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Mud
Slurry Mixing System Overland transport is generally limited to 12' diameter tanks. For a vertical cylindrical tank, to achieve 20,000 gallons, the resultant straight wall would need to be 25' tall. If a single mixer is used for this application, a rough estimate for this mixer would be about $32,000. This make no mention of the related design costs required for the tank structure that would need to support the design loads (weight, torque and bending moment) of a top mounted mixer for a vertical-on-tank-centerline mounting arrangement. In consideration of numerous other mixing applications, such as flocculation for example, it is quite common to use multiple mixers in the floc basin rather than to use either one or two large mixers. This concept can prove to be quite useful in handling slurries or slurry mixing for the purpose of waste oil recovery. There are numerous reason for the use of multiple mixers. In this instance the initial cost of four or five (4-5) smaller mixers to handle the 20,000 gallon capacity is significantly less expensive than the use of one (1) large mixer. It also evident that the performance of multiple mixers in a rectangular tank design for slurry suspension is vastly superior. From a common sense view, covering the overall rectangular area with smaller circles (diameter of the impellers) is just better than a few or even one large one. There are still even more advantage and considerations such as reduced continual energy demand (horsepower).
If we were to consider an 8.5' wide x 9'
tall x 38' long rectangular tank, to achieve the 20,000 gallon requirement,
where it is assumed that the floor footprint is available to accommodate such a
tank, there may be numerous advantages to consider. In this particular
case, due to the above stated mixer efficiencies, we considered using five (5)
mixers, subdividing the overall volume into five equal rectangular
sections. The following advantages resulted:
The first is related to the tank itself where the mixer design loads are
distributed over the length of the tank. In short a 9' tall wall with
an 8.5' span is a much less stressful and therefore more economical as
compared to the single mixer tank design. The continual energy consumed by the multiple mixer design is 1/2 that of
the single mixer design. In this case, the laws of physics govern the
solid suspension requirement. Obviously, this may not be intuitive,
however the result is apart of mixer process design optimization.
Always remember that mixer gearboxes transform horsepower into torque (the magic
black box). Torque optimums result from the mixer optimums
stated above. The initial cost of five (5) mixers was 73% of the cost of one (1) single
large mixer. This resulted directly from the consideration of mixer
optimums. Although there are five separate simple beam arrangements to span the
8.5' wide span, the cost of the simple rectangular tank is vastly less
expensive than the construction of a 12' x 25' tall tank (in carbon steel),
which may have to be built on site. Remember to consider the applied
design loads (torque, weight & bending moment) of the one (1) large
complex mixer design. 04.11.11 |
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Industrial
Portable Mixers
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