Completely segregated flow

For a first-order reaction in a CSTR, compare the predicted performance for completely segregated flow with that for nonsegregated flow. 

Fig. 10. Fractional conversion versus Damkohler number for half,-, first- and second-order reactions taking place in a single ideal CSTR. Shaded areas represent possible conversion ranges lying between perfectly micromixed flow (M) and completely segregated flow (S). Data taken from reference 32. A = R —...

In a reactor with a segregated fluid, mixing between particles of fluid does not occur until the fluid leaves the reactor. The reactor exit is, of course, the latest possible point that mixing can occur, and any effect of mixing is postponed until after all reaction has taken place. We can also think of completely segregated flow as being in a state of minimiun mixedness. We now want to consider the other extreme, that of maximum mixedness consistent with a given residence-time distribution. 

In the completely segregated flow we are assuming, the mean extent of the reaction will be... 

Completely segregated flow as a plug-flow reactor with... 

Figure 8.16 Alternate represeritation of completely segregated flow (A), maximum mixed flow(B), and an intermediate mixing pattern (C).

Figure 8.15 Completely segregated flow as a plug-flow reactor with side exits outlet flows adjusted to achieve given RTD.

Between these two extremes, there are various levels of micro-mixing in which mixing of fluid takes place within a mixture of segregated fluid elements and individual fluid molecules present in different proportions. A parameter X, which denotes the extent of micro-mixing, is assumed to vary between 0 (for completely segregated flow) and 1 (for complete micro-mixing). 

Calculate the conversion of a first-order reaction with rate constant k = 0.421 min carried out in Reactor I of Problem 3.15 assuming that the reactor is a completely segregated flow reactor. 

The conversion of a reactant in a completely segregated flow reactor is calculated using the equation... 

A total of 80% conversion is reported in an ideal CSTR with complete micro-mixing for a second-order reaction A- >B whose rate equation is (-r ) = ECa- What would be the conversion if completely segregated flow condition is assumed ... 

In the completely segregated flow case, both the fluid elements move through the incremental volume as two separate units without mixing with each other. Changes in fractional conversion of A AXi and AX in the two fluid elements are given by... 

Conversion of a First-Order Reaction in Ideal Reactors with Completely Segregated Flow... 

A. Ideal CSTR with completely segregated flow ... 

Consider a first-order reaction A—with kinetic rate expression (-/a) = 1cC carried out in an ideal CSTR with completely segregated flow (see Figure 3.73). 

An ideal CSTR with complete segregated flow. 

Consider an ideal PFR with completely segregated flow (Figure 3.74). x = v/cj is the space time, which is same as the mean residence time ... 

This implies that the conversion in an ideal PER with complete micro-mixing is the same as the conversion in an ideal PER with completely segregated flow for reactions of any order. Thus, the extent of micro-mixing has no effect on the conversion in an ideal PER for reactions of any order. 

---