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LNG Basics: Understanding Its Typical Properties

For those who starts working with LNG, I recommend to read BS EN 1160 – Installations and equipment for liquefied natural gas – general characteristics of liquefied natural gas. The standard covers almost all LNG characteristics that you need to know, such as properties of LNG, evaporation of LNG, spillage, ignition, containment, and other physical phenomena. I think it will be nice to share some of them in this post.

There are three things at least you need to know about LNG before knowing other things.

lng-basic-properties
lng-basic-properties

To compare how cold LNG is compared to other components, please see illustration below.

Boiling Point of Several Component
Boiling Point of Several Component at Atmospheric Temperature (in deg C)

Composition

Typical LNG composition is shown in below illustration.

Typical LNG Composition
Typical LNG Composition

 

Density

LNG density is function of composition, but usually ranges from 430 kg/m3 to 470 kg/m3. Density is also a function of temperature with a gradient of about 1.35 kg/m3 deg. I wonder if this rule of thumb is true. Let’s check!

Figure below illustrate LNG composition from two different sources, namely from location A (orange) and location B (blue) at atmospheric pressure. The composition is actually real composition.

LNG Mass Density as A Function of Temperature
LNG Mass Density as A Function of Temperature

We can see that different composition gives different gradient mass density. Maybe basis of LNG composition used in EN 1160 is rich LNG which have less than 85% of methane composition.

Temperature

LNG is boiling at temperature ranges from -166 deg C to -157 deg C at atmospheric pressure. Again, it is actually a function of composition. EN 1160 states that variation of boiling temperature with the vapor pressure is about 0.000125 deg C/Pa.

LNG Boiling Temperature as a Function of Vapor Pressure
LNG Boiling Temperature as a Function of Vapor Pressure

In my case gradient for LNG boiling temperature as a function of pressure is about 0.000034 deg C/Pa.

Different LNG properties, such as spillage, containment, and other phenomena will be shared in next post. Please be patient ;).

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