What is the Difference Between Sweet and Sour Natural Gas?

The difference between sweet and sour natural gas lies in the presence of hydrogen sulfide (H2S) and carbon dioxide (CO2) in the gas.

• Sweet natural gas contains trace amounts of hydrogen sulfide and is non-corrosive, less acidic, and requires little refining. It is easy to transport and handle.
• Sour natural gas contains large amounts of hydrogen sulfide and carbon dioxide, making it highly corrosive and acidic. It is difficult to handle and requires more refining. Sour gas is usually considered as such if it contains more than 5.7 mg of hydrogen sulfide per cubic meter, which is equivalent to 4 ppm by volume.

Sweetening is the process of converting sour gas into sweet natural gas by removing the acidic impurities, such as H2S and CO2. This process is essential as it prevents corrosion problems and increases the heating value of the gas. Sour gas sweetening is often achieved through energy-intensive chemical scrubbing, which may not be economically viable for gas with high concentrations of H2S and CO2. An alternative is the use of tailored polyimide membranes that can purify sour gas with a wide range of compositions.

Comparative Table: Sweet vs Sour Natural Gas

The main difference between sweet and sour natural gas lies in the presence of hydrogen sulfide (H2S) and carbon dioxide (CO2). Here is a summary of the differences in a table:

Sour natural gas is characterized by containing large amounts of H2S and CO2, making it highly corrosive and more acidic than sweet natural gas. Sweet natural gas, on the other hand, contains only CO2 and trace amounts of H2S, making it non-corrosive, less acidic, and requiring less refining. Sour gas must be "sweetened" by removing its acidic impurities before it can be used or transported through pipelines.