a-Hemihydrate Gypsum from Flue Gas Desulphurization Gypsum
Keywords:flue gas desulphurization (FGD) gypsum α-hemihydrate gypsum, calcium sulphate dihydrate, dehydration, hydration
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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