Avaliação de reagentes alternativos para substituição da cal em sistema de bombeamento de longa distância de polpa de minério de ferro

Abstract

Two great concerns related to long-distance slurry pumping systems are plug formation, i.e. blockage, and sediment compaction upon shutdown. These problems are avoided in the Samarco Pipeline by adding lime. However, the presence of calcium ions generatesscaling in the storage tanks of the concentrate pumping system and in the process water pumping system in the pelletizing unit. Moreover, the filter media is degraded in the subsequent process. Some alternative reagents were tested with the objective of evaluating the possibility of lime substitution as a transport reagent. Two organic coagulants PolyDADMAC and Epi/DMA and two flocculants tapioca starch andCMC were evaluated at dosages of 5g/t, 100g/t e 300g/t by performing rheology, settling, penetration and angle of repose tests. It was verified that a dosage of 300g/t of the organic coagulants affect the slurry rheological behavior and settling velocity, besides the water clarification after settling, in like-manner as lime, so that they can replace it at this condition. Lower dosages do not result in coagulation or do notmaintain the slurry coagulated with agitation, therefore they were considered insufficient. The changes generated by the flocculants in the slurry characteristics are not satisfactory since they do not minimize the high probability of plug formation. It was concluded that the aggregation state of the ultrafine and colloidal particles of the iron ore slurry transported by the Samarco Pipeline must be changed by the coagulationmechanism in order to operate the system efficiently and safely.