Hydrate analysis operates on a single stream and supports a single EVALUATE definition. This hot key is a subset of the complete functionality described in PRO/II Keyword Input Manual, chapter 125.
Defaults are: POINTS=30, Inhibitor = None,
IPRESSURE(ATM)=0.1, MAXPRES(ATM)=400.0, DP=0.0.
Note: Hydrate calculations assume the presence of free water for hydrates to form. An error should occur if this situation does not exist in the stream of interest.
Either temperature or the pressure range of the analysis can be specified. Regardless of which option is chosen, the lower limit value and the number of points to generate are required. The user has the choice of supplying either the upper limiting value or an increment between each point. When the maximum value is given, increment is computed from the lower and upper limit values and the number of points; i.e.,
Increment = ((Hilim - Lolim) / Npts) + 1
When the increment is given, the upper limit is calculated from:
Hilim = Lolim + (Npts * increment)
All possible hydrate formers are: C1, C2, C3, nC4, iC4, CO2, H2S, N2, ethylene, propylene, Ar, Kr, Xe, cyclo-propane, and sulfur hexafluoride. Only hydrate formers present in the stream of interest will be tested. This behavior is strictly in conformance with that of the Hydrates unit operation.
Optionally, a single inhibitor may be selected from a predefined list available in a combo box.
The possible inhibitors are limited to
(1) NaCl (salt),
(2) methanol,
(3) Ethylene Glycol (EG),
(4) DiEthylene Glycol (DEG), and TriEthylene Glycol (Teg).
The selected inhibitor must be present in the stream of interest and will be ignored if absent. This is intended to maintain strict compliance with the normal behavior of the Hydrates unit operation. Hydrate concentration are in terms of wt% and represents the amount present in the aqueous phase.
Calculations
The user presses either the Show Plot or the Show Table button to initiate calculations. In either case, the calculations are identical. This is equivalent to executing a single EVALUATE statement in the Hydrate unit operation. Any hydrates that form are of either "Type I" or "Type II". All data for "Type I" (from all hydrate formers) constitute one set of data for one curve. All "Type II" values (from all hydrate formers) may constitute a second set of data for a single (second) curve. The type of hydrate formed is not specified beyond "Type I" or "Type II".
Hydrate Plot Display
For the "Show Plot" case, pressing the "Show Plot" button executes the calculations. Immediately upon completion of calculations, a dialog box appears to display the available plot options.
Initially, the only two plot options are graphs of Hydrate forming versus Temperature and Pressure. The first plot has temperature on the X axis and pressure on the Y-axis. The second plot is the same, except the axes are transposed so that pressure is on the X-axis and temperature is on the Y-axis. In both cases, some convention should be adopted to identify points as representing Type I, Type II, both, or neither type of hydrates. Various symbols or color conventions should be chosen as appropriate to indicate these distinctions. Preferably, the plot would include a legend that explained the various colors or symbols.
Hydrate Tabular Display
Unlike the "Show Plot" option, the "Show Table" button offers no display options. As soon as calculations are complete, the data is displayed in a table. The data format is consistent with the layout and content of the normal report of the Hydrate unit operation.
Note: Because the hot keys are designed to be quick and easy, they may not offer all the functionality of the feature already implemented in the GUI.
The data for the hot key is stored locally, is temporary, and is thrown away when the hot key WINDOW is closed. Hot Key functionality is available to users in demand mode. Hydrates are not supported at all through the GUI