Envites - Filtration with cake washing
PRODUCTS > Filter presses > With membrane plates > Filtration with cake washing

Cycle description

Description of the process stages:

  • Start of cycle
    the emptied filter press is ready to start a new filtration cycle
  • Closing of the filter press
    the whole set of filtration plates is compressed by means of a hydraulic system, filtration chambers are created between the individual plates.
  • Start of filling
    the suspension is conveyed from a pressure tank; however, a feeding pump is used more often
  • Filling of the filter press
    chambers are filled up with the suspension. Solid particles are trapped by the filtration cloth, liquid phase passes through the cloth to the plate drainage system.
  • Formation of filtration cake
    a layer of solid particles grows on the cloth, which increases the filtration resistance. The filling pressure must be increased in order for the liquid to keep passing through the cake and the cloth. The rising filtration resistance also results in reduced flow rate of the suspension through the filter press.
  • Achieving of the maximum filling pressure (usually 6 - 8 bars) and end of filling
    the feeding pump stops pumping the suspension into the filter press chambers.
  • Start of membrane compression
    water or compressed air is pumped to the room behind the membrane. The membrane presses the cake and pushes out the residual liquid.
  • Achieving of the set compression value
    the pressure is kept at this constant value throughout the cake washing, which ensures maximum efficiency of the washing
  • Cake washing
    the washing medium enters though the holes for the filtrate drainage on one side of the first plate. The liquid passes through the cake and washes out the undesirable soluble and water-soluble substances, which must be removed from the cake. The washing liquid is drained through channels draining filtrates in the second plate on the opposite side of the chamber. The washing liquid is then led across the chamber. The membrane compression ensures that the washing liquid passes through the cake and that the cake is not by-passed.
  • End of membrane compression
    water or air is pumped to the room behind the membrane. The filtration pressure starts increasing, the membrane again compresses the cake and pushes out the residual washing liquid.
  • Achieving of the maximum compression value (usually 15 bars)
    the volume of discharged filtrate is minimum and after some time it remains almost stable. The maximum pressure is maintained for a certain period of time. The filtration is completed.
  • Core blow (optional)
    the residue of unfiltered sludge is pushed out of the suspension feeding channel passing through the whole set of plates by compressed air.
  • Releasing of pressure
    the compression medium is pumped out from behind the membrane, the pressure in the filtration chambers drops to the value before the start of filtration
  • Opening of the filter press
    the hydraulic system releases the compression, the steel plate compressing the set of filtration plates during filtration is shifted away and the individual filtration plates are deflated., during the process of which the filtration cake is discharged.
  • Filtration cake drying (optional)
    Similarly to the description of the filtration cake washing it is also possible to introduce pressurized air instead of the washing medium and push the residual liquid out of the cake. Drying is usually used following the process of filtration cake washing.