The H2S or Hydrogen Sulfide which is present in the biogas is actually an impurity. This can deter the use of the biogas as an eligible source of energy. The concentration of H2S can also vary based on the feedstock. The hydrogen sulfide concentration is the biogas in is actually the function of the digester feed substrate along with the inorganic sulfate content. The high protein wastes that contain the amino acids can influence the H2S levels.
Why removal of H2S is important?
During the process of digestion, the inorganic sulfate which is present in the feedstock gets reduced by some bacteria that are present in the digester. This results in contribution of more to the sulfide level that is present in the biogas. The H2S contained in the gas can cause bad smell and corrosiveness after the gas is burned. It is extremely important to remove the hydrogen sulfide from the biogas if it is going to be used as fuel in combustion engines, turbines and cells.
Techniques for removing H2S
Here are some of the techniques that are used for removing H2S from the biogas:
- Iron sponge
- Activated carbon
- Iron oxide pellets
- Sodium hydroxide scrubbing
- Water scrubbing
- Biological removal over the filter beds
Commonly used methods for H2S removal
The different level of concentration of different components of the biogas impacts its usage. While the boilers can withstand the concentration up to 1000 ppm, the internal combustion engine can function well only when the H2S is managed below 100 ppm. Two of the most common methods used for removing H2S from biogas are: Oxygen dosing and Iron chloride dosing.
Oxygen (air) dosing: The biological desulphurization or the oxygen dosing of the biogas can be performed with the help of the microorganisms. Almost every microorganism belonging to the Thiobacillus family is capable of oxidizing the sulfide. For oxidation of the sulfide, you will need to add the air or oxygen is a particular ratio to that of the biogas. This is a simple method where you have to add oxygen directly to the digester or the storage tank. Safety measures must be taken for preventing any overdosing of oxygen. You need to understand that the biogas in oxygen can result into explosion.
Iron chloride dosing: Iron chloride can be fed to the digester directly or it can be given to the feed substrate in the pre-storage tank. Then, the produced H2S will react with the iron sulfide for producing a compound called iron sulfide salt. The method has a great effect in lowering or removing the hydrogen sulfide from the biogas.
So, you have to choose the right technique for removing the hydrogen sulfide from the biogas. While choosing the right method, you have to consider some of the important factors such as cost of the chemicals uses, vacuum trucks for emptying the filters and disposal of wastes. Considering all these factors is very important otherwise there can be some risk of ignition of the spent adsorbent or the used adsorbent. Make the wise decision.
Chemical Products Industries Also Offers Following Services :
Chemical Products Industries, Inc. Address: 7649 SW 34th St, Oklahoma City, OK Phone: (800) 624-4356