Bitumen Emulsion Production. Continuous bitumen machines can be of two types: rotary or piston. This division indicates not only the nature of the forces causing emulsification (inertia in the former type of machines and piston pressure in the latter), but also on the design of the machines: a rotor and a stator in the first case and a closed emulsification chamber in the second. Rotary machines are most commonly used in road construction material production. Plunger homogenizers found wide use in food production.
The design of the rotary machines is simpler, with a lot less friction parts, and they are better suited for the use in road construction.
To create the best conditions of emulsification, the surfaces of the rotor and the stator come in various shapes (conical, cylindrical, parabolic, irregular etc). Irregular and scalloped surfaces also cause shear forces promoting dispersion. Elliptical shape creates a varying cross section of the gap between the rotor and the stator, maintaining liquid pressure. In case of a conical form, depending on the cone angle, the forces pushing the liquids through the gap change. Conical and cylindrical shapes are simple to manufacture.
Beside single rotor, there are homogenizers which use several rotor disks on the same shaft, pushing the emulsified liquids consecutively through all gaps. This emulsification is referred to as multistage emulsification, and in practice it is often used to introduce additional components into the emulsion.
To increase production capacity of single rotor homogenizers, they often come with several gaps and simultaneous emulsification in all active zones.
Plunger batch machines are only used in road construction as mixers for preparation of highly concentrated water in oil and oil in water emulsions. In terms of design, agitators can be equipped with vanes or vane screws. Multipass vane agitators are used for preparation of concentrated water-in-oil emulsions.