microcondensation
Microcondensation refers to the formation of very small amounts of condensed water vapour on the surfaces of individual particles. Bulk solids consist of a two-phase system of solids and gas. The high porosity of dispersed systems allows water vapour to penetrate deeply into the bulk solid bed.
m˙cond is the mass of condensed water per unit of time
k is the empirical heat transfer coefficient
A is the effective bulk surface area
Tsteam is the steam temperature.
Tparticle is the temperature of the particles.
Microcondensation alters the product properties of many powders. Even small amounts of water can cause agglomeration and impair flow properties. Water increases surface adhesion and can promote chemical reactions and microbiological growth. All of this has an impact on storage stability, processability and shelf life.
To prevent unwanted microcondensation, it is crucial to control temperature, relative humidity and dew point. Packaging and storage environments should keep moisture away as much as possible. Precise climate control is particularly important for hygroscopic bulk materials.
However, microcondensation can also be used for technical purposes. In amixon® mixers, bulk materials can be minimally wetted in a targeted manner. During the mixing process, the vapour of a dissolved active ingredient is finely distributed and injected. This condenses on the particle surfaces, creating micro-wetting or thin, functional coatings.
Such processes can be carried out in the amixon® technical centre. An amixon® vacuum mixer can also be operated as a contact dryer. Under vacuum, water bound to the surface evaporates even at low temperatures. Drying is therefore gentle and uniform. The controlled influence of condensation and evaporation results in a wide range of possible applications.