Production of belite calcium sulfoaluminate cement using sulfur as a fuel and as a source of clinker sulfur trioxide: pilot kiln trial Theodore Hanein PhD Student, School of Engineering, University of Aberdeen, Aberdeen, UK Isabel Galan Research Fellow, Department of Chemistry, University of Aberdeen, Aberdeen, UK Ammar Elhoweris PhD Student, Department of Chemistry, University of Aberdeen, Aberdeen, UK Sameer Khare Research Fellow, School of Engineering, University of Aberdeen, Aberdeen, UK Solon Skalamprinos PhD Student, Department of Chemistry, University of Aberdeen, Aberdeen, UK Gabriel Jen Research Fellow, School of Engineering, University of Aberdeen, Aberdeen, UK Mark Whittaker Research Fellow, School of Engineering, University of Aberdeen, Aberdeen, UK Mohammed S. Imbabi Senior Lecturer, School of Engineering, University of Aberdeen, Aberdeen, UK Frederik P. Glasser Chair in Chemistry, Department of Chemistry, University of Aberdeen, Aberdeen, UK Marcus N. Bannerman Lecturer, School of Engineering, University of Aberdeen, Aberdeen, UK (corresponding author: m.campbellbannerman@abdn.ac.uk) 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. Introduction Belite calcium sulfoaluminate (b-C$A) cements are currently under rapid development and offer a number of advantages over Portland cement (Alvarez-Pinazzo et al., 2012; Chen and Juenger, 2011; Gartner, 2004; Hasanbeigi et al., 2012; Juenger et al., 2011; Li et al., 2007). These b-C$A cements are an attrac- tive alternative to Portland cement due to the lower carbon dioxide (CO 2 ) emissions associated with their production. The reduction in carbon dioxide is achieved through a lower clinker- ing temperature and a reduced lime factor relative to Portland cement (Hanein et al., 2016). A key characteristic of b-C$A cements is that they contain ye’elimite (C 4 A 3 $) (the cement clinker phases used in this paper are written in cement notation, as shown in Table 1). The sulfur necessary to form phases such as ye’elimite is conventionally introduced into the raw feed as gypsum and/or anhydrite; however, further economies of produc- tion can be achieved by the partial substitution of carbon-based fuels by sulfur (Hanein et al., 2016). Sulfur is naturally available in ‘sour’ fuels and also in its elemental form as a by-product of the desulfurisation of ‘sour’ oil and natural gas. Although using calcium sulfate (CaSO 4 ) (as opposed to sulfur) as a raw material provides a lower raw material ‘carbon footprint’, the generation of calcium sulfate (when created as a by-product of the energy industry) typically requires the de-carbonation of limestone and thus it may have some inherent carbon dioxide emissions associ- ated with its production; nonetheless, utilising sulfur products to form reactive cement clinker phases is still highly effective in sig- nificantly reducing the environmental burden caused by the pro- duction of cement due to the high heat of combustion of sulfur. A recent study by the authors has demonstrated that the carbon dioxide emitted by calcination of the raw material is increased by up to 15% over using calcium sulfate as a raw feed; however, more than 50% of the theoretical heat of clinkerisation can be supplied by the sulfur combustion for high-ye’elimite clinkers 643 Advances in Cement Research Volume 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. Advances in Cement Research, 2016, 28(10), 643–653 http://dx.doi.org/10.1680/jadcr.16.00018 Paper 1600018 Received 20/02/2016; revised 28/06/2016; accepted 31/08/2016 Published online ahead of print 11/10/2016 Keywords: clinkering/clinkering reactions/C2S/sulfate-based cements ICE Publishing: All rights reserved Downloaded by [ University of Aberdeen] on [09/11/16]. Copyright © ICE Publishing, all rights reserved.