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What advantages do vacuum reactors offer for reaction mixing and drying in fine chemicals?

In fine chemistry, vacuum reactors offer above all thermal protection, improved mass and heat transport as well as efficient reaction management, mixing and drying in a closed system. Sensitive products, intermediates and solvents can thereby be processed in a targeted manner at reduced temperature and with greater process control.

Advantages for reaction mixing and process management

  • Improved homogenisation: in combination with suitable agitator elements, uniform blending is achieved even with viscous, pasty or suspension-containing batch systems.
  • Better mass and heat transport: process intensification reduces transport resistances at interfaces and thereby improves heat removal and mass exchange within the reaction system.
  • Higher reaction yield and selectivity: more intensive blending and more targeted process management can improve conversion, yield and selectivity.
  • One-pot process: reaction, distillation, crystallisation, filtration and drying can be combined in one apparatus, which reduces transfer steps and minimises product losses.

Advantages for drying and solvent removal

  • Lowered boiling temperatures: under vacuum, solvents and volatile constituents evaporate at considerably lower temperatures.
  • Gentle drying: thermally sensitive substances are subjected to less stress, which reduces decomposition, discolouration or structural changes.
  • Faster mass transfer: the reduced pressure increases the driving force for evaporation and accelerates drying and desorption processes.
  • Homogeneous residual moisture: defined vacuum conditions make it easier to set reproducible residual solvent and residual moisture values.

Advantages for product quality

  • Protection of sensitive molecules: lower process temperatures are particularly important for thermolabile active substances, intermediates and polymorphic solids.
  • Less oxidation and hydrolysis: operation in a closed system and under reduced pressure can decrease contact with oxygen and moisture.
  • Better particle properties: gentle removal of solvents can reduce sticking, agglomeration and unwanted changes to the crystal structure.

Advantages for safety and economy

  • Closed system: vacuum reactors lower the exposure of operating personnel to volatile, toxic or highly active substances.
  • Efficient solvent recovery: solvents can be recovered via condensers, which reduces costs and disposal effort.
  • Lower energy input: lower process temperatures and integrated process steps can reduce the overall energy demand.
  • Shortened cycle times: combining several unit operations in one apparatus supports more intensive and more economical production.

Vacuum reactors are therefore particularly suitable for fine chemical and pharmaceutical applications in which product quality, reproducibility, containment and efficient drying are required at the same time.

How amixon® implements the advantages of the vacuum reactor for fine chemistry

There are two series for reaction mixing and vacuum drying

  • amixon® manufactures vacuum mixing dryers and reactors in two vertical designs: the vertical mixing dryer/reactor VMT and the conical mixing dryer reactor AMT. Both are of pressure- and vacuum-tight construction and can reach a vacuum of 5 mbar absolute. They can be pressure-resistant up to 30 bar. They are fully temperature-controllable with water, steam or thermal oil.
  • Their unique feature is that the helical mixing tool (shaft, arms and helix) can also be fully temperature-controlled. In combination with the double-walled mixing chamber, this creates particularly large heat transfer surfaces. These enable rapid heat input and extremely short drying times even at low product temperature differentials.
  • Mixing, reacting, suspending, deagglomerating, coating, conditioning and vacuum contact drying can be combined in the same apparatus. For fine chemistry this means that the highly concentrated active substance remains in a closed, pressure- and vacuum-tight system from the synthesis step through to the free-flowing final powder. Exposure risks are avoided.
  • Process parameters such as system pressure, temperature, sequential addition of substances (dry, wet or gaseous) and mixing intensity are freely adjustable. Cutting rotors with mechanical seals accelerate the mixing drying and deagglomerate alongside it, for example when tough plastic phases are passed through during drying.
  • The vapour handling is solved in a consistently hygienic manner: the temperature-controllable vapour filter can be provided with a lateral inspection door. The fine dust is returned to the process chamber. The extracted solvents are condensed and recovered.

Freedom from dead space and product protection

The mixing chamber and mixing tool are fully welded and ground. The mixing tool is supported and driven at the top only. The ball segment valve in the outlet has little or no dead space and is vacuum- and pressure-resistant. Drying takes place at low temperatures and low rotational frequencies. It is therefore also suitable for the most sensitive materials such as fungal spores, bacterial cultures or effect pigments. Free-flowing mixes can be discharged almost completely. amixon® apparatus can also be used at low fill levels of, for example, 15 %. This is helpful for evaporation processes.

Safety, hygiene, materials

  • The mixing chamber is optionally pressure-resistant or explosion-pressure-shock-resistant and designed in accordance with ATEX Zone 20. It can be used for hybrid material systems. This is relevant in particular for solvent-moist, ignitable powders. On request, the apparatus is designed as an FDA-compliant sterile reactor, meets the EHEDG requirements as well as the 3-A Sanitary Standards and is suitable for steam sterilisation.
  • High-alloy materials up to Alloy 59, Hastelloy-C22 and nickel are available for corrosive reaction systems. Ceramic plasma coatings serve as wear protection. The VMT 200 made of Alloy 59 serves as a reference.
  • The sizes range from 100 to 50,000 litres in 100-litre increments. The design is secured by drying and reaction trials in the amixon® pilot plants. amixon® also supports the dimensioning of large vacuum mixing dryers with empirical values from its own works operation.