To study the performance of a rotary drum filter operating under vacuum. AIM:
To determine the specific cake resistance (α) for a given slurry of CaCO3. INTRODUCTION:
A most common type of continuous vacuum filter is the rotary drum filter, which consists up a horizontal drum with a slotted face turns at a speed of 0.1 to 2 rev/min in an agitated slurry trough a filter medium such as canvas covers the face of the drum., which is partly submersed in the liquid. Under cylindrical face of the main drum is a second smaller drum with a solid surface. Between two drums are radial partitions dividing the annular space into separate compartments. Due to vacuum applied inside the drum, the filtrate is drawn in through the filter medium and the cake is deposited on the outer surface of the drum THEORY:
In a continuous rotary drum filter, the feed, filtrate and cake moves at steady constant rates. For any particular element of the filter surface, however, conditions are not steady but
MECHANICAL OPERATIONS LABORATORY MANUAL For one full rotation of the drum:
∆P= pressure drop, Pa μ= viscosity of filtrate, kg/ms
Cs= concentration of solids in the slurry kg/m m = F mass
of wet cake g
3
MECHANICAL OPERATIONS LABORATORY MANUAL
DESCRIPTION:
The set-up consists of stainless steel ram moving in gunmetal brackets. The drum is divided in 6 compartments, covered by a SS mesh. A canvas filter is used for filtration. The whole assembly is fitted with a SS trough in which an agitator is provided. To make the unit a self-contained a slurry mixing and feed arrangement, receiver tanks, vacuum pump, control panel are provided. UTILITIES R EQUIRED:
Electricity Supply: Single Phase, 220 V AC, 50 Hz, 5-15 Amp combined socket with earth connection.
Water Supply: Continuous @ 2 LPM at 1 Bar. CaCO3: 10 kg
EXPERIMENTAL P ROCEDURE: STARTING P ROCEDURE:
Prepare feed solution by mixing 10 kg of calcium carbonate in 40 liter of water. Note down the mass of calcium carbonate and volume of water. Ensure that switches given on the panel are at OFF position.
MECHANICAL OPERATIONS LABORATORY MANUAL
Record the height of filtrate collected in the filtrate tank and time.
When filtrate tank-1 is completely fill up then close the valve V 6 and V7.
Chose the filtrate tank-2 and adjust the valve V 8 to set pressure same as filtrate tank-1. Open the valve V 9 and create the vacuum line. Wait for the completion of process. Allow air to enter the drum by open the valve V 5 and stop the vacuum pump. Collect the wet cake deposited per revolution of the drum. Remove the cake deposited. Repeat the experiment for different pressure.
CLOSING P ROCEDURE:
When experiment is over switch OFF the stirrer and pump.
Switch OFF the main power supply.
Drain the filtrate tank-1 by open the valve V10.
Drain the filtrate tank-2 by open the valve V11. Drain the rotary drum assembly by open the valve V12. Drain the slurry tank by open the valve V13. Wash the filter assembly properly
OBSERVATION & CALCULATION:
MECHANICAL OPERATIONS LABORATORY MANUAL
Plot the graph of ∆t/∆V Vs V and find slope “Kp” and intercept “B”. K p = B
=
6 (sec/m ) 3 (sec/m )
Wt of
Watch
Watch
Wet cake
Dry
empty
glass +wet
glass +dry
(g)
cake(g)
watch
cake (g)
cake (g)
glass(g)
Find α from the above eqn
C kg /m 3
α m/kg
R m m-1
MECHANICAL OPERATIONS LABORATORY MANUAL h
Height of filtrate collected in time t
cm
Measured
L
Length of drum
m
Given
m
Mass of calcium carbonate in feed slurry
Measured
n
Speed of drum
kg sec-
P
Pressure
∆P
Pressure drop (vacuum gauge reading)
mm of Hg
Calculated
t
Time of filtration
sec
Measured
V
Volume of the filtrate
m
Calculated
V1
Volume of water in feed slurry
Lit
Measured
m/kg
Calculated
N sec/m²
Given
α
Specific cake resistance of filtrate
μ
Viscosity of filtrate
PRECAUTION & MAINTENANCE I NSTRUCTIONS:
Measured
N/m
* Symbols represent unitless quantity.
Measured
Proper cleaning is must of drum and its clothes. Feed slurry is filtered before feeding it into the tank. Low flow is best for operating it. Vacuum pump connections should be correct & properly tight. Vent valve V5 of rotary drum should be close during the operation.
TROUBLESHOOTING:
If the slurry is overflow from the drum slow down the feed inlet rate.
