Chapter 6F

6D.Hydrate Formation T at Specific P (Trekell-Campbell) Back to Main

This screen determines the hydrate formation temperature at a specific pressure using the Trekell-Campbell Method. All basic hydrate prediction correlations are for a system containing only gas and water in a static test cell that was rocked only to provide good equilibrium.

Trekell-Campbell Method

The Katz method possesses pressure limitations and fails to address the hydrate depression effects of molecules too large to fit into the cavities. Too many of these in one location make it difficult for a stable lattice to form around them.

The molecules larger than methane increases the ease of stable hydrate formation. This method uses methane as the reference condition. The additive effect of other molecules is then plotted in the Hydrate Prediction Correlations at 6.9 and 13.8 MPa graph (figures 6.19 and 6.19 (a)), the Hydrate Prediction Correlations at 20.7 and 27.6 MPa graph (figure 6.20 and 6.20 (a)), and the Hydrate Prediction Correlations at 34.5 and 41.4 MPa graph (figure 6.21 and 6.21 (a)). Each figure is for a specific pressure and the corresponding methane hydrate forming temperature. The abscissa shows the displacement of this methane hydrate forming temperature for the percentage of each component shown on the ordinate. The Hydrate Prediction Correlations for Non-Hydrate Formers graph (figure 6.22) is the negative correction (depression) for nonhydrate formers (pentanes plus). The parameter is the ratio of the mol fraction of pentanes plus to the sum of the mole fractions ethane, propane and butanes.

##### How do I carry out this calculation?

To carry out the hydrate formation calculation the pressure and the mole % of each component of the gas must be entered into the entry space. To do so use the mouse to click the cursor in the entry spaces and input the data. Once this has been done, select Run to execute the solution.

##### Definitions of the variables and where to obtain the unknown data

Pressure is the force exerted per unit area of the substance. For engineering purposes absolute pressure is used. In English units we add an "a" to indicate absolute pressure (psia, psfa); "g" is added to gauge pressure (psig, psfg). In SI metric no suffix will be used for absolute pressure.

The component table is a list of the possible compounds along with their symbols to be used with this program. In the far right column titled Mole % use the mouse to choose the available cell and enter the Mole % of each component in the mixture. Use the Up and Down arrow keys to move from cell to cell. The total for the Mole % should be 100.00.

Hydrates are a form of clathrate first discovered by Davy in 1810. A clathrate is any compound wherein guest molecules are entrapped in a cage structure composed of host molecules. With natural gas hydrate water molecules form the lattice. Contained within each lattice is a series of cavities of cages that must be occupied by enough guest molecules to stabilize this lattice crystal.

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