Dustan A C, Cohen B, Petrie J G
Department of Chemical Engineering, University of Cape Town, Rondebosch 7700, South Africa.
Adv Colloid Interface Sci. 2005 May 30;113(2-3):85-97. doi: 10.1016/j.cis.2005.01.003. Epub 2005 Apr 2.
An understanding of the mechanisms which control solids formation can provide information on the characteristics of the solids which are formed. The nature of the solids formed in turn impacts on dewatering behaviour. The 'upstream' solids formation determines a set of suspension characteristics: solids concentration, particle size distribution, solution ionic strength and electrostatic surface potential. These characteristics together define the suspension's rheological properties. However, the complicated interdependence of these has precluded the prediction of suspension rheology from such a fundamental description of suspension characteristics. Recent shear yield stress models, applied in this study to compressive yield, significantly reduce the empiricism required for the description of compressive rheology. Suspension compressibility and permeability uniquely define the dewatering behaviour, described in terms of settling, filtration and mechanical expression. These modes of dewatering may be described in terms of the same fundamental suspension mechanics model. In this way, it is possible to link dynamically the processes of solids formation and dewatering of the resultant suspension. This, ultimately, opens the door to improved operability of these processes. In part I of this paper we introduced an integrated system model for solids formation and dewatering. This model was demonstrated for the upstream processes using experimental data. In this current paper models of colloidal interactions and dewatering are presented and compared to experimental results from batch filtration tests. A novel approach to predicting suspension compressibility and permeability using a single test configuration is presented and tested.
了解控制固体形成的机制可以提供有关所形成固体特性的信息。所形成固体的性质反过来又会影响脱水行为。“上游”固体形成决定了一系列悬浮特性：固体浓度、粒度分布、溶液离子强度和静电表面电位。这些特性共同定义了悬浮液的流变特性。然而，这些特性之间复杂的相互依存关系使得无法从对悬浮特性的这种基本描述中预测悬浮液的流变学。本研究中应用于压缩屈服的近期剪切屈服应力模型，显著减少了描述压缩流变学所需的经验性。悬浮液的压缩性和渗透性唯一地定义了脱水行为，可通过沉降、过滤和机械压榨来描述。这些脱水方式可以用相同的基本悬浮力学模型来描述。通过这种方式，可以动态地将固体形成过程与所得悬浮液的脱水过程联系起来。这最终为改进这些过程的可操作性打开了大门。在本文的第一部分，我们介绍了一个用于固体形成和脱水的综合系统模型。该模型通过实验数据在上游过程中得到了验证。在本文中，我们给出了胶体相互作用和脱水的模型，并与间歇过滤试验的实验结果进行了比较。提出并测试了一种使用单一测试配置预测悬浮液压缩性和渗透性的新方法。
