ARCHIMEDEAN SCREW CRYSTALLIZER (K) / REACTOR ASKR
Continuous crystallization like in a batch reactor
Now possible: Continuous crystallization without back-mixing and without pressure drop – and with better results compared to the batch stirred vessel.
Currently, most reactions and crystallizations are processed in batches and in stirred tanks.
Batch-processing has many technical and economic disadvantages. Unfortunately, conversion into continuous processing in a plug-flow reactor (PFR) or a continuous stirred tank reactor (CSTR) is mostly impossible due to unacceptable broad residence time distribution, the high pressure drop and the technical feasibility.
The new ASKR is different: it is the solution for all these problems for flow rates of 10 l/h to 100 m³/h and residence times of 10 hours and more.
The mechanism of action
The patented principle is very simple (middle picture): A horizontal rotating cylinder with a spiral fixed to the wall conveys fluid from the entry on one side to the exit of the machine on the other side.
Each segment is filled and intensively mixed just like a small stirred tank. The big difference is the homogeneous and turbulent mixing pattern – even without a stirrer (left picture).
• A negligible residence time distribution relates to higher product quality and faster, more effective reactions/crystallisations.
• The turbulent mixing pattern in the segments, gently produced without the use of agitators, causes less harm to the product (e.g. secondary crystallization). High shear rates on the walls reduce fouling and agglomeration. Sediments are kept in suspension (left picture).
This leads to significantly better and larger crystals, for example in L-glutamic acid in water with Ethanol as anti-solvent.
The process is studied in one segment in a simple lab reactor (right picture) over time.
The patented lab reactor is temperature-controlled to conduct heating and cooling ramps.
Lab reactor with temperature control and opening on the side:
• Temperature range: -20° C to 240° C
• Pressure range 0.125 bar (abs.) to 10 bar
The advantages of ASKR compared to batch production:
• Extremely narrow residence time distribution,
• Intensive but gentle mixing,
• Small-scale control at every stage of the process – enables immediate countermeasures if necessary,
• Significantly reduced use of space and hardware.
Resulting from this:
• More efficient and cost-effective production,
• Better product quality,
• Less production errors,
• Simple test design.