Qualitative flowsheet

Qualitative flowsheets are given for the extraction and purification of all the rare metals discussed in earlier chapters. As far as possible the examples chosen are typical of current practice or of recently proposed processes. Each flowsheet presented begins with a mineral ore and ends with a pure metal, whereas in practice the various component operations are sometimes divided between two or more plants e.g. in the case of uranium, it is convenient to produce a concentrate containing about 70 per cent of the element near the minefield and to ship this to various refineries many thousands of miles away. Metal production may take place at the refinery, or in yet a third factory in association with subsequent metallurgical stages. 

Is reacting /-propanol with aluminum a better process than solid/liquid separation of n-heptane and / -propanol It is not possible to determine from the qualitative flowsheets developed here. Reacting /-propanol with aluminum has potential problems. The reaction to aluminum propoxide may not be sufficiently complete. The reactor may be expensive. In Chapters 3,4, and 5 we will take up methods to analyze designs for product purity and cost, for example. During the design phase, it is essential to generate different possibilities, which can be analyzed later. 

Included also in this chapter is a qualitative description of separations based on intraphase mass transfer (dialysis, permeation, electrodialysis, etc.) and discussions of the physical property criteria on which the choice of separation operations rests, the economic factors pertinent to equipment design, and an introduction to the synthesis of process flowsheets. 

Design a process to continuously produce prebaked pizza dough for a major grocery chain. Your flowsheet should have labels on all units and qualitative compositions of all streams. For each unit list key quantities such as temperature and residence time of material through the unit. 

Table 13.3 provides the control performance qualitatively for these five systems. As expected, the MeAc system (type I flowsheet) exhibits relatively poor control performance as can be seen early from qualitative argument or quantitative nonlinearity measures. The closed-loop behaviors of the EtAc and IPAc (type II flowsheet) systems are not quite as nonlinear as the steady-state measures predict. Relatively fast and symmetrical dynamics... 

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