When mixing powders and liquids with the goal of dissolving the powders thoroughly, it is often both important and challenging to prevent lumps from forming.
The formation of lumps when mixing powders with liquids is of particular concern when working with highly viscous stabilizers or with powders that are difficult to wet. Factors like these increase the likelihood that a substance (such as a stabilizer) will form a gelling surface around powder particles, preventing the liquid from fully wetting the powder. When this occurs, lumps are the result.
Why is lumping a problem? For one thing, the functionality of a stabilizer is not utilized efficiently when lumping occurs – a situation that requires us to add more powder to the recipe to achieve the same functional results. But in many cases, the more significant problem with lumps is that they can prevent a product from being completely formed.
To keep floating solids (lumps) from forming, we need to address a variety of mixing issues, including the dispersion of the powder, the wetting of solids, shearing, and the breakup of agglomerates.
Key Steps to Prevent Lumps
To prevent lumping and clogging, it is important to pay attention to several aspects of the mixing and pre-mixing processes, including:
Batch mixers, with an optimal mixing unit inside the mixer tank, are the ideal solution when dealing with difficult powders and highly viscous liquids. Additionally, by dosing powder on the liquid’s surface and transporting it quickly towards the mixing head in a controlled vortex, we can wet the powder optimally by ensuring minimum exposure to the liquid medium.
(*Source: Handbook of Industrial Mixing- Science and Practice)
Technological Methods of Mixing Particularly Challenging Powders
Many powders that tend to lump, such as stabilizers, are notoriously difficult to disperse. To prevent lumping and clogging, these powders require high-shear mixing, which involves a tank and a rotor-stator homogenizer mixer that are optimally designed to make this mixing possible. A number of technological options have been developed for dealing with such scenarios.
“In various manufacturing processes, there are delicate powders with a small surface area that do not easily mix into a continuous main phase (liquid),” explains Eng. Korenblit (M.Sc), Mixing Expert at MGT. “To overcome this mixing challenge, various technological solutions have been tested. One such solution involves a dispersion shear disk. In a second method, a tri-blender utilizes the Venturi effect to create a vacuum that absorbs powder and injects it into a stream of liquids. A third solution involves a direct interior pipe feeder in a rotor-stator homogenizer.”
Although these three methods rely on different technologies, they are effective for similar reasons. “In each of these methods, the fine powder meets the liquid before entering the intense shear zone, an area that is particularly prone to lumping,” Korenblit adds. “To solve the problem of wetting and dispersion, we need to create a vacuum in the shearing zone, which separates particles and allows for better wetting. At the same time, we must apply shearing power to ensure that no floating solids are formed.”
Which of these three methods is the most viable and reliable for industrial purposes? “The ideal solution is to use a rotor-stator homogenizer while injecting fine powder into an intensive shearing zone to prevent the formation of powder floating solids,” Korenblit states.
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