Iron Oxide Dry Desulfurization System

Dry desulfurization principle

Dry desulfurization involves filling a cylindrical desulfurization tower with a certain height of desulfurizing agent. Biogas passes through the desulfurizing agent from bottom to top, removing H₂S and achieving the desulfurization process. Iron oxide is a commonly used desulfurizing agent in wastewater treatment plants, and its granules are cylindrical. The principle of iron oxide desulfurization is as follows:

Fe₂O₃H₂O+3H₂S=Fe₂S₃H₂O+3H₂O

As can be seen from the reaction equation above, Fe₂O₃ absorbs H₂S to become Fe₂S₃ . As biogas is continuously produced, iron oxide absorbs H₂S . When the amount of H₂S absorbed reaches a certain level, the removal rate of H₂S will be greatly reduced until it becomes ineffective.

Advantages of dry desulfurization

1. Simple structure and easy operation: The system has no complex moving parts, requires little equipment maintenance, and is suitable for low-cost operation and maintenance of small and medium-sized biogas projects (processing capacity <500m³/h).

2. Low investment cost, outstanding economic efficiency, and simple equipment: The desulfurization tank itself has a simple structure and does not require a large number of auxiliary equipment (such as circulating pumps, heating systems, etc.). The initial equipment investment is far lower than that of complex processes such as wet desulfurization. Small footprint: The entire system is compact and has low site requirements, making it very suitable for projects with limited space.

oxide desulfurizers can reduce H2S to below 20mg/m³, meeting the standards for biogas power generation and domestic gas supply.

4. Simple operation and maintenance, controllable operating costs: It operates at normal temperature and pressure, without the need for heating or pressurization equipment, with low energy consumption. The operating cost is only the cost of replacing the desulfurizing agent (approximately 0.1-0.3 yuan/m³ biogas).

5. High safety: The desulfurization reaction is mild, with no risk of flammability or explosion, and the desulfurizing agent (such as iron oxide) itself is non-toxic. After disposal, it can be treated as ordinary solid waste (or recover elemental sulfur).

6. No secondary pollution, environmentally friendly, dry process: The desulfurization reaction is a gas-solid phase reaction, and the products are solid sulfur or sulfides (such as iron sulfide) that remain in the packing material. No wastewater is generated, avoiding complex wastewater treatment problems and making it more environmentally friendly.

7. High flexibility, strong adaptability, and modular design: Single or multiple tanks (connected in series or parallel) can be flexibly configured according to the biogas production volume, facilitating capacity expansion. Resistant to load fluctuations: It has good adaptability to fluctuations in biogas production and concentration, making it particularly suitable for intermittent production or situations with unstable gas volume (such as livestock farms or seasonal production plants).

Key operating parameter control

1. To ensure desulfurization efficiency and system stability, the following operating parameters must be strictly controlled:

Biogas residence time: The residence time of biogas in the desulfurization tower needs to be ≥10 seconds (adjusted according to the H2S concentration, the higher the concentration, the longer it needs to be) to ensure that H2S reacts fully with the desulfurizing agent; this is usually achieved by controlling the biogas flow rate (frequency conversion adjustment of the blower) .

2. Biogas moisture content: The biogas entering the desulfurization tower must have a moisture content of <80% (dew point temperature <15℃) to prevent the desulfurizing agent from absorbing water and clumping; the moisture content can be reduced by a pre-cooler or an adsorption dryer.

Desulfurizer filling height: The desulfurizer bed height is usually 2-3 times the tower diameter (e.g., 2-3m for a 1m tower diameter) to ensure sufficient reaction contact area; the filling should be uniform to avoid "channeling" (local short circuit of biogas, where it does not react with the desulfurizer).

3. H₂S concentration monitoring: Online installation of H₂S ... The detectors (one for the inlet and one for the outlet) should be used. When the outlet H2S concentration exceeds the set value (e.g., 20 mg/m³), the desulfurizing agent should be replaced promptly. It is recommended to record the data once per hour to track the desulfurization efficiency.

Applicable to

1、Applicable to: places that generate large amounts of biogas, such as large-scale sewage treatment plants, large-scale livestock and poultry farms, large food factories, kitchen waste treatment facilities, and landfills.