DNV GL 21 June 2015 SAFER, SMARTER, GREENERDNV GL

21 July 2015Diane Broomhall

OIL & GAS

Analytical challenges faced by UK gas network operators accepting biomethane into the UK gas grid

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1st Chemistry in Energy Conference

July 2015, Edinburgh

DNV GL 21 June 2015

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DNV GL 21 June 2015

Energy Measurement and Compliance

Provide key technical advice to gas distribution and transmission companies:

Interchangeability of unconventional gases with natural gas:

Impact of gas components on gas networks and gas appliances

Combustion analysis

Evaluation of third party analytical equipment and practices

Energy measurement and accounting

Transportation of H2 in the gas network

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Biomethane and the UK gas network

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EU Directive 2003/55/EC:The complete opening of national gas markets to competition

Lays down the right of third parties to non-discriminatory access to gas transmission and distribution systems.

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EU Directive 2003/55/EC:The complete opening of national gas markets to competition

Lays down the right of third parties to non-discriminatory access to gas transmission and distribution systems.

Provides the framework for admission of biogas or gas from biomass to the gas network for environmental reasons provided that the gas is permanently compatible with the relevant technical rules and safety standards.

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DNV GL 21 June 2015

EU Directive 2003/55/EC:The complete opening of national gas markets to competition

Lays down the right of third parties to non-discriminatory access to gas transmission and distribution systems.

Provides the framework for admission of biogas or gas from biomass to the gas network for environmental reasons provided that the gas is permanently compatible with the relevant technical rules and safety standards.

These rules and standards should ensure that these gases can technically and safely be delivered into, and transported, through the natural gas system and should also address the chemical characteristics of these gases

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UK Gas Safety (Management) Regulations 1996

Property Range or limit

Hydrogen sulphide (H2S) < 5 mg m-3

Total sulphur < 50 mg m-3

Hydrogen (H2) < 0.1 mol %

Oxygen (O2)< 0.2 mol %< 1.0 mol % for biomethane

Water dewpointHydrocarbon dewpointImpurities

The gas shall not contain solids or liquids that may interfere with the integrity or operation of the network or appliances

Wobbe Number 47.20 and 51.41 MJ m-3

ICF (Incomplete Combustion Factor) < 0.48

SI (Sooting Index) < 0.60

OdourGas below 7 barg will have a stenching agent added to give a distinctive odour

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DNV GL 21 June 2015

UK Gas Safety (Management) Regulations 1996

Property Range or limit

Hydrogen sulphide (H2S) < 5 mg m-3

Total sulphur < 50 mg m-3

Hydrogen (H2) < 0.1 mol %

Oxygen (O2)< 0.2 mol %< 1.0 mol % for biomethane

Water dewpointHydrocarbon dewpointImpurities

The gas shall not contain solids or liquids that may interfere with the integrity or operation of the network or appliances

Wobbe Number 47.20 and 51.41 MJ m-3

ICF (Incomplete Combustion Factor) < 0.48

SI (Sooting Index) < 0.60

OdourGas below 7 barg will have a stenching agent added to give a distinctive odour

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Differences in composition:UK natural gas and raw biogas

Component Conc. in grid natural gas

Conc. in raw biogas

CH4 81 - 97% 40 80%

C2 0.007 - 10.2% 0

C3 to C5 hydrocarbons 0.1 5.7% 0 - 0.001% (10ppm)

C6+ hydrocarbons 0 0.15%(mainly alkanes)

0 0.03%(mainly aromatics)

CO2 0 4% 15 55%

O2 0.001% (10ppm) 0 6%

N2 0.005 7.7% 0 20%

H2 0.01 0.02% 0 4%

Water Dewpoint < -10C@ network pressure

Saturated@ ambient pressure

H2S 0 5mgm-3 0 45600 mgm-3

Other trace contaminants Drying agents and gas liquids By-products of digestion plus all sorts of man-made waste!

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Trace contaminants found in biogas

Trace contaminant SourceWater AD plant

Siloxanes Cosmetic products Food wasteTerpenes Essential Oils (natural and man-made)Ammonia Products of Digestion processAldehydes and ketones Products of Digestion processPesticides & pharmaceuticals FeedstockMetals (Hg, As, Ca, Si) Waste water treatment plantMicro-organisms DigesterDust Upgrading process beds

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Potential safety consequences of non-compliant gas

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Component Safety ConsequencesCorrosion Combustion Leakage detection by

public(impact on odour)

Steel

(gas network)

Copper

(domestic)Safety Control of industrial processes

High Inerts (CO2, N2) High CO2 + H2O High N2 High N2

H2S If H2O present

Total sulphur

O2Depends of partial pressure of O2 and presence of

H2O

Moisture

Siloxanes

Organic halides

Micro-organisms If H2O present

Terpenes

Aldehydes & ketones

Ammonia

Volatile metals (Hg, As) Liquid Hg

Pesticides & Pharmaceuticals

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Volatile Organic Compounds in Biogas

VOC type Example compounds Limits for natural gas distribution grid

Alkanes (includingcyclo-alkanes) propane, cyclohexane Total concentration limited by hydrocarbon dewpoint.

EA QP limit for xylene is 100 mg m-3Aromatic hydrocarbons

benzene, toluene, xylene

Siloxanes hexamethyldisiloxane Limits for gas grids still to be decided. Likely to be between 5 mg m-3 and 0.05 mg m-3

Terpenes limonene, pinene Limits on individual compounds will depend on their

impact on the smell of distributed gas.Carbonyls formaldehyde, acetone

Organo halides carbon tetrachloride, Freons Limit for Total Organo Halides is 1.5 mg m-3

Organic sulphides dimethyl sulphide Total Sulphur limit includes H2S. Total Sulphur limit for natural gas is 50 mg m-3.

EA QP limit is 30 mg m-3.Mercaptansmethyl mercaptanethyl mercaptan

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Risk Assessment for New Gas Connections

All UK licensed Gas Transporters have an obligation to ensure:

all new gas connections comply with all statutory legislation with regard to gas quality, calorific value and flow measurement

The safety and integrity of the gas network is not compromised

The new gas will not affect the operation of gas customers appliances

Will not impact on the health of the general public either directly or indirectly via gas combustion products

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Risk Assessment Output:Sampling and Analysis Protocol - Criteria

Feedstock and Digestion Process Crop silage, food waste, animal waste, sewage sludge Consistent feedstock mix or feedstock changes Continuous digestion or batch process

Upgrading process H2S suppression Specialist adsorption e.g. siloxanes, terpenes Main upgrading process:

Membrane separation Water wash Cryogenic Pressure/Temperature Swing Adsorption

Retro-fit upgrading equipment

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Risk Assessment Output:Measurement Provisions for Network Entry Point

Gas sampling and analysis provide evidence to the HSE that every best endeavour has been made to protect the gas network and customers:

For on-line measurement of gas components: Correct analyser No interference from other components Appropriate analytical range for network limit Evaluate performance before ROV opens Calibrate regularly or continually monitor performance

Sampling and Analysis Protocol for other gas components of interest: Demonstrate steady state gas process before ROV opens Initial sampling interval for each component determined by Risk Rating Sampling interval can be reduced if evidence allows

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Risk Assessment Output:Biomethane components measured on-line

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Component Measurement techniqueAll components required by Ofgem to calculated CV: CH4, C2H6, C3H8, C4H10, C5H12, C6+

CO2, N2

Ofgem approved instrument: Gas chromatograph Inferential device

Hydrogen sulphide Gas chromatograph Electrochemical cell

Oxygen Gas chromatograph Electrochemical cell

Hydrogen Gas chromatograph

Water dewpoint Moisture sensor

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Analytical techniques for critical trace biogas components

Biogas trace componentsSiloxanesTerpenesAmmoniaAldehydes and ketonesPesticides & pharmaceuticalsMetals (Hg, As, Ca, Si)Micro-organismsDust

There are no inexpensive reliable continuous on-line analysers for most trace biogas contaminants

At present, they require specialised sampling and complex laboratory methods.

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