Chu C P, Ju S P, Lee D J, Mohanty K K
Chemical Engineering Department, National Taiwan University, Taipei, Taiwan.
J Colloid Interface Sci. 2002 Jan 1;245(1):178-86. doi: 10.1006/jcis.2001.7938.
We investigated the batch settling behavior of the kaolin slurry and the UK ball clay slurry at various initial solids fractions (phi(0)s) using a computerized axial tomography scanner (CATSCAN). The spatio-temporal evolutions of solids fractions in the consolidating sediments were continuously monitored. Since the interface between the sediment and the supernatant of the investigated slurries was blurred, an averaging procedure was employed to estimate their null-stress solids fractions (phi(g)s). Besides the rather slow settling for the high-phi(0) slurries, the basic settling characteristics resemble each other regardless of whether phi(0)>phi(g) or vice versa. The above-mentioned experimental data reveal that the investigated slurries are neither purely elastic nor purely plastic in rheological behavior. On contrary to most model works a blurred supernatant-sediment interface makes difficulty in the gel point determination. During initial settling the high-phi(0) slurries clearly exhibit a finite yield stress to resist deformation. That is, the slurries are plastic fluids. However, the network structure in the slurries deteriorates gradually in the subsequent settling stage while the final, equilibrated sediment reveals a continuous distribution in solids fraction. Restated, the final sediment possesses as a purely elastic characteristic. The model parameters of theory by Buscall and White were regressed by the dynamic consolidating sediment data, while those by Tiller and Leu were obtained using the final equilibrated sediment data. Calculations from both models reveal that ball clay slurry is more compressible than is the kaolin slurry. The high-phi(S0) slurry would yield the less compressible sediment.
我们使用计算机轴向断层扫描仪（CATSCAN）研究了高岭土浆料和英国球粘土浆料在不同初始固体分数（phi(0)s）下的间歇沉降行为。对固结沉积物中固体分数的时空演变进行了连续监测。由于所研究浆料的沉积物与上清液之间的界面模糊，采用了平均程序来估计其零应力固体分数（phi(g)s）。除了高phi(0)浆料沉降相当缓慢外，无论phi(0)>phi(g)还是反之，基本沉降特性彼此相似。上述实验数据表明，所研究的浆料在流变行为上既不是纯弹性的也不是纯塑性的。与大多数模型工作相反，上清液 - 沉积物界面模糊使得凝胶点的确定变得困难。在初始沉降期间，高phi(0)浆料明显表现出有限的屈服应力以抵抗变形。也就是说，这些浆料是塑性流体。然而，浆料中的网络结构在随后的沉降阶段逐渐恶化，而最终达到平衡的沉积物在固体分数上呈现连续分布。换句话说，最终沉积物具有纯弹性特征。通过动态固结沉积物数据对Buscall和White理论的模型参数进行了回归，而Tiller和Leu的模型参数则使用最终平衡的沉积物数据获得。两个模型的计算结果表明，球粘土浆料比高岭土浆料更具可压缩性。高phi(S0)浆料产生的沉积物可压缩性较小。
