What is the specific gravity of LNG at 5 bar and -134 deg C?

In summary, a user is seeking help in calculating the specific gravity of a sample of LNG using a composition certificate and temperature and pressure variables. They have attempted to use the ideal gas equation but have not been successful. Another user suggests using density tables for LNG found in engineering handbooks as there are no theoretical equations for calculating the density of a liquid.
  • #1
nikcosmo
2
0
Hi Everyone...

I'm trying to calculate the specific gravity of a sample of LNG using a compostion certificate and temperature and pressure variables of 5 bar at -134 deg C saturated. Its do perform a check for the value used to calculate how much is charged per litre by converting density to litres. The density should be around 0.4 kg/m^3 but i can't seem to get a close answer to that using the ideal gas equation, pv = nrt.

Infor on composition certificate;
Gas composition;
Nitrogen ; 1.18%
Methane; 96.66%

Gas density at 15 deg C = 0.699 k/m^3
Ave MW = 16.487 g/mol

Can someone please help? thanks.
 
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  • #2
pV=nRT is and ideal GAS equation, LNG is a LIQUEFIED natural gas. You can't use theory that describes gaseous state to liquid state.

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  • #3
Any suggestions to which way i should approach it then? cheers.
 
  • #4
Only approach I can think of is to find density tables for LNG, engineering handbooks should have these. There are no theoretical equations that would allow calculation of density of a liquid (and even when such equations exist, they make heavy use of experimentally determined coefficients - so we are back to the handbook and tables).

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1. What is specific gravity and how is it measured?

Specific gravity is a measure of the density of a substance compared to the density of water. It is typically measured using a hydrometer, which is a device that measures the displacement of liquid caused by an object placed in it. The specific gravity of a substance is determined by dividing its density by the density of water.

2. How is specific gravity relevant to LNG?

Specific gravity is an important factor in determining the quality and composition of LNG (liquefied natural gas). It is used to measure the density of LNG, which can affect its energy content and performance. Specific gravity is also used to calculate the volume and mass of LNG, which is crucial in transportation and storage.

3. What is the typical specific gravity of LNG?

The specific gravity of LNG can vary depending on its composition and source, but on average it is around 0.45 to 0.55. This means that LNG is typically about half as dense as water.

4. How does temperature affect the specific gravity of LNG?

Temperature can significantly affect the specific gravity of LNG. As the temperature of LNG decreases, its specific gravity increases. This is because the density of LNG increases as it becomes colder and transitions from a gas to a liquid state. Therefore, accurate temperature control is crucial in measuring the specific gravity of LNG.

5. Why is it important to know the specific gravity of LNG?

The specific gravity of LNG is important for several reasons. It is used to determine the energy content and performance of LNG, which can affect its use in various applications. It is also necessary for calculating the volume and mass of LNG, which is crucial for transportation and storage. Additionally, specific gravity is a key factor in determining the quality and composition of LNG, which can impact its market value.

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