Investigation of settling behaviour of gördes and karaçam lateritic nickel ores at CCD process after hpal

In this study, the sedimentation performance of Manisa-Gördes and Eskişehir-Karaçam lateritic nickel ores were investigated in counter current decantation (CCD) thickeners at the High Pressure Acid Leaching (HPAL) process. In the scope of the study, all test samples were taken from the plant stream at different times and a series of sedimentation tests were performed using anionic, cationic and nonionic flocculants of various ionic and molecular weights. The sedimentation performance was evaluated according to parameters such as sedimentation time, clarity and compression. The flocculants used were freshly prepared before each test and applied in two stages as a stock solution at a concentration of 0,1%. Flocculants were studied on a wide scale in terms of molecular weight and ionicity, but flocculants that did not show any flocculation effect were not included in the evaluation. In order to determine the optimum conditions for the tests, a pre-test was applied and the sludge solid content 7% and the flocculant dosage 850 g/t was indicated. According to the results of the test, it was observed that especially high molecular weight nonionic flocculants gave better results than other flocculants. It has been found that flocculation is adversely affected with the increase of anionicity and results are obtained only with very low anionic flocculants. The settling rate with cationic flocculants is very fast, but especially for Gördes ore, the amount of compression is not favorable. However, it is envisaged that the amount of consumption can be reduced if cationic flocculant is used. When a comparison was made between the two ores, similar results were obtained in general terms. The thickener underflow density was acceptable for all flocculant performances with Karaçam ore. On the other hand, it was concluded that the variable ore structures and unstable process parameters have an effect on the change of flocculant adsorption mechanisms and consequently on the settling behavior.