Abstract: Traditional decanter centrifuge is only used to separate heavy sludge rather than floating sludge. This research developed a two-phase numerical simulation on a decanter centrifuge in separating light solid floating sludge. The three dimension software Pro-E was used to build the 3D model. The computational fluid dynamics software Fluent was applied to analyze volume fraction distribution of the solid and liquid phase as well as the effects of operating conditions and fluid parameters on flow field and separation properties. The simulation was based on Euler multiple phase flow model and RNG k-ε turbulence model in a multiple coordinate reference system. The simulation results showed that the decanter centrifuge can be used to separate high density and middle-coarse particles;the fluid settling lamination was obvious and water was in the inner side while floating sludge outside of cistern;there was little effect of rotation speed discrepancy on separation properties. Rotation speed discrepancy in the range of 30-70r/min was optimal. With the increase of the feed concentration,particles'setting velocity and separation efficiency decreased. Low setting velocity for small particles resulted in less separation efficiency and coarse particles had higher separation capabilities because of quick setting velocity.

Key words: light floating sludge separation, decanter centrifuge, numerical simulation, separation properties

摘要： 传统的卧式螺旋卸料离心机只能分离沉渣,不能分离浮渣。本文对一种分离轻质固体浮渣的卧螺离心机进行两相数值模拟研究,使用Pro-E软件建立三维模型,应用计算流体力学软件Fluent,基于Euler多相流模型,采用RNG k-ε湍流模型及多重参考系(MRF)方法,模拟分析了这种卧螺离心机内的固液两相体积分数分布以及操作参数和物性参数对流场和分离性能的影响。模拟结果表明:此卧螺离心机适用于高浓度、中粗粒子的分离;流体沉降分层比较明显,水在液池的外层,浮渣在内层;转速差总体上对分离性能影响不大,但不能过低或是过高,保持在30~70r/min是比较好的选择;进料浓度增加,颗粒沉降速度降低,分离效率会下降;小颗粒沉降速度底且易"反混"而分离性能差,较大颗粒沉降速度高,分离性能明显高于小粒径颗粒。

关键词: 浮渣分离, 卧螺离心机, 数值模拟, 分离性能