McLanahan | Why Is Filter Press Core Blow Needed?

Why Is Filter Press Core Blow Needed?

Dennis Zink
By: Dennis Zink October 8, 2019
Core blow is an option for dual feed Filter Presses that can provide many benefits, including maximum cake dryness and extended filter cloth wear life.

Filter Presses are designed to dewater and separate slurry material into solids and liquids. The slurry can be fed into one or two ends of the Filter Press with appropriately designed feed piping. 

Larger Filter Presses with more than 50-100 filter plates require higher slurry flow rates to initially fill the empty chamber spaces. Feeding the press from both ends allows the fill time to be shorter without excessively high slurry feed velocity through the core hole areas. 


What is core blow?

When the Filter Press is designed to feed from both ends, it is also possible to complete a “core blow” at the end of the filtration stage to remove wet slurry remaining in the core hole area before the dewatered cakes are discharged.

Without completing a core blow, the wet slurry will be discharged with the dewatered cakes when the plates are opened. The wet slurry discharging with the cakes will increase the average cake moisture and may cause problems transporting and storing the dewatered filter cakes. 

Additionally, the wet slurry material can build up on the filter cloths below the core hole area, and partially dewatered cake material can remain in the core hole. Both of these conditions increase the wear on the filter cloths, reducing the potential cloth life.  


Partially blocked core holes.

How does the core blow process work?

The core blow is accomplished using a set of automatic valves connected to the slurry feed piping. 

Prior to opening the Filter Press to discharge the dewatered cakes, the slurry is flushed out of the core hole with water and/or compressed air. The water and/or compressed air are fed into one feed end of the press, and the slurry is forced out of the opposite end of the press, typically back to the slurry feed tank. 

With the feed slurry lines isolated with auto-valving, water is first pumped through the core holes to wash out any residual slurry material using a centrifugal water pump. The water pump is then stopped and compressed air is forced through the core holes, removing the flush water and any remaining slurry materials. 

An animation of the core blow process. 

Typically, the core hole water and air flush combined is completed in 30 to 60 seconds per cycle

Following the completion of the core blow, the Filter Press is unclamped and the filter plates are opened, allowing the dewatered cake material to be discharged to the ground or onto a collection system below the Filter Press.

Benefits of Filter Press core blow

The benefits of the core blow can result in the following:

  • Elimination of wet slurry discharging with the dewatered cakes
  • Maximum cake dryness
  • Maximum water recovery
  • Longer cloth life cycles due to less cloth wear
  • Reduced cloth cleaning frequency
  • Reduced frequency of slurry blowouts between filter plates, resulting in: 
    • Less wear and damage to the Filter Press and other equipment components
    • Less housekeeping cleanup effort
    • Lower safety risk from slippery, wet surface 


Dual feed inlet pipe.

Adding core blow to your Filter Press

Customers should specify the core blow feature when evaluating new Filter Press equipment, as it will not be automatically included from every supplier, even if dual feed capabilities are included. 

The core blow feature can be added to existing dual feed capable Filter Presses with the installation of the required auto-valving, piping and upgraded controls. 

Including or installing the core blow feature will help optimize Filter Press dewatering efficiency, equipment maintenance, operator safety and general housekeeping.

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