Plate and Filter Frame Press

 

Mass Transfer 2 Experiment 4 : Plate and Filter Frame Press

1. 1.0 0  Objective The purpose of the experiment was to study the operation of the filter press for  filtra filtration tion of calciu calcium m carbon carbonate ate slurry slurry and to determ determine ine the filter filter med medium ium resist resistanc ancee and specific cake resistance from filtration data obtained.

2. 2.0 0 Summary   The experiment`s objective was to study the operation of the filter press for filtration of calcium carbonate slurry and to determine the filter medium resistance and specific cake resistance from filtration data obtained. Calcium carbonate solution was used as the filtrate. The experiment was run, every 5 L of filtrate produced the time was taken. At three different time, three samples was taken to study the relationship of density and viscosity to volume of  filtrate. The viscosity and density of the samples was decreasing as V is approaching the final volume. volu me. And using using the equation given, given, the value of filter medium medium resistance resistance and filter f ilter cake resistance was found . The viscosity and density was values at the three different samples was taken and it is found that they are proportional in relationship. The value of filter medium resistance and specific cake resistance was determined from filtration data obtained.

3. 3.0 0 Result 1

 

Mass Transfer 2 Experiment 4 : Plate and Filter Frame Press

Weight fraction of calcium carbonate in slurry : 5 %

Weight of wet cake Tray 1 :

3600 g

Tray 2 :

290 g

Tray 3 :

550 g

Total :

4400 g

  Weight of dry cake Tray 1 :

3460 g

Tray 2 :

240 g

Tray 3 :

410 g

Total :

4110 g

Weight ratio of wet cake to dry cake (mf/mc) : 1.071

Viscosity of filtrate (μ) At V= 5 L

:

5 Pa.s

At V=45 L :

1 Pa.s

At V=89.3 L:

1 Pa.s

Density of filtrate (p) At V=5 L

1.0 g/cm3

:

At V=45 L :

0.997 g/cm3

At V=89.3 L:

0.992 g/cm3

Density of calcium carbonate : 2.93   g/cm 3 Total active filter area : 0.47 m x 47.0 m =  22.09 m 2 Pressure drop (ΔP) : 40 Total filtration time : 1005 s Total volume of filtrate : 89.30 litre 2

 

Mass Transfer 2 Experiment 4 : Plate and Filter Frame Press

Table 1 : Filtrate volume volume corresponding to time Filtrate volume V (litre)

Time t (second)

5

75

10

107

15

155

20

203

25

255

30

323

35

374

40

428

45

478

50

530

55

583

60

640

65

692

70

743

75

793

80

844

85

895

89.3

1005

Table 2 : Table of the density of the 3 trays ρ1

ρ2

ρ3

1.000 g/cm3

0.997 g/cm3

0.992 g/cm3

μ1

Table 3: Table of the viscosity of the 3 trays μ2

μ3

5 Pa.s

1 Pa.s

1 Pa.s

3

 

Mass Transfer 2 Experiment 4 : Plate and Filter Frame Press

C = mass of solid deposited(total weight of wet cake) in the filter per unit volume of  filtrate = 4.10 kg89.3 L = 0.04591 kg/L

4.0  Tutorial 1. Plot the data relating to t/V versus V to obtain a straight linear graph Table 2 : t/V and V t/V (second/liter)

Filtrate volume V (liter)

15

5

10.7

10

10.33

15

10.15

20

10.2

25

10.77

30

10.69

35

10.7

40

10.62

45

10.6

50

10.6

55

10.67

60

10.65

65

10.61

70

10.57

75

10.55

80

10.53

85 4

 

Mass Transfer 2 Experiment 4 : Plate and Filter Frame Press

11.25

89.3

Figure 1 : t/V versus V graph

2. The slope of each line is K c/2 in seconds per liter and 1/q o from the intercept of the line. When ΔP is constant, the only variable left are V and t. When t=0 and V=0 and ΔP=ΔPm : hence; μRmAΔP = (dtdV) = 1qo dtdV=1q = K cV + 1qo

Where, K c = μcαA2(ΔP)

(1)

Integration of the equation (1) between the limits (0,0) and (t,V) gives tV=(Kc2)V + 1qo

y = -0.015x + 11.52 slope = -0.015x = K c/2 K c = -0.030 s/L, since it cannot be negative, the negative sign is neglected. so, K c = 0.030 s/L 1/qo = intercept = 11.52

3. Obtain the filter value of filter medium resistance (Rm) and cake resistance ( α)

from these equations. 1qo = μRmA(ΔP) , K c = μcαA2(ΔP)

Where, μ = viscosity of filtrate 5

 

Mass Transfer 2 Experiment 4 : Plate and Filter Frame Press

A = filter area (ΔP) = pressure drop

C = mass of solid deposited in the filter unit per unit volume of filtrate (kg/L)

So, Rm = A(ΔP)qoμ

= 22.09 (40 )0.08681μ = 10178.55μ

Table 3: Table of the viscosity of the 3 trays μ1

μ2

μ3

5 Pa.s

1 Pa.s

1 Pa.s

Table 4: Table for filter medium resistance for the three trays Rm1 10178.55 μ1 = 50892.75 m-1

 

Rm2

Rm3

10178.55 μ2

10178.55 μ3

= 10178.55 m-1

= 10178.55 m-1

Rm = Rm1+Rm2+Rm33 = 50892.75+10178.55+10178.553 = 71249.85  m -1

And, α = KcA2(ΔP)μc α = 0.030 (22.09)2(40)μ0.04591 (22.09)2(40)μ0.04591 α = 0.030 (22.09)2(40)0.04591μ (22.09)2(40)0.04591μ

= 12754.56μ

Table 3: Table of the viscosity of the 3 trays 6

 

Mass Transfer 2 Experiment 4 : Plate and Filter Frame Press

μ1

μ2

μ3

5 Pa.s

1 Pa.s

1 Pa.s

Table 5: Table for filter cake resistance for the three trays α1

α2

α3

12754.56 μ1

12754.56 μ2

12754.56 μ3

= 63772.79 s/L

= 12754.56 s/L

= 12754.56 s/L

 

α = a1+a2+a33

= 63772.79+ 12754.56+ 12754.563 = 89281.91 s/L

5.0  Discussion

7

 

Mass Transfer 2 Experiment 4 : Plate and Filter Frame Press

Figure 1 : t/V versus V graph From the graph, at t=5 minutes,the t/V is at its highest at the first 5 L. This is because there were less cake resistance during the first 5 liters as the cake resistance had just started to build up. A filter cake is formed by the substances that are retained on a filter. The filter cake grows in the course of filtration, becomes thicker as particulate matter is being retained [2]. With increasing layer thickness the flow resistance of the filter cake increases[2]. From V=5 until V=30 the resistance of the filter cake resistance was starting to increase, that causes the graph to plummet.As time volume increase, the filter cake resistance is increasing until the cake was fully stuffed at the trays. From V equals 30L to V=89.3 the graph become linear, this proof that the cake resistance is at its maximum and cannot build up anymore. The filter  medium resistance changed only when the pressure drop changed[1]. Cake resistance is based on the volume of filtrate stucked in the filter. With some filter cakes, the specific resistance varies with the pressure drop across it [2]. This is because the cake becomes denser under the higher pressure and so provides fewer and smaller small er passages passages for flow[2]. The effect is spoken of as the compressibility of the cake. The pressure drop of this experiment was constant at 40 psi. Filter cake builds up on the upstream side of the cloth, that is the side away from the plate [2]. In the early stages of the filtration cycle, cyc le, the pressu pressure re drop drop across across the cloth cloth is small small and filtrati filtration on proceed proceedss at more more or less less a constant rate[2]. As the cake increases, the process becomes more and more a constant-pressure one and this is the case of this experiment. Calcium carbonate is directly affected by the pressure drop because of the size of its particle, this does not apply to materials with smaller particle like salt and sugar [2]. The result of the experiment may not be correct because of the machine may not be fucntioning properly. This may cause error of the experiment which means it is not the same as the theory.

Table 6 : Table of density and viscosity at different volume V=5 L

V=45 L

V=89.3 L

ρ1

ρ2

ρ3

3

1.000 g/cm μ1

3

0.997 g/cm μ2 8

3

0.992 g/cm μ3

 

Mass Transfer 2 Experiment 4 : Plate and Filter Frame Press

5 Pa.s

1 Pa.s

1 Pa.s

Table 2 and 3 shows the values of the different density and v viscosity iscosity of the different volume which are V=5L,V=45L and V=89.3L. The relation of the density and viscosity of the filtrate is proportional. For the first volume the value was the highest because the of the cake and filter medium resistance was at it initial stage, which is the lowest. This is also caused by the pressure is at its highest since there was still less resistance in during the first 5 liter. Then, at V=45 liter the value of the density and viscosity decreases compared to the value of the first 5 liter. This is because the cake resistance was starting to build up and less particle can get through throu gh as the filter filtrate filtrate more calcium carbonate carbonate compared to the first 5 liter. At the final volume, V=89.3 L, the viscosity had remained constant because of the cake resistance had remained constant as explained before(graph discussion). The density still decreases, this may not be correct as it is also have to remain constant or almost the same as density at V=45 L. This may be caused by experimental error, for example there is still air trapped inside the density meter which cause the density value is less than it is supposed to be. The weight of the cake(dry and wet) was different for every trays. The first tray have the highest weight because of it is the first tray that was in contact with the filtrate. The cake had build up at tray 1 that causes it to have the highest weight. The the third tray have higher  weight than tray 2 maybe because of tray 3 have smaller holes for its filter than two. The different of weight of wet cake and dry cake is because of the weight of moisture(water) in wet cake.  

6. 6.0 0 Conclusion The conclusion is the filter medium resistance and specific cake resistance had been determined which are Rm=71249.85 m-1 and =89281.91 s/L by using the graph and formulas and the data obtained. We explained the factors that affects the filter medium resistance and specific cake resistance value which are pressure drop, filter medium, the size of particle. The result of thus experiment may not be correct as the machine may not be functioning properly. Proper maintenance should be done for better reliability of the experiment.

9

 

Mass Transfer 2 Experiment 4 : Plate and Filter Frame Press

 

7.0 References Reference s

1. McCabe, Smith and Harriot, Units Operations of Chemical Engineering, McGraw

Hill, 6th edition (2000)

Food Processing. NZIFST (Inc.) ,(1983) ,(1983) 2. R. L. Earle ,Unit Operations in Food

8.0 Appendices C = mass of solid deposited(total weight of wet cake) in the filter per unit volume of  filtrate = 4.10 kg89.3 L = 0.04591 kg/L

μRmAΔP = (dtdV) = 1qo dtdV=1q = K cV + 1qo

Where, K c = μcαA2(ΔP)

(1)

Integration of the equation (1) between the limits (0,0) and (t,V) gives tV=(Kc2)V + 1qo

y = -0.015x + 11.52 10

 

Mass Transfer 2 Experiment 4 : Plate and Filter Frame Press

slope = -0.015x = K c/2 K c = -0.030 s/L, since it cannot be negative, the negative sign is neglected. so, K c = 0.030 s/L 1/qo = intercept = 11.52

1qo = μRmA(ΔP) , K c = μcαA2(ΔP)

Where, μ = viscosity of filtrate A = filter area (ΔP) = pressure drop

C = mass of solid deposited in the filter unit per unit volume of filtrate (kg/L)

So, Rm = A(ΔP)qoμ

= 22.09 (40 )0.08681μ = 10178.55μ Rm = Rm1+Rm2+Rm33 = 50892.75+10178.55+10178.553 =  71249.85 m -1

And, α = KcA2(ΔP)μc α = 0.030 (22.09)2(40)μ0.04591 (22.09)2(40)μ0.04591 α = 0.030 (22.09)2(40)0.04591μ (22.09)2(40)0.04591μ

= 12754.56μ 11

 

Mass Transfer 2 Experiment 4 : Plate and Filter Frame Press

α = a1+a2+a33

= 63772.79+ 12754.56+ 12754.563 = 89281.91 s/L

12