Hydrogen sulfide is nothing but a contaminant that is present in biogas. It is known to cause corrosion to instrumentation, equipment, and piping. The presence of different elements within biogas does have an effect on the end-use. Boilers may be able to tolerate hydrogen sulfide till 1000ppm. However, combustion engines work the best when the H2S is below 1000ppm. The technique used for extracting hydrogen sulfide is internal.
This is mostly done by utilizing Micro-organism. The organisms used are from the Thiobacillus. For the oxidation process of sulfide, oxygen needs to be added to biogas. However, the amount of oxygen will depend on the amount of hydrogen sulfide present in the biogas.
The simplest technique of desulphurization is to ad oxygen within the digester or even a tank that serves as storage. The Thiobaclli are then introduced and are not inoculated. They expand on the top of the digestive, this also provides the surface needed and the required nutrients. They create yellow patches of sulfur. The quantity of sulfur removal from natural gas will totally depend on the flow of air, the time is taken for the reaction, and temperature. If these are in perfect combination then the sulfur content can be brought down by 95%.
The process is not so simple as it sounds a lot of safety measures. The measure is to make sure that no overdosing happens if the pumps fail. Biogas when exposed to air can be explosive, if the methane content is high.
An Overview Of Dosing Using Iron Chloride
Iron Chloride is administered directly within the digester, which is in a storage tank. Iron chloride starts a reaction with the hydrogen sulfide and then we get iron sulfide in the form of salt particles. This technique works wonders for H2S removal from biogas. After this, the biogas can be used as fuel for various vehicles. However, this is only good for partial removal as it prevents corrosion of equipment. This technique is usually combined with another removal method to bring the levels down to 10ppm.
Removal Using Carbon
Removing hydrogen sulfide from little portions of biogas can be done through carbon that is nonpolar-activated as it acts as the perfect sorbent. You have to remember that activated carbon has a very limited capacity to absorb.
Different impregnated sorbents have been tested at various stages of reaction. The results revealed that the absorption of Hydrogen sulfide removal depends on the reaction conditions. To pick the perfect sorbent it is good to know about the water, oxygen, and gas content within biogas.
The good news is that this process does not require heavy investment as the equipment only consists of a dosing pump and a tank to hold the solution of iron chloride. The cost of operation may be high because of iron chloride. So, this is all you need to know about the removal process of hydrogen sulfide from Biogas. The process is always undergoing changes to make things easier.
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