Technology of Electromagnetic Dynamic Crushing and Milling

Abstract

The technology of electromagnetic dynamic breakdown allows to effectively carry out crushing and milling of metallic and non-metallic materials, including rocks, to a given size with simultaneous removal of part of the total moisture and foreign objects. The reduction ratio of crushing and milling per stage can exceed 3,000 times, which is many times higher than the best performance of mechanical crushers and mills. The minimum attained size of particles during milling is 0.5 microns. A pilot version of a crushing and milling unit for metallic and non-metallic materials with simultaneous removal of part of the moisture and foreign objects with the capacity of 2.0 tonnes per hour was used for milling the iron ore concentrate (IOC) of Kovdorskiy GOK, which contains more than 65.0% of +40 micron particle size and less than 14.0% of 20-40 micron particle size, we used. The dimensions of the crushing and milling unit are 4,500x2,300x3,200 mm and the total weight is 25.0 tonnes. No special base plates or foundations for the operation of the unit are required. Measurements of the particle size of magnetite before and after milling were taken using the technology of applying diffraction of laser radiation in a convergent laser beam patented by FRITSCH, Germany. At present, this technology is the international standard for quick and reliable determination of the particle size of any substance. The measurements were taken on a multi-purpose ANALYSETTE 22 MicroTec plus laser device with a range of measurements of 0.08-2000 microns. Measurement results for each sample were automatically printed as files with appropriate names. Each file contained information on the size range of the sample in a graphic and tabular form. The integral values of d20, d40, d80 and d99.9 for each sample mean that d20 is the maximum particle size expressed in sample microns, whose total content does not exceed 20% of the total quantity of all particles in a sample. Thus, d40, d80 and d99.9 are the maximum particle sizes (in microns) of a sample whose total content does not exceed 40%, 80% and 99.9%, respectively, of the total quantity of all particles in a measured sample. In terms of particle size distribution, the non-milled magnetite in the initial sample whose data represents the weighted average values of several tests, contained less than 35% of particles of less than 40 microns and 15% of particles of more than 150 microns in size at the weighted average particle size of 79.8 microns. In terms of particle size distribution in the test magnetite sample which had been milled once, whose data represents the weighted average values of several tests, the content of particles of less than 40 microns was 78.8%, while the content of particles of 40-100 microns was up to 22% at the weighted average size of particles of 42.4 microns. Thus, the IOC of Kovdorskiy GOK was milled in a single stage to the standard sizes using a pilot crushing and milling unit for metallic and non-metallic materials with a capacity of 2.0 tonnes per hour. The lack of mechanical impact mills reduces the wear of steel structures of the unit manifold. The specific power consumption is up to 1.0 kW*hour per tonne. Safe operation of the unit is ensured in the range of temperatures from -50°C to +50°C. The lack of any foundations and feasibility of installing the unit outside makes it indispensable for breaking down metallic and non-metallic materials to the required particle size distribution under any natural and climatic conditions.