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首页> 外文期刊>Advanced Powder Technology: The internation Journal of the Society of Powder Technology, Japan >Fluidized Bed Dryers - Recent Advances
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Fluidized Bed Dryers - Recent Advances

机译：流化床干燥机-最新进展

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Although industrial fluidized bed dryers have been used successfully for the drying of wet solid particles for many years,the development of industrial fluidized bed dryers for any particular application is fraught with difficulties such as scaling-up,poor fluidization and non-uniform product quality.Scaling-up is the major problem and there are very few good,reliable theoretical models that can replace the expensive laboratory work and pilot-plant trials.This problem is mainly due to the different behavior of bubbles and mixing regimes in fluidized bed dryers of different size.Simple transformation of laboratory batch drying data to continuous back-mixed dryers using the residence time distribution of the solids is insufficient to account for the complex flow and heat and mass transfer phenomena occurring in the bed.Although time scaling using temperature driving forces and solids mass flux for the same change in moisture content in the batch and continuous dryers has been successful in predicting moisture content profiles in the continuous dryer at the constant rate period,it does not take into account solid mixing.Two-phase Davidson-Harrison models have been used in modeling of the continuous back-mixed dryer with various degrees of success.On the other hand,the three-phase Kunii-Levenspiel model is seldom used in modeling fluidized bed dryers because it is too complex to handle.A combination of multi-phase models and residence time distribution could improve predicting power for back-mixed dryers because this combination takes into account both the bubbles and solid mixing phenomena.Incremental models were widely used to model continuous plug flow fluidized bed dryers,but the cross-flow of drying medium has not been sufficiently modeled except by the author.In some incremental models,axial dispersion is modeled using the Peclet number,Pe.A combination of an incremental model with an axial dispersion and cross-flow model of drying medium would improve predicting power.Poor fluidization of Geldart group C particles could be improved by the assistance of external means such as vibration,agitation,rotation and centrifugation.Both vibrated and agitated fluidized bed dryers have been successfully used in industry,but rotating or centrifugal fluidized bed dryers are still not available for industrial use.
机译：尽管工业流化床干燥器已成功用于干燥湿固体颗粒多年，但针对任何特定应用的工业流化床干燥器的开发仍面临着诸如规模扩大，流化差和产品质量不均等难题。放大是主要问题，很少有好的，可靠的理论模型可以代替昂贵的实验室工作和中试研究。该问题主要是由于不同流化床干燥器中气泡的行为不同以及混合方式不同使用固体的停留时间分布将实验室批次干燥数据简单转换为连续反向混合干燥器不足以解决床中发生的复杂流动和传热传质现象。批次干燥机和连续干燥机中水分含量相同变化的固体质量通量已成功在预测恒定速率的连续式干燥机中的水分含量分布时，它没有考虑固体混合。两相Davidson-Harrison模型已用于连续反混式干燥机的建模，取得了不同程度的成功。另一方面，三相Kunii-Levenspiel模型很少用于流化床干燥器的建模，因为它处理起来太复杂。多相模型和停留时间分布的组合可以提高对回混干燥器的预测能力，因为增量模型被广泛地用于连续塞流流化床干燥器的建模，但是除作者以外，没有对干燥介质的交叉流进行充分建模。在某些增量模型中，轴向使用Peclet数Pe对分散进行建模。将增量模型与轴向分散和干燥介质的错流模型结合起来可以改善预测借助振动，搅拌，旋转和离心等外部手段可以改善Geldart C组颗粒的流化不良。振动和搅拌流化床干燥机均已在工业中成功使用，但旋转或离心流化床干燥机已被广泛使用。仍无法用于工业用途。

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