Process and reactor for producing alpha-hemihydrate gypsum from calcium sulphate dihydrate from flue gas desulphurisation plants operating by the wet scrubbing process with lime

摘要

In a process for producing alpha-hemihydrate gypsum from calcium sulphate dihydrate from flue gas desulphurisation plants operating by the wet scrubbing process with lime, a suspension, taken off from the flue gas desulphurisation plant and containing the calcium sulphate dihydrate, and, if appropriate, auxiliary substances, are continuously introduced from above into an upright tubular reactor, the suspension is heated in the reactor to a reaction temperature which is higher than 100 DEG C but lower than the boiling point, and finally an alpha-hemihydrate gypsum suspension is taken off from the bottom of the reactor. The liquid level in the reactor is adjusted by means of control instruments in the reactor outlet. The suspension is heated in the reactor by steam which is introduced into the suspension. The heating with steam is effected at a plurality of points uniformly distributed in the longitudinal direction. A reactor for carrying out the process is described. <IMAGE>