Investigation of organic desulfurization additives affecting the calcium sulfate crystals formation

In the study, the optimal experimental conditions for gypsum crystals formation were 323K, 300rpm stirring speed. The major impurities of Mg2+, Al3+, and Fe3+ were found to inhibit calcium sulfate crystals formation. Fe3+ caused the strongest inhibition, followed by Mg2+ and Al3+. The influence of desulfurization additives on the gypsum crystals formation was explored with the properties of moisture content, particle size distribution and crystal morphology. The organic desulfurization additives of adipic acid, citric acid, sodium citrate and benzoic acid were investigated. Citric acid and sodium citrate were found to improve the quality of gypsum. Moisture contents were reduced by more than 50 %, gypsum particle sizes were respectively enlarged by 9.1 % and 22.8 %,induction time extend from 4.3 min (blank) to 5.3 min and 7.8 min, and crystal morphology trended to be thicker.