TECHNOLOGY OF RAW MATERIAL ENRICHMENT OF INHOMOGENEOUS CARBONATE DEPOSITS AND EVALUATION OF ITS ENERGY EFFICIENCY
Authors:   Dnipro University of Technology, Ukraine, Dreshpak Oleksandr , Dreshpak Nataliia ,   Dnipro University of Technology, Ukraine, Vypanasenko Stanislav ,   Dnipro University of Technology, Ukraine
Published: February 2022

The article presents the results of solving the urgent scientific and practical problem of establishing regularities connecting the indicators of the efficiency of enrichment and classification of raw materials of heterogeneous limestone deposits with its initial characteristics, technological and design parameters of the classification equipment, substantiating rational screening modes on this basis. An assessment of the energy efficiency of the proposed technical solutions is given. The research was carried out at Dnipro University of Technology (Ukraine, Dnipro). Technological lines for dry processing of limestone raw materials, which are used in quarries, ensure the production of marketable products of acceptable quality only for large grades of crushed stone in low humidity conditions. Small grades of crushed stone are not used and are sent to the dump. There is a need to improve the existing process of classification and enrichment of raw materials in order to improve the quality of the final product and expand, on this basis, the fractional com 195 position of commercial crushed stone, which complies with the requirements of state standards. The proposed concept of enrichment of raw materials of heterogeneous carbonate deposits consists in the forced separation of clay coatings from pieces of rock, followed by highly efficient screening of limestone in quarry conditions. The implementation of the concept provides for the use of a roller-finger screen, which provides high performance indicators at high material moisture. New analytical dependencies have been obtained linking the indicators of the efficiency of limestone concentration with the results of the granulometric and chemical analyses of the feedstock, the efficiency of its screening. On their basis, a mathematical model has been created that allows, with a limited amount of experimental data, to predict the achieved enrichment efficiency indicators, taking into account the characteristics of the classification devices used. It is shown that the dependence of the indicator of the efficiency of enrichment of raw materials on the size of the separation of particles by screening devices has an extremum, and the value of the size corresponding to the maximum of the indicator does not depend on the efficiency of screening. This makes it possible to use a screening mode with an optimal particle size separation, while ensuring high enrichment efficiency, reducing waste from the processing process, and improving the ecological situation in the region. A method for calculating the optimal size of the separation of the material to be classified has been developed. On its basis, an algorithm for calculating the indicators of the concentration efficiency was created, which allows obtaining expanded information on the nature of changes in certain parameters with a variation in the size of the separation of particles and screening efficiency. The use of a roller-finger screen as a combined device, which carries out both the separation of clay coatings from pieces of limestone, and the separation of particles by size (including conditions of high humidity of the feedstock), improves the screening efficiency. Based on the study of the dynamics of the particle of the material, the determination of the forces acting on the particle, the obtained analytical dependence determines the condition for excluding the mode of its infringement. It is proved that such a regime does not depend on the levels of forces acting on the particle, but is determined exclusively by the values of the angles characterizing the position of the points of contact of the particle with parts of adjacent rolls. To study the enrichment and classification processes of the feedstock, linear regression multifactor models were created, where the values of the limestone content in the feedstock and the moisture content of the material were used as factors, and the values of the indicators of the efficiency of enrichment and screening of limestone were used as the response functions. The models allow the comparing of the efficiency of screening and beneficiation processes in classification options with and without a roller-finger screen. The presence of a roller-finger screen is manifested in its stabilizing effect on the classification process, which is accompanied by an increase in the beneficiation efficiency by 10-20%. Along with the tasks of increasing the efficiency of enrichment of raw materials from carbonate deposits, the indicators of the energy efficiency of the technological 196 process are considered. A methodology for assessing the energy intensity of the existing and proposed raw material enrichment technology has been developed. The structure of the regression model for standardizing the indicator of specific electricity consumption is proposed and a list of measures that are advisable to use in order to improve energy efficiency is determined.