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LNG Transport & Terminals |
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 Natural Gas is often sourced long distances from consumers. For shorter distances (less than 3000 km), transport by pipeline is generally used. Over longer distances, it is more economical to transform the Natural Gas into Liquefied Natural Gas (LNG) for transport. One cubic meter of LNG is equivalent to 600 m3 of Natural Gas, making the volume to be transported much more attractive.
Bulk transportation of LNG is generally done using ocean-going LNG Carriers. This allows transport from the LNG loading terminal to the LNG receiving terminal. The receiving terminals have storage and vaporisation systems to allow Natural Gas to be fed into the local gas distribution system as required, according to consumption.
Since natural gas liquefies at cryogenic temperatures, i.e. temperatures well below -100°C, there is continuous boil-off of a small portion of the liquefied natural gas during transportation and storage. This is termed natural boil-off gas (NBOG). Specialised equipment is required in order to handle this boil-off on both land and marine storage facilities. On ocean-going LNG carriers, this NBOG is frequently used to provide a source of fuel for the vessel propulsion, using boilers feeding steam turbines, or feeding directly to dual fuel diesel engines coupled to electric propulsion units. In case that additional fuel is required, additional cargo is vaporised to make up the shortfall. |
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The Applications
LNG Carriers
 Cargo Handling machinery
Cryostar supplies the necessary High Duty (Vapour Return) compressors, LNG Vaporizers and Natural Gas Heat exchangers required for loading, unloading and tank maintenance operations. This equipment ensures that tank pressures are maintained within the allowable pressure range during normal operations.
High duty Compressor: Download the data sheet (.pdf)
 Fuel Gas supply systems
Cryostar has considerable experience in supply of machinery for all propulsion systems used on LNG carriers. This includes vessel with Steam Turbine as well as Dual Fuel Diesel Electric (DFDE) propulsion. Various models of machinery are available to suit the operator’s requirements. Special technology is used in some cases to cool the NBOG to ensure sufficient fuel gas pressure for the engines.
More recently, the trend for DFDE vessels is to use 4-stage Low Duty compressors, which do not require any precooling and allow the vessel to burn the remaining liquid in the tanks (heel) on the ballast voyage, saving Heavy Fuel Oil costs.
For the Fuel Supply systems requiring higher pressures, water Aftercoolers and Intercoolers may be used to control temperatures to either engines or Gas Combustion Unit (GCU)
1-stage Compressor for Steam Turbine propulsion
2-stage Compressor for DFDE propulsion:
Download the data sheet (.pdf)
4-stage Compressor for DFDE propulsion:
Download the data sheet (.pdf)
Reliquefaction
Vessels fitted with 2-stroke slow speed diesel engines which do not consume the NBOG, require a means to maintain safe cargo tank conditions and recover the NBOG. Cryostar’s famous EcoRel reliquefaction plants have been fitted to the world largest LNG carriers, Qatargas’ Q-Max series of vessels as well as smaller vessels.
Regasification
For installation onboard regasification vessels or FSRUs. Cryostar has plants of Open- or Closed-Loop designs to use either steam or seawater as heating medium. In addition, equipment required for BOG recondensers is available.
EcoVap LNG regasification plants: Download the data sheet (.pdf)
Land-based
Reliquefaction
Storage tanks which are used for long-term storage benefit from the installation of reliquefaction plants which can recover the natural Boil-off gas and return it to the tanks, allowing a zero send-out strategy to be followed.
EcoRel BOG reliquefaction plants:
Download the data sheet (.pdf)
Return Gas Blowers and BOG Compressors
Cryostar’s proven single stage compressors are used as gas blowers or multi-stage compressors for BOG compressors either designed according to our standard or in API 617 execution. Together with BOG compressors, BOG recondensing systems may be provided.
1 and 2-stage BOG Return Gas Blowers
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 The Equipment
Cryogenic Compressors
Electric motor or steam turbine driven single-stage or multi-stage cryogenic compressors complete with lube oil system, seal gas system, and accessories. These units can handle any type of cryogenic gas. Incorporating a bulkhead for marine applications, the single skid design provides a solid foundation for these robust machines. Anti-surge controller and instrumentation are provided.
Heaters & vaporizers
Shell and U-tube design, all stainless steel, directly heated by saturated steam. The equipment consists of a single pass shell with stationary head, fully welded to the U-tube bundle. They are intended for cryogenic applications.
Water Inter and Aftercoolers
Shell and straight-tube design with compensators where necessary. All stainless steel construction, directly cooled by fresh water. The equipment consists of a single pass shell fully welded to the tube bundle. They are intended for cryogenic applications.
LNG Pumps
Cryostar offers a wide range of centrifugal or reciprocating cryogenic pumps available for LNG applications. Including reciprocating high pressure fuel gas (300+ bar) supply for direct injection 2-stroke diesel engines, as well as feed pumps, condensate return pumps, gas turbine fuel gas feed pumps and numerous other applications.
High pressure pump:
Download the data sheet (.pdf)
N2 Companders
A Cryostar design first delivered in 1996, this machine type combine of compressor and expander stages on the same gearbox and frame to produce the cold power required for liquefaction processes. This design is unique in that the expander expansion energy is directly recovered and offsets the input power required. |
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Processes
BOG Reliquefaction
Cryostar’s patented reliquefaction processes are based a Brayton cycle with nitrogen as an inexpensive and safe cooling medium. A compander produces the cold power and cryogenic heat exchangers are used to change the BOG back to liquid form for return the storage tanks. Full in-house process engineering, mechanical design as well as rotating machinery manufacture allows optimum matching of equipment to process.
LNG Regasification
Cryostar’s modular skid-mounted design is offered using one of three process, using steam or seawater as the heating medium.
LNG carrier Fuel Gas supply systems
Cryostar is in the unique position of being able to provide the equipment as well as the process know-how for fuel gas supply systems, having been intimately involved in many new developments in fuel gas supply over the years. Providing new technology has allowed Cryostar to lead in this field and offer the market the most up-to-date solutions to the wide operational requirements demanded by vessel operators.
Special Processes
Cryostar has the ability to perform studies for specific applications or operational circumstances to provide solutions to specialised operational problems or conditions.
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