Launched from the Wison Shipyard in Shanghai, China, the Exmar Offshore and Pacific Rubiales Energy Caribbean FLNG is making its slow journey

across the Pacific Ocean to its new home off the coast of Colombia in the Caribbean Sea. The Caribbean FLNG looks to be the first commissioned floating LNG (FLNG) project in the modern era of dedicated FLNG production. Scheduled to be commissioned in late 2015, the floating liquefaction, regasification and storage unit (FLRSU) will provide 69.5 million ft3/d of natural gas, or 0.5 million tpy. Black & Veatch was contracted for the topside liquefaction

process and cooperated with the engineering, procurement, construction, installation and commissioning contractor (EPCIC), Wison Offshore & Marine Ltd, for the manufacturing.

The FLRSU features the Black & Veatch PRICO® liquefaction system and will supply approximately 140 000 – 160 000 m3 of LNG for export on the spot market. What makes this FLRSU different from typical FLNGs is the regasification capability. This was added to the barge as part of an agreement with the owner of the gas field as a way to supply natural gas to onshore Colombia.

Christopher Campos, Ebara International Corp.,

Cryodynamics Division, USA, takes a look at the acceleration

of floating applications in the LNG industry.

FLOATING

APPLICATIONS

ON THE RISE

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Ebara International Corp., Cryodynamics Division (EIC Cryo) was awarded the contract for the design and manufacturing of high pressure booster pumps to be used in the regasification process. Unlike typical multi-stage, high pressure pumps used in land-based applications, a special design had to be utilised for the marine installation and environment. Simple metals such as carbon steel could not be utilised for these applications, given the corrosive nature of the marine environment. Additionally, the close proximity of the booster pumps to the hazardous area location required increased safety in enclosures and junction boxes.

Finally, operating a multi-stage high pressure pump on a floating barge presented a challenge. This meant that the submerged motor pump would have to be able to withstand buoyant forces during operation and non-operation. Modelling these forces required rotor dynamic simulations (RDS) to determine the axial and torsional forces bestowed upon the pump from the heave, roll and sway of the barge (Figure 1).

Radial diffusers were selected instead of the classic axial design in order to provide a compact solution to the multi-stage pump. By using a compact radial diffuser (referenced to shaft) to diffuse the LNG from the impeller vane, the impeller can conveniently fit inside the housing. Compact fluid passages then transfer the LNG from one stage to the next via the housings, which results in almost a 20% reduction in pump height and weight. In many cases, hydraulic efficiency can often increase due to the reduced disc friction caused by moving LNG over elongated axial diffusers. The end result is a more compact multi-stage, high pressure pump with higher hydraulic efficiency.

These evolving technologies are still being explored as the popularity of floating storage and regasification units (FSRUs) increases. The FSRU offers a quick and relatively inexpensive solution to providing natural gas for any number of applications. Additionally, the use of FSRUs to supply fuel to power plants is becoming an increasingly sought after option.

Mammoth at seaRoyal Dutch Shell plc started conceptual design of an FLNG in the mid 1990s. In July 2009, Shell awarded the first FLNG contract to French contractor Technip S.A. and South Korean shipbuilder Samsung Heavy Industries (SHI). The concept was simple – Technip would design the liquefaction process (topside) and SHI would design the hull and storage tanks (hullside). On 20 May 2011, Shell made the final investment decision (FID) to construct Prelude.

EIC Cryo has worked with SHI on many LNG carriers and assisted Technip with several land-based receiving and export terminals. The company has also worked with Shell as an overall supporter of submerged motor equipment, as well as on liquefaction projects using the submerged generator expander to increase LNG production and efficiency while reducing boil-off gas (BOG).

In 2010, Shell, Technip and EIC Cryo entered into a FEED contract to design an LNG expander for use in the Prelude liquefaction process. The technology included utilising a design improvement of an upward flow orientation to improve shaft balancing and reduce vapour bubbles that may cause cavitation. Vapour bubbles naturally rise and will exit out through the discharge nozzle positioned at the top of the expander. EIC Cryo adapted the electrical components, instrumentation and inlet vessel/headplate for the marine application.

Submerged motor pumps and expanders utilise a dual glass seal conduit connection (feedthrough) to provide a barrier between the non-hazardous area and the hazardous area outside of the sealed vessel. This feedthrough contains a purge cavity that can be inertly filled and monitored with nitrogen and added purging systems. Two purge nozzles act as an inlet and outlet to this purge space. With the knowledge of the pressure of the nitrogen contained in the purge space, any increase in the pressure in the purge space could indicate a leakage of vapour

Figure 1. Linear and rotational ship motion.

Figure 2. High pressure booster pump.

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from the seal. Additionally, any loss of pressure from the purge space could indicate a leakage outside of the purge space. There are no specific requirements for monitoring this purge space, even under NFPA 59A, Standard for the Production, Storage and Handling of Liquefied Natural Gas (LNG). However, the technology to add purge monitoring devices is available. EIC Cryo has developed its own standard system that includes the necessary items of tubing, valves, gauges, pressure indicators and transmitters. Remote transmitters are also available for sending updated data to a monitoring device. The purging system is constructed in a mountable rack and contains inlet and outlet nozzles for connections to a constant supply of nitrogen and power supply connection.

Based on lessons learned from the Prelude FLNG project, FEED studies have already started on future Shell FLNG projects utilising the same applications and equipment. The goal will be to streamline the complex design and manufacturing process.

Simplified processWhile Prelude is estimated to cost approximately US$13 billion, there are other simpler options available. At 5.3 million tpy, consisting of 3.6 million tpy of LNG, 1.3 million tpy of condensate and 0.4 million tpy of LPG, the Prelude FLNG is a multi-train FLNG plant. However, if only 1 – 2 million tpy is required, then a smaller solution will suffice. This was the goal of the Petronas FLNG (PFLNG1) project.

The PFLNG1 project signalled the second in a consortium of engineering companies to design and manufacture a super floating facility. At approximately one-fifth of the size of Prelude, PFLNG1 will be designed, manufactured and commissioned in half the time of Prelude. Current projections estimate the commissioning of PFLNG1 by the end of 2015.

EIC Cryo supplied LNG cargo pumps that were selected for offloading and transferring LNG. The LNG cargo pump has been in existence for over 40 years, during which time the capacity and discharge pressure has steadily increased. Most cargo pumps have been designed to operate at a power supply of 60 Hz. The PFLNG1 and PFLNG2 were designed to operate at 50 Hz (as is common in Malaysia). So why would this make a difference?

Differential pressure produced by the pump’s hydraulics is a function of the commonly known Affinity Laws. At a fixed trim impeller, the differential pressure developed by a 60 Hz pump will be higher than the differential pressure developed by a 50 Hz pump due to the pump’s rotational speed. As a result, if the same capacity and differential pressure is to be developed using a 50 Hz frequency, the pump’s fixed impeller trim has to become larger. This is the case with PFLNG1, as EIC Cryo designed and manufactured one of the largest submerged motor cargo pumps to be mounted in a floating vessel.

New lifeIn 1975, Gotass-Larsen Shipping Corp. entered the LNG market with its first LNG carrier, named Hilli. In 1997, Osprey Maritime Ltd acquired Gotaas-Larsen and then later formed an LNG shipping company in 2001. Golar World Shipping has been expanding its fleet of LNG carriers and has converted and built a number of FSRUs since.

Now nearing 40 years old, the original Golar Hilli LNG carrier was due to enter into retirement. Designed with six spherical tanks, the 125 000 m3 LNG carrier (built by Moss Rosenburg, Norway) was given a new life by building a

liquefaction process on the topside, using the tanks as storage for the newly processed LNG.

Prior to commencing work, Golar LNG studied the market for FLNGs and determined a number of opportunities that could use the Golar Hilli FLNG and additional converted FLNGs. The sister ships Gimi and Gandria are also planned for FLNG conversion. Golar has identified the advantages of using

Figure 3. Single-phase upward flow expander.

Figure 4. Dual seal feedthrough with N2 purge ports.

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converted FLNG over land-based or newbuild plants. First, Golar estimates that the conversion would only take 31 months (shorter than a newbuild or land-based plant). Second, the converted FLNG is estimated to cost approximately US$588 million, compared to the US$13 billion required for the Prelude FLNG.

Golar LNG contracted Black & Veatch to conduct a study to provide its PRICO® liquefaction technology for the FLNG. The converted FLNG would produce approximately 2.8 million tpy of LNG. EIC Cryo supported the liquefaction process by adding an LNG expander to improve the liquefaction production efficiency. The Hilli FLNG will be the second FLNG to feature the submerged generator LNG expander.

Future awaitsSome analysts believe that floating applications simply cannot replace traditional land-based liquefaction plants, receiving terminals and export terminals. However, floating applications can provide an alternative solution to the traditional land-based plant. FLNGs and FSRUs can also provide a quicker operation time and potentially reduced cost, depending on the scale of the project.

These are the current evaluations taking place with one such project off the coast of Mozambique. Eni S.p.A is in partnership with PetroChina, Galp Energia, Kogas and the National Oil Company of Mozambique (ENH) to develop the

Area-4 region of Rovuma Basin. An FLNG is currently in the evaluation stage, utilising a parallel FEED of multiple consortium engineering, procurement and construction (EPC) contractors. This consortium includes SHI/Technip, Daewoo Shipbuilding and Marine Engineering (DSME)/KBR, and Hyundai Heavy Industries/Saipem/Chiyoda. Each consortium will provide its design of the FLNG concept, with estimated construction costs and time to delivery. Final evaluation of the designs and FID will be conducted by the Eni partnership.

As suppliers and cooperative design solution providers to EPC contractors, EIC Cryo expects to provide recommendations and support to each of the designs. The company hopes to recommend design influences for the LNG expander in the liquefaction process, as well as solutions for the offloading cargo pumps.

Bibliography• HINE, L., ‘ENI lays down ambitious schedule for FLNG

production unit off Mozambique,’ TradeWinds, London, http://www.tradewindsnews.com/weekly/339554/eni-lays-down-ambitious-schedule-for-flng-production-unit-off-mozambique (20 June 2014).

• SMITH, C. E., ‘ENI lets FEED contract for Mozambique FLNG,’ Oil & Gas Journal, http://www.ogj.com/articles/2014/10/eni-lets-feed-contract-for-mozambique-flng.html (16 October 2014).

• SINGH, G., ‘EXMAR launches FLRSU to exploit stranded gas offshore Colombia,’ http://www.Offshore-Mag.com (1 August 2014).

• ‘FLNG firmly on the radar’; ‘Golar in high-risk, high-reward play,’ Offshore LNG Supplement (November 2014).

• Golar LNG, courtesy of Golar LNG website, http://www.golarlng.com/index.php?name=Company_Facts%2FHistory.html

• ‘All set for a soft LNG winter’, LNG World Shipping (November/December 2014), pp. 8 - 10.

• LNG Shipping at 50, A Commemorative SIGTTO/GIIGNL Publication (2014), pp. 92 - 93, 96 - 97, 99 - 101, 104 - 105.

• ‘PETRONAS signs agreement for floating LNG solutions joint venture,’ http://www.petronas.com.my/media-relations/media-releases/Pages/article/PETRONAS-SIGNS-AGREEMENT-FOR-FLOATING-LNG-SOLUTIONS-JOINT-VENTURE.aspx (15 May 2009).

• ‘PETRONAS holds steel cutting ceremony for floating LNG facility,’ http://www.petronas.com.my/media-relations/media-releases/Pages/article/PETRONAS-HOLDS-STEEL-CUTTING-CEREMONY-FOR-FLOATING-LNG-FACILITY.aspx (25 June 2013).

• ‘PETRONAS commenced topside module lifting for its first floating liquefied natural gas facility,’ http://www.petronas.com.my/media-relations/media-releases/Pages/article/PETRONAS-COMMENCED-TOPSIDE-MODULE-LIFTING-FOR-ITS-FIRST-FLOATING-LIQUEFIED-NATURAL-GAS-FACILITY.aspx (24 September 2014).

• ‘Standard for the Production, Storage and Handling of Liquefied Natural Gas (LNG),’ National Fire Protection Association (NFPA) 59A (2006).

• Shell Prelude Project, courtesy of Shell website, http://www.shell.com/global/aboutshell/major-projects-2/prelude-flng.html

• GOSDEN, E., ‘Shell’s giant floating refrigerator to tap new gas reserves,’ The Telegraph, http://www.telegraph.co.uk/finance/newsbysector/energy/10390228/Shells-giant-floating-refrigerator-to-tap-new-gas-reserves.html (21 October 2013).

• ‘Wison of China Nets FLRSU Order from Exmar,’ LNG World News, http://www.lngworldnews.com/wison-of-china-nets-lng-flrsu-order-from-exmar/ (1 June 2012).

Figure 5. Submerged motor cargo pump.

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