University of Technology Gothenburg SHIPPING AND MARINE TECHNOLOGY MARTIME ENVIRONMENT AND ENERGY SYSTEMS. Cecilia Gabrielii Lecturer, PhD

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1 University of Technology Gothenburg SHIPPING AND MARINE TECHNOLOGY MARTIME ENVIRONMENT AND ENERGY SYSTEMS Cecilia Gabrielii Lecturer, PhD

2 What is LNG: properties and facts LNG - what is it? Production, storage, transport Properties and behavior

3 What is LNG? Natural gas that is converted to liquid for ease of storage/transport LNG takes up about 1/600th of the volume of natural gas. Natural gas becomes a liquid (LNG) at approximately -162 C Transported and stored at around -162 LNG s extremely low temperature makes it a cryogenic liquid. LNG as marine fuel a way to reduce air pollution

4 LNG produced for transportation purposes Gas market is often far from the natural gas source LNG offers greater flexibility than pipeline gas There are challenges with storing / transporting LNG

5 Outside of storage tanks LNG quickly warms back into natural gas Volume expansion 600

6 Inside storage tanks LNG eventually warms back into natural gas so called Boil Off Gas BOG Volume expansion 600 Tank pressure increases 20 C -162 C

7 LNG s principal hazards result from its Cryogenic temperature Vapor expansion and dispersion characteristics Flammability characteristics If an LNG release occurs, there is an immediate potential for a range of different outcomes and types of consequences.

8 From gas field to users

9 Exploration/production

10 Natural gas reservoirs Conventional gas - porous reservoir with sufficient permeability to allow gas to flow to producing well Unconventional gas - Deposits in relatively impermeable rock formations artificial pathways have to be created

11 What is natural gas? Crude oil and natural gas constitute of hydrocarbons Gas from different sources have different chemical composition Methane is by far the major component, over 80%

12 Typical natural gas composition And impurities such as hydrogen sulphide, water and mercury

13 From the natural gas production/exploration plant Natural gas is transported in pipelines to the processing and liquefaction plant

14 Processing and liquefaction plant Composition before Composition after

15 Processing and liquefaction plant -162 C

16 Processing before liquefaction Removing of impurities hydrogen sulphide (H 2 S) and mercury Removing components which would freeze at the liquefaction water vapour and carbon dioxide Removing heavier hydrocarbons raw materials to industry or used as fuel at the plant

17 Liquefaction The gas is cooled down in stages until it is liquefied, at -162 C Nitrogen removal Nitrogen decreases the energy content in LNG Nitrogen

18 Typical LNG composition Others: Ethane < 4% Propane < 1% Butane < 0.5% Nitrogen < 0.5%

19 LNG can now be transported wherever needed

20 Transport of LNG By truck very short distances specialised, double-skinned tank trucks By ships long distances in a special purpose LNG carrier good insulation and a double hull design

21 LNG Carriers 50 years ago Methane Princess - the first ship built purposely for transport of LNG Capacity of m 3

22 LNG Carriers - today 350 carriers - average capacity of m 3 Specifically designed to contain LNG at or near atmospheric pressure at a cryogenic temperature of approximately -162 C

23 How to keep LNG in its liquid form? Tank insulation will not keep the LNG cold enough to remain as a liquid by itself Auto-refrigeration LNG stays at near constant temperature if kept at constant pressure. Achieved if the LNG vapour boil off (BOG) leaves the storage tank -162 C 20 C

24 How to handle the boil-off? Use it as fuel in the propulsion machinery Steam turbine propulsion Dual fuel engines Re-liquefy and send back to the LNG tanks Disposal of boil-off gas to atmosphere Only in an emergency situation

25 LNG Carriers two different tank systems Spherical Membrane

26 Spherical - self-supporting - tank Tank shell: 30 mm aluminium or 9% nickel steel Insulation: 220 mm of e.g. polystyrene foam Spherical; high degree of safety against fracture or failure

27 Membrane tanks not self-supporting - the inner hull forms the load bearing structure very thin primary barrier to 1.5 mm stainless steel or nickel alloy utilize the hull shape more efficiently larger cargo capacity must always be provided with a secondary barrier

28 Which type is the best? Spherical Membrane Simple construction Independent from the ship's hull Can be partially pressurised Larger cargo capacity Less tank weight Lower windage area

29 LNG has arrived at the import terminal! Onshore terminal or floating (FSRU)

30 Feeder vessel to intermediate terminal Feeder vessel Regional distribution of LNG Typical cargo capacity: m 3

31 At the receiving terminal (import / intermediate) LNG is either re-gasified into natural gas delivered to the gas grid or LNG is delivered to a truck or bunker vessel which deliver it to a LNG fuelled vessel LNG is re-gasified just before entering the engine

32 Some components at the terminal Cryogenic pipelines Storage tanks Boil-Off Gas (BOG) compressors and re-condensers Pumps Vaporisers (re-gasifiers)

33 Onshore terminal storage tanks Flat bottomed tanks (FBT) - stores LNG under atmospheric pressure Semi-pressurised tanks - stores LNG under pressure (approx. 10 bar) withstand cryogenic temperatures maintain the liquid at low temperature minimize the amount of evaporation (BOG)

34 Example of LNG bunkering terminal From the atmospheric FBT : High pressure pump Regasification To the natural gas grid From the semi-pressurised tanks: To truck or bunker vessel

35 Storage tanks how to prevent leakage of LNG? LNG tanks have more than one means of containment. Primary the tank which holds the LNG, with insulation Secondary dikes, impoundment dams around storage tanks, or: second tank around the primary storage tank

36 Atmospheric pressure tanks (FBT tanks) Large tanks (> m 3 ) Built on site on flat-base concrete foundations A system for BOG is needed Different types Double containment Full containment

37 Double containment tank In case of failure/leakage: LNG is contained by a concrete bund wall But uncontrolled release of LNG vapour to the ambient

38 Full containment tank In case of a failure / leakage The outer tank - concrete wall - is capable of containing both LNG and LNG vapour (controlled venting of the vapour)

39 Handling of the Boil-off Gas (BOG) % of the total tank content per day -162 C This gas is captured and sent to the pipeline (gas grid), or re-injected into the LNG carrier during the unloading, or re-condensed and sent back to the storage tank, or sent to the flare - only in abnormal or accidental situations

40 Handling of the Boil-off Gas (BOG) BOG

41 Regasification LNG is warmed back to natural gas and delivered by pipeline to consumer.

42 Regasification The atmospheric storage tanks are equipped with submerged pumps that transfer the LNG towards high-pressure pumps.

43 Regasification The pressurised LNG is then turned back into a gaseous state in vaporizers (warmed by seawater).

44 Example of LNG bunkering terminal From the semi-pressurised tanks: To truck or bunker/vessel

45 Pressurised tanks Small scale tanks - typically 1000 m 3 Cylindrical tanks designed to resist pressures of up to approx. 10 bar. The BOG can remain in the tank Simple tank arrangement Two types Double integry Full integry

46 Double integry pressure tank In case of a failure/leakage a pool / collection basin directing any spillages away in a safe location.

47 Full integrity pressure tank In case of a failure/leakage Both the inner and the outer containment are constructed from cryogenic steel being able to hold the LNG.

48 Example of LNG bunkering terminal From the semi-pressurised tanks: To truck or bunker/vessel

49 Bunker vessel Smaller and more manoeuvrable compared to an LNG feeder vessel Typical cargo capacity: m 3

50 Floating LNG Terminal (FSRU)

51 FSRU - Floating Storage and Regasification Unit m 3 membrane tanks Klaipeda

52 FRSU

53 Bunker vessel loading at FSRU

54 Chemical and physical properties fundamental for understanding and predicting LNG behaviour distinguish between the properties as a liquid and as a gas/vapour the properties which make LNG a good source of energy can also make it hazardous if not adequately contained properties, characteristics and behaviour of LNG differ significantly from conventional marine fuels

55 LNG s principal hazards result from its Cryogenic temperature Vapor expansion and dispersion characteristics Flammability characteristics If an LNG release occurs, there is an immediate potential for a range of different outcomes and types of consequences.

56 Chemical and physical properties Cryogenic liquefied gas Chemical composition Boiling point Density volume expansion Flammability

57 LNG is a cryogenic liquefied gas Gas: a fluid that is in gaseous form at normal pressure and ambient temperature Liquefied gas: a gas that has been turned into a liquid by cooling or compressing it Cryogenic liquefied gas: liquefies at a temperature below 150 C at atmospheric pressure.

58 How to liquefy a gas: Gas Compress: Increase pressure Liquid Cooling Vapour pressure (barg)

59 Common cryogenic liquefied gas Nitrogen (LIN) -196 C Oxygen (LOX) -183 C Helium (LHe) -269 C Hydrogen (LH2) -253 C Natural gas (LNG) -162 C

60 Typical chemical composition of LNG others: Ethane 4% Propane <1% Butane < 0.5% Nitrogen < 0.5%

61 Hydrocarbons in LNG Name of the hydrocarbon Number of carbons Boiling point atm. pressure Methane C Ethane 2-89 C Propane 3-42 C Butane 4 0 C Nitrogen: -196 C

62 Boiling point at atmospheric pressure water 100 C LNG -162 C Outside of storage tanks LNG quickly warms back into natural gas

63 Vapour pressure curve Higher pressure higher boiling point Gas Liquid LNG is always stored at the vapour pressure curve, thus at its boiling point! Vapour pressure (barg)

64 Density A liquid has a higher density than a gas/vapour! Liquid Gas

65 Volumetric expansion 1 m 3 LNG corresponds to around 600 m 3 natural gas The reason why natural gas is stored and transported as LNG A small leakage of LNG results in a large (flammable) gas cloud

66 Density LNG (liquid) Lower density than water, i.e. LNG floats on water But becomes a vapour pretty soon LNG: 450 kg/m 3 Water: 1000 kg/m 3

67 Density LNG vapour (natural gas) At temperature below -110 C: LNG vapour is heavier than air LNG vapour blankets the ground, the cloud travels with the wind At temperature above -110 C: LNG vapour is lighter than air LNG vapour will rise when sufficiently warmed by ambient air

68 How to recognize LNG (natural gas)? colourless and odourless The white clouds that forms at a leakage of LNG is not LNG/natural gas Cold LNG vapours will make the moisture in the air condense causing the formation of a white cloud (fog)

69 This is not a leakage of LNG The cold LNG pipe will make the air moisture to condense

70 What about flammability? Yes, natural gas burns - this is why it can serve as a fuel! LNG (liquid form) does NOT burn But, LNG begins vaporising immediately upon its release Flammability properties Flashpoint Flammability range Auto ignition temperature Minimum ignition energy

71 Flammability properites - summary ( ) ( ) LNG MDO/HFO Flammability range (in air) 5-15% 1-7.5% Flashpoint -187 C >60 C Auto ignition temperature 537 C C Minimum ignition energy in air 0.27 mj 20 mj To be continued