Bypass effect

Find the correction factor for bundle-bypassing effects Jb from Fig. 11-12... 

The amount of catalyst required in (a) is even greater than that required for a CSTR, which may be accounted for by the bypassing effect (Section 23.1.3). 

In a single continuous flow stirred tank reactor, a portion of the fresh feed could exit immediately in the product stream as soon as the reactants enter the reactor. To reduce this bypassing effect, a number of stirred tanks in series is frequently used. This reduces the probability that a reactant molecule entering the reactor will immediately find its way to the exiting product stream. The exit stream from the first stirred tank serves as the feed to the second, the exit stream from the second reactor serves as the feed to the third, and so on. For constant density, the exit concentration or conversion can be solved by consecutively applying Equation 5-158 to each reactor. The following derived equations are for a series of three stirred tanks (Figure 5-23) with constant volume VR. 

Since gases have much higher mobility than crude oil or water, the injected gas has a strong tendency to channel through the reservoir and bypass the reservoir oil. This bypassing effect decreases, significantly, the efficiency of the recovery process and, in some cases, even makes any gas injection unprofitable. 

Another problem associated with the formation of aggregates of hairy roots is that entrapped bubbles of gas can coalesce to form large babbles that lead to channeling and bypassing effects that adversely affect mass transfer of O2 to the roots. (Rise velocities of large bubbles are greater than those of small dispersed bubbles.)... 

The residence time distribution of the gas may deviate from plug-flow operation by dispersion and bypassing effects. (We will learn in the Section 4.10.3 why plug-flow operation is mostly advantageous compared to mixed flow.)... 

Subsequent serially linked serpentine— This flow field also divides the flow field into segments in an attempt to avoid the long straight channels and relatively large pressure differentials between the adjacent sections, thus minimizing the bypassing effect [13. ... 

Figure 7.17a and b illustrate the dynamic profiles of sulfur concentration and temperature of industrial HDT reactor, which were determined from mass and energy balance equations. The results of the transient simulation of sulfur profiles of bench-scale reactor and experimental temperature are also shown for comparison. It can be observed that the steady state was reached at the same time (1700 s), which is due to the same space velocity and initial temperature used in both reactors. Because a single point at steady state is used to validate the dynamic model, some uncertainness remains regarding the shape of dynamic profiles of bench-scale and industrial reactors. According to Carberry and Varma (1987), the small peak in the sulfur concentration profile at the outlet of the commercial reactor is a typical response from HDT reactors that perform well with a weak bypass effect. 

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