Correlation Study On Collection Zone Pressure Fluctuations And Hydrodynamics In A Flotation Column

Cyclonic microbubble flotation column creatively combines the centrifugal force field with flotation and develops a multi-stage sorting mechanism of“collection in roughing zone—selection in swirl zone—selection in foam zone”in a unit.Fluid dynamics?hydrodynamics?of flotation column plays an important role in the flotation performance of coal particles.Until now,the main methods for studying the hydrodynamic characteristics of flotation columns include photographic imaging technology,tomography technique,particle tracing technology,and probe technology.These technologies are expensive and difficult to apply to the complex production environment of industrial flotation columns.Pressure measurements are widely used in the characterization of fluid dynamics in laboratory,semi-industrial and industrial gas-liquid-solid fluidized beds and bubble columns.They have the advantages of easy operation,inexpensive price,and suitable for harsh industrial conditions.Therefore,the pressure fluctuations technique is used to evaluate the hydrodynamics of the flotation column,which provides the technical support for the stable and efficient separation of the particles,and is expected to provide intellectual support for the monitoring of the separation effect monitoring of the large-scale industry flotation column.In order to study correlation study on collection zone pressure fluctuations and hydrodynamics in a flotation column,the pressure measurement technology was introduced into the study of the fluid dynamics characteristics of the flotation column collection zone.The bubble size,bubble rise velocity,gas holdup,and pressure fluctuations of the gas-liquid flow in the collection zone of the flotation column were measured by the bubble parameter measuring instrument and pressure-difference method.Time-series analysis in time domain,frequency domain,and in state space were carried out to characterize the hydridynamics of the gas-liquid flow.Quantitative analysis between the characteristic parameters of pressure fluctuation and the characteristic paramaters of hydrodynamics?bubble size,bubble velocity,gas holdup and bubble Reynolds number?were carried out in a gas-liquid flotation column.Furhermore,hydrodynamics of a gas-liquid-solid flotation column was studied quantitatively with time-series analysis of pressure fluctuations.The time-series anlysis of the pressure fluctuation are used to preduct the recovery of coal particles in a flotation column.The main research results are follows:Firstly,the correlation between the characteristics of pressure fluctuations in frequency domain and the bubble motion behavior was studied.The quantitative relationship between the incoherent standard deviation of pressure fluctuations and the large bubble diameter of gas-liquid two-phase flow was established((?_IOP=22.67?7?d_???,avg?8?^1.65,Adj.R²=0.9511)).Bubble coalescence results in non-uniform distribution of the bubble size,the increase of the number of large bubbles,the development of liquid circulation?eddy?.Those phenomena are in good aggrement with the random motion of the bubble movement,and the increase in the power spectral density in the 3-5 Hz frequency region.Secondly,the correlation between the chaotic characteristic parameter?Kolmogorov entropy?of pressure fluctuations and bubble Reynolds number in the collection zone was investigated?Kolmogorov?=0.13ln?7?Re_b?8?-0.67,Adj.R²>0.99?.When the fluid regime in the collection zone changes from bubbly flow?homogeneous?to churn turbulent?heterogeneous?,large bubbles occurs in the center of the column,and bubbles coalesce more clearly.The rising velocity of large bubbles is obviously higher than that of small bubbles,and thus the liquid recirculation?eddy?presents around them.Those leads to the increase in the chaotic degree and the turbulent intensity of the gas-liquid flow.Thirdly,there is a strong correlation between the standard deviation of pressure fluctuations and bubble size,bubble velocity and bubble Reynolds number,while the correlation between gas pressure and gas holdup is relatively poor.The linear fitting goodness between the standard deviation of pressure fluctuations and the characteristic parameters of hydrodynamics is poor?Adj.R²<0.8?,which is mainly due to that the statistical analysis method ignores the frequency characteristics of pressure fluctuations.the correlation between the standard deviation of pressure fluctuations and the hydrodynamic parameters in the collection zone was evaluated.The standard deviation of pressure fluctuations is related to the behavior of bubble motion.With the increase of measuring position height,the degree of bubble motion becomes more irregular,and the degree of irregularity of bubble size distribution increases.Fourthly,it is observed that the results of spectrum and chaotic analysis of gas-liquid-solid flow pressure fluctuations are in good agreement with the qualitative analysis results of the hydrodynamic conditions in the collection zone.The chaotic analysis of the pressure fluctuations that the existence of solid particles also reduces the degree of chaos and the power spectral density in the 3-5 Hz frequency region.The presence of solids can inhibit the bubble coalescence and reduce the flow turbulence of the collection zone.Finally,it is found that there is a good correlation between pressure fluctuations and particle recovery under the relatively low solid concentrations.The chaotic characteristic parameters?Kolmogorov entropy?of the pressure fluctuations in the collection zone have a good correlation with the flotation yield of coal particles under the relatively low solid concentrations.Under higher solid concentrations,the correlation between chaotic characteristic parameters and particle recovery is poor due to the limitation of bubble loading capacity.