CHAPTER 1
INTRODUCTION
1.1 OVERVIEW
Liquefied Natural Gas LNG, which is produced from the natural gas via various cooling process to the temperature of -160
C at atmospheric pressure of 101kPaWang, 2009., The composition of LNG is similar to natural gas since LNG
is produced from natural gas. LNG is not a pure substance but formed by various hydrocarbons and non-hydrocarbon like methane, ethane, propane, butane, nitrogen,
carbon dioxide, and etcYounger, 2004. Typically, methane with chemical formula CH
4
exists with a high fraction within the natural gas if compared to other components but the composition of the natural gas can vary widely depend on the
gas sourceKastner, 2005.Table 1.1 show typical composition of natural gas which makeup from large volume of methane 85 along with the other component.
Different composition of LNG with respect to country is shows at Table 1.2. Bintulu, Malaysia produced highest percentage of methane91.2 among the other country
Table 1.1: Typical Composition of Natural Gas. Mokhatab, 2006. Name
Formula Volume
Methane CH
4
85 Ethane
C
2
H
6
3-8 Propane
C
3
H
8
1-2 Butane
C
4
H
10
1 Pentane
C
5
H
12
1 Carbon dioxide
CO
2
1-2 Hydrogen sulfide
H
2
S 1
Nitrogen N
2
1-5 Helium
He 0.5
Table 1.2: Composition of LNG in Different Terminal Locations Yang, 2003 Component
, mole Das
Island, Abu
Dhabi Whitnell
Bay, Australia
Bintulu, Malaysia
Arun, Indon
esia Lumut,
Brunei Bontang,
Indonesia Ras
Laffan, Qatar
Methane 87.1
87.8 91.2
89.2 89.4
90.60 89.6
Ethane 11.4
8.3 4.28
8.58 6.3
6.0 6.25
Propane 1.27
2.98 2.87
1.67 2.8
2.48 2.19
Butane 0.141
0.875 1.36
0.511 1.3
0.82 1.07
Pentane 0.001
- 0.01
0.02 -
0.01 0.04
The main objective introduction of LNG is to solve the problem of transportation and storage Bossier, 2011. Conventionally, natural gas is transmitted
to user from production plant by using insulated pipeline Thomas Dawe, 2003 and it is become a problem when there is a long distance transmission in term of
costing and unmanageable pipeline work. LNG with the liquid volume 600 times smaller than its corresponding original volume provided a strongpoint for ease of
storage and transportation by using tanker or ship Chandler et al, 2002. Figure 1.1 shows the comparison between natural gas, LNG and Compressed Natural Gas
CNG as well and the volume ratio of natural gas to LNG and CNG is 600:1:3.
During low period, LNG is stored at the isolated cryogenic storage tank at atmospheric pressure to serve the demand during peak periods Flynn, 2005.
Figure 1.1:The Comparison of Volume Between Natural Gas, LNG and CNG. Neptune, 2012
Recent year, due to liberalization of global gas market, it leads to the whole gas market under transition from long term rigid contract to sort term contract.
Besides that, diversification of LNG supply sources increase result in complicating reception terminal to handle and store the LNG inside separate tank according to its
source respectively. To deal with greater variety of incoming LNG, the storage tank at reception terminal must be fully utilized by mixing varies type of LNG inside one
tank to reduce costing and capital.Versluijs, 2010 The consequence of mixing varies LNG qualities inside a storage tank is density stratification and in the end lead
to serious safety concern named rollover.
1.2 PROBLEM STATEMENT
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