Download 2) Quality of the gas inserted into the network

Regasification Code
Quality of the LNG delivered and the gas redelivered
QUALITY THE OF THE LNG DELIVERED AND THE GAS
REDELIVERED
1)
QUALITY OF THE LNG DELIVERED ................................................................................................... 1
1.1)
1.2)
1.3)
2)
QUALITY OF THE GAS INSERTED INTO THE NETWORK ............................................................. 3
2.1)
2.2)
2.3)
3)
DETERMINING THE QUALITY OF THE LNG UNLOADED ............................................................................ 1
QUALITY SPECIFICATIONS AT THE DELIVERY POINT ............................................................................... 1
MIXING OF THE LNG IN THE TANKS ........................................................................................................ 2
OVERVIEW .............................................................................................................................................. 3
ANALYSIS METHODS ............................................................................................................................... 5
QUALITY SPECIFICATIONS AT THE NETWORK INSERTION POINT .............................................................. 6
CHECKS OF THE PROCESS TO DETERMINE THE QUALITY OF THE LNG DELIVERED ..... 6
4) CHECKS OF THE PROCESS TO DETERMINE THE QUALITY OF THE GAS INSERTED INTO
THE NETWORK................................................................................................................................................... 7
4.1)
4.2)
1)
CHECKING OF INSTRUMENTS ................................................................................................................... 7
AUTOMATIC CHECKS ON THE CONSISTENCY OF THE DATA PROCESSED BY THE SVC ............................... 7
QUALITY OF THE LNG DELIVERED
The qualitative characteristics of the LNG delivered by the User shall be identified by
means of analysis carried out at the Panigaglia Terminal using the methods,
procedures and instruments for measuring quality in use at the Terminal itself.
The qualitative characteristics of the LNG delivered to the Delivery Point must comply
with the quality specifications described below.
1.1) Determining the quality of the LNG unloaded
The LNG quality is determined at the Terminal using its own instruments. The
procedure is based on determining the average composition of the LNG, obtained by
means of:
a) LNG sampling;
b) Gas chromatographic analysis;
c) Calculations based on the average composition of each LNG component (gross
heating value, molar volume, molecular weight).
1.2) Quality specifications at the Delivery Point
The LNG delivered by the User to the Panigaglia Terminal must meet the following
specifications:
Gross heating value components
Component
Methane
Ethane
Propane
Iso-butane
Normal butane
Acceptance values
Unit of measurement
(*)
(*)
(*)
(*)
(*)
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Regasification Code
Hexanes and higher
Nitrogen
Oxygen
Carbon dioxide
Quality of the LNG delivered and the gas redelivered
(*)
(*)
≤ 0.6
≤3
%mol
%mol
(*) Acceptance values for these components are inherently limited by the acceptability range of the Wobbe
index
Trace compounds
Parameters
Hydrogen sulphide
Mercaptan sulphur
Total sulphur
Acceptance values
Unit of measurement
≤ 6.6
≤ 15.5
≤ 150
Mg/Sm3
Mg/Sm3
Mg/Sm3
Physical properties
Properties
Hydrogen sulphide (H2S)
Mercaptan sulphur
Total sulphur
Gross Heating Value
Wobbe Index
Adjustment of the Wobbe
Index(1)
LNG Density
Acceptance values
Unit of measurement
 6 mg/Sm3
 15 mg/Sm3
 150 mg/Sm3
38.18  43.18 MJ/Sm3
47.31  52.13 MJ/Sm3
52.13  53.17 MJ/Sm3
MJ/Sm3
MJ/Sm3
MJ/Sm3
430  470 kg/m3
kg/m3
(1) Interval of use of the adjustment systems present at the Terminal
Please refer to the specific procedure published on the GNL Italia website for the
management of situations where quality data for the LNG delivered by the User is
unavailable.
1.3) Mixing of the LNG in the tanks
The Parties agree that, in view of the technical problems resulting from mixing
volumes of LNG with different density values in the same storage tank at the terminal,
in accordance with Notice No. 616026 of the Ministry of Industry, Commerce and
Handicraft of 11 February 1975, in the event that volumes of LNG are delivered to the
Operator at the Delivery Point with a density that differs by more than ±25 kg/Sm3
from the density of the Liquefied Natural Gas present in the Terminal's storage tanks at
the time of unloading, the Operator shall have the right to delay the unloading of such
LNG volumes at the Terminal, except as laid down in the chapter entitled "Receiving,
storage and regasification of LNG" of this document.
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Regasification Code
Quality of the LNG delivered and the gas redelivered
Where this decision is made, the Operator shall notify the User of the estimated delay
that will be incurred at least 24 hours prior to the arrival date of the Carrier.
2)
QUALITY OF THE GAS INSERTED INTO THE NETWORK
The qualitative characteristics of the gas inserted into the Snam Rete Gas network are
the result of analysis carried out at the Panigaglia Terminal using the methods,
procedures and instruments for measuring quality in use at the Terminal itself.
The regasified LNG inserted into the network by GNL Italia shall meet the quality
specifications for gas entering the Snam Rete Gas network - as specified in the Network
Code - provided that the LNG delivered by the User complies with the specifications at
the Delivery Point, as described above.
In its capacity as owner of the transportation capacity of the Entry Point to the National
Network interconnected with the Terminal in accordance with Article 8 (1) of
Resolution No. 137/02, GNL Italia shall comply with the quality specifications laid
down in the Network Code in accordance with the provisions of Article 8 (1) Annex A
of Resolution No. 185/05, which prohibits the insertion into the national network of
gas that does not conform with specifications or which, although in compliance with
specifications, contains elements that are not normally present in natural gas in
quantities that could harm Users, in order to redeliver the gas to the User at the Virtual
Exchange Point.
However, should any of the aforementioned scenarios occur, GNL Italia, in accordance
with article 19 (1) of Annex A of Resolution No. 185/05, is required to provide prompt
written notice to Snam Rete Gas and the User(s) concerned.
2.1) Overview
Checks with regard to gas quality are performed in the manner and frequency
indicated below. The quality of the natural gas inserted into the network at the
redelivery flange at the Panigaglia Terminal is continuously monitored by two "singlestream" gas chromatographs connected to the SVC (Supervisory Computer System) of
the measurement system, as well as a third gas chromatograph with similar
functionality that works with the other two using a "2 out of 3" logic, interrupting the
supply where two instruments out of three report a specific exception (in relation to
the Wobbe Index value) with regard to the gas composition.
The three gas chromatographs referred to above are installed in a special pressurized
gas-quality control area along with other "multi-stream" gas chromatographs which are
generally dedicated to the analysis of other gas flows from the process, but which can
analyse the composition of the final gas in the event that the instruments specifically
intended for that purpose are all simultaneously unavailable.
One characteristic of regasified natural gas is that it is virtually free of sulphur
compounds. This is the result of a combination of the following factors:
1)
the process for liquefying natural gas is always preceded by a phase of processing
the gas supply designed to remove all the components of the mixture which may
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Regasification Code
Quality of the LNG delivered and the gas redelivered
solidify at typical liquefaction cryogenic temperatures (-162°C) from the natural
gas current (in particular H2O (dehydration) and CO2 (decarbonation)), or at least
reduce the concentration to a level that does not result in precipitation phenomena
or problems of fouling and clogging in subsequent processes. Among these
compounds are branched and cyclic hydrocarbons and, if present in the gas field,
hydrogen sulphide and other sulphur compounds;
2) the regasification process has no possible source that could introduce sulphur
compounds.
With regard to the water and hydrocarbon dew points, the liquefied natural gas
unloaded at the Panigaglia Terminal is well below the network limit as a result of the
treatment carried out at the ports of loading, briefly outlined in point 1).
The sulphur compounds and water and hydrocarbon dew points are determined
discontinuously, according to the procedures and frequency set forth below.
The quality shall be determined on the basis of the chemical and physical
characteristics described below.
Molar composition
Chemical composition in %mol
 Methane
(C1)
 Ethane
(C2)
 Propane
(C3)
 Iso-butane
(i-C4)
 n-Butane
(n-C4)
 Iso-pentane
(i-C5)
 n-Pentane
(n-C5)
 Hexanes and higher
(C6 +)
 Nitrogen
(N2)
 Carbon Dioxide
(CO2)
 Helium
(He)
 Oxygen
(O2)
Sulphur compounds in mg/Sm3. The values of the following compounds are
determined:



Hydrogen Sulphide
Mercaptan sulphur
Total sulphur
(H2S)
(S-RSH)
(S TOT)
Temperature
The temperature of the LNG delivered, expressed in degrees Celsius.
Relative density
The relative density of the gas-air ratio is defined in relation to the densities of gas and
air at reference conditions (Rhos air = 1.22541 kg/Sm3).
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Regasification Code
Quality of the LNG delivered and the gas redelivered
Density
Density (Rhos), expressed in Kg/Sm3, is calculated on the basis of chemical
composition in accordance with standard ISO 6976.
Determination of the Gross Heating Value
The Gross Heating Value (GHV), expressed in KJ/Sm3 is calculated on the basis of
chemical composition in accordance with standard ISO 6976 (in its most recent
version), considering the ideal values of the components recorded in the same standard
(reference conditions: m3 15°C, combustion 15°C).
Wobbe Index
The Wobbe Index (WI) is expressed in KJ/Sm3 and is calculated using the following
formula: WI = GHV/rd.
Water dew point
The dew point of water at delivery pressures of 70 bars, expressed in °C.
Hydrocarbon dew point
The dew point of hydrocarbons in a pressure range of 1-70 bars, expressed in °C.
2.2) Analysis methods
The chemical and physical characteristics set out in section 2.1.1 are determined
continuously by means of the appropriate measurement equipment installed in the
measurement station, or discontinuously with the extraction of gas in a cylinder that is
subsequently analysed in the laboratory.
Continuous
The Operator and Snam Rete Gas shall agree in advance on the type of equipment to be
used for continuous analysis, the accessories required for its operation and the action
plans for the maintenance thereof.
The gas sample to be analysed is extracted by means of probe installed at a
representative point along the delivered gas pipeline, in the middle of the pipeline or at
a point equal to at least one third of the diameter of the higher or lower pipeline.
Discontinuous
Instantaneous sampling is performed on the basis of an agreed frequency, in
accordance with standard ISO 10715/97 or GPA 2166. A report is created when the
sample is taken and the laboratory results are indicated in the Certificate of Quality.
Analysis of Hydrogen Sulphide
The Panigaglia Terminal has a H2S analysis tool that continuously monitors the final
gas.
Sulphur compounds (total sulphur and mercaptan sulphur)
The sulphur compounds, referred to in paragraph 2.1.1 above shall be determined
discontinuously by laboratory analysis, according to the ASTM D5504 method or
another methodology agreed between the Parties or between the Network Manager
and the Operator.
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Regasification Code
Quality of the LNG delivered and the gas redelivered
This determination shall be made each time the continuous analysis produced by the
H2S analyser gives concentration values that are greater than 1 mg/Sm3, or at least
once a year.
2.3) Quality specifications at the network insertion Point
The regasified LNG inserted into the network by the Operator meets the quality
specifications for the insertion of gas into the National Network, as specified in the
Network Code.
Gross heating value components:
Component
Acceptance values
Unit of measurement
(*)
(*)
(*)
(*)
(*)
(*)
(*)
≤ 0.6
≤3
%mol
%mol
Methane
Ethane
Propane
Iso-butane
Normal butane
Hexanes and higher
Nitrogen
Oxygen
Carbon dioxide
(*) Acceptance values for these components are inherently limited by the acceptability range of the Wobbe
index
Trace compounds
Parameters
Acceptance values
Unit of measurement
≤ 6.6
≤ 15.5
≤ 150
Mg/Sm3
Mg/Sm3
Mg/Sm3
Hydrogen sulphide
Mercaptan sulphur
Total sulphur
Physical properties
Properties
Acceptance
values
34.95 ÷ 45.28
47.31  52.33
0.5548 ÷ 0.8
≤ -5
Unit of measurement
Hydrocarbon dew
point
≤0
°C
Max temperature
Min temperature
< 50
>3
°C
°C
Gross Heating Value
Wobbe Index
Relative density
Water dew point
3)
MJ/Sm3
MJ/Sm3
Kg/Sm3
°C
Conditions
At a relative pressure
of 7000 kPa
In the pressure range
of 100 ÷ 7000 KPa
rel.
CHECKS OF THE PROCESS TO DETERMINE THE QUALITY OF THE LNG
DELIVERED
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Regasification Code
Quality of the LNG delivered and the gas redelivered
Every 3 days, GNL Italia usually verifies the calibration of the gas chromatographs that
analyse the quality of the LNG unloaded from the LNG carriers.
Where the User requests further checks of the entire system to determine the quality
parameters of the LNG delivered, GNL Italia shall facilitate such requests for
additional testing.
4)
CHECKS OF THE PROCESS TO DETERMINE THE QUALITY OF THE GAS
INSERTED INTO THE NETWORK
4.1) Checking of instruments
All of the measurement equipment shall be subjected to calibration and periodic
checks to ensure that correct measurements are taken within the maximum expected
accuracy limits.
Where, during the execution of such checks and calibrations, an error is identified that
exceeds the allowed limits, the appropriate action required to eliminate such an error
shall be taken.
In the event that it is not possible to restore the correct functionality of the equipment,
it shall be replaced.
The results of the monitoring and calibration checks are reported by means of specific
reports which are dated and signed by the tester and representatives of Snam Rete
Gas and the Operator.
Regular calibration is also performed on any equipment that is temporarily out of
service.
The instruments and sample cylinders used for calibration are certified by SIT (Italian
Calibration Service) accredited laboratories.
4.2) Automatic checks on the consistency of the data processed by the SVC
The variable data measured by field instruments and the processed data are
continuously checked by the SVC (Supervisory Computer System).
The SVC compares the density values produced by the two gas chromatographs, and
compares them to the data obtained by the reference densimeter.
If the difference between the densities produced by the two gas chromatographs and
between these values and that of the reference hydrometer exceeds acceptable limits,
an asterisk is added next to the density value "Gas Quality Daily Report" for which the
exception was identified.
In the event that such limits are exceeded - with regard to pressure, temperature and
flow rate values - the SVC signals an exception that is reported by the printer alarm. If
the exception does not affect the volume from being determined, the amount shall not
be indicated on the daily report; an asterisk shall be printed next to the parameter
where the limit has been exceeded.
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