Filter Leaf:
Principle:
It is an apparatus consisting of a longitudinal drainage screen covered with a filter cloth.
The mechanism is surface filtration and acts as a sieve or strainer.
Vacuum or pressure can be applied to increase the rate of filtration
Construction:
The leaf filter consists of a frame enclosing a drainage screen or grooved plate.
The frame may be any shape circular, square or rectangular.
The whole unit is covered with filter cloth.
The outlet for the filtrate connects to the inside of the frame through suction.
Working:
The filter leaf is immersed in the slurry.
Vacuum system is connected to the outlet.
The slurry passes through the filter cloth.
Finally filtrate enters the drainage canal and goes through the outlet into the receiver.
Air is passed to flow in reverse direction which facilitates removal of cake
Advantages of filter leaf:
Simplest form of filter used for batch process.
A number of units can be connected in parallel to increase the surface area of filtration.
Pressure difference can be obtained either with vacuum or using pressure up to the order of 800 kilopascals.
Labor costs for operating the filter leaf are fairly moderate.
The efficiency of washing is high.
The slurry can be filtered from any vessel.
The cake can be washed simply by immersing the filter in a vessel of Water.
Disadvantages of filter leaf:
It is not a continuous process.
It is used where the proportion of solid in the liquid to be filtered is about 5% or less.