Abstract: Fluidized bed reactor and a process for the operation of a circulating, fluidized bed reactor, by which a solid particle material, in particular carbonaceous fuel, is introduced into the lower part of the reactor and is formed to a fast bed by a fluidization gas containing a gaseous reactant material, in particular oxygen, introduced into the reactor bottom, while non-reacted particles are removed from the reactor top and recirculated to the bed. By removing a predetermined fraction of the solid particle material in the reactor from at least one site positioned below the reactor top, subjecting it to thermal treatment and recirculating it to at least one other, lower positioned site of the bed, enhanced possibilities for process optimalization are achieved.

Abstract: In a process for purification, in particular desulphurization, of flue gas from the combustion of sulphur-containing fuel in a combustion furnace, fresh, alkaline absorption agent selected among oxides and hydroxides of calcium, magnesium and the alkai metals, is added in the flue gas channel from the combustion furnace, and the formed reaction product is separated from the flue gas.By adding the absorption agent drily after adjusting the water-dewpoint of the flue gas and/or the temperature of the flue gas so that the distance between dewpoint temperature and flue gas temperature is 5.degree.-50.degree. C., preferably 10.degree.-20.degree. C., a very effective desulphurization is obtained.

Abstract: Fluidized bed reactor and a process for the operation of a circulating, fluidized bed reactor, by which a solid particle material, in particular carbonaceous fuel, is introduced into the lower part of the reactor and is formed to a fast bed by a fluidization gas containing a gaseous reactant material, in particular oxygen, introduced into the reactor bottom, while non-reacted particles are removed from the reactor top and recirculated to the bed. By removing a predetermined fraction of the solid particle material in the reactor from at least one site positioned below the reactor top, subjecting it to thermal treatment and recirculating it to at least one other, lower positioned site of the bed, enhanced possibilities for process optimalization are achieved.