Field application of non-blasting mechanized mining using high-frequency impact hammer in deep hard rock mine

A non-blasting mechanized mining experiment was carried out with a high-frequency impact hammer,and the daily mining performance was recorded to explore the applicability of the high-frequency impact hammer in deep hard rock mines.Before the field application,the scope of the excavation damage zone was monitored,and rock samples were obtained from the ore body to be mined to carry out a series of laboratory experiments.Field application results show that the overall excavation efficiency reaches 50.6 t/h,and the efficiency of pillar excavation after excavating stress relief slot reaches 158.2 t/h.The results indicate that the non-blasting mechanized mining using high-frequency impact hammer has a good application in deep hard rock mines,and the stress relief slot is conducive to mechanical excavation.In addition,the high-frequency impact hammer also exhibits the advantages of high utilization rate of labor hours,small lumpiness of spalling ore,little dust,and little excavation damage.Finally,according to the field application and laboratory experiment results,a non-blasting mechanized mining method for hard rock mines based on high-frequency impact hammer is proposed.

In situ observation of iron ore particle reduction above 1373K by confocal microscopy

The reduction behavior of single iron ore particle was investigated at high temperatures(above 1373 K)with CO/CO2 mixture.A high-temperature laser scanning confocal microscope for in situ observation and a vertical quenching furnace for offline characterization were designed.The reduction process of ore particles at different temperatures and in different atmospheres was videoed using the confocal microscope.In the temperature range studied,the transformation of Fe2O3-FeO firstly occurred in the ore particles,and there was no metallic iron until the ore particles completely converted to FeG phase.During the formation of FeO phase,its crystal lattice transforms along the most close-packed direction of its close-packed plane(111).The gangue-rich area firstly melts during reduction around 1573 K.Above 1673 K,the iron ore particles melt and form spherical liquid drops with metallic iron in the center.The gas-based reduction behavior of iron ore particles above 1373K is deduced and graphically presented.