This document discusses analyzing the composition and BTU content of natural gas from fracking operations using gas chromatography. It describes how both flame ionization detectors (FID) and thermal conductivity detectors (TCD) are needed to measure the concentrations of hydrocarbon components and inert gases to determine the total BTU value. The analysis can be performed using a gas chromatograph equipped with dual FID/TCD detectors, packed and capillary columns, and temperature programming to separate methane, ethane, and heavier hydrocarbons up to C6 in about 12 minutes to allow calculation of the natural gas heating content.

1. Analysis of Natural Gas Composition
and BTU Content from Fracking
Operations
Dr. John N. Driscoll & Jennifer Maclachlan
PID Analyzers, LLC
Cape Cod, MA
Pittcon Symposium: Advances in Energy Research: From
Unconventional Fuels to Solar Energy
March 10, 2015
PM Session 3:05
Paper 1370-5
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2. Introduction
• Natural gas is bought or sold based on the quantity of energy delivered.
The product of the concentration (determined by gas chromatography)
and the heating value (BTU) determines the BTU content of the fuel.
Although the natural gas from Marcellus shale is primarily methane, the
composition can vary considerably from region to region
• Shale gas streams can vary in composition from primarily CH4 to one that
can contain heavier hydrocarbons (to C6+) species. The work for this paper
was completed with our Model 301C gas chromatograph based natural gas
analyzer is configured with dual detectors (FID & TCD), packed and
capillary column capability and temperature programming. It has an
embedded PC and Windows 7.0 operating system with PeakWorks™
chromatography control software. It is a compact industrial gas
chromatograph in a 19” rack mount or wall mount enclosure. Outputs
include RS485, and 4-20 mA. It can be connected to the internet and can
be controlled remotely.
Advances in Energy Research: From Unconventional Fuels to Solar Energy 2

3. What GC Detectors are needed for BTU
determinations?
• The most popular detector for hydrocarbons is
the flame ionization (FID) detector. This detector
is specific for hydrocarbons, has a wide dynamic
range (>106) and sub ppm detection limits. The
disadvantages include the requirement for H2 and
zero air as well as the 30-45 warmup time.
• The Thermal Conductivity detector(TCD) has a
range from 100% to a few hundred ppm. The TCD
has a universal response to fixed gases, and all
inorganic and organic gases.
3Advances in Energy Research: From Unconventional Fuels to Solar Energy

4. Flame Ionization Detector
FID Schematic Description FID
An FID consists of a combustion
source (a flame), an ion
chamber, an igniter, a voltage
source for the accelerating
electrode, and an
electrometer/amplifier
As illustrated here, the flame
acts as the accelerating
electrode or the bias electrode
4Advances in Energy Research: From Unconventional Fuels to Solar Energy

5. FID Mechanism
• Flame ionization is the process of ionization
that occurs in organic compounds when the
carbon–carbon bond is broken via a thermal
process (in the flame) that results in the
formation of carbon ions. These ions are
collected in the flame by applying a positive
potential to the FID jet and the ions are
pushed to the collection electrode where the
current is measured. The response (current) is
directly proportional to the concentration.
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6. Thermal Conductivity Detector
Description of TCD
• Measures the difference in
thermal conductivity
between reference and
sample stream
• Uses a Wheatstone Bridge
which is shown here
• Universal response
• Linear range > 104
• Detection limit 100-200ppm
• Maximum value 100%
TCD Schematic
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7. GC Instrumentation
Photo of GC 301C
PeakWorks™ Software with
Windows 7 OS
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The 301C GC has an 8” touch screen
which displays all the chromatographic
conditions and integration information

8. GC301 Fluidics
301 Gas Controls TCD/FID
2 point Natural Gas System Gases-
Photo of inputs and outputs
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9. Other Components of Natural Gas
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All these
compounds can
be separated on
a packed mole
sieve column:
The advantage of
the TCD is there
might be other
combustible
gases in the
sample and these
can be used to
bring up the BTU
value of the gas

10. Inert Components & CO
• There are a number of BTU & inert
components in natural gas which can be
detected by a Thermal conductivity Detector
(TCD):
– Inert components: N2, trace O2, CO2
– Combustible components not detected by the FID:
CO & H2
– These can be separated on a packed molecular
sieve column
10Advances in Energy Research: From Unconventional Fuels to Solar Energy

11. Columns for HC Separation of C1 to C6 HCs
• Methane can be separated from ethane and
ethylene easily on a 1 M packed column like
HayeSep N as seen in the next slide. The
problem is that to get the higher C3+
hydrocarbons off the column, temperature
programming up to 200 degrees C is needed.
This increases the analysis time considerably
because the column then has to cool down to
40-50 degrees C to complete the separation.
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12. C1-C2 HC Packed Column- FID
12
This is a typical
chromatogram
of methane,
ethane,
ethylene and
acetylene on a
HayeSep N
column
Advances in Energy Research: From Unconventional Fuels to Solar Energy

13. Capillary Column Analysis of C1& C2’s
• We chose to use a thick film (5 micron methyl
silicone film capillary column). We chose this
column because it separates by boiling point of
the hydrocarbons. The issue here is that
methane(BP -161C) , ethane and ethylene are
gases while all other boiling points for
hydrocarbons are considerably higher and methyl
silicone phase separates by boiling point. The
boiling point of propane is -42C. The difficult
part of the analysis is the separation of C1 and C2
hydrocarbons. The next slide demonstrates that
the C1 & C2’s are separated.
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14. C1 to C3 HC GC-Capillary Column
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We’re achieving
pretty good
separation here:
Ethane & Ethylene
is 50%, Methane
is baseline and
this is separated
from the
propylene and
propane.

15. C1 to C6 separation
• With the same column and with temperature
programming from 40-70oC, we can separate
all of the HC except propene and propane in
12 minutes. The higher hydrocarbons are
important because of the higher BTU values
compared to methane.
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16. C1 to C6 HC GC-Capillary: Alkanes &
Alkenes
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The
alkenes
come out
before the
alkanes

17. Natural Gas
• The major component of natural gas is
methane. The content can vary from 87-97%.
The next highest component is ethane or
ethylene and the other higher hydrocarbons
are in the 1% or lower concentration. The BTU
values for higher molecular weight
hydrocarbons are larger because they have
more carbon and hydrogen atoms to burn and
generate heat.
17Advances in Energy Research: From Unconventional Fuels to Solar Energy

18. Typical Natural Gas Composition
Component
Typical Analysis Range
(mole %) (mole %)
Methane 95.0 87.0 - 97.0
Ethane 3.2 1.5 - 7.0
Propane 0.2 0.1 - 1.5
iso - Butane 0.03 0.01 - 0.3
normal - Butane 0.03 0.01 - 0.3
iso - Pentane 0.01 trace - 0.04
normal - Pentane 0.01 trace - 0.04
Hexanes plus 0.01 trace - 0.06
Nitrogen 1.0 0.2 - 5.5
Carbon Dioxide 0.5 0.1 - 1.0
Oxygen 0.02 0.01 - 0.1
Hydrogen trace trace - 0.02
Gross Heating Value (MJ/m3
),
dry basis *
38 36.0 - 40.2
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19. BTU Values of
Hydrocarbons-
This is why people are
interested in measuring
these -Note the net
heating values-these
can really add up and
increase the value
Gas Gross Heating Value
(Btu/Scf)
Net Heating Value
(Btu/Scf)
Methane 1012 911
Ethane 1783 1631
Propane 2557 2353
isobutane 3354 3094
n-butane 3369 3101
isopentane 4001 3698
n-pentane 4009 3709
Neopentane 3987 3685
n-hexane 4755.9 4403.8
2-Methylpentane 4747.3 4395.2
3-Methylpentane 4750.3 4398.2
2,3-Dimethylbutane 4745 4392.9
n-heptane 5502.5 5100
2-Methylhexane 5494.6 5092.2
3-Methylhexane 5498.6 5096
2,2-Dimethylpentane 5481.9 5079.6
3,3-Dimethylpentane 5488.8 5086.4
Ethene (Ethylene) 1599.8 1499.1
Propene (Propylene) 2332.7 2181.8
1-Butene (Butylene) 3079.9 2878.7
cis-2-Butene 3072.2 2871
trans-2-butene 3068 2866.8
1-pentene 3826.5 3575
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20. Natural Gas Sample
This is a sample
of natural gas
from Cape Cod
using the same
30M column and
conditions as
slide # 16. Just C1
to C4 in this
particular
sample.
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21. Natural Gas Analysis
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We could run a TCD analysis here to
see if there is any hydrogen or CO to
burn so we can increase the value

22. Heating Content of Natural Gas
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23. Natural Gas HC + Inert Compounds: FID TCD
Configuration
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The configuration for FID/TCD is
shown here with dual columns run
in parallel. One is packed and the
other is a 30M capillary column.
Advances in Energy Research: From Unconventional Fuels to Solar Energy

24. Natural Gas Compressor Measurements
Compressors
• Natural Gas Compressors are
used to increase the pressure on
a fluid and transport the fluid
through a pipe to the next
compressor. EPA requires the
exhaust from these compressors
to be monitored. The 301C
natural gas analyzer can also
monitor the exhaust gas for non
methane hydrocarbons via EPA
method 18 which reports C1 to C6
hydrocarbons less methane &
ethane, which are not considered
photochemically active
Natural Gas Compressor Station
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25. An Example of Natural Gas Compressor Exhaust
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These are the same conditions and column that we use for the natural
gas analysis-We don’t see methane in this sample.

26. Conclusions
• Natural gas analysis & BTU content can be done using a
GC equipped with both flame ionization and thermal
conductivity detectors. Any conversion factors can be
entered into the final analysis by the customer.
• The typical analysis time for C1-C6 analysis is 12
minutes.
• The analyzer can also be used to check the emissions
from natural gas compressors via EPA Method 18.
• Want to learn more? Come by our booth in the Pittcon
expo, #1326.
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27. Connect with us on Linked-In
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@pidguy
@pidgirl
www.facebook.com/pidanalyzers
www.twitter.com/pidguy
www.twitter.com/pidgirl
www.analyzersource.blogspot.com
Advances in Energy Research: From Unconventional Fuels to Solar Energy