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BIOGAS TREATMENT · TECHNICAL ARTICLE

Biological and chemical scrubbers for high-volume biogas desulphurisation

At higher gas flow rates or H₂S loads, an external scrubber can remove most of the sulphur using liquid regeneration or biological oxidation.

7 min readSources are listed at the end of the article
Two tall scrubber columns with a recirculation tank and piping to remove hydrogen sulphide from biogas
A scrubber transfers H₂S from the gas to a liquid phase; the absorption liquid is then regenerated chemically or biologically.

When a plant handles a large biogas flow or H₂S concentrations are too high for economical activated-carbon use, an external scrubber becomes relevant. Rather than using a consumable medium in a small vessel, it continuously transfers H₂S from the gas into a liquid phase, then treats or regenerates the absorption liquid.

Biological scrubbers

Paques' THIOPAQ combines H₂S absorption with biological regeneration of an alkaline solution and production of elemental sulphur. According to the manufacturer, the technology is used in biogas and biomethane applications and can handle a wide range of inlet H₂S loads.

Biogasclean and the moving-bed approach

Biogasclean's BMR uses a biological moving-bed reactor. After compression, cooling and controlled air addition, the gas enters through diffusers and H₂S is biologically oxidised to elemental sulphur. Such systems are of interest where gas flow and sulphur load are substantial.

Chemical scrubbing

Chemical scrubbers use an absorption liquid that binds H₂S through a chemical reaction. Depending on the chemistry, the reagent may be regenerated or consumed. Rapid response to changing loads is an advantage; chemical consumption, waste streams and the need for corrosion-resistant equipment can be disadvantages.

What matters in selection?

  • raw gas flow in Nm³/h and its operating range
  • average and peak H₂S concentrations
  • target outlet H₂S concentration
  • availability of air, oxygen, chemicals and water
  • sulphur production and its potential market or disposal route
  • electricity consumption and required pressure
  • need for standby capacity or a bypass

Scrubber plus final polishing

A common arrangement uses a scrubber to remove most of the sulphur and a smaller activated-carbon filter for final polishing. This reduces carbon replacement frequency while maintaining a low and stable outlet concentration.

Key pointA scrubber is a process unit, not simply a filter. It becomes economical when the sulphur load and gas flow justify a continuous regeneration or biological treatment system.

Sources and further reading

This article is for information only. The final cleaning specification must be based on analysis of the actual gas composition, the end user's requirements, safety rules and confirmation from equipment manufacturers. The illustration shows the functional principle, not a construction design.