Saturday, March 19, 2016 Newport County, Rhode Island, USA MCA FCLC LNG Properties... · LNG ton of...

Copyright © 2016 United States Maritime Resource Center, Inc. All Rights Reserved. 1Copyright © 2016 United States Maritime Resource Center, Inc. All Rights Reserved. 1

Flammable Cryogenic Liquid Carriers

Thank You to the Seminar Sponsor

Seminar Provider and Host

Saturday, March 19, 2016

Newport County, Rhode Island, USA


Agenda & Topics

Morning 0830 - 1230

01 Introduction

02 LNG Properties and Characteristics

03 LNG Hazards

04 LNG Industry overview

Afternoon

1330 – 1630 Interactive Work Shop

05 LNG Fuel Vessel Design and Construction

06 Fuel Tanks and Fuel Supply Systems

07 Gas Atmosphere Control and Monitoring, Venting,

Inerting, unique repair hazards


02 Physical & Chemical Properties

Properties and Characteristics of LNG and natural gas

Pressure and Temperature, including vapor pressure / temperature relationship

Copyright © 2016 United States Maritime Resource Center, Inc. All Rights Reserved. 4

LNG Properties and Characteristics

• LNG is natural gas which has been converted to liquid form for ease of transport and storage

• LNG is composed of mostly methane, with ethane, propane, butane, pentane and other trace liquid gases

• When liquefied the natural gas volume is reduced by a factor of about 600 to 1

• LNG is odorless, colorless, non-corrosive, non-flammable, and non-toxic

• The properties that make LNG a good source of energy can also make it hazardous if not fully contained


Interactive Exercise

Refer to the LNG Safety Data Sheet:

• What is the boiling point of LNG?

• - 162°C (~- 160°C, varies with composition)

• What is the flashpoint of LNG?

• -187.8°C

• What is the specific gravity of LNG?

• 0.45 t/m3 (varies with composition)

• What are the flammable limits for LNG?

• 5%-15% (gas, by volume in air)

• What is the auto ignition temperature of LNG?

• 537°C

• What is the chemical formula for methane?

• CH4

• Based on the SDS, what are the primary hazards?

• Flammability, cryogenic hazard, asphyxiation


LNG Properties

Minimum ignition energy: < 1mJ

-162° C

-188° C

5% - 15%

537 ° C

Not much!

1.333 Bar

Lighter than air*


Composition of LNG

Chemical Chemical

Formula

Low High

Methane CH4 87% 99%

Ethane C2H6 <1% 10%

Propane C3H8 >1% 5%

Butane C4H10 >1% >1%

Nitrogen N2 0.1% 1%

Other

Hydrocarbons

Various Trace Trace


Cryogenic Liquids

• LNG boiling point ~ -160 °C (at

atmospheric pressure, depending on

composition)

• LNG is one of the “warmer”

cryogens

• Most materials become brittle at

cryogenic temperatures

•Steel

•Many plastics

•Rubber (i.e. gaskets)

•Skin

• Suitable materials for LNG service:

•Stainless Steel

•Nickel Steel (9% Ni, Invar,

etc.)

•Aluminum

• Common Cryogens

• Boiling Points:

• Ethane, -83.3 °C

• Ethylene, -104 ° C

• LNG (methane) -162 °C

• Oxygen, -183 ° C

• Argon, -186 ° C

• Nitrogen, -196 ° C

• Hydrogen, -253 ° C

• Helium, -269 ° C

Cryogenic fluids are gases that

have been liquefied by having

their temperature brought below –

150°C*

All cryogenic liquids are gases at normal temperatures and pressures.(http://www.ccohs.ca/oshanswers/prevention/cryogens.html)


LNG Characteristics

• Like all liquid fuels, LNG in it’s liquid state is not explosive and cannot burn

• In order to burn LNG must first be vaporized, mixed with air into the correct proportions and then ignited

• Vaporized LNG is NOT explosive. The flame speed is very slow

• (~ 6.4 kmh- the risk of unconfined Vapor Cloud Explosion is low

• Cold vapor is heavier than air and can form flammable mixtures in low / enclosed spots– venting consideration


Heat of Combustion

• LNG burns hot, which is why it’s such a great fuel…

But… The radiant heat of an LNG fire is a safety concern of government regulators , fire and safety officials, and the public.

Combustion of spilled LNG vapor clouds will involve combustion of “heavies”(propane, ethane and butane), adding uncertainty to thermal radiation calculations

Gasoline 2087°C

Methane 1950°C

Propane 1980 °C

Fuel Oil ( Diesel / IFO / HFO) 2100°C

Natural Gas 1960°C


LNG Energy Content

Energy Content:1 gal of Diesel = ~139,000 Btu1 Gal of LNG = ~ 82,000 Btu1 Diesel Gal Equivalent (DGE) = 1.7 [139,000btu/82,000Btu = 1.7DGE]

Energy Density:1 gal of LNG weighs 3.8 lb1 gal of diesel weighs 6.9 lb

Pound for pound, more energy in LNG:Diesel = ~20,145 Btu/lbLNG = 21,579 Btu / lb


Conversions and Equivalents

cubic

metre gas

cubic foot

gas

million Btu therm gigajoule kilowatt

hour

cubic metre of

LNG

ton of

LNG

1 cubic

meter

gas

1 35.3 0.036 0.36 0.038 10.54 0.00171 0.000725

1 cubic

foot gas0.0283 1 0.00102 0.0102 0.00108 0.299 0.00005 0.00002

1-million

Btu27.8 981 1 10 1.054 292.7 0.048 0.0192

1 therm2.78 98.1 0.1 1 0.105448 29.27 0.0048 0.00192

1

gigajoule26.3 930 0.95 9.5 1 277.5 0.045 0.018

1 kilowatt

hour0.0949 3.3 0.003415 0.03418 0.0036 1 0.000162 0.000065

1 cubic

meter

LNG

584 20 631 21.04 210.4 22.19 6,173 1 0.405

1 ton

LNG1,379 48 690 52 520 54.8 15 222 2.47 1

• The LNG Business is unit-challenged!


Conversions and Equivalent Units

• There’s an App for that!

• www.natgas.info, Chart, Air Products, DNV

• Available for iPhone and Android

http://www.natgas.info/


Boiling Point

• The Boiling Point of LNG is about -160°C (260ºF)

• LNG continuously warms due to contact with the warmer surrounding environment.

• The continuous boiling process presents challenges in the safe storage and containment of LNG

• Boiling produces LNG Vapor known as boil-off gas (BOG)

Heat In-leak

Boil-off

Vapor

Liquid


Boiling Point of LNG Components

• Common components of LNG boil at widely varying temperatures:

• Composition of LNG can change as it boils – if vented or consumed, it

“weathers”

• Components with the lowest boiling points, nitrogen and methane, will

evaporate first.

• Proportion of “heavies” increases as methane boils off

FuelBoiling

Point (oC)

Methane (Natural

Gas)-161.5

Ethane -89.0

Propane -42.0

IsoButane -11.7

n-Butane -1.0

IsoPentane 27.7

n-Pentane 36

n-Hexane 68


Rule 2:Don’t let LNG come in contact

with Air!

The flammable range for Methane in air is approximately 5% to 15%

Flammable Range


Density of LNG

•The density of LNG falls between 430 kg/m3 and 470 kg/m3

depending upon actual composition.

•LNG is less than half the density of water; therefore an LNG spill will

always float on water.

– Density of MDO: 890kg/m3


Relative Density of Methane Vapor

• Methane vapor is lighter than

air at temperatures above -

100°C

• This makes CH4 a relatively

safe gas to handle as leaks

will not create ‘puddles’ of

flammable vapor

• Operators must beware of

the potential for vented gas

to be heavier than air initially

• Significant during LNG

fueling, particularly in active

port areas

0.656 kg/m3 @ 25 °C, 1 atm

0.716 kg/m3 @ 0 °C, 1 atm


Understanding the ‘Gas Laws’

• All gases have 3 quantifiable characteristics:

•volume, temperature, and pressure, all of which may

change

• The Ideal Gas Law 𝑷𝑽 = 𝒏𝑹𝑻

explains the behavior of gases

when temperature, pressure

and volume are changing


• Boyle’s Law: for a fixed amount of gas at a fixed temperature, the pressure and volume are inversely proportional.

pV = constant

Vo

lum

e V

Pressure P

Pressure increase = Volume decrease

LNG Properties and Characteristics


• Charles’s Law says that for a fixed amount of gas at a fixed pressure, the volume is proportional to the temperature.

V/T = constant

Volume V

Tem

per

atu

re (

T)

Temperature increase = Volume increase

LNG Fuel Properties and Characteristics


• Gay-Lussac’s Law says that for a fixed amount of gas at a fixed volume, the pressure is proportional to the temperature.

Tem

per

atu

re T

Pressure P

Temperature increase = Pressure increase

LNG Fuel Properties and Characteristics

P/T = constant


Volume / Pressure / Temperature Relationship

About 600XLNGNatural

Gas

1. Fixed amount, fixed temperature:

Pressure increase = Volume decrease

2. Fixed amount, fixed pressure:

Temperature increase = Volume increase

3. Fixed amount, fixed volume:Temperature increase = Pressure increase


Saturated Vapor Pressure (SVP)

• Bubbles form and break through the

surface to occupy the space above as

vapor

• Some vapor molecules near the surface

re-condense to liquid

• Saturation pressure is the pressure at

which the liquid and vapor phase can

exist in equilibrium with each other at a

given temperature.

• As the pressure is increased so is the

saturation temperature, until the critical

point is reached

The pressure exerted by a saturated vapor at a particular temperature


Boiling Point vs Pressure

25


Temperature and Density


Weathering (aka “Ageing”):

• Boil-off process of LNG changes its composition

• Produces a liquid with a changing heating value and density, altering the value of the LNG


Critical Temperature and Pressure

● The temperature above which the substance cannot be liquefied however great the pressure

● The pressure at which a substance exists in the liquid state at its critical temperature.

● Equal to the saturation pressure at the critical temperature.

● It is the pressure required to compress a gas to its liquid state at its critical temperature

LNG Critical pressure: 44.7 Bar

LNG Critical Temp: -82.5 C

-82.5 °C (-117 F) 44.7 bar (648 PSI)


Knowledge Check

• What are the primary components of LNG?

• Methane Ethane Propane Butane Nitrogen

• What is the molecular structure of methane?

• 1 carbon atom and 4 hydrogen atoms

• Can the properties of LNG change over time?

• Yes- boil-off can change composition, heating value and density

• True or False? LNG burns hotter than conventional fuels

• False- gasoline, diesel, propane, HFO all burn hotter

• Define Saturated Vapor Pressure (SVP):

• Liquid phase and vapor phase are in equilibrium

• True or False? You need nearly 2 times more LNG fuel to get the same

amount of energy in diesel fuel

• True, LNG / diesel energy equivalent is 1.7x

29


End of Section

Questions?


References

CG –OES Policy Letter No. 01-15, GUIDELINES FOR LIQUEFIED NATURAL GAS FUEL TRANSFER OPERATIONS AND TRAINING OF PERSONNEL ON VESSELS USING NATURAL GAS AS FUEL, February 19, 2015

IMO MSC 285(86), Interim Guidelines on Safety for Natural Gas-Fuelled Engine Installations in Ships, 1 June 2009

CG-521 Policy Letter -1-12 DESIGN CRITERIA FOR NATURAL GAS SYSTEMS, April 19, 2012

IMO STCW.7 Circ 23, Interim Guidance on training for seafarers on board ships using gases or other low-flashpoint fuels

HTW 1/17 Development of the International Code of Safety for Ships Using Gases or Low-Flashpoint Fuels (IGF Code)

IMO CCC 1/13/Add.1., Annex 4, DRAFT INTERNATIONAL CODE OF SAFETY FOR SHIPS USING GASES OR OTHER LOW-FLASHPOINT FUELS (IGF CODE)

ISO TS 18683 Jan 2015, Guidelines for systems and installations for supply of LNG as fuel to ships


References (continued)

ISGOTT 5th Edition

SIGTTO Liquefied Gas Handling Principles on Ships and in Terminals , 3rd Edition 2000

SIGTTO LNG Drip Trays Guidance

SIGTTO Guidance for the Prevention of Rollover in LNG Ships Contents

SIGTTO LNG Transfer Arms and Manifold Draining, Purging and Disconnection Procedure

SIGTTO Use of Insulation Flanges (and Electrically Discontinuous Hoses) at the Ship/Shore and Ship/Ship Interface

ABS Guide for PROPULSION AND AUXILIARY SYSTEMS FOR GAS FUELED SHIPS (May 2011, updated February 2014)

ABS Bunkering of Liquefied Natural Gas-fueled Marine Vessels in North America 2ND EDITION

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