One should be aware of the maximum pressure for the phase envelope (cricondenbar).The hydrocarbon dewpoint for an analysis which shows an amount of "C7+" can have a very different dewpoint depending on whether the heaviest component is assumed to be (e.g.) n-C7 or n-C10.Hydrocarbon dewpoint calculations are very sensitive to trace amounts of heavier hydrocarbons.Note that in recent versions of HYSYS a "COM Thermo Three-Phase" envelope can be plotted which shows both the water and hydrocarbon dewpoint lines. By default, the envelope utility is constructed on a dry basis and therefore the dewpoint line corresponds to the hydrocarbon dewpoint. Be careful when comparing stream dewpoints to those calculated by the envelope utility.
All TEG is therefore removed at the flowsheet boundary, and the dewpoint can be calculated in the main flowsheet. When the dry gas leaves the TEG subflowsheet, it should transfer to the main flowsheet property package which does not contain TEG. use a different property package for TEG dehydration/regeneration which includes the component TEG.use a component splitter to remove all TEG from the dry gas, and then calculate the dewpoint.Streams which have small amounts of TEG (e.g., dry gas from a TEG contactor) can predict an incorrect dewpoint.However, there are some pitfalls to watch out for: Usually, HYSYS does a reasonable job calculating stream dewpoints. If you wish to calculate a dewpoint at a pressure which is different than (e.g.) the sales gas pressure, we recommend using a Balance operation to transfer the composition to a new stream, and then specify a new pressure in that stream. Gas property correlations can be enabled by selecting the "Append New Correlation" button on the Properties tab of a stream, and are available under the "Gas" heading. HYSYS 3.1 introduced gas property correlations which enable dewpoints to be calculated in the stream.Once registered, it can be added as a unit operation extension. To use the Gas Properties unit operation extension, it must first be downloaded from the Aspentech Technical Support site, then registered in HYSYS. Aspentech developed a unit operation extension called "Gas Properties" which calculates both the hydrocarbon and water dewpoints for the stream to which it is attached.Here are two ways to easily calculate hydrocarbon and water dewpoints in HYSYS: However, this calculation does not differentiate between a hydrocarbon or water dewpoint (unless you look at the incipient phase). Most HYSYS users know that a stream dewpoint can be calculated by setting the vapour fraction to 1. HYSYS is well-suited to calculate these properties - in particular much work has gone into fitting the Peng Robinson equation of state interaction parameters for standard gas operations. Sales gas specifications vary by region and by recipient these are typical gas specifications in Alberta, Canada. Shall have a gross heating value of not less than 36 MJ/m3.Shall not contain more than 4 lb H2O/MMSCF.Shall not contain more than two (2) percent by volume of carbon dioxide.Hydrocarbon dewpoint not to exceed -10C at operating pressure.Water dewpoint not to exceed -10C at 8275 kPa.Typical sales gas specifications are as follows: A process engineer supporting gas operations will often need to use HYSYS to calculate sales gas properties such as water dewpoint, hydrocarbon dewpoint, heating value and water content.
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