Alternatives to Venting of Natural Gas ANG gas capture to reduce emissionsmembers.igu.org/old/IGU...

DNV GL © 2013 SAFER, SMARTER, GREENER DNV GL © 2013

Alternatives to Venting of Natural Gas –

ANG gas capture to reduce emissions

DNV GL © 2013

Categories of emission or venting

Natural gas emissions to the atmosphere result from several on-

shore gas industry processes and operations, but can be

categorised by four general types. These are:

− Fugitive emission (unplanned and uncontrolled)

− Process venting (planned, function of system operation)

− Venting from maintenance work (planned and controlled)

− Emergency vents (unplanned but controlled)

DNV GL © 2013

Natural Gas Venting Reduction

3

By design

Reduce Natural Gas Venting

By detection and repair

By reducing losses during operations

• Don’t vent gas in the first instance – design features and processes that prevent venting

• Ensure any new equipment installed does not vent gas

• Extend emission and leakage surveys • Take remedial actions to reduce leakage • Develop procedures to keep emissions low

through new systems and improved training/awareness

• Improve operational and/or maintenance practices and procedures

• Capture and re-use the vented gas (or flare it)

• Gas transfer by recompression

Approach

DNV GL © 2013

Key objectives of this study

To find technological solutions to reduce the gas vented volumes : – Prevent the methane emission in the first place (new processes,

technologies or equipment)

– Capture the methane emission (and then use the gas somewhere else or return it to the network)

– Flare the gas to convert it to CO2

Feasibility Study to evaluate options, develop solutions and focus on cost and environmental benefit view-point. Three aspects highlighted: – Recompression – gas transfer from an isolated section to a “live section”

– Capture the gas that would be vented (using specific technology eg. ANG) then re-use it

– Flare the gas rather than vent it.

Main project: Undertake a series of field trials of selected technologies to raise awareness and provide validation data

DNV GL © 2013

Concept of gas capture at a Compressor Station

P

Vent gas

compressor

control

Fuel gas

regulator

Process

compressor

Vent gas

compressor fuel

storage tank

Vent valve

(Normally closed)

Station Vent

Stack

Station Valves

(normally open)

Unit Valves

(normally closed)

Station

Inlet

Station

Outlet

Pressure

Measurement

Vent gas

compressor

Station emergency

shutdown protection

Method of re-compressing casing gas and valve leakage gas

Valve seal leakage

DNV GL © 2013

Introduction to ANG Technology

Adsorption of natural gas onto adsorbent at low or intermediate pressure ranging from

5 to 50 bar.

Adsorbent has a high porosity to achieve maximum storage capacity.

Greater energy density than Compressed Natural Gas (CNG) at same pressure.

LARGE/SMALL GAS MOLECULES

MICROPORE MACROPORE

ACTIVATED CARBON

ADSORBENT

Methane Adsorbed in Micropores

Gas Density in Free Space

Gas Density

in Carbon

Vessel without Carbon

Vessel with Carbon

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ANG Process Overview

Simplified process flow diagram for ANG

Compressor

PackageSolids

Filter

Guard Bed

Vessel

Heater

Package

To existing

venting system

Vented Gas Supply

50 – 2 barg

ANG Vessel

30 barg

Gas Discharged

to be reused

~ 1 barg

DNV GL © 2013


Charging Phase

Compressor

PackageSolids

Filter

Guard Bed

Vessel

Heater

Package

To existing

venting system

Vented Gas Supply

50 – 2 barg

ANG Vessel

30 barg

Gas Discharged

to be reused

~ 1 barg

DNV GL © 2013


Discharge Phase

Compressor

PackageSolids

Filter

Guard Bed

Vessel

Heater

Package

To existing

venting system

Vented Gas Supply

50 – 2 barg

ANG Vessel

30 barg

Gas Discharged

to be reused

~ 1 barg

DNV GL © 2013

Layout of Test Facility

To capture approximately 400 kg of natural gas.

Footprint of test rig is 14 m x 22 m = Area of 308 m2

Gas Receiver Vessel

ANG Storage Vessel

Compressor

Package

Heater Package

Guard Bed

Vessel

Natural

Gas Feed Pressure

Reduction

Flow Control and

Metering

GasPT1

GasPT2

Solids

Filter

1m (Dia) x 11m (L)

DNV GL © 2013

ANG Trial Objectives

To evaluate the performance and capabilities of the ANG storage technology and

carbon footprint.

– To replicate venting scenario at National Grid Compressor Site

– To evaluate and verify the capacity for the selected installation

– To optimise the control of gas quality

– To verify the carbon footprint reduction

– To determine the time taken to capture and store gas

– To demonstrate cyclic operation

DNV GL © 2013

ANG Vessel Design

Thermocouple Locations

ANG Vessel Layout

Existing 42 Inch Diameter Vessel

Metal Framework

V = 9.8 m3 Diameter = 1.1 m Length = 11.0 m

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GAS CAPTURE FIELD TRIAL RESULTS

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Adsorption Process

Adsorption phase Adsorbent bed heats up

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Storage & Delivered Capacity

The results show that at full scale and a pressure of 30 barg, ANG

provides a 70% increase in working capacity compared to CNG.

DNV GL © 2013

Carbon Footprint Reductions

Figure below shows the comparison of carbon footprint using different

technologies as an alternatives to venting.

VENTING,

100.0%

FLARING,

22.9%

ANG, 0.1%CNG, 0.7%

DNV GL © 2013

Achievements

“Full” scale demonstration of ANG technology.

The trial was successful and met all the objectives.

The trial and facility have been designed to mimic the expected venting

and capture process at a compressor site.

The system installation can capture close to 400 kg of natural gas and

showed the benefit of 70% storage enhancement compared to CNG.

For these scenarios, ANG technology gives the greatest carbon footprint

reduction compared to recompression and flaring.

During the discharge phase, the gas delivered meets the transmission

pipeline gas quality specification.

There is no evidence of carbon performance reduction from the cyclic

operations.

DNV GL © 2013

SAFER, SMARTER, GREENER

www.dnvgl.com

The DNV GL project team

Chiew Yen Law, You Van Lam, Robert Judd, Bill Walker,

Len Eastell and Martin Brown

Supported by Quentin Mabbutt and Tamsin Kashap from

National Grid

21

Martin Brown

[email protected]

(01509) 282468

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