C6+ characterization for natural gas
C6+ characterization for natural gas
(OP)
on our lines we have gas chromatograps measuring C1-C6 , the software calculates Cricondentherm, Wobbe, Dew Points etc. splitting C6+ in two fractions (according AGA method), our client (with their simulator and compositions from laboratory analysis) calculates different results (6-10 F in dew points), a chilled mirror returns intermediate values but closer to client's results. We had a long discussion about the procedure to use and there was no agreement, which is the usual practice ?





RE: C6+ characterization for natural gas
When detailed laboratory analysis is available a common practice is to input those data in software package
www.prode.com/docs/proind.pdf
however, as no one knows what happens between two successive laboratory measurements the calculated values may be unreliable.
Apart from this a software package offers the advantage to calculate a large number of different properties with great accuracy.
a suitable equation of state (Peng Robinson, Soave Redlich Kwong , GERG or others) can calculate very accurate VLE values, for hydrocarbon mixtures typical errors are whithin 1-2 C of measured values.
For values as density AGA or GERG again are very accurate (typical errors < 0.3%).
But of course you must find a way to define the correct composition.
RE: C6+ characterization for natural gas
The two questions that you have to ask are: (1) What does the sales contract say? and (2) is the difference material?
David
RE: C6+ characterization for natural gas
PaoloPemi
our EOS package (provided by GC manufacturer) splits C6+ in a certain way which possibly originates some errors, that's the point of arguing, your proposal to use the full compostion from laboratory analysis is intersting but I don't know if our sofwtare can do that.
zdas04
the contract specifies a maximum dew point temperature (at pressures below our delivery point), we must compare results periodically to manual visual measurements, the point is that with our std. distribution for C6+ component we get errors in excess of 15 F while the process simulator and laboratory composition has errors of 5-10 F , from a practical point of view this should have a very limited impact (we know it's a matter of ppm) but there is room for discussions.
RE: C6+ characterization for natural gas
RE: C6+ characterization for natural gas
RE: C6+ characterization for natural gas
The point is that specifications parameters may include compositions, contaminants, water content etc. in addition to dew point, as example we have a maximum content for heavy components, water content and dew point.
RE: C6+ characterization for natural gas
RE: C6+ characterization for natural gas
that could be an alternative to laboratory analysis, I agree that adding a third column train to separate C6+ fraction would cost possibly 40K, however (as far as I know) a in-line automated chilled mirror costs more and I know little of other moisture analyzers (to monitor condensate and water dew point) using a variety of technologies (laser and so on) to recommend one, in addition we would prefer to maintain a single instrument so the GC solution is preferable over others.
However the problem we face seems different, sales contract specifies heating value, maximum water content and gas dew point, our client is calculating dew point with a process simulator and composition from laboratory analysis while we use our in-line GC (C1-C6+), results are different (10-15 F) and the manually operated chilled mirror which we use as reference returns intermediate values, possibly we have 10 ppm of condensate at different conditions, my point is that the difference is acceptable and within the limits of actual GC technolocy.
RE: C6+ characterization for natural gas
RE: C6+ characterization for natural gas
RE: C6+ characterization for natural gas
pressure reducer + separation on each line.
RE: C6+ characterization for natural gas
RE: C6+ characterization for natural gas
RE: C6+ characterization for natural gas
Best regards
Morten
RE: C6+ characterization for natural gas
RE: C6+ characterization for natural gas
And with a little additional price (can be less than 1000 $) you get many different properties which can be very accurate (see the above post).
RE: C6+ characterization for natural gas
RE: C6+ characterization for natural gas
RE: C6+ characterization for natural gas
RE: C6+ characterization for natural gas
RE: C6+ characterization for natural gas
RE: C6+ characterization for natural gas
RE: C6+ characterization for natural gas
when practicable installing a chilling system offers several advantages