Process for desulphurization of flue gas

A process for desulphurization of flue gas generated during the combustion of sulphur-containing fuel in a combustion furnace, said process comprising the steps of

• adding only outside of said combustion furnace fresh alkaline absorption agent selected from among oxides and hydroxides of calcium, magnesium and the alkali metals, to flue gas in a flue gas channel leading from said combustion furnace for desulphurization of the flue gas outside of said combustion furnace,
• separating from the flue gas the reaction product formed by said adding of fresh alkaline absorption agent,
• said addition of said absorption agent is done in dry form at an insert point after adjustment by a heat exchanger means of the relative water content of the flue gas by adjustment of the temperature of the flue gas so that the flue gas temperature becomes 5.degree.-50.degree. above the dewpoint,
• additional fresh, absorption agent is added in dry form at a secondary point which, in the flow direction of the flue gas, is before said heat exchanger,
• said absorption agent is added in molar excess, with respect to S in the flue gas, and
• a mixture containing reaction product and unreacted absorption agent after separation from the flue gas is recirculated for mixture with the dewpoint-adjusted flue gas, said mixture, containing reaction product and unreacted absorption agent, is recirculated to another insert point, which in the flow direction of the flue gas lies before said insert point.