A process for cleaning a flue gas stream (10) in a flue gas cleaning system (2) to remove contaminants such as particulates and acidic components therefrom. The process includes admitting the flue gas stream to a particle collection device (18) to deposit the contaminants onto collector surfaces (19) therein, contacting the collector surfaces (19) with a wash water (20) to remove the contaminants therefrom, and discharging the wash water from the particle collection device (18) to a position downstream of the particle collection device (18). The discharged wash water is neutralized and circulated within the flue gas cleaning system (2).