These are some of the reasons why this is a continuing area of concern in the gas industry. Equally unfortunately, the accurate analysis of the C6+ fraction requires very careful chromatographic analysis by skilled analysts using well-calibrated gas chromatographs. Very small amounts of heavy ends (1 mole percent or even less) can affect the cricondentherm temperature by 10 deg. In addition, the accuracy of the measurement for the heavy ends is crucial. Also, it is virtually impossible to do this calculation by hand, as a horrendous amount of iteration is involved, no matter which equation of state you use to describe the underlying thermodynamics.įinally, I would also say the "answer" is by no means unique: it depends on the chosen equation of state and, further, on the binary interaction parameters chosen. That is why the most practical solution is to use a commercial package - most engineers do not have the required chemical engineering knowledge, mathematical training, and programming skill to implement, for example, Michelsen's algorithm themselves on a computer. Their algorithms are both very reliable and fast, and have been encoded in the major process simulators, as mentioned by Homayun in this thread. This has been an area of considerable research (Heidemann and Khalil, Michelsen). I can personally attest to this fact, having spent considerable effort on the problem myself many years ago. Unfortunately, bubble pressure calculations become progressively harder to converge as the system approaches the cricondentherm temperature. Then you are in the liquid region, following the curve further will take you to the cricondenbar pressure, and so on. At this point, the curve swings back toward the critical point. Stated another way, above the cricondentherm temperature, you will never condense liquids out of a vapor mixture of the given composition, as you will be in the supercritical region no matter what the pressure.Ĭalculating the cricondentherm temperature requires doing phase equilibrium calculations (bubble pressures at gradually increasing temperatures) until you reach the cricondentherm temperature. On the phase envelope, this corresponds to the highest temperature at which any liquid will ever form, irrespective of pressure. In the gas industry, the "dew point" generally denotes the cricondentherm temperature. RE: Hydrocarbon dewpoint (HDP) bonzoboy (Chemical) 27 Dec 05 10:57 temperature would be essentially flat until the measurable dew point is reached.
#Hydrocarbon dew point calculator excel simulator
If a simulator is being used, you could observe this by having it do a condensing curve on the gas. Yet the real gas, if cooled to that temperature might not show any real amount of condensation until some considerable cooler temperature, what you might call the "measurable" dew point. If the gas composition in question is itself generated by computer model and has 1 ppm of a very low-volatile heavy, then the y/K for that component could be calculated as being in the vicinity of 1 at the calculated DP.
#Hydrocarbon dew point calculator excel software
The danger in using software to do dew point calculations is that, even if the method for predicting K values is appropriate for the system, they will just give what I would call a "theoretical" dew point, at which temperature the smallest amount of liquid would start to form.
As you sum up the X values, as y/K, you can see which components contribute most to the summation of X. I salute the comments on "looking under the hood" on dew point calcs, and I thought I'd expand a bit on TD2K's remark about the heavies having most effect on dew point.
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