Absorption

King suad university

College of engineering

Chemical engineering department

Absorption

ChE403

Alawi Al-Awami 423101724

Meshal Al-Jahani 424105851

Meshal Al-Saeed 423105653

Date: 8/5/1429

Supervised :Dr. Malik Al-Ahmad

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Table of Contents :

Title PageSummary 3

Introduction 4

Expierment objective 6

Theory 7

Schematic diagram 8

Experimental procedure 9

Results & Calculation 10

Discussion & Conclusion 16

Reference 17

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Summary :

The objective of this experimental To examine the air pressure differential across the column as a function of air flow rate different water flow rates down the column.

Pressure differential should be plotted as a function of air flow rate on log-log graph paper for each water flow rate.

From our experimental we read differential height and calculated the differential pressure by using equation.

ΔP=ρ *g *Δh

We calculated the results from table (1) to (6) and plotted log-log graph between air flow rate VS. Differential pressure.

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Introduction :

Absorption is a mass transfer process in which a vapor solute A in a gas mixture is absorbed by means of a liquid in which the solute more or less soluble. The gas mixture consists mainly of an inert gas and the soluble. The liquid also is primarily in the gas phase; that is, its vaporization into the gas phase is relatively slight. A typical example is absorption of the solute ammonia from an air-ammonia mixture by water. Subsequently, the solute is recovered from the solution by distillation. In the reverse process desorption or stripping, the same principle and equations hold.(1)

A major application of a absorption technology is the removal of CO2 and H2S from nature gas or synthesis gas by absorption in solution of amines or alkaline salts.(2)

A common apparatus used in gas absorption and certain other operations is the packed tower, shown in Fig. (1) . The device consists of a cylindrical column, or tower, equipped with a gas inlet an distributing space at the bottom; a liquid inlet and distributor at the top; gas and liquid outlet at the top and bottom, respectively; and a supported mass of inert solid shapes, called tower packing.(2)

Common dumped packing, Ceramic Berl saddles and Raschig rings are older types of packing that are not much used now, although there were big improvements over ceramic spheres or crushed stone when first introduced. The shape prevent pieces from nesting closely together, and this increasing the bed porosity.(2)

In given packed tower with a given type and size of packing and with defined flow of liquid, there is an upper limit to the rate of gas flow, called the flooding velocity. Above this gas velocity the tower cannot operate. At the flow rate called the loading point, the gas start to hander the liquid downflow, and local accumulations or pools of liquid start to appear in the packing.(1)

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5

FIG (1): PACKED TOWER FLOW AND CHARACSTERISTICS FOR ABSORPSTION.

Expierment objective To exmine the air pressure differential across the column

as a function of air flow rate for different water flow rate down the column by Ploting the pressure differential as a function of air flow rate on log-log graph paper and establish the relationship between these variable.

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Theory:

ΔP=ρ *g *Δh

Where:

ΔP: differential pressure. (g/cm.s2) ρ: density. (g/cm3)g: gravity constant. (cm/s2)Δh: hight (cm H2O)

Plot the pressure differential as a function of air flow rate on log-log graph paper and establish the relationship between these variable.

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SCHEMATIC DIAGRAM :( 3)

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FIG (2): Gas absorption device.

Experimental Procedure :

1- The first step we dried by passing the maximum air flow until all

evidence of moisture in the packing has disappeared.

2- We run on of the pump of air.

3- At zero flow of air we read the hight and recorded it

4- We increased flow air to 20(l/min) and read of hight a cross the

column.

5- We increased flow air to 40,60, 80,…,180(l/min) and read of hight then

recorded it for each one.

6- After that we changed flow of water to 1.5(l/min) and repeat step 3 to 5

after that changed flow water to 2, 2.5, and 3(l/min).

7- The range of possible air flow rates will decrease with increasing water

flow rate duo to onset of ‘flooding’ of column, which should be noted.

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Result & Calculation :.

dry colunm air flow rate l /min 20 40 60 80 100 120 140 160water flow rate l/min 0 0 0 0 0 0 0 0Δp (cm H2O) 0.2 0.4 0.4 0.4 0.3 1.7 2.6 3.8Δp (g/cm.s2) 196 392 392 392 294 1666 2548 3724log air flow rate (l/min) 1.301029996 1.60206 1.778151 1.90309 2 2.079181 2.146128 2.20412log Δp (g/cm.s2) 2.292256071 2.593286 2.593286 2.593286 2.468347 3.221675 3.406199 3.57101

Table (1): data of flow (air + water) and differential pressure at dried column

dry c olunm

0

0.5

1

1.5

2

2.5

3

3.5

4

0 0.5 1 1.5 2 2.5

log Δp (g/cm.s2)

log

air

flow

rat

e l /

min

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Figure (3): graph of log ΔP vs. log air flow.

.

wet column air flow rate l /min 20 40 60 80 100 120 140 160water flow rate l/min 0 0 0 0 0 0 0 0Δp (cm H2O) 0.2 0.1 0.2 0.6 1.1 1.8 2.4 4.2Δp (g/cm.s2) 196 98 196 588 1078 1764 2352 4116log air flow rate (l/min) 1.301029996 1.60206 1.778151 1.90309 2 2.079181 2.146128 2.20412log Δp (g/cm.s2) 2.292256071 1.991226 2.292256 2.769377 3.032619 3.246499 3.371437 3.614475

Table (2): data of flow (air + water) and differential pressure at wet column

wet c olunm

0

0.5

1

1.5

2

2.5

2.5 2.7 2.9 3.1 3.3 3.5 3.7

log Δp (g/cm.s2)

log

air

flow

rat

e (l/

min

)

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Figure (4): graph of log ΔP vs. log air flow.

.

wet column air flow rate l /min 20 40 60 80 100 120 140 160water flow rate l/min 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5Δp (cm H2O) 0.6 1.2 0.2 0.6 1.6 4.4 6.2 10.6Δp (g/cm.s2) 588 1176 196 588 1568 4312 6076 10388log air flow rate (l/min) 1.301029996 1.60206 1.778151 1.90309 2 2.079181 2.146128 2.20412log Δp (g/cm.s2) 2.769377326 3.070407 2.292256 2.769377 3.195346 3.634679 3.783618 4.016532

Table (3): data of flow (air + water) and differential pressure at 1.5(L/min) of flow water

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water flow rate =1.5 (l/min)

0

0.5

1

1.5

2

2.5

2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1

log Δp (g/cm.s2)

log

air

flow

rat

e (l/

min

)

Figure (5): graph of log ΔP vs. log air flow.

wet column air flow rate l /min 20 40 60 80 100 120 140 160water flow rate l/min 2 2 2 2 2 2 2 2Δp (cm H2O) 0.4 0.2 0.2 1.8 3.4 6.4 10.6 20.6Δp (g/cm.s2) 392 196 196 1764 3332 6272 10388 20188log air flow rate (l/min) 1.301029996 1.60206 1.778151 1.90309 2 2.079181 2.146128 2.20412log Δp (g/cm.s2) 2.593286067 2.292256 2.292256 3.246499 3.522705 3.797406 4.016532 4.305093

Table (4): data of flow (air + water) and differential pressure at 2(L/min) of flow water.

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water flow rate =2(l/min)

0

0.5

1

1.5

2

2.5

2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5

log Δp (g/cm.s2)

air

flo

w r

ate

l /m

in

Figure (6): graph of log ΔP vs. log air flow.

.wet column air flow rate l /min 20 40 60 80 100 120 140 160water flow rate l/min 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5Δp (cm H2O) 0.2 0.2 0.4 2.4 4.8 10.2 11.2 20Δp (g/cm.s2) 196 196 392 2352 4704 9996 10976 19600log air flow rate (l/min) 1.301029996 1.60206 1.778151 1.90309 2 2.079181 2.146128 2.20412log Δp (g/cm.s2) 2.292256071 2.292256 2.593286 3.371437 3.672467 3.999826 4.040444 4.292256

Table (5): data of flow (air + water) and differential pressure at 2.5(L/min) of flow water

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waterflow rate =2.5 (l/min)

0

0.5

1

1.5

2

2.5

2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5

log Δp (g/cm.s2)

log

air

flow

rat

e (l/

min

)

Figure (7): graph of log ΔP vs. log air flow.

.wet column air flow rate l /min 20 40 60 80 100 120 140 160water flow rate l/min 3 3 3 3 3 3 3 3Δp (cm H2O) 3.6 2 0.6 1 4.2 11 20 45Δp (g/cm.s2) 3528 1960 588 980 4116 10780 19600 44100log air flow rate (l/min) 1.301029996 1.60206 1.778151 1.90309 2 2.079181 2.146128 2.20412log Δp (g/cm.s2) 3.547528576 3.292256 2.769377 2.991226 3.614475 4.032619 4.292256 4.644439

Table (6): data of flow (air + water) and differential pressure at 3(L/min) of flow water

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water flow rate=3 (l/min)

0

0.5

1

1.5

2

2.5

1 1.5 2 2.5 3 3.5 4 4.5 5

log Δp (g/cm.s2)

log

air

flow

rat

e (l/

min

)

Figure (8): graph of log ΔP vs. log air flow.

Discussion & Conclusions:

The pressure difference increased when the air flow and water flow increased.

The flooding point decreases as the air flow increases (the high water flow the gives less flooding point )

The slope of the flooding curve is decreasing with the increasing of the water flow rate

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References:

1. Chirstie J.Geankoplis, ( Transport Process and Unit Operation ), 4rd edition. University of Minnesota, 2003 by person Education, "Publishing as Prentice Hall Professional Technical Reference", pages: 645- 650.

2. Warren L. McCabe, Julian C. Smith and Peter Harriott,(UNIT

OPERATION OF CHAMICAL ENGINEERING), 7th edition, international edition 2005,”published by McGraw-Hill”, Avenue of the Americas, pages: 565-568.

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3. Aziz M. Abu-Khalaf, ( Chemical Engineering Education, CEE 32 (3) ), King Suad University 1998.

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