Flue Gas Treatment

Efficient flue gas cleaning

reliable pollutant abatement through wet scrubbing

Flue gases from combustion and industrial processes contain a variety of acidic and toxic pollutants that must be reliably removed to comply with environmental regulations and emission standards. Our two-stage flue gas cleaning systems, consisting of a quencher and a packed-bed column, enable highly efficient removal of pollutants such as SO₂, HCl, Cl₂, HF, HBr, Br₂, and Hg(II).

How does it work?

1.) Quencher - rapid cooling of the flue gas
The hot flue gas is first cooled abruptly in a quencher via water injection. This optimal conditioning prepares the flue gas for the downstream wet scrubbing process. Depending on the temperature range, we utilize different materials:

• Up to 350 °C - quenchers made of glass-fiber reinforced plastic (FRP) for high chemical resistance
• Up to 1600 °C - quenchers made of graphite, ideal for extreme temperatures and aggressive flue gases
• Special materials are used for unique requirements 

2.) Packed-bed column - efficient absorption with sodium hydroxide
In the packed column, the pre-cleaned flue gas is treated in a countercurrent flow, with sodium hydroxide (caustic soda) dosed into the scrubbing solution. During this process, the pollutant gases react and are converted into water-soluble salts.

• Oxidizing pollutants such as chlorine (Cl₂) are reduced with sodium bisulfite or hydrogen peroxide and converted into harmless salts.
• An optional heat exchanger can be integrated to specifically lower the temperature of the purified flue gas.

Your benefits at a glance

• High efficiency ensuring the reliable removal of toxic pollutants
• Downstream component protection as the quencher effectively lowers the gas temperature
• Efficient neutralization with sodium hydroxide for conversion into stable salts
• Destruction of oxidizing components through safe reduction with sodium bisulfite or hydrogen peroxide
• Flexible and adaptable configurations suitable for widely varying flue gas compositions
• Compliance with statutory emission limits through sustainable pollutant abatement 

Three-stage flue gas cleaning

tailored solution for sewage sludge incineration plants

The incineration of sewage sludge generates flue gases with a complex pollutant composition, including acidic components, ammonia, heavy metals, and dust. Our three-stage flue gas cleaning system for sewage sludge incineration plants is typically installed downstream of a dust filter (optionally with a dry sorbent injection). The system combines a quencher with a two-stage packed-bed column consisting of an acidic stage and an alkaline stage to reliably comply with statutory emission limits.

How it works?

1.) Quencher - rapid cooling of the flue gas
The hot flue gas is first cooled abruptly in a quencher via water injection. This optimal conditioning prepares the flue gas for the downstream wet scrubbing process.

2.) Acidic scrubbing with packed-bed column - absorption with sulfuric acid or hydrochloric acid
In this packed bed column, the pre-cleaned flue gas is treated in a countercurrent flow, with sulfuric acid or hydrochloric acid dosed into the scrubbing solution. Ammonia (NH₃) reacts with the acid to form the corresponding ammonium salt, which is discharged in dissolved form as wastewater. Ionic mercury is also absorbed and chemically bound within this acidic stage.

3.) Alkaline scrubbing with packed-bed column - absorption with sodium hydroxide
In this packed column, the pre-cleaned flue gas is treated in a countercurrent flow, with sodium hydroxide (caustic soda) dosed into the scrubbing solution. During this process, the acidic gases react and are converted into water-soluble salts.

• Optional heat exchangers can be integrated to specifically lower the temperature of the purified flue gas.

• At low ammonia and mercury concentrations, separation within the quencher is sufficient, allowing the second stage to be omitted entirely. 

   

Your benefits at a glance

• Combined abatement of all relevant pollutants through a comprehensive three-stage cleaning process
• Downstream component protection as the quencher effectively lowers the gas temperature
• Effective ammonia and mercury removal via the dedicated acidic scrubbing stage
• High separation efficiency for acidic pollutants through the alkaline scrubbing stage
• Flexible and adaptable configurations suitable for widely varying flue gas compositions
• Compliance with statutory emission limits through the sustainable reduction of pollutants