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UNIVERSITI TEKNOLOGI MARAFAKULTI KEJURUTERAAN KIMIACHEMISTRY ENG.LABORATORY

(CHE 315)

Checked by: Rechecked by:

No Title Allocated Marks (%) Marks (%)

1. Abstract/Summary 5

2. Introduction 5

3. Aims/Objective 54. Theory 5

5. Procedure 3

6. Apparatus 5

7. Results 20

8. Calculations 10

9. Discussions 20

10. Conclusions 10

11. Recommendations 5

12. References 5

13. Appendices 2

Total 100

NAME : AHMAD SHAZWAN BIN SHARIF MOHD

STUDENT NO : 2006254352

EXPERIMENT : ABSORPTION - TWO PHASE THROUGH A PACKED BED

DATE PERFORMED : 18 AUGUST 2008

PROGRAMME CODE : DIPLOMA IN CHEMICAL ENGINEERING / EH 110


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CONTENTS

Title Page

Abstract/Summary 2

Introduction 3

Objectives 4

Theory 5

Procedures 6

Apparatus 7

Results 8

Calculations 9

Discussions 14

Conclusions 15

Recommendations 16

References 17

Appendices 18

Summary/Abstract

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This experiment is conducted in order to find the loading and flooding point. The

Raschig ring in the flexi glass column packed is used to increase the interfacial area for

vapor-liquid contact. Solute gas enters at the base of the column, the flow rates are

determined by variable area flow meters water to .The top of the column is similarly

metered and falls trough the packing where it is contacted with the rising gas. The water

fills the manometer and a multiport selection valve, the differential pressure across the

column is determined. When column dynamic is being observed, water is continuously

circulated by means of the recirculation pump and compressed air is blown through the

column.

Introduction

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The packed bed represents a workhouse configuration for a wide variety of mass

transfer operations in chemical process industry, such as distillation, absorption and

liquid-liquid extraction. The packed bed configuration facilitates the intimate contact

(mixing) of fluids with mismatched densities, such as liquids and vapors. The increased

surface area for phase contact that packing offers increases the amount of momentum

transfer, manifested by an increased vapor-phase pressure drop through the column.

Objectives

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Determine how the mass transfer rate is affected by gas flow rate, especially as the

column approaches its loading and flooding points.

Next, it is to model the pressure drop of the gas(air) and the liquid (water) mass

velocities (m/hour) by using the flexi glass column packed with Raschig Ring..

Theory

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Absorption is a mass transfer operation in which a vapors solute A in a gas mixture is

absorbed by means of liquid in which the solute is more or less solute. The gas mixture

(Gas Phase) consists of mainly of an inert gas and the solute. The liquid (Liquid Phase) is

primarily immiscible in the gas phase; its vaporization in the gas phase is relatively small.

Redistribution of soluble gas as solute in the liquid may involve molecular diffusion

in a stagnant medium, molecular diffusion in a smoothly flowing medium (laminar),

molecular diffusion and mixing in turbulent flowing medium or mass transfer between

phases.

The total amount of the material transferred is increased with the time, area through

the transferred occurred.

NA = KA ( CA1 - CA2)

A passive device such as packing was designed for the increasing of the interfacial

area for vapor-liquid contact. Packed towers are vertical columns filled with suitable

packing and normally operated counter currently. Liquid enters the top of the column and

is distributed over the top of the column packing via nozzles or distributor plates. Liquid

flows downward while contact with the vapor phase. Internal packing provides a large

surface area for two - phase contact and facilitates transfer of materials between phases.

Packing imparts good vapor-liquid contact when a particular type is placed together in

numbers, without causing excessive pressure drop across a packed section. Good packing

is a large specific surface area, large free cross section, low weight per unit volume and

large free volume. Large free cross section affects the frictional drop through the tower

and therefore the power that is required to circulate the gas. Small free cross section

means a high velocity for a given throughput of gas, and above certain limiting velocities,

there is tendency to blow the liquid out of the tower. Large free volume is to allow for

reaction in the gas phase, this factor may be importance.

Procedures

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1. The values are arranged according to the U-tube arrangement by filling the

manometer U-tube with water.

2. Before the experiment starts, make sure the values of operating arrangement areset correctly.

3. Before the column is safe to be used, check all valves carefully( closed).

4. The liquid flow rate is set at 20 m3/hour and then valve VR-3 and valve VR-4 are

opened. Noted that; to avoid the air from being trapped in line, we should make sure

that the level of liquid returning to the water reservoir must always be higher than the

bottom of the reservoir. To avoid this phenomena, valve VR-4 is adjusted.

5. The airflow is set to be 10 m3/hour by opening the valve VR-1. During the

experiment, make sure the water and the air flow rate are constant by watching it

every 2 minutes and the pressure drop ( P) mmH2O in the u-tube is read.

6. An extra 5 m3/hour is added to the column to increase the gas flow rate. Wait for

two minutes and the pressure drop is read again.

7. To reach the Flooding Point, step 4 must be repeated

8. The curve of Ln (V) versus Ln ( P/m packing) is plotted.

9. Step 2 to 6 are repeated with difference kind of liquid flow rate

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Apparatus

1. Water tank glass absorption column

-Water flow meter

-Gas flow meter

-Manometer tube

-Water pump

-Compressor

2. Stopwatch

3. Ruler

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Results and Calculations

Liquid Flow, L (m3/hr) : 20

Gas Flow,

V (m3/hr)

Monotube Low

(mm H2O)

Monotube High

(mm H2O)

(P)

(mm H2O)ln (V)

ln (P/m

packing)

10 197 200 3 2.30 - 0.981

15 197 201 4 2.71 - 0.693

20 198 204 6 3.00 -0.288

25 199 203 4 3.22 - 0.693

30 195 209 14 3.40 0.560

35 193 209 16 3.56 0.693

40 167 234 67 3.69 2.125

45 144 257 113 3.81 2.648

50 flooding flooding - - -

GRAPH of ln (V) Vs ln (PRESSURE DROP / m PACKING)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

-2 -1 0 1 2 3

ln (Pressure Drop / m Packing

ln

(V)

Seri


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GRAPH of ln (V) vs ln (PRESSURE DROP / m

PACKING)

0

1

2

3

4

5

-2 -1 0 1 2 3

ln (Pressure Drop / m Packing)

ln

(V)

Serie


Gas Flow,

V (m3/hr)

Monotube Low

(mm H2O)

Monotube High

(mm H2O)

(P)

(mm H2O)ln (V)

ln (P/m

packing)

10 194 203 7 2.30 - 0.134

15 183 215 32 2.71 1.386

20 189 210 21 3.00 0.96525 183 215 32 3.22 1.386

30 198 200 2 3.40 -1.386

35 184 214 30 3.56 1.322

40 168 229 61 3.69 2.031

45 160 257 97 3.81 2.495


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GRAPH of ln (V) vs ln (PRESSURE DROP / m

PACKING)

0

0.5

1

1.5

2

2.5

3

3.5

0 0.5 1 1.5 2 2.5 3


ln

(V)

Serie


Gas Flow,

V (m3/hr)

Monotube Low

(mm H2O)

Monotube High

(mm H2O)

(P)

(mm H2O)ln (V)

ln (P/m

packing)

Gas Flow,

V (m3/hr)

Monotube Low

(mm H2O)

Monotube High

(mm H2O)

(P)

(mm H2O)ln (V)

ln (P/m

packing)

10 151 251 100 2.30 2.526

15 164 204 40 2.71 1.609

20 172 230 58 3.00 1.98125 173 229 56 3.22 1.946






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10 178 222 44 2.30 1.705

15 190 213 23 2.71 1.216

20 186 216 30 3.00 1.417







GRAPH of ln(V) vs (PRESSURE DROP / m PACKING)

0

0.5

1

1.5

2

2.5

3

3.5

0 0.5 1 1.5 2


ln

(V)

Serie

Liquid flow, L (m3/hr) : 20

At gas flow 10 m3/hr

Pressure drop

P mm H2O = Manometer, High - Manometer Low

= (200 197) mm H2O

= 3 mm H2O

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The same step was repeated to calculate the pressure drop at gas flow 15 mm H2O until 45

mm H2O.

15 m3/hour = P, mm H2O = 4 mm H2O







ln (V) = ln 10

= 2.30

Repeat the same step to calculate the ln (V) at gas flow 15 mm H2O until 45 mm H2O.

15 m/hour ln 15 = 2.71

20 m/hour ln 20 = 3.00

25 m/hour ln 25= 3.22

30 m/hour ln 30 = 3.40

35 m/hour ln 35 = 3.56

40 m/hour ln 40 = 3.67

45 m/hour ln 45 = 3.81

ln (P/m packing)

ln (P/m packing) = ln (0.003 m H2O/0.008 m packing)

= -0.981

Repeat the same step to calculate the ln (P/m packing) at gas flow 15 mm H2O

until 45 mm H2O.

15 m/hour ln (P/m packing) = - 0.693

20 m/hour ln (P/m packing) = -0.288

25 m/hour ln (P/m packing) = -0.693

30 m/hour ln (P/m packing) = 0.560

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Note : All these steps were repeated to calculate the pressure drop, ln (V) and ln (P/m packing)

the different liquid flow which are 30 m3/hr, 40 m3/hr and 50 m3/hr.

Discussions

This experiment uses packed tower that has 8mm glass Raschig Rings. When the liquid

flow is at 20 m3/hr and gas flow 10 m3/hr, pressure drop is 3mm H2O after 2 minutes,

ln (V) = ln 10 which is 2.30 and the ln (P/m packing) = ln (0.006 m H 2O/0.008 m packing)

which is -0.288. The gas flow increases to15 m 3/hr and after 2 minutes operates, the reading of

manometer is taken and the pressure drop is 6 mm H 2O, From calculation of ln 15 is 2.71 and the

ln (P/m packing) is -0.470. After that, the gas flow is increased to 20m3/hr and using the same

duration time, pressure drop is 14 mm H2O, from calculation ln 20 is 3.00 and the ln (P/m

packing) is 0.560. The gas flow increases to 25m3/hr and pressure drop is 31 mm H2O, from

calculation ln 20 is 3.22 and the ln (P/m packing) is 0.405. The following steps are repeated

using gas flow 30 m3/hr until 50 m3/hr.

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Conclusion

The flooding point and the pressure drop can be determined by using gas-liquid

absorption column. At 20 m/hr liquid flow rate, no flooding point occurs. Then, at 30

m/hr there is still no flooding point. After the flooding point occurs, liquid flow rate is

raised to 40m/hr with the vapor flow at 45 m/hr but the pressure drop could not be

determined. However, before the flooding point, the pressure drop will moderately

increases and sometimes decreases due to the error during experiment. In the end, the

liquid flow rate is increased to 50 m/hr, the flooding point is achieved when the vapor

flow is at 35m/hr.

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Recommendations

1. Observe all the informations about the machine works.

2. Change valve VR-4 to computer control because it is hard to control manually.

Use a device that can control it automatically when the level water changes.

3. Use real manometer to measure pressure so perfect reading value can be obtained.

4. For the manometer reading, take the highest reading because it will still move

after 2 minutes.

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References:

1. Christine John Geankoplis, Transport Processes And Separation Process Principle

(Includes Unit Operations), 4th Edition, Pearson Education International.

2. Coulson, J.M. and Richardson J.F., Chemical Engineering, Volume 2, Third Edition

(SI Units), Pergamon.

3. Chemical Engineering Laboratory (CHE 315) Manual. Abd Jamil Lam, Chemical

Engineering Faculty, UiTM Shah Alam, Selangor.

4. www.wikipedia.com

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Appendices

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