The job of the sand classifier is to reduce the amount of filler material in sand (ultra-fine dust content with a grain size of < 0.090 mm) to the desired level. The most difficult aspect of this process is the need to reduce agglomerates, i.e., to split the fine and coarse content so that it becomes possible to separate it cleanly in the classifier.

For this reason, the separation process takes place in two stages:

1) The sand classifier is loaded with material from above. This material subsequently flows downward over several cascades. The air required for the classifying process is pulled in from below and is blown in crosscurrent fashion through the material using the cascades, which function here as nozzles. This creates powerful shearing forces that separate the fine-grained from the coarse-
                                           grained particles.

2) As the process proceeds, it is important to achieve a uniform upward flow in order to use gravity for further separation. In this process, coarse particles fall out of the classifier’s bottom. Fine particles, on the other hand, are carried upward and out of the classifier by the flow of air before being fed to the dust filtration plant.

The special advantage to this new development from SCHEUCH is the outstanding separation performance and the ability to adjust the amount of filler, e.g., from 25% filler to 10% — or even further to levels as low as about 5% if so desired. Removal of the filler material is achieved with only a small percentage of over-sized grains.