Calculation of LNG density
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I have a question! Does that expert know what the density of LNG at -163 degrees Celsius is? Is there a formula for calculating its density? Please give me some advice!
I have a question! Does that expert know what the density of LNG at -163 degrees Celsius is? Is there a formula for calculating its density? Please give me some advice! One more thing to add: the methane concentration is 97-98%.
It’s not enough to just know the methane content – is it the volume concentration, or the mass concentration, or the mole percentage? Just ask a friend to use HYSYS to do it; it’s very simple.
The density of LNG mainly depends on its composition, typically ranging from 430 to 470 kg/m3; the higher the methane content, the lower the density； Additionally, density is also a function of temperature; the higher the temperature, the lower the density, with a rate of change of 1.35 kg/(m3·℃). There are two methods to determine the density of LNG: (1) direct measurement, and (2) calculation based on the component results from gas chromatography analysis. This is the most commonly used method. By taking advantage of methane’s ability to absorb infrared light waves, it is possible to accurately measure its density. The testing principle involves emitting two types of radiation alternately: one is a light wavelength of 1A that methane can absorb ； Another type is light that methane cannot absorb, with a wavelength of 2A, but this light can pass through the gas. Since only 1A rays can be absorbed by methane, by measuring the intensity difference between 1A and 2A rays, the density of methane can be calculated. This testing method has the following advantages: ① Rays are not a source of ignition, thus allowing for the safe measurement of the density of flammable gases ； ②Methane can absorb infrared radiation, while the presence of other gases has almost no effect; therefore, the measurements are accurate with a precision of up to 0.1% ； ③By changing the wavelength of the radiation source oscillation, the density of other gases can be measured.
The volume of LNG is about 1/600 of that of an equal amount of gaseous natural gas, and its weight is only around 45% of that of water with the same volume; thus, its density is approximately 450 kg/m3.