Method of treating a gas system

A method of treating a gas stream containing an acid and solid particulates, the method comprising steps of:

• circulating an aqueous scrubbing liquor through an essentially closed loop comprising an acid removal unit for reducing acidity of the liquor;
• diverting a proportion of the circulating liquor away from the closed loop to a gas scrubbing unit;
• supplying the gas stream to the scrubbing unit for dissolution in the diverted liquor;
• returning the diverted liquor to the closed loop;
• monitoring the acidity of the circulating liquor at a location upstream of the acid removal unit within the closed loop;
• and
• controlling the reduction of the acidity of the liquor depending upon the monitored acidity to control a solubility of a solid component of the gas stream within the diverted liquor.

Apparatus for treating a gas stream containing an acid and solid particulates, comprising:

• a gas scrubbing unit;
• an essentially closed loop circulation system comprising a pump for circulating an aqueous scrubbing liquor around the closed loop, an electrochemical unit for reducing the acidity of the circulating liquor, and an exit port for diverting a proportion of the circulating liquor away from the closed loop to the gas scrubbing unit;
• the gas scrubbing unit having a first inlet for receiving the diverted liquor, a second inlet for receiving the gas stream for dissolution in the diverted liquor, and an outlet through which the diverted liquor is discharged from the scrubbing unit, the closed loop having an entry port for receiving liquor discharged from the scrubbing unit;
• a device for monitoring the acidity of the liquor at a location upstream of the electrochemical unit within the closed loop;
• and
• a controller for controlling the reduction of the acidity of the liquor depending upon a monitored concentration to control a solubility of a solid component of the gas stream within the diverted liquor.