Production of bitumen emulsions

Bitumen (usually 80/100 or 60/70 grade), water, emulsifier, chemicals used for the water solubility of the emulsifier, stabilisers and particular oils in a small proportion and solvents are used as raw materials. 

The bitumen is heated at a suitable temperature (110°C-140°C), so as to acquire low viscosity, and is pumped to a colloid mill. The emulsifier, the acid, calcium chlorite or any other water-soluble additives are added to the heated water (normally less than 85 C), and all lead to the colloid mill. Other additives such as solvent or polymer in liquid form are also added to the colloid mill. 

The high-speed mill (up to 6000 revolutions per minute) consists of a conic rotor and its respective stator. The gap between rotor and stator is adjustable and is normally approximately 0.25-0.50 mm. Any variation of the gap affects the sizes of the bitumen globules (particles) and, hence, the quality of the bitumen emulsion. 

The bitumen and the aqueous solution of the emulsifier and other additives as they enter the colloid mill are subjected to high shear stresses, which divide the bitumen into microscopic particles (0.5 to 0.015 mm in diameter). These particles, because of the presence of the emulsifier, are uniformly charged to the same polarity. The produced bitumen emulsion, having a temperature of approximately 80°C-90°C, is pumped into storage tanks to cool down. 

Apart from for the continuous flow production units, there are also batch production units. In this case, the predetermined proportions of water, emulsifier and all the other chemicals for each batch are mixed with water in a separate tank before the aqueous solution is pumped into the colloid mill. The hourly output of this system is always lower than the output of the continuous flow system. 

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