Process for the desulphurization of flue gases from power plant boilers

摘要

In the process described, the raw gases (1) containing sulphur dioxide and, amongst others, chloride ions and residual oxygen are fed into a washing tower (3) where they are heated with a calcium- or magnesium-containing absorbent to oxidize the SO2 in the flue gas to SO42-. The washing suspension (7) which collects on the floor of the washing tower is partly recycled via the circuit (21) to the washing tower, and the desulphuration sludge (12) composed principally of calcium sulphate products is at least partly withdrawn from the circuit. The degree of thickening of the washing suspension is expressed, for a residual oxygen content in the raw gas of at least 2 vol.%, as the ratio of the chloride ion concentration of the aqueous phase of the washing suspension in mg/m3 to the chloride ion concentration of the emitted raw gas in mg/m3 and adjusted to a value of at least 10 000.