Geometric Effect of Taylor Vortex on Agglomeration of Ni/Mn/Co hydroxide in Continuous Reaction Crystallization
Taylor-vortex flow agglomeration reaction crystallization continuous crystallizer flow regime;
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Ni-rich hydroxide (Ni0.90Co0.05Mn0.05)OH2 is an active precursor of the cathode material for battery. One of the most critical factors determining the electrical capacity of the cathode is the tap density which depends on a uniform size distribution and a spherical shape. Thus, in the present study three different geometries and rotation speed were varied in order to investigate the influence of the Taylor vortex flow regime on agglomeration of Ni-rich hydroxide to produce an agglomerate particle with a narrow size distribution and spherical shape. The experimental results revealed that the Taylor vortex flow regime was shifted from weakly turbulent vortex to turbulent flow as the geometry (η) and the rotation speed were varied, providing different mixing intensities which influence in the agglomerate particle size, morphology and coefficient of variation (CV). As η decrease and the rotation speed increase the agglomerate particles became spherical in shape and were narrowly distributed. According to those results, the highest tap density is 2.15 g/ml and was achieved at the geometry η=0.89 and 1500 rpm of rotation speed, thereby the crystal agglomeration was more effectively enhanced with this condition which is suitable for a high packing density required for a cathode material. The empirical correlations between the CV and the tap density with the average shear rate indicated that they are dependent of the geometry of the crystallizer, and it applies for the three studied geometries. The influence of the coefficient of variation on the tap density in the agglomerate particles in the CT crystallizer with different geometries exhibit a linear correlation, thus as the CV value decrease it is possible to get a higher tap density for the agglomerate particle of (Ni0.90Co0.05Mn0.05)OH2.