What is Oxidized Bitumen?
Oxidized Bitumen or Blown bitumen grades are produced by passing air through the penetration grades. This process gives the bitumen more rubbery properties than its original formula and they are simply harder bitumen. Hard bitumen under controlled temperature conditions is widely used as an anti-slip layer compound in the piling industry, for the manufacture of roofing felts, the roofing and waterproofing industries, for sound dampening felts and under carriage sealant in the automotive industry, electric cable joint protection, joint filling compound, sealant compound and many others. Also used in sealing saw cuts and joints where expected movements are minimum. It is also used in the manufacturing of bituminous marine mastic for the oil & gas pipeline joints.
The most popular grades are; grades 95/25, 85/25, 90/40, and 115/15. We are also capable of producing other grades of Oxidized bitumen upon request by our customers. Oxidized Bitumen high softening temperatures qualify them as the excellent sealant for prevention from bleeding in high-temperature applications. Blown Grade Bitumen shall be broken up into small pieces (for the blown grade in molded cake form) and heated slowly to the application temperature of 220ºC to 230ºC. Oxidized Bitumen is predominantly used in the piling industry as an anti-slip compound for the manufacture of undercarriage sealants in the automobile industry. It is also used as a sealant compound, as a joint filling compound apart from being used in the manufacture of roofing felts and sound dampening felts. Further, Oxidized Bitumen is used in the manufacture of bituminous marine mastic, which is required for the oil and gas pipeline joints. This Oxidized Bitumen is available in different grades like 95/25, 85/25, 75/25, 90/40 and 115/15. Oxidized is also capable of producing other grades of Oxidized Bitumen according to the specifications of individual clients
Some of the major advantages of Oxidized Bitumen are that it is completely water resistant, highly flexible and durable. Further, it is chemically very stable. Oxidized bitumen is a very flexible compound that is not only chemically stable but also a very durable compound apart from being completely water resistant. Lastly, Oxidized Bitumen has some very prominent technical advantages that make it a very sought after compound in various applications.
How to produce Oxidized Bitumen?
1. Bitumen heating to 230-270 °C
2. Transferring melted bitumen to blowing towers
3. Blowing air to bitumen
4. Cooling melted bitumen with water
The procedures of producing bitumen are as follows:
1. Continuous blowing procedure
2. Discontinuous blowing procedure
These two procedures are done by other two procedures named catalysis and anti-catalysis. Catalysis means adding some chemical material during the process In order to decrease blowing reaction time.
For the following reasons:
• Ease and simplicity in changing blowing condition and have the production with different grades as a result.
• Ease in generating the unit.
• Ease in technology and also low expense in investment.
The discontinuous producing procedure is chosen.
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.
The admixture of air and the volume of blowing air is two important variants in blowing process. In bitumen producing the 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 severe and uncontrollable which lead to the explosion in the tower.
The long time stay of bitumen in the 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 endamage 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 the product should be kept 150- 165 °C in order to have loading and packing capability.
The production process is as follows:
The producing operation of oxidized bitumen mainly includes tank loading different steps, bitumen blowing, condenser external gasses 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 nozzle then oxidation is done accordingly and the light molecule, volatile gasses, and steam are emitted from the top of the tower.
Blowing operation is done in the 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.
It is necessary to say that the produced gas and steam entered the condenser through the pipe fixed at the top of the blowing tower. In this stage, the bad smelling gasses and oily and volatile parts are separated from then transfer to sewage accompanied with water. Other unseparated gas parts are emitted from the top of the condenser then transfer to the 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 the pump. Packing is done in two sections and in 220-liter drum and 35 kg carton. For fast operation (preventing from cooling & hardening) in every section, several taps are fixed so that it can fill specific drum and carton with bitumen at the same time.
Application of oxidized bitumen:
Oxidized Bitumen has a wide variety of industrial applications
• As a bonding bitumen for roofing sheet membranes.
• As a hot-applied waterproofing layer.
• Carpet tile manufacture.
• As a raw material for liquid bitumen coatings.
• For the production of bituminous paint, mastic.
• For rust proof pipe coatings.
• Used as an anti-slip layer compound in the piling industry.
• Used for production of roofing and sound dampening felts, Used as under carriage sealant in the automobile industry, electric cable joint protection, joint filling compound, sealant compound and much more in our day to day life.