Issue 37

Q. Like et alii, Frattura ed Integrità Strutturale, 37 (2016) 342-351; DOI: 10.3221/IGF-ESIS.37.45 350 C ONCLUSIONS his paper discusses the crack distribution and development in mineral particles composed of galena and calcite under high and low microwave powers using DEM and a 2D plane strain model. The main conclusions are as follows: (1). Microcracks formed in ores are mainly tensile cracks regardless of the level of microwave power and mineral shapes, which are accompanied with few shear cracks. Distribution characteristics and positions indicate that microcracks can be divided into diffused cracks in calcite, calcite-galena interface cracks, and cracks in galena. The first two types of cracks represent the root mechanism for microwave-assisted ore crushing and grinding. (2). Under low microwave power, the total number of microcracks, number of microcracks in calcite, number of microcracks in galena, and boundary damage rate are positively correlated with irradiation time. However, their growth rates are negatively correlated. At different irradiation times, the number of microcracks in the different shapes of galena differs significantly. Circular galena had the least microcracks. (3). Under high microwave power, the number of microcracks in the different shapes of galena display a similar growth law with irradiation time. Microcrack growth curve can be divided into two stages. The first stage achieves a higher growth rate than the second one. The numbers of microcracks in different shapes of galena are similar at different irradiation time in the first stage. However, the number of microcracks in the circular galena is significantly smaller than those in other shapes of minerals. (4). This study suggests the use of high-powered microwave for mineral dissociation and the first growth stage of boundary damage rate as the optimum irradiation time. The numbers of microcracks in different shapes of minerals and their variation laws are basically the same within this optimum irradiation time. The number of cracks in gangue and the boundary damage rate remains unchanged after exceeding the optimum irradiation time. A CKNOWLEDGEMENTS his work was supported by the Foundation of Shaanxi Educational Committee (15JK1471), the China Postdoctoral Science Foundation (2015M572580), and the National Natural Science Foundation of China (No. 51174159). R EFERENCES [1] Qinhan, J., Microwave chemistry. Science Press, Beijing, (1990) 214-216. [2] Lubikowski, K., Seebeck phenomenon, calculation method comparison. Journal of Power Technologies, 95(1) (2015) 63-67. [3] Islam, M. M., Design of a microstrip antenna on duroid 5870 substrate material for ku and k-band applications. Tehnicki Vjesnik, 6(2) (2013) 71-77. [4] Kolarz, C., Korol, K. B. et al., Model of eco-efficiency assessment of mining production processes. Archives of Mining Sciences, 1(2) (2015) 477-482. [5] Ghazala, Y., Almas, H., Saira, I., Pollutants generated from pharmaceutical processes and microwave assisted synthesis as possible solution for their reduction - A mini review. Nature Environment and Pollution Technology, 11(1) (2012) 29-36. [6] Kingman, S. W., Vorster, W., Rowson, N. A., The influence of mineralogy on microwave assisted grinding. Minerals engineering, 22 (1) (2015) 160-163. [7] Liu, Q., Xiong, Y., Research on application mechanism of microwave in iron ores selective grounding. Yunnan Metallurgy, 6 (3) (1997) 25-28. [8] Kingman, S.W., Rowson, N.A., Microwave treatment of minerals- a review. Minerals Engineering, 11(11) (1998)1081-1087. [9] Kingman, S. W., Jackson, K., Recent developments in microwave assisted combination. International Journal of Mineral Processing, 74 (2004) 71-83. [10] Vorster, W., Rowson, N. A., Kingman, S. W., The effect of microwave radiation upon the processing of Neves- Corvo copper ore. International journal of mineral processing, 63( 3) (2001) 29-44. T T