Energy Required and Scale-up

The first step is the evaluation of thermodynamic and kinetic data by quantitative energy calculations and qualitative considerations as discussed in Chapter 2. The results may provide a satisfactory answer as to whether the reaction can be performed in the open laboratory or requires a high-pressure cell arrangement on the small scale. Further evaluations are required for scale-up. Toxicity, corrosivity, type of apparatus, size, and other criteria must also be considered. 

Crystalhzation is important as an industrial process because of the number of materials that are and can be marketed in the form of crystals. Its wide use is probably due to the highly purified and attractive form of a chemical solid which can be obtained from relatively impure solutions in a single processing step. In terms of energy requirements, crystallization requires much less energy for separation than do distillation and other commonly used methods of purification. In addition, it can be performed at relatively low temperatures and on a scale which varies from a few grams up to thousands of tons per day. 

Whilst Izod tests are, perhaps surprisingly, generally reproducible it has been found impossible to scale up the results and thus predict the energy required to break a bar of large cross-section from results obtained with a bar of smaller cross-section. This has led to some uncertainty in the method of quoting results and the following approaches are used ... 

This had increased to 145 million lonnes by 1986 (Europe 44. USA/Canada 24%, Asia/Oceania 18% Africa 9%, Latin America 59c) Such sast quantities require huge planis. lliese frequently have a capacity in excess of 2(KK) tonnes per day in the USA bui arc more commonly in the range 300-750 tonnes pei day in Europe and smaller still in less induslriah/ed couniries. Even so, ihe energy flows are enormous as can be appreciated by scaling up the following reactions... 

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