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Koya University

Faculty of Engineering

Chemical engineering Department

Name of Experiment: Effect of Initial Concentration on

Sedimentation Characteristics

No . Of Experiment : (1)

Group : (A)

Name of lab :unit operation labPrepared by : mevan Ahmed

pavel hamasalih

masoud bilal

balen mohamad

hersh anwarkaywan osman

Supervised by: teach.Abdwlmajid

Date of experiment: 26/10/2014

Date of summation: 2/11/2014


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Content

Aim.1

Introduction..2

Theory...3

Equipment.5

Procedure.............6

Table of data............7

Table of Calculation.8

Discussion.11

Reference................17

Subject page


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Aim

Graph of Clear Liquid Interface Height

vs. Settling Time

Study theEffect of Initial Concentrationon Sedimentation Characteristics


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Introduction

Sedimentation (settling) is the separation of suspended particles

that are heavier than

water. The sedimentation of particles are based on the gravity

force from the di

erences

in density between particles and the

uid. Sedimentation is widely used in wastewater

treatment systems. A successful sedimentation is crucial for the

overall eciency of the

plant. Common examples include the removal of;

Grit and particulate matter in the primary settling basin(settling tanks that

receive raw wastewater prior to biological treatment are

called primary tanks, forsedimentering).

Sludge from the bioreactor (activated sludge process).

Chemical flocs in the chemical step.


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TheoryTheoretical basis:

Sedimentation is simply the process of letting suspendedmaterial settle by gravity.

It is accomplished by decreasing the velocity of the water being

treated to a point below which the particles will no longer

remain in suspensionWhen the velocity no longer supports the

transport of the particles, gravity will remove them from the

flow.In a glass cylinder, when solids diffuse through the interface, the

process starts then to settle from a slurry during a batch settling

test and assumed to approach terminal velocities under

hindered settling conditions. Thus, several zones of

concentration will be established

The particle is not

actually sent all the way to the bottom of thecell, resulting in a sediment. Rather, a low centrifugal field is

used to create a concentration gradient- where more particles

near the bottom of the cell than near the top.

When the temperature decreases, the rate of settling becomes

slower. The result is that as the water cools, the detention time

in the sedimentation cylinder must increase.

As sedimentation continues, heights of each zone vary and the

point at which a single distinct interface forms between liquid

and sediments will be reach.


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Sedimentation is one of the great classical methods where it is

applied for polymer characterization. It can determine the

concentration of a polymeric solute as a function of 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 of unpleasant drug.

The Critical Sedimentation Pointis the point in the settlingprocess at which the particles in the mixture have reached the

sediment stage. None of the suspension zone is still around.

At the critical point, it should be noted that things have not

been completely compressed; merely compressed enough for

all the particles to have entered into the sediment zone.


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Equipment

Sedimentation Study Unit

Used materials:

Water, sand, salt, CaCO3and colors

chalk.


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Experimental Proceeding:

1. Two liters of 2%, 4%, 6%, 8% & 10% by weight CaCO3suspension in water are prepared.

2. Each slurry is placed in sedimentation tubes at the

same height.

3. The slurry inside the vessel was ensured to have a

homogenous characteristic by carefully mixing and

shaking the sedimentation cylinders.4. The heights of the clear regions were recorded with

intervals of 5 minutes for the first two hours.

5. The samples were left overnight and the last point is to

be recorded at that period.


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Table of data

Time

interval

minute

Height of interface cm

2% 4% 6% 8% 10%

0 791 781 805 813 812

10 675 705 756 783 793

20 563 633 710 755 776

30 447 559 664 728 760

40 338 487 618 701 744

50 230 416 573 674 72860 120 345 529 649 714

70 74 277 486 624 698

80 64 218 445 599 683

90 57 196 409 574 670

100 50 183 380 556 656

24 hr 39 72 108 142 175


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calculation

Sample of calculation: For 2%

H2=675 mm

H1=791 mm

DH=H2-H1 = 791-675 = 116 mm

Time = 10 min

Velocity = DH/time

Velocity = 116/10 = 11.6 mm/min

Velocity = 696 mm/hr


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Table of calculation

Time interval

minute

Settling velocity mm/hr

2% 4% 6% 8% 10%

0

10 696 456 294 180 114

20 672 432 276 168 102

30 696 444 276 162 96

40 654 432 276 162 96

50 648 426 270 162 96

60 660 426 264 150 84

70 276 408 258 150 96

80 60 354 246 150 90

90 42 132 216 150 78

100 42 78 174 108 84

24 hr 0.4583 4.625 11.33 17.25 20.04


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Figure (1)


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reference

Lab. sheet

https://www.google.iq/?gfe_rd=cr&ei=29RPVJjjGIfe8gfvmoH

QDg&gws_rd=ssl#q=sedimentation+introduction

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