One of the most important requirements to liquid – solid mixing processes is prevention of sedimentation of solid particles on the tank bottom. Therefore, one of the main tasks of a designer is to provide Just Suspension Speed (JSS) that is the minimum rotational velocity of the impeller at which there are no stagnant zones at the bottom.

Problem description:

A liquid – solid mixing process is carried out in a cylindrical, baffled tank with an elliptical bottom. The parameters of the mixing system are as follows:

Initial data:

  • Tank Elliptical bottom
  • Inside diameter = 2000 mm;
  • Total tank height = 2395 mm;
  • Level of media = 2236 mm;

Baffles:

  1. 3 radial flat baffles with the following parameters:
  2. Width = 150 mm;
  3. Length = 1938 mm;
  4. Distance from bottom = 457 mm.
  5. Angle to radius = 0 deg.

Impeller:

  • A downward pumping Pitched Paddle impeller with 4 blades inclined at 45°
  • Width of blade = 140 mm
  • Tip diameter = 1000 mm;
  • Distance from bottom = 457 mm.
  • Rotational speed = JSS, rpm
  • Power of drive = 7500 W

Properties of the media:

  • Liquid phase: Water – Density = 1000 kg/m3; Viscosity = 1 cP
  • Solid phase: Sand with density of about 2630 kg/m3 
  • The particle size: Average = 180 microns; Largest = 210 microns;
  • Concentration of the solid phase is 250 kg/m3
  • Position of outlet – height = 0 mm

NOTE: Change the density and viscosity input data by VisiMix recommended.

VisiMix Turbulent for mathematical modeling of turbulent mixing in reactor with 2-stage Lightnin impeller.

Problem description:

You will obtain some general data on your mixing equipment, which will enable you to evaluate the general suitability of your equipment, compare different designs, etc. These parameters are used as basic data for calculations of other mixing problems.

Initial data

Tank Flat bottom:

  • Inside diameter = 3000 mm
  • Total volume = 35 cub.m
  • Volume of media = 30 cub.m

Baffle (Flat, attached to the tank wall):

  • Number = 4
  • Width = 300 mm;
  • Length = 4200 mm;
  • Distance from bottom = 0 mm.
  • Angle to radius = 0 deg.

Impeller:

  • 2-stage Lightnin A310
  • Tip diameter = 1300 mm
  • Distance between stages = 2000 mm
  • Distance from bottom = 375 mm.
  • Rotational speed = 80 rpm
  • Power of drive = 10 kW

Media properties:

  • Type of media = Newtonian
  • Density = 1100 kg/cub. m
  • Dynamic viscosity = 4.5 cP

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Test 4 – Liquid – solid mixing. defining jss (just suspension speed)

One of the most important requirements to liquid – solid mixing processes is prevention of sedimentation of solid particles on the tank bottom. Therefore, one of the main tasks of a designer is to provide Just Suspension Speed (JSS) that is the minimum rotational velocity of the impeller at which there are no stagnant zones at the bottom.

Problem description:

A liquid – solid mixing process is carried out in a cylindrical, baffled tank with an elliptical bottom. The parameters of the mixing system are as follows:

Initial data:

  • Tank Elliptical bottom
  • Inside diameter = 2000 mm;
  • Total tank height = 2395 mm;
  • Level of media = 2236 mm;

Baffles:

  1. 3 radial flat baffles with the following parameters:
  2. Width = 150 mm;
  3. Length = 1938 mm;
  4. Distance from bottom = 457 mm.
  5. Angle to radius = 0 deg.

Impeller:

  • A downward pumping Pitched Paddle impeller with 4 blades inclined at 45°
  • Width of blade = 140 mm
  • Tip diameter = 1000 mm;
  • Distance from bottom = 457 mm.
  • Rotational speed = JSS, rpm
  • Power of drive = 7500 W

Properties of the media:

  • Liquid phase: Water – Density = 1000 kg/m3; Viscosity = 1 cP
  • Solid phase: Sand with density of about 2630 kg/m3 
  • The particle size: Average = 180 microns; Largest = 210 microns;
  • Concentration of the solid phase is 250 kg/m3
  • Position of outlet – height = 0 mm

NOTE: Change the density and viscosity input data by VisiMix recommended.

What is the Maximum degree of non-uniformity Axial? %

What is the Maximum degree of non-uniformity Radial? %

What is the Maximum energy of collisions? e-11 J

What is the Frequency of collisions of maximum energy? 1/S

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