A method of binding pollutants, such as sulfur dioxide, hydrochloric acid and/or hydrofluoric acid, in flue gas in one or more combustion plants. The method includes the steps of (a) combusting fuel in a furnace of the one or more combustion plants, resulting in the production of flue gas containing pollutants, (b) introducing at least one of calcium oxide, limestone and dolomite, for forming calcium oxide, into the furnace for binding pollutants in the flue gas in the furnace, (c) causing flue gas to flow through a flue gas channel and a venturi contact reactor which are dimensioned so to provide a desired division of the moistened ash of step (e) into a portion entrained with the flue gas and another portion falling down into the retention tank provided in the flue gas channel, to a dust separator, which separates ash containing unreacted calcium oxide from the flue gas, (d) conducting a portion of the ash separated from the flue gas in step (c) to a moistening device, which mixes water amounting up to 50% of the weight of the ash into the ash, (e) conducting ash moistened in step (d) to the contact reactor, to mix the moistened ash into the flue gas, (f) causing a first portion of the ash mixed into the flue gas in step (e) to (g) causing a second portion of the ash mixed into the flue gas in step (e) to fall down into the retention tank, (h) hydrating at least a portion of the calcium oxide in the ash to form calcium hydroxide in the retention tank, (i) causing the ash to dry out during the hydrating step (h) and (j) recycling at least a portion of the ash from the retention tank to at least one of the one or more combustion plants.