filtration & centrifugation

FILTRATION & CENTRIFUGATIONMECHANICAL – PHYSICAL SEPARATION PROCESS

MECHANICAL – PHYSICAL SEPARATION PROCESSFILTRATION

CENTRIFUGATION

SETTLING AND SEDIMENTATIPN

MECHANICAL SIZE REDUCTION & SEPARATION

FILTRATIONSolid particles are removed from theslurry by forcing the fluid through a filtermedium, which blocks the passage ofthe solid particles and allows the filtrateto pass through.

Pressure difference is set up andcauses the fluid to flow through smallholes of the screen or cloth whichblock the passage of the large solidparticles, which, in turn, build up on thecloth as a porous cake.

CENTRIFUGATIONSimilar to ordinary filtration where abed or cake of solids builds up on ascreen, but centrifugal force is used tocause the flow instead of a pressuredifference.

PROBLEM 1What is the porosity of a solid if its bulk density is 1125 kg/m3 and its true density is 1500 kg/m3?

POROSITY (Ɛ)

PROBLEM 1 (cont.)

PROBLEM 2Given the following data on filter cake (CaCO3) from plate and frame filter press:◦ Thickness of cake: 1 inch

◦ Weight of the cake: 2.7 lbs

◦ Dimensions of cake: 7 x 8 inch

◦ Density if CaCO3: 183 lb/ft3

The porosity of the cake is

PROBLEM 2 (cont.)

FILTRATION

FILTRATION

FILTRATION

FILTRATION

FILTRATION

CONSTANT PRESSURE FILTRATION

CONSTANT PRESSURE FILTRATION

CONSTANT PRESSURE FILTRATION

CONSTANT RATE FILTRATION

CONSTANT RATE FILTRATION

CONSTANT PRESSURE FILTRATIONPRECEEDED BY CONSTANT RATE FILTRATION

CONSTANT PRESSURE FILTRATIONPRECEEDED BY CONSTANT RATE FILTRATION

PROBLEM 3Volume of the filtrate collected is 1 gal when the filtration rate is 1.5 gpm, and it is 5 gal when the filtration rate is 0.6 gpm. Calculate the volume collected when the filtration rate is 0.75 gpm. What is the total volume collected in 10 min? Assume constant-pressure filtration.

PROBLEM 3 (cont.)

PROBLEM 3 (cont.)

PROBLEM 3 (cont.)

PROBLEM 4In the filtration of Al(OH)3 the following data were obtained:◦ The pump is operated at maximum

capacity (P=50psia);

◦ Filtration was completed at constant rate pressure;

◦ Constant rate operation time is 15 min and 1/3 of the total volume is obtained during this period.

Given the above, the total filtration time is

PROBLEM 4 (cont.)

PROBLEM 5If only ½ of the original filtrate volume of the above problem were to be collected with the area remaining unchanged, the new filtration time is

PROBLEM 5 (cont.)

CENTRIFUGATION

CENTRIFUGATION

PROBLEM 6The capacity in cubic meters per hour of a clarifying centrifuge operating under these conditions is?◦ Diameter of bowl = 600 mm

◦ Thickness of liquid layer = 75 mm

◦ Depth of bowl = 400 mm

◦ Speed = 1200r/min

◦ Specific gravity of liquid = 1.2

◦ Specific gravity of solid = 1.6

◦ Viscosity of liquid = 2 cp

◦ Cut size of particles = 30 microns

PROBLEM 6 (cont.)

BASKET CENTRIFUGAL FILTER

BASKET CENTRIFUGAL FILTER

BASKET CENTRIFUGAL FILTER

PROBLEM 7A batch centrifugal filter having a bowl diameter of 750 mm and a bowl height of 450 mm is used to filter a suspension having the following properties:◦ Temperature: liquid, water = 25°C

◦ Porosity of cake = 0.435

◦ Final thickness of cake = 150 mm

◦ Specific cake resistance = 9.5 E 10 ft/lb

◦ Filter medium resistance = 2.6 E 10 per ft

◦ Speed of the centrifuge = 2000 rpm

◦ Concentration of solids in feed = 60 g/L

◦ Density of dry solid in cake = 2000 kg/m3

The final cake is washed with water under such conditions that the radius of the inner surface of the liquid is 200 mm. Assuming that the rate of flow of wash water equals the final rate of flow of filtrate, the rate of washing is m3/hr is

PROBLEM 7 (cont.)

PROBLEM 7 (cont.)

PROBLEM 7 (cont.)

PROBLEM 7 (cont.)

PLATE&FRAME FILTER PRESS andLEAF FILTER

PLATE&FRAME FILTER PRESS andLEAF FILTER