Development of equipment and technology for pelletizing iron ore charge in production of pellets

Abstract

New possibilities of pelletizing process in pellet production can improve the production performance. The principles of induced nucleation in the pelletizing technique expand its technological capabilities. The technical indicators of the new pellet production technology and the physical parameters of wet pellets make it possible to increase the metallurgical properties of agglomerated raw materials. The presented technical diagrams reflect the production capabilities of induced nucleation in the processes of forming a sprayed layer (SL) of the charge and its division by various technical devices. The design features and technological modes of the developed technical schemes are implemented on a typical disc pelletizer. Experimental data obtained during implementation of the developed technological schemes make it possible to change the relative values of strength, mass and moisture content of the pellets during pelletizing of the iron ore charge. These parameters can be adjusted during loading of charge, its spraying onto the charge shell of the pelletizer, dividing the sprayed layer of the charge into nuclei and further pelletizing of the nuclei to form a pellet shell. An assessment of these technological schemes led to selection of the most effective solutions based on thermal power spraying of wet charge, taking into account its adhesion, material consumption and complexity of the equipment design. For practical use, we recommend a combined technological scheme for the production of pellets using the induced nucleation technology on the basis of SL formation of a single air-charge jet (ACJ) containing strengthening additives, on a pre-profiled skull and dividing the SL into nuclei by a conical drum equipped with a metal string. At the end of the technological cycle of pellet production, increased porosity with a high proportion of open pores is formed in the central embryonic part of the pellets. The pellets have a low moisture content (ΘW = 0.97) and a favorable pore structure. In the forecast, they require less energy consumption for their subsequent heat treatment. The technology makes it possible to produce pellets with the required and maximum strength (ΘП ≥ 1.0) 12 – 16 mm in size with higher productivity (ΘM = 0.68). In the course of experiments, it was found that the technology of preliminary nucleation has high reliability and versatility, and it can be easily introduced into the existing production.