Ladle Slag of Electric Steelmaking as Alkaline Agent on Controlling of Acid Mine Drainage Generation

摘要

Commercial coal production in the southern region of Brazil (comprising the Paraná, Santa Catarina, and Rio Grande do Sul states) has been occurring since the beginning of the twentieth century. Regarding the Santa Catarina coalfields, about 60% - 65% of the ROM coal is discharged at dump deposits as waste. These wastes can lead to the formation of acid mine drainage (AMD), a source of ground and surface water pollution. One of the technologies used for preventing AMD consists of the alkaline additive method. Thus, the aim of this work was to study, at laboratory scale, the DAM control by blending coal waste with a metallurgical slag. A coal-tailing sample was collected from a coal mine, and the slag was obtained from a semi-integrated steel plant. Static tests were carried out by the acid-base account method to determine the balance between the acid-producing and acid-consuming (neutralizing) mineral components of the samples. Kinetic tests were conducted in humidity cells, following the ASTM D 5744-96 method, for a period of 80 weeks. The results showed that the coal tailing generates AMD. However, environmental problems can be minimized by mixing the coal waste with the metallurgical slag in 1:1 or 1:1.5 proportions. The kinetic experiments proved that, in this condition, the lixiviation presents a higher pH and a lower concentration of acidity, metals, and sulfate. Finally, it is possible to conclude that the blending slag in coal tailing deposits can be a viable alternative for DAM control in coal mining.