ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 24, Number 4
JKCSEZ 24(4)
August 20, 1980 

A domestic phosphogypsum was calcined in a batch type fluidized bed reactor at various reaction temperatures ranging 90∼180℃ without and with an alkaline additive amounting up to 5% of gypsum, and physical properties of the resultant products were compared following their characterization by X-ray diffraction pattern and DTA. It has been found that dehydration reactions were uniformly carried out in the fluidized bed reactor and only hemihydrate was obtained at 90℃ whereas at higher temperatures dehydration reaction progressed further. When gypsum was charged to the reactor preheated at over 140℃, a considerable degree of dehydration occurred before the reactant reached the initially set reactor temperature and in particular, at over 160℃ most of dehydration reaction was performed prior to the present reactor temperature. However, it has been found that gypsum mostly transforms into hemihydrate around the reactant temperature of 140℃ while transformation into anhydrite mostly occurs around 160℃. When calcium hydroxide was added to gypsum in the reactor, the optimum physical properties of the calcined product were obtained at the weight ratio of Ca(OH2)/P2O5 = 3.2.