Source of hydrogen sulfide
Hydrogen sulfide mainly comes from the following aspects in sewage treatment systems:Working environment of chemical plants and pharmaceutical plants: These industrial sites often produce wastewater containing sulfur compounds, including hydrogen sulfide.
Water inlet lifting pump room of sewage treatment plant: The organic wastewater and exhaust gas in the water inlet lifting pump room often contain a large amount of hydrogen sulfide.
Anaerobic digestion process of primary sedimentation tank sludge: During the anaerobic digestion process of primary sedimentation tank sludge, odors such as hydrogen sulfide will also be released.
Sludge digestion and stabilization process: The ammonia produced during the digestion and stabilization process of sludge may also react with other compounds to produce hydrogen sulfide.
In addition, the formation of hydrogen sulfide is closely related to organic sulfur and inorganic sulfur. Organic sulfur includes compounds containing carbon elements, such as mercaptans, thioethers, etc.; while inorganic sulfur mainly refers to inorganic compounds such as H2S, SO2, SO3, etc. Organic sulfur is generally difficult to remove, while inorganic sulfur is relatively easy to remove.
The principle of activated carbon for hydrogen sulfide removal
Activated carbon is a non-polar molecule, and its principle of removing hydrogen sulfide is mainly achieved through oxygen reduction reaction. The specific reactions are as follows:H2S + O2 → S (solid) + H2O + H2
In addition, impregnated activated carbon, especially activated carbon impregnated with potassium hydroxide (KOH) or sodium hydroxide (NaOH), can also effectively remove hydrogen sulfide in the neutralization reaction. The reaction formula is as follows:
H2S + 2KOH (full amount) → K2S + 2H2O
What are the factors affecting activated carbon adsorption efficiency?
Size, CTC, impregnation amount
Size: The size of the activated carbon particles affects its flow in the treatment system and its adsorption efficiency.CTC: The higher the CTC value, the larger the apparent specific surface area, and the adsorption efficiency of activated carbon will usually be higher.
Impregnation amount: Adjusting the impregnation amount can change the adsorption performance of activated carbon, and an appropriate amount of impregnation can improve the removal efficiency of hydrogen sulfide.
Relative humidity
As the relative humidity increases, the liquid film formed on the desulfurizer becomes thicker, the gas mass transfer resistance increases, the effective diffusion coefficient decreases slightly, and the slope of the penetration curve decreases. On the other hand, the deactivation coefficient decreases and the working sulfur capacity increases. Because less water is not enough to form a water film in the activated carbon pores, or the volume of the water film is smaller, the active sites provided for the reaction are reduced.The appropriate oxygen content
The operating conditions for the adsorbent to adsorb H2S are oxygen content 2%, temperature 95 degrees, and space speed 1000-2000h-1. (1000-2000 cubic meters per hour)Under low oxygen content, the adsorption capacity of the adsorbent is not high. As the oxygen content increases, the adsorption capacity increases. After increasing to 3.5%, increasing the oxygen content has less and less impact on the adsorption capacity; physical adsorption is dominant between 20 and 70 degrees. , chemical adsorption is dominant at 70-95 degrees. Physical adsorption occurs at low temperatures. As the temperature increases, the physical adsorption effect decreases, the chemical adsorption effect gradually increases, and the adsorption capacity first decreases and then increases; as the air velocity increases, the adsorption capacity of the adsorbent decreases.
Effect of gas concentration on hydrogen sulfide adsorption
The mass concentration is high, the macroscopic reaction rate is fast, and the product deposition rate is fast. Therefore, it quickly approaches saturation, so that some active sites are not fully utilized. On the contrary, when the mass concentration is low, the reaction proceeds relatively slowly. The product sulfur is gradually deposited, so that the active sites are fully utilized, so the working sulfur capacity is high.Which type of activated carbon is most effective for removing H2S?
Pillar activated carbon is also a common option for hydrogen sulfide removal. Pillar activated carbon has high specific surface area and good adsorption performance, and is suitable for treating hydrogen sulfide in sewage. Its parameters are usually as follows:
| Item | Activated carbon pellets |
| Size | 3mm, 4mm, 5mm |
| Impregnation amount | 8-15% |
| CTC | ≥50% |
