Insight into Influence of Glycerol on Preparing α-CaSO4·1/2H2O from Flue Gas Desulfurization Gypsum in Glycerol–Water Solutions with Succinic Acid and NaCl

The conversion of CaSO4·2H2O (DH) to CaSO4·1/2H2O (HH) was facilitated by increasing glycerol content from 55% to 85% in glycerol–water mixtures; the average length and diameter of produced α-HH crystals decreased from 60.97 to 7.21 μm and from 15.21 to 5.17 μm, respectively, resulting in a decrease in the average aspect ratio from 4.06 to 1.41. The phase transformation was reduced dramatically from 30 to 3 h. As glycerol content increased in the mixtures, an increase in α-HH maximal relative supersaturation and decrease of ion diffusion rate were hypothesized as explanations for the morphology change in the alpha-hemihydrate (α-HH) produced. The kinematic feasibility of FGD gypsum transition to α-HH in the mixed solutions with the increase of glycerol should also be attributed to the enhancement of maximal relative supersaturation for α-HH precipitation.