EXPERIMENT
PLATE
AND FILTER PRESS
1.
Objective
To evaluate specific cake
resistance, compressibility of the cake and explore the variables effecting the
filtration rate.
2. INTRODUCTION
Plate and frame filter press is the most fundamental design among all
the other filter presses and majority nowadays refer it as the membrane filter
plate. Many plates and frames are present in the plate and filter press and
presence of a centrifuge pump. The separating chambers consist of one hollow
filter frame separated from two filter plates by filter clothes. The introduced
slurry flows through a port in each individual frame, and the filter cakes are
accumulated in each the hollow frame. As the filter cake becoming thicker, the
filter resistance increases as well. So when the separating chamber is full,
the filtration process is stopped as the optimum pressure difference had
reached. The filtrate that passes through filter cloth are collected through
collection pipes and stored in the filter tank. Whereas filter cakes (suspended
solids) accumulation occurs at the hollow plate frame, then being separated at
the filter plates by pulling the plate and frame filter press apart. The cakes
would just fall off from those plates and being discharge to the final collection
point. Cake discharge can be done in many ways. For example: Shaking the plates
while they are being opened or shaking the cloths. Scraper can also be used, by
moving from one chamber to another and scrape the cake off the cloth. At the
end of each run, the cloth are cleaned using wash liquid and ready to start the
next cycle.
The
specific cake resistance is a defined as
ɑ
= 5((1-є)So2)/ ρє3
where,
є= cake porosity
ρ= density of dried cake
ɑ= specific cake
resistance
So=
Cake specific area
4. Procedure
Start-up
Procedure
Clean the vessel, plate
and frames and the scrap out the residuals on the filter medium. Make sure all
the valves are closed. Set the plate and frame alternatively in the rack, cover
the frame with the filter cloth in such a way that the holes are parallel to
each other. Then close the press by rotating the wheel. Make sure it is tightly
packed. Take 2.8 kg of CaCO3 powder and 25.2 L of water. Fill the
vessel with this amount of water. Switch on the power supply and the agitator
knob. Slowly add the powder into the vessel. Switch on the feed pump and open
the feed valve, so that the mixing becomes easy. Let it mix for 10-15 mins.
Performing
the Experiment
After the mixing is done,
partially close the feed valve and open the filter-press valve. The slurry will
start flowing into the inlet ducts and the filtrate will start to flow out
through the bottom duct. Set a time limit and measure the amount of filtrate
coming out. This flow will be continuous. The pressure gauge will start to
fluctuate. Note down this reading. It will become constant in a while. some
amount of water collecting in the tray below the rails, Measure this too. These
are the losses. After a couple of hours the filtrate will abruptly stop
flowing, this is the end of your experiment. Switch off all the pumps and
disconnect the power supply. Open the closing device and release the pressure.
Slowly remove the frame from the rack, and flip open the filter cloth. Remove
the wet cake from the frame by shaking it a little. Let it dry for a couple of
hours and weigh the mass of the dry filter cake.
Shut-down
procedure
Wash the frame with clean
water. Collect the slurry in the agitating vessel and measure its amount. It is
the unused slurry. Clean the vessel with fresh water and drain it away.
