Whereas on ‘Agitators’ there is enormous information available for Design and Design Codes have also been standardized and are noted in Codes and Standards’. There is hardly any reliable information on Jet Mixer in the Literature. Hitherto, the best summary written on these Mixers could be found in a Chapter 9, on “Jet Mixing” by B.K. Revill, ICI Chemicals and Polymers Ltd, Runcorn, Cheshire, in
Mixing in the Process Industries by N. Harnby, M.F. Edwards
and A.W. Nienow, Second Edition, 1992.
Concept of Jet Mixers appears very simple. However, unless one has good understanding of ‘Fluid Dynamics’ and perhaps ability to visualise flow patterns in three dimensions it is difficult even to attempt the design and expect good mixing results.
In Jet mixing, a fast-moving stream of liquid, the Jet is injected into a slow-moving or stationary liquid, the bulk. The velocity difference between the jet and bulk liquid creates a mixing layer at the jet boundary. This mixing layer grows in the direction of the jet flow, entraining and mixing bulk liquid into the jet.
Jet mixing in tanks is usually used either to blend a fresh feed in with the contents of a tank or to obtain a homogeneous mixture within the tank. Batch or Continuous operation is possible and a side entry (i.e. through the tank wall) or an axial jet (i.e. along the axis of the tank) may be used. The Jet is positioned either near the tank floor pointing towards the liquid surface or near the liquid surface pointing towards the tank floor. Jet Mixers are designed specific. The Jet is designed to create appropriate velocities. It is then positioned in the tank at a right position and with a correct angle so that appropriate swirl and vortex is created for the bulk mixing. In some situation more than one jet are required.
Industrial Application of Jet Mixing are :
- Homogenization of Hydrocyclone in storage tanks.
- Mixing in a ‘Bio Reactor’ and Fermentation applications.
- Mixing of Chemicals in Effluent Treatment application.
- Homogenization of low viscosity chemical tanks in various chemical
Jets are useful on their own as carefully designed low pressure drop Jets or they may be used in combination with other design such as ‘Eductors’ or ‘Static Mixers’. Jets with ‘Eductors’ are used as Eductor Jets and as ‘Aerators’.
The Eductor principle whereby high velocity of one fluid creates suction and attracts the second liquid towards itself to effect micro mixing is combined with the JET mixing which is essentially bulk mixing to produce Eductor JETS. Eductor Jets are also effectively used to doze a second liquid into the bulk without an extra pump.
JETS AS AERATORS
JETS with Ejectors and with or without Static Mixers have been effectively used in several gas line applications. Especially when the viscosities are moderate or low such aeration parameters are extremely operated and maintenance free.
JETS WITH STATIC MIXER
Where intensive mixing is required STATIC MIXERS are used together with JETS to produce the required effect.
MAMKO have thorough knowledge of design and application of various types of JETS. They make JETS available in Carbon Steel, Stainless Steel, Polypropylene or PVC.