with different grades as a result.
- Ease in generating the unit.
- Ease in technology and also low expense in investment.
Technical point and operating conditions are as follows:
- The blowing should be done from the bottom of blowing tanker. The reaction between bitumen and air is calorific. If the heat produced during the mixture is high, the heat of reaction is controlled by water injection.
- Admixture of air and the volume of blowing air are two important variants in blowing process. In bitumen producing plant, bitumen 60/70 is usually got by blowing. In this case for making bitumen 90/15 or 85/25 distilled used oil or crude oil should be injected to the product according to the volume 20-25 % otherwise the fragility in bitumen lead to inferior production.
- Increasing the heating temperature, air injection amount, time and tower pressure increase the speed of production process reaction. The suitable temperature for production operation is 265-270 °C which should be controlled not to be ascended since in high temperature and in 288 °C intensity of reaction becomes more sever and incontrollable which lead to explosion in tower.
- The long time stay of bitumen in tower in any condition is not in favor of system and should be delivered to drum or empty tanker after being ready.
- If the liquid surface in blowing tower is low, not more than particular limit should be added to the system for the extra air gather in empty parts and lead to ignition nearly. And if the temperature is kept high, the inside heat of tower ascend fats and this issue cause inside explosion and damage the system.
- Blowing tower is filled up to 70%. Air injection is done in 190-232°C. The final point of blowing is specified by sampling and testing of bitumen properties. Finally the temperature of product should be kept 150- 165 °C in order to have loading and packing capability.