Difference Between Sweet and Sour Natural Gas

The key difference between sweet and sour natural gas is that sweet natural gas contains trace amounts of hydrogen sulfide, whereas sour natural gas contains large amounts of hydrogen sulfide.

Sweet natural gas and sour natural gas are two types of natural gas categorized based on the amount of hydrogen sulfide gas present in the natural gas.

1. Overview and Key Difference
2. What is Sweet Natural Gas
3. What is Sour Natural Gas
4. Side by Side Comparison – Sweet vs Sour Natural Gas in Tabular Form
5. Summary

What is Sweet Natural Gas?

Sweet natural gas is a type of natural gas containing trace amounts of hydrogen sulfide and carbon dioxide. This natural gas is non-corrosive in its pure form, and it requires little refining. We can also transport and market this gas safely.

There is an industrial process called gas sweetening, which involves the process of removing hydrogen sulfides, carbon dioxide, and mercaptans from natural gas. This removal process makes the gas suitable for transport and sale. Further, we need to convert sour gas into sweet gas because the presence of hydrogen sulfide and carbon dioxide makes the natural gas corrosive on gas pipelines and the gas also becomes more toxic to humans.

Difference Between Sweet and Sour Natural Gas

Figure 01: Production of Natural Gas in Different Countries

There are different methods of sweetening natural gas. We can choose a suitable method for this process, depending on the efficiency, cost, scale, and space we need for the process. The most common method is the membrane technology that uses a membrane with pre-treatment that is designed depending on the feed gas composition.

What is Sour Natural Gas?

Sour natural gas is a type of natural gas containing large amounts of hydrogen sulfide. Usually, natural gas is categorized as sour gas if it contains more than 5.7 mg of hydrogen sulfide per cubic meter of natural gas. This amount is equivalent to 4 ppm by volume. However, this value can vary depending on the country, state, and application.

Sometimes, people use the terms sour gas and acid gas interchangeably, but the true meaning of acid gas is described by the presence of any acidic gas, including hydrogen sulfide and carbon dioxide.

We need to take care when handling sour gas because it is highly corrosive and toxic to human. This gas can damage the piping and other equipment when storing and transporting the gas. The reason for its damaging behaviour is the sulfide stress cracking process that builds up inside the gas.

What is the Difference Between Sweet and Sour Natural Gas?

The key difference between sweet and sour natural gas is that the sweet natural gas contains trace amounts of hydrogen sulfide, whereas the sour natural gas contains large amounts of hydrogen sulfide. Moreover, sweet natural gas is non-corrosive, less acidic, and requires little refining. Also, it is easy to transport and handle the sweet natural gas. Meanwhile, sour natural gas is corrosive, can damage piping due to sulfide stress cracking process, requires more refining, difficult to handle.

Below is a summary of the difference between sweet and sour natural gas in tabular form.

Summary – Sweet vs Sour Natural Gas

Sweetening of sour gas is the process of converting sour gas into sweet natural gas by removing acidic gaseous component in the sour gas. This is because the key difference between sweet and sour natural gas is that sweet natural gas contains trace amounts of hydrogen sulfide whereas sour natural gas contains large amounts of hydrogen sulfide.