Purification of combustion plant flue gas containing hydrogen chloride, sulfur dioxide and mercury involves use of a wash fluid using ligands at ligand/mercury (II) ratio above a minimum value

摘要

Purification of combustion plant flue gas containing hydrogen chloride, sulfur dioxide and mercury by contacting with a wash fluid of pH 0-8 to dissolve the divalent mercury as Hg (II) compounds (at least containing mercuric chloride) by use of ligands (L) is such that the amount of L and dissolved Hg (II) in the wash fluid gives a ratio of the concentrations [L]/[Hg (II)] which is greater than a minimum value Mm. Independent claims are also included for a plant for the process having an individual washer (4) or at least one of two sequential washers (23, 24) with a take-off line connected to a unit (12 or 30) for mercury depletion, this unit having a recycling line (18) or recycling lines (35, 36).