When a factory operator needs to invest in a new solid mixing system, be in pharmaceuticals, food or chemicals, the question of the technology of mixing will be asked. The process can either be batch or be based on a continuous dry-mix. Often, there is no direct answer and a rigorous comparison in between both options must be done, following different criteria, like capacity, space available, recipe formulation, competencies of local operators...etc...
This webpage is proposing a comparison table to help factory owners make their choice in between the 2 technologies.
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What is the difference in between batch and continuous process for the mixing of solids ?
||Batch mixing||Continuous mixing||Explanations|
|Recipe complexity||From simple to complex||Rather simple - if no preblend - Limited number of ingredients 4-6|
|Flexibility - ease of changeover||High||Low|
|Capacity||Wide range||Wide range
Can reach higher capacity than batch
|Layout requirement (comparison at same capacity)||Higher||Lower||Continuous mixers are much smaller than their batch equivalent for a same line capacity. The buffer capacities above and after the mixer can also be smaller|
|Segregation||Higher||Lower||The continuous extraction of mixed powder from a continuous mixer allows the process to be less sensitive to segregation than batch (discharging the batch at the end of mixing creates segregation although it is often in acceptable limits)|
|Competency required for operation||Low||High|
|Automation||Simpler||More complex||The control of the feeders in continuous mixing must be elaborate in order to have an accurate dosing. As well, the start-up and stoppages procedures must be controlled. The ratio of the different ingredients must also be monitored in order to detect any deviation in the ratios of dosing.|
|Process validation||May be every batch||Per run||In stringent applications like pharma, it may be required by authority to positively release each batch. A continuous mixer, for which a batch is a long run, may then have an advantage|
In summary, continuous dry-mix are interesting to minimize layout requirement and investment for rather big lines with a simple set of recipes. They can also be interesting in pharma vs batches in order to have less release tests to perform.