STIRRED TANK (TGK) - labtkitb.files.wordpress.com · (TGK) TGK – 2016/PW 7 CHAPTER II PURPOSE AND...

EXPERIMENT MODULE

CHEMICAL ENGINEERING EDUCATION LABORATORY

STIRRED TANK

(TGK)

CHEMICAL ENGINEERING DEPARTMENT

FACULTY OF INDUSTRIAL TECHNOLOGY

INSTITUT TEKNOLOGI BANDUNG

2018

INSTRUCTIONAL LABORATORY CHEMICAL ENGINEERING DEPT.

FTI - ITB

STIRRED-TANK MODULE (TGK)

TGK – 2016/PW 2

Contributor:

Dr. IDG Arsa Putrawan, Dr. Sanggono Adisasmito, Dr. Ardiyan Harimawan,

Yoga Sujatnika, Dinna Rizqi Awalia, Dr. Pramujo Widiatmoko


FTI - ITB


TGK – 2016/PW 3

TABLE OF CONTENT

TABLE OF CONTENT ............................................................................................................. 3

LIST OF TABLE ....................................................................................................................... 4

LIST OF FIGURE...................................................................................................................... 5

CHAPTER I INTRODUCTION ................................................................................................ 6

CHAPTER II PURPOSE AND TARGET OF EXPERIMENT ................................................ 7

CHAPTER III EXPERIMENTAL DESIGN ............................................................................. 8

CHAPTER IV WORK PROCEDURE .................................................................................... 10

BIBLIOGRAPHY .................................................................................................................... 12

APPENDIX A RAW DATA TABEL ...................................................................................... 13

APPENDIX B CALCULATION PROCEDURE .................................................................... 15

APPENDIX C LITERATURE DATA .................................................................................... 17

APPENDIX D JSA CONTROL SHEET ................................................................................. 18


FTI - ITB


TGK – 2016/PW 4

LIST OF TABLE

Table 1. Data of Tap Water Density and Viscosity Determination . . . . . . . . . . . . . . . . . . . 13

Table 2. Dimension of the Stirred Tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Table 3. Data Characteristic Impeller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Table 4. Primary Experiment Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Table 5. Figure Observation of Flow Patterns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14


FTI - ITB


TGK – 2016/PW 5

LIST OF FIGURE

Figure 1. Simple Stirred Tank Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure 2. Type of Stirrer (a) propeller, (b) turbine, (c) paddle . . . ... . . . . . . . . . . . . . . . . . 8

Figure 3. Preliminary Experiment Flow Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

Figure 4. Primary Experiment Flow Diagram. . . . . . . ……... . . . . . . . . . .. . . . . . . . . . . . .11


FTI - ITB


TGK – 2016/PW 6

CHAPTER I

INTRODUCTION

Stirring is an operation aimed at moving the stirred materials, generally carried out to mix

and disperse the material. The stirred material may be two dissolved liquids, solids in a

liquid, a gas in a liquid in bubbles form. Stirring may also be carried out to accelerate heat

transfer, for example by heating the fluid with a coil and / or a heating jacket.

Factors affecting stirring and mixing processes which are the tank configuration, type and

geometry of the agitator, position of the stirrer axis, stirrer rotation speed, and the physical

properties of the stirred fluid. Type and geometry of the mixer is closely related to the stirring

flow patterns that occur. Mixing in the tank occurs because of the rotational motion of the

stirrer in the fluid. This stirring motion 'cuts' the fluid and can cause a moving Eddy current,

creating a flow across the fluid part. The selection of type and geometry of the agitator is

based on the physical properties of the fluid, especially the viscosity. In addition to type and

geometry of the agitator, the speed of stirring also affects circular flow patterns. Excessively

high velocities can lead to whirlpool or so-called vortex. This vortex is not expected in

stirring because it leads to a decrease in the quality of stirring, the entry of air into the fluid,

and over flow of the fluid due to rising fluid surfaces.


FTI - ITB


TGK – 2016/PW 7

CHAPTER II

PURPOSE AND TARGET OF EXPERIMENT

The purpose of the stirred-tank module experiment is:

1. Learn mixing process of component in a fluid which held in a stirred tank system.

2. Identify factors that affect the effectiveness of mixing.

The target of this experiment is to be able to practice:

1. Derive the correlation of mixing time with rotational speed through the analysis of

dimensionless numbers.

2. Derive the correlation of mixing time with the speed of rotation and time through

analysis of dimensionless numbers.

3. Carry out a visual observation of flow patterns and provide an analysis of the flow

patterns that occur.

4. Determine the optimum mixing conditions.


FTI - ITB


TGK – 2016/PW 8

CHAPTER III

EXPERIMENTAL DESIGN

The schematic diagram of the stirred tank system circuit used for this experiment can be seen

in Figure 1. The type of agitator consists of 3, shown in Figure 2.

Keterangan gambar

C = height stirrer from the bottom of

the tank

D = diameter of the mixer blade

Dt = diameter of tank

H = height fluid in the tank

J = width baffle

W = width of mixer blade

Figure 1. Simple Stirred Tank Scheme

Figure 2. Type of Stirrer (a) propeller, (b) turbine, (c) paddle


FTI - ITB


TGK – 2016/PW 9

The tools needed for this practicum are:

1. Set the stirred tank tool

2. Stopwatch

3. Viscometer

4. 25 mL Pycnometer

5. Measuring cylinder

6. Voltmeter

7. Multimeter as amperemeter

8. Pipette

9. Impeller

The list of materials required to carry out this practice is:

1. Tap water

2. Aqua DM

3. Solid grains that are not soluble in water

4. Dyes

The variations done in this experiment are:

1. The speed of the stirrer rotation

2. Type and size of stirrer, propeller, turbine, and paddle.

3. Position of the impeller is center and off-center.

4. Use of baffles.

5. Height of the impeller


FTI - ITB


TGK – 2016/PW 10

CHAPTER IV

WORK PROCEDURE

The stirring module experiment consists of two parts: a preliminary experiment and a primary

experiment. The stirred tank experiment flow diagram is shown in Figure 3 and 4. A

preliminary experiment was conducted to measure the physical properties of the liquid in the

stirred tank, which are density and viscosity. Measurement of fluid density was carried out

with pycnometer, while the determination of viscosity is done with Ostwald viscometer. Both

tools are selected because they are simple and provide fairly accurate results for dilute

liquids.

The main experiment was conducted to observe the mixing time, which is the time required

to achieve the uniformity of the fluid component in the tank. This mixing time is analyzed by

observing homogeneity of color. Variation of stirring speed is done by speed regulator (but

recorded speed is listed in speed display). The power required for stirring may be calculated

by measuring the voltage and current used by the agitating motor. This voltage and current

measurement is performed using amperemeter and voltmeter mounted on the stirrer. After

measuring the mixing time, the experiment is a flow pattern observation. Observations were

made by observing the movement of granules in the fluid during stirring.

Figure 3. Preliminary Experiment Flow Diagram

Measurement of fluid

temperature with

thermometer

Determination of fluid

viscosity with Ostwald

viscometer

Determination of fluid

density with pycnometer


FTI - ITB


TGK – 2016/PW 11

Figure 4. Primary Experiment Flow Diagram

Preparation of tools and materials

The impeller is mounted on the stirrer axis. The axis of the mixer is

attached to the stirrer motor. Connect to power and turn it on.

Initial current reading (Io) and initial voltage (Vo)

The stirring speed is adjusted according to the planned variation

Tap water is put into the tank according to the specified volume. Dyes are

inserted according to the specified volume. The mixing time to

homogeneous is recorded.

Solid grains are included for flow pattern observation. The flow patterns

are then drawn and / or recorded.

The reading of the final current (I) and the final voltage (V)

The above experiment series are repeated for variations of stirring type,

stirring speed, axis position, and baffle usage.


FTI - ITB


TGK – 2016/PW 12

BIBLIOGRAPHY

Mc Cabe, W.L., Unit Operation of Chemical Engineering, 3rd Edition, McGraw-Hill Book

Co., New York, 1978

Perry, R., Green, D.W., and Maloney, J.O., Perry’s Chemical Engineers’ Handbook, 6th

Edition, McGraw-Hill, Japan, 1984

Brodley, and Hershey, Transport Phenomena: A Unified Approach, McGaw-Hill Book Co.,

New York, 1988, Chapter: Application of Mixing

Moo-Young et al., The Blending Efficiencies of Some Impellers in Batch Mixing, AIChEJ,

18 (1), 1972, pp. 178-182

Tatterson, and Gary, B., Fluid Mixing and Gas Dispersion in Agitated Tanks, McGraw-Hill

Book Co., New York, 1991, Chapter 1,2, and 4


FTI - ITB


TGK – 2016/PW 13

APPENDIX A

RAW DATA TABEL

A.1. Determination of Density and Viscosity of Tap Water

Table 1. Data of Tap Water Density and Viscosity Determination

Repetition I II

Aqua dm temperature (oC)

Empty pycnometer mass (g)

Mass pycnometer + aqua dm (g)

Mass pycnometer + tap water (g)

Aqua dm retention time (s)

Tap water retention time (s)

A.2. Tool Configuration

Table 2. Dimension of the Stirred Tank

Characteristic Value

Diameter

Tank Height

Baffle Amount

Baffle Width

Baffle Thickness

Baffle Length

Table 3. Data Characteristic Impeller

Type Turbin Paddle Propeller

Diameter

Number of leaves

Width of leaves

Length of leaves

Thickness of leaves


FTI - ITB


TGK – 2016/PW 14

A.3. Main Experiment

Table 4. Primary Experiment Data

Type of Impeller :

Position of Impeller :

Baffle/non-baffle :

N (rpm) Vo (volt) Io (mA) Vo (volt) Io (mA) Time (s)

A.4. Observation of Flow Patterns

Table 5. Figure Observation of Flow Patterns

Type of Impeller :

High speed

( ...rpm)

Low speed

(...rpm)

Baffle Centre

Off-centre

Non-baffle Centre

Off-centre


FTI - ITB


TGK – 2016/PW 15

APPENDIX B

CALCULATION PROCEDURE

B.1. Determination of Density and Viscosity

… (1)

… (2)

B.2. Analysis of Dimensionless Numbers

1. Reynolds Number

The Reynolds number is a dimensionless number that expresses the ratio between the inertial

force and the viscous force. For systems with stirring, the Reynolds (Re) number is expressed

as:

…(3)

dengan ρ = fluid density, μ = fluid vicosity, dan D = Impeller diameter.

There are three types of flow regimes in the stirring system, namely laminar, transition and

turbulent. The laminar flow regime is obtained on the Reynolds number 10, while the

turbulent occurs at Reynolds number above 104 [Broadkey, 1988].

2. Fraude Number

The Fraude number (Fr) shows the ratio of the inertia force to the force of gravity, expressed

as:

… (4)


FTI - ITB


TGK – 2016/PW 16

dengan Fr = Fraude number, N = Impeller rotating speed, D = impeller diameter, dan g =

gravity acceleration

Fraude numbers are mainly taken into account in the baffled stirring system. In this system,

the liquid surface shape in the tank is affected by gravity, can cause the formation of vortex.

The vortex shows a balance between the force of gravity and the inertia force.

3. Power Number

Power Numbers (Po) shows the ratio between the power produced by the flow and the inertia

force. Pressure changes due to flow distribution on the stirrer surface can be integrated

resulting in total torque and stirring speed. The power number is declared as:

… (5)

dengan Po = Power number, N = Impeller rotating speed, dan ρ = fluid density. Power used

is effective power, that is:

Peff = V.I – Vo.Io … (6)

The correlation between the Power numbers with Reynold and Fraude is expressed in the

following equations:

For system without baffle : Po = a Reb Fr

c

For system with baffle : Po = a Reb

where a, b, c = experimental constants. The equation can be dilinearkan with natural

logarithm making it easier to calculate.

B.3. Graph Making

The mixing time correlation curve and stirring flow are made by passing data ln (N.t) to ln

(NRe). The power demand correlation curve to the stirring flow is the ln (NPo) to ln (NRe),

whereas the optimum condition is the intercept point between graph N to t and P to t.


FTI - ITB


TGK – 2016/PW 17

APPENDIX C

LITERATURE DATA

C.1. Water Density Data at Various Temperatures

Source: Perry’s Chemical Engineers’ Handbook


FTI - ITB


TGK – 2016/PW 18

APPENDIX D

JOB SAFETY ANALYSIS CONTROL SHEET

Material name Material properties Hazards and Repressive act

Fluid with low viscosity

Water

• Melting point 0 ˚C

• Boiling point 100 ˚C

• Good solvent

• Viscosity (0.86 cP at 26 ˚C)

• Colorless liquid, odorless

• Polar solvent

• General handling of

practicum materials

Accidents that may occur Repressive act

Water spilled Cleaned with mop.

Short-circuiting of electrical appliances. Immediately switch off the appliance, disconnect the

power supply.

Safety equipment

Laboratory coat Google

Stages of Experiment

Preparation Tools and Materials • Ensure that the power source is properly

installed in the agitator and the stirring motor is

mounted either on the support rod.

Experiment • Ensure that the stir bar rod is properly installed

when changing the type of stir bar.

• Make sure the test rack wheel is locked

Post Experiment • Disconnect all current connections on electrical

appliances

• Turn off the multimeter

Assistant Advisor Lab TK coordinator

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