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

  • Thread starter Thread starter nikcosmo
  • Start date Start date
  • Tags Tags
    Gravity Specific
Click For Summary

Discussion Overview

The discussion revolves around calculating the specific gravity of liquefied natural gas (LNG) at a pressure of 5 bar and a temperature of -134 degrees Celsius. Participants explore the implications of using the ideal gas equation for a liquid state and seek alternative methods for determining density.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Exploratory

Main Points Raised

  • One participant attempts to calculate the specific gravity of LNG using the ideal gas equation, noting a density value of around 0.4 kg/m^3 based on a composition certificate.
  • Another participant points out that the ideal gas equation is not applicable to LNG, as it is a liquefied gas, and suggests that theoretical models for gases cannot be used for liquids.
  • A third participant asks for suggestions on how to approach the calculation of density for LNG.
  • A later reply suggests consulting density tables for LNG found in engineering handbooks, indicating that theoretical equations for liquids often rely on experimentally determined coefficients.

Areas of Agreement / Disagreement

Participants generally agree that the ideal gas equation is not suitable for calculating the specific gravity of LNG in its liquid state. However, there is no consensus on the best approach to determine the density, with differing suggestions regarding the use of empirical data versus theoretical models.

Contextual Notes

The discussion highlights limitations in applying gas laws to liquids and the reliance on empirical data for accurate density calculations. Specific assumptions regarding the conditions of LNG and its composition are also noted but not resolved.

nikcosmo
Messages
2
Reaction score
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.
 
Physics news on Phys.org
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.

--
 
Any suggestions to which way i should approach it then? cheers.
 
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).

--