Moisturising the Extrusion mixes:
Moisturisation of dry mixes prior to the extrusion step can be carried out using water or other materials that contain water.
Whilst it is possible to moisturise the mix in the batch mixer itself, the distribution of moisture using this method sometimes results in uneven distribution, especially if the mix contains a large amount of flour. Further, some products require the addition of water shortly before the extrusion process. In such cases, Schaaf recommends the use of continuous moisturisers, which are available in vertical and horizontal options with the following advantages -
- Uniform mixing and moisturisation of the extrusion mix.
- Continuous moisturisation, whereby the speed of moisturisation can be adjusted to the extrusion capacity if required using the automatic ON/OFF switch for the moisturiser.
- Simple control of the moisture level and short reaction time of moisture level changes. These can be performed during production by a simple turn of a knob or by changing a parameter using the digital control panels.
The moisturiser is usually installed above the extruder to allow the moisturised material to be fed into the dosing unit/processing section of the extruder directly. Although it is not often rated as a high priority, proper moisturisation of the material is an essential prerequisite for a high quality and uniform product.