If we compared the number of continuous mixers and the number of batch mixers across all industries, we would quickly see that the number of batch mixers exceeds the number of continuous mixers by far. Batch mixers also dominate the array of different mixer designs.
In general, bulk goods are preferably mixed and treated continuously. However, if many components have to be mixed and if very high mixing qualities are required, then batch mixing is preferred. A batch mixer offers much more flexibility in practice. This is another reason why batch mixing plants are much more common.
The batch mixer - on the left - works in batches. The mixing tool only starts to rotate when the individual components have been filled in. The mixer changes the position of all particles in relation to each other by three-dimensional flowing of the goods. The state changes from "unmixed" to "technically ideally mixed". Only then does the discharge process take place.
In the case of continuous mixing - shown on the right - the components involved are continuously fed into the mixer in the correct mass ratio. The material streams are homogenized in the mixer and the mixed material is continuously discharged. In this case, the concentration gradient is lower because the so-called continuous boiler flow has already produced a homogeneous mix base. Input material flows are comparatively small in relation to the already homogenized vessel contents. For example, the average residence time can span between 0.5 and 3 minutes.
At this point, it should be noted that a distinction is made between two types of continuous powder mixing: The tube flow and the boiler flow.
Yes, that is correct. Errors made during dosing lead to the wrong mixing result. Errors that occur for a short time should be corrected immediately. Continuously operating mixing systems have become established since there are accurately operating powder feeders that have high "short-term accuracies". In terms of mixing quality, gravimetric feeders should be given priority. They are also called "Loss and Weight Feeders".
Depending on the type of continuous mixing, residence time spectra may differ. Continuous mixers that have larger residence time spectra can compensate very well for dosing errors that occur for a short time.
The specifics of mixing in the form of classic tube flow and boiler flow are described in another blog entry.