Effect of calcination on properties of calcined gypsum prepared from desulphurization gypsum with potassium aluminum sulfate
To solve the problem of low utilization rate of flue gas desulphurization gypsum(FGD gypsum)and improve its added-value utilization,calcined gypsum was prepared by calcining FGD gypsum added with potassium aluminum sulfate(KAS,mass ratio of 0,0.3％,0.6％,1.0％)at atmospheric pressure.The effects of calcination temperature and KAS content on the properties and the morphology of calcined gypsum were mainly studied.The results showed that the proper calcination temperature could improve the properties of calcined gypsum.However,excessive temperature could generate more cracks on the surface of calcined gypsum,and the properties were subsequently decreased.The addition of appropriate amount of KAS not only improved the crystallinity of calcined gypsum,but also promoted the growth of new phase dihydrate gypsum(DH)along the b-axis after hydration,delayed the growth along the c-axis,and significantly reduced the length-diameter ratio of DH crystals,which could promote the densification of gypsum sclerotium,resulting in the increase of strength.As 0.3％KAS was added into FGD gypsum and calcined at 170℃ for 2 h,the performance of the prepared calcined gypsum was the best.The initial and final setting time was 11.5 min and 14 min,respectively,the 2 h flexural and compressive strength were 3.40 MPa and 9.23 MPa,respectively,and the dried flexural and compressive strengths were 6.70 MPa and 21.82 MPa,respectively,which met the 3.0 grade requirements of the GB/T 9776-2022"Calcined Gypsum".Compared with the blank group,the 2 h flexural strength was increased by 26％and the 2 h compressive strength was increased by 40％.
万方数据
维普
