Investigation of the settling behavior of lateritic nickel ores in the CCD process after HPAL

Abstract

In this study, the settling performance of lateritic nickel ores in the Counter Current Decantation (CCD) thickeners following the High-Pressure Acid Leaching (HPAL) process was investigated in detail. The samples used within the scope of the study were obtained from the overflow of the 2nd CCD thickener under the condition that Manisa-Gördes and Eskişehir-Karaçam lateritic nickel ores were fed to the plant at different times. A series of settling tests were performed for both ores using anionic, cationic, and nonionic flocculants of various ionicity and molecular weight. Sedimentation performance was evaluated based on parameters such as settling time, clarity, and compression. To determine the optimum conditions for the tests, a preliminary test was performed, and the pulp solids content was determined as 7% and the flocculant dosage as 850 g/t. According to the test results, nonionic and very low anionic flocculants gave better results. It was found that flocculation was negatively affected with increasing anionicity, and results could be obtained only with very low anionicity flocculants. It was determined that the settling rate was very fast with cationic flocculants, but the amount of compression was not favorable, especially for Gördes ore. However, it is envisaged that the amount of consumption can be reduced if cationic flocculants are used especially for Karaçam ore. When a comparison was made between the ores, similar results were obtained in general and only for Karaçam ore, tikiner underflow density gave a successful result for all flocculant performances. On the other hand, it was concluded that variable ore structures and unstable process parameters influence the flocculant adsorption mechanisms and thus on the settling behavior.