Effects of fluorite tailings content on formation, properties and fluorine doping preferences of high-silica clinker: Experimental study and industrial verification

As limestone resources gradually deplete, the cement industry is facing the widespread use of low-grade high-silica limestone. This study explored the innovative use of low-fluorine fluorite tailings in the calcination process of raw meals containing high-silica limestone, employing advanced characterization techniques including FIB-TEM, BSEM, XPS, TG-DSC and HTM. The results revealed that fluorite tailings doping lowered the calcium carbonate decomposition temperature, increased the amount of carbonate decomposition, and reduced the liquid-phase temperature of clinker. In terms of the mineral composition of clinker, the incorporation of fluorite tailings reduced the f-CaO content, promoted the formation of C₃S and C₄AF, and hindered the formation of the C₃A. Notably, fluorine in the clinker mineral phase was unevenly distributed, predominantly enriching C₄AF, where F was found to substitute for O. In addition, the feasibility of using fluorite tailings in the production of clinker from high-silica limestone raw meals in a cement rotary kiln was verified. The results revealed that the addition of low-fluorine fluorite tailings increased the 28 d compressive strength of the clinker by 5.6 MPa, reduced standard coal emissions by more than 5 kg per ton of clinker, and resulted in nearly 20 yuan savings per ton of clinker. This research highlights the potential of fluorite tailings as a valuable resource in cement production, promoting both resource recycling and environmental sustainability.