plate filtrationf

8/13/2019 Plate Filtrationf

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Contents

1. Objective 3

2. Introduction 3

3. Theory 3

4. Experimental apparatus 4

5. Procedure 5

6. Observations 6

7. Calculations 9

8. Discussion 13

9. Causes of deviation 13

10.Nomenclatures 13

11.References 14


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Objective

To study the operation of pl ate and frame filter press. To determine Specific cake resistance () and medium resistance (R).

Introduction

Many processes in the food, chemical or pharmaceutical industries make products that are liquid-

solid suspensions or slurries. These mixtures are a little like a runny mud or milk-shake. The solids in

them do not dissolve in the liquid but are carried along in it. Filter presses separate the solids from

the liquids so that the useful part can be processed or packaged.

A filter consists of a series of filter chambers formed between square, rectangular or round filter

plates supported on a metal frame. Once the filter chambers are clamped, filter press is loaded withslurry. The plated on the filter press are clamped together with rams that generate pressure.

In addition to the filter plate filtration medium, the growing filter cake enhances removal of fine

particles in the slurry. The solution coming through the filter press called filtrate will be pure. The

pores of the medium will be larger than the particles which are to be removed, and the filter will

work efficiently only after an initial deposit has been trapped in the medium. One of the biggest

advantages of this filtration process is that it is a mechanical operation and much less energy

demanding than evaporation or drying. The most important factors in the filter selection are the

specific resistance of filter cake, the quantity to be filtered and the solid concentration.

Theory

For incompressible cake:

=

2 +

=

2+

1

Where

1= **c

b1= *R

Where, v= volume of filtrate collected, m3

t = Time, s

A = Total filtration area, m2

P = Pressure drop, Kg/cm2


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= Viscosity of the filtrate

= Specific resistance of the cake, m/Kg

R = filter medium resistance, m-1

C Concentration of slurry, Kg/m3

Under constant pressure conditions, we can integrate the above equations to yield

= +

Where, =

and =

Plot of t/v vs. v is a straight line by which we can yield a and b and further and R by the formulae

=

and =

ExperimentalApparatus

Mixing tank Agitator Pump Filter tank Filtrate collection tank Pressure gauge


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Procedure

1. Prepared slurry of CaCO3 in water (5%) in 25 liter water2. The slurry war fed to the feed tank and Agitator was switched on3. The pump was also switched on and only by-pass valves were switched on for better mixing4. The valve connecting the feed tank to the filter press was turned on completely5. Closed the by-pass valve very slowly so that the pressure drop was observed to be 10 Kg/cm26. The filtrate was collected in the filtrate collection tank and height of the filtrate collected

was noted as a function of time till there was appreciable fall in the rate of the filtrate

collection.

7. The process was repeated for the concentration 10% in 15 liter water and 20% in 10 literwater.


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Observation

Data:-

NF= 6Ac = 16 x 16 cm

2= 256 cm

2= .0256 m

2

AFl = 8 x 8 cm2

= 64 cm2

= .0064 m2

= .001 Ns/m2

g = 9.81 m/sec2

Wt. of plate 1 = 42.63 g







Table# 1 For CaCO3concentration 5% in 25 litre water

Time(s) Height(cm) Pin (mm-Hg) Pout (mm-hg)

0 16 10 0

30 18.8 10 0

60 21.5 10 0

90 24.1 10 0

120 26.6 10 0

150 29.2 10 0

180 31.5 10 0

210 33.8 10 0

240 35.9 10 0

270 38.4 10 0

300 45.5 10 0

330 47.5 10 0

360 49 10 0

390 50.8 12 0

420 52.4 12 0

450 54 12 0

480 55.6 12 0

510 57.2 12 0

540 58.7 12 0

570 60.2 12 0

600 61.7 12 0

630 63.4 12 0

690 64.7 12 0

720 66 12 0750 67.4 14 0


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780 68.8 14 0

810 70.1 14 0

840 71.2 14 0

870 72.4 14 0

900 73.5 14 0930 74.4 14 0

960 75.3 14 0

990 76.2 14 0

1020 77.1 14 0

1050 78 14 0

1080 78.7 14 0

Table #2 For CaCO3concentration 10% in 15 litre water


0 4 10 0

30 6.5 10 0

60 8.7 10 0

90 10.8 10 0

120 12.8 10 0

150 14.5 10 0

180 16.4 10 0

210 18.1 10 0

240 19.8 10 0

270 21.4 10 0

300 22.7 10 0

330 23.8 10 0

360 25.9 12 0

390 26.5 12 0

420 27.3 12 0

450 27.5 12 0

480 27.8 12 0

510 28 12 0

540 28.2 12 0

570 28.4 12 0

600 28.5 12 0

630 28.6 12 0


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Table #3 For CaCO3concentration 20% in 10 litre water


0 4 10 0

30 6 10 0

60 8.8 10 0

90 9.3 10 0

120 10.1 10 0

150 10.5 12 0

180 10.7 12 0

210 10.8 12 0

240 10.8 12 0

Table#4 Weight of the cake formed for 5% concentration

Plate Number Wt. of cake with plate(g) Wt. of cake without plate(g)

1 249.42 206.79

2 235.18 195.79

3 254.65 211.72

4 248.00 203.85

5 255.72 210.96

7 252.64 209.65



1 249.21 206.58

2 249.63 210.24

3 253.93 210.62

4 252.42 211.27

5 254.51 209.75

6 249.40 203.25



1 250.05 207.42

2 242.32 202.93

3 246.93 204

4 247.92 206.77

5 248.91 204.15

6 248.08 205.93


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Calculations

Table#7 Ref. Height, volume and t/v for 5% concentration

Time(s) Height, h (cm) Ref. Height, h`(cm) Volume(m3

) t/v(s/m3

)0 16 0 0 0

30 18.8 2.8 0.000717 41852.68

60 21.5 5.5 0.001408 42613.64

90 24.1 8.1 0.002074 43402.78

120 26.6 10.6 0.002714 44221.7

150 29.2 13.2 0.003379 44389.2

180 31.5 15.5 0.003968 45362.9

210 33.8 17.8 0.004557 46084.97

240 35.9 19.9 0.005094 47110.55

270 38.4 22.4 0.005734 47084.26

300 45.5 29.5 0.007552 39724.58

330 47.5 31.5 0.008064 40922.62

360 49 33 0.008448 42613.64

390 50.8 34.8 0.008909 43776.94

420 52.4 36.4 0.009318 45072.12

450 54 38 0.009728 46258.22

480 55.6 39.6 0.010138 47348.48

510 57.2 41.2 0.010547 48354.07

540 58.7 42.7 0.010931 49399.88

570 60.2 44.2 0.011315 50374.72

600 61.7 45.7 0.011699 51285.56

630 63.4 47.4 0.012134 51918.51

690 64.7 48.7 0.012467 55345.23

720 66 50 0.0128 56250

750 67.4 51.4 0.013158 56997.81

780 68.8 52.8 0.013517 57705.97

810 70.1 54.1 0.01385 58485.44

840 71.2 55.2 0.014131 59442.93870 72.4 56.4 0.014438 60255.98

900 73.5 57.5 0.01472 61141.3

930 74.4 58.4 0.01495 62205.69

960 75.3 59.3 0.015181 63237.77

990 76.2 60.2 0.015411 64239

1020 77.1 61.1 0.015642 65210.72

1050 78 62 0.015872 66154.23

1080 78.7 62.7 0.016051 67284.69


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Time(s) Height, h (cm) Ref. Height, h`(cm) Volume(m3

) t/v(s/m3)

0 4 0 0 0

30 6.5 2.5 0.00064 46875

60 8.7 4.7 0.001203 49867.02

90 10.8 6.8 0.001741 51700.37

120 12.8 8.8 0.002253 53267.05

150 14.5 10.5 0.002688 55803.57

180 16.4 12.4 0.003174 56703.63

210 18.1 14.1 0.00361 58178.19

240 19.8 15.8 0.004045 59335.44

270 21.4 17.4 0.004454 60614.22

300 22.7 18.7 0.004787 62667.11

330 23.8 19.8 0.005069 65104.17

360 25.9 21.9 0.005606 64212.33

390 26.5 22.5 0.00576 67708.33

420 27.3 23.3 0.005965 70413.09

450 27.5 23.5 0.006016 74800.53

480 27.8 23.8 0.006093 78781.51

510 28 24 0.006144 83007.81

540 28.2 24.2 0.006195 87164.26

570 28.4 24.4 0.006246 91252.56

600 28.5 24.5 0.006272 95663.27630 28.6 24.6 0.006298 100038.1


Time(s) Height, h (cm) Ref. Height, h`(cm) Volume(m3 ) t/v(s/m3)

0 4 0 0 0

30 6 2 0.000512 58593.75

60 8.8 4.8 0.001229 63828.56

90 9.3 5.3 0.001357 66332.55120 10.1 6.1 0.001562 76844.26

150 10.5 6.5 0.001664 90144.23

180 10.7 6.7 0.001715 104944

210 10.8 6.8 0.001741 120634.2

240 10.8 6.8 0.001741 137867.6


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Sample calculations:-

For CaCO3 concentration of 5%

P = 11.94*1333.22 Pa = 15918.64 pa

A = 2 * Nf* Aflm2= 2 * 6 * (64 * 10-4) = 0.0768 m

2

a(slope) = 2 x 106

m-3

b(intercept) = 36270 s/m3

= 2 * A2* P * a / (* c) m/kg = 7.51*10

10m/Kg

R = A * P * b / m-1

= 4.43* 1012

m-1

Concentration 50 100 200

a(slope)( m-3

) 2 x 106 7 x 10

6 5 x 10

7

b(intercept)( s/m3) 36270 36211 16637

P(Pa) 15918.64 14532.09 14517.43

(m/Kg) 7.51 x1010

1.2 x 1011

4.3 x1010

R(m-1

) 4.43 x 1012

4.04 x 1010

1.9 x1010

Graph#1 t/v vs. v for 5% concentration of CaCO3

y = 2E+06x + 36270

R = 0.7509

0

10000

20000

30000

40000

50000

60000

70000

80000

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018

tV (cu. m)

t/v vs v


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y = 7E+06x + 36211

R = 0.7237

0

20000

40000

60000

80000

100000

120000

0 0.001 0.002 0.003 0.004 0.005 0.006 0.007

tV (cu. m)

t/v vs v

y = 5E+07x + 16637

R = 0.5455

0

20000

40000

60000

80000

100000

120000

140000

160000

0 0.0002 0.0004 0.0006 0.0008 0.001 0.0012 0.0014 0.0016 0.0018 0.002

tV (cu. m)

t/v vs v


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Discussion

Surface filtration works largely through direct interception. This means that the pore size of the

medium are stopped at the upstream surface of the filter. The particle size prevents them from

entering or passing the pores. Surface type media are not perfectly smooth on their surfaces, nor are

their pores perfectly in their shape or direction.

Typically, when surface type filters are exposed to the flow of contaminated fluid, two effects- the

gradual reduction in effective pores size and the building of a cake bed- start to take place almost

immediately.

Gradual reduction in effective pore size-The effective pore size of the medium is gradually reduced,

as some of the pores become partially blocked by the particles, this reduction makes the filter

become more effective in removing fine particles. Pore size reduction can be caused by the

retention of extremely small particles within the pores by absorptive forces.

Building of cake filter- A cake or bed filter aid particles start to build on the surface of the filter

cloth. This build-up of filter cake actually does the filtering. As time continues this cake becomes

progressively finer.

Causes of Deviations:

1. The deposition of filtrate inside the plate and frame filter press led to deviated results filtrate

volume.

2. Pressure drop could not be maintained constant as all the slurry made was exhausted and some

air had entered the pump.

3. The readings on the scale were not clear and only after a certain time the readings became visible;

Also error due to parallax.

4. Some filtrate was lost when additional slurry was prepared and mixed in the agitator.

Nomenclature

A = Slope of the graph AFl= Area of one frame, m2 AC= filtration area, m2 B = Intercept of the graph V = Volume of filtrate collected in time t, m3 t = time, s C = Concentration of the slurry, Kg/m

3

g = Acceleration due to gravity, m/sec2


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Nf= Number of frames P = pressure drop, mm-Hg = viscosity of the filtrate Ns/m2 = specific resistance of the cake, m/Kg

R = filter medium resistance, m

-1

V = volume of filtrate collected in time t, m3 Pi = Inlet Pressure, mm-Hg Po = Outlet Pressure, mm-Hg h = height of filtrate collected in time t, cm

Reference

1. Lab Manual ChE 391, 2012-132. McCabe, W.L. and J.C. Smith, Unit Operations of Chemical Engineering, 3rdEdition, McGraw-Hill,

1976 pp. 932-942

3. Coulson, J.M. and J.F. Richardson, Chemical Engineering, Vol. 2, Pergamon Press, 1960, pp. 414-

421

4. Walas, S.M, Chemical Process Equipment Selection and Design, Butterworth- Heinemann, 1990,

pp. 305-334

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