Unit operations in chemical engineering

Separation Efficiency. Similarly to other unit operations in chemical engineering, filtration is never complete. Some soflds may leave in the hquid stream, and some Hquid will be entrained with the separated soHds. As emphasis on the separation efficiency of soHds or Hquid varies with application, the two are usually measured separately. Separation of solids is measured by total or fractional recovery, ie, how much of the incoming solids is coUected by the filter. Separation of Hquid usually is measured in how much of it has been left in the filtration cake for a surface filter, ie, moisture content, or in the concentrated slurry for a filter-thickener, ie, solids concentration. 

McCabe, W. L. J. Smith and R Harriott. Unit Operations in Chemical Engineering, 5th ed. McGraw-Hill, New York (1993). 

The milling, grinding, and pulverizing of materials have always been one of unit operations in chemical engineering. They are well described in chemical engineering... 

Systematic engineering analysis of chemical processes led to the definition of a series of unit operations, such as distillation, absorption, and filtration, which are common to different chemical processes (e.g., see W. L. McCabe and J. C. Smith, Unit Operations in Chemical Engineering, 2nd ed., McGraw-Hill, New York, 1967). 

J. Nyvlt, Crystallization as a unit operation in chemical engineering, in Industrial Crystallization, 1969, pp. 1-23. 

McCabe, L.W., Smith, J.C., and Harriott, P. Unit operations in chemical engineering, 6th ed., McGraw-Hill, Singapore, 2001. 

McCabe, W.L. and Smith, J.C. 1976. Unit Operations in Chemical Engineering, Third Edition, McGraw-Hill Book Company, New York, NY, pp. 146, 610-613. 

In the foregoing discussion, the assumption is that each phase is transported in its own percolating network by a pressure-driven flow mechanism. This is the generally accepted view of multiphase flow in subsurface applications, and is certainly true at low values of the capillary number Ca = vfi/a). However, blob mobilization is a dominant form of transport in many unit operations in chemical engineering, where the capillary number and Reynolds number are higher. In these cases, specialized correlations for multiphase flow should be used. 

The methods of completely empirical experimentation and dimensional analysis are very important in engineering practice bnt exclnded from this snrvey as these methods are well known and described in most introdnctory textbooks on unit operations in chemical engineering. 

Melt crystallization, with all the mentioned advantages, has not found the place it deserves among the unit operations in chemical engineering today. Research efforts conducted by industry during the last few years, however, are a good beginning in the efforts to change this. 

Distillation is the main unit operation in chemical engineering for the separation and purification of liquids and vapors. 

It should be pointed out here that the scale-up procedure described here is specifically designed for separation or classification of fine particles. These are the particles predominantly used in the chemical industry and the approach, using dimensionless groups, is in common with the treatment of other unit operations in chemical engineering. The geometrical similarity concerns all internal dimensions of the individual cyclones except the size of the underflow orifice which is regarded here as an operational variable. 

Melt crystallization can have advantages and features that establish it as an alternative separation technique compared to other thermal unit operations in chemical engineering. 

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