Methodology for optimizing the granulometry of grits and dregs for use as mineral additions

Abstract

In 2020, the kraft cellulosic pulp industry produced approximately 21 million tons of pulp in Brazil, keeping the country as the world's second largest pulp producer (IBÁ, 2021). Therefore, there is a great concern related to the environmental impacts caused by the increase in the volume of generation of these wastes and consequent incorrect disposal of these. Among the residues generated in the Kraft  process, the dregs and grits stand out, which due to their predominantly calcium carbonate constitution, have potential for use as the mineral addition in partial replacement to Portland cement, for this, it is necessary that they have particles with diameters less than 75 μm (ABNT NBR 16697:2018). The aim of this study proposes to develop a methodology for obtaining particles of grits and dregs with a diameter of less than 75 μm, through the Los Angeles abrasion mill and the sieving, for this, the proposed methodology covers the steps described below; i) the determination of initial humidity; (ii) drying of samples; iii) determination of the granulometric distribution by sieving; iv) grinding by means of Los Angeles abrasion and sieving equipment; v) laboratory tests (dynamic imaging analysis and particle size analysis by laser diffraction). It can be seen that the grinding method adopted in the present study allowed a reduction of 99.4% and 99.7% in the average diameter of dregs and grits particles, respectively, proving the effectiveness of the methodology employed and the times adopted to reduce particle size.