ONSHORE GAS PROCESSING GAS PROCESSING …...This gas processing complex is typical of plants being...

1
9 8 7 6 5 4 1 3 2 1 Inlet receiver 2 Stabilizer tower 3 HP amine tower 4 Mole sieve dryers 5 Turboexpander 6 Demethanizer 7 De-ethanizer 8 Depropanizer 9 Debutanizer Legend ® OIL & GAS JOURNAL 1455 West Loop South, Suite 400 Houston, TX 77027 www.ogjonline.com Editorial direction and coordination from Warren R. True, Chief Technology Editor Cryogenic Natural Gas 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 ONSHORE GAS PROCESSING 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. 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 (H 2 S), carbon dioxide (CO 2 ), and mercaptans. 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 (C 5 +), and is sold as a product or blended with other products from the gas processing plant. GAS PROCESSING Amine treating 3 Following inlet separation and filtering, the mixed gas stream must be treated to remove any sour components before final processing and fractionation. This prevents H 2 S contamination of the products, and CO 2 freezing in downstream cryogenic NGL extraction during ethane (C 2 ) recovery. Mercaptans are removed to prevent contamination of liquid propane (C 3 ), butane (C 4 ), and liquid gasoline (C 5 +). 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. 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 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 control valve or a turboexpander. 5 The rotating turboexpander is often preferred because it provides improved gas cooling, product recovery efficiency, and recompression via an attached compressor. 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. 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. Slug catcher Stabilizer Stabilizer reboiler To condensate storage Inlet separator Inlet filter separator Sour gas Mercury removal Molecular sieve dehydration Amine treating Inlet pipeline Inlet gas Sweet gas Water Hot regeneration gas Residue-gas compressor after-cooler Residue gas compressor Cryogenic exchangers, separators Turboexpander Demethanizer Surge drum Residue gas to sales pipeline Depropanizer overhead condenser De-ethanizer overhead condenser De-ethanizer reflux accumulator De-ethanizer reboiler Depropanizer reboiler Ethane compression Depropanizer De-ethanizer Debutanizer overhead condenser Debutanizer reboiler Propane storage Butane storage Mixed butane to sales Stabilized condensate to sales Condensate storage tanks Condensate cooler Propane to sales Ethane product to sales pipeline Debutanizer Depropanizer reflux accumulator Debutanizer reflux accumulator Cyrogenic gas processing 4 5 6 5-6 9 8 7 1 2 3 Typical brazed aluminum exchange Exchanger separation vessel Brazed aluminum multipass exchanger 5 Turboexpander module Low-pressure residue gas Turboexpander, compressor unit High-pressure process gas Compressor residue gas Expander discharge LEVEL PRESSURE FLOW VALVES ANALYTICAL DCS SCADA Toll Free: +1–800–772–0878 www.rustco.com Proudly serving the Western United States since 1976 REPRESENTING: INTALOX ® ULTRA high performance random packing United States (316) 828-5110 | Canada (905) 852-3381 Italy +39 039 6386010 | Singapore +65-6831-6500 www.koch-glitsch.com 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. YOU CAN RELY ON US. www.MSAsafety.com ALTAIR® 2X Gas Detector ALTAIR® 4X Multigas Detector FlameGard® 5 MSIR ALTAIR® 2X Gas Detector ALTAIR® 4X Multigas Detector FlameGard® 5 MSIR 100 years of providing you with reliable, durable and innovative flame and gas detection. NGL Recovery Technology that is pre-engineered for faster time to market www.c-a-m.com/cryocam CRYOCAM GPA School of Gas Chromatography 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 GAS PROCESSING SOLUTIONS EPFC Capabilities for the Entire Natural Gas Value Chain GAS CONDITIONING AND TREATING MODULAR GAS PROCESSING PLANTS FRACTIONATION DEEP ETHANE EXTRACTION LPG RECOVERY LIQUID PRODUCT TREATING Call: + 1 713 375 8885 | Visit: www.CBI.com/gas-processing www.mchemical.com H Molecular Sieve H Purification Catalysts H LPG Odorants H Sulfur Recovery Catalyst

Transcript of ONSHORE GAS PROCESSING GAS PROCESSING …...This gas processing complex is typical of plants being...

Page 1: ONSHORE GAS PROCESSING GAS PROCESSING …...This gas processing complex is typical of plants being built to process production from major gas reserves in various regions of the US,

9

8

7

6

5

4

1

3

2

1 Inlet receiver

2 Stabilizer tower

3 HP amine tower

4 Mole sieve dryers

5 Turboexpander

6 Demethanizer

7 De-ethanizer

8 Depropanizer

9 Debutanizer

Legend

®

OIL & GAS JOURNAL1455 West Loop South, Suite 400

Houston, TX 77027 www.ogjonline.com

Editorial direction and coordination fromWarren R. True, Chief Technology Editor

Cryogenic Natural Gas 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

ONSHORE GAS PROCESSINGThis 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.

Inlet receiving 1The 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.

Liquid handling, stabilizing 2NGLs 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.

GAS PROCESSINGAmine treating 3

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.

Mole sieve dehydration 4Because 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 6The 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 control valve or a turboexpander. 5 The rotating turboexpander

is often preferred because it provides improved gas cooling, product recovery efficiency, and recompression via an attached compressor.

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.

NGL fractionationThe 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.

Slug catcher

Stabilizer

Stabilizerreboiler

To condensate storage

Inletseparator

Inlet filter separator

Sourgas

Mercuryremoval

Molecularsievedehydration

Aminetreating

Inlet pipeline Inlet gasSweet gas

Water

Hot regenerationgas

Residue-gas compressorafter-cooler

Residuegas compressor

Cryogenicexchangers,separators

Turboexpander

Demethanizer

Surge drum

Residue gas to sales pipeline

Depropanizeroverhead condenser

De-ethanizeroverhead

condenserDe-ethanizerrefluxaccumulator

De-ethanizerreboiler

Depropanizerreboiler

Ethane compression

DepropanizerDe-ethanizer

Debutanizer overheadcondenser

Debutanizerreboiler

Propane storage

Butane storageMixed butane to sales

Stabilized condensate to salesCondensate storage tanks

Condensate cooler

Propane to sales

Ethane product to sales pipeline

Debutanizer

Depropanizer refluxaccumulator

Debutanizer refluxaccumulator

Cyrogenic gas processing

4

5

6

5-6

9

87

1

2

3

Typical brazed aluminum exchange

Exchanger separation vessel

Brazed aluminum multipass exchanger

5 Turboexpander module

Low-pressure residue gas

Turboexpander, compressor unit

High-pressure process gas

Compressor residue gas

Expander discharge

LEVEL PRESSURE FLOW VALVES ANALYTICAL DCS SCADA

Toll Free: +1–800–772–0878www.rustco.com

Proudly serving the Western United States since 1976

REPRESENTING: INTALOX® ULTRA high performance random packing

United States (316) 828-5110 | Canada (905) 852-3381Italy +39 039 6386010 | Singapore +65-6831-6500

www.koch-glitsch.com

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.

YOU CAN RELY ON US.

www.MSAsafety.com

ALTAIR® 2X Gas Detector

ALTAIR® 4X Multigas Detector

FlameGard® 5 MSIR

ALTAIR® 2X Gas Detector

ALTAIR® 4X Multigas Detector

FlameGard® 5 MSIR

100 years of providing you with reliable, durable and innovative flame and gas detection.

NGL Recovery Technology that is pre-engineered for faster time to market

www.c-a-m.com/cryocam

CRYOCAM™

ENGINEERING | PROCUREMENT | FABRICATION | CONSTRUCTION

www.sconinc.com

GPA School of Gas ChromatographyA weeklong school that is 100 percent dedicated to gas chromatography, taught in classroom and hands-on lab sessions.Held annually in August at theUniversity of Tulsa, Oklahoma.

Class size limited; register early!

www.GPAglobal.org/education/gas-chromatography-school

GAS PROCESSING SOLUTIONS EPFC Capabilities for the Entire Natural Gas Value Chain

• GAS CONDITIONING AND TREATING• MODULAR GAS PROCESSING PLANTS• FRACTIONATION

• DEEP ETHANE EXTRACTION• LPG RECOVERY• LIQUID PRODUCT TREATING

Call: + 1 713 375 8885 | Visit: www.CBI.com/gas-processing

cbi_ogj_cryogenic_pstr_mar_2015.indd 1 3/11/2015 1:36:53 PM

www.mchemical.com

H Molecular SieveH Purification CatalystsH LPG Odorants H Sulfur Recovery Catalyst