BIOGAS CLEANING AND

BIOMETHANE UPGRADING

TECHNOLOGY

DAY TWO, 4TH JULY

13.00 – 14.00

@adbiogas #UKADBiogas

DIANE BROOMHALL TECHNICAL CONSULTANT

GL NOBLE DENTON

Selecting the correct gas quality measuring equipment UK AD & Biogas July 2013

GL Noble Denton

GL Noble Denton are independent advisors providing consulting, design, assurance

and project execution services, combining excellent engineering and analytical skills

with operational experience of offshore, maritime and onshore oil and gas assets.

GL Noble Denton:

Gas Quality and Interchangeability

GL Noble Denton's consultancy services for biogas connections to grid include:

• risk assessments for new gas connections

• review network operations, ensuring network integrity

• measurement of gas properties to meet safety and contractual obligations

• consistent, accurate and Ofgem compliant energy accounting

• combustion analysis

• rhinology practices

• recommend, specify and evaluate monitoring instrumentation

• supply of DANINT Ofgem compliant software

Training courses on:

• variations in natural gas from different international sources

• Flow Weighted Average CV and Ofgem compliance

Licensed UK Gas Transporter’s Safety Case to the HSE

In order to obtain a Gas Transporter’s license, Gas Transporter’s must submit a

Safety Case to the UK HSE

The Safety Case describes what Policies and Procedures are in place to ensure the

safe transportation of gas and compliance with gas safety legislation – Gas Safety

(Management) Regulations and Gas (Calculation of Thermal Energy) Regulations

One such Procedure is a Risk Assessment for all new gas connections

Risk Assessment for New Gas Connections

The Risk Assessment will ensure that:

• the new gas connection complies 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

• the new gas will not impact on the health of the general public either directly or

indirectly via gas combustion products

The Risk Assessment will determine:

• which gas components must be monitored on-line

• which gas components can be monitored by a program of spot-sampling and

analysis

Once the Risk Assessment is completed and agreed by both gas producer and gas

transporter a contractual Network Entry Agreement can be produced.

Gas Distribution Network Entry Agreement:

Gas Composition

Gas Component GS(M)R limits Typical NEA limit

H2S 5 mg m-3 = 3.3 ppm (v) 5 mg m-3 = 3.3 ppm (v)

Total sulphur 50 mg m-3 50 mg m-3

H2 0.1 mol % 0.1 mol %

O2 1.0 mol % 1.0 mol %

Total inerts GS(M)R gas

interchangeability diagram

≤ 7 mol %

and CO2 ≤ 2 mol %

Gas content GS(M)R gas

interchangeability diagram

Suitable for Ofgem

approved instruments

Total organic halides “impurity” ≤ 1.5 mg m-3

Radioactivity “impurity” ≤ 5 Becquerels g-1

Gas Distribution Network Entry Agreement:

Gas Properties

Gas Property GS(M)R limits Typical NEA limit

HC dewpoint Maintain integrity of grid &

appliances

≤ -2°C up to 85 barg

H2O dewpoint ≤ -10°C @ 85 barg

WN, ICF, SI See GS(M)R gas interchangeability diagram

CV WN calculation > Target FWACV - 0.5 MJ m-3

Characteristic odour

for gas ≤ 7 barg

No component that removes gas odorant or suppresses its

impact on the human nose

Gas temperature — 1 to 38°C

Gas pressure Safe for gas appliances Depends on back pressure

and MOP @ Delivery Point

Analytical requirements for gas-grid entry

For components limited by GS(M)R or NEA must know:

• Concentration in biomethane

• Stability of that concentration

If concentration shown to be negligible and stable then no need for on-line analyser

If concentration shown to be just below GS(M)R or NEA limit (even for short

periods) then on-line analyser mandatory

For some biomethane components there are no on-line analysers available

• Compliance with GS(M)R or NEA can be demonstrated by sampling and analysis

protocol

Components to be monitored on-line

Gas component Typical NEA limit

and therefore maximum

concentration in biomethane

Concentration in raw biogas

H2S 3.3 ppm (v) Up to 30000 ppm

H2 0.1 mol % Up to 4 mol %

O2 1.0 mol % Up to 6 mol %

CO2 2.0 mol % 15 to 55 mol %

H2O dewpoint ≤ -2°C up to 85 barg Saturated

Gas content for

calculating CV, ,

WN, ICF & SI

Suitable for Ofgem approved

instruments

CO2 too high

CH4 too low

Accuracy at the limit of detection

Example: Biogas clean-up plant specification to reduce H2S from 4000 to 1 ppm

Dual-range H2S analyser: 0 – 5000 ppm and 0 – 200 ppm

0 50 100 150 200

Res

po

nse

Low range H2S concentration (ppm)

Accuracy at the limit of detection

Example: Biogas clean-up plant specification of 1 ppm H2S

Dual-range H2S analyser: 0 – 5000 ppm and 0 – 200 ppm

0 50 100 150 200

Res

po

nse

Low range H2S concentration (ppm)

• Repeatability - 1% of FSD = 2 ppm

Accuracy at the limit of detection

Example: Biogas clean-up plant specification of 1 ppm H2S

Dual-range H2S analyser: 0 – 5000 ppm and 0 – 200 ppm

0 50 100 150 200

Res

po

nse

Low range H2S concentration (ppm)

• Repeatability - 1% of FSD = 2 ppm

• Biomethane GS(M)R limit 3.3 ppm

Accuracy at the limit of detection

Example: Biogas clean-up plant specification of 1 ppm H2S

Dual-range H2S analyser: 0 – 5000 ppm and 0 – 200 ppm

0 50 100 150 200

Res

po

nse

Low range H2S concentration (ppm)

• Repeatability - 1% of FSD = 2 ppm

• Biomethane < 3.3 ppm

• Calibration gas – 10 ppm

Interference between components

Example: Paramagnetic analysers for O2 analysis

Sensitive to all paramagnetic molecules including CH4, CO2 and C3H8

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2

Res

po

nse

O2 concentration mol %

• Repeatability 1% FSD = 0.02 mol %

Interference between components

Example: Paramagnetic analysers for O2 analysis

Sensitive to all paramagnetic molecules including CH4, CO2 and C3H8

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2

Res

po

nse

O2 concentration mol %

• Repeatability 1% FSD = 0.02 mol %

• Clean-up plant spec 1 mol %

Interference between components

Example: Paramagnetic analysers for O2 analysis

Sensitive to all paramagnetic molecules including CH4, CO2 and C3H8

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2

Res

po

nse

O2 Concentration mol %

• Repeatability 1% FSD = 0.02 mol %

• Clean-up plant spec 1 mol %

• 95 mol % CH4 will suppress O2 response by 0.15 mol %

Interference between components

Example: Paramagnetic analysers for O2 analysis

Sensitive to all paramagnetic molecules including CH4, CO2 and C3H8

• So although repeatability is still 0.02 mol %, for O2 measurements in

biomethane there is a known bias of 0.15 mol%

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2

Res

po

nse

O2 concentration mol %

Implications for Gas Network Control

Gas Control Centres monitor concentration of GS(M)R and NEA components

If concentration reaches GS(M)R limit, ROV will be closed

As concentration rises towards GS(M)R limit warnings sent to gas producer

Control Desk warning limits depend on accuracy of analyser

Implications for biogas clean-up plant specification

H2S O2

Accuracy 2 ppm 0.15 mol %

GS(M)R limit 3.3 ppm 1.0 mol %

Control desk warning limit 1.3 ppm 0.85 mol %

Checklist for choosing entry point analysers

Questions to ask about your biomethane:

1. Is this component limited by GS(M)R or NEA?

2. What is the concentration in my biomethane?

3. Is the concentration stable?

4. Does the concentration ever approach GS(M)R or NEA limit?

Questions to ask your analyser supplier:

1. Is my target component concentration mid-range?

2. Is the accuracy/repeatability of the same order as the GS(M)R or NEA limit?

3. Will my calibration gas be of a similar concentration to my biomethane?

Thank you for your attention

Contact details:

Diane Broomhall

Technical Consultant

Gas Quality Group, Utilities

GL Noble Denton

+44 1509 282128

diane.broomhall@gl-group.com

www.gl-nobledenton.com