Can a mixing reactor combine mixing, drying and reaction processes in a single step?
Yes. Modern mixer-reactors can combine mixing, drying and reaction processes in a single, closed apparatus ("one-pot processing"), provided the mechanics, thermal systems and vacuum technology are designed accordingly.
Technical basis
A multifunctional mixer-reactor requires:
- Mixing elements (ploughshare, paddle or helical tools) that circulate the product intensively and continuously bring fresh particles to the heat transfer surfaces.
- Thermal systems (double jacket, heated walls and tools) for targeted heating and cooling, in order to control the heat of reaction and provide the enthalpy of evaporation for drying.
- A vacuum-capable, sealed design, so that boiling points can be lowered, solvent vapours drawn off and temperature-sensitive products dried gently.
Integrated process steps
The following can typically be carried out in a mixer-reactor either in sequence or overlapping:
- Mixing and homogenising of solid, liquid and pasty components.
- Reaction control through a regulated temperature, pressure and gas atmosphere as well as targeted dosing of reagents and catalysts.
- Drying and separation of water or solvents, frequently under vacuum with extraction and condensation of the vapours.
The mixing tool must transmit high torques from low-viscosity liquids through to the plastic and solid phase, minimise build-up and ensure homogeneous movement.
Advantages and limits
One-pot processing offers:
- fewer machines and less peripheral equipment,
- shorter process times and fewer product transfers,
- lower product losses and contamination risks,
- higher yield, reproducibility and efficiency in terms of floor space and energy.
Not every formulation is suitable for it. The viscosity profile, tackiness, heat demand, explosion protection and target parameters such as particle size distribution, residual moisture and purity must be examined critically. Pilot plant trials are therefore central to assessing the combined operating mode reliably.
How amixon® combines mixing, drying and reacting in one apparatus
Where chemical processes demand precision, amixon® combines mixing, drying and reaction processes in a single apparatus. Vacuum mixer-dryers and synthesis reactors are designed for this as multifunctional, pressure- and vacuum-tight systems.
The multifunctional mixer-reactors VMT and AMT
Two designs cover complex procedures:
- Vertical mixer-dryer/reactor VMT with a flat base
- Conical mixer-dryer reactor AMT with a conical mixing chamber
Both machines are vacuum- and pressure-resistant (typically fine vacuum down to approx. 5 mbar, system pressure up to around 30 bar) and fully temperature-controllable – mixing chamber, helical mixing tool, mixing tool arms and cutting rotors can be heated or cooled with water, steam or thermal oil. Mixing, reacting, suspending, crystallising, chemical precipitation, washing, de-agglomerating, coating, conditioning and vacuum contact drying can thus be combined in one apparatus.
Large heat transfer surfaces and short process times
The SinConcave®/SinConvex® helical mixing tool, in a smooth or MultiPlane® version, is fully temperature-controllable and works with a double-walled mixing chamber that is likewise temperature-controlled. This creates a particularly large specific heat transfer area, which permits:
- rapid heat input and removal,
- a high drying rate at low product temperatures and
- very short process times.
Temperature-controllable cutting rotors ease the passage through tough plastic phases, shorten the process time and de-agglomerate along the way. A heatable vapour filter returns fine dust to the product and allows solvents to be condensed and recovered.
Hygienic design, materials and sizes
Mixing chamber and mixing tool are welded free of crevices and ground smooth, and the mixing tool is mounted at the top only; discharge fittings are dead-space-free, vacuum- and pressure-resistant. ATEX Zone 20 design, inerting and FDA-compliant sterile reactor versions to EHEDG and 3-A standards are available.
Depending on the task, highly corrosion-resistant materials such as Alloy 59, Hastelloy-C22 or nickel are used. Typical sizes range from approximately 100 to 50,000 l, and process-reliable fill levels begin at around 15 % of the volume.
Trial-based design and qualification
Large vacuum mixer-reactors are designed on the basis of pilot plant trials with original products within the intended temperature and pressure range (up to approx. 350 °C, from fine vacuum to double-digit bar pressures). Difficult scale-up tasks (a factor of 100 and more) are secured by thermodynamic calculations and references from large industrial plants.
For regulated environments, amixon® supplies qualifiable one-off machines to URS, including support for DQ, IQ and OQ. Documentation and execution follow, on request, EU GMP and FDA 21 CFR Part 11; on request the machines meet additional standards such as EHEDG, 3-A, USDA, GMP and ATEX and are fully integrated into the operator's validation concept.