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How much horsepower is required to mix this specific material?

Q: I am designing a jacketed mixer that will mix coconut oil + 60% water. The operating speed is 10 rpm, and the operating temperature is 70 degrees C. The mixer has these specifications:

• material SS304
• inner vessel 1,250 mm X 1,295 mm
• gross capacity 1,650 liter
• blades: anchor & marine
• shaft rod 63 mm diameter
• housing shaft 70 mm diameter

Please tell me the correct hp required to mix the material. Per my thinking, 15 hp will be more than sufficient.

A: Let's work backwards on the answer to your questions.  First, 15 hp is too large for the mixer.  The 63 mm diameter shaft can only tolerate the loads of a 3 hp motor at 10 rpm.  Any more torque on your anchor impeller will bend the shaft.  At the same time, 10 rpm does not require much power to turn the impellers.  Your anchor impeller could handle up to about 100,000 cp viscosity at 10 rpm.  Your mixture of coconut oil and water should have a much lower viscosity, probably only 2,000 cp, or less at 70 degrees C.  A marine impeller at 10 rpm will not contribute to mixing and will not require any additional power, or so little you don't have to worry about it.

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