The results of the simulation suggest that about three stirred tanks in series are equivalent to the RTD response eurve. Ĭomputer program PROGS 1 determines the number of tanks, the varianee, dispersion number, and the Peelet number from Hull and von Rosenberg data. The model consists of i -i- 1 stirred tanks in series, i of which have a common volume, and one of which has a smaller volume. N -> This indicates that the behavior of stirred tanks in series. The following derived equations are for a series of tliree stii+ed tanks (Figure 5-23) with eonstant volume Vr. For eonstant density, the exit eoneentration or eonversion ean he solved hy eonseeutively applying Equation 5-158 to eaeh reaetor. The exit stream from the first stirred tank serves as the feed to the seeond, the exit stream from the seeond reaetor serves as the feed to the third, and so on. This reduees the prohahility that a reaetant moleeule entering the reaetor will immediately find its way to the exiting produet stream. To reduee this bypassing effeet, a numher of stirred tanks in series is frequently used. In a single eontinuous flow stirred tank reaetor, a portion of the fresh feed eould exit immediately in the produet stream as soon as the reaetants enter the reaetor. Thus the general scaling equation for pressure drop in a single tube in laminar flow can be given in several equivalent forms. (4) so that only two are arbitrarily adjustable. They are for volume, S, radius Sr, and length, Sl.

This table includes three geometric scaleup factors. Factors for other forms of scaleup for incompressible fluids are given in Table 10.2. When scaling in parallel, the number of tubes scales directly with the inventory scaleup factor, S. This advantage is especially useful in polypropylene processes where the last reactor adds ethylene for impact modification.

The usual case is for two Ī major advantage of using tanks in series is the ability to have a different reaction environment in the various tanks. The series arrangement leads to higher conversion and thus eases the burden of downstream recovery and recycling. One advantage of using tanks in series is the improvement in residence time distribution from the exponential distribution of a single stirred tank toward that of piston (plug) flow. Modern fluidized-bed processes for polypropylene use two beds in series. Some polypropylene processes use two or three loop and stirred-tank reactors in series. Some polystyrene processes use five stirred-tank and stirred- tube reactors in series. Another way is to add a stirred tank in parallel, but better results and a more flexible process are usually achieved by adding a stirred tank in series. One way to double the output of a stirred tank process is to increase each linear dimension by 2 / = 1.26, but this may lead to heat transfer or mixing limitations. For the same LIG ratio, the relative crystallization times of k stages and one stage to reach the peaks are given by Eq. For two such the cumulative distribution is represented by Īs in the operation of chemical reactors, multistaging requires shorter residence time for the same performance. Nyvlt (1971) also develops equations for multistage crystalhzers in which nuclei form at the same rate in all stages.

Wilh generation of nuclei in die first stage only, the Equations were developed by Nyvlt (1971) for two main cases. Operation in several tanks in series will provide narrower size distributions.

Tanks in series infinite tanks