xzNAME: SHEH MUHAMMAD AFNAN BIN SEH HANAFISTUDENT NO:
2013210382GROUP: EH2214AEXPERIMENT: GAS ABSORPTIONDATE PERFORMED:
11/03/2015SEMESTER: 4PROGRAMME / CODE: PROCESS ENGINEERING
LABORATORY ( CPE 554 ) SUBMIT TO: MISS HABSAH ALWI
NO.TITLEALLOCATED MARKS (%)MARKS
1ABSTRACT / SUMMARY5
2INTRODUCTION5
3AIMS5
4THEORY5
5APPARATUS5
6METHODOLOGY / PROCEDURE10
7RESULTS10
8CALCULATIONS10
9DISCUSSION20
10CONCLUSION10
11RECOMMENDATIONS5
12REFERENCE5
13APPENDIX5
TOTAL MARKS100
REMARKS:CHECKED BY:
------------------------------------DATE:
TABLE CONTENT
NumberTitle Page
1. Abstract/Summary2
2. Introduction3
3. Aims3
4. Theory4 5
5. Apparatus6
6. Methodology/Procedure7 8
7. Results9 11
8. Calculations12 - 22
9. Discussion23
10. Conclusion24
11. Recommendations24
12. Reference25
13. Appendix26
ABSTRACT Gas absorption is a process in which a gaseous mixture
is brought into contact with a liquid and during this contact a
component is transferred between the gas stream and the liquid
stream. The gas may be bubbled through the liquid, or it may pass
over streams of the liquid, arranged to provide a large surface
through which the mass transfer can occur. The liquid film can flow
down the sides of columns or over packing, or it can cascade from
one tray to another with the liquid falling and the gas rising in
the counter flow.The gas, or components of it, either dissolves in
the liquid (absorption) or extracts a volatile component from the
liquid (desorption). In addition, there is the aim that should be
achieved at the end of the experiment which is to examine the air
pressure drop across the column as a function of air flow for
different water flow rates through the column. In packed column,
air is fed into the bottom and water is transferred to the top of
the column either from feed vessel B1 using the centrifugal pump,
P1. The pressure drop is recorded when the liquid flow rate is set
to 1.0 L/min until 3.0 L/min. The gas flow rate starts from 20
L/min until 180 L/min with 10.0L/min of intervals. How fast the
liquid can flow down with no vapor flowing upwards and the rate at
which the vapor is trying to flow upwards is the actual flooding
point.
INTRODUCTIONGas 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. A common
apparatus used in gas absorption and certain other operations is
the packed tower. 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. 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 down flow, and local accumulations or pools of
liquid start to appear in the packing. AIMS1. To examine the air
pressure drop across the column as a function of air flow for
different water flow rates through the column.2. To determine the
loading and the flooding points in the column.
THEORYThis experiment required to plot graph of pressure drop
against air flow rate in graph. The flow parameter shows the ratio
of liquid kinetic energy to vapour kinetic energy and parameter of
K4 or y-axis needs and x-axis or FLV can be calculated by using
these formulae:
Gas absorption is a process where mixture of gas is in contact
with liquid and becomes dissolve. Therefore, there is mass transfer
occurs in the component that changes from gas phase to liquid
phase. The solutes are absorbed by liquid. Inside this experiment,
only the mass transfer between air and liquid are concerned. Gas
absorption is widely use in industries to control the air pollution
and to separate acidic impurities out of mixed gas streams. The
pressure drop values are observed from the manometer. The graph of
pressure correlation for different flow rate of water is plotted in
order to find the relationship between K4 and FLV. The steps on how
to obtaine K4 and FLV is shown below:Density of air, G = 1.175
kg/m3Density of water, L = 996 kg/m3Column diameter, Dc = 80 mmArea
of packed diameter, Packing Factor: Fp = 900 m-1Water viscosity,
water = 0.001 Ns/m2
Theoretical Flooding Point 1. Gy must be in m3/h
2. To calculate gas flow rate, GG (kg/m2s)
3. To calculate capacity parameter, K4,
4. To calculate liquid flow rate, GL (kg/m2) (1 LPM, 2 LPM, 3
LPM)
5. To calculate flow parameter, FLV (1 LPM)
Where:= Air flow rate (m3/h)
APPARATUS
SOLTEQ-QVF Absorption column (Model: BP 751-B)
PROCEDUREGeneral start-up Procedures1. All the valves were
ensured closed except the ventilation valve V13.2. All the gas
connections were checked whether they are properly fitted.3. The
valve on the compressed air supply line was opened. The supply
pressure was set between 2 to 3 bar by turning the regulator knob
clockwise.4. The shut-off valve on the CO2 gas cylinder was opened.
The CO2 cylinder was checked whether the pressure is sufficient.5.
The power for the control panel was turned on.Experiment :
Hydrodynamics of a Packed Column (Wet Column Pressure Drop)1. The
general start-up procedures were performed as described above.2.
The receiving vessel B2 was filled through the charge port with 50
L of water by opening valve V3 and V5.3. Valve V3 was closed.4.
Valve V10 and V9 were opened slightly. The flow of water was
observed from vessel B1 through pump P1.5. Pump P1 was switched on,
then slowly opened and valve V11 was adjusted to give water flow
rate of arrounf 1 L/min. The water was allowed to enter the top
column K1, flew down the column and accumulated at the bottom until
it overflows back into vessel B1.6. Valve V11 was opened and
adjusted to give water flow rate of 0.5 L/min into column K1.7.
Valve V1 was opened and adjusted to give an air flow rate of 40
L/min into column K1.8. The liquid and gas flow were observed in
the column K1 and the pressure drop across the column at dPT-201
was recorded.9. Steps 6 to 7 were repeated with different values of
air flow rate, each time increasing by 40 L/min while maintaining
the same water flow rate.10. Steps 5 to 8 were repeated with
different values of water flow rate, each time increasing by 0.5
L/min by adjusting valve V11.
General Shut-Down Procedures1. Pump P1 was switched off.2. Valve
V1, V2 and V12 were closed.3. The valve on the compressed air
supply line was closed and the supply pressure was exhausted by
turning the regulator knob counter-clockwise all the way.4. The
shut-off valve was closed on the CO2 gas cylinder.5. All the liquid
in the column K1 was drained by opening valve V4 and V5.6. All the
liquid from the receiving vessels B1 and B2 were drained by opening
valves V7 and V8.7. All the liquid from the pump P1 was drained by
opening valve V10.8. The power for the control panel was turned
off.
RESULTSFlow rate(L/min)Pressure Drop(mm
airwater20406080100120140160180
1.00267910132158
2.0820393053--
3.00271339----
Table 1: Pressure Drop for Wet column
Flow rate (L/min)Air Water
1.02.03.0
Gas Flow rateLog Gas Flow ratePressure drop (mmH2O)Log Pressure
drop (mmH2O)Pressure drop (mmH2O)Log Pressure drop (mmH2O)Pressure
drop (mmH2O)Log Pressure drop (mmH2O)
201.3010-80.9030-
401.60220.30120.30120.301
601.77860.7780-70.845
801.90370.84530.477131.114
1002.0090.95490.954391.591
1202.079101301.477--
1402.146131.114531.724--
1602.204211.322----
1802.255581.763----
Table 2: Log Gas Flow rate and Log Pressure drop
Air Flow rate (L/min)Air Flow rate (m3/h)GG (kg/ms2)K4FLV (1
LPM)FLV (2 LPM)FLV (3 LPM)Pressure drop correlated in mm H20(1LPM)
(2LPM) (3LPM)
201.20.07790.01541.4542.9124.3621.525.0812.7
402.40.1560.0620.727
1.4562.1815.0810.1625.4
603.60.2340.1390.4840.9691.4528.8925.438.1
804.80.3110.2450.3640.7291.09312.740.6450.8
1006.00.3890.3830.2910.5830.87425.445.7253.34
1207.20.4670.5530.2430.486-40.6450.8-
1408.40.5450.7530.2080.416-43.1855.8-
1609.60.6230.9840.182--50.80--
18010.80.7011.2450.162--55.89--
Table 3: Theoretical Flooding PointLog Pressure drop correlated
in mm H20(1LPM) (2LPM) (3LPM)
0.180.711.10
0.711.001.40
0.951.401.58
1.101.611.71
1.401.661.73
1.611.71-
1.641.75-
1.71--
1.75--
Table 4 : Log Pressure drop correlated in mm H20
Figure 1: Graph of Log Pressure Drop against Log Gas Flow
Rate
Figure 2: Graph of Log correlated Pressure Drop against Log Gas
Flow Rate
CALCULATIONSInformation given :Density of air, air = 1.175
kg/m3Density of water, water = 996 kg/m3Column diameter, Dc = 80
mmArea of packed diameter,
Packing Factor: Fp = 900 m-1Water viscosity, water = 0.001
Ns/m2Theoretical Flooding Point for 20 L/min1. Gy = 20 L/min = 2.
Calculate gas flow rate, GG (kg/m2s)
3. Calculate capacity parameter, K4,
4. Calculate liquid flow rate, GL (kg/m2) (1 LPM)
5. Calculate liquid flow rate, GL (kg/m2) (2 LPM)
6. Calculate liquid flow rate, GL (kg/m2) (3 LPM)
7. Calculate flow parameter, FLV (1 LPM)
8. Calculate flow parameter, FLV (2 LPM)
9. Calculate flow parameter, FLV (3 LPM)
Theoretical Flooding Point for 40 L/min Gy =1. Calculate gas
flow rate, GG (kg/m2s)
2. Calculate capacity parameter, K4,
3. Calculate flow parameter, FLV (1 LPM)
4. Calculate flow parameter, FLV (2 LPM)
5. Calculate flow parameter, FLV (3 LPM)
Theoretical Flooding Point for 60 L/min Gy =1. Calculate gas
flow rate, GG (kg/m2s)
2. Calculate capacity parameter, K4,
3. Calculate flow parameter, FLV (1 LPM)
4. Calculate flow parameter, FLV (2 LPM)
5. Calculate flow parameter, FLV (3 LPM)
Theoretical Flooding Point for 80 L/min Gy =1. Calculate gas
flow rate, GG (kg/m2s)
2. Calculate capacity parameter, K4,
3. Calculate flow parameter, FLV (1 LPM)
4. Calculate flow parameter, FLV (2 LPM)
5. Calculate flow parameter, FLV (3 LPM)
Theoretical Flooding Point for 100 L/min Gy =1. Calculate gas
flow rate, GG (kg/m2s)
2. Calculate capacity parameter, K4,
3. Calculate flow parameter, FLV (1 LPM)
4. Calculate flow parameter, FLV (2 LPM)
5. Calculate flow parameter, FLV (3 LPM)
Theoretical Flooding Point for 120 L/min Gy =1. Calculate gas
flow rate, GG (kg/m2s)
2. Calculate capacity parameter, K4,
3. Calculate flow parameter, FLV (1 LPM)
4. Calculate flow parameter, FLV (2 LPM)
5. Calculate flow parameter, FLV (3 LPM)
Theoretical Flooding Point for 140 L/min Gy =1. Calculate gas
flow rate, GG (kg/m2s)
2. Calculate capacity parameter, K4,
3. Calculate flow parameter, FLV (1 LPM)
4. Calculate flow parameter, FLV (2 LPM)
5. Calculate flow parameter, FLV (3 LPM)
Theoretical Flooding Point for 160 L/min Gy =1. Calculate gas
flow rate, GG (kg/m2s)
2. Calculate capacity parameter, K4,
3. Calculate flow parameter, FLV (1 LPM)
4. Calculate flow parameter, FLV (2 LPM)
5. Calculate flow parameter, FLV (3 LPM)
Theoretical Flooding Point for 1800 L/min Gy =1. Calculate gas
flow rate, GG (kg/m2s)
2. Calculate capacity parameter, K4,
3. Calculate flow parameter, FLV (1 LPM)
4. Calculate flow parameter, FLV (2 LPM)
5. Calculate flow parameter, FLV (3 LPM)
PERCENTAGE ERROR %1LPM Total correlated pressure drop = 243.38
mm H20Total pressure drop = 126 mm H20
2LPM Total correlated pressure drop = 177.8 mm H20Total pressure
drop = 105 mm H20
3LPM Total correlated pressure drop = 180.3mm H20Total pressure
drop =61 mm H20
DISCUSSION
For this experiment, the aim is to determine the pressure drop
correlation for different flow rate of water 1 LPM, 2 LPM and 3
LPM. The air flow rate increased as the pressure drop in the dry
packed column increases. These occur due to the air flow rate
increased results of increasing in resistance for the water to
flows down the column and give high pressure drop across the
packing. In the graph of log pressure drop against log gas flow
rate, the log air flow rate increase as the log pressure drop is
also increase. The air flow rate increase as the pressure drop
increase in constant flow of water. At 1 LPM, the pressure drop is
the lowest water flow rate compared to the other two flow rate.
This is because of the space for gas flow is blocked by the liquid
that flows sown the column. The water flows down due to the
gravitational force and thus the gas flows in a counter-current
direction with water. During this experiment, there are some
resistances occur in the column such as the gas from the bottom
starts to impede the water flowing down the column and overflow of
water. Because of that, the graph in figure 1 differ from
theoretically graph which is 1 LPM should be a straight line while
the other two flow rate which is 2 LPM and 3 LPM should be parallel
to the graph 1 LPM. From the calculation of K4 and FLV, the plotted
graph is obtained. The relationship between the plotted graphs is
K4 is inversely proportional to FLV. As the value of FLV increase,
the value of K4 decreases. This shows that the relationship of
pressure drop and gas flow rate is increasing linearly. Then those
values can use to generalize correlation for pressure drop in
packed column in chart shows in Appendix. Theoretical generalized
correlation charts show that the high flow parameters are typical
of high liquid rates and high pressure drop. However, by looking at
both of graph, it shows difference of value pressure drop in
theoretical and experimental. Percentage error of pressure drop in
1LPM is 48%, 2LPM is 46% and 3LPM is 5.08%. This is due to overflow
during experiment is carried on. It also might be due to minor
leaking when the experiment is being carried out. Minor leaking
will affect the flow rate of both water and air thus affecting the
pressure drop. When the gas flow rate increased, pressure drop
increased and some of the water will trapped in packing. Later, the
water from bottom will increase until the highest level and this
will results in flooding. Flooding point is the highest point for
each line in the graph of pressure against gas flow rate. When this
happen, the process can be no longer be conducted because there is
too much liquid entrainment. The flooding points occur at 180
L/min,140 L/min in and 100 L/min for 1LPM,2LPM and 3LPM
respectively.CONCLUSIONIn conclusion, the pressure drop will
increase when the gas flow increased at constant water flow rate of
1 LPM to 3 LPM. The gas was absorbed through the packed column in a
batch process in absorption of air and the effect of liquid flow
rate on the absorption-adsorption process was observed. As the flow
rate of air increased, the absorption-adsorption process also
increased as the composition of the outlet volume of air increased
over time. The resistance to of water flows down the column due to
the increasing water flow rate. As for the theoretical value, the
same principle is used based on the pressure drop correlation
charts as well as the experimental value. However, there are are
different value in pressure drops value as there are some error
occur which can prevent in recommendation. From the experiment, the
value of experimental pressure drop is lower compared to the
correlated values for packed column.RECOMMENDATIONThere are some
recommendations that should be taken account into to ensure the
experiment to become more accurate which are the valve controlling
the level of water flowing back to the water reservoir should be
constantly checked so that we can get a better reading. The level
of water must be higher than the bottom of the reservoir. This need
to be done to avoid air being trapped in line. Beside that, Make
sure all the valves are closed before using the column so that the
experiment runs smoothly. Moreover, Make sure the gas and liquid
flow rates were constant at that particular flow rate Then, the gas
and liquid flow rates must be constant at that particular flow
rates. Then, collect the samples simultaneously from both inlet and
outlet of the packed column. Furthermore, Give the experiment some
more time before the results are taken.
REFERENCES1. Transport Process and Separation Process Principles
(Includes Unit Operations) 4th Edition, Christie John Geankoplis,
Pearson Education Inc2. Principle of Gas Absorption retrieved from
http://pubs.acs.org/doi/abs/10.1021/ie50180a0023. Gas Absorption
Lab Manual4. http://separationprocess.com/5. Principle of Gas
Absorption retrieved from
http://pubs.acs.org/doi/abs/10.1021/ie50180a002
APPENDIX
26