A candle filter is a pressure-driven industrial filtration system used to separate solids from liquids or gases. It consists of multiple vertical porous filter elements (“candles”) installed inside a closed pressure vessel.
During operation, the process fluid flows through the candle media while solid particles accumulate on the outer surface to form a filter cake. The clarified filtrate passes through the internal core of the candles and exits the vessel.
Because of its high filtration efficiency, automated cleaning, and closed-system design, candle filtration is widely used in chemical processing, pharmaceuticals, food production, and petrochemical industries.
A candle filter is a vertical pressure filtration system designed for solid–liquid separation in industrial processes. The system contains multiple cylindrical filter elements mounted inside a pressure vessel.
Each candle element acts as a porous filtration medium. Common materials include:
• stainless steel wire mesh
• sintered metal
• ceramic media
• polymer or fiber filter cloth
When process slurry enters the vessel under pressure, the liquid passes through the porous walls of the candles while solid particles remain on the surface. Over time, these particles form a filter cake, which improves filtration performance by trapping finer contaminants.
A typical industrial candle filter includes several key components:
• Pressure Vessel
The closed housing that contains the candle elements and maintains filtration pressure.
• Candle Filter Elements
Porous cylindrical tubes that act as the filtration media.
• Tube Sheet or Support Plate
Holds the candle elements in position and separates feed from filtrate.
• Filtrate Outlet System
Collects the filtered liquid from the inner core of the candle elements.
• Cleaning System
Backwashing or gas pulsing removes accumulated filter cake to restore filtration capacity.
The candle filtration process usually follows a cyclic operating sequence.
1. Feed and Filtration
The slurry enters the vessel under pump pressure and flows from the outside to the inside of the candle elements.
Solid particles are captured on the surface of the candles while the liquid passes through the porous media.
2. Filter Cake Formation
As filtration continues, particles accumulate on the candle surface and form a filter cake layer.
This cake acts as an additional filtration barrier, allowing the system to capture finer particles and improve overall filtration efficiency.
3. Pressure Monitoring
As the cake layer becomes thicker, the pressure drop across the filter increases. Sensors monitor this differential pressure to determine when cleaning is required.
4. Backflushing and Cleaning
When the pressure reaches a preset level, the system initiates a backflushing cycle using compressed air or clean liquid.
The reverse flow dislodges the accumulated cake from the candle surface.
5. Cake Discharge
The detached solids fall to the bottom of the vessel and are discharged through the outlet, after which the filtration cycle resumes.
Candle filtration systems are widely used in industries that require reliable solid-liquid separation and high product purity.
Common applications include:
• Chemical Processing
Removal of catalysts, activated carbon, and suspended solids from process streams.
• Pharmaceutical Manufacturing
Clarification of fermentation broth, recovery of biomass, and purification of pharmaceutical intermediates.
• Food and Beverage Production
Filtration of beverages such as juice, beer, and edible oils.
• Petrochemical and Refining
Removal of fine particles from fuels, lubricants, and process fluids.
Compared with traditional filtration systems, candle filters offer several operational benefits.
• High Filtration Precision
The cake filtration mechanism allows the removal of very fine particles.
• Closed-System Operation
The sealed vessel prevents contamination and reduces product loss.
• Automated Cleaning
Backflushing allows continuous operation without manual filter replacement.
• Large Filtration Area
Multiple candle elements provide a large effective filtration surface inside a compact vessel.
1. What is a candle filter used for?
A candle filter is used for solid–liquid separation in industrial processes, especially when fine particles must be removed from slurries or process liquids.
2. How does a candle filter remove particles?
The filter forces liquid through porous candle elements under pressure. Solid particles accumulate on the surface and form a filter cake, which improves filtration efficiency.
3. What materials are used for candle filter elements?
Candle filter elements are commonly made from sintered metal, stainless steel mesh, ceramic media, or polymer filter cloth, depending on process requirements.
4. What industries use candle filters?
Candle filters are widely used in chemical processing, pharmaceuticals, food and beverage production, petrochemical refining, and environmental filtration systems.
Related Reading: Candle Filter vs Cartridge Filter
