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 The world's first LNG tanker, safely carries LNG from Lake Charles, LA., to Canvey Island, United Kingdom, initiating commercial LNG shipping 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 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.

a main heat exchanger a compressor a condenser two Joule-Thomson (JT) valves Equipment:

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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