Cairo University (Giza, Egypt):

Khairy N., PhD Candidate;
El-Mofty S. E., Professor, PhD in Mining Engineering, Professor, mpm_cu@yahoo.com
El-Midany A. A., Professor, PhD in Mining Engineering, Professor

National Authority for Remote Sensing and Space Sciences (Cairo, Egypt):

El-Magd I. A., Head of Department, PhD in Civil Engineering, Professor

Oil shale grinding critically affects subsequent upgrading processes. It may affect the surface properties, the structure of the ground material, or even both. It depends mainly on the type of the material under study; therefore, it needs to be treated carefully. In this study, the effect of ceramic and steel balls as grinding media on oil shale size reduction was studied in terms of ball filling, expressed as the number of balls, ball diameter, and grinding time, taking the mean size (d50) of the ground product as an indicator. Although the weight of ceramic balls is approximately two-thirds that of steel balls, the product size obtained with ceramic balls is twice the size produced using steel balls. The resulting d50 was 0.8 mm for steel and 1.8 mm for ceramic balls, when using 17 balls, 4 cm ball size, and 30 minutes grinding time, which confirms the effectiveness of the load applied to the particle bed by steel balls, as compared to ceramic balls. The results indicate that the smallest particle size was obtained at higher ball filling, with coarser balls, and longer grinding time due to the higher collision probability with higher loading by coarser balls. In addition, the experimental data showed a good fit to the first-order breakage law for both ball sizes used.
The authors gratefully thank the Minerals Technology and Testing Lab of the Faculty of Engineering, Cairo University, for providing the help, guidance, and the needed equipment and instrumentation for conducting the experiments for this work.

1. Developments in petroleum science: Oil shale / Eds. Yen T. F., Chilingarian G. V. Elsevier Science Ltd, 1976. 292 p.
2. Tissot B. P., Welte D. H. Petroleum formation and occurrence. Springer Science & Business Media, 2013. 702 p.
3. El-Mofty S. E., Khairy N., El-Kammar A.M., El-Midany A. A. Effect of mineralogical composition and kerogen content on oil shale natural floatability. Energy Sources, Part A: Recovery, Utilization, and Environmental Effects. 2018. Vol. 40, Iss. 9. pp. 1144–1152.
4. Chang Z., Chu M., Zhang C., Bai S., Lin H., Ma L. Influence of inherent mineral matrix on the product yield and characterization from Huadian oil shale pyrolysis. Journal of Analytical and Applied Pyrolysis. 2018. Vol. 130. pp. 269–276.
5. Khairy N. Upgrading of oil shale by flotation: MSc thesis. Cairo University, Faculty of Engineering, 2013.
6. Meng Y., Tang L., Yan Y., Oladejo J., Jiang P., Wu T., Pang C. Effects of microwave-enhanced pretreatment on oil shale milling performance. Energy Procedia. 2019. Vol. 158. pp. 1712–1717.
7. Meng Y., Yan Y., Jiang P., Zhang M., Oladejo J., Wu T., Pang C. Investigation on breakage behaviour of oil shale with high grinding resistance: A comparison between microwave and conventional thermal processing. Chemical Engineering and Processing: Process Intensification. 2020. Vol. 151. DOI: 10.1016/j.cep.2020.107909.
8. Hussein N. T., El-Midany A. A. Size reduction of oil shale by attrition scrubbing and its effect on kerogen content. International Journal of Coal Preparation and Utilization. 2020. April. DOI: 10.1080/19392699.2020.1749054.
9. Hussein N. T., El-Midany A. A. H. Significance of conditioning pretreatment on enrichment and flotation of oil shale. Petroleum Science and Technology. 2020. Vol. 38, Iss. 10. pp. 713–722.
10. Cook T., Courtney T. The effects of ball size distribution on attritor efficiency. Metallurgical and Materials Transactions A. 1995. Vol. 26, Iss. 9. pp. 2389–2397.
11. Katubilwa F. M. Effect of ball size distribution on milling parameters: MSc thesis. University of the Witwatersrand, Faculty of Engineering and the Built Environment, 2008. 101 p.
12. Lameck N. N. S. Effects of grinding media shapes on ball mill performance: MSc thesis. University of the Witwatersrand, Faculty of Engineering and the Built Environment. 2005. 146 p.
13. Kotake N., Kuboki M., Kiya S., Kanda Y. Influence of dry and wet grinding conditions on fineness and shape of particle size distribution of product in a ball mill. Advanced Powder Technology. 2011. Vol. 22, Iss. 1. pp. 86–92.
14. Kuzev L., Penchev T., Karastoyanov D. New shape milling bodies for ball mills. Problems of Engineering Cybernetics and Robotics. 2009. Vol. 61. pp. 11–19.
15. Deniz V. Influence of interstitial filling on breakage kinetics of gypsum in ball mill. Advanced Powder Technology. 2011. Vol. 22, Iss. 4. pp. 512–517.
16. Deniz V. The effects of ball filling and ball diameter on kinetic breakage parameters of barite powder. Advanced Powder Technology. 2012. Vol. 23, Iss. 5. pp. 640–646.
17. Olejnik T. P. Kinetics of grinding ceramic bulk considering grinding media contact points. Physicochemical Problems of Mineral Processing. 2010. Vol. 44. pp. 187–194.
18. Olejnik T. P. Selected mineral materials grinding rate and its effect on product granulometric composition. Physicochemical Problems of Mineral Processing. 2013. Vol. 49. pp. 407–418.
19. Austin L. G. Introduction to the mathematical description of grinding as a rate process. Powder Technology. 1971. Vol. 5, Iss. 1. pp. 1–17.
20. Fuerstenau D. W., De A., Kapur P. C. Linear and nonlinear particle breakage processes in comminution systems. International Journal of Mineral Processing. 2004. Vol. 74. pp. S317–S327.
21. Austin L. G., Shoji K., Bell D. Rate equations for non-linear breakage in mills due to material effects. Powder Technology. 1982. Vol. 31, Iss. 1. pp. 127–133.
22. Tavares L. M., de Carvalho R. M. Modeling breakage rates of coarse particles in ball mills. Minerals Engineering. 2009. Vol. 22, Iss. 7–8. pp. 650–659.
23. Barani K., Balochi H. First-order and second-order breakage rate of coarse particles in ball mill grinding. Physicochemical Problems of Mineral Processing. 2016. Vol. 52. pp. 268–278.
24. Duda W. H. Cement data book. In 2 vol. Weisbaden, Berlin: Bauverlag GmbH, 1985.
25. Uçurum M., Güleç Ö., Cingitaş M. Wet grindability of calcite to ultra-fine sizes in conventional ball mill. Particulate Science and Technology. 2015. Vol. 33, Iss. 4. pp. 342–348.
26. Erdem A. S., Ergün Ş. L. The effect of ball size on breakage rate parameter in a pilot scale ball mill. Minerals Engineering. 2009. Vol. 22, Iss. 7–8. pp. 660–664.
27. Tüzün M. A., Loveday B. K., Hinde A. L. Effect of pin tip velocity, ball density and ball size on grinding kinetics in a stirred ball mill. International Journal of Mineral Processing. 1995. Vol. 43, Iss. 3–4. pp. 179–191.