Drying phosphate gypsum - without escape of fluorine by adding calcium oxide/hydroxide/carbonate

摘要

Contamination of the atmosphere and corrosion of the drying apparatus are prevented by adding to gypsum a minor amt. of CaO, Ca(OH)2 or CaCO3, and heating the mixture at 200-600 degrees C. The presence of a small amt. of fluorine (e.g. 0.27 wt %) improves the quality of the subsequently produced Portland cement.