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Study on Simulation of Flow and the Influence on Fractal Growth of Flocs in Floccution Reactor

Author: RaoHongMei
Tutor: NanJun
School: Harbin Institute of Technology
Course: Municipal Engineering
Keywords: Flocculation reactor Similarity theory Beaker experiment Three-dimensional flow field Numerical Simulation
CLC: X703
Type: Master's thesis
Year: 2010
Downloads: 108
Quote: 1
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Abstract


Flocculation process to the water treatment process in the application of the most common and one of the most important aspects, which largely affect operating costs, the operating conditions of the follow-up process and the final effluent quality, and thus become the water industry an important scientific and technological research and development fields. In the flocculator the hydraulic conditions floc and water are inseparable. Floc by the water entrainment movement and water flow has a good companion, therefore floc seen as flowing medium, to study the flocculation process as fluid dynamics problem. Binding experiments and numerical simulation of the subject, to the PAC as flocculant, humic acid organic matter in the water and kaolin particles suspended in fluid mechanics for the removal of the object, the study of the geometric dimensions of the existing jar test flocculation effect similar theory to explore the beaker test promote the use of results in the production practice, and studied the impact of changing the structure of the reactor flocculation effect, and flocculation reactor three-dimensional flow field simulation to explore ways to enhance flocculation efficiency and optimize flocculation process provides a fast, reliable, and effective method. Beaker test is widely used in the production of water treatment research and guidance, but the validity of the the beaker test simulates actual flocculation process so far more controversial, domestic and foreign research little problem of the flocculation model test on this special test, it is necessary research. In this paper, on the basis of the beaker test different sizes of geometric similarity relations reactor Experimental Study on the flocculation effect, residual turbidity as evaluation of geometric similarity flocculator the flocculation effect exists between the different make reasonable interpretation of analysis. The test results indicate that the reactor scale enlarged flow structure changed, the G value of the same flocculation process does not similar. Floc particles are brought into contact collision force is a shearing force generated by the swirling motion and the inertial centrifugal force, wherein the the scroll shear force is the dominant driving force of the flocculation reaction. Due to the structure of the reactor directly affect the flocculation tanks vortex scale and quantity, so it is decided flocculation effect of one of the key factors play a decisive role in the floc growth. By changing the shape of the reactor, high aspect ratio (H / D) inside the reactor, the bezel width (B) and the stirring blade height (C) hydrodynamic conditions using fractal dimension and the average of the residual turbidity, floc particle size as the evaluation index, the different flow conditions on the flocculation effect to obtain a more rational geometry of the flocculation reactor in each case, the test results showed that: a circular reactor, high aspect ratio H = 1.00D baffle width B The flocculation effect = 0.20D and a stirring blade height when C = 0.33H best. Experiments concluded: reasonable to change the pool type, baffle spoiler adjustment the stirring paddle height flocculation reaction conditions, and design studies to optimize the flocculation of important guiding significance in the production practice, if effective control vortex body to eliminate large-scale vortex, increase the proportion of small-scale vortices, can significantly increase the number of particle collisions, effectively improve the flocculation effect. Applied Computational fluid dynamics software FLUENT simulation calculation of the three-dimensional flow field in the reactor under different hydraulic conditions in the above experiments, the calculation results to analyze, interpret test phenomenon, and then study the flow structure in different reactor structure flocculation effect. The simulation results and the test results are basically the same: a suitable shape of the reactor, high aspect ratio, the width of the reactor internal baffles and stirring blades height hydraulics can effectively improve the effect of the turbulent flow in the reactor to promote the flocculation reaction carried out.

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CLC: > Environmental science, safety science > Processing and comprehensive utilization of waste > General issues > Wastewater treatment and utilization
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