Badania i aplikacje technologiczne osadników lamelowych

Osadniki lamelowe stosowane są w dziedzinach, w których tradycyjnie stosowano sedymentacyjną metodę oczyszczania wód powodując podwyższenie skuteczności separacji zwłaszcza w zakresie cząstek drobnych. Dzięki temu, rozwiązanie to może zastępować hydrocyklony i filtry będące rozwiązaniami o znacznej energochłonności. Projektowanie osadników lamelowych jest jednak utrudnione ze względu na brak uniwersalnych, wystarczająco dokładnych metod obliczeniowych. Ten stan rzeczy skłonił do podjęcia badań i teoretycznej analizy procesu sedymentacji w osadnikach z wypełnieniem płytowym i profilowym o przepływie przeciwprądowym, współprądowym oraz krzyżowym. W efekcie opracowano jednolite ujęcie opisu procesowego w przypadku przepływu przeciwprądowego, współprądowego i krzyżowego w osadnikach z wypełnieniem, spełniających wymogi przemysłowe w zakresie parametrów technologicznych, procesowych i konstrukcyjnych, co daje podstawy racjonalnego doboru układu przepływowego.

The paper presents the study of the process of particles separation from the polydisperse suspensions, carried out by means of different laboratory stands comprising of lamella and multichannel settlers with counter-current, co-current and cross-current flow regimes. Considering the velocity distribution and dimensional analysis of the phenomena, a validation of variant models of the process has been carried out based on the obtained results. Correlation of the experiment results, concerning different industrial suspensions, carried out according to the theoretical equations, gives considerably bad outcomes, much worse than these produced by the empirical equation (2). Furthermore, these theoretical models disable functional analysis of the parameters, having significant influence on the process, proved by the experiments. Design purposes are worth recommendation for the correlation equations, incorporating equivalent diameter of the particles or in particular, the criterion equations using fractional diameter for calculation of sedimentation systems with particle fractions grading. The analysis of the obtained exponents, points out a different effect of some dimensionless numbers observed by different hydraulic regimes, which favours the use of model based on criterion equation, validated by experiments. It is a consequence of good representativity of particle size distribution through the dz50 value as well as particularly through the application of fractional efficiency calculation method. The analysis of exponents, accompanying geometrical simplexes, favours the use of: counter-current systems; for separation of suspensions of high inlet concentrations of particles - producing sediment of significant thickness, due to the removal of clarified liquid carried on in the upper part, co-current systems; in case of suspensions of relatively low inlet concentration and particles of significant density, which enhances stable sliding down of sediment and limits disturbances related to reemission of deposit. Cross-current systems; for classification of suspensions of diversified grain fractions materials, with applying the short plates. ? hybrid systems are composed of inlet and outlet short multichannel packing but in the middle, decisive part of plate packing. such an arrangement favours the compensation of inlet velocity distribution, stabilises the sludge collection and simultaneously it supports all system in the upper part of the settler. That construction solution is especially recommended for large-size settlers alleviate the influence of inlet-outlet effects as well. Developed model of process efficiency and empirical criterion equations, validated on the basis of around 1000 experiments, prove certain universal features and represent sedimentation process run by three regimes, with a high accuracy. These equations, as distinct from theoretical models, enable accounting for specific characteristic parameters like: polydisperse nature of the system, including bimodal distribution, the influence of geometrical invariants, and enhance the selection of flow regime in relation to the character of the suspension. The elaborated equations, concerning the fractional efficiency, enable also the design and optimisation of the settler geometry, both one - and two-stage, as well as the particle classifiers. Furthermore, the received results enabled: formulation of the uniform process description; formulation of rational criteria for the selection of appropriate settler depending on characteristic parameters of the suspension; and finally - the industrial application of the settlers.