Batch Batch size

The batch size can mean two things

• the batch mass [kg or t] or also
• the batch volume [l = dm³ or m³]

If a liquid batch or a powder batch is to be mixed, the container in which the mixing process takes place must be larger than the batch volume. There must be a free space above the filling level. This is also known as the gas space. The mixing movement generated by the mixing tool loosens up the powder. Loosened powder requires a larger volume than stationary powder.

The maximum usable batch volume of a powder mixer, synthesis reactor or vacuum mixer dryer is always smaller than the construction volume = gross volume of the apparatus. The percentage by which it is defined as smaller depends on the design and mode of operation of the mixing tool.

When comparing the price/performance of different mixers, reference should always be made to the usable volume in litres or cubic metres. Other terms for usable volume are net volume, batch volume or batch volume.

It should be noted at this point that mixer manufacturers define their sizes differently. Some define their sizes as gross volume or gas chamber volume or total volume. Other mixer manufacturers define the sizes of their mixers according to the maximum usable volume, the net or usable volume.

In most cases, the mixed batch is also the population from which samples are taken for analysis as part of quality assurance.

Sometimes the volume of a mixed batch is reduced by the mixing process. In most cases, however, the batch volume does not change significantly. In rare cases, especially with solid-liquid mixtures or synthesis reactions, the batch volume in the apparatus increases. This must be taken into account when filling the apparatus.

Caution!      Process equipment usually reacts very sensitively to overfilling.
sensitive to overfilling. They can even be destroyed as a result.

Similar effects also occur in isolated cases with vacuum mixed drying. In most cases, however, the batch volume is reduced by the drying process.

In most cases, plant operators want to calculate the output of their equipment in kg or tonnes. To do this, the bulk density of the finished mixture must be known. This cannot be calculated, but must be measured. See "Measuring the bulk density of a powder" in the amixon glossary.

If you multiply the volume of a batch by the bulk density, you get the mass of the batch.