Candle Filter - Pharmaceutical Engineering B. Pharm Third Semester PDF Notes

Candle Filter

The  Candle  Filters  are,  as  all  pressure  filters,  operating  on a  batch  cycle  and  may  be  seen  in  process  lines  handling titanium  dioxide,  flue  gas,  brine  clarification,  red  mud, china  clay,  fine  chemicals  and  many  other  applications that  require  efficient  low  moisture  cake  filtration  or  high degree of polishing

The Candle Filter consists of three major components:

• The vessel 

• The filtering elements 

• The cake discharge mechanism 

The Vessel       

There are two types of vessel configuration: 

• Vessels with conical bottom for cake filtration and polishing

• Vessels with dished bottom for slurry thickening

The Cake Discharge Mechanism

There are two methods to discharge the cake at the end of the cycle:

• Snap blow

• Vibrating mechanism

Cakes that discharge readily a snap blow from the backside of the medium is sufficient to release the cake but cakes that are difficult to discharge require a mechanism that assists release by vibrating the entire pack of candles

In this instance it is good practice to incorporate special headers with high impact sprays in the upper part of the vessel to clean the candles and dislodge entrained particles


• Excellent cake discharge

• Adapts readily to slurry thickening

• Minimum floor space

• Mechanically simple since there are no complex sealing glands or bearings


• High headroom is required for dismantling the filtering elements

• The emptying of the vessel in between cake filtration, washing and drying requires close monitoring of the pressure inside the vessel to ensure that the cake holds on to the candles

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