Liquified Natural Analysis 1

[arie2044]

HI Everybody
I'm looking for specifications of LNG and the description of chemical & Phisical test,specially on Measurment of Dew Point in this gas.

Thanks

 

[25362]

Quality specs. of a product may be defined as its fitness for a specific need or purpose that may differ from one application to another, the same applies to NG. Appropriate testing and analyses are generally covered by ASTM.

The principal quality criterion of natural gas is its heating value measured by ASTM D 1826-94(2003) or D3588-98(2003).

Since it should be readily transportable through high-pressure pipelines its water dew point, as measured by ASTM D 1142-95(2000), or water content by D 5454-93(1999), must be considered to prevent formation of hydrates.

Hydrocarbons heavier than ethane, as defined by the hydrocarbon dew point, should be considered to prevent accumulation of liquids that may block pipelines.

Its products of combustion must not be corrosive, thus detection of hydrogen sulfide by ASTM D 6228-98(2003), D-4323-84(2003), D 5504-01, D 6828-98(2003), D 6968-03, and total sulfur by ASTM D 1072-90(1999) are of importance. In some cases mercaptans can also be detected by ASTM D 2650-04 (gas chromatography).

Upon liquefaction of NG by cryogenic methods, carbon dioxide will separate out of the cold liquid and interfere with the refrigeration system. CO₂ can be determined by ASTM D 1945-96(2001) or D 2650-04.

A complete analysis by ASTM D 1945 (gas chromatography) must be made to be sure of the absence of deleterious materials when intended to be used as feedstock for the production of hydrogen.

 

[25362]

Mercaptans can be measured in the field by applying ASTM D-1988-21(2000)

 

[arie2044]

Hi 25362
Thank you for your answers, they help me very much.
do you know any company that sells instrument to measure hydrocarbons dew point.
Thanks again

 

[25362]

Arie2044

The dew point temperature depends on the selected pressure and viceversa.

1. If you know the composition of the gas you can estimate
it. This can be done by using computerized programs or
iterating (trial and error) by hand using K values (=
vap. press. at the selected temp.[÷]total system
pressure). Of course, you should fix the system pressure
to get the dew point temperature. If you need it I can
show you an example.

2. Otherwise, if you are interested in the dew point of a
stream of gas, without knowing its composition, use
instrumentation such as, for example, that
presented in the following site:

http://www.michell.co.uk/technology/pdf/Dark_spot_principle.pdf