Wet cleaning systems are generally made use of after effective removal of dusts from the flue gas. The washing process allows achievement of good separation efficiencies for hydrogen chloride and sulphur dioxide as well as for particle-bound, vaporous heavy metals such as mercury and cadmium.At least two cleaning stages are required for effective flue gas scrubbing. The reason for this is that some pollutants (hydrochloric acid, hydrogen fluoride, heavy metals) require acid conditions (pH of around 1) for successful removal, while others (sulphur dioxide) require neutral conditions (pH around 7).
Incoming flue gases are led into a narrow steel container and cooled to 70°C. At this stage good cleaning results are already achieved for water soluble components. The scrubbers have a large baffle structure area, i.e. an enlarged surface area, which ensures that the flue gases are intensively mixed with the cleaning fluid. The waste water created in the process is concentrated by evaporation to allow safe removal of the pollutants contained.