The production process of bitumen emulsions is inextricably connected with bitumen emulsification. Currently there are several approaches to the production of this material: mechanical, acoustic, chemical and aeration.
Mechanical method means grinding of initial bitumen by compression, impact, stretching, friction and other external forces. With the acoustic method the properties of ultrasonic waves are used for bitumen milling. Chemical method causes bitumen breaking by the reaction between injected substances (acids) and binder. Interfacial tension is reduced and further simple mixing results in emulsification.
Emulsion facilities are usually equipped with:
- a bitumen-emulsion production unit;
- bitumen melting plant for bitumen dehydration and heating;
- a soap boiling tank;
- tanks for caustic soda preparation;
- agitator for preparation of emulsifier water solution;
- emulsifier feeding tanks;
- water softening unit;
- portioning units.
To eliminate the risk of foaming and ejection of the mix out of the emulsifying unit, the temperatures of bitumen and emulsifier solution are set so as not to exceed 200ºС total. The temperature of bitumen is kept unchanged, while the temperature of the product at the outlet of the emulsifying unit must not exceed 90ºС.
The process of bitumen emulsion preparation starts from the supply of emulsifier solution into the unit, followed by bitumen. If using acoustic dispersers, the duration of mixing is 5 to 7 minutes after supplying the full batch of bitumen, and in case of a vane mixer it takes 5 to 8 minutes after supplying the solution when inverse emulsions are made. If slotted dispersers are use, the mixing process is continuous.