Particle classification of fine size region by using hydrocyclone

Abstract

The electric hydrocyclone had never been investigated. The reduction of the particle cut size was important in many industrial processes. In this research, a novel electric hydrocyclone was developed and tested. Aqueous suspensions of silica with a median diameter of 0.754 micrometer and 0.2% volumetric concentration were tested using a 20-mm-diameter hydrocyclone. The ratios of the experimental underflow to the throughput were: 0, 0.1, 0.2 and 0.3. The tested volumetric flow rates were 0.083*10[superscript -3] and 0.117*10[superscript -3] and 0.167*10[superscript -3] m[superscript 3]/s (5, 7 and 10 L/min). The four investigated pH of the suspension were: 6.0, 8.0, 9.0 and 10.0. The conical part of the electric hydrocyclone was connected to a cylindrical dust box having 41.8 mm diameter. This dust box had a central metal rod cone and a cylindrical metal wall between which the desired 50-volt DC electric potential or no potential was applied. The investigated lengths of the dust box were 53 and 106 mm. The investigated central rod diameters were 8, 12, 16 and 20 mm. The three different cases investigated were: a) no applied electric potential, b) positive potential applied at the central rod side and negative potential at the side wall, and c) the reverse of case b). In both the presence and absence of the underflow, the hydrocyclone with a long dust box was found to give smaller the 50% particle cut size, d[subscript 50] than that with a short dust box. Both the presence and absence of the underflow expectedly decrease d[subscript 50] when electric potential was applied. Moreover, the presence of the underflow gave smaller d[subscript 50] than the absence of the underflow. It was found that case c) exhibited a stronger effect on the d[subscript 50] than case b). Application of the electric potential in case c) can reduce d[subscript 50] by up to 9.6% compared to the absence of electricity. As expected, the higher the underflow to throughput ratio, the smaller d[subscript 50] becomes. The zeta potential was increased when the suspension had higher pH. The electric potential exhibited a stronger effect when the suspension had higher pH. The higher the pH, the smaller d[subscript 50] becomes. The combined effect of electric potential and pH can reduce d[subscript 50] by up to 18.8% compared to the absence of electricity. Moreover, the electric potential exhibited a stronger effect when the central rod had a larger diameter. The effect of electric potential with the largest central rod diameter and highest pH can reduce d[subscript 50] by up to 22.7% compared to the absence of electricity. The best conditions to obtain the smallest d[subscript 50] were that the long dust box be used, the system was operated with a highest pH suspension, the largest central rod diameter and positive electric potential at the wall be employed in the presence of the underflow. Based on the experimental results, a semi-empirical correlation for d[subscript 5]had been obtained