How Do I Select the Proper Size Disperser?

How Do I Select the Proper Size Disperser?

The size of a disperser is generally thought of in terms of horsepower. However, there are dispersers that are dimensionally very large but use relatively small amounts of horsepower. These are exceptions to the rule.

The horsepower of the disperser is related to the blade diameter and the anticipated load the blade will create at a given speed and resistance. The resistance is a function of the rheology of the dispersion as well as the viscosity and density. However, as the blade diameter increases, the horsepower increases disproportionately. For example: If a 12” diameter blade were to draw 20 HP in a non-Newtonian system (viscosity changes with shear), doubling the blade diameter could increase the horsepower demand by a factor of 5. That means a 24” diameter blade of the same design, working in the same product, would require 100 horsepower. The larger blade would also pump considerably more so it would lend itself to working in a much larger (perhaps 5 times the volume) tank and producing a much greater amount of finished product in the same time period.

Horsepower requirements are interrelated with blade diameter, tank diameter, batch size, rheology, viscosity and density. Variations outside recommended operating parameters usually result in compromises in performance such as poor particle separation, extended dispersion times, and a decrease in quality of the finished product.