Liquid Mixing Equipment

Vessel:

  • Vertical cylindrical vessel with a liquid height which is equal to the tank diameter.
  • The vessel top and  bottom may be provided with flat or dished ends.
  • Dished bottom heads can be 2:1 ellipsoidal, torispherical, hemispherical or conical.
  • Nozzles – Agitator mounting, feeding, measurement instruments, manhole, material discharge
  • Design for the operating temperature and pressure conditions.
  • The thickness of the vessel shell and dished ends should be calculated using the relevant pressure vessel design codes.


Baffle:

  • Baffles are installed on agitator vessels to produce a flow pattern conducive to good mixing and to prevent vortex formation.
  • In standard agitation equipment configurations, 4 vertical baffles are provided each of which has a width of 1/10th or 1/12th of the tank diameter.
  • Baffles are generally offset from the vessel wall by a distance equal to 1/3rd to 1/6th width of the baffle.
  • Baffles increase the power consumption of the mixer but in turn improve the process performance.


Draft Tubes:

  • Draft tube is a cylindrical duct slightly larger than the impeller diameter and is positioned around the impeller.
  • Used with axial impellers to direct the suction and discharge flows.
  • The impeller draft tube system acts as a low efficiency axial flow pump.
  • The top to bottom circulation flow is of significance for flow controlled process, suspension of solids and for dispersion of gases.
  • They are particularly useful in tall vessels having high ratio of height to diameter.


Heat Transfer Surfaces:

  • Heat transfer surfaces are provided for applications which require heating or cooling of process.
  • Heat transfer for an agitated vessel is dependent on the following.
  • Overall heat transfer coefficient.
  • Surface area for heat transfer.
  • Temperature difference between the heat transfer fluid and the process fluid.
  • The heat transfer co-efficiencies can be estimated using established corrections.
  • The turbulence created by the action of the impeller improves the heat transfer coefficient.

Impellers

  • Based on the liquid viscosity, impellers can be classified as turbines for low viscosity fluids and close clearance impellers for high viscosity fluids.
  • Depending on the flow patterns developed by the mixing impellers, they are classified as axial flow impellers and radial flow impellers.

Impeller designs may also be classified based on the amount of shear that they produce.

        Axial flow impellers

  • Marine propellers
  • Pitched bade turbines
  • Hydrofoil impellers

      Radial flow impellers

  • Rushton turbine
  • Smith Impeller
  • Open blade turbine
  • Coil or spring impellers

      Low clearance impellers

  • High shear impellers

Related Links

  • Marine Propeller - In a theoretical environment, one full revolution would move the liquid longitudinally a fixed distance depending upon the of inclination of propeller blades…Read more
  • Pitched Blade Turbine – Impeller Diameter – 450 mm to 3000 mm,Hub with even number of blades are mounted at an angle of 10° to 90° with respect to the horizontal…Read more
  • Hydrofoil Impellers - High efficiency impellers designed to maximize fluid flow and minimize shear rate. 3 or 4 tapering twisted blades…Read more
  • Radial Flow Impeller – The impeller blade is parallel to the axis of the impeller,Radial flow impeller discharges flow along the impeller radius…Read more
  • Rushton Turbine - The Rushton turbine is a disk type (six blade turbine) radial flow impeller,The diameter of the disk ranges from 66 to 75 percent of the internal vessel diameter…Read more
  • Open Blade Turbine – In open blade turbine, the blades are directly mounted on the hub…Read more
  • Anchor Impeller – The Low Clearance Impellers:Anchor Impeller and the helical impeller are the two commonly used close clearance impellers…Read more
  • High Shear Impeller – Used for application such as grinding, dispersing pigments and making emulsions…Read more