Phase Transformation of FGD By-Product into Plaster Mould via Heat Treatment Process

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.

• Periodical: Key Engineering Materials (Volume 908)
• Pages: 672-677
• DOI: https://doi.org/10.4028/p-wfju6k
• Online since: January 2022
• Authors: Fatin Fatini Othman*, Banjuraizah Johar, Shing Fhan Khor, Nik Akmar Rejab, Suffi Irni Alias
• Keywords: Autoclave, FGD Sludge, Hemihydrate, Plaster of Paris (POP), X-Ray Diffraction (XRD)

References

[1] B. Szostakowski, P. Smitham, and W. S. Khan, Plaster of Paris–Short History of Casting and Injured Limb Immobilzation, Open Orthop. J., (2017) 11(1) 291–296.

DOI: 10.2174/1874325001711010291

[2] A. J. Lewry and J. Williamson, The setting of gypsum plaster - Part III The effect of additives and impurities, J. Mater. Sci., (1994) 29(23) 6085–6090.

DOI: 10.1007/bf00354546

[3] P. S. Valimbe and V. M. Malhotra, Effects of water content and temperature on the crystallization behavior of FGD scrubber sludge, Fuel, (2002) 81(10) 1297–1304.

DOI: 10.1016/s0016-2361(02)00045-5

[4] X. C. Qiao, C. S. Poon, and C. Cheeseman, Use of flue gas desulphurisation (FGD) waste and rejected fly ash in waste stabilization/solidification systems, Waste Manag., (2006) 26(2) 141–149.

DOI: 10.1016/j.wasman.2005.02.020

[5] C. Chandara, K. A. M. Azizli, Z. A. Ahmad, and E. Sakai, Use of waste gypsum to replace natural gypsum as set retarders in portland cement, Waste Manag., (2009) 29(5) 1675–1679.

DOI: 10.1016/j.wasman.2008.11.014

[6] I. Suárez-Ruiz and C. R. Ward, Coal Combustion, Appl. Coal Petrol., (2008) 85–117.

[7] I. Y. Elbeyli, E. M. Derun, J. Gülen, and S. Pişkin, Thermal analysis of borogypsum and its effects on the physical properties of Portland cement, Cem. Concr. Res., (2003) 33(11) 1729–1735.

DOI: 10.1016/s0008-8846(03)00110-8

[8] H. F. W. Taylor, Cement chemistry, (1997).

[9] F. A. Program, Care and Maintenance: Recommendations for Artwork in the Fine Arts Collection U.S. General Services Administration, (2005).

[10] A. P. P. et al. A. V. Eremin, Modern approach to X-Ray diffraction analysis of gypsum binders, Stroitel'nyematerialy, (2012) 62–66.

[11] A. M. Kilic and Ö. Kilic, The phase transition in natural gypsum, Asian J. Chem., (2007) 19(4) 3157–3168.