In a number of industries, powders are combined with other powders, or binders, in high-shear blending operations, to form homogeneous mixtures for further downstream processing.
The wide scope of blender sizes, methodologies, and geometries means that performance can differ between machines, creating mixtures with different flow characteristics which perform differently in subsequent operations.
It is vital to understand the effect of any given unit operation on downstream performance, as incompatibility can result in a product which is out of specification and not fit for purpose. An understanding of how the powder and the process interact with each other is needed to make sure that downstream performance has not been influenced detrimentally by upstream processes. The process can be optimized to supply a product with desirable properties once this is understood. This supplies major commercial advantages in terms of reduced wastage and higher productivity.
The Influence of Processing Powders
For the production of refractory bricks, three blends of Magnesium Oxide (MgO) and Graphite, together with a resin binder, were utilized. The blends were prepared using different mixers (Mixer 1, Mixer 2 and Mixer 3) but were from the same feedstock, and differences in the quality of the final product were noted depending on the mixture employed.
Mixture 1 exhibited optimum performance, Mixture 2 represented intermediate performance, and Mixture 3 showed the worst behavior. The three mixtures were assessed by employing an FT4 Powder Rheometer® to look at the dynamic flow, bulk and shear properties.
FT4 Powder Rheometer®
The FT4 Powder Rheometer is a universal powder tester which supplies reliable, automated, and comprehensive measurement of bulk material characteristics. To increase processing efficiency and aid quality control, this information can be correlated with process experience.
It specializes in the quantification of dynamic flow properties, the FT4 also incorporates a shear cell, and the ability to measure bulk properties such as compressibility, density, and permeability, allowing comprehensive characterization of a powder in a context which is process relevant.
Dynamic testing uses a unique measurement method to establish a powder’s resistance to flow. A specially shaped blade traverses along a prescribed path through a precise volume of the powder. As it moves axially and rotationally, the force and torque acting on the blade are combined to supply a value for flow energy.
Results of the Study
Dynamic Testing: Basic Flowability Energy (BFE)
Mixtures 2 and 3 produced BFE values which were comparable, but the BFE of the Mixture 1 was notably higher. High BFE shows a better resistance to flow, which is likely due to a more uniform particle packing structure in this case...
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This information has been sourced, reviewed and adapted from materials provided by Freeman Technology.
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