Euroby is excited to announce the arrival of Xelletor – Flottweg SE’s latest centrifuge technology.
A radically new design addresses the three “holy grails” of dewatering – cake dryness, low energy consumption and low polymer consumption – improving all three.
Flottweg have re-examined how the decanter functions and how dewatering is conventionally optimised according to the nature of the feedstock. Granular sludges usually require a shallow cone angle of about 8°. This geometry creates a large discharge diameter and hence a shallow pond; the solids usually settle quickly and the shallow cone angle facilitates discharge. In the case of fine, pasty sludges like sewage sludge, settling is slower and the dewatering is effected by a compressive action.
A steeper cone of 15° and a smaller discharge diameter is utilised to form a deep pond, this allows a longer settling time – or greater bowl capacity, and the additional head of water increases the compressive force on the sludge. The limiting factor here is the scroll body which hinders the development of an ideal “super-deep pond” machine.
Flottweg have looked at modern engineering construction techniques and, taking a leaf out of the motorsport book, replaced the scroll body with an open space-frame on which the flights are mounted.
The design results in an extremely deep pond – with perfect axial flow. Whereas previously the feed stream was introduced in to the pond radially, with a great deal of turbulence – and associated energy losses, the Xelletor feed stream is axial and meets the liquid surface with a minimum of disruption resulting in smooth feed acceleration and low vibration.
The use of a “negative dip weir” permits the use of a large discharge diameter for the cake, but a small diameter for the centrate. The centrate discharges at a small radius and less energy is lost at the discharge point, also, the greater depth behind the dip weir serves to assist cake transfer past the dip weir by hydraulic pressure, with more energy savings.
So – what does this mean for the operator?
Tests at the end of 2015 against “conventional” Flottweg decanters showed the following improvements:
2 % higher cake dryness, or…
2 kg/tD.S. lower polymer demand
40 % saving in power consumption (compared to a traditional decanter, in this case a Z4E)
Smooth operation – low vibration
No more wear in the feed chamber, because there is no feed chamber
Variable feeding point, adjusted by varying the length of the feed pipe
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