Product design single-material systems

Products consisting of only one material in a single system (non-composite) are easy and pure to re-use. With them, it is not generally necessary to separate the product structure prior to processing. This is why single-material systems are preferable when it comes to the design of products easy to recycle. Such systems, however, might meet their limits in cases where... 

Hydrothermal Synthesis Systems. Of the unit operations depicted in Figure 1, the pressurized sections from reactor inlet to pressure letdown ate key to hydrothermal process design. In consideration of scale-up of a hydrothermal process for high performance materials, several criteria must be considered. First, the mode of operation, which can be either continuous, semicontinuous, or batch, must be determined. Factors to consider ate the operating conditions, the manufacturing demand, the composition of the product mix (single or multiple products), the amount of waste that can be tolerated, and the materials of constmction requirements. Criteria for the selection of hydrothermal reactor design maybe summarized as... 

Figures 8.33 and 8.34 show the yield and conversion for the two cases ns a function of Qr. The conversion is not adversely affected by the poor mixing. In fact the conversion in the two-reactor system is higher than the single, well-mixed reactor. Notice, hotvever, that at low values of Qr, which corresponds to poor mixing at the feed location, the yield changes from more than 90% to less than 15%. Low yield is a qualitatively different problem than low conversion. If the conversion is low, we can design a separation system to remove the unreacted A and recycle it, or use it as feed in a second reactor. With low yield, however, the A has been irreversibly converted to an undesired product D, The raw material is lost and cannot be recovered, it is important to diagnose the low yield as a reactor mixing problem, and fix the problem at the reactor. A yield loss cannot be recovered by downstream processing.

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