Studies in the carbothermic reduction of phosphogypsum

Thermogravimetric studies of the synthesis of cas from gypsum, CaSo4·2H2O and phosphogypsum

“…Gypsum and phosphogypsum are also reacted with different types of carbon, such as coke, coal, charcoal, wood charcoal, etc. For the maximum conversion to CaS, the molar ratio CaSO4:C should be a minimum of 1:2 [6]. Again the nature of the products varies.…”

“…One disadvantage is that a large excess of gaseous reductants is required, with no oxygen at all present [6]. The nature of the solid and gaseous products vary depending on the reaction conditions and reducing gases, making the process difficult to control.…”

“…The main chemical use of gypsum and phosphogypsum is in the manufacture of sulphuric acid [6]. The first step involves the decomposition of calcium sulphate to cal- [6,7]. During the next steps calcium sulphide is used as main reagent to obtain sulphuric acid.…”

“…While some byproduct gypsum from forced oxidation flue gas desulphurization systems is being converted into wallboard, the supply of waste gypsum greatly exceeds the demand [5]. The main chemical use of gypsum and phosphogypsum is in the manufacture of sulphuric acid [6]. The first step involves the decomposition of calcium sulphate to cal- [6,7].…”

Thermodynamic study of phosphogypsum decomposition by sulfur

“…Carbon is the traditional reductant for phosphogypsum decomposition [8][9][10][11]. This process has been studied since Müler and Kühne discovered that coke could lower the decomposition temperature and increase the decomposition rate of gypsum [8].…”