A candle filter, also known as a tubular filter, is a
type of pressure filter used for the
separation of solids from liquids, particularly in processes where high filtration
efficiency is
required. It is widely used in industries such as chemical processing,
pharmaceuticals, food
and beverage, and wastewater treatment.
Working Principle
- Introduction of Slurry: The slurry
or suspension containing solids and liquids is
introduced into the filter housing under pressure.
- Filtration: The slurry flows into
the candle filter elements, which are typically
cylindrical or tubular in shape. The filter elements are made of porous
materials,
such as sintered metal, ceramic, or synthetic fibers, which allow the liquid to
pass
through while retaining the solid particles on the surface or within the pores.
- Formation of Filter Cake: As the
filtration process continues, a layer of solid
particles, known as the filter cake, forms on the outer surface of the candle
elements. The thickness of the filter cake increases over time, enhancing the
filtration efficiency by capturing finer particles.
- Discharge of Filtrate: The
filtered liquid, now free of solids, passes through the
porous candle elements and is collected in the filtrate outlet. The clean
filtrate is
then discharged or sent for further processing.
- Cake Discharge: Once the filter
cake reaches the desired thickness or the filtration
cycle is complete, the filtration process is stopped. The filter cake is
typically
discharged by introducing gas or air into the filter housing, which helps to
loosen and
release the cake from the candle elements. The cake can then be removed manually
or automatically, depending on the system design.After the filter cake is
discharged,
the candle elements are cleaned, either by backwashing, chemical cleaning, or
other
cleaning methods, to restore their filtration capacity for the next cycle.
Features of Candle Filters
- High Filtration Efficiency: Candle
filters are capable of achieving very high filtration
efficiencies, making them suitable for applications requiring the removal of
fine
particles or for producing high-purity products.
- Pressure Filtration: Candle
filters operate under pressure, which allows for efficient
filtration even with viscous liquids or slurries with high solid content.
- Continuous or Batch Operation:
Depending on the design, candle filters can be used
in both continuous and batch filtration processes.
- Automatic Cake Discharge: Many
candle filters are designed for automatic cake
discharge, reducing manual intervention and improving process efficiency.
- Scalability: Candle filters are
available in various sizes and configurations, making
them scalable for different industrial applications, from small-scale laboratory
use to
large-scale industrial processes.
Applications of Candle Filters
- Chemical Processing: Used for the
filtration of acids, alkalis, and other chemicals
where high purity and efficient solid-liquid separation are required.
- Pharmaceuticals: Ensuring sterile
filtration of liquid pharmaceuticals and
biotechnology products.
- Food and Beverage: Clarification
of liquids such as wine, beer, edible oils, and juices.
- Water Treatment: Filtration of
industrial wastewater, drinking water, and other
water treatment applications