Chapter 6B

6B. Water Content of Sour Natural Gases Back to Main

This screen is used to determine the water content of gases containing H2S and CO2. Equation (6.2) does this by multiplying the water content of the pure sour component by its mol fraction in the mixture. Figures 6.2 and 6.3 show what is called the "effective water content."

(6.2)

Where: W = water content of gas

Whc = water content of hydrocarbon part of gas from figure 6.1

W1 = water content of CO2 from Figure 6.2 and 6.4

W2 = water content of H2S from Figure 6.2 or 6.5

y = 1 – y1– y2

y1 = mol fraction of CO2

y2 = mol fraction of H2S

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

To carry out the water content calculation the temperature, pressure, H2S mole percent, and the CO2 mole percent of the gas 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 the correct data has been entered, select Run to execute the solution.

As we have compared the results of this method with others we find that it is consistently high. It is the maximum possible value that can occur within a range of possible values.

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

A sour gas has a significant amount of sulfur compounds and/or carbon dioxide.

Pressure is the force exerted per unit area of the gas. 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.

Temperature is the temperature of the gas in SI units, Celsius and Kelvin or in English units, Fahrenheit and Rankin.

° C = 0.556 (° F - 32), K = ° C + 273, ° F = (1.8)(° C) + 32, ° R = ° F + 460

H2S Mole Percent is the mole fraction of Hydrogen Sulfide in the mixture multiplied by 100.

CO2 Mole percent is the mole fraction of Carbon Dioxide in the mixture multiplied by 100.

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