Tuesday, February 12, 2013

Removing impurities: Sweetening sour natural gas

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Some wells where natural gas is extracted contain significant amounts of sulfur, in the form of hydrogen sulfide. Hydrogen sulfide -laden natural gas, or sour gas, is dangerous because it is composed of harmful and often lethal compounds, and can sometimes also be corrosive. In addition, sulfur compounds extracted from natural gas streams can also be sold and marketed on its own.

Sulfur extraction from natural gas is also commonly known as “sweetening the gas.” The process that is used for this is very similar to that of glycol dehydration and NGL absorption, but instead of glycol and absorption oil, amine solutions are used. This is called the Girdler or amine process. In this process, the hydrogen sulfide-laden natural gas is run through a tower that contains the amine solution from top to bottom. The amine solution absorbs sulfur compounds from the sour natural gas, leaving it “sweetened.” Similarly to glycol dehydration and NGL extraction, the amine solution can also be reused.

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However, for sulfur to be sold, it has to be reduced to its base form. The hydrogen sulfide-laden amine solution is then run through something called the Claus process, which then extracts the base element sulfur from the hydrogen sulfide-laden solution using thermal and catalytic reactions.

Removing impurities and other substances from natural gas is the most important part in natural gas processing because it ensures that the natural gas used by families and homes across the US is clean, safe, and environmentally friendly. Natural gas engineering books, like Boyun Guo and Dr. Ali Ghalambor’s Natural Gas Engineering Handbook, expound on these important processes.

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