Decanter Operation; Decanter Operating Principle; Operating Mode - ABB ACS880 Supplement Manual

20 Decanter program features

Decanter Operation

Decanter operating principle


The Decanter control fulfills the common requirement of two-shaft decanters, where the
machinery consists of a bowl and a scroll (screw conveyer).
Bowl
Gear
box
Liquid output
Figure 6. Two-shaft Decanter
A two-shaft Decanter operates on the principle of sedimentation. The slurry (input product)
is fed through a fixed central pipe into the distributor located in the scroll. Thereafter the
product is accelerated through the spiral gravity separator to the bowl. This means that
solid particles heavier than the liquid will settle out. Centrifugal force speeds up the
separation process.
The bowl speed is the master speed of separation. The speed difference (delta speed)
between the bowl and the scroll influences directly to remove the solid particles. The
master speed (bowl actual speed) is sent from the Bowl drive through the DDCS link to the
Scroll drive. The Scroll drive does the necessary scaling based on the gearbox and belt
gear parameters.
The process load compensation function (Torque window control and Direct torque
compensation) supervises the actual torque of the Scroll drive. When necessary the
function corrects the delta speed reference. The delta speed reference is subtracted from
(or added to) the master speed and used as the speed reference of the follower (scroll).

Operating mode


Decanter control can be set with parameter
For using the Decanter, see steps in
examples (page 25).
Screw (scroll)
74.01 Centrifuge/ Decanter function
Decanter drive start-up
Slurry input
Solids output
selection.
(page 10) and Decanter