Pilot-scale operation practical application

The effectiveness of a fixed-bed operation depends mainly on its hydraulic performance. Even if the physicochemical phenomena are well understood and their application in practice is simple, the operation will probably fail if the hydraulic behavior of the reactor is not adequate. One must be able to recognize the competitive effects of kinetics and fluid dynamics mixing, dead spaces, and bypasses that can completely alter the performance of the reactor when compared to the ideal presentation (Donati and Paludetto, 1997). The main factor of failure in liquid-phase operations is liquid maldistribution, which could be related to low liquid holdup in downflow operation, or other design problems. These effects could be critical not only in full-scale but also in pilot- or even in laboratory-scale reactors. 

Purification can be accomplished by varied means and there is no one best way to handle all situations. In projecting a new venture to operation on the industrial scale, one should be acquainted with established industrial practices. For this there is no need to describe each separate type of factory operation, inasmuch as many incorporate similar processing methods and a full recital would bog down in tedious repetition. Therefore the discussion here will be limited to a description of representative applications selected to illustrate different means for accomplishing diverse objectives. Included are processes in current industrial use together with items taken from pilot plant studies. Several discontinued applications are included because they contain potentially useful techniques not reported elsewhere. 

The problem of nonideal flow is directly related to scale-up. For example, there is no reason to pilot-plant if the reactor operates in an ideal mode. However, the magnitude or degree of (he nonideality of flow can significantly impact design and performance equations. This effect should not be ignored by the practicing engineer in some applications it is discussed in mote detail in a later section. 

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