Classifying Devices

SCHEUCH Air Sifter for fibres:

The design of the SCHEUCH SWSF sifter, which includes internal guidance and distribution apparatus, ensures the homogenous distribution of both air and material, resulting in efficient separation and classification. External control equipment regulates and adjusts the distribution and velocity of the air to match a variety of operating conditions.

Ventilation options for both exhaust and recirculated air can also be freely selected. This makes it possible to minimize investment and energy costs for air conditioning and subsequent dedusting. Installation of the SWSF sifter takes place between the fibre dryer and the forming station.

Fibre quantity is measured using a screw- or belt weigher and fibres are fed to the SWSF sifter via an intermediate rotary valve. Spiked feed rollers then uniformly distribute the flow of materials over the entire cross-section and loosen and advance the material. In this way, the fibre stream enters the actual sifter, where an upward stream of air on the side of the sifter captures the fibres.

A second stream of air from below counteracts the downward motion of the fibres and builds a curtain of air. Only those particles with a higher settling speed than the speed of the rising air fallen to the bottom, where a screw conveyor feeds them to a rotary valve for discharge. The air stream carries fibre particles with a lower settling speed to the exit opening of the sifter. They are then transported pneumatically to a cyclone unit, separated and fed to the forming station.

SCHEUCH Sand Classifier

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:

• 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.

• 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.