Is there any formula for calculating the height of an anchor agitator? We have a reactor with these specifications: Reactor capacity 5 KL ID 1650 mm Height of shell 2400 mm Motor 10 hp Sweep diameter 1160 mm Height of liquid 2071 mm Liquid is MDC
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Dave Dickey Forum Moderator 282 Posts
Re: Is there any formula for calculating the height of an anchor agitator?23 August 2010 at 1:29pmThe answer to your questions about an anchor impeller can be best handled in terms of fractions or percentages, which will make the guidance general and independent of your specifics.
Starting with the ID of the vessel, the anchor (sweep) diameter should be 90% to 95% of the vessel diameter, or 1485 mm to 1567 mm for your 1650 mm ID vessel. A sweep diameter of 1160 mm is definitely too small. Next, the width of the blades, not the height, should be about 10% of the anchor diameter, or 15 mm to 16 mm wide. The height of the anchor is best set based on the liquid level. The liquid level should never be more than about a blade width above the top of the anchor. Therefore, the anchor should be at least 2085 mm, but obviously less than the shell height, and best only about 90% of the shell height or 2160 mm. That information covers the basic geometry.
The power requirements cannot be determined from the information provided. The rotational speed of the anchor is major factor. The fluid properties, density and viscosity also will influence the power requirements. Finally, as a general comment: anchors do not do a good job of mixing. All they provide is some movement at the wall and rotational motion. They provide almost no top-to-bottom motion, so an addition on the surface may require an extended period of time to be uniformly distributed through the vessel. An anchor impeller is not the worst choice of an impeller for liquid blending, but it is close to the worst.