Line mixers-dispersers are used in industrial production of bitumen emulsions for waterproofing.
What is a disperser?
A disperser is a continuous colloid mill. In this mill, bitumen emulsion is prepared in a rotor-stator mixer with a gap 0.2-0.6 mm between the moving part and the housing. The rotor breaks and tears particles and droplets of bitumen and evenly distributes them in aqueous emulsifier solution.
There are also plunger dispersers, but rotary dispersers are simpler in design and are more durable.
Structural elements of the disperser:
- heated tank for bitumen;
- water dispenser connected to pipe or tank;
- emulsifier dispensers for bitumen emulsion (bitumen mill);
- probe to measure pH;
- feed pumps;
- mixer-homogenizer;
- output pipe or tank for storage of bitumen emulsion.
How does a disperser colloid mill work?
Bitumen is continuously heated to operating temperature (80°C and higher) in a tank by a bitumen heater, and water is heated to 60-80 ° C. Further:
- to dispersing chamber:
– where a chemical reaction takes place between fatty acid and alkali or hydrochloric acid (parts of anionic or cationic emulsifiers);
– the resulting reagents immediately dissolve in water;
- mixer-homogenizer breaks bitumen into droplets to form the water phase which is stabilized by the emulsifier;
- The mixture is pumped into a tank, it is cooled and poured into transport containers. Due to heat exchangers, the generated heat is sent to heat water.
The formula for bitumen emulsion depends on future application and the type of bitumen used. Emulsion component percentages are: 50-60% bitumen, 1-3% emulsifier and the rest is water. Different types of bitumen emulsion are used for road, construction, roofing, waterproofing of foundation and building blocks. Also, bitumen emulsions are divided according to speed of evaporation and separation of water – 5, 10 minutes and more than 10 minutes.
Advantages of continuous industrial dispersers:
- automation and remote control, no harmful effects of chemicals;
- mass production of emulsions and implementation of quick changeover to a different type;
- increased productivity compared to batch units;
- low operating costs of bitumen mill.