Stability of ternesite and the production at scale of ternesite-based clinkers

A method to synthesize high-purity ternesite is presented and the importance of reaction volume is highlighted; a
brief description of the product morphology is also presented. Thermodynamic data for ternesite are derived and
the limits of ternesite stability are then explored. An upper temperature stability limit of ≈1290 °C at 1 atm is
determined; however, this temperature is dependent on the fugacity of the volatile components in the
atmosphere. Thermodynamic predictions confirm that belite and ternesite rich calcium sulfoaluminate clinkers
can be readily produced in a single stage process at temperatures above 1200 °C provided the atmosphere and
temperature are controlled. To demonstrate this control at larger scales, a conventional 7.4-meter rotary kiln has
been used to produce ≈20 kg of ternesite-containing clinkers. This demonstrates the usefulness of thermodynamic
modelling as it has enabled ternesite-based clinkers to be readily produced at scale in a single-stage
process using existing equipment without major modifications.