Decanter centrifuge designs
Dewatering decanter centrifuge for maximum concentration of solids
Clarifying decanter centrifuge for clarifying liquids
Separating decanter centrifuge for the separation of liquid mixtures and the simultaneous separation of solids
Concentrating decanter centrifuge for the concentration of solids
Extraction decanter centrifuge for the extraction of reusable materials
Classifying decanter centrifuge for the extraction of different solid fractions
The decanter centrifuge is mainly consists of the bowl, the screw conveyor, the gearbox, the frame with the hood, the feeding, and the discharge arrangement.
The bowl in a modern decanter is a cylindrical tube with a flange at either end, on which are bolted at one end the liquid discharge bowl hub. And on the other end, the cake discharge hub, or the beach followed by the cake discharge hub. The first cylindrical bowls used a filler piece in the end of the bowl to form the beach. On modern bowls particularly the larger ones, the beach is bolted to a flange at one end of the cylindrical section, although with some overlap to provide mechanical location.
The thickness of the bowl wall is dictated by the material of construction used, the maximum speed at which the bowl will be rotated. and the maximum weight of process material. feed, centrate or cake, likely to be held in the bowl. Thus the density of the process materials in use can have a major effect on the safe working speed of the bowl.
The screw conveyor (or scroll) is in the form of an Archimetlian screw. fitting inside the beach and bowl between the two end huhs. with a small clearance of less than 2 mm ratlially. lt has a number of functions. Not only does it convey the solids, after they form a cake. along the cylindrical bowl section and up the beach, it also accepts the feed and accelerates it up to bowl speed.
In its simplest form, the conveyor has a cylintlrical central hub with a set of flights welded onto it, to form one contirluou 、helix. The conveyor bearings and associated seals are housed in both ends of its central hub. Somewhere in between the bearings will be a chamber called the feed zone, sealed and isolated from both bearings.
The gearbox is a major component of the rotating assembly, which creates the differential speed between the bowl and the conveyor. Usually, the screw conveyor driven by a planetary gearbox turns slightly slower than the bowl.
There are two main types of gearboxes used on decanters. These are the epicyclic gearbox and the Cyclo gearbox.
FRAME AND HOOD
Usually, the frame is fabricated from steel channel or box sections. The frame needs to be a rigid support for the rotating assembly. The surfaces for the main bearing pillow blocks are accurately machined in the same plane, and in line. to ensure no end-to-end misalignment of the rotating assembly. which would cause premature bearing failure.
The frame and hood act as the link between the high g field of the rotating assembly and the stationary area around it.
MAIN AND BACK DRIVE
The main centrifuge drive is usually an electrical motor mounted on slide rails on the frame or sub-frame and connected to the centrifuge drive pulley with V-belts. A purpose built belt guard will cover the two pulleys and belts. Motors on the larger decanters can consume a few hundred kilowatts of power. Such large motors are more often directly mounted on the floor, in which case a special belt-tensioning device is incorporated to allow for the differential movement of the rotating assembly.
The back-drive system is a means of controlling the speed of the gearbox pinion shaft (and thereby the conveyor differential speed) using, for instance, a motor or a brake. This could be offset from the gearbox shaft. in the same manner as the main drive.