Modification of FGD gypsum in hydrothermal mixed salt solution

Article type: Research Article

Authors: WU, Xiao-qin | WU, Zhong-biao

Affiliations: Department of Environmental Engineering, Zhejiang University, Hangzhou 310027, China | Department of Chemical Engineering, Wuhan University of Science and Technology, Wuhan 430081, China

Note: [] Corresponding author. E-mail: wys@dq.cern.ac.cn

Abstract: A novel utilization way of the sludge from wet calcium-based flue gas desulfurization (FGD) processes has been developed in this paper. This study focused on the conversion of the FGD gypsum into α-hemihydrate calcium sulfate by a hydrothermal salt solution method at atmospheric pressure. Experimental study has been carried out in a batch reactor. Qualitative and quantitative analyses were made by DSC/TG thermal analysis, SEM, XRD, metalloscope and chemical analysis. The experimental results showed that the modification of FGD gypsum was controlled by the dissolution and recrystallization mechanisms. With the introduction of FGD gypsum the salt solution was supersaturated, then crystal nucleus of α-hemihydrate calcium sulfate were produced in the solution. With the submicroscopic structure of FGD gypsum crystal changed, the crystal nucleus grew up into α-hemihydrate calcium sulfate crystals. Thus, the modification of FGD gypsum was fulfilled.

Keywords: FGD gypsum, modification, hydrothermal mixed salt solution, atmospheric pressure

Journal: Journal of Environmental Sciences, vol. 18, no. 1, pp. 170-175, 2006