filtration report

1

FILTRATION

OBJECTIVE:

• To study the theory of filtration

• To determine the average cake resistance for the given slurry and the resistance of the

filter medium used in the filtration process.

• To determine the time for filtration and hence the performance of the equipment based on

the volume of the filtrate collected.

THEORETICAL STUDY:

INTRODUCTION:

The separation of particles is done on the basis of the state of the particles to be

separated. There are a group of separation techniques where the separation is accomplished by

the differences in the mechanical- physical forces in the system and not the molecular/ chemical

forces. These mechanical- physical forces act on the particles, liquids, or the mixtures of

particles and the liquids and not necessarily on the individual molecules.

Filtration is the removal of solid particles from a fluid by passing the fluid through a

filtering medium, or septum, on which the solids are deposited. Filtration is the most common

application of the flow of fluids through packed beds. It is analogous to the filtration carried out

using a filter paper on a funnel or using a Buckner funnel in a laboratory. The objective is to

separate the solid from the fluid in which it is present. The separation is carried out by forcing

the fluid through the porous membrane. The solid particles are trapped within the pores of the

membrane and a build up as a layer is seen on the surface of the membrane.

Industrial filtrations range from simple straining to highly complex separations. The fluid

may be a liquid or a gas; the valuable stream from the filter may be the fluid, or the solids or

both. Sometimes it is neither, as when waste solids may be separated from the waste liquid prior

to disposal. In industrial filtrations, the solid content ranges from a trace to a very high

percentage. Often the feed is subjected to a pretreatment process to increase the filtration rate,

as by heating recrystallizing, or by adding filter aids.

2

CLASSIFICATIONS:

Process Phase Separation

Filtration Liquid – Solid Pressure reduction

Centrifugation Liquid – Solid & Liquid – Liquid Centrifugal force

Sedimentation Liquid – Solid Gravity

cyclone separator Gas – Solid & Gas – Liquid Flow

Electrostatic precipitator Gas – Solid Electric field

Magnetic separator Solid – Solid & Solid – Liquid Magnetic field

Screening

Solid – Solid

Size of particles

Industrial Filters:

The classification of different equipments according to the different driving forces

are listed below

• Pressure filters

� Plate and frame filter press

� Leaf filter

� Sparkler filter

� Candle filter

� Line, Cartridge filter

• Vacuum filters

� Nutsche filter

� Rotary Drum filters

• Centrifugal filters

� Top driven centrifuge

� Bottom driven centrifuge

3

Mechanisms of filtration:

a) Cake filter b) Clarifying filter c) Cross- flow filter

• Cake filters separate relatively large amounts of solids as a cake or crystals or sludge.

Often they include provisions for washing the cake and removing some of the liquids

form the solids before discharge.

• Clarifying filters remove small amounts of solids to produce a clean gas or sparkling

clear liquids, like beverages. The solid particles are trapped in the filter medium as

shown. Clarifying filters differ from screens in that the pores in the filter medium are

much larger in diameter than the particles to be removed.

• In a Cross-flow filter the feed suspension flows under pressure at a very high velocity

across the filter medium. A thin layer of solids may form on the surface of the medium

but the high liquid velocity keeps the layer from building up. The filter medium may be

ceramic, metal or a polymer membrane with pores small enough to exclude most of the

suspended particles. Some liquid passes as a clear filtrate and leaves behind a suspension

of solids.

4

CAKE FILTRATION:

In cake filtration, the filter cloth often acts as no more than a substrate

for building up the first thin layers of the filter cake, which itself then acts a filter to trap more

and more particles of smaller and smaller size. The first particles form bridges over the pores of

the medium. After this, smaller particles pass through the filter cloth, leading to a turbid liquid

(filtrate). As soon as the first layer of the particles has accumulated on the filter medium, this

cake will then act as the actual filter medium. The first solid particles enter the pores of the

medium and are immobilized, but soon others begin to collect on the septum surface. After the

brief initial period, a cake of apparent thickness builds up on the surface and must be

periodically removed. Naturally, the pressure drop through the filter cake increases and flow

decreases as the filter cake gets thicker. If the slurry contains too many fines, all pores of the

cloth may become blocked.

DERIVATION:

PRESURE DROP OF FLUID THROUGH THE FILTER CAKE:

The solid-fluid suspension to be filtered is passed under pressure through a

medium which allows the flow of the suspending fluid but retains the suspended particles to

form a cake of the upstream side of the

medium.

At time ‘t’ sec,

thickness of cake = L m

filter cross-sectional area = A m2

linear velocity for flow = v m/s for A m2

Section through a filter medium at definite

time ‘t’ sec from the start of filtration

For laminar flow, in a packed bed of particles, the Carman-Kozeny relation has been

shown to apply to filtration. It is given by,

…1

5

where, ∆pc -> Pressure drop across the cake in N/m2 (lbf/ft2)

ν -> Open tube velocity in m/s (ft/s)

D -> Diameter in m (ft)

L -> Length in m (ft)

µ -> Viscosity in Pa.s or kg/m.s (lbm/ft.s)

k1 -> constant = 4.17 for random particles of definite size and shape

ε -> Void fraction or porosity of cake

S0 -> Specific surface area of particle in m2 per volume of solid particle

The linear velocity depends on cross sectional are according to the relation,

where, A -> filter area in m2 (ft 2)

V -> total m3 (ft3) volume of filtrate collected upto time ‘t’ sec

The cake thickness ‘L’ is related to volume by Material Balance

where, Cs -> kg solids /m3 (lbm/ft3) of filtrate

ρp -> density of solid particles in the cake in kg/m3 (lbm/ft3) solid

The final term of this equation is the volume of filtrate held in the cake. This is usually small and neglected.

Substituting Eq. 2 in Eq. 1, using Eq. 3 to eliminate L, we get,

…2

…3

6

where, α -> Specific cake resistance in m/kg (ft/lbm), given by

For filter medium resistance,

where, Rm -> Resistance of the filter medium to filtrate flow ( m-1)

Rm is an empirical constant that includes the resistance to flow of the piping leads to and

from the filter and the filter medium resistance.

As α and Rm are in series,

where,

The volume of the filtrate V can be related to W, the kg of accumulated dry cake solids, as

where, Cx -> mass fraction of the solids in the slurry

m -> mass ratio of dry cake to wet cake

ρ -> density of filtrate in kg/m3

Specific Cake Resistance:

Specific cake resistance is a function of void fraction ε and S0. It is also a function of pressure as

pressure can affect ε. By conducting various experiments at various pressure drops, the variation

of α with ∆p can be calculated.

If α is independent of -∆p, then the sludge is incompressible. Usually, α increases with –∆p,

since most cakes are somewhat compressible.

7

An empirical equation is often used as,

where αo and s are empirical constants. The compressibility constant s is zero, for incompressible

cakes. Usually, it varies between 0.1 and 0.8 .

Constant Pressure Conditions:

For a Batch process,

where, Kp is in s/m6 and B is in s/m3

For constant pressure, constant α, and incompressible cake, V and t are the only variables.

Integrating to obtain the time of filtration in t s,

Dividing by V,

The plot of t/V Vs V gives a straight

line with an intercept.

The slope gives Kp and the intercept

gives B.

8

Constant Rate Conditions:

These conditions are attained if the slurry is fed to the filter by a positive

displacement pump. Here, the flow rate of the slurry through the filter medium is kept a

constant.

where,

where Kv is in N/m5 ,

C is in N/m2.

Assuming that the cake is incompressible, Kv and C are constants characteristic of the slurry, cake, rate of the filtrate collected. A plot of pressure –∆p Vs V, the total volume of the filtrate collected, gives a straight line for a constant rate dV/dt. The slope of the line is Kv and the intercept is C. The pressure increases as the cake thickness increases and as the volume of the filtrate collected increases. The equations can also be rearranged in terms of –∆p and time ‘t’ as variables. At any moment during the filtration, the total volume V is related to the rate and total time t as,

Substituting in the first equation,

For a case when the specific cake resistance is not a constant, but varies as

this can be substituted as the value for α to obtain a final equation.

9

CENTRIFUGAL SEPARATION PROCESS:

Centrifugal settling or sedimentation:

Sometimes gravity settling may be too slow because of the closeness of the densities of

the particles and the fluid, or because of forces holding the particles together as in the case of

emulsions. In such cases, centrifugal separation is employed.

Forces developed in centrifugal separation:

Centrifugal separators make use of the principle that an object whirled about an axis or centre point at a constant radial distance from the point is acted on by a force. The object being whirled about an axis is constantly changing direction and is thus accelerating, even though the rotational speed is constant. This centripetal force acts in a direction toward the centre of rotation.

If the object the object being rotated is a cylindrical container, the contents of fluid and solids exert an equal and opposite force, called centrifugal force, outward to the to the walls of the container. This is the force that causes settling or sedimentation of particles through a layer of liquid through a bed of filter cake held inside a perforated rotating chamber.

Here, a cylindrical bowl is shown rotating with a slurry feed of solid particles and liquid being admitted at the centre. The feed enters and is immediately thrown outward to the walls of the container, as in section (b). The liquid and solids are now acted upon by the vertical gravitational force and the horizontal centrifugal force. The centrifugal force is usually so large that the force of gravity may be neglected. The liquid layer then assumes the equilibrium position with the surface almost vertical. The particles settle horizontally outward and press against the vertical bowl wall.

In section (c) two liquids having different densities are being separated by the centrifuge. The more dense fluid will occupy the outer periphery, since the centrifugal force is greater on the more dense fluid.

10

Equations for Centrifugal forces:

In circular motion, the acceleration from the centrifugal force is

where, ac -> acceleration due to the centrifugal force in m/s2

r -> radial distance from centre of rotation in m

ω -> angular velocity in rad/s

The centrifugal force Fc in N, acting on the particle is given by

ince ω = ν/r, where ν is the tangential velocity of the particle in m/s

Often rotational speeds are given as N rev/in and

and

Substituting

The gravitational force on a particle is given by,

where, g is the acceleration of gravity = 9.80665 m/s2

In terms of gravity force, the centrifugal force is given as

Hence, the force developed is r ω2/g times gravity force. This is expressed as equivalent to so

many g forces.

11

Equations for rates of settling in centrifuges:

General equation for settling:

If a centrifuge is used for sedimentation (removal of particles by settling), a particle of a

given size can be removed from the liquid in the bow if sufficient residence time of the particle

in the bowl is available for the particle to reach the wall. For a particle moving radially at its

terminal setting velocity, the diameter of the smallest particle removed can be calculated.

The feed enters at the bottom and it is assumed all the liquid moves upward at a uniform velocity, carrying solid particles with it. The particle is assumed to be moving radially at its terminal settling velocity vt. The trajectory or path of the particle is shown in the above figure. A particle of a given size is removed from the liquid if sufficient residence time is available for the particle to reach the wall of the bowl, where it is held. The length of the bowl is b m.

At the end of the residence time of the particle in fluid, the particle is at a distance rb m from the axis of rotation. If rb < r2, then the particle leaves the bowl with the fluid. If rb = r2 , it is deposited on the wall of the bowl and effectively removed from the liquid.

For settling in the stokes’ law range, the terminal settling velocity at a radius r is obtained by,

where, Vt -> Settling velocity in the radial direction in m/s

Dp -> Particle diameter in m

ρp -> Particle density in kg/m3

ρ -> Liquid density in kg/m3

µ -> Liquid viscosity in Pa.s

If hindered settling occurs, the RHS of the above equation is multiplied by the factor (ε2Ψp).

12

Since,

Integrating between limits r=r1 at t=0 and r=r2 at t=tr

The residence time tr is equat to the volume of liquid V m3 in th bowl divided by the feed volumetric flow rate q in m3/s. The volume V is given by,

Substituting and solving for q,

Particles having diameters smaller than that calculated, will not reach the wall of the bowl and will go out with the exit liquid. Larger particles will reach the wall and be removed from the liquid.

The critical diameter Dpc is be defined as the diameter of a

particle that reaches ½ the distance between r1 and r2. This particle moves a distance of half the liquid layer or (r2-r1)/2 during the time this particle is in the centrifuge.

The integration is then between r = (r1+r2)/2 at t = 0 and r = r2 at t = tr.

Then we obtain,

At this flow rate qc, particles with a diagram greater than Dpc will predominantly settle to the wall and most smaller particles will remain in the liquid.

13

Sigma values and scale-up of centrifuges:

A useful characteristic of a tubular-bowl centrifuge can be expressed as,

where νt is the terminal settling velocity of the particle in a gravitational field

Σ is physical characteristic of the centrifuge and not of the fluid- particle syste, being separated. For a special case of settling of a thin layer,

The value of Σ is really the area in m2 of a gravitational settler that will have the same sedimentation characteristics as the centrifuge for the same feed rate. To scale up from a laboratory test of q1 and Σ1 to q2 ( for νi 1 = νi 2 ),

This scale-up procedure is dependable for similar type and geometry centrifuges and if the centrifugal forces are within a factor of 2 from each other. If different configurations are used, efficiency factors E should be used where q1/Σ1E1 = q2Σ2E2 . These efficiencies are determined experimentally and values for different types of centrifuges are available.

Co- relation with the cake filtration theory:

The theory of constant pressure filtration can be modified and used where the centrifugal force

causes the flow instead of the impressed pressure difference. The equation will be derived for the

case where a cake has already been deposited. The inside radius of the basket is r2, ri is the inner

radius of the face of the cake, and r1 is the inner radius of the liquid surface. We will assume that

the cake is nearly incompressible so that an average value of α can be used for the cake. Also the

flow is laminar. If we assume a thin cake in a large-diameter centrifuge, then the area A for flow

is approximately constant. The velocity of the liquid is,

14

where q is the filtrate flow rate in m3/s and v is the velocity.

From the above we get,

where mc = csV , mass of cake in kg deposited on the filter.

For a hydraulic head of dz m, the pressure drop is

In a centrifugal field, g is replaced by rω2 and dz by dr. Then,

Integrating between r1 and r2,

Combining the equations and solving for q,

For the case where the flow area A varies considerably with the radius, the following has been

derived

Where A2 =2πr2b (area of filter medium), Āl=2πb(r2-ri)/ln(r2/ri) (logarithmic cake area),

and Āa=(ri+r2)πb (arithmetic mean cake area).

This equation holds for a cake of a given mass at a given time.

15

FILTER MEDIUM:

It is defined as a material that is permeable to one or more components of a

mixture, solution or suspension, and is impermeable to remaining components. Its principal role

is to cause a clear separation of particulates from the fluid with minimum consumption of

energy.

Properties of filter media:

Filtration Properties Filter oriented properties Feed oriented properties

Particle retention Ability to be fabricated Chemical/thermal stability

Flow resistance Resistance to stretch Biological stability

Dirt holding capacity Vibrational stability Ad/absorptive characteristics

Tendency to blind Rigidity Disposability

Cake discharge characteristics Strength Re-use

Types of filter media used:

1. Woven fabrics � Natural like cotton, wool � Synthetic includes polymers, metal carbons

2. Non woven media

� Felts and needlefelts � Paper (cellulose and glass) � Filter sheets

3. Metal sheets

� Perforated � Woven wire

4. Rigid porous media

� Ceramics and stoneware � Carbon � Sintered metals

5. Plastic sheets

� Woven monofilaments

� Fibrillated film

� Porous sheets

16

6. Membranes

� Polymeric

� Ceramic

� Metal

7. Cartridges

� Sheet fabrications

� Bonded beds

� Yarn wound

FILTER AIDS:

It is frequently necessary to modify the slurry in order to provide an acceptable filtration

rate, washing rate, or final cake moisture content. The most common treatment is the addition of

flocculating agents. Filter aids are non-compressible particulate substances that are either mixed

with the product slurry to improve filtration rate and reduce cloth blinding, or laid down to pre-

coat the filter before the slurry is introduced to improve retention of fine particles.

They are granular or fibrous solids capable of forming a highly permeable filter cake in which

very fine solids are trapped. Application of filter aids allows the use of a much more permeable

filter medium than would be provided by depth filtration.

Properties of Filter Aids:

� Filter aids should have low bulk density to minimize settling and aid

good distribution on the filter-medium surface.

� They should be porous and capable of forming a porous cake

to minimize flow resistance.

� They must be chemically inert to the filtrate.

Examples:

• Diatomaceous earth (also called diatomite), which is an almost pure silica.

• Expanded perlite, particles of “puffed” lava that are principally

aluminum alkali silicate.

• Cellulosic fibers (ground wood pulp) are sometimes

used when siliceous materials cannot be used.

• Carbon, Gypsum, salt, Fine sand, Starch, and precipitated CaCO3.

17

LAB – SCALE EXPERIMENT: (CONSTANT PRESSURE PROCESS)

OBJECTIVE:

• To determine the average cake resistance for the given slurry and the resistance of the

filter medium used in the constant pressure filtration process.

• To determine the rating of the equipment, given the volume of the filtrate to be collected.

APPARATUS REQUIRED:

Sample to be filtered, pressure filtration set- up – Buchner funnel, filter medium of appropriate

pore size, purified water for cleaning purposes

THEORY:

In filtration, suspended solids in a fluid of liquid or gas are removed by

using a porous medium that retains the particles as a separate phase or cake and passes the clear

filtrate. The laboratory filtration is performed using a Buchner funnel. The liquid is caused to

flow though the filter cloth by a vacuum at the exit end.

The slurry consists of the liquid and the suspended particles. The passage of the particles is

blocked by the small openings in the exit of the filter cloth. A support with relatively large holes

is used to support the filter cloth. Solid particles build up in the form of a filter cake. The cake

itself acts as a filter. The cake thickness increases with time. As the cakes builds up, the

resistance to flow also increases.

18

From the derivation of the Pressure drop through the filter cake,

This equation is in the form of a straight line, y = mx + c, where Kp is the slope of the straight

line and B is the intercept of the line in the y - axis.

A plot of t/V vs V thus, gives a straight line, from which the values of Kp and B can be

calculated. Substitution of these values in the above expressions gives the values of α and Rm.

ASSUMPTIONS MADE:

• There is negligible solid motion, that is, the solid phase velocity is considered zero.

• There is a constant and time invariant wet to dry cake mass ratio in the slurry, that is, the

concentration of the solids in the slurry is a constant.

• Absolute vacuum conditions are assumed through the entire filtration process

• Rm is a constant throughout the filtration process

• The properties of the newly formed cake layer (concentration and specific resistance) are similar to the average filter cake properties.

EXPERIMENTAL PROCEDURE:

1) Settling Test:

Allow about 1 liter of slurry to settle on the lab bench in a beaker.

The material should settle and produce a clear liquor phase in less than 30 minutes.

If the slurry remains cloudy for 30 minutes or more, the product will probably be difficult to

isolate. The crystallization conditions may have to be altered to increase particle size or reduce

fines.

19

2) Cake Permeability Test:

• Filter the slurry sample through a Buchner funnel with vacuum to obtain a filter cake

about 2" thick.

• Measure the rate at which the clear ML is filtered through the cake.

• If the liquors filter at a rate of 1 gpm/ft2 of filter area or greater, then it is a good

candidate for centrifugation or other large-scale filtration. If the liquor filtration rate

is less than 0.5 gpm/ft2, it means that the slurry contains too many fines, or that the

product is amorphous (noncrystalline) in nature and too easily compressed to allow

liquid to drain through. Again, a change in crystallization conditions may be required.

3) Measuring Filtration data:

• Determine the solid concentration in the slurry sample before carrying the filtration

tests.

• Pour the sample into the funnel and apply vacuum to the container

• Measure the volume of filtrate collected at various time intervals. The intervals may

be increased progressively to compensate for the drop in the filtrate flow rate.

• Remove the cake from the filter and dry it and weigh it. This can also be used for the

calculation of the concentration of the dry solids in the sample.

• The plot of time and filtrate data gives the desired parameters characteristic of the

slurry.

PRECAUTIONS:

� The cake should not crack at any point. The filtration should be stopped if a crack is

observed in the filter cake.

� Do not allow the cake to completely drain before adding more slurry.

� The slurry should be kept as homogeneous as possible during the test.

� The initial tests should be performed to check the amount of fines in the slurry.

� The concentration of the solids in the slurry should be calculated initially before the

experiment.

� The rate at which the slurry is added into the funnel should not be altered too much so

a smooth graph can be obtained.

� If the filtration pressure is increased too quickly, the filtration rate will increase too

fast. This should be avoided.

� The selection of the filter medium should be done with the knowledge of the

suspension characteristics of the slurry.

20

GRAPHS AND CALCULATIONS:

COMPOUND 2

TIME t (sec) t/V VOLUME V (Ml)

8 0.160 50

12 0.120 100

22 0.147 150

25 0.125 200

40 0.160 250

56 0.187 300

75 0.214 350

92 0.230 400

115 0.256 450

147 0.294 500

175 0.318 550

203 0.338 600

236 0.363 650

283 0.404 700

345 0.460 750

385 0.497 775

COMPOUND-2

0.000

0.030

0.060

0.090

0.120

0.150

0.180

0.210

0.240

0.270

0.300

0.330

0.360

0.390

0.420

0.450

0.480

0.510

0.540

50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 775

Volume

t/V

From the graph,

Kp = 1.06 * 10-5 B = 0.02

21

where

µ -> Viscosity in Pa.s or kg/m.s = 1 centi Poise = 1 * 10-3 Pa.sec

A -> filter area in m2 = ( 3.14) r2 = 0. 0095 m2

∆pc -> Pressure drop across the cake in N/m2 = 95.99 kPa

Cs -> kg solids /m3 of filtrate

α -> Specific cake resistance in m/kg

Rm -> Resistance of the filter medium to filtrate flow (m-1)

Cs = 7.86 % w / w

Assume 100 kg of slurry

7.86 kg of solid corresponds to 100 kg of slurry

7.86 kg of solid corresponds to 92.14 kg of ML

Density of ML = 850 kg/m3

Volume of ML = 92.14/ 850

= 0.1084 m3

7.86 kg of wet cake corresponds to 0.1084 m3 of ML

175 kg of wet cake corresponds to 2.4134 m3 of ML which equals 170 kg of dry cake

Cs = 170 kg of dry cake / 2.4134 m3 of ML

= 70.44 kg/ m3 of ML

Substituting in the equations of Kp and B,

α = 1.3036 * 10-3 m/kg

Rm = 1.8238 * 103 m-1

22

COMPOUND 4

Total time 111 secs

TIME t (sec) VOLUME V (Ml) t/V

7 100 0.070

10 200 0.050

14 250 0.056

19 300 0.063

22 400 0.055

26 450 0.058

28 500 0.056

34 550 0.062

36 600 0.060

46 700 0.066

55 800 0.069

70 850 0.082

COMPOUND-4

0.000

0.010

0.020

0.030

0.040

0.050

0.060

0.070

0.080

0.090

100 250 400 500 600 800Volume

t/V

From the graph,

Kp = 6.71 * 10-5 B = 0.041

23

where

µ -> Viscosity in Pa.s or kg/m.s = 1 centi Poise = 10-3 Pa.sec






Cs = 10 % w / w


10 kg of solid corresponds to 100 kg of slurry

10 kg of solid corresponds to 90 kg of ML


Volume of ML = 90 / 900

= 0.10 m3

10 kg of wet cake corresponds to 0.10 m3 of ML



= 88.5714 kg/ m3 of ML


α = 6.563 * 10-3 m/kg

Rm = 3.7388 * 103 m-1

24

COMPUOND 5

TIME t (sec) VOLUME V (Ml) t/V

7 100 0.070

10 150 0.067

13 200 0.065

20 300 0.067

25 350 0.071

28 400 0.070

34 450 0.076

36 500 0.072

42 550 0.076

48 600 0.080

53 650 0.082

70 700 0.100

80 750 0.107

COMPOUND -5

0.000

0.020

0.040

0.060

0.080

0.100

0.120

100 200 350 450 550 650 750V

t/V

From the graph,

Kp = 2.074 * 10 -4 B = 0.040

25

where

µ -> Viscosity in Pa.s or kg/m.s = 0.6 centi Poise = .6 * 10-3 Pa.sec

A -> filter area in m2 = ( 3.14) r2 = 0.0095 m2

∆pc -> Pressure drop across the cake in N/m2 = 95.99k Pa




Cs = 11.60 % w / w





Volume of ML = 88.4 / 800

= 0.1105 m3




= 83.98 kg/ m3 of ML


α = 3.567 * 10-3 m/kg

Rm = 3.647 * 103 m-1

26

COMPOUND 6

TIME t (sec) VOLUME V

(Ml) t/V

7 100 0.070

10 250 0.040

13 300 0.043

17 400 0.043

20 450 0.044

24 500 0.048

27 550 0.049

31 600 0.052

35 650 0.054

41 700 0.059

46 750 0.061

51 800 0.064

61 850 0.072

70 900 0.078

80 950 0.084

103 1000 0.103

COMPOUND-6

0.000

0.010

0.020

0.030

0.040

0.050

0.060

0.070

0.080

0.090

0.100

0.110

100 250 300 400 450 500 550 600 650 700 750 800 850 900 950 1000

V

t/V

From the graph,

Kp = 1.05 * 10-4 B = 0.028

27

where

µ -> Viscosity in Pa.s or kg/m.s = 0.37 cPoise = 0.37 * 10-3 Pa.sec






Cs = 9.25 % w / w





Volume of ML = 90.75 / 800

= 0.1134 m3




= 48.91 kg/ m3 of ML


α = 5.0265 * 10-2 m/kg

Rm = 6.9 * 104 m-1

28

COMPOUND 7

[2 FILTER CLOTHS]


(Ml) t/V

10 100 0.100

14 200 0.070

18 250 0.072

25 300 0.083

34 350 0.097

80 600 0.133

86 650 0.132

90 700 0.129

108 750 0.144

117 800 0.146

150 825 0.182

COMPOUND-7

0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

0.160

0.180

0.200

100 200 250 300 350 600 650 700 750 800 825

V

t/V

From the graph,

Kp = 3.5 * 10 -4 B = 0.03

where

29



∆pc -> Pressure drop across the cake in N/ m2 = 95.99 kPa




Cs = 1.55 % w / w





Volume of ML = 98.45 / 800

= 0.123 m3 of ML




= 10.2386 kg/ m3 of ML


α = 49.35 m/kg

Rm = 4.559 * 104 m-1

30

COMPOUND 8

[2 FILTER CLOTHS]


(Ml) t/V

13 100 0.130

20 150 0.133

24 200 0.120

31 250 0.124

40 300 0.133

52 350 0.149

62 400 0.155

68 450 0.151

75 500 0.150

88 550 0.160

95 600 0.158

110 650 0.169

118 675 0.175

125 700 0.179

150 750 0.200

COMPOUND-8

0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

0.160

0.180

0.200

0.220

100 200 300 400 500 600 675 750V

t/V

From the graph,

Kp = 2.16 * 10 -4 B = 0.105

31

where







Cs = 11.21 % w / w





Volume of ML = 88.79 / 900

= 0.09865 m3


240 kg of wet cake corresponds to 2.112 m3 of ML

Cs = 240 kg / 3.68 m3 of ML

= 113.636 kg/ m3 of ML


α = 1.6466 * 10-4 m/kg

Rm = 9.575 * 104 m-1

32

COMPOUND 9

[2 FILTER CLOTHS]


(Ml) t/V

9 100 0.090

12 150 0.080

16 200 0.080

22 250 0.088

27 300 0.090

31 350 0.089

36 400 0.090

40 450 0.089

47 500 0.094

52 550 0.095

59 600 0.098

68 650 0.105

79 700 0.113

87 750 0.116

93 775 0.120

97 800 0.121

105 825 0.127

113 850 0.133

122 875 0.139

146 900 0.162

COMPOUND-9

0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

0.160

0.180

100 200 300 400 500 600 700 775 825 875

V

t/V

33

From the graph,

Kp = 2.84 * 10 -4 B = 0.0090

where

µ -> Viscosity in Pa.s or kg/m.s = 0.6 centi Poise = 0.6 * 10-3 Pa.sec






Cs = 6.35 % w / w





Volume of ML = 93.65 / 800

= 0.117 m3




= 41.75 kg/ m3 of ML


α = 9.821 * 10-4 m/kg

Rm = 13.678 * 102 m-1

34

CONCLUSIONS: o Filtration was studied theoretically and on a lab scale.

o Using the available equipment (Buchner funnel set- up), the resistance of the filter medium

and the specific cake resistance of different cakes were calculated.

o It was observed that as the cake thickness increases, the pressure difference across the cake

also increases. Thus, the resistance to the fluid flow by the cake also increases.

o A graph was plotted between t/V Vs Volume of the filtrate collected over the filter medium.

The slope and the intercept of this graph gave values characteristic of the slurry.

o The conclusions of the experiments conducted are applicable to Pressure filtration

equipments such as Sparkler, Line, Candle, Cartridge filters and Vacuum filters such as

Nutsche filters and ANFDs.

o Scaling up of a centrifuge requires Pilot plant centrifuge devices for conducting lab- scale

experiments. It requires the application of other equations determined by scale up factors

after the calculation of the specific cake resistance and resistance of the filter medium.

• Theoretically, specific cake resistance values must lie in the range of 109 to 1012 and the

resistance of the medium should lie in the range of 104

• The DEVIATIONS in the values calculated from the graphs might be because

� The Pressure assumed in the experimental conditions might not have been

absolute vacuum.

� The concentration of the sample was assumed to be the same as the batch

concentration. This might not have been correct.

� The graphical calculation of the slope and the intercept of the graph plotted

might not have been precise.

35

ACKNOWLEDGEMENTS I thank Mr.Chellapandi, G.M., Process Engineering, for trusting my ability and knowledge and allowing me to work on a project. I extend my heartfelt gratitude to Mr. S. M. Krishnakumar and

Mr. T. Sivaramakrishna for their wonderful support, guidance and assistance through my project. I should not fail to thank them for their immense encouragement for the same. I thank the Process Development Lab technicians for their assistance and guidance through the project. I am forever indebted to all the Phase-2 employees for allowing me to observe and study the equipments and letting me learn the ways of work in the industry. I thank the H.R. Department for their timely assistance. I thank Mr.Jacob Jayakumar for his help with the transportation, without which things wouldn’t have been so easy. I also thank Mr.Jai Ganesh for the assistance at the canteen. Lastly, I thank Orchid Chemicals & Pharmaceuticals for this wonderful opportunity provided to young, aspiring students to increase their aptitude and enrich their knowledge by working in the company for a brief period of time and providing them with the required exposure to be successful individuals.

filtration report

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