Flue Gas Desulfurization Technology

Flue gas desulfurization (FGD) based on the so-called lime(stone)-gypsum-process is the classic absorption process for cost-effective separation of sulfuric oxides (SOx, i.e. SO² and SO³) from flue gases with medium to high flow rates or sulphur oxide loads.

Flue gas desulfurization plants based on the lime(stone)-gypsum process are typically used for

  • coal or heavy-oil powered industrial (thermal) power plants
  • waste and toxic waste incinerators
  • chemical or petrochemical processing plants
  • thermal processing facilities, e.g. calcination, sintering and roasting plants

Although the lime(stone)-gypsum FGD process belongs to the wet-scrubbing processes, most of the plants constructed by Steuler are operated without any waste water discharge.

The SOx is absorbed into the scrubber liquid and converted by absorbent into insoluble, reusable end-product gypsum. The gypsum, i.e. calcium sulfate of high purity, is then separated out of the process by filtration.

Cheap calcium-based compounds like limestone or lime are usually used as absorbent. In exceptional cases absorbents such as ZnO, Mg(OH)² or sea water can also be used. The end product gypsum can usually also be re-used industrially, e.g. in the construction industry. Additional savings can thus be made as no expensive disposal at toxic waste sites is necessary.

As a supplementary process for desulphurization (DeSOx) of flue gases, especially for lower gas flow rates, there are chemical scrubbers available, typically based on neutralization reactions with alkaline sorbents (e.g. NaOH, KOH, NaHCO³, ...).

Due to its leading position and technological competence in industrial corrosion protection and in the construction of pickling and etching plants, Steuler relies on corrosion-free thermoplastics for construction of scrubbers where highly aggressive media have to be dealt with. Flue gas scrubbers up to a transportable size and a tower diameter of 4 to 5 meters can be delivered by Steuler prefabricated and ready-to-install.

Larger and non-transportable flue gas scrubbers are usually manufactured on site using an innovative method of steel-reinforced concrete construction developed by Steuler, the mechanically anchored interior BEKAPLAST™ lining system.