Introduction: What is LNG?
 When natural gas is cooled to a temperature of
approximate (–160 C) at atmospheric pressure it
condenses to a liquid ,called (LNG).
• The liquefaction process reduces the original volume of the
natural gas(≈1/600).
• The density of LNG is less than half that of water, (≈ 45% ).
• Odorless.
• Colorless.
• non-corrosive.
• non-toxic.
• When vaporized, it burns only in concentrations of 5% to 15%.
LNG is a safe and efficient way to transport gas
across long distances.
1917 First commercial natural gas liquefaction plant built
in
West Virginia.
1959 The world's first LNG tanker, safely carries LNG from
Lake Charles, LA., to Canvey Island, United Kingdom,
initiating commercial LNG shipping.
1964 The British Gas Council begins importing LNG from
Algeria, making the United Kingdom the world's first LNG
importer and Algeria as its first exporter.
1969 United States exports LNG to Asia for the first time:
from Alaska to Japan.
The LNG process removes the oxygen, carbon dioxide,
sulfur compounds, and water.
 Black & Veatch developed a single mixed refrigerant
loop .called the PRICO Process.
 The PRICO process is the only LNG process with
proven installations in a wide capacity range.
 The capacity of the PRICO process is limited to
about 1/3 of the APCI or Phillips process units
presently being constructed.
Simplicity & Operation Reliability
Operating Flexibility
Rapid Startup
 This refrigerant is a mixture of nitrogen hydrocarbons
,ranging from methane to isopentane.
 Utilization of SMR greatly simplifies the piping, controls,
and equipment arrangements
 The use of a single refrigeration system is the key aspect
of a simple and reliable LNG plant.
 The use of a single exchanger for the LNG production is
another key to process simplicity.
 Fluctuations of feed gas composition ,pressure and
changes in ambient conditions have minor impact on the
system.
Equipment:
a main heat exchanger
a compressor
a condenser
two Joule-Thomson (JT)
valves
The process cools the natural gas feed
from ambient conditions to gas liquefaction
temperatures and then further cools the gas
to minimize vaporization when sending the
LNG to atmospheric storage tanks.
• The refrigerant is partially condensed in the condenser
and is fed to the NG HX and is cooled together with the
natural gas stream.
• The refrigerant is a sub-cooled liquid at the outlet of NG
HX and is expanded to the low pressure (Pl). The
resulting two-phase mixture provides the cooling in NG
HX by vaporization.
• The outlet from the heat exchanger (NG HX) is slightly
super-heated, partly to avoid damage to the compressor.
Prico process optimization
The Prico process was selected for optimization :
 First, it is a simple LNG process with 7 independent
variable.
 Second, it is possible to verify the results by
investigating the resulting hot and cold Composite
Curves (CCs).
•
the flow rate and
composition of the
refrigerant
•
the compressor suction
pressure (low pressure)
• the condenser pressure
(high pressure).
Prico process optimization:
 The two most important unit operations in an LNG process:
 Compressors
 Heat exchangers
Degeneration of energy:
Parameters and variables in Prico process:
Composite curves for the initial solution:
Composite curves for case 1:
Composite curves for case 2:
..\simulation.avi
..\optimization.avi
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