概要:
前報1)において報告した旋回機構付きプロペラ式水中撹拌機(NKKスウィングミキサー)は,大規模下水処理場嫌気槽・無酸素槽用として開発され,低消費電力,軽量,メインテナンス性の良さや低ランニングコストを特徴とした画期的な新型撹拌機である。今回この旋回機構付きプロペラ式水中撹拌機が作動した場合の矩形槽内の流動状況を数値解析でシミュレーションする方法を新たに開発した。さらに活性汚泥に相当する固形物粒子を槽内に入れた場合に本撹拌機の槽底部への汚泥沈降防止効果についてもシミュレーション計算で求め,実設備における実験結果と比較した。この結果,槽内の流動状況および固形物の沈降状況についてもシミュレーション計算は実験と良い相関を示すことがわかった。
Abstract:
A propeller type underwater mixer with the oscillating mechanism is newly developed for the efficient mixing of large size wastewater treatment plants, which has already reported and named NKK Swing Mixer. It has the characteristics of low energy consumption, light weighted, easy maintenance and low running costs. This report deals with the numerical simulation method to obtain the unsteady flow field of the rectangular reaction tank using FLUENT-5 CFD code and user defined functions. Moreover the simulation of prevention from the sedimentation of sludge in the anaerobic reaction tanks by a NKK Swing Mixer are tested using algebraic slip mixing model using solid particles which has the similar diameter and specific gravity to the activated sludge in wastewater treatment tank. Simulated results containing the velocity distributions and activated sludge concentration distribution in several points in the tank were compared with the experimental results obtained at the actual working wastewater treatment plant. According to these results, the newly developed CFD simulation method showed close correlation with the experimental results.
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