This article is going to help you learn what H2S (Hydrogen Sulfide) is, and how you can remove this gas from biogas. The main objective of this article is to educate you and help you learn and expand your knowledge. So without further ado let us begin by understanding what H2S is.
What is H2S gas?
Hydrogen Sulfide is a gas with the formula H2S. This gas occurs naturally in biogas, volcanic gas, crude petroleum, and hot springs. H2S is produced by the breakdown of organic matter (waste of human or animal) in the absence of oxygen gas.
Here are some properties to identify the Hydrogen Sulfide gas –
1: Hydrogen Sulfide is a colorless gas.
2: H2S gas is flammable or explosive in normal conditions.
3: It burns in the presence of oxygen with blue flames.
4: The odor of H2S gas is like rotten eggs and can be smelled at low concentration.
5: H2S is slightly denser than air.
6: Hydrogen Sulfide act as a reducing agent.
6: Other names for Hydrogen Sulfide are – sewer gas, hydrosulfuric acid, and stink damp.
Before learning the process of Hydrogen Sulfide gas removal from biogas, let us understand why it is done.
Why remove H2S from Biogas?
Biogas contains Hydrogen Sulfide along with other gases like methane and carbon dioxide. It is a renewable resource that releases energy in the form of heat. However, due to the presence of H2S gas in biogas, the chances of corrosion, sulfur emission and odor increases when it is burned.
So, if the biogas is used in fuel cells, turbines or any other internal combustion system, it becomes necessary to remove the H2S gas in order to save the equipment. Plus removal of H2S gas from Biogas eventually protects the environment.
H2S removal method
There are several methods that can be used to remove the H2S gas from biogas. Some of them with an overview are mentioned below.
1: Iron Oxide Pellet – People needed low-cost option and they got one. The iron oxide pellets are packed in a unit and then the biogas is passed through it for desulfurization.
The iron oxide reacts with the H2S gas and converts it into iron sulfide. With approx. 100g iron oxide – 20g of sulfur can be removed.
2: Activated Carbon – This method can be applied in the pumping station and sewage treatment plants, as activated carbon is found to be the best option to remove H2S from air steam.
3: Iron Sponge Method – This process involves the use of a chemical reaction of ferric oxide with H2S solutions. It sweetens the gas streams without removing the carbon dioxide.
4: Water Scrubbing – It is the easiest & cheapest method of removing H2S from biogas in which water is pressurized and used as an absorbent.
Water scrubbing is the process of absorbing H2S & CO2 in the water at high pressure. And then restoring it with a release in pressure and a very little variation in temperature.
The removal of H2S from biogas may be costly and can require various technologies. Meaning every method for sulfur desulfurization comes with some drawbacks that could harm the environment directly or indirectly. So, one should keep in mind the resources that may be included in the process.
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