CHE504 - Lab Report on Gas Absorption (L8) (2018) PDF

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UNIVERSITI TEKNOLOGI MARA FAKULTI KEJURUTERAAN KIMIA HEAT & MASS TRANSFER LABORATORY (CHE504) NAME : NURLINA SYAHIIRAH BINTI MD TAHIR STUDENT NO : 2017632214 GROUP : EH2204I EXPERIMENT : GAS ABSORPTION (L8) (INDIVIDUAL REPORT) DATE PERFORMED : 5th APRIL 2018 SEMESTER :4 PROGRAMME / CODE : CHEMIC...

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UNIVERSITI TEKNOLOGI MARA FAKULTI KEJURUTERAAN KIMIA HEAT & MASS TRANSFER LABORATORY (CHE504) NAME STUDENT NO GROUP EXPERIMENT DATE PERFORMED SEMESTER PROGRAMME / CODE SUBMIT TO No. 1 2 3 4 5 6 7 8 9 10 11 12 13

: NURLINA SYAHIIRAH BINTI MD TAHIR : 2017632214 : EH2204I : GAS ABSORPTION (L8) (INDIVIDUAL REPORT) : 5th APRIL 2018 :4 : CHEMICAL ENGINEERING / EH220 : MADAM SYAFIZA BINTI ABD HASHIB

Title Abstract/Summary Introduction Aims Theory Apparatus Methodology/Procedure Results Calculations Discussion Conclusion Recommendations Reference Appendix TOTAL MARKS

Allocated Marks (%)

Marks

5 5 5 5 5 10 10 10 20 10 5 5 5 100

Remarks: Checked by:

Rechecked by:

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Date:

Date:

TABLE OF CONTENT

1.0

ABSTRACT ................................................................................................................... 2

2.0

INTRODUCTION......................................................................................................... 3

3.0

OBJECTIVES ............................................................................................................... 4

4.0

THEORY ....................................................................................................................... 5

5.0

MATERIALS & APPARATUS ................................................................................... 7

6.0

METHODOLOGY ....................................................................................................... 8

7.0

RESULTS .................................................................................................................... 10

8.0

CALCULATIONS ...................................................................................................... 14

9.0

DISCUSSION .............................................................................................................. 17

10.0 CONCLUSION ........................................................................................................... 19 11.0 RECOMMENDATIONS............................................................................................ 20 12.0 REFERENCES ............................................................................................................ 21 13.0 APPENDIX .................................................................................................................. 22

LAB REPORT ON GAS ABSORPTION (L8)

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1.0

ABSTRACT

Gas absorption is mass transfer operation where one or more species is removed from a gaseous stream by dissolution in a liquid. Packed tower with Rashchig Rings packings is used in the experiment. The main objective of the experiment is to examine the air pressure drop across the column as a function of air flow rate for different water flow rates through the column. The pressure drop is observed every 2 minutes at air flowrate of 20 LPM, 40 LPM, 60 LPM, 80 LPM, 100 LPM, 120 LPM, 140 LPM, 160 LPM and 180 LPM for water flowrate of 1 LPM, 2 LPM and 3 LPM, respectively. The experiment is ongoing for the respective water flowrate until flooding occurs. Then, the water flowrate is changed. The pressure drop increases as the air flowrate is increases. Comparing with their respective theoretical data, the pressure drop at 1 LPM and 2 LPM shows higher value but lower value at 3 LPM. The percentage error is determined at 12.50%, 33.33% and 20.00% for water flow rate of 1 LPM, 2 LPM and 3 LPM, respectively. Packing tower work efficiently at lower liquid flow rate. Low liquid flow rate enabling the absorption rate to be maximize. The objectives are successfully obtained, thus the experiment is successfully done.

LAB REPORT ON GAS ABSORPTION (L8)

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2.0

INTRODUCTION Gas absorption is mass transfer operation where one or more species is removed from

a gaseous stream by dissolution in a liquid. The component that is extracted from the gaseous stream is known as solute and the component that extracting the solute is known as solvent. Packed column is one of the commonly used gas absorption equipment. Packed column can be operated in co-current as well as counter currently. Counter-current flow is preferable since the contact time between the liquid and gas is greater. This equipment usually consists of a cylindrical column containing a gas inlet and distributing space at the bottom, a liquid inlet and a packing or filing in the tower. The packed column used in the experiment is SOLTEQ-QVF Absorption Column BP751-B which used Raschig Rings as the packings medium. Air and water as the gas and liquid, respectively. At low gas velocity, the pressure drop is proportional to the flow rate. At loading point, the gas starts to hinder the liquid flow and accumulation occurs in the packings. At the upper limit of the gas flow rate which is called flooding velocity, flooding occurs. The operating packed column, in actual operating or industries should be well below flooding since the equipment cannot operate above the flooding velocity. The pressure drop within the system increases as the flow rate of the gas or liquid is increases.

LAB REPORT ON GAS ABSORPTION (L8)

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3.0

OBJECTIVES

The following are the objectives for the experiment: 1) To examine the air pressure drop across the column as a function of air flow rate for different water flow rates through the column. 2) To plot the graph of column pressure drop against the air flow rate in a log – log graph. 3) To obtain the pressure drop from the generalized correlation chart as in Appendix. 4) To compare the experimental value and the correlated value.

LAB REPORT ON GAS ABSORPTION (L8)

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4.0

THEORY

Gas absorption is mass transfer operation where one or more species is removed from a gaseous stream by dissolution in a liquid. The component that is extracted from the gaseous stream is known as solute and the component that extracting the solute is known as solvent. Carrier gas is the insoluble component present in the gas that is not absorbed by the solvent. The transfer is based on the preferential solubility of solutes in the solvent (Gas Absorption And Desorption, n.d.). Packed towers are used for continuous countercurrent contacting of gas and liquid in absorption (Geankoplis, 1993).The mechanism in packed tower is the gas and liquid phases flows counter – currently where they interact on the packings interface. The liquid flows in downward direction, over the surface of the packing, whereas the gas flows through the space or voids of the packings in upward direction. The gas flow is driven by pressure while the liquid flow is driven by the gravity force. The gas undergoes pressure drop due to the liquid occupied some part of the open space and voids of the packing. Thus, reducing the area available for the gas to flow. If the packing is dry with no liquid feed, then maximum flow gas is available. The pressure drop increases as the liquid flowrate into the tower increases. High flux will resulting in flooding. This occurrence happen at the upper limit of the gas flow rate called flooding velocity since the liquid is blown out with the gas at the flooding point. The gas start to hinder the liquid flow at loading point where accumulation of liquid start appearing in the packing. Low flux will resulting in channelling or weeping. There are two types of packings types which is random and structured.

Figure 1 - Typical Packed Tower Packings: (a) Raschig ring, (b) Lessing ring, (c) Berl Saddle, (d) Pall Ring (Geankoplis C. J., 1993)

LAB REPORT ON GAS ABSORPTION (L8)

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One of the oldest specially manufactured types of random packings are Raschig rings and still in general use. (Separation Columns (Distillation, Absorption and Extraction)) They provide a large surface area within the volume of the column for the interaction between liquid and gas. They also enhance the contact time between liquid and gas. (iitb.vlab.co.in, 2011) The generalized correlation for pressure drops in packed column (Eckert, 1970)

Figure 2 - Generalized Correlation for Pressure Drop in Packed Columns (Eckert, Chem. Eng. Prog., 66(3), 39 (1970)

y − axis =

x − axis =

Where, Gy

Gy 2 FP vx 0.1 g C (ρx − ρy )ρy ρy Gx √ Gy ρx − ρy

(Equation 1)

(Equation 2)

= Gas Mass Velocity, kg/m2.s

Gx

= Liquid Mass Velocity, kg/m2.s

ρy

= Density of Gas, kg/m3

ρx

= Density of Liquid, kg/m3

FP

= Packing Factor, m-1

vx

= Kinematic Viscosity of Liquid, m2/s

gC

= gravitational constant,

LAB REPORT ON GAS ABSORPTION (L8)

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5.0

MATERIALS & APPARATUS

5.1

Materials 1) Water. 2) Air.

5.2

Apparatus 1) SOLTEQ-QVF Absorption Column BP751-B

Figure 3 - The Packed Column Used in The Experiment with Raschig Rings as The Packings

LAB REPORT ON GAS ABSORPTION (L8)

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6.0

METHODOLOGY

6.1

Start-Up Procedures 1) All the valves are ensured to be closed except for the ventilation valve, V13. 2) All the gas connections are checked to be properly fitted. 3) All the valve on the compressed air supply line is opened. The supply pressure is set to between 2 to 3 bars by turning the regulator knob clockwise. 4) The shut-off valve on the CO2 gas cylinder is opened and the pressure is checked. 5) The power for the control panel is turned on.

6.2

Experimental Procedures: Hydrodynamics of a Packed Column (Wet Column Pressure Drop) 1) The receiving vessel B2 is filled through the charge port with 50L of water by opening valve V3 and V5. Then, valve V3 is closed. 2) Valves V9 and V10 is opened slightly. The flow of the water from vessel B1 through pump P1 is observed. Pump P1 is switched on. 3) Valve V11 is slowly opened and adjusted to give a water flowrate of around 1L/min. 4) The water is allowed to enter the top of the column K1, flow down the column and accumulated at the bottom until it overflows back to vessel B1. 5) The valve V11 is opened and adjusted to give a water flow rate of 1 L/min into column K1. 6) The valve V1 is opened and adjusted to give and air flow rate of 20L/min into column K1. 7) The liquid and gas flow in the column K1 is observed. The pressure drop across the column at dPT-201 is recorded. 8) Steps 3 to 5 is repeated with different values of air flow rate, each time increasing by 20 L/min each time after two minutes while maintaining the same water flow rate. 9) Steps 3 to 6 is repeated with different values of water flow rate, each time increasing by 1 L/min by adjusting valve V11.

LAB REPORT ON GAS ABSORPTION (L8)

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6.3

Shut-Down Procedures 1) Pump, P1 is switched off. 2) Valves, V1, V2 and V12 is closed. 3) The valve on the compressed air supply line is closed and the supply pressure is exhausted by turning the regulator knob counter clockwise all the way. 4) The shut-off valve on the CO2 gas cylinder is closed. 5) All the liquid in the column K1 is drained by opening valve V4 and V5. 6) All the liquid from the receiving vessels, B1 and B2 is drained by opening valves, V7 and V8. 7) All the liquid from the pump P1 is drained by opening valve V10. 8) The power for the control panel is turned off.

LAB REPORT ON GAS ABSORPTION (L8)

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7.0

RESULTS

Table 7.1: Pressure Drop At Different Water Flow Rate and Air Flow Rate. Flow rate

Pressure Drop

(L/min)

(mBar)

Air

20

40

60

80

100

120

140

160

180

1.0

0

0

2

4

5

11

14

25

32 (F)

2.0

0

2

3

6

10

14

25

41(F)

F

3.0

1

2

5

10

18

36(F)

F

F

F

160

180

Water

*F = Flooding Table 7.2: Pressure Drop At Different Water Flow Rate and Air Flow Rate. Flow rate

Pressure Drop

(L/min)

(mm H2O/m)

Air

20

40

60

80

100

1.0

0.00

0.00

25.49

50.99

63.73

2.0

0.00

25.49

38.24

76.48

127.46 178.45 318.66

3.0

12.75

25.49

63.73

127.46 229.44

Water

120

140

140.21 178.45 318.66

458.87 (F)

F

522.60 (F) F

407.89 (F) F

F

*F = Flooding Table 7.3: Theoretical Pressure Drop At Different Water Flow Rate and Air Flow Rate. Flow rate

Theoretical Pressure Drop

(L/min)

(in H2O/ft)

Air

20

Water

40

60

80

100

120

140

160

180

1.0

0.0000 0.0906 0.2000 0.2917 0.4205 0.7500 1.1667

F

F

2.0

0.0750 0.2500 0.3958 0.5000 1.0000

F

F

F

F

3.0

0.1600 0.4318 0.7500 1.5000

F

F

F

F

F

*F = Flooding

LAB REPORT ON GAS ABSORPTION (L8)

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Table 7.4: Theoretical Pressure Drop At Different Water Flow Rate and Air Flow Rate. Flow

Theoretical Pressure Drop

rate

(mm H2O/m)

(L/min) Air

20

Water

40

60

1.0

0.0000

2.0

6.2483 20.8275 32.9741

3.0

7.5479 16.6620

80

100

120

140

160 180

24.3015 35.0319 62.4825 97.1978

F

F

41.6550 83.3100

13.3296 35.9733 62.4825 124.9650

F

F

F

F

F

F

F

F

F

*F = Flooding

Table 7.5: Log Pressure Drop and Log Air Flowrate Value (Experimental) Flow rate

Log Pressure Drop

(L/min)

(mm H2O/m)

Air Water

1.3010 1.6021 1.7782 1.9031 2.0000 2.0792 2.1461 2.2041 2.2553

1.0

-

2.0

-

3.0

-

1.4064 1.7074 1.8044 2.1468 2.2515 2.5033

1.4064 1.5825 1.8835 2.1054 2.2515 2.5033

1.1054 1.4064 1.8044 2.1054 2.3607

2.6617 (F)

F

2.7182 (F) F

2.6105 (F) F

F

*F = Flooding Table 7.6: Log Pressure Drop and Log Air Flowrate Value (Theoretical) Flow rate

Log Theoretical Pressure Drop

(L/min)

(mm H2O/m)

Air Water

1.3010 1.6021 1.7782 1.9031 2.0000 2.0792 2.1461 2.2041 2.2553

1.0

-

0.8778 1.2217 1.3856 1.5445 1.7958 1.9877

F

F

2.0

0.7958 1.3186 1.5182 1.6197 1.9207

F

F

F

F

3.0

1.1248 1.5560 1.7958 2.0968

F

F

F

F

F

*F = Flooding

LAB REPORT ON GAS ABSORPTION (L8)

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Table 7.7: Data from Calculation to Determine Theoretical Pressure Drop Air

Gas Mass

Capacity

Liquid Mass Velocity

Flow Parameter

Flowrate

Velocity

Parameter

(𝑮𝒙 ) 𝐤𝐠/𝐦𝟐 𝐬

(x-axis)

(𝐕𝐲 )

(𝑮𝐲 )

(y-axis)

LPM

𝐤𝐠/𝐦𝟐 𝐬

20

0.0779

0.0011

3.3025 6.6049 9.9074 1.4566 2.9132 4.3698

40

0.1558

0.0046

3.3025 6.6049 9.9074 0.7283 1.4566 2.1849

60

0.2338

0.0103

3.3025 6.6049 9.9074 0.4855 0.9711 1.4566

80

0.3117

0.0184

3.3025 6.6049 9.9074 0.3641 0.7283 1.0924

100

0.3896

0.0287

3.3025 6.6049 9.9074 0.2913 0.5826 0.8740

120

0.4675

0.0414

3.3025 6.6049 9.9074 0.2428 0.4855 0.7283

140

0.5454

0.0563

3.3025 6.6049 9.9074 0.2081 0.4162 0.6243

160

0.6234

0.0735

3.3025 6.6049 9.9074 0.1821 0.3641 0.5462

180

0.7013

0.0931

3.3025 6.6049 9.9074 0.1618 0.3237 0.4855

1

2

3

1

2

3

LPM

LPM

LPM

LPM

LPM

LPM

Table 7.8: Percentage Error of The Experiment Water Flow

Theoretical Flooding

Experimental Flooding

Percentage Error

Rate

Air Flow Rate

Air Flow Rate

(%)

(L/min)

(L/min)

(L/min)

1

160

180

12.50

2

120

160

33.33

3

100

120

20.00

LAB REPORT ON GAS ABSORPTION (L8)

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Log Pressure Drop vs Log Air Flowrate 3.0000

2.5000

Log Pressure Drop

2.0000 Exp (1 LPM) Exp (2 LPM)

1.5000

Exp (3 LPM) Theory (1 LPM) Theory (2 LPM)

1.0000

Theory (3 LPM)

0.5000

0.0000 0.0000

0.5000 1.0000 1.5000 2.0000 Log Air Flowrate (LPM)

2.5000

Figure 4 - Log Pressure Drop vs Loq Air Flowrate The graph shows the log pressure drop increases as the log air flowrate increases. Also indicates as air flowrate increases, the pressure drop increases. At 1 LPM and 2 LPM water flowrate, the experimental data shows a higher pressure drop compared to theory but at 3 LPM water flowrate, the experimental data shows a smaller pressure drop compared to theory.

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8.0

CALCULATIONS

Density of Air,

ρy = 1.175kg/m3

Density of Water,

ρx = 996kg/m3 (R. H. Perry, 1973)

Packing Factor,

FP = 900m3

Column Diameter,

D = 80mm

Water viscosity,

μx = 0.0008 kg/ms (Bingh...