Numerical Experimental Study On Influencing Factors And Influence Law Of Microwave Irradiation

Microwave technology for processing ore can be applied to microwave-assisted mechanical crushing to reduce the wear of equipment tools and improve efficiency,and promote the realization of a new "microwarve+mechanical rock breaking" method.The morphology,content,physical and mechanical parameters,rock types and irradiation distance of microwave-assisted rock breaking process are important factors affecting the irradiation effect.The study of the influence law and influence mechanism of these factors can promote the microwave irradiation effect and promote the practical application.In this paper,COMSOL is used to simulate the electromagnetic field,temperature field stress field and plastic zone under different mineral shapes,contents,physical and mechanical parameters,rock types and irradiation distances.The pyrite is used as the object.The effects of physical and mechanical factors such as dielectric constant,specific heat capacity,thermal conductivity,thermal expansion coefficient,cohesion and internal friction angle on microwave rock breaking effect and mechanism were studied.The values of basalt,limestone and granite under microwave irradiation were established.Simulation and analysis of the effects of different types of rocks on microwave irradiation,the main results are as follows:(1).Quantify the difference in shape between minerals and use the dimensionless unit roundness coef-ficient R to represent R ?(0,1,1 to represent the circle,and study the roundness coefficient and the irradiation effect under the same microwave irradiation environment.The relationship between the two studies shows that when the microwave environment is 1 kW and 2 s,the roundness coefficient is from 0.71 to 1,which will cause the thermal stress inside the mineral to decrease by 15%,and the plastic zone to account for 20%,and the gap It will increase as the irradiation time increases.(2).Establish a coupling model of the content and shape of strong absorbing minerals(pyrite).The results show that the content and shape have opposite effects on the irradiation effect.When the microwave environment is 1 kW,2 s,the content of pyrite increases from 4%to 8%,and the maximum stress of minerals increases by 30%,resulting in a 40%increase in the plasticity ratio inside the model.Pyrite is subj ect to The pressure is destroyed,the calcite is damaged by the pull,and the gap increases as the irradiation time increases.(3).The effects of six kinds of thermophysical parameters of minerals on the microwave irradiation effect of minerals were studied and analyzed.The results show that when the dielectric constant of minerals increases,the specific heat capacity decreases,the thermal conductivity decreases,and the thermal expansion coefficient increases.The decrease of the cohesive force and the decrease of the internal friction angle play a role in the corresponding process of the mineral failure mechanism,so that the crushing effect of the microwave irradiation becomes better.(4)This paper proposes a layout scheme for microwave irradiation on TBM.A simplified two-dimensional model is established on this scheme.Microwave irradiation is applied to basalt,granite and limestone.The research shows that under the same microwave irradiation environment,The fastest rate of temperature rise is granite,and the most tensile and compressive stress is basalt.The best irradiation results are basalt,granite and limestone.The reason for the above phenomenon is that the basalt has the highest dielectric constant,the granite has the lowest specific heat capacity,and the basalt has the largest thermal expansion coefficient.(5)In the proposed layout scheme of TBM microwave irradiation,the difference of the irradiation effect caused by the change of the irradiation distance of microwave is studied.The number of electric field peaks on the near-illuminated surface of the microwave generating port corresponds to the number of plastic zones.The plastic zone is narrow and deep.When the number is large,the plastic zone is wide and shallow.The optimal illumination distance within the study model was 16 cm.