Discussion paper Technical standards - Green Gas Grids · By end of 2012 in eleven European...
Transcript of Discussion paper Technical standards - Green Gas Grids · By end of 2012 in eleven European...
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Standards for biomethane as vehicle fuel and for injection into the natural gas grid
22 March 2013
Arthur Wellinger
European Biogas Association
Deliverable 3.6 WG2
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Table of contents
Standards for biomethane as fuel and for injection...................................1
1. Starting position.......................................................................................3
2. The mandate and working groups of CEN TC408 .......................4
3. Experts groups..........................................................................................5
4. Open points to be discussed .............................................................10
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Deliverable 3.6 2nd discussion paper as of March 2013-03-04
Development of standards
1. Starting position
By end of 2012 in eleven European countries biogas was upgraded to
biomethane. In nine countries thereof biomethane was injected into the
grid. The longest experience has Sweden and Switzerland which started
back in the early 90ies.
All of the biomethane countries developed standards for injection (plus
some more countries not injecting biomethane yet) however, a lot of
differences could be found in fundamental aspects such as parameters
and/or concentrations of compounds other than methane, with variations
even up to a factor of 100 (i.e. for mandated oxygen levels). In the past
years, there have been two EU funded projects aiming to develop common
standards for biomethane injection in the natural gas grid. During the FP6
project Biogasmax, a proposal was developed1 which wanted to find a
compromise between stringent formulated parameters created by the
national DSOs and parameters that could be achieved at reasonable prices
and process energy.
Another approach was made by Marcogaz, a technical association of the
natural gas industry. They came close to an excellent solution until the
different DSOs started to water down the proposal. The final proposal could
not find common ground and was abandoned.
During the discussion and formulation of the GGG project, an existing CEN
groups could take over a mandate from the European Commission directly
related to the topic, DG ENER’s Mandate M/475. The GGG work programme
(WP3/WG2) on biomethane parameters therefore planned a close
collaboration with CEN if ever they would start their work but also keep
contacts with IEA Bioenergy Task 37 and Biogasmax.
Arthur Wellinger, project partner on behalf of EBA and WP3 leader is
directly involved with IEA Bioenergy Task 37 work, acting in the agreement
as Technical Coordinator and has therefore easy access to their data. The
link to the (completed) Biogasmax project is also granted because Arthur
Wellinger was directly involved as responsible project partner of the Swiss
partner Berne. As such he was co-author of the recommendations for
injection parameters.
1 www.biogasmax.eu/
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Shortly after the start of the GGG project the EC decided to allocate the
above-mentioned mandate to a new CEN technical committee (CEN TC
408) to develop a standard for both, biomethane as a fuel and for injection,
and this was the reason why the GGG consortium decided to fully
collaborate with this group under formation. This was possible as two
project partners, EBA and NGVA Europe had the right to participate in the
TC as specialized European Associations.
Specific contribution of GGG to the CEN TC408 commission:
GreenGasGrids is represented in CEN TC408 through two of the consortium
partners, i.e. EBA and NGVA Europe. Both partners represent the voice of
the practice. EBA stands for the needs of biogas and upgrading plant
operators as well as of the plant providers. EBA is supported within the
CEN group by two representative of member associations acting within
their country representation: The German Biogas Association (Claudius da
Costa Gomez) and Club Biogaz (Christophe Mandereau). NGVA is the voice
of the engine manufacturers that are in part also directly involved in CEN
(Scania, Volkswagen).
2. The mandate and working groups of CEN TC408
After several discussions between CEN and the Commission, CEN was given
the mandate to develop, as a first step:
• A European Standard for a quality specification for biomethane to be
used as a fuel for vehicles;
• European deliverables such as Technical Specifications or European
Norms for quality specification of biomethane to be injected into
natural gas pipelines transporting either H-gas or L-gas.
The CEN technical experts should consider whether it is possible and
desirable for the proper functioning of the market to develop only one
European Standard addressing the requirements of both applications.
The European Standard on biomethane was to include no unnecessarily
restrictive requirements, as long as the proper functioning in the intended
applications could be guaranteed.
Because the biomethane quality for vehicle fuel is closely related to the
quality of natural gas – which has not been defined so far – the discussion
cannot be separated into two CEN TCs. The work of CEN/TC 408 was
therefore extended and addressed also the issue of CNG (Compressed
Natural Gas) as a fuel, and blends of fossil CNG with biomethane under the
TC umbrella.
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Therefore, the new scope of CEN/TC 408 encompasses now both
biomethane and natural gas as fuels and biomethane for injection into
natural gas grids.
The founding meeting of the CEN TC 408 took place on September 16,
2011 at Afnor in Paris. Erik Büthker from Holland was elected president
while Charles Pierre Bazin de Caix from France was nominated secretary.
Since then the group met eight times in total with the goal to formulate a
draft proposal by fall 2013. In total 10 meetings are planned with
additional focus group meetings, phone conferences and webinars.
Responsible organisms of 17 Countries participate in CEN TC408: Austria
(ASI), Belgium (NBN), Bulgaria (BDS), Czech Republic (UNMZ), Denmark
(DS), Finland (SFS), France (AFNOR), Germany (DIN), Greece (ELOT),
Italy (UNI), Latvia (LVS), Norway (SN), Slovenia (SIST), Slovakia (SUTN),
Spain (AENOR), Sweden (SIS) and the United Kingdom (BSI).
In addition there was an established liaison with seven EU organisations:
Afecor, EBA, Farecogaz, GIE, Marcogaz, ENTSOG and NGVA Europe.
Formal liaisons with other technical committees were established:
CEN/TC 19 on Gaseous and liquid fuels, lubricants and related products of
petroleum, synthetic and biological origin, CEN/TC 234 WG 11 on Gas
infrastructure/ Gas quality and ISO/PC 252 on Natural gas fuelling stations
for vehicles.
A number of stakeholders participated occasionally during the meetings:
Car manufacturers; grid operators; biomethane producers; fuel producers;
natural gas suppliers and manufacturers of gas fuelling stations.
The start was a little difficult for several reasons, the major being that the
mandate was not as clearly formulated as should have been, especially
concerning the job sharing or rather the definition of the responsibilities
between TC 234/WG 11 - M 400 and TC 408 – M 475.
3. Experts groups
In order to allow an efficient work three internal expert groups were
created within the framework of the TC 408:
• EG1: bio-content determination
• EG2: NG/biomethane as a fuel
• EG3: grid injection specification
• EG4: test methods
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3.1 Expert Group 1
A topic which gave reason to long discussions was the expectation of the
Commission as part of the mandate that a method should be developed or
reported allowing the determination of biomethane at any place in the
natural gas grid. It was expected that a C14 method would be applied. An
expert group (EG1) was founded to explore the possibilities.
After the first meeting, the expert group was in full agreement that such a
method would not be feasible at reasonable costs. In an expert discussion
paper it was highlighted that for full demonstration of biomethane various
measurement points along a given grid would have to be installed to follow
the biomethane flow continuously. Such equipment would cost in the order
of 1.5 m Euro.
Other methods to guarantee the mass (energy) balance between the
injected and the removed biomethane like certificates (guarantees of
origin) are proven, cost effective and even more precise. After several
meetings with Kyriakos Maniatis from DG Energy it was decided to describe
a method (as complicated and expensive as it is) for the potential case that
it would have to be determined for legal or contractual reasons close to the
point of injection. But at the same time an easy applicable control method
should be introduced.
3.2 Expert Groups 2 and 3
It was soon realized that it would probably not be possible to define an
equal standard for vehicle fuel and for grid injection. Therefore two
subgroups have been founded. The vehicle fuel group (EG2) is mainly
composed of car manufacturers and led by our project partner Jaime Alamo
from NGVA Europe. The other expert group (EG3) on grid injection includes
primarily the representatives of the national standardisation bodies, TSOs,
gas utilities and the associations. The group is led by Jacques Dubost from
GDF Suez. There is some interaction with EG2 in that the quality
requirements of the vehicle fuel should not be higher as for natural gas
because in next future the large amount of fuel will still be delivered by NG
and not by biomethane. In essence, TC408 is dealing with three major
cases: 1) Gas upgrading and grid injection with subsequent use in housing,
industry or as a fuel; 2) Upgrading without injection and use it as a fuel
either as a stand-alone fuel or as a blend e.g. with LNG; 3) Local
production and local utilisation with very specific requirements (Fig.1)
The challenge of the injection group is to find a common ground between
all the different national parameters. All parameters to be proposed should
therefore be based on sound measurements by standardized sampling and
testing methods. A first list of parameters was proposed for the further
discussion. An outline of the full table is given in Table 1.
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Table 1: Major parameters for grid injection (Source EG3)
In December 2011, EG2 came up with a first proposal for biofuel quality
parameters that served for further discussions (Table 2).
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Table 2. First proposal for parameters defining biomethane quality
(Source EG2)
The discussion on the lower heating value (LHV) has been narrowed down
to 44MJ/kg corresponding to 95% methane. This is a little bit lower than
the value in the German regulation DIN 51624 of 46 MJ/kg (Fig. 2).
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Fig.2 LHV Relation for a binary mixture of CH
4 and CO
2
(Source: E.ON Ruhrgas)
4. Open points to be discussed
A number of points are still open for discussion either because reliable data
are still to be compiled or because the relevant data are not available yet
and must be part of future research projects:
- Sulphur
- Siloxanes
- Trace components that may (or can) have an effect on health
- Exposure models for these trace components
- Oxygen
- Hydrogen
- Methane number (parameter linked to the risk of knocking in
engines, cf. octane number for liquid fuels)
In the case of insecurity preliminary figures will be used in the standard
that will subsequently be adapted. There is still dispute if these values will
arbitrarily be set at a low value and weakened afterwards if possible or if
they should be set at the upper limit of known band width and
subsequently be reduced if necessary.
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4.1 Hydrogen Sulphide
ECE R110 sets a limit (for safety operation of Natural Gas Vehicles) of 23
mg/m3 and the German DIN 51624 sets 7 mg/kg.
The requirements for the limit of the H2S concentration are quite different
depending on which client the participant is representing:
Volkswagen requests a sulphur limit of max.10 ppm in CNG. Their
argument is that petrol and diesel fuel already are at a limit of 10 ppm
sulphur. The limit is dictated by the under-floor catalysts which cannot
recover from high sulphur contents at low temperatures.
Bosch promotes a North American study which proposes some 3,5 - 7
mg/kg limit due to the H2S combustion products sticking ICE valves.
ACEA also asks for a limitation at 10ppm in fuel where as TC234/WG11
could accept 20mg/m3 in the grid.
The Netherlands have experience with a H2S content of natural gas
delivered to the domestic market of close to zero and always lower than 5
mg/m3 whereas in Italy that H2S in their network code is a value below 6.6
mg/m3 (m3 at 1.01325 bar and 288 K).
The biomethane producers promote a value not lower than 10ppm.
The current discussions in TC 408 tend towards 5 to 10ppm.
4.2 Siloxanes
Siloxanes might create serious problems in engine pistons (Fig.3) and
especially in micro-turbines. When siloxanes are oxidized, silicium oxide is
formed that covers surfaces leading to abrasion or even blocking of
engines. Siloxanes are mainly a problem in biogas coming from landfills
and sewage sludge digestion. Main sources are sanitary products
(maquillage, tooth paste, shaving foams, etc.), foam from fire
extinguishers, lubricants, etc. The German delegation reported, through its
Bosch representative, of tests studying the impact on lambda sensors
claiming the need for a total silicon content below 0,06 mg/kg. The main
reported problem is linked to the effects of silicon glass layer covering the
active electrodes of lambda sensors and creating malfunction in the signal
to be transmitted, plus a potential deterioration of the catalytic active
platinum-based electrodes
Standard procedures in Austria and Switzerland are active carbon filters to
remove the siloxanes. If low values have to be achieved, cooling down to
-25°C is necessary.
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Fig. 3 Silicium Oxyde (SiO2) formation on engine pistons and piston
blocks
Several documents have been made available by different experts. Limits
are depending on the application but the most strict ones for gas turbines
and ICEs (ranging from 0,05 mg/Nm3) up 2mg/Nm3 for gas engines.
There is still no agreed sampling and test method available yet. DNV KEMA
has presented a project proposal to the EC for engine testing and GERG is
willing to work in the sampling and test methods.
4.3 Water dew point
Water content/water dew point: as both parameters are important and are
also correlated (ISO 18453) CEN TC408 decided to limit only one of them,
and preferably the dew point (Fig.4).
Fig. 4 Water dew point in function of water content and pressure
The proposal under discussion is to create a variable limit depending on the
different climate zones:
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Zone A: 0 0C at 200 bar
Zone B: -10 0C at 200 bar
Zone C: -20 0C at 200 bar
Zone D: -30 0C at 200 bar
The duty of the national regulators is to specify to which zone they belong
4.4 Methane number
Methane Number is the measure of resistance of fuel gases to engine
knock (detonation) and is assigned to a test fuel based upon operation
in a knock testing unit at the same standard knock intensity. Pure
methane is assigned as the knock resistant reference fuel with a methane
number of 100. Pure hydrogen is used as the knock sensitive reference fuel
with a methane number of 0.
Gas Infrastructure Europe (GIE) is an association representing the sole
interest of the infrastructure industry in the natural gas business such
as Transmission System Operators. They are against the introduction of
a methane number mainly for two reasons:
1. A Methane Number of 80 as recommended by Euromot (the
European Association of Internal Combustion Engine Manufacturers) would
endanger the Security of natural gas supply to the European market,
limiting acceptable gas sources (e.g. from LNG).
2. Including the Methane Number in the European Standard
requires an agreed and reliable method of determination and should
incur minimum costs.
The methane number ( M N ) is not a thermodynamic property of gas,
so no Equation of State (EOS) can be used to calculate it. Moreover,
there are different calculation methods available and the results are
different depending on the method applied as listed below:
- Linear Correlation method
- Hydrogen/Carbon (H/C) ratio method
- AVL method - AVL Inc. developed a method to calculate the methane
number, based on experimental measures of different gas mixtures (up to C4, H2, CO2 and H2S). Property software is available to purchase
which uses proprietary algorithms to determine the Methane
Number, but does not take into account all components.
- E.ON- gas calculation
- Calculations of various engine manufacturer methods
Euromot asked for a Methane Number between 80 and 100 which would
exclude the majority of available LNG from coming to Europe (Fig.5). The
argument of Euromot is that a methane number below 80 would reduce
the efficiency of modern gas engines (Fig.6).
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Fig.6 Methane Number versus Wobbe index of imported LNG
Fig. 6 Example of efficiency of gas engines (CHP) with different methane
numbers
A Methane Number of 80 would endanger the Security of natural gas
supply to the European market, limiting acceptable gas sources. For
example, Denmark has been supplied with natural gas with a
methane number around 70 (AVL method) from the Danish part of the
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North Sea for more than 20 years. The span of variation is typically
from 65 to 75, all of which would require further processing or
curtailment if the gas standard required a Methane Number above 80.
Gassco has also expressed its concerns about the inclusion of the Methane
Number since it may affect Norwegian gas exportations.
As mentioned before, the inclusion of a Methane Number in the
European Standard requires an agreed and reliable method of
determination and should incur minimum costs. There is no commonly
agreed Methane Number calculation method today:
- The only methods to calculate Methane Number included
in an international standard do not correctly predict the
trend of the Methane Number when hydrogen is injected.
- Current methods do not take into account the presence of
hydrocarbons heavier than butane.
- Some methods to calculate Methane Number (e.g. AVL)
require the purchase or development of property software in
order to be used effectively.
ACEA and car industry is opting for a methane number of 70 (AVL method).
This corresponds also to the engine test fuel.
4.5 Oxygen
There is a large variety among the different countries in the allowed
oxygen content from 0.1% up to 3% (Table 3) whereby the 0.1 correspond
already to a 10 to 100 fold increase in France, the UK respectively in Spain.
For the general NG grid specification, CEN/TC 234 is proposing to make it
variable depending on aspects such as proximity to underground storages,
though the limits are still to be discussed. For biomethane injection into the
grid some preliminary values ranging between 0,1 and 2% have been
proposed.