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


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 


There are two types of vessel configuration: 

• Vessels with conical bottom for cake filtration and

• Vessels with dished bottom for slurry thickening

The Cake Discharge

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

• 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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