Flow through the Two-stage Hydraulic Cyclone

Abstract

As the authors discussed in the previous paper2), the sharpness of classification of hydraulic cyclones may be markedly improved by combining them in series as shown in Fig.1. In such a system, as we call the two-stage cyclone system, the overflow-side back pressure Po of the first cyclone I is not always the same as the underfiow-side back pressure Pu, because pressure drops through the two second cyclones (ΔpIIo and ΔpIIu) may differ from each other. Consequently, flow rate and flow ratio through cyclone I will be functions of the overflow-side pressure drop Δpo (=Feed pressure Pf-Po), the underfiow-side pressure drop Δpu (=Pf-Pu) and the dimension of the cyclone.To see the effect of back pressures on the flow rate and the flow ratio of cyclone I, an experimental apparatus as shown in Fig.2 was constructed. The underfiow nozzle of the cyclone I was enclosed in a back pressure chamber A. Overflow and underfiow rates were adjusted by valves E and D and the back pressures were measured with manometers C and F. Thus full range of flow ratio from zero to 100% could be surveyed with this apparatus.Typical examples of the results are shown in Figs.3 and 4, where the observed points are plotted on the Δpo/γ vs ΔPu/γ chart. Numbers above the points show the flow rate Qf and numbers in bracket under the points represent the flow ratio Rf. It may be seen from these charts that the points of equal flow ratios lie on the straight lines (equi-flow-ratio lines) which cross the origin. All the observed points fall between those two limiting lines which represent zero and 100% flow ratio. Inclinations of equi-flow-ratio lines are correlated to De/Du and Rf as shown in Fig.7 and equation (6). Do and Du seem to have equivalent effects on the flow rate and the flow ratio. Similarly the points of equal flow rate lie on the straight line which ties the same flow rate points on two limiting lines. The flow rate Qf is represented in equation (8) as a function of Δpo, Δpu and the dimension of the cyclone.Applying these results, dimension, pressure drop and Newton's classification efficiency are calculated for the purpose of designing two-stage, circulation type hydraulic cyclone system. Results of the calculation are shown in Fig.12, 14 and Table 3.