Gravitational separation, process-stream

In any separation process, three streams are involved as shown in Fig. 7 for a filter with cake formation, a cross flow filter without cake formation, and a thickener or clarifier based upon gravitational sedimentation. The filter is assumed to have a fixed volume into which slurry is fed and cake is formed as filtrate flows through the filter medium. The fraction of filtrate or overflow, compared to the liquid in the slurry, is called the fractional recovery of liquid, which can be obtained based upon material balance. The fractional recovery for cake filter, cross-flow filter, and thicker or clarifier are as follows ... 

Mass transfer across interfaces is ubiquitous in industrial processes. For instance, it occurs in separation processes used in the field of biotechnology, in the extraction of metals from aqueous solutions, in the chemical and pharmaceutical industries and also in the treatment of effluents from the same plants. Ho vever, in the design of the contacting equipment the role of the interface and of interfacial phenomena are not taken into account. Take the example of the industrial effluent streams. These are usually not made up of pure components but are soups containing different chemicals and chemicals with surfactant properties. However, in the design of liquid-liquid contactors those streams are considered to be clean and interfacial phenomena (such as Marangoni and gravitational convection), which may exist, are not taken into account. 

In devices with cross parallel flow, there is a local unidirectional movement of streams, as a rule, to the subsequent centrifugal— gravitational separation. Speed limit of an easy phase in devices of this type makes 6-lOmps. They are expedient for using, for example, in processes with significant thermal effects (Karpenkov, 1970 and Vazovkin, 1972). 

Glassification. Classification (2,12,26,28) or elutriation processes separate particles by the differences in how they settle in a Hquid or moving gas stream. Classification can be used to eliminate fine or coarse particles, or to produce a narrow particle size distribution powder. Classification by sedimentation iavolves particle settling in a Hquid for a predetermined time to achieve the desired particle size and size distribution or cut. Below - 10 fim, where interparticle forces can be significant, gravitational-induced separation becomes inefficient, and cyclone and centrifugation techniques must be used. Classification also separates particles by density and shape. Raw material separation by differential sedimentation is commonly used in mineral processiag. 

There are a large number of processes in the chemical industries that handle a variety of suspensions of solid particles in liquids. The application of filtration techniques for the separation of these heterogeneous systems is sometimes very costly. If, however, the discrete phase of the suspension largely contains settleable particles, the separation can be effected by the operation of sedimentation. The process of sedimentation involves the removal of suspended solid particles from a liquid stream by gravitational settling. This unit operation is divided into thickening,... 

---