Chapter 6E

6C. Hydrate Formation T at Specific P (Katz) Back to Main

Katz and his co-workers developed a set of Kv-s values for hydrate prediction. Figures 6.14 - 6.18 are the Kv-s charts for use of this method. In spite of some theoretical flaws in the method it has proven very reliable up to about 7 MPa [1000 psia].

A dewpoint type calculation is made using the Kv-s values obtained from the graphs. Use the known pressure and assume a temperature to obtain the Kv-s values. Through trial and error plug values into equation (6.5) until it becomes a true statement. Kv-s equals infinity for all non-hydrate formers present. Equation (6.5)

S ( yi / Kv-s ) = 1.0

Where " yi" is the mole fraction of each component in the gas.

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

To calculate the water content the pressure and mole % of each component in the mixture must be entered into their entry spaces. 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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