This document discusses the basic design of agitated vessels. It defines agitation as induced circulatory motion inside a container, while mixing is the random distribution of separate phases. Agitated vessel design considers factors like vessel shape, impeller type/size/placement, flow patterns, baffles, and power requirements. Common impeller types include axial-flow and radial-flow varieties. Baffles are used to prevent vortexes and direct flow. Power correlations can determine agitator power needs based on parameters like pumping number and Reynolds number.

1. Basic Agitated vessel
design
Dipak Babu
seminar

2. Mixing Agitation

3. Basic definitions
 Agitation :
 Induced motion of a
material in a specified
way ,usually in a
circulatory pattern inside
some sort of a container.
 Mixing :
 Random distribution into
and through one another
,of two or more initially
separate phases.

4. A simple example
Gas A Gas B
blending
Sample A Sample B
Same composition = Agitation

5. Rotating drum
Different compositions = Mixing

7.  Blending of two miscible liquids ( ethyl alcohol and water).
 Dissolving solids in liquid ( salt in water).
 liquid-liquid dispersion (dispersion of pigment in solvents ).
 Suspending of fine solid particles in a liquid ( catalytic
hydrogenation of a liquid).
 Agitation of the fluid to increase heat transfer between the
fluid and a coil or jacket in the vessel wall.
 dispersing a gas in a liquid as fine bubbles, such as oxygen from
air in a suspension of microorganisms for fermentation or for
the activated sludge process in waste treatment.
Where is it used….??

8. The basic design
Influencing factors for
achieving a needed amount
of mixture or quality of
mixing :
1) Dimensions of the liquid
content of the vessel.
2) Dimensions and
arrangement of the
impellers , baffles .
http://commons.wikimedia.org/wiki/File:A
gitated_vessel.svg

9.  The vessel shape .
 The type , size , position and speed of the impeller.
 Flow patterns.
 Vortex formation.
 Baffles.
 Power correlations.
Design factors

10. The vessel
Rounded to eliminate
sharp corners or
regions into which
fluid currents would
not penetrate .
Height of fluid =
diameter of the
vessel
http://commons.wikimedia.org/wiki/File
:Agitated_vessel.svg

12. “The impeller”

13. Based on
viscosity
Based on
flow pattern
impellers
Axial – flow
impellers
propellers
High
efficiency
impellers
Radial – flow
impellers
turbines
Types …..!!!

15. Vessel illuminated with a number of
thin light sheets with different colors.
www.bakker.org

16. Pitched blade turbine
Three blade marine propeller Straight blade turbine
Concave blade impeller
Disc turbine

17. Image source : www.fusionfluid.com
Double flight helical
ribbon impeller

18. Impeller location : 1/6 the liquid level from the bottom
Impeller speed : standard speeds are 37, 45, 56, 68, 84, 100, 125, 155, 190, and
320rpm.
Power requirements usually are not great enough to justify the use
of continuously adjustable steam turbine drives.
Impeller size : the ratio of diameters of impeller and vessel falls in the range,
d/D,=0.3-0.6.
Another rule is that a second impeller is needed when the liquid must travel more
than 4 ft before deflection.

19.  Depend upon :
 The type of the impeller
 The characteristics of the liquid(especially viscosity)
 The size and proportions of : 1) tanks
2) baffles
3) impeller
Flow patterns

20. Vr
Vt
Vl

21. http://www.dynamixinc.com/baffled-by-baffles

22. Vortex elimination

23. Small tank
http://www.dynamixinc.com/baffled-by-baffles

24. Angle with the
radius
http://www.dynamixinc.com/baffled-by-baffles

25. “Baffles”
http://www.dynamixinc.com/baffled-by-baffles

26. Power consumption
Pumping number
Power number
Reynolds number
Power correlations

29. A simple numerical
For a vessel containing 5000 gal of liquid with specific gravity = 0.9
and viscosity of lOOcP, find size and speed of a pitched turbine
impeller to deliver 2 hp/1000 gal. Check also the superficial linear
velocity
Solution :
1) Size : d = 0.40 = 0.4(9.5)(12) = 45.6 in , say 46 in .
2) P= 2V = 2(5) = lO hp. (1 hp = 0.74 kW) = 7.4 kW .

30. Standard
speeds
Developed
formulae
Formulae source : www.pacontrol.com
Above 1000

31. 1.3

32. N = 84 Rotations per minute

33. I fps = .308 m/sec
So 0.68 fps = 0.207 m/sec
1 cubic foot per second = 0.0283168466
cubic meters / second
48.1 cfs = 1.362 cubic meters / second

34. Input
parameters
www.checalc.com

35. identical
identical
www.checalc.com

36.  The performance of a particular agitator usually
cannot be predicted quantitatively.
 Agitator design is largely in exercise of judgment so
a considerable variety has been put forth by various
manufacturers.
 Developing software .
Conclusion

37.  www.fusionfluid.com
 www.checalc.com
 www.wikipedia.org
 www.bakker.org
 www.pacontrol.org
 www.safaribooks.org
 Unit Operations of Chemical Engineering (7th
edition)(McGraw Hill Chemical Engineering
Series)Warren McCabe Julian Smith Peter Harriott
 www.dynamixinc.com
Bibliography