i

THE STUDY OF INTERCHANGEABILITY IN LIQUEFIED NATURAL GAS

(LNG) IN COMPARISON TO OTHER FUELS

DEIRDRE ANAK JAMES DAMU

A thesis submitted in fulfillment

of the requirements for the award of the degree of

Bachelor of Chemical Engineering (Gas Technology)

Faculty of Chemical & Natural Resources Engineering

Universiti Malaysia Pahang

December 2010

v

ABSTRACT

Natural gas interchangeability is the key subject in the industry today and most recently

Liquefied Natural Gas (LNG) has emerged as a major source and differs substantially

from domestically produced gas. Interchangeability means the characteristics of a design

that allow direct placement of one item without requiring any modification. This

research was a challenge, as it is difficult to find the suitable equipment and available

equipment in the lab is limited to a lab scale only as the objective is to investigate to

what degree LNG in its gaseous form is interchangeable and to show Wobbe Index (WI)

is a measure of the fuel interchangeability. From the research that has been conducted,

the key parameters used to investigate the interchangeability of a fuel gas WI, Calorific

Value (CV), Air Fuel Ratio (A/F) and CARI (Combustion Air Requirement). This

research is conducted by experiment, studying the methane as LNG and LPG (at

different composition) using Boys calorimeter to find the CV and WI. Then, the Flame

Propagation and Stability Unit are used to measure each fuel gases A/F and CARI index.

As expected, the result showed that LNG has higher WI value that is 304.787 Btu/Ft3

when compared to LPG with the value of 238.08 Btu/Ft3, followed with Propane with

the value 228.51 Btu/Ft3 and Butane with the value of WI 210.816 Btu/Ft

3. As a

conclusion, LNG has much better characteristics in interchangeability factor and higher

heating value meaning higher Wobbe Index which is better performance in terms of

interchangeability when compared to other fuel. It is safe to say LNG provides higher

energy to the burner and provides much efficient as well as safer combustion process.

The accuracy and the efficiency of this research could be improved by using a metered

or digitalizing the Boy’s Calorimeter and well as customizing the flame properties for

the flame propagation and stability unit at a constant flame color and rate.

vi

ABSTRAK

Kebolehsalingtukaran gas asli ialah subjek utama dalam industri hari ini dan Liquefied

Natural Gas (LNG) muncul sebagai satu sumber utama dan berbeza dari gas yang

dihasilkan secara domestik. Kebolehsalingtukaran bererti ciri-ciri satu rekaan yang

membenarkan pengantian alatan tanpa memerlukan sebarang pengubahsuaian.

Penyelidikan ini merupakan satu cabaran, kerana ia agak sukar untuk mencari alat yang

sesuai dan peralatan yang sedia ada dalam makmal terhad kepada skala makmal kerana

objektif penyelidikan ini ialah untuk menyiasat darjah LNG dalam bentuk gasnya

mampu saling bertukar dan menunjukkan Wobbe Index (WI) ialah satu langkah

kebolehsalingtukaran bahan api. Dari kajian, parameter utama yang digunakan untuk

menyiasat pertukaran dari bahan bakar gas adalah WI, Nilai Kalori (CV), Air Fuel Ratio

(A / F) dan CARI (Keperluan Pembakaran Udara). Penyelidikan ini dilakukan melalui

percubaan, mempelajari metana sebagai LNG dan LPG (pada komposisi yang berbeza)

menggunakan kalorimeter Boys untuk mencari CV dan WI. Kemudian,Unit propagasi

api dan kestabilan digunakan untuk mengukur bahan bakar bagi setiap gas untuk A/F

dan indeks CARI. Seperti yang diharapkan, hasilnya menunjukkan bahawa LNG

mempunyai WI nilai yang lebih tinggi iaitu 304,787 Btu/Ft3 bila dibandingkan ke LPG

dengan nilai 238,08 Btu/Ft3, diikuti dengan Propane dengan 228,51 Btu/Ft

3 nilai dan

Butana dengan nilai 210,816 Btu WI/ ft3.Sebagai kesimpulan, LNG mempunyai ciri-ciri

yang jauh lebih baik dalam faktor saling pertukaran dan nilai pemanasan yang lebih

tinggi bermakna lebih tinggi Indeks Wobbe yang prestasi yang lebih baik bila

dibandingkan dengan bahan bakar yang lain. Adalah selamat untuk dikatakan, LNG

memberikan lebih tenaga dan lebih cekap serta selamat. Ketepatan dan kecekapan kajian

ini dapat dipertingkatkan dengan menggunakan kilometer Boy’s yang bermeter atau

berbentuk digital dan juga mengubah sifat api untuk unit propagasi api dan kestabilan

pada warna nyalaan konstan dan stabil.

vii

TABLE OF CONTENTS

Page

TITLE PAGE i

SUPERVISOR’S DECLARATION ii

STUDENT’S DECLARATION iii

ACKNOWLEDGEMENTS iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES x

LIST OF FIGURES xi

LIST OF ABBREVIATIONS xii

LIST OF SYMBOLS xv

APPENDICES xvi

CHAPTER 1 INTRODUCTION

1.1 Background of study 1

1.1.1 Liquefied Natural Gas (LNG) Industry in Malaysia 4

1.2 Problem Statement 4

1.3 Objectives 5

1.4 Scope of Study ` 5

1.5 Rationale and Significance 5

viii

CHAPTER 2 LITERATURE REVIEW

2.1 Liquefied Natural Gas (LNG) 6

2.1.1 Liquefied Natural Gas (LNG) Composition 6

2.1.2 Boling Point of Liquefied Natural Gas (LNG)

2.1.3 Density and Specific Gravity of Liquefied Natural Gas (LNG) 9

2.1.4 Flammability Limit of Liquefied Natural Gas (LNG) 12

2.1.5 Ignition and Flame Temperature of Liquefied Natural Gas (LNG) 14

2.2 Key Parameter for Interchangeability 16

2.2.1 Calorific Value (CV) 16

2.2.2 Wobbe Index (WI) 17

2.2.3 Stoichiometric Air to Fuel Ratio 18

2.2.4 Combustion Air Requirement Index (CARI) 19

2.3 Comparison of Liquefied Natural Gas (LNG) with Other Fuels 21

CHAPTER 3 METHODOLOGY 23

3.1 Gases used for Interchangeability Test 23

3.1.1 Properties of the Fuel Gases 23

3.2 Parameters Selected for Interchangeability Test 24

3.3 Equipment for this Research 25

3.3.1 Experimental Procedures using Boy’s Calorimeter 25

3.3.2 Experimental procedures using Flame Propagation and Stability

Unit 26

3.3.2.1 General Start – Up Procedure 27

3.3.2.2 General Shut – Down Procedure 27

3.3.2.3 Flame Propagation Test 27

3.4 Overall Methodology for this Research 28

ix

CHAPTER 4 RESULT AND DISCUSSION 30

4.1 Calculation for Calorific Value (CV) 30

4.1.1 LPG (70 % Propane & 30 % Butane) 31

4.1.2 Purified Methane as LNG (99.5% purity) 34

4.1.3 LPG with Propane (96.0 % purity) 37

4.1.4 LPG with Butane (96.0 % purity) 40

4.1.5 Comparison and Discussion for Calorific Value for each sample

fuel gases 43

4.2 Wobbe Index (WI) 43

4.2.1 Sample 1 LPG Tank (70% Propane & 30% Butane) 44

4.2.2 Sample 2 LNG (99.5% pure methane) 46

4.2.3 Sample 3 LPG (96% pure Propane) 48

4.2.4 Sample 4 LNG (96% pure Butane) 50

4.2.5 Comparison and Discussion of Wobbe Index for each sample Gas 52

4.3 Combustion Air Requirement Index (CARI) 53

4.3.1 CARI for LPG 53

4.3.2 CARI for Methane as LNG 54

4.3.3 CARI for LPG as Propane 54

4.3.4 CARI for LPG as Butane 54

4.4.5 Relationship between Air to Fuel Ratio & CARI (Combustion

Air Requirement Index) for each fuel gas 55

CHAPTER 5 CONCLUSION AND RECOMMENDATION 57

5.1 Conclusion 57

5.2 Recommendation 58

REFERENCES 59

x

APPENDICES

A Table 1: Gas Volume Factors relative to 0"C and 760 mmHg. 63

B Table 2: Gas Volume Factors relative to 0"C and 760 mmHg. 64

C Table 3: Meter Gas Rates & Water Collection Rates 65

D Data for LPG (Liquefied Natural Gas / 70% Propane &30 %

Butane) 66

E Data for Methane (99.5%) 67

F Data for Propane (96%) 68

G Data forButane (96%) 69

H Formula for calorific value, CV (MJ/m3) 70

I Data for LPG (Liquefied Petroleum Gas/ 70% Propane & 30%

Butane) 71

J Formula for Air to Fuel Ratio 72

K Data for Methane (99.5%) 73

L Data for Propane (96%) 74

M Data for Butane (96%) 75

N The Flame Propagation and Stability Unit 76

O Flame Propagation and Stability Unit Panel 77

P The fuel gas flame at stable condition 78

Q The blue flame indicates the flame is propagating through the tube 79

R Propane and Butane Gas Tank 80

xiii

LIST OF TABLES

TABLE NO TITLE PAGE

2.1 Typical chemical composition of LNG 7

2.2 Boiling Points of water and some common gases. 9

2.3 Flammability limits of hydrocarbon fuels. 14

2.4 Auto-ignition temperature of some fuels at standard

conditions. 15

2.5 Air to Fuel Ratio Requirement for the combustion of selected

alkanes 19

2.6 Advantages and disadvantages of Liquefied Natural Gas (LNG)

compared to Gasoline, Liquefied Petroleum Gas (LPG) and

Methanol 21

3.1 Properties of fuel gases used in the research. 23

3.2 Indicator on Flame Propagation and Stability Unit. 26

4.1 Temperature of the inlet and outlet inside Boy’s Calorimeter. 30

4.2 Mass of water collected for each reading 30

4.3 Temperature of inlet and outlet inside Boy’s Calorimeter 33

4.4 Mass of water collected for each reading 33

4.5 Temperature of inlet and outlet inside Boy’s Calorimeter 36

4.6 Mass of water collected for each reading 36

4.7 Temperature of inlet and outlet inside Boy’s Calorimeter 39

4.8 Mass of water collected for each reading 39

4.9 Calorific Value for each data of LPG 44

4.10 Calorific Value for each data of Methane 45

4.11 Calorific Value for each data of Propane 47

4.12 Calorific Value for each data of Butane 49

xiv

xv

LIST OF FIGURES

FIGURE NO TITLE PAGE

1.1 Typical LNG composition. 2

1.2 Liquefied Natural Gas Production and Refueling Options. 3

2.1 LNG “boiling” at atmospheric pressure and temperature. 8

2.2 LNG vapor cloud created for training at Texas A & M in the

LNG Live Fire Training Workshop. 10

2.3 The fire triangle. 13

2.4 Flammability range for methane 13

3.1 Flame Propagation and Stability Unit 26

3.2 Flowchart of overall methodology 28

4.1 Graph for the Calorific Value, CV (MJ/m3) versus run for each

Gas 42

4.2 Graph of Wobbe Index, WI (Btu/Ft3) versus run of each fuel

Gases 51

4.3 Graph of Relationship between Air to Fuel Ratio and CARI for

each gases. 54

xvi

LIST OF ABBREVIATIONS

A/F : Air to Fuel Ratio

Btu : British thermal unit

Btu/lb : Pound per British thermal unit

Btu/Ft3 : Cubic foot per British thermal unit

C : Carbon

CARI : Combustion Air Requirement Index

CH4 : Methane

C2H6 : Ethane

C2H8 : Propane

C4H10 : Butane

C5H12 : Pentane

C6H14 : Hexane

C7H16 : Heptane

C8H18 : Octane

CO : Carbon Monoxide

CO2 : Carbon Dioxide

CV : Calorific Value

F : Fahrenheit

GVF : Gas Volume Factor

xvii

H : Hydrogen

H2O : Water

HGV : Heavy Good Vehicles

lb /US gal : Pound per gallon

LNG : Liquefied Natural Gas.

LPG : Liquefied Petroleum Gas.

LFL : Lower Flammability Limit.

M – 85 : Methanol

m2 :

Meter square

m3 : meter cubic

MJ/kg : Mega joule per kilogram

MJ/m3 : Mega joule per meter cubic

mL : milliliter

Nm3 :

Newton meter cube

NOx : Nitrogen Oxide

O2 : Oxygen

Kg /m3 :

kilogram per meter cube

N2 : Nitrogen

Revs : Revolution

UFL : Upper Flammability Limit.

US : United States

xviii

W : Weight

WI : Wobbe Index

xix

LIST OF SYMBOLS

°C : Celsius

ΔT : Temperature difference

1

CHAPTER 1

INTRODUCTION

1.1 BACKGROUND OF STUDY

Liquefied natural gas (LNG) is natural gas (predominantly methane, CH4) that

has been converted temporarily to liquid form for ease of storage or transport. The main

advantage of liquefaction process is the reduction by about 600 times of the total volume

required for natural gas storage and transportation (Rafael Rosal et al., 2008). It is

odorless, colorless, non-toxic and non-corrosive. Hazards include flammability, freezing

and asphyxia. The liquefaction process involves removal of certain components, such as

dust, acid gases, helium, water, and heavy hydrocarbons, which could cause difficulty

downstream. The natural gas is then condensed into a liquid at close to atmospheric

pressure (maximum transport pressure set at around 25kPa or 3.6psi) by cooling it to

approximately −162°C (−260 F). The reduction in volume makes it much more cost

efficient to transport over long distances where pipelines do not exist. Where moving

natural gas by pipelines is not possible or economical, it can be transported by specially

designed cryogenic sea vessels (LNG carriers) or cryogenic road tankers. Figure 1 shows

the typical LNG composition.

2

Figure 1.1: Typical LNG Composition

(Source: Center for Energy Economics, et al., 2007)

Natural Gas liquefaction dates back to the 19th

century when British Chemist and

Physicist Michael Faraday experimented with liquefying different types of gases

including natural gas. German engineer Karl Von Linde built the first practical

compressor refrigeration machine in Munich in 1873. The first NG plant was built in

West Virginia in 1912 and began operation in 1917. The first commercial liquefaction

plant was built in Cleveland, Ohio, in 1941. The LNG was stored in tanks at atmospheric

pressure.

The liquefaction of natural gas raised the possibility of its transportation to

distant destinations. In January 1959, the world’s first LNG tanker, The Methane

Pioneer, a converted World War II liberty freighter containing five, 7000 barrel

equivalent aluminum prismatic tanks with balsa wood supports and insulation of

plywood and urethane, carried in LNG cargo from Lake Charles, Louisiana to Canvey

Island, United Kingdom. This event demonstrated that large quantities of liquefied

natural gas could be transported safely across the ocean (Michelle Michot Foss, 2007).

Figure 2 shows the liquefied natural gas production and refueling option diagram.

3

Figure 1.2: Liquefied Natural Gas Production and Refueling Options

(Source: Wegrzyn, J, et.al., 1998)

The LNG must be stored and transported permanently at around this temperature

and this is accomplished by super insulation in a pressurized, double tank system,

similar in principle to a thermos flask, together with a venting system to take away

vapor. The storage pressure of about 8 bar (8 x atmospheric) is not regarded as very high

but because of the insulation requirements the tanks are large, the fuel is only suited to

large, heavy diesel vehicles such as trucks, buses and HGV’s (Envocare et al., 2007).

LNG is the liquid form of natural gas people use in their homes for cooking and heating.

Natural gas is also used as fuel for generating electricity. Natural gas and its component

are used as raw material to manufacture a wide variety of products, from fibers for

clothing, to plastics for healthcare, computing and furnishing (Center for Energy

Economics et al., 2007).

4

1.1.1 LNG Industry in Malaysia

Malaysia LNG operates the world’s largest LNG production facility in a single

location; it has eight production units in three integrated plants and a total production

capacity of 23 million tons per year. The country is the world’s third largest exporter of

LNG. Malaysia LNG is keen to maintain its position as a world-class operator and

embarked on a project to review and improve its energy usage in 2005 (Shell Global

Solution).

LNG is simply a natural gas that has been treated to remove impurities, and then

condensed to a liquid form. The unique economics of the LNG industry usually dictate

that heavier ethane-plus components are not removed down to the levels commonly

found in US domestic pipeline gas. At the same time, LNGs usually contain little or no

carbon dioxide or nitrogen both commonly present in domestic natural gases (Gas

Technology Institute et al., 2003).The benefits of LNG include low pressure storage and

greater energy density per volume. As a result LNG has the greatest potential for

medium-heavy duty applications where users require low-cost, low-weight fuel storage

options with increased driving range.

1.2 PROBLEM STATEMENT

The limitation in this research are, first, is to find out what are the other

equipment that are available in the gas engineering lab to conduct the interchangeability

test that are done mostly with big or industrial scale equipment. Second, the research is

to compare the interchangeability of Liquefied Natural Gas, LNG (99.5% of purity) with

Liquefied Petroleum Gas (LPG) at different composition (pure propane 96% purity, pure

butane 96% and the composition of 70% propane and 30% butane). The next problem is

to find out what is the basic parameter can used in measuring interchangeability of the

fuel.

5

1.3 OBJECTIVES

The objective of this project is to investigate to what degree LNG in its gaseous

form is interchangeable or compatible with existing utilization equipment. The next

objective is to run, analyze different kind of fuel for different kind criteria of the fuel

experimentally. Then, the physical terms of LNG and LPG is compared. Lastly, the

objective is to show Wobbe index is a measure of the fuel interchangeability with

respect to its energy content and metered air fuel ratio (A/F ratio).

1.4 SCOPE OF STUDY

The scope of study in this research is to investigate experimentally the alternate

ways to find the key parameter that can be used to measure the interchangeability of

LNG and LPG. In the industry, most of the interchangeability test is conducted using

industrial scale equipment such as gas turbine and knock engines, and the equipment

available in the laboratory is limited only to the industrial scale unit, so we are to find

what are the equipment available for the research.

1.5 RATIONALE AND SIGNIFICANCE

This research is conducted to determine interchangeability of LNG to other

conventional fuel and to find out experimentally whether LNG is efficient, cleaner, safer

and economical in the performance value.

6

CHAPTER 2

LITERATURE REVIEW

2.1 LIQUEFIED NATURAL GAS (LNG)

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

or transport. LNG takes up about 1/600th

of the volume of natural gas. Depending upon

its exact composition, natural gas becomes a liquid at approximately -162°C (-259°F) at

atmospheric pressure. LNG‟s extremely low temperature makes it a cryogenic liquid.

Generally, substances which are -100°C (-48°F) or less are considered cryogenic and

involve special technologies for handling. In comparison, the coldest recorded natural

temperatures on earth are -89.4°C (-129°F) at the height of winter in Antarctica and the

coldest reported temperature in a town was recorded in Oymayakon (Sakha Republic)

during Siberian winter (-71.2°C; -96.16°F). To remain a liquid, LNG must be kept in

containers which function like thermos bottles they keep the cold in and the heat out.

The cryogenic temperature of LNG means it will freeze any tissue (plant or animal)

upon contact and can cause other materials to become brittle and lose their strength or

functionality. This is why the selection of materials used to contain LNG is so important.

2.1.1 Chemical Composition of LNG

Natural gas is a fossil fuel, meaning it has been created by organic material

deposited and buried in the earth millions of years ago. Crude oil and natural gas

constitute types of fossil fuel known as “hydrocarbons” because these fuels contain

chemical combinations of hydrogen and carbon atoms. The chemical composition of

7

natural gas is a function of the gas source and type of processing. It is a mixture of

methane, ethane, propane and butane with small amounts of heavier hydrocarbons and

some impurities, notably nitrogen and complex sulphur compounds, water, carbon

dioxide and hydrogen sulphide which may exist in the feed gas but are removed before

liquefaction. Methane is by far the major component, usually, though not always, over

85% by volume. Table 2.1 displays the chemical compositions of the hydrocarbon

compounds which make up natural gas, and the volume ranges in which they may be

present in LNG. Pipeline natural gas may contain small amounts of water vapor.

Table 2.1: Typical chemical 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

(Source: Center for Energy Economics)

2.1.2 Boling Point of Liquefied Natural Gas (LNG)

The boiling point of LNG varies with its basic composition, but typically is -

162°C (-259°F).

8

Figure 2.1: LNG “boiling” at atmospheric pressure and temperature.

(Source: Osaka Gas Co. Ltd)

When cold LNG comes in contact with warmer air, water, or the environment, it

begins to “boil” at that interface because the surrounding temperatures are warmer than

the LNG‟s boiling point, as shown in Figure 2.1. Table 2.2 shows the boiling points of

water and common gases.

9

Table 2.2: Boiling points of water and some common gases.

Fahrenheit(°F) Celsius (°C) Occurrence

212 100 Water Boils

31 -0.5 Butane Boils

-27 -33 Ammonia Boils

-44 -42 Propane Boils

-259 -162 LNG Boils

-298 -183 Oxygen Boils

-319 -195 Nitrogen Boils

-422 -252 Hydrogen Boils

-454 -270 Helium Boils

-460 -273 Absolute Zero

(Source: Adapted from the Engineering Toolbox)

Note: Absolute zero is the coldest temperature theoretically possible, and cannot be

reached by artificial or natural means. By international agreement, absolute zero is

defined as precisely 0 K on the Kelvin scale and is equivalent to -273.15°C/-459.67°F.

2.1.3 Density and Specific Gravity of Liquefied Natural Gas (LNG)

Density is a measurement of mass per unit of volume and is an absolute quantity.

Because LNG is not a pure substance, the density of LNG varies slightly with its actual

composition. The density of LNG falls between 430 kg/m3 and 470 kg/m3 (3.5 to 4

lb/US gal). LNG is less than half the density of water; therefore, as a liquid, LNG will

float if spilled on water.

Specific gravity is a relative quantity. The specific gravity of a liquid is the ratio

of density of that liquid to density of water (at 15.6°C/60°F). The specific gravity of a

gas is the ratio of the density of that gas to the density of air (at 15.6°C). Any gas with a

10

specific gravity of less than 1.0 is lighter than air (buoyant). When specific gravity or

relative density is significantly less than air, a gas will easily disperse in open or well-

ventilated areas. On the other hand, any gas with a specific gravity of greater than 1.0 is

heavier than air (negatively buoyant). The specific gravity of methane at ambient

temperature is 0.554; therefore it is lighter than air and buoyant.

Under ambient conditions, LNG will become a vapor because there is no place

on earth with a temperature of -162°C (-259°F). As LNG vaporizes, the cold vapors will

condense the moisture in the air, often causing the formation of a white vapor cloud until

the gas warms, dilutes, and disperses as shown in Figure 2.2.

Figure 2.2: LNG vapor cloud created for training at Texas A & M in the LNG Live Fire

Training Workshop, 2005

(Source: Photograph by A.H. Walker)

For a relative humidity higher than 55%, the flammable cloud is totally included

in the visible vapor cloud. If the relative humidity is less than 55%, the flammable cloud

can be partially or completely outside of the visible cloud, which means that the vapors

11

could be ignited even though the ignition source is distant from the visible vapor cloud.

The size of the vapor cloud will depend on wind speed, direction, and other weather

conditions and can easily be predicted by the appropriate related calculations. These

very cold vapors will rise as they are sufficiently warmed by ambient air.

LNG vapors at the boiling point temperature (-162°C/ -259°F) and atmospheric

pressure have a relative density of about 1.8, which means that when initially released,

the LNG vapors are heavier than air and will remain near the ground. However as

methane vapors begin to rapidly warm and reach temperatures of approximately -

110°C/-166°F, the relative density of the natural gas will become less than 1 and the

vapors become buoyant.

At ambient temperatures, natural gas has a specific gravity of about 0.6, which

means that natural gas vapors are much lighter than air and will rise quickly. Cold LNG

vapors (below -110°C/-166°F) are negatively buoyant and more likely to accumulate in

low areas until the vapors warm. Therefore, a release of LNG that occurs in an enclosed

space or low spot will tend to replace the air (and oxygen) and make the area a hazard

for breathing.

The rate of LNG vapor ascent depends upon the quantity of LNG released,

ambient weather conditions, and where the LNG is released, e.g., confined or

unconfined, low or elevated area, on land or on water. One strategy to manage the

vapors is to create a downwind water curtain which helps block and/or divert the vapors

away from possible ignition sources until the vapors warm and become buoyant, and/or

dilute to a lesser concentration outside the flammable limits, which are discussed in the

next section.

Heat input to LNG in any form will enhance vaporization and dispersion. Such

heat may be transferred from passive sources such as atmospheric humidity (which is a

significant source), the ground or spill catchment areas, impoundments, pits and

structures. LNG vaporizes five times more quickly on water than on land, depending