Experimental Study Of Microwave Assisted Grinding Of Huimin Iron Ore

After the processing of exploitation of iron ore resource, grinding is the last process to achieve full dissociation before smelting. The process of gringding ore decide the capacity of concentration plant, effecting the index of beneficiation. The quality of grinding is directly concerned for the plant's technical and econ-omic indicators. The energy consumption of grinding is great, grinding account for more than 60% of the plant total investment,50-60% of plant total power consumption, more than 40% of the production and management cost. The energy of grinding process is dissipated mainly in heat, sound, friction etc.,only 1% of energy is used for crushing to impel the broken of bond between the mineral particles and the generation of new surface, energy efficiency is very low.In order to reduce energy consumption and realize the economic value of lean ore, the researchers of various countries have done a lot of studies. Along them, heat-treatment as a pretreatment process to change the mechanical properties of the ore and creat favorable conditions for grinding.With the characteristics of rapid heating, selective heating and overall heating, microwave has become the hotspot of study in recent years.Under the premise of a wide range access to paper information at home and abroad, Huimin oxide ore is taken as the raw materials in this paper. Based on the studies of the mainly chemical composition, the chemical phase and apparent morphology of ore, the method of microwave heating is used to pretreat the raw ore, resulting in a large number of iternal cracks and other mineral deficiencies, so as to create favorable conditions for grinding process.Studies of the heating characteristic of ore under microwave treatment is carring out to prove the effects of the position of thermocouple, mineral fragment- ation, quality, humidity, microwave power, heating time and atc. to the heating of the mineral. Analysis and investigation of the change of the mineral strength (Mechanical test machine), apparent morphology(SEM) and porosity of the mineral after microwave processing are carried out to explain the effects of microwave processing to the mechanical properties of ore block. Taking grinding experiments of mineral before and after microwave processing, the auxiliary function of microwaving processing to the size composition, distribution, fineness and yield of grinding products is found out and the change of grindability of ore after microwave treatment is verified. The effect of water-quenching to the grinding of ore is investigated also. Preliminary studied the mechanism of microwave-assisted grinding ores, determined the main factors which effect the results of microwave-assisted grinding, and provided an effective pre-treatment technology to the comprehensive utilization of mineral resources in the region.Research indicates that, ore mineral presents a stage-heating under microwave irradiation, it can be heated to above 400℃within 60 seconds and 800℃within 180 seconds unter the microwave power of 1500W. Once increase the microwave power, the heating temperature becomes higher, but the energy efficiency is not necessarily increasing; the amount of material and mineral block significantly affect the heating process, a matching relationship exists among the microwave power, the amount of material, mineral blocks degrees. In the experimental range, with power of 2000 W, ore fragmentation of 10-20mm, amount of material of 150g can achieve best heating results.A large amount grain boundary fractures generated inside the mineral ore after microwave treatment, the internal defects of ore increased significantly, which makes the grinding process more likely to occur. With the extension of treat time, the internal crack continues to expand, but not produce many new micro-cracks which makes a slow supporting role to the grinding of ore, until the ore burst to generate new surface, Significant effect the grinding or ore again. Thus, while the extension of heating time can increase the heating temperature of the ore, but not significantly change the grinding efficiency all the time.The fragmentation rate of Huimin iron ore is up to 46% and the strength reduction up to more than 50%, grindability increased 11.34%, porosity increased 24.04%, grinding product of-200 mesh grew more than 7.3%, particle size distribution is more centralization and with less Coarse-grained and over crushed of grinding product.Water quenching promote the grinding of minerals, making a increase of 4%-8% to the grinding products of-200 mesh. Cooling with water after micro-wave heating can induce more material damage, interrupt the healing process of materials,the subsequent contraction make the materials to further damage.Microwave heating is a relatively new mineral pretreatment process which can improve the grinding efficiency and reduce grinding energy consumption, providing a possible pre-treatment technology to the comprehensive utilization of Huimin iron ore.