No single “best practice” fits the many combinations of solids and liquids.  Many factors influence the success of failure of solids addition to a liquid.  A long list of solids characteristics, such as particle size and density, solids concentration, solids wetting behavior, solubility, addition rate and other factors will influence solids addition.  Liquid effects are usually simpler, but the interaction between the solids and liquid, such as surface tension and wetting characteristics are common factors.

The simple answer to whether a mixer can be used to add solids to a liquid is that many solids additions are successfully done with a mixer.  However, the mixer design depends on all of the factors previously mentioned.  Some mixers, especially in-line mixers, are specifically designed to add powders to liquids.

Valve control of solids addition is rarely successful.  A valve usually does not provides adequate control of the rate of addition.  More likely some type of mechanical feeder will be needed.

Without more specific information, the success of a mixer is impossible to predict.

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