Research on the influence of basic additives on the compressive strength of pellets

Besides the humidity, the granulometric composition and the specific surface of the pelleted material, the compressive strength of the pellets is also influenced by some additions with binding proprieties (bentonite, lime, limestone, dolomite, etc.). During the hardening process, these additions form a resistant slag that contributes to the binding of the granules of ferrous raw materials and, finally, to the increasing of the compressive strength of the pellets. The paper presents the results of the laboratory experiments on the production of pellets by using secondary materials (steel plant dust, sludge from sintering and blast furnace plants, red mud, etc.) as raw materials, and lime/dolomite as a binder along with the bentonite. To determine the influence of the addition of lime and dolomite on the compressive strength of pellets, we performed a series of experiments in the laboratory phase, consisting of the production of pellets based on various recipes, by adding bentonite & lime or bentonite & dolomite. During the research, we aimed to establish correlations between the compressive strength of pellets and the additions of water, bentonite, lime or dolomite. The data obtained in the experiments were processed in Excel and MATLAB programs, resulting simple or multiple correlation equations. Based on these equations, we could establish the optimum addition of materials with basic character