a-Hemihydrate Gypsum from Flue Gas Desulphurization Gypsum
AbstractIn this work, properties of sulphate technogenic raw material – flue gas desulphurization (FGD) gypsum have been investigated in order to obtain α-hemihydrate gypsum as gypsum binding material. FGD gypsum is produced as a by-product during the process of desulphurization of exhaust gas emitted in power stations heated by fuel containing sulphur. It has been determined that α-hemihydrate gypsum can be obtained from FGD gypsum under hydrothermal conditions at 125°C and 130°C. The compressive strength of gypsum samples is 13 MPa–16 MPa after 2 h of hardening and it depends on temperature and time of isothermic curing. The compressive strength of the same samples in dry state is 49 MPa–67 MPa. SEM analysis data showed that the properties of α-hemihydrate gypsum significantly depend on the shape and size of its crystals: when crystals have near form to regular hexagonal – shaped prism with length and width ratio approx. of 4:1, the gypsum exhibits the high quality mechanical and physical properties.
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