On The Study Of Continuous Flocculation Process Using An OFR

The history and actuality of flocculation technology are reviewed in this paper. The reactors for flocculation, which are mostly used nowadays, have disadvantages and problems including configuration complexity, flow patterns changefully, space consuming, low flocculation rate and reaction effects instability. Furthermore, the control indicators for reaction effects, which are calculated from all kinds of reactive dynamics, are questioned in its application universality and reliability.Oscillatory Flow Reactor(OFR) is a new type of devices in Chemical Engineering Process, which has a good performance in heat and mass transport. The baffles in the reactor and oscillatory devices in the bottom make the reactor close to a plug flow reactor under certain conditions.In this paper, the effects of flocculation reactions, which were carried out in the OFM continuously under different oscillatory conditions, were studied by measuring the sedimentation curves and its particle size distributions. In said flocculation reactions, the suspension was prepared from diatomite of Shenxian after some treatment. Flocculants applied was FeCI₃ (1#) and mixture (2#) of HPAM and FeCI₃. The average aggregates size was 100 times bigger than primitive particles' using 1# flocculants and 1000 times bigger using 2# flocculants. Flocculation effects were obviously affected by oscillatory conditions: average size of aggregates increase with oscillatory frequency f and swing x. The best oscillatory condition for flocculation was reached at St=0.796, Re_o=3102 when using 1# flocculants and St=0.796, Re_o=5170 using 2# flocculants. The average size of aggregates doesn'tincrease with Re_o=(2Ï€ fx_oDρ)/μ in all conditions, which indicates that it is notreasonable to have Re_o as the control indicators for flocculation in OFR.Taking the fluid flows we observed through a camera under different Strouhal and Reynolds numbers into account, we found that the effects offlocculation increase with the area of vortex of certain size. The oscillatory extend is the key to the emergence of vortex while oscillatory frequency dominates the range and distribution of the vortexes. The fluid flow statusleading to flocculation can be determined by a parameter tj G, and theResidence time distribution can be described by Tanks-ln-Series with stage-between mixed flow.Besides, the fragmentation of floccules was observed in flocculation reaction under 1 # flocculants through size distribution analysis, which indicate that it is necessary to use decreasing-flocculation techniques in OFR when using non-organic flocculants. The decreasing-flocculation techniques may be introduced by changing the baffles' occupation rate on the upper part of thereactor.