Proudly serving the Western United States since 1976
FlameGard® 5 MSIR
INTALOX® ULTRA
GAS PROCESSING SOLUTIONS
REPRESENTING:
EPFC Capabilities for the Entire Natural Gas Value Chain
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Toll Free: +1–800–772–0878
www.rustco.com
LEVEL
PRESSURE
FLOW
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ANALYTICAL
DCS
GAS CONDITIONING AND TREATING
MODULAR GAS PROCESSING PLANTS
FRACTIONATION
high performance
random packing
CRYOCAM™
DEEP ETHANE EXTRACTION
LPG RECOVERY
LIQUID PRODUCT TREATING
NGL Recovery Technology
that is pre-engineered for
faster time to market
United States (316) 828-5110 | Canada (905) 852-3381
Italy +39 039 6386010 | Singapore +65-6831-6500
www.koch-glitsch.com
cbi_ogj_cryogenic_pstr_mar_2015.indd 1
ALTAIR® 2X
Gas Detector
100 years of providing you with reliable, durable
and innovative flame and gas detection.
YOU CAN RELY ON US.
For related trademark information, visit http://www.koch-glitsch.com/ourcompany/pages/trademarks.aspx.
This technology is protected by one or more patents in the USA. Other foreign patents may be relevant.
www.c-a-m.com/cryocam
Visit: www.CBI.com/gas-processing
Call: + 1 713 375 8885 |
SCADA
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ALTAIR® 4X
Multigas Detector
www.MSAsafety.com
3/11/2015 1:36:53 PM
Cyrogenic gas processing
Sweet gas
Inlet pipeline
Inlet gas
®
OIL & GAS JOURNAL
1455 West Loop South, Suite 400
Houston, TX 77027
www.ogjonline.com
ONSHORE GAS PROCESSING
GAS PROCESSING
Amine treating 3
This gas processing complex is typical of plants being built to process production
from major gas reserves in various regions of the US, especially shale gas regions.
Natural gas liquids (NGLs) produced from such a plant may include ethane, propane,
normal and isobutanes, and condensate. The gas remaining after processing (residue
gas) moves via a separate pipeline for further processing, as necessary, or to end-use
markets.
Cryogenic
Natural Gas Plant
Following inlet separation and filtering, the mixed gas stream must be treated to
remove any sour components before final processing and fractionation. This prevents
H2S contamination of the products, and CO2 freezing in downstream cryogenic NGL
extraction during ethane (C2) recovery.
Mercaptans are removed to prevent contamination of liquid propane (C3), butane
(C4), and liquid gasoline (C5+).
Sour gas enters an amine contactor tower, flowing upward through trays while lean
amine flows downward. The lean amine reacts with the sour components in the gas,
removing them from the gas stream.
The gas is now “sweet” and the amine liquid is rich. Sweet inlet gas, now saturated
with water, leaves the top of the amine contactor. It then passes through the sweet gas
scrubber to catch any condensed or carryover amine and water from the contactor.
The sweet gas then moves to the inlet coalescing filter upstream of a molecular sieve
dehydration unit.
Rich amine leaves the bottom of the amine contactor and enters an amine
regenerator. This unit heats the rich amine, boiling it at low pressure to drive off the
sour components and regenerates the lean amine for re-use in the amine contactor.
The low pressure sulfur-rich vapor is sent to a sulfur unit for conversion to elemental
sulfur. Sour overhead vapor can also be disposed of by thermal oxidation.
Inlet receiving 1
The gas processing plant’s inlet receiving consists of a slug catcher and an inlet
receiver vessel. The slug catcher employs gravity to separate hydrocarbon liquids
that accumulate in the gathering pipeline from the producing field. The receiver
vessel receives the vapor and the vapor-liquid overhead from the stabilizer units
compression, ensuring that only vapor enters the gas processing unit.
The separated vapor flows to a filter-separator to remove remaining liquids or
particulates from the gas stream before flowing to a high-pressure amine contactor
to remove such acid-gas contaminants as hydrogen sulfide (H2S), carbon dioxide
(CO2), and mercaptans.
Editorial direction and coordination from
Warren R. True, Chief Technology Editor
Liquid handling, stabilizing 2
NGLs from the slug catcher and various other process units flow to the stabilizing
unit where they are blended, filtered, and heated. The heated liquids then enter a
stabilizer feed separator, which separates flashed vapor from residual water and NGLs
before the NGLs flow to the stabilizer tower for stabilizing. Distillation separates the
lighter, more volatile hydrocarbons and returns them to the gas processing system.
The overhead product of the stabilizer tower is a natural gas stream rich in propanes
and butanes, which is then compressed and moves to the inlet receiver to enter the
gas processing portion of the plant.
The stabilizer tower's bottom product is stabilized condensate or natural gasoline,
primarily pentanes and heavier (C5+), and is sold as a product or blended with other
products from the gas processing plant.
Content by the Wood Group Mustang team:
Randy Sharp, Naga Jonnalagedda, Marty Ogg, and David Harsh
Artwork & rendering: Tim Mayo, Industrial 3D – A Check6 company
Graphic coordination: Chris Jones, Xenon Group | xenongroupdesign.com
Mole sieve dehydration 4
Because the downstream NGL recovery section operates at cryogenic temperatures
(colder than −150° F. or −100° C.), removing water is necessary to prevent equipment
from freezing. Molecular sieve dehydration achieves the proper level of dryness.
After leaving the sweet gas scrubber, treated gas enters a coalescing filter, which
removes any residual particles of entrained hydrocarbon liquid, free water, and amine
liquid that would contaminate the mole sieve beds.
The gas enters the mercury guard bed, a vertical vessel filled with a sacrificial
mercury adsorbent, which removes mercury to prevent damage to aluminum
exchangers further downstream. After the mercury guard bed, the gas enters the
mole sieve dryers, which are vertical vessels containing beds of solid granular
molecular sieve desiccant and bed support materials.
These beds remove virtually all the water remaining in the inlet gas to an outlet
water content of less than 0.02 ppm (wt). The mole sieve dryers operate in rotation,
sequentially absorbing water or being thermally regenerated with hot gas.
The dehydrated gas leaves the bottom of mole sieve dryers and is then filtered
to remove dust that could damage or foul downstream equipment in the NGL
extraction unit. The filters are rated a nominal 0.5µ. After filtering, about 10% of
the total gas flows to the regeneration compressors, which is then heated and
used to regenerate the molecular sieve beds to a dry state. The remaining dry gas
stream flows to the inlet of the NGL extraction unit.
Cryogenic NGL extraction 5 6
Following expansion, the cold gas and refrigerated liquids enter the
demethanizer tower. 6 Cold methane-rich residue gas leaves the overhead
while ethane and heavier hydrocarbons leave the tower bottom as a liquid.
The cold residue gas is cross exchanged in the brazed aluminum feed
exchangers to cool incoming gas and then recompressed before entering the
residue-gas pipeline for sale or further processing.
Demethanizer
3
Sour
gas
1
Amine
treating
Inlet
separator
Slug catcher
5
Turboexpander
Mercury
removal
Inlet filter separator
4
Stabilizer
NGL fractionation
The liquid stream from the bottom of the demethanizer tower contains
ethane, propane, butanes, and pentane and heavier hydrocarbons. These are
separated by sequential fractionation.
Ethane is recovered in the overhead of the de-ethanizer column 7 as a
vapor product then typically compressed and sold into a pipeline. If ethane
recovery is not required or desired, the demethanizer can be designed to
“reject” ethane, leaving it in the residue gas.
The deethanizer bottom liquids contain propane and heavier hydrocarbons.
The propane is recovered in the depropanizer 8 as an overhead liquid and
sold as an LPG product. Mixed butanes are recovered in the debutanizer
tower 9 overhead as liquid and sold as a product or further processed to
split the normal butane and isobutane.
The debutanizer bottom liquid is a natural gasoline product similar to the
stabilizer bottom product and can often be blended and sold.
The purpose of cryogenic extraction is to cool, condense, and absorb into a liquid
all hydrocarbon components in the plant’s inlet gas heavier than methane, so that
these components can be separated and sold as individual products. Performing this
separation greatly increases the value of the products, compared with leaving them
in the gas stream.
There are many variations of cryogenic gas separation processes, but all function
by progressively cooling the gas by applying cooling by refrigeration, separation, and
mechanical gas expansion. Propane and propylene are commonly used refrigerants.
Mechanical expansion can be
provided by a high pressure-drop
5 Turboexpander module
control valve or a turboexpander.
5 The rotating turboexpander
is often preferred because it
provides improved gas cooling,
Turboexpander, compressor unit
product recovery efficiency, and
recompression via an attached
compressor.
Compressor residue gas
Water
Hot regeneration
gas
Molecular
sieve
dehydration
Cryogenic
exchangers,
separators
6
Surge drum
2
Stabilizer
reboiler
Residue-gas compressor
after-cooler
To condensate storage
Residue gas to sales pipeline
Residue
gas compressor
7
De-ethanizer
De-ethanizer
overhead
condenser
Depropanizer
overhead condenser
De-ethanizer
reflux
accumulator
Depropanizer
8
Debutanizer overhead
condenser
Depropanizer reflux
accumulator
Debutanizer reflux
accumulator
Debutanizer
9
Butane storage
Mixed butane to sales
Expander discharge
De-ethanizer
reboiler
Depropanizer
reboiler
Debutanizer
reboiler
Condensate storage tanks
Condensate cooler
Propane storage
Ethane compression
Legend
1 Inlet receiver
5-6 Typical brazed aluminum exchange
Low-pressure residue gas
Brazed aluminum
multipass exchanger
3 HP amine tower
4 Mole sieve dryers
5 Turboexpander
6 Demethanizer
7 De-ethanizer
8 Depropanizer
9 Debutanizer
7
9
2
Exchanger separation vessel
3
8
6
4
1
5
ENGINEERING
|
PROCUREMENT
|
FABRICATION
|
CONSTRUCTION
GPA School of Gas Chromatography
H Molecular Sieve
H Purification Catalysts
H LPG Odorants
H Sulfur Recovery Catalyst
www.sconinc.com
www.mchemical.com
A weeklong school that is 100 percent
dedicated to gas chromatography, taught in
classroom and hands-on lab sessions.
Held annually in August at the
University of Tulsa, Oklahoma.
Class size limited; register early!
www.GPAglobal.org/education/gas-chromatography-school
Propane to sales
Ethane product to sales pipeline
High-pressure process gas
2 Stabilizer tower
Stabilized condensate to sales