| Submerged Membrane Bioreactor (SMBR) is a kind of new reactor that is the combination of biological degradation and membrane separation, and is improved on inner loop air-lift bioreactor.By theory analysis, relationship of gas holdup, liquid circulation velocity and oxygen transfer coefficient along with reactor structure, operation parameters and mixture characteristic parameters , which is of importance to fluid dynamics of SMBR, are gained. With the requirement of application in project, the constucture of reactor are optimized.By experiment study of sparger optimization of SMBR, the performance about different types of perforated pipe sparger are obtained. (1) The regime experiment shows that the fluidizing quality is almost equivalent to CSTR (Continuous Stirred Tank Reactor). Compared fluidization to different pore sizes of sparger at the same conditions, the smaller pore size sparger is more divergence to the CSTR;(2) The oxygenizing experiment indicates that the oxygenation performance of three pore size spargers are more or less the same , and all are the similar to the widespread mesopore sparger;(3) The Hydrodynamics experiment , using tap water is investigated, and conclusion is that under the three types of perforated pipe sparger conditions, air lift flow velocities increased and then reached a stable point with the intensification of aeration intensity in riser. Under the condition of low aeration intensity, the larger the pore size, the higher the air lift flow velocity, while under the high aeration intensity condition, the air lift flow velocities of three types of sparger tend to the same peak value. The larger pore size of sparger is superior to the small one from the point of view of controlling the membrane fouling. It does mean that there is a economical aeration intensity in this reactor, here is about 100m3/m~2/h, the corresponding air lift velocity is about 0.43m/s;(4) The high flux membrane filtration results that the large size sparger is more benefits to preventing sedimentation and deposition of colloidal suspension on the membrane surface.Critical flux region for module of pilot-scale SMBR was measured with "flux step-wise method", in the condition of different aeration intensities and different sludge concentrations. Furthermore characteristics of critical flux were studied. The conclusions is that--(1) for a given configuration of SMBR and in a condition of sludge concentration specifically, aeration intensity is the most of important parameter impacting the critical flux. When aeration intensity is less than economical aeration intensity, critical flux increased with the aeration intensity intensifying, whereas the critical flux to a peak value;(2) under the condition of aeration intensity , the critical flux decreased with the concentration of sludge increased, but in a specific range of sludge concentration, critical flux is stabilizing;(3) under the condition of a specific sludge concentration, reactor configuration became the main parameters effecting the critical flux choosen.According to the continuity equation, the momentum equation, and the energy equation for mixture, software Fluent is used to simulate flow regime in SMBR. The static pressure distribution , liquid circulation velocity and gas holdup in the whole reactor -downcomer and riser, and local zones are gotten by simulation. Influence of reactor structure to its performance is analyzed, the span of some parameters are knew. It is verification that the CFD simulation Model could be used to describe the relationship of air lift flow velocities and aeration intensity accurately in a SMBR within the range of the airflow rates applied... |
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