Top discharge centrifuges

The suspension that is to be separated is filled into the horizontal, overhung perforated basket at a pre-selected loading speed. As a result of the centrifugal force, the solid particles settle on the filter fabric on the basket shell. 

The solids are retained by the filter fabric, suspension fluid flows through the forming filter cake, including the filter fabric and leaves the perforated basket through bore-holes in the basket sleeve. 

During filling, the fluid level in the basket and the growth of the filter cake are controlled by sensors. Upon reaching the desired filter cake height the filling process is stopped automatically.

Depending on the product, a filling process will be interrupted by intermediate spinning with increased speed, in order to free filling volume in the basket and continue the filling process. 

Depending on the filtration reaction of the product, intermediate spinning will be repeated several times. 

As soon as the suspension fluid has been centrifuged, the washing the solids in the basket process is started. During this phase the washing fluid is evenly distributed via a suitable washing pipe (nozzle pipe or orifice-type sprayer) throughout the whole length of the basket.

as a result of the centrifugal force, the washing fluid penetrates the filter cake, displaces the still sticking suspension fluid and leaves the basket in the same way as the suspension fluid during filling. Washing can be carried out at the same or higher speed than the filling process.

In order to separate the fluid from the filter cake the basket is generally accelerated to the maximum allowable speed and kept constant at this speed. 

Kinetics of the hydro-extraction process depend on the solids and fluid parameters, the height of the filter cake and, naturally, the centrifugal force acting upon the fluid that is to be separated. 

The residual humidity in the filter cake decreases over time under the constant  centrifugal force and asymptotically it approaches a theoretical limit.

After hydro-extraction and with the basket rotating, the filter cake is peeled layer by layer by means of a discharge device.

This is done by inserting a short peeling knife horizontally below the basket rim into the filter cake close to the filter medium. Then, the peeling knife is slowly moved downwards, during which it removes the filter cake except for a residual layer. 

The scraper speed must be selected so the solids can fall freely through the opening in the basket floor into a hopper below the centrifuge.

Cleaning of the interior of the centrifuge is often required after every cycle or several cycles, in order to ensure a defined product separation between two following batches, or to prevent an infection. 

The inside of the centrifuge with all built-in devices can be completely cleaned with an integrated CIP cleaning system without the need to open the centrifuge.