ng lab report as at 2012
DESCRIPTION
Natural gas lab reportTRANSCRIPT
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School of Computing, Science and Engineering
MSc petroleum and Gas Engineering
MODULE 1: FUNDAMENTALS OF NATURAL GAS & PRODDUCTION SYSTEMS
& DESIGN
LECTURER: Dr. Martin Burby
LABORATORY REPORT ON: CALORIFIC VALUE OF NATURAL GAS, RELATIVE DENSITY, AERATION TEST BURNER NUMBER AND ANALYSIS OF NATURAL GAS COMBUSTION PRODUCTS
NAME: OPEYEMI OSHO ROLL NUMBER: @00344819
DATE OF EXPERIMENT: 19TH OCTOBER, 2012 DATE OF REPORT DUE: 14TH DEC, 2012
GROUP 4 MEMBERS: Mr. Otunwa Gerald; Mr. Oluyide Oladipupo; Mr. Ukaeru Chinedu; Mr. Uyoyo – Ghene Okoro; Mr. S.Petrus; Mr. A.Raj; Miss. V.Juclcileia; Mr. P .Mattaios; Mr. M. S. Hamza; Mr. A. Mohammed; Mr. A .S .Tahir; Mr. M. Liman; Mr. Obaro Ogezo; Mr. O. Y. Samuel
TEACHING ASSISTANT: MR. Abu-Bakr Abbas and Mr. Alan Mappin
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Table of Contents LIST OF FIGURES ............................................................................................................................................ 3
LIST OF TABLES .............................................................................................................................................. 3
EXPERIMENT 1: DETERMINATION OF CALORIFIC VALUE OF NATURAL GAS ........................................ 4
Bibliography .................................................................................................................................................. 9
EXPERIMENT 2: DETERMINE RELATIVE DENSITY (SPECIFIC GRAVITY) ........................................................ 10
OBJECTIVE ................................................................................................................................................. 10
INTRODUCTION ........................................................................................................................................ 10
THEORY ....................................................................................................................................................... 10
EXPERIMENTAL SET-UP/ APPARATUS .................................................................................................. 11
PROCEDURE .............................................................................................................................................. 12
RESULTS ....................................................................................................................................................... 13
ANALYSIS ..................................................................................................................................................... 13
DISCUSSION ................................................................................................................................................. 14
CONCLUSION ............................................................................................................................................... 14
REFERENCES ............................................................................................................................................ 15
APPENDIX 1: Relative Density Correction table. ................................................................................. 16
EXPERIMENT 3: ANALYSIS OF NATURAL GAS COMBUSTION PRODUCTS .................................................. 17
OBJECTIVE ............................................................................................................................................... 17
INTRODUCTION ....................................................................................................................................... 17
EXPERIMENTA SET-UP/ APPARATUS ....................................................................................................... 17
PROCEDURE OF THE EXPERIMENT .......................................................................................................... 20
RESULT .................................................................................................................................................... 21
DISCUSSION AND CONCLUSION .............................................................................................................. 21
RFERENCES .............................................................................................................................................. 22
EXPERIMENT 4: AERATION TEST BURNER NUMBER ................................................................................... 23
OBJECTIVE ............................................................................................................................................... 23
BACKGROUND AND THEORY ................................................................................................................... 23
EXPERIMENTAL SET-UP ........................................................................................................................... 23
EXPERIMENTAL PROCEDURE................................................................................................................... 24
RESULTS AND DATA ................................................................................................................................ 24
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ANALYSIS ................................................................................................................................................. 25
DISCUSSION ............................................................................................................................................. 26
CONCLUSION ........................................................................................................................................... 26
REFERENCES ............................................................................................................................................ 27
LIST OF FIGURES Figure 1 Layout of the experiment (Elevated View) ..................................................................................... 5
Figure 2 Boys Calorimeter ............................................................................................................................. 5
Figure 3 Simmance S.G bell ......................................................................................................................... 11
Figure 4 Hand Operated Aspirator analyser ............................................................................................... 17
Figure 5 Draeger Tube Analyser .................................................................................................................. 18
Figure 6 Kane May Gas Analyser ................................................................................................................. 19
Figure 7 Infra Red Analysis .......................................................................................................................... 19
Figure 8 ‘SIGMA’ AERATION TEST BURNER ................................................................................................. 24
LIST OF TABLES Table 1 readings from the experiment taking both inlet and outlet temperatures ..................................... 7
Table 2 Experimental Results for Relative Density of Methane and Butane .............................................. 13
Table 3 Experimental Results for Analysis of Natural Gas Combustion Products ...................................... 21
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EXPERIMENT 1: DETERMINATION OF CALORIFIC VALUE OF NATURAL GAS
OBJECTIVE
This experiment is carried out and their aim is the Determination of Calorific Value of Natural Gas using a
boys’ non-recording calorimeter.
Introduction
Calorific value (CV), which is also known as heating value (HV) is a measure of heating power and is
dependent upon the composition of the gas. The CV refers to the amount of energy released when a
known volume of gas is completely combusted under specified conditions. The CV of gas, which is dry,
gross and measured at standard conditions of temperature and pressure, is usually quoted in mega
joules per cubic meter ,
.
Fuel gas which contains hydrogen or hydrocarbon possess two CV the gross and the net. The heat
of combustion for fuels is expressed as the HHV, LHV, or GHV, and thus is defined below
as follows:
Gross calorific value is the overall heat content of the gas, as defined above, when all the water which is formed in the combustion process o f gas is condensed at constant temperature, while Net calorific value is the amount of heat released by combusting a specified quantity (initially at 25°C) and returning the temperature of the combustion products to 150°C, which assumes the latent heat of vaporization of water in the reaction products is not recovered. The heating values for gaseous fuels in units of Btu/lb. are calculated based on the heating values in units of Btu/ft3 and the corresponding fuel density values. The heating values for liquid fuels in units of Btu/lb. are calculated based on heating values in units of Btu/gal and the corresponding fuel density values.
The calorific value, CV of natural gas is measured in this experiment by the calorimeter precisely (Boys
Calorimeter). This was achieved by complete combustion of the natural gas at atmospheric pressure and the CV
was measured by the calorimeter at constant pressure.
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DESCRIPTION OF EXPERIMENT/ APPARATUS
In this experiment the major apparatus, is the calorimeter being used, but before listing the apparatuses used in this experiment, I provided below a block schematic diagram and a pictorial view of the experimental setup and position of the apparatus in this experiment.
Figure 1 Layout of the experiment (Elevated View)
Figure 2 Boys Calorimeter
Now, the following apparatuses were used in the experiment that is as followed:
graduated glass vessel
Boys calorimeter
Thermometers
Hyde meter
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Boys’ Calorimeter: this instrument was invented by Sir Charles Boys, and its
essence is to determine the calorific values of a broad range of gas fuels currently
being utilized. From the layout, it was attached to a Hyde gas meter with a
capacity of 0.02 foot-cube per revolution (
), and below is a diagram of both the
calorimeter and the Hyde type gas meter. (Naveen, 2012)
Figure 2: Boys’ calorimeter and Hyde gas meter
EXPERIMENTAL ROUTINE
The following, outlines the routines undertaken for the operation, and thus as followed below:
The gases from the CH4 cylinder is switched on and kindled.
Water switched on and the calorimeter placed on its base.
The flow of gas into the calorimeter is to be adjusted in a way that the time for a revolution of
the meter, hands falls within the limits, being deduced from the formulae below:
T (min) =
T (max) =
Where, CV= theoretical calorific value in
; T= time in seconds (s).
The rate of water flowing through the calorimeter must be altered, so that the quantity obtained
during 4 revolutions of the meter hand is around 50 ml of the value of the anticipated CV. Water
must be drained, until it starts to run out of the condensate outlet pipe.
The calorimeter must then be allowed to come to rest, until temperatures from both inlet and outlet
thermometers become constant, thus the following was observed during the period of experiment
on the meter indicator.
a) At the 3 o’ clock position, the inlet thermometer is read. At the instant when the meter hand
reaches 12 o’ clock position, the change at the funnel with redirected to change the flow of
water from the outlet into a container.
b) When the meter hand, get to 3 o’ clock position again, the 1st reading of the outlet thermometer
is made and this thermometer is also read at successive quarter of the meter, until 14 reading
have been attained. The meter hand will be at the 6 o’ clock position.
c) After the 1st reading of the inlet thermometer is gotten, future readings are being made when
the meter hand is between 12 and 3 o’ clock giving 4 inlet thermal readings.
d) When the meter hand reaches 12 o’ clock for the last reading of the outlet thermometer, the
funnel is redirected away from the container.
Readings of the meter temperature, barometer, and pressure of gas at the inlet to the meter must
be measured. The former reading must be added to the barometer for the total pressure, after
making the necessary conversions to consistent units.
The volume of water collected during the experiment is measured and recorded in kg. (Burby &
Nasr, 2012)
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DATA
Barometric pressure= 754.75 mmHg, thus pressure (gauge) =
Gas pressure=20 mbar
Room temperature = 23°C, thus 23+273= 296k
Water obtained = 1229 ml of water=1.299 kg.s
Total pressure = 1005.3 + p.t
Below is the tabular readings drafted from the experiment carried out.
Water temperature °C
Number of cycles
1
2
3
4
Average
outlet
32.40
32.40
32.40
32.35
32.45
32.48
32.48
32.49
32.49
32.48
32.47
32.45
32.47
32.48
32.48
32.49
32.45
inlet
16.50
16.54
16.53
16.50
16.52
Table 1 readings from the experiment taking both inlet and outlet temperatures
ANALYSIS
CV=
Where,
T= change in temperature °C
W= weight of water obtained, Kg
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S= specific heat of water= 1
F= conversion factor for CV from
TO
V= volume of gas burnt during the test (corrected to MSC).
Therefore, converting CV in BTU/ft³, the conversion factor, F, has the value.
F=
Thus, CV in BTU/ft³= = = 1028.85
Conversion of C.V in
, first find the conversion factor, F.
F=
C.V = = 37.002
SUMMARY OF RESULTS
Calorific value in
was 1028.85 and for that of the
was 37.002.
DISCUSSION
The heating value of a gas is of paramount importance in contrasting factors of gases and seriously
needs a high stability in its environment for its measurement, and determining it should be achieved
with high accuracy. In this experiment we recorded 37.002
as compared to the actual reading of
37.97
. Also, the error in the experiment is high minimal with a percentage error of 0.99 %, and this is
due to measurement error. The derivation from the actual reading, which is to be noted as precautions
are as followed:
Interaction with surrounding gases.
Parallax errors from reading measurements
Heat loss due to radiation
Laboratory condition, thus environmental state in which the experiment is performed.
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CONCLUSION
We obtained a heating value of 37.002
, which appears to differ slightly from the actual heating value
due to the errors listed, and other conditional or experimental factor, which will affect the commercial
value of the gas, which therefore, means that using boys’ calorimeter instead of bomb calorimeter is
preferable for more accurate result.
Bibliography Burby, M., & Nasr, G. (2012). Gas and Petroleum Laboratory Experiment Manual. salford: University
Press.
Naveen, M. (2012, November 7). CALORIMETERS. Retrieved November 18, 2012, from Deepthi
Engineering: http://www.deepthiengineering.net/calorimeters.html
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EXPERIMENT 2: DETERMINE RELATIVE DENSITY (SPECIFIC GRAVITY)
OBJECTIVE
The objective of this experiment is to investigate and determine the Relative Density of given sample of natural gas and butane using ‘Simmance’ Specific Gravity Bell.
INTRODUCTION
Relative Density (Specific Gravity) is the ratio of the density of given fluid to the density of a reference fluid under the same temperature and pressure. It is applicable to both liquid and gaseous state of existence of fluid. When used for gases as in this experiment, the relative density is the ratio of the density of a given gas to the density of air at the same temperature and pressure.
Relative density has diverse application in both petroleum and other allied industries (e.g. to determine the Wobbe Number).
In this experiment using ‘Simmance’ Specific Gravity Bell, the time taken for a volume of the test gas (Methane and Butane) to effuse through an orifice in the ‘Simmance’ Bell is compared with that taken by the same volume of air under identical condition.
THEORY
The determination of the Relative Density in this experiment is based on the Graham’s law of diffusion which states that, given constant temperature and pressure, the diffusion/effusion rate of two gases are inversely proportional to the square root of their respective densities as shown in the equation below:
Where:
𝑅𝐴= 𝑅 𝑡𝑒 𝑜𝑓 𝑑𝑖𝑓𝑓𝑢𝑠𝑠𝑖𝑜𝑛 𝑜𝑓 𝑔 𝑠 𝐴
𝑅𝐵= 𝑅 𝑡𝑒 𝑜𝑓 𝑑𝑖𝑓𝑓𝑢𝑠𝑠𝑖𝑜𝑛 𝑜𝑓 𝑔 𝑠 𝐵
𝑑𝐴= 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 𝑜𝑓 𝑔 𝑠 𝐴
𝑑𝐵= 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 𝑜𝑓 𝑔 𝑠 𝐵
Also:
𝑅𝐴=
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𝑅B=
Where:
𝑉𝐴=𝑉𝑜𝑙𝑢 𝑒 𝑜𝑓 𝑔 𝑠 𝐴 𝑒𝑓𝑓𝑢𝑠𝑒𝑑
𝑉𝐵=𝑉𝑜𝑙𝑢 𝑒 𝑜𝑓 𝑔 𝑠 𝐵 𝑒𝑓𝑓𝑢𝑠𝑒𝑑
𝑡𝐴=𝑇𝑖 𝑒 𝑡 𝑘𝑒𝑛 𝑓𝑜 𝑔 𝑠 𝐴 𝑡𝑜 𝑒𝑓𝑓𝑢𝑠𝑒
𝑡𝐵=𝑇𝑖 𝑒 𝑡 𝑘𝑒𝑛 𝑓𝑜 𝑔 𝑠 𝐵 𝑡𝑜 𝑒𝑓𝑓𝑢𝑠𝑒
EXPERIMENTAL SET-UP/ APPARATUS
In this experiment, the major and only apparatus used was a simmance specific gravity bell which comprises of a small water tank in which a bell is suspended from a beam carrying a pointer. The pointer moves over a scale plate on which are engraved two lines, corresponding to the upper and lower heights of the bell between which the time of effusion is measured. A balance weight is fitted to other end of the beam so that the rate of effusion can be controlled. An orifice of 0.8mm in diameter which is protected by a removable dust cap is mounted on a nipple fitted to the top of the bell. The bell is connected by a cord to the beam with the cord resting on a quadrant arm to maintain the bell in the center of the tank. Gas or air can be introduced into the bell through either of 2 cocks which are attached by a connecting tube to a standpipe located inside the bell. Below is a photograph of the apparatus.
Figure 3 Simmance S.G bell
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PROCEDURE
To carry out this experiment, the following procedure was taken into actions, which are:
We now partake by means of leveling screws, so as the bell hangs at the center inside the tank. Occupy the tank with water until the dome of the bell is just covered when the bell is static.
Calibrate the scale, so the indicating punch mark is level with the pivots which is carrying the beam and also set the cord that is attaching the bell to the beam, so that the pointer is about 2cm below the lower mark on the scale , when is bell is static.
Remove the cap covering the orifice from in a scheduled manner in order to examine the orifice. If dust or moisture has accumulated, try to remove it with a soft brush and clean the orifice with a splinter for soft wood. Polish, so as to avoid parallax errors.
Connect one of the cocks to the gas supply leaving the other disconnected, so that air can enter as required.
Lock the gas cock, and open the other cock to air. Fill the bell with air by slowly depressing the free end of the beam until the pointer is well above the upper mark on the scale and then allow the bell to immerse slowly into the water until it covers the bell crown. Repeat this scenario to purge the gases inside, except air.
Observation was made for the time of effusion of Air for the three cases using stop watch.
Similarly, the bell was filled with other gases (Methane and Butane) one at time as in the case by allowing the bell to rise under gas pressure.
Again the gas (Methane or Butane) was allowed to effuse and the time of effusion recorded
The effusion time for each of the three gases (air, methane and butane) for the three cases was recorded form which an average effusion time was obtained for each gas.
The cap covering the orifice was examined time to time in order to examine the orifice.
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RESULTS
The following results were obtained from the experiment, and it is tabulated below:
GASES TIME average
AIR 56.35 56.18 56.68 56.40
METHANE 48.50 48.70 47.90 48.37
BUTANE 82.80 83.73 82.86 83.13 Table 2 Experimental Results for Relative Density of Methane and Butane
CONDITIONAL DATA
Barometric pressure= 754.75 mmHg
Room temperature= 22⁰C
Temperature of water inside the tank= 21⁰C
ANALYSIS
From Graham’s law, we then find the relative densities of methane and butane, which the
equation; 𝑒𝑙 𝑡𝑖 𝑒 𝑑𝑒𝑛𝑖𝑠𝑡𝑦 𝑜𝑓 𝑔 𝑠 (
)
So for methane,
𝑅 𝐷 𝑒𝑡 𝑛𝑒 (
)
And for butane,
𝑅 𝐷 𝑢𝑡 𝑛𝑒 (
)
Thus, the uncorrected relative density for both methane and butane are 0.736 and 2.172 respectively.
Using the uncorrected data, we correct to dry basis by applying the correction gotten from the table. And the formula used for this scenario is:
𝑅𝑒𝑙 𝑡𝑖 𝑒 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 𝑛 𝑜 𝑒 𝑡𝑒𝑑 𝑅𝑒𝑙 𝑡𝑖 𝑒 𝐷𝑒𝑛𝑠𝑖𝑡𝑦
Where c = corrected value of relative density, and it is obtained from the table in appendix 1, at 22⁰C.
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For methane, this is 0.735. We find the exact error of percentage using interpolation from the table, and it is within the range of 0.7-0.8.
Thus, x = 0.00428, and C= 0.736 – 0.00428= 0.731
Similarly, for butane which is at 2.172, using extrapolation method from the table, it is within the range of 1.20-1.10.
Thus, x =0.0234, and C= 2.172 + 0.0234= 2.195
DISCUSSION
In this experiment, the relative density of methane and butane differ a little from the values commonly used by industries and academia. For instance, in Britain, relative density for methane is 0.6 and that of butane is 2.0 as to the ones gotten from the experiment which are 0.731 and 2.195 respectively. The utterance of the values might be due to the following:
Error in experiment and measurement due to parallax.
Solubility of methane and butane gases in water
Remains of contaminants in the equipment, which result to a much denser result, 0.735 for methane.
Despite considering all factors of errors, this experiment is slight closer to the factual values which , thus could be improve to attained to that value.
CONCLUSION
The scope of the determination of relative density of methane and butane was attained.
Future considerations for the development of the specific gravity bell for better accuracy in measurement of sample gases.
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REFERENCES
1) University of Salford School of Computing, Science and Engineering
2) Determination of Relative Density of Methane and Butane Gas using (‘SIMMANCE’
SPECIFIC GRAVITY BELL) Manual.
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APPENDIX 1: Relative Density Correction table.
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EXPERIMENT 3: ANALYSIS OF NATURAL GAS COMBUSTION PRODUCTS
OBJECTIVE
To measure the oxygen, carbon dioxide and carbon monoxide contents of combustion products from a
natural gas burner.
INTRODUCTION
This experiment deals with the combustible products that are contained in combustible
compound usually organic compounds. The amount or extent of these combustible products in
the analysed compound characterised the combustion quality of the compound. As such, the
knowledge of this amount of combustion products (carbon dioxide, carbon monoxide & oxygen)
contained is important in the combustion analysis of the compound and the design of the burner
that is suitable for its burning.
More so, the experimental result finds its application in the determination of fuel gas air ratio
which is important in the extraction of maximum energy from the fuel.
EXPERIMENTA SET-UP/ APPARATUS
The equipment used in this experiment is:
Fyrite analyser: This utilises the technique of chemical absorption whereby the sample of the
gas to be analysed is bubbled through a liquid that absorbs the particular constituent being
analysed. Below is a schematic diagram of this analyser.
Figure 4 Hand Operated Aspirator analyser
Absorbent
fluid
Flexible
diaphragm
Adjustable
scale
Spring loaded
double seated
plunger valve
Sample
reservoir
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Drager tube: This is a simple rapid acting device that may be used to determine the presence of
a gas in air or fuel gases. The detector comprises of a hand held bellows pump into which is
fitted a tube containing a solid absorbent impregnated with a reagent that reacts with the
constituent being analysed. Below is the tool in a schematic diagram.
Figure 5 Draeger Tube Analyser
Paramagnetic oxygen analyser: This measures the magnetic susceptibility of the sample gas.
Only a few gases, including oxygen and nitrogen oxides are paramagnetic (exhibit a positive
magnetic susceptibility), with the vast majority exhibiting a negative magnetic susceptibility.
Below is a picture of this tool.
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Figure 6 Kane May Gas Analyser
Infrared analyser: This utilizes the fact that compound gases such as carbon monoxide and
carbon dioxide selectively absorbs long- wave radiation. The sample to be analysed is held in a
measuring tube through which filtered radiation passes and absorption occurs at wavelengths
characteristics of the gases. Below is a schematic diagram of this tool.
Figure 7 Infra Red Analysis
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PROCEDURE OF THE EXPERIMENT
This experiment was carried out in 4 stages, which are:
The first stage of the experiment was when the burner was place beneath the sampling hood
with the air shutter fully opened and damper closed.
The oxygen analyser was initially set at zero by nitrogen through the tool. Air was passed though
the tool and the span control was calibrated.
Other measurement tools were connected and linked via the operation manual as instructed.
The burner was ignited, and exhaust gas linked to al the measurement tools were collected.
For the Bacharach fyrite, it was first adjusted with the horizontal level of fluid to a mark of zero (rest) on
the scale.
1. The exhaust gas was gotten from the sampling hood by pumping 18 times only when the Bunsen
burners’ shutter was opened.
2. The suctioned gas was switched in a reciprocating positions for about 3 times, to reach proper
contact with the reagent (CO₂ analysis)
3. We obtained the reading from a calibrated cylinder.
4. At the top of the cylinder, was taken out and gas escaped from the fluid. This routine is repeated
during the closed session of the shutter.
For the Draeger Analysis Tube, the following is being listed below:
1. The tubes carefully broken at both end and were used to obtained samples of the exhaust gas
through the sampling hood.
2. Various tubes were used for oxygen and carbon dioxide analysis.
3. The sample was taken by means, a bellow type pump to suck the sample into a tube.
4. The concentration of the gases decolorized, the reagent which was obtained through reading
5. This routine was repeated when the shutter was closed.
For Infra-Red Analyser, the following is being listed below:
1. The apparatus was at first adjusted by using the zero and span buttons to ensure that it
produced accurate gas values.
2. Sample of the exhaust gas was obtained from the sampling hood, when the burner shutter was
open.
3. Reading of the concentration of oxygen and carbon dioxide were taken after fine tuning the
meter.
4. This routine was repeated for the closed session of the shutter.
For the Kane May apparatus, the following is being listed:
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1. The tool was turned on and allowed to initial sequence
2. Then, the sample of the exhaust gas was collected from the sampling hood, when the shutter of
the burner was open.
3. Values of the concentration of oxygen, carbon monoxide, and carbon dioxide were collected
after fine tuning the meter.
4. This routine was repeated for the closed session of the shutter.
RESULT
Analysis of Natural gas Combustion Products
Air Shutter Open
Air Shutter Closed
CO CO₂ O₂ (18
pumps)
No× CO CO₂ O₂ NO× Temperature
Bacharach Fyrite 0.5% 19% 4.5%
Infra-Red 0.0003% 0.97% 0.062 7.07
Kane-May 6 PPM 1% 19.2% 451 PPM
6.3% 9.8 189°C (Open) 275°C (Closed)
Paramagnetic
Drager Tube 6 PPM 1.5% 500 PPM
5.8%
Table 3 Experimental Results for Analysis of Natural Gas Combustion Products
Infra-red reading for CO: CO₂ (Open) = 0.0005%
Kane-May reading for CO: CO₂ (Open) = 0.0005
Infra-red reading for CO: CO₂ (Closed) = 0.0095
Kane-May reading for CO: CO₂ (Closed) = 0.01
DISCUSSION AND CONCLUSION
In the experiment, the results obtained from the analysis of natural gas combustion products, which we
used the tools and methods mentioned early in the report like the Bacharach fyrite, Draeger tubes,
Infra-Red, and Kane May with a Bunsen burner which was fully opened (complete combustion), and also
which was closed (incomplete combustion). My observation was the Carbon monoxide content is high
when the shutter was closed, compared to when it’s opened. This explains the reasons CO is produced
in the process of incomplete combustion because of minimum oxygen during combustion. Another of
my observation, was that oxygen content required for combustion is very high when the shutter is open,
than when it’s closed. So therefore, we conclude that the shutter closed operating conditions indicates
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incomplete combustion and vice versa. And also most of the oxygen required for the combustion is
collected from air.
RFERENCES
1. Laboratory manual on Analysis of Natural Gas Combustion Products, 2009. School of
Computing, Science & Engineering. University of Salford, United Kingdom.
2. Connor, N.E and Nasr, G.G (2000) “Basic Units of Measurement, Gas Supply and
Combustion”. School Of Computing, Science and Engineering, University of Salford,
United Kingdom.
3. www.inspectapedia.com. Accessed December 5, 2011
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EXPERIMENT 4: AERATION TEST BURNER NUMBER
OBJECTIVE
The scope of this experiment is to determine the aeration test burner number (A.T.B No.) of a sample of
natural gas.
BACKGROUND AND THEORY
The study of the behaviour of aerated burners is complex involving the burning velocities of the
constituent gases and their air inducing properties. Attention has, therefore, been concentrated on the
manufacture of a standard test burner which will enable an empirical relationship to be attained which
gives a signal of the relative combustion features of different gases. The A.T.B is such a burner and has
been standardized as the official test burner.
To determine the A.T.B number was completed alongside assistance of the Sigma’s Monogram for A.T.B
Indicator (Type 600) alongside calibration chart no. 9267. The instrument reading was seized from the
reading on the shutter working manipulation corresponding to the mean locale of the inner flame of the
blaze at the fiducial point.
EXPERIMENTAL SET-UP
The main and only apparatus in this experiment is the aeration best burner, which is defined as a burner
for measuring the features of the combustion of commercial gases, (Barach). The burner comprises of a
Bunsen burner with a fixed gas orifice operating at standard pressure. A primary air-shutter which is
manually adjusted to provide an inner cone of specific height. The degree of the opening of the shutter
is indicated as a scale calibrated in “Tens” and “units” on the shutter operating control. The whole unit is
enclosed in a fire resistant cabinet with chromium fittings. It has a manometer for determining the
differential/gauge pressure of the gas and a burner jacket through which the cooling water flows. A
governor is fitted to the shutter operating controls which adjust the gas pressure to 20 mbar. Below is a
photograph of the aeration test burner, and a schematic view
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Figure 8 ‘SIGMA’ AERATION TEST BURNER
EXPERIMENTAL PROCEDURE
The burner should be connected to a gas supply at a pressure of not less than 22 mbar, and
calibrate the governor to 2o mbar.
Correct the flow of water passing through the burner jacket between 200-500 ml/minute, and
maintain temperature within 10-20⁰C, and ignite the burner.
Slowly and carefully open the shutter until the tip of the inner core of the flame is brought to
the reference mark, and don’t take any reading until the burner has being in combustion for 5
minutes.
As slight oscillation of the inner core of the flame, correct the air-shutter, so that the mean
position of the tip corresponds with the reference line, and take the reading on the scale. And
now use this reading, and read off the A.T.B number from the calibration chart.
RESULTS AND DATA
The result gotten from the aeration test burner scale was 32, and from the chart the A.T.B number is
385. Thus, finding the wobbe number of natural gas, commercial propane and butane, the following
data below is used to obtain it:
Conditional Data
Calorific value of propane= 2500
Calorific value of butane= 3200
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Calorific value of natural gas= 1028.85
or 37.002
; relative density= 0.715
Barometric pressure= 754.54 mmHg
Temperature of water= 15-20 ⁰C
ANALYSIS
CALCULATE WOBBE NUMBER OF CH4, PROPANE AND BUTANE
The formula for wobbe number of a gas =
For natural gas, using the unit of British thermal unit per cubic foot,
Wobbe number =
For S.I units,
Wobbe number =
For commercial propane, to find relative density
Relative density=
; where Mwt= molecular weight
So Mwt (propane) = 44; and Mwt (air) =28.97
Thus R.D= 44÷28.97=1.52
So therefore, wobbe number=
,
Now for S.I units, converting to
,
Calorific value in
Thus, wobbe number of propane=
And finally for commercial butane,
The relative density =
Thus, wobbe number =
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And for S.I unit, converting to
𝑉
The wobbe number of butane=
.
DISCUSSION
In the experiment for A.T.B. of Natural gas, a value of 385 was obtained which falls within the
acceptable range of A.T.B in Britain. This may as source of gas changes. Other calculated values
of Wobbe Numbers of Methane, Propane and Butane. The accuracy of the above results obtained
was limited by source/origin of the sample gas and the empirical formulae used the
determination of the Wobbe Numbers. For instance, the molecular weights of the gases under
study were all approximated values and not a generic representative of the three gases considered
especially in Britain.
In the case of Methane, there could be some amount of contaminants as the gas flows from the
mains resulting in a slightly heavier relative density value of 0.67.
Error due to parallax while taking the reading from the chart.
The relative density of Butane could be affect by the structure of the butane used in the
experiment e.g. Iso-butane and n-butane.
Insufficient primary air in the laboratory giving rise to more diffusion flame.
Condition of the test environment
In spite of the aforementioned challenges in carrying out this experiment and the calculations, it
gave an indication of the significance of these parameters in gas quality specification and
monitoring.
CONCLUSION
From the experiment, it was observed that the higher the Wobbe number, the greater the heating
value of the quantity of gas that will flow through a hole of a given size in a given amount of
time. The ATB number gives an immediate indication of the combustion characteristics of gas under test.
It also helps determine gases present in a mixed gas of different characteristics In almost all gas
appliances, the flow of gas is regulated by making it to pass through a hole or orifice. Such that
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for a given orifice, all gas mixtures that have the same Wobbe number will deliver the same
amount of heat. The Wobbe number is also a critical factor to minimize the impact of
changeover when analyzing the use of substitute natural gas (SNG) fuels such as propane –air
mixture. Wobbe number is an indicator of the interchangeability of fuel gases such as natural gas
and LPG.
The Calorific value of the fuel gases when related to the Wobbe number is a measure of the
heating power and the amount of energy released when a known volume of gas is completely
combusted under specified conditions. The higher the calorific value, the greater the Wobbe
number.
The objective of determination of the A.T.B. Number of Natural gas and the calculation of the
Wobbe numbers of other fuel gases were achieved. These parameters (Calorific valve, Relative
density, A.T.B. No. and Wobbe No.) are of great importance in the industry.
However, Relative density has an inverse relation with Wobbe number, such that the higher the
relative density, the lower the Wobbe number-a measure of the interchangeability of fuel gases.
REFERENCES
University of Salford School of Computing, Science and Engineering: The Aeration Test
Burner section from Gas and Petroleum Engineering Laboratory Report.
http://www.cerlabs.com/experiments/1087540412X.pdf (accessed on 06/12/2012)
http://en.wikipedia.org/wiki/Wobbe_index (accessed on 06/12/2012)
http://www.sizes.com/units/wobbe_number.htm (accessed on 06/12/2012)
http://www.nationalgrid.com/uk/Gas/Data/help/opdata/index.htm (accessed on
06/12/2012)
http://www.globalenergy.co.uk/gaschange.htm (accessed on 06/12/2012)