Oil & Gas
Application Note
Inlet-Residue-NGL Solutions
for Natural Gas Processing Applications
To optimize the efficiency and profitability of your natural gas
processing plant you must account for the changing composition of
the inlet gas as well as adjust the natural gas liguid (NGL) extraction
efficiency to account for marketing conditions. The Inlet-ResidueNGL application for the Rosemount 770XA gas chromatograph
(GC) analyzes the inlet gas and the two product streams in a single
field-mounted analyzer to provide real-time feedback to the control
system and the operators. Using the live compositions from a single
gas chromatograph enables tight control of product specifications
thereby maximizing the economic return of the facility.
Figure 1 – The Typical Process Flow of a Natural Gas
Processing Facility Showing the Locations of the Sample
Points for the Gas Chromatograph
Residue
(Sales Gas)
Application Overview
Natural gas processing involves removing acid gases such as H2S
and CO2 and water from the raw inlet gas and then extracting the
condensates to produce natural gas, or residue or sales gases, and
natural gas liquid (NGL) products.
The composition of the inlet gas can vary significantly depending on
which well-heads are flowing, the ambient conditions on the primary
separators, and the operating state of the gathering network. The
composition of the sales gas is constrained by the contract tariffs
that typically limit the CO2 and nitrogen levels, the energy content,
and the hydrocarbon dew point. The NGL product will have virtually
zero CO2 and nitrogen, a small amount of methane, and varying
amounts of the heavier hydrocarbons.
To maximize the economic performance of your plant, you should be
able to quickly adjust to the market prices for the various products
that you extract. Typically, if the ethane price is high relative to
the natural gas price, the plant will run in ethane recovery mode to
produce as much ethane as possible from the NGL stream while
filtering out as much methane as possible. If the ethane price is
relatively low, the plant will run in “ethane rejection mode” and
will produce ethane rich natural gas close to the upper energy and
hydrocarbon dew-point pipeline tariffs. Historically, processing
plants would run for months at a time in a single mode. However,
due to the increasing variability in pricing and demand, plants that
can quickly switch between modes can capitalize on short term
fluctuations in the market and dramatically improve profitability.
Inlet
NGL
The Rosemount 770XA GPIRN Solution
Natural gas processing plants typically have one or two gas
chromatographs operating at their facility. We often find that on site
plant technicians and engineers do not have the time, training, or
expertise to properly operate these complex scientific instruments,
therefore increasing the risk of potential lost revenue opportunities
or costly shutdowns.
The Rosemount 770XA gas chromatograph configuration for
Inlet-Residue-NGL applications or GPIRN for short, is engineered
to eliminate complexity and designed to operate remotely and
unattended without compromising repeatability. The inlet and
residue streams are configured with a wide range of compositions,
and the NGL analysis accounts for a wide variation in ethane and
propane compositions found between the rejection and recovery
modes without the need of operator assistance.
See Table 1 for more details.
The Rosemount 770XA’s rugged hardware is designed to increase
analytical capability and widens the range of analysis options in a
field mounted GC with an ambient temperature rating of -4 to 140 °F
(-20° to 60 °C). Whether the analyzer is installed out in the field close
to the process or enclosed in a shelter, the 770XA is ideal for natural
gas processing applications that require advanced analysis such as
C9+ (with hydrocarbon dew point and cricondentherm calculations)
or C6+ with H2S.
Oil & Gas
Table 1 - Composition Ranges for the Rosemount 770XA
Inlet-Residue-NGL recommended application.
Inlet
Sales/Gas Residue
NGL Product
Nitrogen
0–10
0–10
–
Methane
75–100
75–100
0–5
Carbon Dioxide
0–10
0–10
0–1
Ethane
0–20
0–20
0–60
Propane
0–10
0–10
0–70
Isobutane
0–5
0–5
0–20
n-Butane
0–5
0–5
0–20
Isopentane
0–1
0–1
0–10
n-Pentane
0–1
0–1
0–10
Hexanes Plus (C6+)
0–0.7
0–0.7
0–10
Figure 2– A Rosemount 770XA Configured for the GPIRN
Application that is Suitable for Mounting in a Three-sided
Shelter, a GC Cabinet, or an Analyzer House.
System Design
The sample system design is critical to the performance of any
analyzer system and is an integral component of the Inlet-ResidueNGL application (see Table 1). Particulate filters, liquid filters,
check-valves, and bypass flow rotameters are provided for the two
vapor streams. Flow switches in the bypass flow can be included as
an option. To ensure there is no contamination between the inlet
gas and the residue gas sample streams, double-block-and-bleed
solenoids are used to select between the calibration and vapor
streams.
The liquid sample initially is conditioned through a liquid particulate
filter with fast bypass loop and armored rotameter mounted
externally to the main SHS enclosure. A very low volume side stream
is passed into the vaporizing regulator mounted inside the SHS
enclosure. The vaporized sample then passes through a manual ball
valve that allows for the manual calibration of the liquid analysis.
The vaporized liquid sample is injected into the GC oven through a
dedicated sample injection valve that is separate from the sample
injection valve used for the inlet and residue streams.
Both of the sample injection valves vent through dedicated
atmospheric referencing valves to enable the purging samples
to be routed to a safe sample vent (such as to the flare or vapor
recovery system) while enabling the sample loop to be referenced to
atmospheric pressure prior to injection into the analytical flow path
to ensure accurate and repeatable measurements.
All of the vapor state sample handling components are mounted
inside a stainless steel heated cabinet that can optionally include a
viewing window for easy system checks and can be incorporated into
the Rosemount 770XA gas chromatograph, or mounted remotely.
Page 2
Figure 3 – GPIRN Sample System
Oil & Gas
Rosemount 770XA Specifications and Drawings
Please consult Rosemount if your requirements are outside the specifications listed below. Improved performance, other products and
material offerings may be available depending on the application.
Construction
Environmental temperature: -20° to 60 °C (-4° to 140 °F)
Environmental temperature without safety certification:
40° to 60 °C (-40° to 140 °F)
Detector: Thermal conductivity detector (TCD), flame ionization detector (FID), TCD/TCD or TCD/FID dual detector configurations possible; flame photometric detector (FPD) available.
Enclosure Protection Rating: IP66
Gating Options: Fixed-time, slope sensing gating of peaks
• Dimensions (without sample system):
Streams: Up to 20 externally controlled streams or up to 8 internal
(includes calibration stream)
• Wall-mount: 711 mm H x 445 mm W x 498 mm D
Chromatograms stored/archived internally: Stores over 80 days of
analysis report data and up to 2500 individual chromatograms.
(28'' H x 17.5'' W x 19.6'' D)
• Pipe-mount: 711 mm H x 445 mm W x 671 mm D
ƒƒ Standard: 24 VDC (21–30 VDC)
(60.3'' H x 17.5'' W x 24.1'' D)
ƒƒ Optional: 90–264 VAC, 47–63 Hz
Corrosion Protection:
Typical Power Consumption at 22 °C (72 °F):
ƒƒ Startup: 105 Watts DC (125 Watts AC)
ƒƒ Steady State: 35 Watts DC (40 Watts AC)
• GC Enclosure Material: Copper free aluminum coated with industrial grade powder coat suitable for high humidity and salt-
laden environments.
Note: Add 15.5 Watts DC (18 Watts AC) for LOI
• Electronics: All electronic circuit boards are tropicalized with a clear conformal coating.
Communications (Standard)
• Process Wetted Materials: Stainless steel. Where the function of an item excludes the use of stainless steel (e.g. glass rotameter tubes), materials that are resistant to corrosion are used.
ƒƒ
ƒƒ
ƒƒ
ƒƒ
Mounting: Floor-standing (standard), wall- or pipe-mount (optional)
ƒƒ
Approximate Weight (without sample system): 50 kg (110 lbs.)
ƒƒ
Area Safety Certification Options:*
ƒƒ CSA:
–– USA and Canada
• Class I, Division 1, Groups B, C, and D
ƒƒ ATEX / IECEx
–– Ex II 2G
–– Ex d IIC Gb T6
(Ta = -20 °C to 60 °C)
Ethernet: Two ports – one RJ-45 and one four-wire with 10/100 mbps
Analog inputs: Two standard isolated inputs filtered with transient
protection, 4–20 mA (user scalable and assignable)
Analog outputs: Six isolated outputs, 4–20 mA
Digital inputs: Five inputs, user assignable, optically isolated, rated to 30 VDC @ 0.5 A
Digital outputs: Five user-assignable outputs, Form C and
electromechanically isolated, 24 VDC
Serial: Three termination blocks, configurable as RS-232, RS-422 or
RS-485 and one RS-232 D-sub (9-pin) Modbus/PC Connection
Communications (Optional)
Two expansion slots available for additional communications.
Each slot has the capacity to add one of the following:
ƒƒ
Four analog inputs (isolated) card
*Stated T-ratings can vary based on applications.
Performance Capabilities
ƒƒ
ƒƒ
ƒƒ
ƒƒ
ƒƒ
Four analog outputs (isolated) card
Eight digital inputs (isolated) card
Five digital outputs (isolated) card
One RS-232, RS-422 or RS-485 serial connection card
One modem card, 300-19.2k baud
Additionally, a FOUNDATION™ fieldbus module is available.
Memory Capacity: 1 GB of flash memory for data storage; 128 MB of SDRAM system memory with 2 MB static RAM (battery-backed)
Carrier Gas: Application-dependent. Typically zero-grade helium, nitrogen, or hydrogen
Carrier Gas Input Pressure Range (recommended):
6.2052–6.8947 bar (90–100 psig)
Power:
• Floor-mount: 1532 mm H x 445 mm W x 612 mm D
Sample & Calibration Gas Input Pressure Range:
0.2068–2.0684 bar: 1.0342 bar (recommended) or 15 psig
Electronics
(28'' H x 17.5'' W x 26.4'' D)
Oven: Airless, maximum 150 °C (302 °F)
Valves: Six-port and ten-port diaphragm chromatograph valves. Other types of valves, such as liquid injection or rotary valves, may be used depending on the application
Touch Key Local Operator Interface (Optional)
The Rosemount 770XA local operator interface (LOI) allows for maintenance
and operation of a 770XA without a laptop or PC. The LOI is a state-of-the-art
high resolution color display that is touch key infrared activated and supports
all core GC operations.
Page 3
Oil & Gas
Option Selection
Use the matrix below to choose the options for your application and build up the model string to order.
770XA GPSCS -
1
-
2
-
770XA
Rosemount 770XA Process Gas Chromatograph
Level 1
Hazardous Area Approval
Level 2
Level 3
Level 4
Level 5
A
ATEX/IEC-Ex
C
CSA rated
4
F
Floor-mount
P
Pipe-mount
W
Power
AC
Wall-mount
Universal 85 to 240 VAC
DC
24 VDC
Front Panel
EN
Extended switch panel - 18 streams switches and FID ignite
button (ignitor not used inless option XX-YY are chosen on
level 12)
SK
Local Operator Interface (LCD)
SN
Standard switch panel - eight stream switches - not available
when an FID option is selected on Level 12
Additional* I/O and Serial/Modem Communications - Slot A
5D
5M
5N
5P
5R
5S
5T
Additional I/O Port - Four Additional Channels of Analog Inputs
(Isolated)
Additional I/O Port - Eight Additional Channels of Digital Inputs
(Isolated)
Modem
None
Additional I/O Port - Four Additional Channels of Analog Outputs
(Isolated)
Additional Serial Port - (1) RS422 or 485 (Factory/Field
configurable)
Additional Serial Port - (1) RS232
Additional I/O Port - Five Additional Channels of Digital Outputs
(Isolated)
Additional* I/O and Serial/Modem Communications - Slot B
6A
Additional I/O Port - Four Additional Channels of Analog Inputs
(Isolated)
6D
Additional I/O Port - Eight Additional Channels of Digital Inputs
(Isolated)
6M
Modem
6N
None
6P
Additional I/O Port - Four Additional Channels of Analog Outputs
(Isolated)
6R
Additional Serial Port - (1) RS422 or 485 (Factory/Field
configurable)
6S
Additional Serial Port - (1) RS232
6T
Additional I/O Port - Five Additional Channels of Digital Outputs
(Isolated)
Level 7
FOUNDATION™ Fieldbus Interface
Level 8
Sample System Mounting Location
L
Local Sample System - Sample System mounted under GC, with
tubing and signaling connections by RAI
R
Remote Sample Handling System - Includes an external junction
box for SHS signal wiring, attached to the 700XA. Signal Wiring
and tubing connections are others.
Level 9
Gas Processing Application
1F
Page 4
-
5
GPSCS
Level 1
Mounting
5A
Level 6
3
-
Interface Module
GPIRN
Gas Processing - Inlet Residue NGL (three streams)
GPDET
GPEPS
DeEthanizer Tower Overheads and Bottoms (two streams)
Ethane Purity
GPPPS
Propane Purity
GPPPX
Propane Purity Extended (with Propylene)
Level 2
Level 3
Level 4
Level 5
Level 6
Level 7
Level 8
-
6
-
7
-
8
- GPIRN
- GPIRN
9
Sample Conditioning System for Rosemount 770XA
- Gas Processing Applications
Gas Processing Application SHS type
GPIRN
Inlet/Residue/NGL
GPDET DeEthanizer Tower
GPEPS
Ethan Purity
GPPPS
Propane Purity
GPPPX
Propane Purity Extended (with Propylene)
Hazardous Area
A
Local Sample System
C
CSA rated components - Class I, Division 1, Groups B, C, D
Mounting
LS1
Local Sample System - Sample System mounted under GC, with
tubing and signaling connections by Rosemount
RS1
Remote Sample Handling Sysem - Includes external junction
box, with signal wiring and tubing connection by others.
Power
A1
110 VAC
A2
220 VAC
Window
PL
Plexiglass - Lexan
Vapor Flow Switches
V1
Single Vapor Flow Switch
V2
Two Vapor Flow Switches
V3
Three Vapor Flow Switches
V4
Four Vapor Flow Switches
Vapor Sample Entry
H1
Single Vapor Heat Trace Boot
H2
Two Vapor Heat Trace Boots
H3
Three Vapor Heat Boots
H4
Four Vapor Heat Trace Boots
B
⅛ Bulkhead Fittings
Liquid Flow Switches
L1
Single Liquid Flow Switch
L2
Two Liquid Flow Switch
L3
Three Liquid Flow Switches
L4
Four Liquid Flow Switches
(*) Standard Communications - 5 Di/ 5 DO/2 AI/ 6 AO (All Isolated and (3) RS422, RS422 or RS485 (Factory/Field configurable) serial ports.
Optional Accessories
Vapor Sample Probe
Vapor Sample
Probe/Regulator
Vaporizing Regulator
Heating Sample Probe
Liquid Sample Probe
Heat Traced
Sample Line
Provide line size, process connection details, process
pressure and temperature.
Provide line size, process connection details, process
pressure and temperature.
For remote mount at the sample point
For vapor samples. To be mounted at the sample point.
Provide line size and process connection details.
⅛th Stainless steel heat traced sample tubing including
termination kit. Specify length required.
Oil & Gas
Recommended Installation
The drawings below represent the minimum recommended installation guidelines for the Rosemount 770XA Natural Gas Chromatograph.
Please consult Rosemount for detailed installation recommendations for your application.
Figure 4 – GPIRN OD Local
Figure 5 – GPIRN OD Remote
Page 5
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