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回転円筒型液液抽出装置における流動状態におよぼす操作条件の影響

Rotor speed and supply flow rate effects on flow behavior in an annular centrifugal extractor

三角 隆太*; 國井 佳奈子*; 轟 慧*; 仁志 和彦*; 上ノ山 周*; 佐野 雄一; 坂本 淳志; 竹内 正行

Misumi, Ryuta*; Kunii, Kanako*; Todoroki, Kei*; Nishi, Kazuhiko*; Kaminoyama, Meguru*; Sano, Yuichi; Sakamoto, Atsushi; Takeuchi, Masayuki

原子力分野の使用済核燃料再処理プロセスでは回転円筒型液液抽出装置の利用が注目されているが、抽出効率に大きく関連する装置内の流動状態に対する操作条件の影響については十分な検討が行われていない。本研究では、主要な操作因子であるロータ回転数や溶液の供給流量が異なる条件を対象に、混合部の流動状態の観察、ならびにParticle Image Velocimetryによる流速分布測定を行った。ロータ回転数や溶液の供給流量が変化した場合に、装置内の混合部の流動状態が、(a)混合部底面からロータ下部までが液体で満たされロータの回転の影響が流速分布に強く影響する状態(流動状態A)、(b)混合部下部における液の存在領域が、槽底の固定羽根近傍とロータ下部近傍に鉛直方向に大きく2つに分断される状態(流動状態B)、(c)これら2つの状態の過渡的な状態(遷移状態)の3種類の状態に分類されることを明らかにした。8枚の固定羽根が槽底に放射状に取り付けられた混合部では、2枚の固定羽根と槽壁に囲まれた各領域内で、槽壁近傍ではロータの回転方向に沿った流れが形成され、下流側の固定羽根に沿って曲げられ槽底中心部に流れ込むフローパターンであることがわかった。流動状態Aでは、混合部内の水平断面内の流速分布はロータ回転数に対しておおよそ比例するが、流動状態Bでは流動状態Aより流速が遅く、ロータ回転数には比例しないことがわかった。

Annular centrifugal extractors have been used in spent nuclear fuel reprocessing, but the relation between the extraction rate and flow pattern in the vessel remains unclear. This study quantifies characteristics of the flow pattern to clarify this relation. An extractor produces a mixing zone around the vessel bottom and a separation zone in the rotor. The horizontal velocity of the liquid in the mixing zone was measured using particle image velocimetry at various rotor speeds and supply flow rates. Flow behaviors in the mixing zone are of three types, changing with operational conditions: Type A, Type B, and a transition regime. At lower rotor speeds and high supply flow rates, the mixing zone is fully filled with liquid from the vessel bottom up to the lower edge of the rotor: the Type A flow state. At high rotor speeds and low supply flow rates, the zone with existing liquid is vertically divisible into two regions: near the vanes and around the bottom of the rotor, which is the Type B flow state. A transition regime is also observed between Type A and Type B state. In each region surrounding the two vanes on the vessel bottom and the vessel wall, the liquid flowed in the direction of rotor rotation along the vessel wall. Liquid flow altered by the vane flowed toward the center of vessel bottom. The liquid then entered the separation zone through the orifice at the rotor bottom. For the Type A state, the horizontal velocity distribution was roughly proportional to the rotor speed. For the Type B state, the horizontal velocities around the vessel bottom were lower than those of Type A and were not proportional to the rotor speed. Presumably, the liquid fed into the vessel went directly to the rotor instead of passing between the two vanes attached to the vessel bottom.

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パーセンタイル:100

分野:Engineering, Chemical

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