Design problems detailed considerations

In the last analysis, a detailed consideration of these problems can be reduced to determination of the design of the reaction unit that will yield the maximum amount of end-product per unit of reactor volume. 

The other cause of constmction problems is the introduction of badly chosen, or even unauthorized, changes during constmction in order to expedite the work. Any changes in details, material specifications, or erection procedure must be given careful consideration by both the builder and silo designer. 

The analysis indicated that the conformance problems associated with the hub design had a cost of failure of more than 30%. This would represent at the annual production quantity required and target selling price, a loss to the business of several million pounds. As a result of the study the business had further detailed discussions with their suppliers and not surprisingly it turned out that the supplier would only be prepared to stand by its original quotation provided the tolerances on the hub, discussed above, were opened up considerably (more than 50%). Subsequently, this result supported the adoption of another more capable design scheme. 

Reference electrodes for non-aqueous solvents are always troublesome because the necessary salt bridge may add considerable errors by undefined junction potentials. Leakage of components of the reference compartment, water in particular, into the working electrode compartment is a further problem. Whenever electrochemical cells of very small dimensions have to be designed, the construction of a suitable reference electrode system may be very difficult. Thus, an ideal reference electrode would be a simple wire introduced into the test cell. The usefulness of redox modified electrodes as reference electrodes in this respect has been studied in some detail... 

Plants for the manufacture of fine chemicals are discussed in Chapter 7 with emphasis put on multiproduct plants. Types of production plants and typical equipment for multiproduct plants with cost considerations are presented in more detail. Problems of designing and scheduling multiproduct and multipurpose plants with particular emphasis given on process data needed to realise this task are discussed. 

As the flowsheet becomes more firmly defined, the detailed process and mechanical design of the equipment can progress. The control scheme must be added and detailed hazard and operability studies carried out. All this is beyond the scope of the present text. However, all these considerations might require the flowsheet to be readdressed if problems are uncovered. 

In spite of the drawbacks enumerated above, fluidized bed reactors have a number of compelling advantages, as we have noted previously. By proper design it is possible to overcome their deficiencies so that their advantages predominate. This book does not discuss in detail the manner in which this problem can be solved, although the design considerations outlined in subsequent sections of this chapter are quite pertinent. For detailed treatments of fluidized bed reactor design, consult the excellent reference works by Kunii and Levenspiel (3) and by Davidson and Harrison (4). 

The second problem is the identification of absorption bands, a problem that Prof. Adamson makes clear in the first page of his paper. In discussing transitions to the various d-d excited states in octahedral chromic complexes, he uses the usual octahedral designations. These designations serve to identify these bands loosely. But we must do considerably better than this. Thus, the second problem is certainly to identify the absorption bands in considerably more detail. 

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