I have a 5,000 liter reactor with the following geometry: 56-inch ID, 126-inch straight side length, ASME bell top and bottom. There are three baffles along the straight sides of the tank spaced 120 degrees apart and are 6.25 inches in width. The agitator I have is center-mounted with three blades approximately 13 inches in diameter. The drive is 1 hp with a 1,725 rpm motor and a 175 rpm output gear reducer. The shaft size is 1.5 inches and approximately 153 inches in length. Unfortunately, the viscosity of my product changes during the process. It starts out as a low viscosity (close to water) fluid, becomes thick as it is heated, and then thins out again as the reaction progresses. I need good agitation for heat transfer. What is the maximum viscosity of fluid I can mix with this type of agitator?
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Dave Dickey Forum Moderator 309 Posts
Re: What is the maximum viscosity of fluid I can mix with a certain agitator?27 May 2010 at 1:29pmThe question of maximum viscosity has different answers depending on the limiting factor. The 1 hp motor will not overload, even up to 50,000 cp. However, the mixing will not be effective above about 1,000 cp. In effect, the motor is larger than needed to operate the impeller and the impeller is smaller than needed to effectively mix the tank contents.
Increasing the impeller diameter to 18 inches from 13 inches will not overload the motor and also increase the effective mixing limit to about 7,500 cp. Even a 20-inch impeller may work, depending on the specific power number for the hydrofoil impeller. A quick check of the shaft design does not show a critical speed problem, even with the larger and heavier impellers.