Characteristics And Mechanism Of A Multi-velocity Gradient Flocculation Fluidized Bed

Flocculation is one of the most significant processes for water treatments, whichdetermine the running conditions of the following processes, quality of effluent andoperation costs of water treatment eventually. Therefore flocculation process is anincreasing popular concern in water treatment discipline. Flocculation fluidized bed, anew type of flocculation plant, was developed by utilizing the characteristic that solidparticles could achieve a fluidized condition. Compared with those conventionalprocesses, the flocculation fluidized bed has many advantages, such as easy operation,small footprint, lower power consumption, high efficiency and so on. In this paper,previous work of other researchers was our basis and we did some further research toexplore the new reactor plant. Firstly, the device was filled with resin particles A andresin particles B, respectively. Then the variation of velocity gradient G value andflocculation time T value, which were the flocculation control indicator parameters,respectively, was researched. We explored the flocculation efficiency variation with Gand T value changes for treating kaolin suspension and optimize the two ranges. Theexperiment results showed that the flocculation efficiency increased firstly and thendecreased with the increase of G values. As a result, the optimal G value range ofapproximately was165-180s-1. On the whole, the longer the flocculation time was,the higher the efficiency was, but too long time would cause flocs broken.Flocculation efficiency would improve when the GT values increased. But when GTvalue was greater than10000, the efficiency did not significantly improve or evendecreased to some extent.On the basis, two or more kinds of particles were filled with in the device. Becausedifferent particles have different hydraulic fluidization characteristics, a multi-velocitygradient condition can be established. Then a contrast was made betweenmulti-velocity gradient and single-velocity gradient on efficiency. The results showedthat the flocculation efficiency was5%-10%higher in MGF than in SGF. And thedevice had a better ability to fight against external impact load. We had a initialattempt to treat disperse red solution, similarly, the efficiency was7%-20%higher in MGF than in SGF.At the same time, with the help of floc morphology techniques, morphologicalcharacteristics of flocs under different conditions were studied. A further study aboutreaction characteristics in multi-velocity gradient flocculation fluidized bed was made.The results showed that in MGF reaction process, the floc size increased with fractaldimension and density decreasing with the increase of bed height.In addition, we had preliminary attempts to use some model for studying the kineticcharacteristics in the device. In the flocculation reaction, the floc size was increasing,and the space among flocs was increasing, too. So the frequency and time of flocscollision reduced. And the data show that the collision efficiency in the device wasmore than60%.This thesis focused on flocculation efficiency and reaction characteristics of thedevice. And three kinds of solid particles were studied. Our research shows that thiskind of device has a good practical application and this thesis can provide somereference for designing similar reactor.