Multiple-Vessel Configurations

Some multiple-vessel configurations and consequences for design and performance are discussed previously in Section 14.4 (CSTRs in series) and in Section 15.4 (PFRs in series and in parallel). Here, we consider some additional configurations, and the residence-time distribution (RTD) for multiple-vessel configurations. 

---

We focus attention in this chapter on simple, isothermal reacting systems, and on the four types BR, CSTR, PFR, and LFR for single-vessel comparisons, and on CSTR and PFR models for multiple-vessel configurations in flow systems. We use residence-time-distribution (RTD) analysis in some of the multiple-vessel situations, to illustrate some aspects of both performance and mixing. 

For smaller boiler plants, various sieves, screens, cyclones, and strainers may sometimes be used for filtering MU and FW. Also, bag, ceramic membrane, cartridge, and candle filters, either with a filter aid (precoat filters) or without (naked filters), all of which are typically available in single- and multiple-filter component vessel configurations. 

Multiple parallel vessel configurations also possible. 

Port Selector Valve. The inside of the Model 50 Extractor oven was originally equipped with a VALCO 4-port selector valve (Model No. E04). This valve is important in operations regularly utilizing additional co-solvents, inerts or vacuum, as in the introduction of modifiers in our case. When the valve is mounted in its normal fashion, one inlet port controls the flow to four outlet ports which are user selected by position number. When the valve is mounted in a reverse fashion, four inlet ports control the flow to one outlet port. In this manner, the inlet ports can be used to independently deliver various solvents. This reverse configuration is used in our system design. With this configuration, multiple fluids can be introduced to the extraction vessels with ease. 

The model 496 Multiple Organic Synthesizer (Figure 13.7) has two robotic arms to deliver reagents and solvents to the Teflon reaction block. Standard monomer racks accommodate 10, 36, or 128 vessels (custom configurations are easy to adapt). The reagents in the racks are kept under an inert atmosphere. To pick up a reagent, the robotic arms pierce the septum at the top of the rack. In addition, six 100-mL reservoirs are available to store common reagents. 

Note that Eq. 6.1.25 provides only an estimate on the range of the value of HTN. We select a specific value after examining the reactor performance for different values of HTN. It is important to examine the reactor design for different values of HTN, since, when multiple reactions occur, it is difficult to predict the effect of the heat transfer on the relative rates of the individual reactions. Once the physical reactor vessel has been designed, it is necessary to verify that its configuration (S/V) and the agitation conditions actually provide the desired value of HTN. 

---