Batch Batch size
The batch size can mean two things
- the batch mass [kg or t] or
- the batch volume [dm³ or m³]
The batch mass is calculated from the product of bulk density and batch volume.
m = ρ ⋅ V
Here, m denotes the mass, ρ (Greek “rho”) denotes the bulk density, and V denotes the batch volume.
When mixing powders, the mixing vessel must be larger than the actual batch. There must be a sufficiently large gas space above the fill level. This is important because the mixing tool causes movement in the product. This loosens the powders, which then require more space than when at rest.
The usable batch volume of a mixer, reactor, or vacuum mixing dryer is always smaller than its gross volume. The size of this difference depends on the design and the mixing tool.
When comparing prices and performance, it is therefore advisable to refer to the usable volume. Other terms for this are net volume, batch volume, or batch capacity.
Manufacturers define the sizes of their mixers differently. Some refer to the total volume (gross volume). Others define the maximum usable volume as the size.
amixon® defines the sizes of its mixers, vacuum dryers, and synthesis reactors based on the maximum usable volume in liters. For example, a VM 5000 vertical mixer can mix batches of up to 5 m³. A HM 10,000 twin-shaft mixer can mix batches of up to 10 m³. An AM 2600 cone mixer can mix batches of up to 2.6 m³.
The volume of a batch can change during the mixing process. In most cases, it decreases slightly. In certain cases, however, such as when powders are moistened, it can also increase. This must be taken into account when defining the batch size.
A powder mixer should never be overfilled. Otherwise, mixers, synthesis reactors, and vacuum mixing dryers can be damaged.