Problem description:

In this fermentation reactor, with 2-stage pitch paddle, the air is injected under the bottom impeller. For this process, the oxygen dissolution rate and the maximum shear stress are, among others, important mixing parameters.

Initial data

• Tank Elliptical bottom
• Inside diameter = 1800 mm
• Total volume = 6000 L
• Volume of media = 5500 L

Baffle (flat type, attached at a distance from the wall)

• Number = 4
• Width = 160 mm;
• Length = 2000 mm;
• Distance from bottom = 450 mm.
• Distance from wall = 50 mm
• Angle to radius = 0 deg.

Impeller (Pitched Paddle):

• Tip diameter = 900 mm
• Impellers number = 2
• Distance between stages = 1100
• Number of blades = 4
• Pitch angle = 45 deg.
• Width of blade = 140 mm
• Distance from bottom = 400 mm.
• Rotational speed = 75 rpm
• Motor power = 7500 W

Properties of the media:

• Newtonian
• Average Density = 1100 kg/cub.m;
• Dynamic viscosity = 15 cP

Data on air injection and physical properties

• Surface tension = 0.07 N/m
• Volume flow rate = 0.1 cub.m/s 
• Operating conditions = fixed liquid level
• Molecular diffusivity = 1.8e-9 sq.m/s
• Mass solubility = 0.01 kg/cub.m
• Mass gas concentration in solution = 0.004 kg/cub.m