Single pass dry

The Single-pass dry process is based on the dry injection of calcium hydroxide Ca(OH)2 into the flue gas before a filtering unit (bag filter or electrostatic precipitator) without any recirculation of the residues. The neutralisation reaction between the acid gas and the calcium hydroxide begins in the reactor or in the duct and continues in the filter. In case of in-duct injection without a reactor, a good mix between the reagent and the flue gas is necessary since the residence time is very short.

The performance of the single-pass dry process is influenced on one hand by the flue gas characteristics: temperature, pollutants concentration, humidity, etc. and on the other hand by the quality of the calcium hydroxide. For this reason Lhoist has developed a full range of reagents in order to adapt to the different gas conditions in order to decrease the amount of reagent consumed and residue produced.

 

Sorbacal SP Sorbacal SPS Sorbacal A Sorbacal HSH
       
Minsorb      

 

The single-pass dry process with lime is characterised by the following features:

Simplicity

  • Low investment cost
  • No preparation before injection: ready-to-use reagent

Residues

  • Dry residues easy to handle
  • No liquid effluents (from reagent fabrication to residues elimination)

High flexibility and compatibility

  • Large temperature and capacity ranges
  • Compatibility with every filtration mode
  • Compatibility with every additional treatment: DeNOx SCR/SNCR, DeDiox

Reduced maintenance:

  • No crusher
  • No additional conveyer
  • No buffer silo

Minimum foot print, since the reagent can be directly injected in the duct.
 

Options

The gases can be cooled before the dry injection of sorbent. Such a process is called the conditioned dry process or semi-dry process, when cooling is carried-out by spraying water.

The Sorbacal® SP is ideally suited to all kinds of dry processes like incinerators and to a growing number of new FGT applications such as the cement and glass industries. Sorbacal® SP makes dry processing a highly competitive solution.

Micro pollutants

The Single-pass dry process is also suited to the removal of micropollutants by injecting Powdered Activated Carbon (PAC), Lignite Coke or Minsorb® . Pollutant concerned : volatile heavy metal, typically mercury (Hg) and organics such as dioxins/furans (PCDD/PCDF), Polychlorinated Biphenyls (PCB) and Polycyclic Aromatic Hydrocarbon (PAH).

Non-volatile and semi-volatile heavy metals (Cr, Tl, As, Cd, Pb, etc.) settle on the ashes and are either concentrated ashes at the bottom or in the airbone ashes and are removed by the filter.

The sorbent can be injected separately from the calcium hydroxide or specific blends can be prepared combining acidic and micropollutant removal. Also see blended products.