Type of presentation: Poster

MS-5-P-5947 Influence of use of plastic as fuel in cement clinker production on phase distribution: SEM as a QC-tool

Semsari Parapari S.¹, Mokhtari P.¹, Papila M.¹, Gülgün M. A.¹, Uysal Tüten P.²

¹Sabancı University, FENS and SUNUM, No:27, 34956, Orhanlı Tuzla, Istanbul, Turkey, ²AkçanSA, No:38, 34662, Altunizade, Üsküdar, Istanbul, Turkey

sorour@sabanciuniv.edu

Use of plastic wastes as alternative fuels in cement producing kilns is currently performed at industrial scale in many countries. Beside of the many advantageous points of disposing residual plastics with this method, there are also a few drawbacks. For example, incorporation of minor elements coming from the fuel during the firing may affect the clinker phase distribution. It has been suggested that these alterations in clinker phases have influences in the subsequent hydration products and thus, could change the strength development of the cement [1-4]. Therefore, investigating the effects of alternative fuels in microstructural evolution and chemical composition of cement clinker is of utmost importance.
In this study, a scanning electron microscope (JEOL JSM-6010LV) was used to investigate the morphology of the cement clinker phases with and without the usage of plastic wastes as the fuel in production process. Backscattered electron images (Fig. 1 and Fig. 2) showed the phase distribution in each of the two clinker specimens. Alite (3 CaO • SiO₂: C₃S) and Belite (2 CaO • SiO₂: C₂S) phases are recognizable because of their atomic weight differences. The average atomic weight of Alite is 228.31 g/mol and for Belite is 188.23 g/mol. A slight increase in Belite phase formation can be seen in the clinker produced with plastics as fuel. Also, it is obvious that the distribution of phases all over the clinker granules is different for two samples. These alterations in microstructure are probably due to the influence of impurity elements like Sulfur (S) and Chlorine (Cl) which are the result of combustion of plastic wastes.
Energy dispersive x-ray spectroscopy was utilized to perform the chemical analysis of the clinker phases. Fig. 3 illustrates EDS maps of Cl and S for the same region from the sample produced with plastic waste as fuel. Sulphur appeared to have concentrated preferentially to Belite phase whereas chlorine was concentrated in pore volume.
ImageJ software was used to measure the variation of Alite/Belite phase ratio in two samples. Fig. 4 shows that this ratio decreased from 5.15 to 3.13 for the samples without and with plastic waste fuel, respectively.
[1] Husillos Rodríguez, et al., (2013). The effect of using thermally dried sewage sludge as an alternative fuel on Portland cement clinker production. Journal of Cleaner Production, 52(0), 94-102.
[2]Shirasaka, T., Hanehara, S., & Uchikawa, H., (1996). Influence of six minor and trace elements in raw material on the composition and structure of clinker. World Cement, 27(3).
[3] Woo-Teck KWON et al., (2005). Effect of P2O5 and Chloride on clinkering reaction. Online Journal of Materials, 1.
[4] Lin, K.-L., Lin, D. F., & Luo, H. L. (2009). Journal of Hazardous Materials, 168(2–3), 1105-1110.

Fig. 1: Backscattered electron image of cement clinker prepared without plastic fuels.	Fig. 2: Backscattered electron image of cement clinker prepared with plastic fuels.
Fig. 3: Energy dispersive spectroscopy maps of Cl and S for the same region in cement clinker prepared with plastic fuel.	Fig. 4: Alite/Belite ratio calculated with ImageJ software for two clinker samples.