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
www.gl-nobledenton.com