Plug mixing

Models are useful for representing flow in real vessels, for scale up, and for diagnosing poor flow. We have different kinds of models depending on whether flow is close to plug, mixed, or somewhere in between. 

Scheme Q D, and E, From Fig. 12.1 the exit age distribution function for the two equal-size plug-mixed flow reactor system is...

Packed bubble columns 1-20 Plug Mixed Unlimited 0.5-0.7 1-4 10-30 1-12... 

Bubble cap plate columns 50-200 Plug Mixed Unlimited 0.7-0/7 1-4 10-40 1-16... 

Plate columns without downcomers 50-300 Plug Mixed Limited variation 0.5-0.5 1-4 10-20 1-8... 

Sieve plate in spray regime 100-300 Plug Mixed Unlimited — 1-3 5-20 0.5-6... 

Figure 3.1. F curves for plug, mixed, and arbitrary flow as obtained by imposing step input of dye of concentration C and measuring, as the output, the tune record of exit concentration as C/C . The two parameters characterizing the curve are T (mean residence time that for normalized curves is equal to 1) and u (axial dispersion).

Figure 3.2. a) C curves for plug, mixed, and arbitrary flows as obtained by imposing an idealized instantaneous input pulse of dye and measuring the time record of exit concentration as the output, (b) For arbitrary flow, a Gaussian-shaped curve is eventually achieved, which is characterized by the two parameters T(mean residence time), for which C = C ", and a (standard deviation equaling axial dispersion). 

With gas dispersed as bubbles in Bubble columns hquids 1-30 Plug Mixed Unlimited 0.6-0.8 1-4 2.5-100 0.25-40... 

Multiple reactions in parallel producing byproducts. Consider again the system of parallel reactions from Eqs. (2.16) and (2.17). A batch or plug-flow reactor maintains higher average concentrations of feed (Cfeed) than a continuous well-mixed reactor, in which the incoming feed is instantly diluted by the PRODUCT and... 

In general terms, if the reaction to the desired product has a higher order than the byproduct reaction, use a batch or plug-flow reactor. If the reaction to the desired product has a lower order than the byproduct reaction, use a continuous well-mixed reactor. 

The series byproduct reaction requires a plug-flow reactor. Thus, for the mixed parallel and series system above, if... 

But what is the correct choice a byproduct reaction calls for a continuous well-mixed reactor. On the other hand, the byproduct series reaction calls for a plug-flow reactor. It would seem that, given this situation, some level of mixing between a plug-flow and a continuous well-mixed reactor will give the best... 

A series combination of plug-flow and continuous well-mixed reactors (Fig. 2.3c and d)... 

Polymerization reactions. Polymers are characterized by the distribution of molecular w eight about the mean as well as by the mean itself. The breadth of this distribution depends on whether a batch or plug-flow reactor is used on the one hand or a continuous well-mixed reactor on the other. The breadth has an important influence on the mechanical and other properties of the polymer, and this is an important factor in the choice of reactor. 

Solution We wish to avoid as much as possible the production of di- and triethanolamine, which are formed by series reactions with respect to monoethanolamine. In a continuous well-mixed reactor, part of the monoethanolamine formed in the primary reaction could stay for extended periods, thus increasing its chances of being converted to di- and triethanolamine. The ideal batch or plug-flow arrangement is preferred, to carefully control the residence time in the reactor. 

The performance of fluidized-bed reactors is not approximated by either the well-stirred or plug-flow idealized models. The solid phase tends to be well-mixed, but the bubbles lead to the gas phase having a poorer performance than well mixed. Overall, the performance of a fluidized-bed reactor often lies somewhere between the well-stirred and plug-flow models. 

Continuous well-mixed reactors to plug-flow... 

The first distinction to be drawn, as far as heat transfer is concerned, is between the plug-flow and continuous well-mixed reactor. In the plug-flow reactor shown in Fig. 13.1, the heat transfer can take place over a range of temperatures. The shape of the profile depends on... 

VME bus. It is possible to plug other standard VME boards in the ET instrument. For example, it is possible to add a DSP board, and carry out on-line analysis. But there is also CPU time left to add signal processing on the eddy current board itself. (For example on-line mixing of signals at 2 different frequencies). 

The time-to-distance transfonnation requires fast mixing and a known flow profile, ideally a turbulent flow with a well-defined homogeneous composition perpendicular to the direction of flow ( plug-flow ), as indicated by tire shaded area in figure B2.5.1. More complicated profiles may require numerical transfomiations. 

Method 1. Mix 1 0 g. of 3 5-dinitrobenzoic acid (Section IV,168) with 4 ml. of thionyl chloride in a dry 50 ml. conical flask fit a reflux condenser, carrying a plug of cotton wool at the upper end, into the flask and heat on a water bath for 15-30 minutes. Remove the condenser and heat the flask in a boiling water bath FUME CUPBOARD 1) until the excess of thionyl chloride has evaporated. Use the resulting 3 5-dinitrobenzoyl chloride (about 10 g.) immediately. 

---