Production of Portland cement using fluorine gypsum – hydrofluoric acid waste
Introduction. The purpose of the research was to explore the possibility of making PC400–D20 Portland cement, as the gypsum stone was replaced with fluorogypsum during the milling process. The study deals with physical and mechanical properties of Portland cement obtained by mixing milled Portland cement clinker, fly ash (consisting of nanosized particles of SiO2 and Al2O3) and sulphate additives (gypsum stone or fluorogypsum). Methods. In accordance with the quality indicators set by Russian State Standard GOST 4913–82 (EN 13279–2), Angarsk Electrolysis Chemical Plant (JSC AECP) fluorogypsum is significantly superior to the gypsum stone mined in the Nukutsky Gypsum Quarry (Irkutsk Region). The use of high-quality fluorite concentrate in the production of the hydrofluoric acid can be accounted for exceptional characteristics of fluorogypsum found at the sludge fields of JSC AECP. Results and Discussion. The composition of sludge fields of Angarsk Electrolysis Chemical Plant has been investigated. The quality of its main component, fluorogypsum, has been determined with accredited classification. The studies of chemical composition and physical properties of fluorogypsum deposited at the sludge fields of JSC AECP proved that it can serve as a first-grade raw material in accordance with Russian State Standard GOST4913–82 for the production of high-grade gypsum. Laboratory tests confirmed the practicability of using fluorogypsum as a substitute for natural gypsum stone in cement production process (when grinding cement clinker). A technology and parameters for the production of high-grade gypsum production from the fluorogypsum have been developed. Conclusions. Laboratory tests confirmed the possibility of using fluorogypsum as a setting regulator in cement production when grinding cement clinker. The exact quantity of fluorogypsum when grinding cement clinker was determined, which ensures the production of high-quality cement in compliance with Russian State Standard GOST 10187–85. The prospects of using fluorogypsum as a raw material for the production of high-quality gypsum as well as a wide range of building mixtures based on it has been identified.