Activated Carbon for H2S Removal From Biogas/Oil and Gas

Hydrogen sulphide (H₂S) is a toxic and flammable gas with a “rotten egg” odour, which is commonly found in industrial and biological fermentation processes. Activated carbon is widely used to remove H₂S due to its adsorption properties.

In this article, we will discuss the role of активированный уголь in the removal of hydrogen sulphide, introduce the different types of activated carbon products and their advantages, and share a guide to selecting the right activated carbon.

Why Is It Necessary to Remove H₂S?

The removal of H₂S is essential for several reasons:

• Health Risks: Prolonged exposure to H₂S can cause respiratory issues, eye irritation, and can even be fatal at high concentrations.
• Corrosion Prevention: H₂S is highly corrosive and can damage metal equipment, pipelines, and infrastructure, leading to expensive maintenance costs.
• Operational Efficiency: In biogas production, removing H₂S is necessary to protect downstream equipment and ensure the gas meets pipeline specifications or is suitable as vehicle fuel.

In this context, activated carbon serves as an ideal solution due to its highly efficient adsorption properties.

The Role of Activated Carbon in H₂S Removal

Activated carbon, with its highly developed porous structure, can adsorb various gases and chemicals. In the case of H₂S removal, activated carbon functions in the following ways:

• Adsorption: The porous structure of activated carbon allows it to effectively adsorb H₂S molecules. Through this adsorption process, activated carbon traps H₂S molecules in its pores, reducing the concentration of H₂S in the air.
• Chemical Reactions: Some specially treated activated carbon, such as potassium iodide (KI)-impregnated activated carbon, not only physically adsorbs H₂S but also chemically converts it into harmless sulfur or sulfuric acid.
• Protecting the environment: H₂S emissions pollute the air and have negative impacts on ecosystems, including acidification of soils and water bodies and toxic effects on plants and animals.
• Efficiency: Compared to other H₂S removal methods, activated carbon offers cost-effectiveness and high treatment efficiency, especially in high-flow and high-concentration gas applications.

Applications of Activated Carbon for H₂S Removal

Activated carbon is widely used for H₂S removal in various critical applications:

Очистка биогаза

Биогаз, produced from the anaerobic digestion of organic waste (e.g., agricultural waste, food waste), primarily consists of methane but may also contain H₂S.

Activated carbon can efficiently remove H₂S from biogas, improving its quality and usability while reducing environmental pollution and health risks.

Additionally, activated carbon can remove volatile organic compounds (VOCs) and siloxanes from biogas, preventing their release during combustion and protecting downstream equipment.

Oil and Gas Industry

H₂S is a common byproduct in the production and refining of oil and natural gas. Removing this hazardous gas is essential to ensure safe production and long-term equipment stability. Activated carbon efficiently removes H₂S, ensuring a safe operating environment and extending the lifespan of equipment.

Wastewater Treatment Plants

H₂S may be generated during the wastewater treatment process, especially in the effluent settling tank and anaerobic digestion stages. Due to its strong toxicity and odor, hydrogen sulphide gas must be removed promptly to ensure the safety of the working environment and the normal operation of wastewater treatment facilities.

The use of specially treated activated carbon can effectively adsorb and remove hydrogen sulphide during the wastewater treatment process, improving the air quality and avoiding the corrosive effects of hydrogen sulphide on the facilities.

Landfill Gas Treatment

Landfills generate biogas during anaerobic digestion, which contains H₂S and other pollutants. Due to its excellent adsorption capability, activated carbon plays a vital role in landfill gas treatment. It effectively adsorbs H₂S and converts it into harmless sulfur, protecting equipment from corrosion and improving the overall quality of the gas.

Dairy Plants and Co-Fermentation Facilities

Dairy plants generate waste that, after anaerobic digestion, releases H₂S, posing odor and corrosion risks to equipment and the environment.

Similarly, co-fermentation facilities produce sulfur-rich biogas. Activated carbon can effectively adsorb and convert H₂S into harmless elemental sulfur, protecting equipment and improving waste gas treatment efficiency.

Types of Activated Carbon for H₂S Removal

Selecting the appropriate type of activated carbon is crucial for effective H₂S removal. The following table provides a detailed comparison of several commonly used activated carbon types:

Activated Carbon Type	Reaction Mechanism	Applicable H₂S Concentration	Oxygen Requirement
Гранулированный активированный уголь	Physical adsorption	Low	No
KI-Impregnated Activated Carbon	H₂S + ½ O₂ → S + H₂O	High	Required
NaOH-Impregnated Activated Carbon	H₂S + 2 NaOH → Na₂S + 2 H₂O	Medium to High	No
KOH-Impregnated Activated Carbon	KOH + H₂S → KHS + H₂O	High	No
Catalytic Activated Carbon	H₂S + O₂ → S + H₂O	High	Required
Iron Oxide Desulfurizer	H₂S + Fe₃O₄ → FeS + H₂O	Medium to Low	No

Гранулированный активированный уголь

Гранулированный активированный уголь is commonly used for adsorbing harmful gases and is suitable for low-concentration H₂S treatment. Produced through specialized granulation and drying processes, GAC offers high stability, abrasion resistance, and corrosion resistance, making it effective for H₂S adsorption.

Features:

• Suitable for low-concentration gas treatment
• Reusable through regeneration processes
• Easy to operate and replace

KI-Impregnated Activated Carbon

KI-impregnated activated carbon is chemically treated and impregnated with KI. It can catalyze the oxidation of H₂S into harmless elemental sulfur (S).

Reaction Mechanism:

KI-impregnated activated carbon catalyzes the oxidation of H₂S into elemental sulfur through reactions such as:

• H₂S + ½ O₂ → S + H₂O
• 2 CH₃-CH₂-SH + ½ O₂ → CH₃-CH₂-S-S-CH₂-CH₃ + H₂O

To ensure complete conversion of H₂S to sulfur, the required oxygen amount should be 1.7 times the stoichiometric amount.

Operational Considerations:

• Mixing Uniformity: To achieve high sulfur loading, H₂S and oxygen must mix thoroughly. Poor mixing reduces efficiency and sulfur loading capacity.
• Humidity Control: If the relative humidity of the gas exceeds 60-70%, reaction efficiency may be affected. Heating the gas can improve efficiency in such cases.

Advantages of KI-Impregnated Activated Carbon:

• Efficient Conversion: Effectively converts H₂S into elemental sulfur, reducing harmful emissions.
• Oxygen Requirement: Requires oxygen to sustain the catalytic oxidation reaction.
• Applicability: Ideal for environments with high H₂S concentrations.

NaOH-Impregnated Activated Carbon

NaOH-impregnated activated carbon removes H₂S through chemical adsorption. This process does not require oxygen, as H₂S reacts with NaOH to form harmless sodium sulfide and water:

H₂S + 2 NaOH → Na₂S + 2 H₂O

Features:

• No oxygen requirement
• Suitable for medium to high H₂S concentrations
• Effective for removing other acidic gases

KOH-Impregnated Activated Carbon

KOH-impregnated activated carbon removes H₂S through chemical adsorption and reaction. KOH reacts with H₂S to form soluble compounds, enhancing the selectivity of H₂S adsorption:

KOH + H₂S → KHS + H₂O

Features:

• Highly efficient for acidic gas adsorption
• Handles complex gas compositions
• Suitable for high H₂S concentrations

Catalytic Activated Carbon

Catalytic activated carbon combines metal oxides (e.g., iron oxide, copper oxide) with activated carbon. These metal oxides catalyze the oxidation of H₂S, converting it into harmless substances like sulfur or sulfates:

H₂S + O₂ → S + H₂O

Features:

• High-efficiency H₂S removal, suitable for high-concentration gases
• Requires oxygen to enhance catalytic reactions
• Suitable for large-scale industrial applications

Iron Oxide Desulfurizer

Iron oxide desulfurizers remove H₂S by reacting with it to form iron sulfide (FeS). These materials are commonly used in natural gas purification and exhaust gas treatment, particularly for medium to low H₂S concentrations. Iron oxide desulfurizers are highly effective and can be regenerated through simple processes.

Features:

• Suitable for medium to low H₂S concentrations
• Regenerable through simple processes
• Ideal for natural gas and industrial exhaust gas treatment

Заключение

The removal of H₂S is critical for many industrial processes, and activated carbon provides a reliable and cost-effective solution for gas purification. By selecting the appropriate type of activated carbon based on the application and gas characteristics, efficiency can be maximized, ensuring smooth industrial operations.

If you need an efficient H₂S removal solution, feel free to связаться с нами. We offer a variety of impregnated and catalytic activated carbon products tailored to meet different industrial demands, ensuring a safe and environmentally friendly production environment. Visit our product page or reach out to us directly for quotes!