Key Engineering Materials Vol. 908

Abstract: Flue Gas Desulfurization (FGD) is a waste incineration process commonly used to eliminate sulfur dioxide (SO₂) from flue gas power plants. FGD by-product recorded a rich gypsum content, also known as calcium sulfate dehydrate (CaSO₄•2H₂O), which has promising practical applications in plaster mould production. Plaster of Paris (POP) with a chemical composition of calcium sulfate hemihydrate (CaSO₄•0.5H₂O) is widely used in plaster mould production because of its quick setting and hardening upon moistened. Naturally, gypsum with 2 molecules of crystalline water can change to 1.5 molecules via the dehydration process. Various dehydration methods were conducted to transform FGD gypsum to hemihydrate. After undergoing different autoclave processes, the phase transition of FGD by-products was identified by X-ray diffraction (XRD) mode and compared with commercial POP. Chemical composition of FGD sludge contains a high amount of calcium oxide (CaO), sulfur trioxide (SO₃) and boron trioxide (B₂O₃), as well as other impurities such as fluorine (F), chlorine (Cl), and magnesium oxide (MgO). Based on phase analysis, sample H1 to H5 show the percentage of hemihdyrate is 1.5%, 19.7%, 2.8%, 1.2%, and 46.1%, respectively, after different dehydration methods.

Abstract: This paper presents the physical and chemical properties of fly ash obtained from two coal power plants; the Sultan Salahuddin Abdul Aziz Power Plant in Kapar, Selangor and Sultan Azlan Shah Power Plant in Manjung, Perak. Moisture and radionuclide contents, and chemical composition in the fly ash were characterized. It was found that moisture content for Kapar and Manjung fly ash were at 0.41% and 0.11%, respectively. XRF result showed that Kapar fly ash sample is of class C due to the total percentage of SiO2, Al2O3, and Fe2O3 being less than 70% while Manjung fly ash sample is of class F due to the total percentage of SiO2, Al2O3, and Fe2O3 of more than 70%. Gamma spectrometry analysis indicated presence of ²²⁶Ra, ²³²Th, and ⁴⁰K in the samples. These data can be used to establish a technical standpoint in supporting the development of radioactive waste immobilization technology using geopolymer material. This study is expected to benefit the nuclear fuel cycle specifically in conditioning of low-level radioactive waste produced in nuclear power plants.