Issue 37

Q. Like et alii, Frattura ed Integrità Strutturale, 37 (2016) 342-351; DOI: 10.3221/IGF-ESIS.37.45 343 S TATE OF THE ART orster et al. [10] ground and floated massive copper sulfide ores in Neves-Corvo Mine after microwave irradiation and found that microwave pre-irradiation can reduce Bond’s work index of minerals by 70% and significantly increase the single separation degree of useful minerals after ore grinding. Mamdouh Omran et al. [11] exposed iron ores to microwave irradiation and conducted electron microscopic scanning to ores. Their experiment confirmed that microwave heating resulted in microcracks developing easily between minerals and gangue compared with the traditional heating method. Guo Shenghui [12] and R.K. Amankwah et al. [13] exposed ilmenite and gold ores to microwave irradiation and discovered that microwave irradiation induced microcracks between useful minerals and gangue. These microcracks can effectively facilitate the separation of minerals and gangue. The tests showed that microwave irradiation can enhance the dissociation ability of minerals, and that microcracks in minerals are the root source of mineral dissociation capability. Determining temperature, stress, and strain distributions in minerals under microwave irradiation through tests can be difficult. Thus, the numerical approach has become the main method used in this field. Huijun Cui et al. [14] simulated the temperature rise curve of carbon-chromium powder using the finite element method (FEM). Qin Like et al. [15] studied temperature distribution in ore particles and its influencing factors. D.A.Jones [16] analyzed temperature-stress distribution in ore particles composed of pyrite and calcite and corresponding damages based on finite difference. A.Y. Ali [17] and Qin Like et al. [18, 19] examined the damages of galena-calcite boundaries in a microwave field based on the finite different method and explored the corresponding influencing factors. Yicai Wang [20] and Qin Like et al. [21] investigated temperature and stress distribution characteristics in monocrystal minerals using FEM. Ge Wang [22] and A.Y. Ali et al. [23] discussed the distribution characteristics of microcracks in minerals using the discrete element method (DEM). Interesting findings concerning microwave-assisted ore grinding and crushing have been obtained. However, the influence mechanism of mineral shape on microcrack distribution and development inside ores under microwave irradiation remains unknown. Therefore, the effects of mineral shapes on microcrack distribution and the different factors of ore particles composed of galena and calcite under microwave irradiation were studied from the mesoscropic perspective by using particle flow code (PFC) a commercial Discrete Element Method software from Itasca [24]. M ETHODOLOGY Computing method he energy balance equation can be expressed as follows: i v i q T q C x t         (1) where  q i is the heat flux vector (W/m 3 ) that can be calculated using Fourier’s law,  x i refers to the position coordinates,  q v is the amount of heat generated under microwave irradiation (W/m 3 ),  ρ refers to material density (kg/m 3 ),  C is the specific heat capacity of the material (J/kg °C),  q v is equal to P d . The heat quantity generated by an object under microwave irradiation is determined mainly by microwave frequency and electric field intensity. The amount of heat generated by an object per unit volume can be calculated using Eq. (2). " 2 2 d o r o P f E     (2) where P d is the power density of the microwave (W/m 3 ), which refers to the power required for the microwave to transform into heat energy, f is the diffusion frequency of the microwave (Hz), V T