A pilot-scale trial was undertaken in a 7•4 m kiln to demonstrate the production of belite calcium sulfoaluminate cement clinker using sulfur as a raw feed. The sulfur was introduced in its elemental form as fuel to the burner, thus partially offsetting fuel costs while providing sulfur trioxide which is incorporated in the clinker. The study demonstrates that sulfur trioxide is readily sequestered into cement clinker in a standard rotary kiln; however, some scrubbing of the exit gas may still be required. As the products of scrubbing (anhydrite or gypsum) are usually required to optimise the cement formulation, the recovered sulfur product can find an immediate use in the final cement product. This trial demonstrates the successful production of targeted belite calcium sulfoaluminate clinkers at scale using sulfur as both a fuel and sulfur trioxide source.
Advances in Cement ResearchVolume 28 Issue 10 Production of belite calcium sulfoaluminate cement using sulfur as a fuel and as a source of clinker sulfur trioxide: pilot kiln trial Hanein, Galan, Elhoweris et al.
Calcium sulfoaluminate clinkers containing ye'elimite (Ca 4 Al 6 O 12 (SO 4 )) and ternesite (Ca 5 (SiO 4 ) 2 SO 4 ) are being widely investigated as components of calcium sulfoaluminate cement clinkers. These may become low energy replacements for Portland cement. Conditional thermodynamic data for ye'elimite and ternesite (enthalpy of formation) have been determined experimentally using a combination of techniques: isothermal conduction calorimetry, X-ray powder diffraction and thermogravimetric analysis. The enthalpies of formation of ye'elimite and ternesite at 25°C were determined to be -8523 and -5993 kJ mol -1 , respectively.
Calcium sulfoaluminate clinker produced through a previously described novel production process, generating further economies of carbon emission minimization and sulfur use efficiency, is tested for performance as a cementitious binder. The reactivity levels of major phases, including ye'elimite, two polymorphs of belite and anhydrite are found to produce a viable product characterized by rapid hydration. Through investigation, the reactivity is linked to the unique distribution of crystalline phases present within cement grains. It is inferred that both microstructure and mineralogy are responsible for the undesirable set behaviour encountered. The causality of this problem is further investigated and determined to be a consequence of the intrinsic anhydrite component for which remediation solutions are described. The resultant mortar compression strengths are determined for the subject cement in order to characterize its potential in relation to ordinary Portland cement.
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