Emptying and Discharge
If no heel volume filtration is necessary, the remaining filter volume at the end of filtration can be emptied back to the product tank via gas pressure or gravity.
To prevent loss of the cake, the filtrate line must be open to allow part of the volume to pass through the cake into the filter plate
- Slurry Discharge of the Filter Cake
After emptying, the wet cake is flung from the plates by rotation of the filter nest and exits the filter through the discharge nozzle.
This procedure is helped by the addition of a clear rinse liquid (water or filtrate etc.) opposite the filtration direction. If the cake/liquid mix does not flow out by gravity, gas pressure must be applied.
- Heating, Drying
If the cake is discharged in dry form the cake is first heated by steam and is then dried by a flow of air or nitrogen. The heating and drying can also be accomplished by using hot gases.
With discontinuous use, the procedure allows for repeated build up of pressure in the vessel and evacuation through the filtrate line. This method has the advantage of lower gas usage.
- Dry Cake discharge
The filter nest rotates with an open discharge valve: centrifugal force flings the dry cake from the filter plate and allows it to fall as granular particles into a container on exiting the filter at the bottom.
In many cases, only some of the above steps are necessary.
The R-A model has an additional cylindrical part attached to the cake discharge nozzle which is necessary for the option of discharge in dry or slurry form, for example in catalyst filtration.