Various procedures are used to remove H2S from biogas including the use of Zero Valent Iron, red rock as well as bioreactors. All these processes are briefly described here under for your consideration.
Zero-Valent Iron
Zero-valent iron with 90% purity can be used to remove H2S from biogas and generate biomethane. Usually, biogas with the concentration of H2S up to 138, 139, and 211 PPM is introduced to the system of chemical removal of H2S from it. The results of these tests have shown that the concentration of H2S can be reduced to less than 50 PPM which can be accepted in the biogas used for running engines with internal combustion system. The removal of H2S in this process can depend upon the pH and the removal substances. While removing h2S with zero-valent iron or FeO, pH helps in the precipitation of sulfide and iron to form FeS. At pH 6 the maximum efficiency to absorb H2S can be up to 95% which is much better than the absorbents used traditionally. This process can also reduce the risk of pollution in the environment and the cost of the process.
Red rock
According to various studies, Red Rock is also a potent material for the removal of H2S from biogas. The samples of various sizes of the particles of red rock were collected, separated, and organized to calcinate at different temperatures from 500 to 1,000 degrees C. Then various technologies including FE-SEM, BET, and energy depressive X-ray florescent technique are used for characterizing the rock particles for using them in different phases.
These calcinated particles of Red Rock are then filled in the bed of the reactor as an absorbent through which the biogas is passed. The concentration of H2S in the biogas is recorded before and after passing through this absorbent. The absorption efficiency of the particles of red rock depends upon their calcination temperature, size, the mass of absorbent, rate of flow of biogas. It can be as high as 95% with the sample of smallest particles of red rock calcinated at the temperature of 1,000degree C as it can remove 0.37 grams of H2S from 100 grams of biogas.
Thus the performance of red rock in removing H2S from biogas is also promising.
Bioreactors
The anoxic and aerobic bioreactors can also be used individually or collectively to remove H2S from biogas. They are recommended to be used for commercial applications after summarizing the performance of both the bioreactors.
The biological processes of both of these bioreactors have proved their effectiveness for cleaning biogas by removing H2S from it in clinical trials. However, one of the main drawbacks of this process is the clogging of the bed with the deposit of sulfur and the accumulation of biogas in these beds. Though in a clinical trial the capacity of eliminating H2S from biogas is very high but it is not recommended for industrial use due to clogging of the bed.
Thus you can any of these processes for removing H2S from biogas in your establishment as per your suitability.
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