ABSTRACT
Settling is the process by which particles sink gradually or slowly to the bottom of a
liquid and form sediments. Particles that experience a force, either due to gravity or due to
centrifugal motion will tend to move in a uniform manner in the direction exerted by that
force. For gravity settling which is what is applied in this experiment, this means that the
particles will tend to fall to the bottom of the vessel, forming slurry at the vessel base. The
objective of this experiment is to determine the settling velocity as a function of
concentration from batch sedimentation test. Sedimentation applies the process of settling
in separating solids from a liquid to obtain a liquid or solid. In the experiment carried out, the
slurry height of different concentrations of calcium carbonate (CaCo3) by weight:4%, 8%,
12%, 16% were recorded as time elapsed using vertical cylinders. The effects of the slurry
concentration on sedimentation characteristics were determined using the sedimentation
curves. The slurry showed an example of a hindered settling. Results showed that the slurry
concentration affects the calcium carbonate sedimentation characteristics. Increasing the
mixture concentration decreases the settling velocity of the particles before the compression
zone.
1
TABLE OF CONTENTS
TITLE PAGE
ABSTRACT…………………………………………………….………….…………….…1
TABLE OF CONTENTS………………………………………………………….…….2-3
LIST OF SYMBOLS………………………………………………………………………4
LIST OF FIGURES………………………………………………………………………..5
LIST OF TABLES………………………………………………………………………....6
CHAPTER ONE…………………………………………………………………………....7
1.0 INTRODUCTION……………………………………………………………………...7
CHAPTER TWO…………………………………………………………………………..8
2.0LITERATUREREVIEW...........………………………………………......................8-9
CHAPTER THREE………………………………………………………………………..10
3.0 DESCRIPTION OF APPARATUS…………………………………………………...10
3.1 EXPERIMENTAL PROCEDURES……………………..........................................11
CHAPTER FOUR………………………………………………………..........................12
4.0 EXPERIMENTAL RESULTS…………………………..........................................12-24
4.2 DISCUSSION OF RESULTS……………………..................................................25
CHAPTER FIVE…………………………………………………………………………26
5.0 CONCLUSION……………………………………………………….......................26
2
5.1 RECOMMENDATIONS……………………………………………….........27
REFERENCES………………………………………………………..................28
APPENDIX………………………………………………………………………..33
3
LIST OF SYMBOLS
Symbol
Name
Unit
Z
height of interface
cm
t
time
s
Vsi
settling velocity
ms-1
C
concentration
m-1
W1
mass flux or mass velocity
m-1
LIST OF TABLES
Table No.
Page No.
4.1
11
4.2
12
4.3
17
4.4
21
4
LIST OF FIGURES
Figure no.
Title.
Page no.
3.1
powdered chalk
10
3.2
weigh balance
10
3.3
meter rule
10
3.4
spatula
10
3.5
beaker
10
3.6
stop watch
10
3.7
sketch of setup
10
4.01
graph of z(4%) against t
13
4.02
graph of z(8%) against t
14
4.03
graph of z(12%) against t
15
4.04
graph of z(16%) against t
16
4.05
graph of Vsi against C for 4%
17
4.06
graph of Vsi against C for 8%
18
4.07
graph of Vsi against C for 12%
19
4.08
graph of Vsi against C for 16%
20
4.09
graph of Wi against Vsi for 4%
21
4.10
graph of Wi against Vsi for 8%
22
4.20
graph of Wi against Vsi for 12%
22
4.30
graph of Wi against Vsi for 16%
23
5
CHAPTER ONE
INTRODUCTION
Sedimentation is the partial separation or concentration of suspended solid particles from a
liquid by gravity. The equipment used for settling by gravity is either thickeners or clarifiers.
Sedimentation can either be a batch or continuous process. When the process is continuous
the concentration at which the mass rate of the solids is especially important for the correct
functioning of the system and design of the equipment used . In the experiment carried out
the sedimentation process applied was a batch process and the analysis carried out here is
comparable to any industrial settling process.
In the thickening process the concentration of the suspended solids in the feed stream is
increased whereas in clarification the suspended particles are removed to make a clear
effluent. Sedimentation can be classified in these types: Type 1 and Type 2.
In Type 1 settling, the suspension settles into four zones, a clear liquid zone, a constant
composition zone, a variable composition zone and sediment.
In Type 2 settling, there are only three zones with the constant composition zone absent.
In this experiment the settling process is a batch clarification process where the suspension is
allowed to settle into a clear liquid zone and sediment.
When the suspension is first allowed to settle, there is a brief period of acceleration, followed
by the constant downward movement of the interface between the clear liquid and the
suspension. The sediment accumulates at the bottom of the vessel. When the interface
approaches the layer of sediment, its rate of fall decreases until the critical settling point is
reached i.e. when the direct interface is formed between the sediment and the clear liquid.
Further sedimentation results in the agglomeration of the sediment and the increased upward
movement of the liquid.
The objective of this experiment is however to determine the settling velocity as a function of
concentration by weight of calcium carbonate. This process is important industrially because
it can be used to treat wastewater by removing suspending solids from it or it can be used to
recover valuable solids such as ores from washing solutions. It is one of the great classical
methods applied for polymer characterization. It can determine the concentration of a
polymeric solute as a function of a position from the center of a rapidly rotating cell. Also,
the chemical industry has large scope manufacturers of pharmaceuticals where suspension is
usually applicable for drug which is insoluble or poorly soluble. This is to prevent
degradation of drug or to improve stability of drug and to mask the taste of bitter or drugs
with unpleasant taste. Vaccines as an immunizing agent are often formulated as suspension
and so does for X-ray contrast agents.
The types of sedimentation processes used are affected by factors such as particle
size, liquid viscosity, solution densities, temperature as well as the characteristics of the
slurry within the solution. For batch settling carried out in vertical tubes the main factors
which affect the process are the height of the suspension, the diameter of the vessel, and the
volumetric concentration.
6
CHAPTER TWO
2.0 LITERATURE REVIEW
There are two basic types of settling that takes place, hindered settling and free
settling. Hindered settling occurs when the concentration of the solution is high enough for
there to be significant interaction between the particles. The frictional force exerted at a given
velocity of the particles relative to the fluid may be greatly increased as a result of
modifications to the flow pattern. Free or particulate settling occurs when the concentration
of the solution is low and the particles are sufficiently far apart to freely settle regardless of
their nature. Faster settling particles may collide with slower moving ones where they may
cohere or continue downward at their own settling velocity. The cohered particles settle at a
rate greater than that of the individual particles and there is a gradual transition from
particulate settling into zone settling regime where the particles are forced to settle as a mass.
The settling rate of the mass is a function of the solids concentration. The sedimentation
velocities of the particles tend to decrease steadily as the concentration of the suspension is
increased. However for very dilute solutions the settling velocities may be up to 1.5 times the
normal terminal velocities due to the formation of clusters of particles which settle in well
defined streams.
The suspension is first allowed to settle, there is a brief period of acceleration,
followed by the constant downward movement of the interface between the clear liquid and
the suspension. The sediment accumulates at the bottom of the vessel. When the interface
approaches the layer of sediment, its rate of fall decreases until the critical settling point is
reached i.e. when the direct interface is formed between the sediment and the clear liquid.
Further sedimentation results in the agglomeration of the sediment and the increased upward
movement of the liquid.
For batch settling carried out in vertical tubes the main factors which affect the process are
the height of the suspension, the diameter of the vessel, and the volumetric concentration.
Generally the height of the suspension does not affect the rate of sedimentation or the
consistency of the sediment obtained. However if the position of the interface is plotted as a
function of time for two or more different height, then it is seen that they vary by a constant
factor. If the ratio of the diameter of the vessel to the diameter of the particle is greater than
100 then the walls of the container have no effect on the rate of sedimentation process.
The concentration of the suspension however affects the rate of sedimentation such that at
higher concentrations the rate of fall of sludge is lower because the upward velocity of the
displaced fluid is greater hence the velocity gradients are steeper. The movement of the
particles is retarded and the settling rate is less than that for free settling. When the
concentration of a suspension is low the settling velocity is uniform and the particles move at
an almost constant rate. For a continuous process if the settling velocity is high then some of
the particles may be withdrawn with the clear liquid.
The shape and orientation of the vessel affects the rate of sedimentation such that if the walls
of the vessel are vertical and the cross-sectional area does not vary with depth then the shape
of the vessels can be considered to be is independent of the sedimentation rate. If the vessel is
inclined at an angle then its shape cannot be ignored.
The behaviour of settling particles in slurry can be conveniently studied in small batch
experiments. The data is then useful for designing large scale settling tanks which have a
number of applications (e.g. clarification of waste water). The main information required for
7
design is the settling rate of the particles as a function of the system parameters such as
particle size and shape, concentration, geometry of the system, etc. The effect of
concentration on the settling slurry continuously increases with time. The effect of geometry
of the system on the settling rate can be significant. When the cylinder is tilted, Boycott
(1920) found that the settling rate increases due to shorter sedimentation path. This
phenomenon is known as the Boycott effect, and is used to enhance the rate of settling in
some applications.
(i) Vertical Cylinders: Depending on the concentration of the slurry, two regimes of
settling are possible, free settling and hindered settling. As the name implies, in free settling,
each particle is unaffected by the motion of the neighbouring ones and its terminal velocity is
given by
Ut = {
g(𝜌p – 𝜌)Dp2
18𝜇
}
18𝜇Ut
Dp = {𝑔(𝜌𝑝− 𝜌)}1/2
Cd = 24/R
ԑ = 1 – C/𝜌p
*All above equations are valid only for Reynolds no. Re < 1.
Where
𝜌p and 𝜌 are the densities of the particle and the suspending medium respectively,
Dp is the diameter of the particle,
Cd is the drag coefficient
And Reynolds no. Re = DpUt 𝜌p/ 𝜇.
The model assumed for describing Free Settling, has some limitations in practical application.
Such as the interaction of particles in the fluid, or the interaction of the particles with the
container walls can modify the settling behaviour. Settling that has these forces in appreciable
magnitude is known as hindered settling.
In the hindered settling regime due to particle-particle interactions and up draft of liquid, the
velocity of individual particles is considerably smaller. The settling velocity (Us) may be
estimated by an empirical equation of the form
Us = Ut ԑn
where ԑ is the volume fraction of the fluid and n is a constant.
8
CHAPTER THREE
3.0 DESCRIPTION OF APPARATUS
The suspension used was white coloured powdered chalk and water. This was placed
in cylindrical glass vessels that were vertically oriented in the batch sedimentation apparatus.
30 cm meter rule was used to measure the settling heights. A stopwatch was used to measure
the rate of settling. A weigh balance was used to measure the powdered chalk before placing
them in the respective glass vessels.
List of the materials and apparatus used:
Fig 3.1 Powdered chalk (CaCO3)
Fig 3.2 Weigh balance.
Fig 3.3 Meter rule
Fig 3.7
Fig 3.4 Spatula
Fig 3.5 Beaker
Fig
3.6
watch
Stop
9
3.1 EXPERIMENTAL PROCEDURES
List of the materials and apparatus used:







Powdered chalk (CaCO3): substance under consideration mixed with water.
Weigh balance: for measurement of the powdered chalk
Meter rule: to determine settling heights.
Stirring rod: for even mixture of suspension before leaving to settle.
Spatula: for taking up powdered chalk.
Beaker: temporary placement for powdered chalk before placed or put into the
cylindrical glass vessel.
Stop watch: used to measure the rate of settling.
White chalk (CaCO3) was crushed to powdered form and weighed into four quantities to
make up four volumes of chalk in water slurry of 4%, 8%, 12% and 16% concentration by
weight. Each slurry was in separate beakers and volume in each of them was the same to fill
1.5 liter of the sedimentation tube.
Each slurry was turned into their respective sedimentation tube and stirred properly but
gently to avoid breaking the tube.
The interface between clear liquid and settling solids were recorded at time intervals of
5minutes for the four suspensions till the record of 30 minutes was obtained.
The settled slurry was then allowed to stand for 48 hours and obtained heights noted as well.
10
CHAPTER FOUR
4.0 RESULTS
Height of cylinder = 23.6cm
Radius of cylinder = 4.25cm
Density of water = 1g/cm3
Density = mass/volume ; 1 = mass/volume
Therefore, volume = mass = πr2h = 22/7 x 4.252 x 23.6
Mass = 1339.72g.
Concentration
4% of 1339.72 = 53.6g
8% of 1339.72 = 107.2g
12% of 1339.72 = 160.8g
16% of 1339.72 = 214.4g
RAW DATA TABLE
Serial no.
1
2
3
4
5
6
7
Table 4.1
Time
(mins)
5
10
15
20
25
30
48 hrs
4%
8.5
3.3
2.9
28
2.8
2.8
2.4
Heights of Interface (cm)
8%
12%
17.1
21.5
11.6
18.4
8.9
15.1
6.7
13.0
6.1
9.8
5.7
9.2
4.9
5.4
16%
21.6
19.8
18.1
16.2
14.2
11.1
6.3
11
PROCESSED DATA
Serial no.
1
2
3
4
5
6
7
Table 4.2
Time
(secs)
300
600
900
1200
1500
1800
172800
4%
0.070
0.018
0.014
0.013
0.013
0.013
0.009
Heights of Interface (m)
8%
12%
0.156
0.200
0.101
0.169
0.074
0.136
0.049
0.115
0.046
0.083
0.042
0.077
0.034
0.039
16%
0.201
0.183
0.166
0.147
0.127
0.096
0.048
 All values of time in table 4.1 multiplied by 60 for the conversion of time
from minutes to seconds. Example 5 x 60 = 300.
 1.5 subtracted from the values of height of interface to give the height of
clear water then divided by 100 for the conversion to meter from
centimeter. Example 8.5 – 1.5 =7 (height of clear water).
Then, 7/100 = 0.07m.
12
GRAPH OF Z (4%) AGAINST t
0,08
0,07
INTERFACE (m)
0,06
0,05
0,04
0,03
0,02
0,01
0
300
600
900
1200
1500
1800
172800
TIME (s)
Fig 4.01
Settling velocity = (y – y1)/(x – x1)
Settling velocity (1) = (0.070 – 0.018) ÷ (172800 – 1800) = 3.04 x 10-7
Settling velocity (2) = (0.07 – 0.014) ÷ (172800 – 1500) = 3.26 x 10-7
Settling velocity (3) = (0.07 – 0.013) ÷ (172800 – 1200) = 3.32 x 10-7
Settling velocity (4) = (0.07 – 0.013) ÷ (172800 – 900) =3.32 x 10-7
Settling velocity (5) = (0.07 – 0.013) ÷ (172800 – 600) =3.31 x 10-7
Settling velocity (6) = (0.07 – 0.009) ÷ (172800 – 300) = 3.30 x 10-7
Settling velocity (7) = (0.07 – 0.07) ÷ (172800 - 172800) = 0
Concentration C =1/Z
Concentration (1) = 1/0.070 = 14.3
Concentration (2) = 1/0.018 = 55.6
Concentration (3) = 1/0.014 = 71.4
Concentration (4) = 1/0.013= 76.9
Concentration (5) = 1/0.013= 76.9
Concentration (6) = 1/0.013= 76.9
Concentration (7) = 1/0.009= 111.1
13
GRAPH OF Z (8%) AGAINST t
0,18
0,16
INTERFACE (m)
0,14
0,12
0,1
0,08
0,06
0,04
0,02
0
300
600
900
1200
1500
1800
172800
TIME (s)
Fig 4.02
Settling velocity = (y – y1)/(x – x1)
Settling velocity (1) = (0.156 – 0.101) ÷ (172800 – 1800) = 3.22 x 10-7
Settling velocity (2) = (0.156 – 0.074) ÷ (172800 – 1500) = 4.79 x 10-7
Settling velocity (3) = (0.156 – 0.049) ÷ (172800 – 1200) = 6.24 x 10-7
Settling velocity (4) = (0.156 – 0.046) ÷ (172800 – 900) =6.40 x 10-7
Settling velocity (5) = (0.156 – 0.042) ÷ (172800 – 600) =6.62 x 10-7
Settling velocity (6) = (0.156 – 0.034) ÷ (172800 – 300) = 7.07 x 10-7
Settling velocity (7) = (0.156 – 0.156) ÷ (172800 - 172800) = 0
Concentration C =1/Z
Concentration (1) = 1/0.156 = 6.4
Concentration (2) = 1/0.101 = 9.9
Concentration (3) = 1/0.074= 13.5
Concentration (4) = 1/0.049= 20.4
Concentration (5) = 1/0.046= 21.7
Concentration (6) = 1/0.042 = 23.8
Concentration (7) = 1/0.034= 29.4
14
GRAPH OF Z (12%) AGAINST t
INTERFACE (m)
0,25
0,2
0,15
0,1
0,05
0
300
600
900
1200
1500
1800
172800
TIME (s)
Fig 4.03
Settling velocity = (y – y1)/(x – x1)
Settling velocity (1) = (0.200 – 0.169) ÷ (172800 – 1800) = 1.81 x 10-7
Settling velocity (2) = (0.200 – 0.136) ÷ (172800 – 1500) = 3.74 x 10-7
Settling velocity (3) = (0.200 – 0.115) ÷ (172800 – 1200) = 4.95 x 10-7
Settling velocity (4) = (0.200 – 0.083) ÷ (172800 – 900) =6.81 x 10-7
Settling velocity (5) = (0.200 – 0.077) ÷ (172800 – 600) =7.14 x 10-7
Settling velocity (6) = (0.200 – 0.039) ÷ (172800 – 300) = 9.33 x 10-7
Settling velocity (7) = (0.200 – 0.200) ÷ (172800 - 172800) = 0
Concentration C =1/Z
Concentration (1) = 1/0.200= 5.0
Concentration (2) = 1/0.169 = 5.9
Concentration (3) = 1/0.134= 7.5
Concentration (4) = 1/0.115= 8.7
Concentration (5) = 1/0.083= 12.0
Concentration (6) = 1/0.077 = 13.0
Concentration (7) = 1/0.039= 25.6
15
GRAPH OF Z (16) AGAINST t
0,25
INTERFACE (m)
0,2
0,15
0,1
0,05
0
300
600
900
1200
1500
1800
172800
TIME (s)
Figure 4.04
Settling velocity = (y – y1)/(x – x1)
Settling velocity (1) = (0.201 – 0.183) ÷ (172800 – 1800) = 1.05 x 10-7
Settling velocity (2) = (0.201 – 0.166) ÷ (172800 – 1500) = 2.04 x 10-7
Settling velocity (3) = (0.201 – 0.147) ÷ (172800 – 1200) = 3.15 x 10-7
Settling velocity (4) = (0.201 – 0.127) ÷ (172800 – 900) =4.30 x 10-7
Settling velocity (5) = (0.201 – 0.096) ÷ (172800 – 600) =6.10 x 10-7
Settling velocity (6) = (0.201 – 0.048) ÷ (172800 – 300) = 8.87 x 10-7
Settling velocity (7) = (0.201 – 0.201) ÷ (172800 - 172800) = 0
Concentration C =1/Z
Concentration (1) = 1/0.201= 5.0
Concentration (2) = 1/0.183 = 5.5
Concentration (3) = 1/0.166 = 6.0
Concentration (4) = 1/0.147 = 6.8
Concentration (5) = 1/0.127 = 7.9
Concentration (6) = 1/0.096 = 10.4
Concentration (7) = 1/0.048 = 20.8
16
Settling velocities x10-7 (m/s)
4%
0.00
3.04
3.26
3.32
3.32
3.31
3.30
8%
0.00
3.22
4.79
6.24
6.40
6.62
7.07
12%
0.00
1.81
3.74
4.95
6.81
7.14
9.33
16%
0.00
1.05
2.04
3.15
4.30
6.10
8.87
Concentrations (m-1)
4%
14.3
55.6
71.4
76.9
76.9
76.9
111.1
8%
6.4
9.9
13.5
20.4
21.7
23.8
29.4
12%
5.0
5.9
7.5
8.7
12.0
13.0
25.6
16%
5.0
5.5
6.0
6.5
7.9
10.4
20.8
Table 4.3
SETTLING VELOCITY m/s x10-7
GRAPH OF VSI AGAINST C for 4%
3,5
3
2,5
2
1,5
1
0,5
0
14,3
55,6
71,4
76,9
CONCENTRATION
76,9
76,9
111,1
(m-1)
Fig 4.05
Mass flux = (y – y1)/(x – x1)
Mass flux (1) = {(0.00 – 0.00)x 10-7}÷(14.3-14.3) = 0.00
Mass flux (2) = {(0.00-3.04) x 10-7} ÷ (14.3-55.6) = 7.36 x 10-9
Mass flux (3) = {(0.00-3.26) x 10-7} ÷ (14.3-71.4) = 5.71x 10-9
Mass flux (4) = {(0.00-3.32) x 10-7} ÷ (14.3-76.9) = 5.30x 10-9
Mass flux (5) = {(0.00-3.32) x 10-7} ÷ (14.3-76.9) = 5.30x 10-9
Mass flux (6) = {0.00-3.31) x 10-7} ÷ (14.3- 76.9) = 5.30x 10-9
Mass flux (7) = {0.00-3.30) x 10-7} ÷ (14.3-111.1) = 3.41x 10-9
17
SETTLING VELOCITY (m/s) x10-7
GRAPH OF VSI AGAINST C for 8%
8
7
6
5
4
3
2
1
0
6,4
9,9
13,5
20,4
CONCENTRATION
21,7
23,8
29,4
(m-1)
Fig 4.06
Mass flux = (y – y1)/(x – x1)
Mass flux (1) = {(0.00-0.00) x 10-7} ÷ (6.4-6.4) = 0
Mass flux (2) = {(0.00-3.22) x 10-7} ÷ (6.4-9.9) = 9.20 x 10-8
Mass flux (3) = {(0.00-4.79) x 10-7} ÷ (6.4-13.5) = 6.70x 10-8
Mass flux (4) = {(0.00-6.24) x 10-7} ÷ (6.4-20.4) = 4.46x 10-8
Mass flux (5) = {(0.00-6.40) x 10-7} ÷ (6.4-21.7) = 4.18x 10-8
Mass flux (6) = {0.00-6.62) x 10-7} ÷ (6.4- 23.8) = 3.80x 10-8
Mass flux (7) = {0.00-7.07) x 10-7} ÷ (6.4-29.4) = 3.07x 10-8
18
SETTLING VELOCITY (m/s) x10-7
GRAPH OF VSI AGAINST C for 12%
10
9
8
7
6
5
4
3
2
1
0
5
5,9
7,5
8,7
CONCENTRATION
12
13
25,6
(m-1)
Fig 4.07
Mass flux = (y – y1)/(x – x1)
Mass flux (1) = {(0.00-0.00) x 10-7} ÷ (5.0-5.0) = 0
Mass flux (2) = {(0.00-1.81) x 10-7} ÷ (5.0-5.9) = 2.01 x 10-7
Mass flux (3) = {(0.00-3.74) x 10-7} ÷ (5.0-7.5) = 1.50x 10-7
Mass flux (4) = {(0.00-4.95) x 10-7} ÷ (5.0-.8.7) = 1.34x 10-7
Mass flux (5) = {(0.00-6.81) x 10-7} ÷ (5.0-12.0) = 9.73x 10-7
Mass flux (6) = {0.00-7.14) x 10-7} ÷ (5.0- 13.0) = 0.893x 10-7
Mass flux (7) = {0.00-9.33) x 10-7} ÷ (5.0-25.6) = 0.453x 10-7
19
SETTLING VELOCITY (m/s) X10-7
GRAPH OF VSI AGAINST C for 16%
25
20
15
10
5
0
0
1,05
2,04
3,15
CONCENTRATION
4,3
6,1
8,87
(m-1)
Fig 4.08
Mass flux = (y – y1)/(x – x1)
Mass flux (1) = {(0.00-0.00) x 10-7} ÷ (5.0-5.0) = 0
Mass flux (2) = {(0.00-1.05) x 10-7} ÷ (5.0-5.5) = 2.10 x 10-7
Mass flux (3) = {(0.00-2.04) x 10-7} ÷ (5.0-6.0) = 2.04x 10-7
Mass flux (4) = {(0.00-3.15) x 10-7} ÷ (5.0-.6.5) = 2.10x 10-7
Mass flux (5) = {(0.00-4.30) x 10-7} ÷ (5.0-7.9) = 1.48x 10-7
Mass flux (6) = {0.00-6.10) x 10-7} ÷ (5.0- 10.4) = 0.113x 10-7
Mass flux (7) = {0.00-8.87) x 10-7} ÷ (5.0-20.8) = 0.561x 10-7
20
Settling velocities x10-7 (m/s)
4%
8%
12%
16%
0.00
3.04
3.26
3.32
3.32
3.31
3.30
Table 4.4
0.00
3.22
4.79
6.24
6.40
6.62
7.07
0.00
1.81
3.74
4.95
6.81
7.14
9.33
0.00
1.05
2.04
3.15
4.30
6.10
8.87
Mass flux (s-1)
4%
(x10-9)
0.00
7.36
5.71
5.30
5.30
5.30
3.41
8%
(x10-8)
0.00
9.2
6.7
4.46
4.18
3.80
3.07
12%
(x10-7)
0.00
2.01
1.50
1.34
9.73
8.93
4.53
16%
(x10-7)
0.00
2.10
2.04
2.10
1.48
1.13
5.61
GRAPH OF Wi AGAINST Vsi for 4%
MASS FLUX (s-1) X10-9
8
7
6
5
4
3
2
1
0
0
3,04
3,26
3,32
3,32
SETTLING VELOCITY (m/s)
3,31
3,3
X10-7
Fig 4.09
21
GRAPH OF Wi AGAINST Vsi for 8%
MASS FLUX (s-1) X10-8
10
9
8
7
6
5
4
3
2
1
0
0
3,22
4,79
6,24
6,4
SETTLING VELOCITY (m/s)
6,62
7,07
X10-7
Fig 4.10
GRAPH OF Wi AGAINST Vsi for 12%
MASS FLUX (s-1) X10-7
12
10
8
6
4
2
0
0
1,81
3,74
4,95
6,81
7,14
9,33
SETTLING VELOCITY (m/s) X10-7
Fig 4.20
22
GRAPH OF Wi AGAINST Vsi for 16%
MASS FLUX (s-1) X10-7
6
5
4
3
2
1
0
0
1,05
2,04
3,15
4,3
SETTLING VELOCITY (m/s)
6,1
8,87
X10-7
Fig 4.30
23
4.1 DISCUSSION OF RESULTS
From the result obtained above, we see that the height, z, and time, t, in the unit
process, batch sedimentation are of inverse relationship and ultimately a function of the given
mass percent of the sample.
From the results, we discovered that increase in settling velocity leads to increase in
concentration of the sample slurry. Also, the graphs plotted are not straight-line graphs i.e.
they are not linear graphs. It was also notice that there was also variation in the values gotten
for the mass velocity and so also, their graphs were not straight-line graphs.
24
CHAPTER FIVE
5.0 CONCLUSION
The experiment has confirmed that the higher the concentration of solid in a
suspension the slower the rate of settlement. Hence when mixing of solute and solvent is
done in a sedimentation process there should be average input of both, no too much solvent
neither too much concentration of solute. As applied to crude oil processing the denser or
more concentrated materials are settled at the bottom while the less dense materials are at the
top which also assist in the separation of crude oil.
The batch sedimentation test was carried out on calcium carbonate in chalk form with
various concentrations. The observations made of the sedimentation process conducted under
dynamic conditions are in agreement with the Kynch theory of sedimentation in which the
sedimentation process can be likened to a “slinky spring” collapsing onto itself from a height.
25
5.1 RECOMMENDATIONS
After the performance of the experiment, the following are recommended for its
improvements:



When pouring the chalk particles into the graduated cylinder, care must be taken to
avoid pouring the chalk particles on the wall of the graduated cylinder.
Timing should start immediately we stopped stirring.
It would be useful performing investigations about particle surface properties for
chalk particles depending on crystalline degree so as to enhance the knowledge about
its behaviour.
26
REFERENCES
https://en.wikipedia.org/wiki/Sedimentation/ accesed on 3 December, 2016
https://www.coursehero.com/file/14331486/Experiment-1pdf/ accessed on 3 December, 2016
http://www.che.iitb.ac.in/online/system/files/92/course_details/FM+304.pdf/ accessed on 3
December, 2016.
http://documents.mx/documents/sedimentation-final.html/ accessed on 3 December, 2016.
http://www.slideshare.net/jeufier/sedimentation-finalrepz1/ accessed on 3 December, 2016.
J.M .Coulson & J.F,Richardson.Chemical EngineeringVolume2(5thEdition)Chapter5.
Particle Technology & Separation Processes. J.R. Backhurst, J.H. Harker
Perry’s Chemical Engineers Handbook. Chapter 18 “Liquid Solid Operation & Equipment”
27