Classification: Internal Status: Draft LNG Shipping TEP 10 Gas Processing and LNG - 2008 Trygve G. Egge 2 Topics Why LNG? Historic overview Commercial fundamentals Technical aspects Operational aspects Technology trends
3 Why LNG? LNG is mainly produced for transportation purposes. More economical to transport gas as LNG compared to pipelines over long distances Volume ratio between natural gas and LNG is approximate 600:1. 4
5 European Cryogenic Courses Commercial fundamentals 6 LNG chain & cost - indications Gas Production Liquefaction Transportation Receiving Terminal $ 0.5-1.5 Bill. $ 1-1.5 Bill. $ 0.6-1.2 Bill. $ 0.5-0.7 Bill. $ 0.5-1.5/MMBtu $ 1-1.5/MMBtu $ 0.4-1.5/MMBtu $ 0.5-0.7/MMBtu Total Chain Cost $ 3.25-4.5 per MMBtu US Average forward HH gas price 2008-2012 = USD 10 MMBtu Source: Fearnley Consultants AS
7 LNG trade routes 8 Development of LNG carrier fleet
9 Newbuilding prices LNGC & VLCC 10 Newbuilding acquisition schedule
11 LNG transportation safety record LNG shipments started experimentally in the mid 1950 s, but the main trades did not begin until late 1970 s. To date there have been close to 40,000 LNG voyages (80,000 loaded port transits) with no loss of cargo! There have been two serious groundings, both in the late 1970 s, but neither of these resulted in cargo loss. As the El Paso Kayser event was very serious, striking a rock at 19kts, and the LNG Taurus grounding at 12 kts, these events are good confirmations of the inherent strength of this type of vessel with its additional barriers and physical separation of the cargo to the sea. 12 European Cryogenic Courses Technical aspects
13 Design Code Design, construction and operation of gas carriers are regulated through UN s shipping organisation IMO (International Maritime Organisation). The regulations are given in the publication International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk ( Gas Code ). Ships intended for carrying liquefied gases in bulk are categorised in three different types (type 1G, 2G/2PG and 3G) according to the product s hazard potential. LNG is classified as requiring type 2G ship 14 LNG transportation technical aspects LNG is transported at 163 deg. C and at atmospheric pressure This extreme low temperature require that the LNG is transported and handled with special consideration, i.e. Completely separated from the ship s hull LNG temperature must be maintained during the voyage requiring efficient insulation of the cargo tanks All cargo handling equipment must be able to operate at the extreme low temperature of -163 degr. C Two basically different cargo containment systems are used: Self supported independent tanks (Moss Rosenberg spherical tanks, IHI SPB, cylindrical tanks) Membrane tanks (Gaz Transport and Technigaz (GTT)) Market share between the two concepts has been ab. 50/50 - but the membrane concept has been increasingly selected for recent newbuilding orders.
15 Spherical tank cargo containment systems (Moss Rosenberg ) 16 Spherical LNG cargo tanks pros & cons Advantages Independent from the ship s hull hull stresses not transferred into the cargo tanks Very robust design No sloshing problems Can operate with partly filled tanks Allow simultaneous building of hull and cargo tanks Easy to inspect Easy to detect and repair leakages Disadvantages Low volumetric utilisation of the hull Larger physical dimensions for same capacity compared with prismatic tanks Visibility from bridge reduced compared with ships with prismatic tanks Require return cargo ( heel ) on ballast voyage to keep cargo tanks cooled
17 Upper half of spherical cargo tank 18 IHI SPB Tank
19 SPB cargo containment system pros & cons Advantages Independent from ship s hull Robust design No sloshing problems/ no filling restrictions High utilisation factor of the ship s hull Allow simultaneous construction of hull and tanks Smaller physical dimensions for same capacity compared to spherical tank design Disadvantages Costly to manufacture the cargo tanks Require heel on ballast voyage to maintain cooled down tanks 20 Ocean LNG Cylindrical Independent Tank
21 LNGC Membrane cargo containment system (GT No. 96, MK I and MK III, and CS1) 22 Mark III (Technigaz) Membrane system
23 Membrane cargo containment system (GTT) pros & cons Advantages High volumetric utilisation of ship s hull Less sensitive to temperature changes as inner membrane (invar steel) has very low thermal contraction coefficient Limited need for heel on ballast voyage Disadvantages Cargo tanks are an integrated part of the ship s hull - hull stresses transferred to cargo tanks Does not allow simultaneous construction of hull and cargo tanks Difficult to detect and costly to repair leakages Restricted filling ratio LNG Carriers Cargo containment systems 24
25 European Cryogenic Courses Operational aspects LNGC operating particulars 26 During transit voyages, boil off gas (BOG) is either used as fuel in the boilers for generating steam (steam ship) or re liquefied A small amount of LNG is retained onboard after discharging ( heel ) and is used for cooling the cargo tanks during the ballast voyage Measurements (custody and fiscal) of LNG is performed on board the ship after loading and discharging. LNG used by the ship is determined for each voyage Total port time is 20 24 hours including port clearance, safety checks, loading/discharging, cargo measurements, connection/disconnection of cargo arms Transit speed between 19 20 knots Fuel consumption about. 150 200 t/24 h (steam ship) Complement 25-30 persons
27 Ship/shore interfaces In order to achieve safe and efficient loading and discharging operation, standardised ship/shore interfaces are important. For LNG ships, the ship/shore interfaces are designed according to the following standards: SIGTTO (Society of International Gas Tanker and Terminal Operators) OCIMF (Oil Companies International Maritime Forum) EN 1532 (European Norm) Typical Ship/Shore interfaces include: Ship size (max/min) Arrangement of loading arms Fender arrangement Mooring arrangement Shore gangway ESD (Emergency Shut Down System) Normal and emergency communication system 28 European Cryogenic Courses Technology trends
29 Market and Technology trends Shipping demand is driven by: New trading routes Increased trading volumes Increased trading distances New vessels are adapting: New areas harsh environment arctic design conditions Increased vessel size Alternative propulsion system 30 LNG trade the past situation
31 LNG trade the future 32 New LNG trades harsh environment New LNG projects are being developed in remote and environmentally sensitive areas. Snøhvit Sakhalin Shtokman For arctic projects, the transportation will require special consideration wrt: Low sea and air temperatures High wind velocity High sea states Reduced visibility Long duration of adverse weather
33 LNG ships design aspects To secure the required off-take and transportation regularity with the highest level of safety, the following design aspects need to be considered: Structural safety (ice strengthening, fatique, extended FEM calculations). Environmental and safety features Navigation Winterisation (enclosed working areas, heat tracing of equipment). 34 Increased ship sizes The increasing demand for LNG, especially in the US and Europe, and the need to reduce long haul transportation costs from the Middle East to US/Europe, is driving the current increase in ship size. While max. ship size for existing terminals is ab. 155 000 m3, sizes in excess of 200 000 m3 has recently been ordered. These bigger sizes are limited to specific projects which involve either the construction of new terminals or the construction of offshore terminals ( Energy Bridge, SRV, etc.)
35 LNG Carriers Growth in the average capacity 36 Illustration of relative size of LNG carriers
37 Alternative propulsion system For the larger ship sizes, propulsion system has become an issue. The draft limitation makes it difficult to design an efficient propeller and hull form for a single screw vessel. This has led to the development of a twin-skeg, twin-screw propulsion arrangement as a design solution for maintaining normal trading speed ( ab. 20 kn). In turn, this has led the industry to look for alternative propulsion systems to the commonly used steam turbine plant. Systems considered are: Dual fuel diesel electric Twin slow speed diesel engines with reliquefaction of boil off gas Gas turbine Of these alternatives, the two first have already been selected for recent large size newbuilding orders. 38 Alternative propulsion system, cont. The main advantage of the diesel alternatives over steam turbine is the improvement in fuel efficiency. Diesel engines have 20 % better thermal efficiency compared to steam turbines. For a diesel LNGC with reliquefaction of BOG, this results in fuel saving of ab. 50 t HFO pr. day (24 h) for a Snøhvit size LNGC. In addition, a full cargo of LNG will be delivered (and paid for)!
39 Steam turbine FO Boiler BOG Advantages Low vibrations High proven reliability Low maintenance cost Dual fuel capability Low NOx emission R/G S/T Disadvantages Low fuel efficiency (ab 30 %) High CO2 emission Large engine room space Few makers Reduced number of skilled engineers 40 Dual Mode Gas/Diesel engines Advantages Environmentally friendly by using gas (no SO x, reduced NO x, reduced amount of particles) High redundancy of propulsion and power generating system Reduced total power installed due to flexibility in different operating modes Disadvantages High initial cost Reduced delivered cargo LNG used as fuel Require high quality fuel (LNG/MDO)
41 Slow speed diesel engines with re-liquefaction system (twin screw) FO Tank G BOG Cycle G C E C G N2 Cycle G FO Tank 42 Slow speed diesel engine with re-liquefaction plant Advantages High overall fuel efficiency Proven propulsion system with high level of reliability No loss of cargo 100% delivered to customer Lower initial cost Reduced CO 2 emission Disadvantages Slightly higher vibration compared to steam and diesel-electric propulsion Need separate auxiliary generators therefore high total installed power High NOx emission Single fuel capability High maintenance cost
43 Gas turbine & electric motors Advantages FO BOG Exh.gas MGO BOG Reduced engine room space Low level of vibration and noise Redundant propulsion Reduced maintenance Gas turbine Low NOx emission Boiler S/T Disadvantages Not used in LNGC yet R/G Motor High initial cost 44 Arctic Shipping
Shipping distances and unit cost 45