Method for operating a heat-producing plant for burning chlorine-containing fuels

Method for operating a heat-producing plant of the type which comprises a chamber (2) for burning chlorine-containing fuels and a channel (3) connected with said chamber, in which a plurality of consecutive heat-transferring devices (5, 5′, 5″) are located, through which fluids, such as steam, water or air may pass with the purpose of being heated by hot flue gas which flows through the channel in the direction from the combustion chamber (2) towards an outlet (4), the flue gas being conditioned by addition of a sulphur-containing additive, which is injected into the flue-gas flow in a channel section located, on one hand downstream a combustion zone and, on the other hand, upstream and at a distance from that heat-transferring device (5) positioned downstream the combustion zone being the first to be hit by the flue gas, and which additive, after the entrance thereof in the flue-gas flow has the purpose of, during the way thereof to said first heat-transferring device, sulphating above all gaseous alkaline chlorides comprised in the flue gas, with the aim of reducing chlorine-induced corrosion on the heat-transferring devices characterized in that a compound chosen from the group:

• ammonium sulphate ((NH4)2SO4), ammonium bisulphate ((NH4)HSO4), ferrous sulphate (FeSO4), and sulphuric acid (H2SO4), is used as additive, in order to form reactive sulphur trioxide (SO3) at the occasion of entrance, which is injected in a quantity of at least 20 mg S/m3n (normal cubic metres) flue gas, at a point distanced from the combustion zone, where at least 90% of the fuel is burnt out, where the temperature of the flue gas is within the range of 1000 to 600° C.