In the CANSOLV^® Multipollutant Absorption process, the absorption tower is divided into three sections separated by chimney trays: prescrubber, SO2 absorption and NOx-Mercury absorption sections. The prescrubber and SO2 absorption sections are identical to that of the CANSOLV^® SO2 Scrubbing System. The NOx-Mercury section operates with Cansolv Absorbent DN101™.  As the absorbent flows down this section of the tower, NOx and mercury are gradually absorbed. The rich solvent is then pumped to a regeneration tower where NOx is stripped from the solvent in much the same way as SO2.

In the regeneration step, a slipstream of solvent passes through an electrolysis cell to reverse the effects of oxidation and reactivate the solvent for further NOx capture. A combination of additives keeps oxidation rates low to minimize the duty of the electrolysis cell.

Regenerated NOx is reduced to nitrogen in a two phase gas burner. Captured mercury is removed by diverting a small slipstream of solvent to a resin packed column. The mercury absorption process is irreversible and the resin must be changed once or twice per year, depending on the rate of removal.

Cansolv Multipollutant Absorption at a glance:
SO2 removal to 99% or 10 ppmv NOx removal to 95% Elemental mercury to 90% with polishing Durable solvents stand up to oxidative environment Best-in-class heat consumption for regenerable scrubbing. Can be designed for high turndown or for wide fluctuations in pollutant concentrations No ammonia, no catalysts No solids / slurries

For very high elemental mercury removal, a polishing section may be added to the tower. In this section, a chemical oxidant is used to oxidize mercury and increase its solubility in aqueous solution. Residual NOx and SO2 will also be oxidized in this section pushing removal rates of these pollutants to very high levels.