BHS Filtration

Candle Filter

General Description

Criteria Download PDF Brochure PDF

The BHS Candle Filter provides for thin-cake pressure filtration, cake washing, drying, reslurry and automatic discharge as well as heel filtration in an enclosed, pressure vessel. Units are available from 0.17 m2 up to over 100m2 of filter area per vessel.

Candle Filters are installed for clarification and recovery applications from liquids with low solids content from 5% to less than 1% solids and even down to trace amounts.   

Technical Description

The filter candles, consist of three components: single-piece dip pipe for filtrates and gas, perforated core with outer support tie rods and filter sock media. The filtrate pipe is the full length of the candle and ensures high liquid flow as well as maximum distribution of the gas during cake discharge. The perforated core can be a synthetic material, stainless steel or Hastelloy and is designed for the full filtration pressure. The outer support tie rods provide for an annular space between the media and the core for a low pressure drop operation and efficient gas expansion of the filter media sock for cake discharge. Finally, the filter media is a synthetic type with a clean removal efficiency of 0.5 microns. As the cake builds up, removal efficiencies improve to less than 0.5 microns.

Automatic Process Cycles

Filling: The slurry feed enters the bottom of the filter vessel.
Filtration: The slurry is pumped under pressure into the vessel. Cake will deposit on the outside of the candle; the separated filtrate will flow through the filtrate pipe and the registers. This process continues to a maximum pressure drop, the maximum cake thickness, or the minimum flow.
Washing: Displacement washing or recirculation washing.
Drying: Blowing gas, steam or “shock” drying.
Heel Filtration: The liquid remaining in the vessel cone after filtration or washing is completely filtered.
Cake Discharge: Gas flows through the register pipes, and down the filtrate pipe. The filter media gently expands allowing for cake discharge. Alternatively, the cake can be discharged as a slurry.

Dry Cake discharge

At the end of filtration, cake washing and drying, the solid matter is discharged completely by gentle expansion of the filter sock with low-pressure gas. Alternatively, the cake can be reslurried and discharged as a concentrated slurry. 

Selection of candle filter technology

Cake Thickness and Filtration: The candle filter is limited to cake structures that can be formed to about 5 – 25 mm with and can conduct filtration up to 150 psig.
Filter Media: The candle filter uses only synthetic media and use media with a clean removal efficiency to less than 0.5 microns.
Cake Washing: If the process requires washing, displacement washing can be conducted.
Cake Drying: The candle filter can produce cakes as low as 10 – 15% moisture. This moisture level depends upon the specific cake but the moisture lower limit is that moisture just about the cake cracking point.
Cake Discharge: Complete cake discharge with no residual heel by gentle gas expansion of the filter sock.
Sock Cleaning after Cake Discharge: If necessary, sock cleaning is accomplished by filling and circulating cleaning fluids while blowing gas in the reverse direction to the filtration direction, which creates a turbulent mixture or a quasi-ultrasonic cleaning effect.

Back to top


Fine chemistry:






Industrial effluent:


Environmental technology:




Clarifying filtration:






Back to top

Technical Data


Number of Candles

Filter- area  in m2

   CF 7 - 2



   CF 7 - 4


 CF 13 - 4



 CF 13 - 7


 CF 19 - 6



   CF 19 - 10


   CF 31 - 11



   CF 31 - 16


   CF 37 - 13



   CF 37 - 19


   CF 49 - 17



   CF 49 - 25


   CF 61 - 21



   CF 61 - 31


   CF 69 - 23



   CF 69 - 35


   CF 77 - 26



   CF 77 - 39


   CF 91 - 31



   CF 91 - 46


Contact BHS for Systems with up to 400 candles and larger




  • Metallic materials contacting the product: carbon steel, stainless steel, alloys and lined-vessels
  • Filter fabrics:  Various synthetic media from 0.5 um to up to 100 um

Technical data may change due to technical progress. Subject to modification without notice.

Back to Top

Related Articles

Back to top