Bitumen Emulsions Production
Oil based bitumen is widely used in the road construction industry due to its excellent binding properties. Bitumen should be heated up to 100-200⁰С / 212- 392⁰F to make it liquid and only then is it mixed in with other chemical compounds. The ready mixture should be transported and applied only when it is hot. When the bitumen mixture becomes cold, it gets stronger and begins to set-up.
There is another way to get liquid bitumen by using kerosene. When kerosene evaporates, the bitumen mixture begins to solidfy and eventually becomes solid. There had been no alternatives to these methods until bitumen emulsion made a breakthrough in the high-tech road construction market.
The production of bitumen emulsion consists in dispersion of bitumen in water. Sometimes inert additives may be added to this mixture. The strength of the pavement is provided by water evaporation and subsidence of bitumen paste. This technology is safe, because it significantly to reduces the risk of harmful vapours, burns, and fires.
What does term “Bitumen Emulsion” mean?
Emulsion is a finely-divided system consisting of two or more liquids. For example, in the ‘oil and water’ system, oil is a disperse phase, and water is a constant one. Therefore, bitumen emulsion is produced as a result of mixing. But, when the mixing process is not performed, the mixture becomes broken down. Special substances such as emulsifiers are added to the mixture in order to prevent such consequences. They allow the emulsion to maintain stability and not to fall into separate phases. If the bitumen emulsions contain from 40% to 80% of bitumen, they look like a sour brown color (diameter of bitumen droplets ranges from 0.1 to 20 microns).
The GlobeCore UBV units are designed for bitumen emulsion production. They operate on the basis of a colloid mill which is supplied with a mixture of warmed up bitumen. The special claws on the rotor of the colloid mill are designed to provide increased turbulence which improves the bitumen grinding process.
There is also bitumen emulsion equipment that has an uninterrupted mode of operation. First, components such as additives, hot water, and emulsifier are metered in a special container and mixed up with bitumen to make a water phase.
Then, the colloid mill is supplied with this mixture. Such equipment can also be equipped with special pumps, required to meter the components of a disperse system and to warm up water. There is no need in using container-type tanks while mixing the components. Such additives such as SBS-modified bitumen and latex are mostly used in bitumen emulsion production. The latex metering should be performed with a help of special equipment since it can form clots in the pipes and pumps. Bitumen should be divided into separate droplets to get a finely-divided system. But, there are such problems as: (1) viscosity; (2) surface tension; and (3) internal cohesion of bitumen. Additionally, some separated droplets can merge again. Mechanical energy should be applied to get lots of small stable particles. And no less efforts should be taken to prevent a reverse merging process.
A wide range of factors should be taken into consideration to achieve a desirable size of bitumen droplet. consider the following:
(2) type and concentration of emulsifier;
(3) time, spent in the colloid mill;
(4) gap between the stator and the rotor; and
(5) speed of the driving motor.