Particles mixed sizes

For granular solids of mixed sizes the average particle diameter may be calculated as... 

AN particle shape, size distribution and density have a significant effect on the mixing and loading characteristics of molten Minol II. The product made with grained AN was best with respect to ease of mixing, smooth consistency, uniform viscosity, pourability and cast density (Ref 48)... 

Mixing together of particulate solids, sometimes referred to as blending, is a very complex process in that it is very dependent, not only on the character of the particles — density, size, size distribution, shape and surface properties — but also on the differences of these... 

Several mathematical models are available for predicting the dissolution of particles of mixed size. Some are more complex than others and require lengthy calculations. The size of polydisperse drug particles can be represented with a distribution function. During the milling of solids, the distribution of particle sizes most often results in a log-normal distribution. A log-normal distribution is positively skewed such that there can exist a significant tail on the distribution, hence a number of large particles. The basic equation commonly used to describe the particle distribution is the log-normal function,... 

For beds composed of spheres of mixed sizes the porosity of the packing can change very rapidly if the smaller spheres are able to fill the pores between the larger ones. Thus Coulson 15) found that, with a mixture of spheres of size ratio 2 1, a bed behaves much in accordance with equation 4.19 but, if the size ratio is 5 1 and the smaller particles form less than 30 per cent by volume of the larger ones, then K" falls very rapidly, emphasising that only for uniform sized particles can bed behaviour be predicted with confidence. 

For relatively coarse particles, the rates of fall of the interface between (a) and (b) and between (b) and (c) can be calculated approximately if the relation between sedimentation velocity and voidage, or concentration, is given by equation 5.76. Richardson and Shabi 65) have shown that, in a suspension of particles of mixed sizes, it is the total concentration which controls the sedimentation rate of each species. 

Uf and Cf are determined by solving equations 5.115 and 5.116 simultaneously. Further study has been carried out of the behaviour of particles of mixed sizes by several groups of workers including Selim, Kothari and Turian171 . 

The behaviour of particles of mixed sizes and of mixed densities is highly complex and it has been the subject of many investigations. The works of Chen and Keairns(77) of Hoffman, Janssen and Prins(78) and of Wu and IJaeyens179-1 indicate the current state of knowledge in this area. 

In fluidisation with a liquid, a bed of particles of mixed sizes will become sharply stratified with the small particles on top and the large ones at the bottom. The pressure drop is that which would be expected for each of the layers in series. If the size range is small however, no appreciable segregation will occur. 

When a bed is composed of granular material with particles of mixed sizes, the suction potential cannot be calculated and it must be measured by methods such as those given... 

Solutions are homogeneous mixtures that contain particles the size of a typical ion or small molecule. Any one state of matter can mix with any other state, leading to seven possible kinds of solutions. For solutions in which a gas or solid is dissolved in a liquid, the dissolved substance is called the solute and the liquid is called the solvent. 

---