Types of Mixing Equipment
Mixing equipments are classified based on the type of materials being mixed. The three main classifications of mixing equipment are:
1. Blenders: Mixers for Solid-Solid Blending
Considering the myriad of industrial operations requiring blending of bulk solids, there is a wide range of blender technologies available. Depending on the principle, mechanism of mixing, blenders are classified as follows:
· Tumbler Blenders : Double Cone Blender, V-Blenders, Octagonal Blender
· Convective Blender: Ribbon Blender, Paddle Blender, Vertical Screw Blender
· Fluidization Blenders / Mixers: Plow Mixer, Double Paddle Mixer (Forberg Mixer)
2. Agitators: Mixers for Liquid-Liquid, Liquid Gas Mixing
A variety of process functions like blending miscible liquids, contacting or dispersing immiscible liquids, dispersing a gas in a liquid, heat transfer in agitated liquid, suspension of solids in liquids, etc. are carried out in agitated vessels by rotating impellers. The impellers are classified into two types, axial and radial, depending on the angle that the impeller (also known as agitator) blade makes with the plane of impeller rotation.
· Axial Flow Impellers: The impeller blade makes an angle of less than 90° with the plane of impeller rotation. As a result the locus of flow occurs along the axis of the impeller (parallel to the impeller shaft)
e.g.: Marine Propellers, Pitched Blade Turbine
· Radial Flow Impellers: The impeller blade in radial flow impellers is parallel to the axis of the impeller. As a result, the radial-flow impeller discharges flow along the impeller radius in distinct patterns.
e.g.: Flat Blade Turbine, Paddle, Anchor
3. Heavy Duty Mixers: Mixers for Viscous, Pasty Materials
For high-viscosity materials, the mixing regime changes from one in which turbulence dominates (as in liquid agitators) to one in which viscous drag forces dominate. Moreover, some materials exhibit Non-Newtonian behavior. A non-Newtonian fluid is a fluid whose flow properties are not described by a single constant value of viscosity. Therefore mixing of such material requires special heavy duty mixers. These include:
· Double Arm Mixers
· Planetary Mixers
· Dual and Triple Shaft Mixers
The operation of the mixing equipment may be batch or continuous depending upon the required production capacity, product quality, pre and post mixing equipment, type of mixer, etc.