Download - APN0028 - LNG facilities

Sheila Crisologo /7 Dräger Safety AG & Co. KGaA APN0028, January 2010

LNG facilities

1 The LNG value chain Typically, natural gas is fed in through over thousands of kilometres of pipelines and compressors transporting the natural gas with high pressure. However, for natural gas producing areas which are not connected directly to pipeline networks the transportation of liquefied natural gas (“LNG”) via special designed ships is the only distribution channel. The important stages of the LNG value chain are:

• Exploration and gas treatment of natural gas • Liquefaction of natural gas into LNG • Transportation of LNG • Storage of LNG • Re-gasification of LNG into natural gas • Supply

Liquefaction facility

LNG storage tank

LNG ship

Loading on LNG ship

LNG Vaporization Facility

Unloading and storage

of LNG Supply

Supply

Natural Gas Field

www.etapii.com/draeger2.html/


1.1 Liquefaction of natural gas Natural gas has to be liquefied for shipping. In the liquefaction facility gas flows through several heat exchangers and is cooled in several stages until it obtains its liquid form, at -259°F/-161°C. By liquefying the ga s, its volume is reduced by a factor of 600. Prior liquefaction components of the natural gas are removed. Although the amount of these components in the natural gas are negligible they might cause damage the facilities, for instance they might freeze up and break the facilities. These components are hydrocarbons, water, carbon dioxide, nitrogen, oxygen and especially sulphur compounds.

1.2 Transportation of LNG LNG is transported in double-hulled ships (a tank within a tank) specifically designed to handle the low temperature of LNG under atmospheric pressure. The inner hull prevents LNG from heating up, expanding and overpressure whereas the outer hull prevents the LNG from spreading out into the ambient air. During loading and transportation a small amount of LNG evaporates. This so called “boil-off-gas" is used for supplement fuel for the carriers or gets re-liquefied and is sent back to the tanks. There are mainly two different carrier types which differ from their tank design: LNG ships with spherical tanks (A) and LNG membrane ships (B). LNG ships with spherical tanks are most common in the past. However, the membrane ships are more and more in demand because their cargo capacity is higher at the same ship size.

(A) (B)

1.3 Terminal At LNG Terminals the LNG is loaded or unloaded. When LNG ships arrived with loaded tanks at the LNG terminals, unloading arms on the dock will be connected to the ship. The ship’s pump transfers LNG through pipelines to storage tanks.


1.3.1 LNG storage tank These specific for LNG designed storage tanks are locally placed next to liquefaction and receiving and re-gasification facilities. After liquefaction LNG is stored in LNG storage tank waiting to be shipped on a specified LNG ship. At final destinations the LNG ship is moored and the unloading arms on the dock have been connected, the ship's pumps will transfer LNG into the onshore LNG storage tanks. LNG can be stored in different types of storage tanks: Above-ground and below-ground tanks. Above-ground tanks are very common worldwide due to their economic construction and their easy maintenance. Below-ground tanks however are more expensive and are more complex regarding maintenance. In-ground tanks, Underground tanks and In-pit tanks are variants of below ground tanks. While the roofs of in-ground tanks are above the ground, underground tanks are completely buried under the earth. Underground in-pit tanks have a double metal shell with an inner and outer tank. The inner tank is made of metal with high resistance to low temperature. Additional insulation of thermal insulating materials and dry nitrogen gas fills the space between the inner and outer tanks. LNG is cryogenic which means that it is not necessary to store LNG under pressure.

1.3.2 Re-gasification of LNG into natural gas Before it is fed in the local pipeline network LNG is re-heated back to its gaseous phase by heat exchangers in re-gasification facilities. LNG is pumped from the storage tanks to the re-gasification facilities. By re-gasification, different media can be used.

In so-called „Open Rack Vaporizer“ sea water is used as heating source for vaporizing LNG. Seawater flows down on the outside surface of the aluminium or stainless steel heat exchanger panel and vaporizes LNG inside of the panel.


In „Submerged Combustion Vaporizer“ the submerged combustion burner uses natural gas to heat water which is used as heat source for vaporizing.

Other types for vaporizing LNG are “Double Tube Vaporizer” (DTV), “Plate Fin Vaporizer” (PFV) and “Air Fin Vaporizer” (HAV) is further techniques to vaporize LNG.

2 Challenge Numerous regulations, guidelines, standards dictate safety arrangements regarding LNG facilities. The standards below address also the gas detector systems.

• 49CFR Part 193 (Liquefied Natural Gas Facilities: Federal Safety Standards) • NFPA 59A (Standard for the Production, Storage, and Handling of Liquefied

Natural Gas (LNG)) • EN 1473 (Installation and equipment for liquefied natural gas - Design of

onshore installations) • ICG Code (International Code for the Construction and Equipment of Ships

Carrying Liquefied Gases in Bulk) The greatest hazard is when LNG spills and is able to form a methane-ambient air -vapour cloud. This happens when leakages on facilities and pipes occur. Therefore almost all facilities are a source of danger. If the methane concentration amount to between 5 Vol.-% and 15 Vol.-% in this mixture, then it is flammable. Supply lines, flanges, valves are potential leakage sources. In order to warn the workers onboard as well on land at or in the facilities in time and in order to take actions preventing any harm, gas and fire detection systems are used.

2.1.1 On board Gas and fire detection systems on board are installed in compressor rooms, control rooms and around the tanks.

Quelle: www.cryonorm.nl


2.1.2 On land Besides smoke detectors, low temperature detectors also gas detectors especially IR sensors for methane detection, open path systems and flame detectors, are deployed at nearly all facilities: Open Path Systems can be used at the unloading berth, at the storage tanks and liquefaction facilities. Infra-red point gas detectors are used at the air inlet to fire equipment and at building heating, ventilation and air-conditioning (HVAC) inlets, at storage tanks and also in the liquefaction and re-gasification facilities. Electrochemical sensors might be used for O3 and NH3 detection for water treatment. H2S sensors could be also used for detecting H2S releases during the gas treatment before liquefaction because untreated natural gas contains a considerable amount of H2S. O2 Sensor might be also installed in areas where workers stay, for example control rooms. The unloading berth is covered by flame detectors. In case of leakage or flame detection workers will be warned, evacuated and extinguishing systems will be activated (foam or/and water) for fire fighting and to limit the vapour cloud dispersion. Further, an emergency shut down will be activated (ESD). A false alarm leads to enormous costs. Therefore it is important that gas and fire detection systems work properly and reliable.

3 Dräger Solutions Dräger offers an ideal system for these applications. Polytron IR (Type 334/340), Polytron IR 3000 and Polytron IR 7000 are suitable for methane detection. Polytron Pulsar, Dräger’s Open Path System, is able to detect the methane-ambient air vapour cloud before it reaches not secured areas or ignitions sources. For minor concentrations in order to detect leakages the catalytic bead sensor IR SE Ex is recommendable. Dräger Flame 1700, Dräger Flame 2300 and Dräger Flame 5000 are ideally suited for use as flame detection. The REGARD family as controller supports actions preventing from damage to personnel and property such as activating extinguishing systems and emergency shutdown (ESD).


3.1.1 USPs Infrared point detectors (Dräger PIR 3000, and PIR 7000, Polytron PIR) Fast response time, operation under extreme environment conditions, very good long-term stability and long life time, no false alarms, easy calibration. Open Path/Pulsar 2 Fast response time (≤ 1 sec.), Span 0-100% LEL (for 4…20mA), operating distance over 100m, solar immune, redundant infrared source with pre-warning of failure, variable source intensity and frequency, no optical alignment tools required, one man commissioning, no further calibration required once commissioned, immune to the effects of sun, flare radiation and common contaminants, pre-warning for dirty or misaligned optics. Dräger Flame 1700 (IR) and 2300 (UVIR) Easy installation and commissioning, quick response, automatic and manual optic check, no false alarms Dräger Flame 5000 No false alarms, offers a true CCTV flame detection solution, on board recording of alarms, worldwide approvals (ATEX, IECEx, FM and CFM), integrated ‘lens check’ can be used as a stand alone detector, digital signal processing and software algorithms to process live video image and interpret the characteristics of a flame

4 References Country Customer Project Contractor Products Year Egypt Spanish

Egyptian Gas (SEGAS)

LNG 1 LNG Offsites & Admin

MW Kellogg IR, Pulsar, TX, Flame IR3

2003

Qatar Qatar Gas LNG Loading Terminal

Salam automation

IR, H2S 1999

Qatar QP GTC 129 LNG Tank Farm

Samsung IR 2004

Australia Woodside Pluto LNG Onshore Foster Wheeler & Worley Parsons

IR, Pulsar, XP Tox

2009

Australia Woodside Pluto LNG Offshore (Riser Plattform)

EOS Singapore

IR, Pulsar 2008

Australia Conoco Phillips Darwin LNG (Onshore)

Foster Wheeler

Pulsar 2004


5 Sources http://www.energy.ca.gov/lng/documents.htmlhttp://www.erneuerbareenergiequellen.com/erdgas_�ussi gerdgas.html http://www.erdgas.ch/de/versorgung-der-schweiz/herkun ft-des-erdgases/lng.htmlhttp://www.naturalgas.org/lng/lng.asp

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